JP2019030623A - Beamforming method, measurement imaging device, and communication device - Google Patents

Abstract

To provide a device which can perform beamforming at high speed and with high accuracy without performing approximation calculation.SOLUTION: A beamforming method includes: a step for receiving wave motions arriving from an object to be measured at at least one reception opening element 20a and generating a reception signal; a step for generating a multi-dimensional reception signal by performing beamforming and lateral direction modulation with respect to the reception signal generated at the step; and a step for performing Hilbert transformation processing with respect to the multi-dimensional reception signal generated at the step. The Hilbert transformation processing step performs partial differential processing or first-dimensional Fourier transformation in an axial direction or lateral direction, generates analytical signals of the respective multi-dimensional reception signals of two wave motions in the case of two-dimension and, in the case of three-dimension, generates analytical signals of the respective multi-dimensional reception signals of three or four wave motions.SELECTED DRAWING: Figure 2

Description

  The present invention relates to a beam forming method for performing beam forming using an arbitrary wave coming from a measurement target. Furthermore, the present invention relates to a measurement imaging apparatus and a communication apparatus that use such a beamforming method.

  In particular, the present invention captures an image of a measurement object based on an electromagnetic wave, light, dynamic vibration, sound wave, or arbitrary wave such as a heat wave coming from the measurement object, or temperature or displacement in the measurement object. The present invention relates to a digital beam forming method in an imaging apparatus for nondestructively measuring the physical quantity, composition, structure, or the like. There are various measurement objects such as organic substances, inorganic substances, solids, liquids, gases, objects that follow rheology, living creatures, astronomical objects, the earth, and the environment, and the application range is extremely wide.

  The present invention can be applied to nondestructive inspection, diagnosis, resource exploration, material and structure generation and manufacturing, various physical and chemical repairs and treatment monitoring, clarified functions and physical properties, etc. Relatedly, in such cases, accuracy may be required under conditions that are not invasive, minimally invasive, noninvasive, and the like, without causing great disturbance to the measurement target. Ideally, the measurement object should be observed in situ in situ.

  In addition, treatment or repair may be performed on the measurement target by the action of the wave itself, and the situation may be observed by performing beam forming on the response from the measurement target at that time. Also, beam forming is performed in satellite communication, radar, sonar, etc. to realize an informationally safe environment under energy saving, and accurate communication is performed. Beam forming has also been applied to ad hoc communication devices and mobile communications. When the measurement target is dynamic, real-time characteristics are required, and beam forming is required to be completed in a short time.

  In a wave such as an electromagnetic wave, light, dynamic vibration, sound wave, or heat wave, the behavior as a wave varies depending on the frequency, bandwidth, intensity, or mode. Many types of transducers of various types of waves have been developed so far, and imaging using transmitted waves, reflected waves, refracted waves, scattered waves (forward scattered waves, back scattered waves, etc.) of these waves has been performed.

  For example, it is well known that ultrasonic waves having a high frequency among sound waves are used in non-destructive inspection, medical care, and sonar. Also in the radar, electromagnetic waves (radio waves, FM waves, microwaves, terahertz waves, infrared rays, visible light, ultraviolet rays, radiation such as X-rays, etc.) having an appropriate frequency according to the measurement object are used. The same applies to other waves, and each wave behaves differently depending on the frequency.Therefore, different sensing and communication are performed according to the measurement object, medium, and frequency band. , Polarization can also be used).

  In those applications, a beam forming process is often performed by mechanically scanning a measurement target with a transducer, using the same transducer multiple times, or using a plurality of transducers arranged in advance in an array. . It is well known that aperture surface synthesis processing is performed when observing the earth, land, ocean, and weather with satellite or airplane radar. Beam forming is often aimed at obtaining a high spatial resolution and a high contrast in a region of interest or a point of interest by providing appropriate directivity particularly when imaging a measurement target.

  As a result, by acting on the wave generated from the measurement object, reflection and transmission, various scattering (Rayleigh scattering, Mie scattering, etc.), attenuation, or frequency dispersion due to spatial changes in impedance are observed. It is possible to observe the structure and composition of the inside and surface of the measurement object based on what the measurement object is. The measurement object may be observed with various spatial resolutions. It can be characterized at the level of structure or composition (eg, individual level, molecular level, atomic level, nuclear level, etc.).

  For the purpose of high-accuracy high-resolution imaging, signal compression techniques have been used for a long time, and chirp wave techniques and coding compression techniques have been used as representative ones. In some cases, such as ISAR (Inverse Synthetic Aperture Radar), the observed wave is subjected to inversion of the beam characteristics to perform super-resolution (not always during aperture synthesis). ), And may actively reduce resolution. Among them, singular value decomposition, regularization, Wiener filter, etc. are effective.

  In addition, the encoding technique is also used when a plurality of signals are separated, for example, when a received signal is separated into received signals corresponding to transmission signals having different transmission positions. Waves coming from different directions may be separated, and signal sources may be identified and separated. In such a case, the place which relies on the matched filter with high signal detection ability is great. However, while it is possible to acquire signal energy, when obtaining the movement, displacement, distortion, etc. of the measurement object accompanied by deformation, the spatial resolution is lowered, and the measurement accuracy is lowered. In separating waves and signals, it is also useful to use frequencies, bands, or multidimensional spectra.

  In the imaging using the above-described wave, the distribution of amplitude data obtained through orthogonal detection, envelope detection, or square detection is usually displayed as a gray image or a color image in one, two, or three dimensions. Often resulting in a morphological image. Functional observation is also possible. For example, in Doppler measurement using these waves, raw coherent signals are processed (ultrasonic Doppler, radar Doppler, laser Doppler, etc.).

  In addition, for example, in the field of medical ultrasound, there is a useful technique that can detect a moving tissue although there is no information on the displacement direction, as in power Doppler. In addition, when microwaves, terahertz waves, or far infrared rays are used, the temperature distribution of the measurement target can be observed. These measured physical quantities may be displayed superimposed on the morphological image. In the field of image measurement, it is well known that motion is observed using a signal made incoherent through detection (cross-correlation processing, optical flow, etc.). In medical ultrasound and sonar, imaging using physically generated harmonics, chords, and difference tones is also performed. In particular, when the measurement target is dynamic, real-time characteristics are required for the beam forming process.

  In satellite communications, radar, sonar, etc., beam forming is performed to realize an informationally safe environment under energy saving, and accurate communication is performed. Beam forming has also been applied to ad hoc communication devices and mobile communications. It is also effective for communication with a specific person, a specific signal generation source, and a specific position. In communication, information may be transmitted from a transmitter to a receiver on a wave, and the purpose may be achieved by itself, or the receiver may return the result of the communication to the transmitter, Of course, there is a case of responding to the request, but of course the example of communication is not limited to this. Real-time characteristics are required when the content of information is dynamic depending on the communication target and observation target, and beam forming in that case is required to be completed in a short time.

  Under such circumstances, the inventor of the present application has developed an ultrasonic imaging technique for differentially diagnosing lesions such as cancer lesions and sclerosis in human tissues. The inventor of the present application has made high resolution and high efficiency of HIFU (High Intensity Focus Ultrasound) treatment along with high resolution of echo imaging and high precision measurement imaging of tissue displacement, They also perform imaging based on the reception of echoes during intense ultrasound radiation. Such imaging is based on performing high-speed and appropriate beam forming, and high-speed and appropriate detection methods, tissue displacement measurement methods, shear wave propagation measurement methods, and the like have been reported in the past.

  More than 20 years have passed since the medical ultrasonic diagnostic imaging apparatus was digitized. In older cases, a device that performs mechanical scanning using a single aperture conversion element and then performs electronic scanning using a plurality of conversion elements and an array type device composed of them is an analog device. To digital equipment. In fact, the classic aperture synthesis process itself was digital beamforming from the time it was used in radar mounted on satellites and airplanes, but the received signal strength was weak. For that reason, it was rarely used in medical ultrasound.

  On the other hand, the inventor of the present application recently invented a multidirectional aperture plane synthesis method and invented beamforming in multiple directions from received echo data for aperture plane synthesis. As a result, it is possible to obtain a multi-directional steering (deflection) image signal at the same frame rate as that of a normal electronic scan, and by performing coherent addition thereof, lateral modulation imaging (depth direction and It has a horizontal carrier frequency orthogonal to this, and has a higher spatial resolution than normal imaging. Furthermore, by using together the multidimensional autocorrelation method invented by the inventor of the present application, the displacement vector distribution can be measured in real time. In addition, when incoherent addition is performed, it is also possible to reduce speckles (normally, transmission beams are generated in different directions to reduce speckles, but according to the multidirectional aperture synthesis method, High frame rate). Outside the field of ultrasound, digitization is progressing in sensing devices that use radiation such as microwaves, terahertz waves, X-rays, other electromagnetic waves, vibration waves including sound, and heat waves for nondestructive inspection. It has been.

  For example, aperture synthesis in these sensing devices is active beamforming, and the waves to be processed are transmitted waves, reflected waves, refracted waves, or scattered waves (forward) of those waves generated by the transducer. Scattered waves or backscattered waves). On the other hand, in passive beamforming, for example, the temperature distribution measurement based on the above-mentioned microwave observation and the case of observing the electrical activity source due to the brain magnetic field of living creatures are self-divergent. A transmitted wave, a reflected wave, a refracted wave, or a scattered wave (a forward scattered wave, a back scattered wave, or the like) based on a wave emitted from a (self-emanating) signal source is a target. There are many other examples that correspond to these, but as an example different from them, recently, we have called living organisms as measurement objects, called photoacoustics, irradiating measurement objects with lasers, and frequency-dependent A volume change is caused by a certain heat absorption, an ultrasonic wave is generated using this as a sound source, and peripheral blood vessels are differentiated as a result of beam forming.

  A digital device requires more processing time than an analog device, but its computational processing capability has been greatly improved, and it has been downsized, including data storage media, has become inexpensive, and higher-order calculation processing There are many advantages such as being easy to apply and having a high degree of freedom. In fact, even in digital devices, high-speed analog processing after receiving a signal by a sensor is extremely important in sensing devices, and AD conversion (analogue-to-digital conversion) is relatively close. It can be appropriately realized in combination with the digital processing after.

  In an analog device, transmission and reception beamforming are performed by analog processing. On the other hand, in a digital apparatus, transmission beam forming is performed by analog processing or digital processing, and reception beam forming is performed by digital processing. Therefore, in the present application, the digital beamformer means that the reception beamforming is always performed by digital processing.

  After receiving a wave from a measurement object through a plurality of transducer elements, an array type device composed of them, or mechanical scanning of one or more transducer elements, DAS (Delay and Summation) is a so-called aperture plane synthesis process. Addition) processing is performed. In transmission, transmission beam forming may be performed by driving a plurality of elements, and classical aperture synthesis based on single element transmission may be performed. However, in reception beam forming, , DAS processing is performed.

  That is, transmission beam forming is performed by analog processing or digital processing. On the other hand, in receive beamforming, a received signal is generated by receiving a wave by each element in the array or at a different position, and the analog received signal is output after level adjustment or analog filtering by analog amplification or attenuation. A / D conversion into a digital reception signal is performed, and the digital reception signal is stored in a memory. After that, devices and computers with general-purpose computing power, PLD (Programmable Logic Device), FPGA (Field-Programmable Gate Array), DSP (Digital Signal Processor), Digital processing is performed on the stored received signal using a GPU (Graphical Processing Unit), a microprocessor, or a dedicated computer, a dedicated digital circuit, or a dedicated device. The

  Devices that perform these digital processes may include analog devices, AD converters, memories, and the like. Devices and computers with computing power may be multi-core. As a result, at the time of reception, dynamic focusing, which is almost impossible with an analog device, can be easily performed. Parallel processing is also performed. In order to increase the speed of analog processing and digital processing, a transmission line (for example, a stacked circuit) and a broadband wireless path are important.

  Dynamic focusing improves the spatial resolution in the range direction of the generated image signal and the depth direction (depth direction) of the measurement target. On the other hand, the dynamic focusing of transmission is possible only in the case of classic aperture synthesis by single-element transmission. In order to secure the energy of the transmission wave, transmission beam forming at a fixed focal position by multiple element driving is often performed instead of aperture plane synthesis by single element transmission.

  The inventor of the present application invented high-frame-rate echo imaging that transmits a wave whose plane of a plane wave or the like spreads widely in the lateral direction and interrogate a wide range in one transmission. In addition, the inventor of the present application coherently adds (superimposes) a plurality of waves of this type having different steering (deflection) angles to perform lateral modulation and lateral wideband (higher lateral resolution). In particular, when the above-described multidimensional autocorrelation method is realized, blood flow in the carotid artery where shear wave propagation or blood flow is fast, or blood flow in the heart chamber with complicated flow, etc. Was measured as a multi-dimensional displacement vector. The same applies when multidirectional aperture synthesis is performed and when transmission beamforming is performed. In addition, a plurality of waves having different carrier frequencies may be generated and overlapped to realize a wide band in the axial direction (high resolution in the axial direction).

  Such processing is performed in the case of active beam forming, but a transmitter is not used in passive beam forming. In this way, a digital beamformer usually consists of a transmitter (in the case of active beamforming), a receiver, and a DAS processing device, and is realized by assembling these devices. Small packages are now available at low cost.

  This DAS process uses a phase delay process that multiplies a complex exponential function in the frequency domain, which requires a huge amount of time but delays the received signal at high speed by interpolating approximation processing in the spatial domain for phasing. There is one that delays with high accuracy based on the Nyquist theorem (the past invention of the inventor of the present application), and the received signals are added in the spatial domain after phasing (phasing addition). In a digital device, as a trigger signal for digital sampling (AD conversion) of an analog reception signal, for example, a command signal generated by a control unit may be used so that a transmitter generates a transmission signal to an element to be driven. .

  In addition, when driving a plurality of elements with transmission delay in one beamforming, an analog or digital transmission delay is mounted in advance on the transmission unit to realize the transmission focus position, steering direction, etc. that can be selected by the operator. Patterns may be used. Furthermore, in the reception digital processing, the command signal for the element to be driven first, the command signal for the element to be driven last, or the command signal for driving another element is used as a trigger signal. Sampling may be started and a digital delay may be applied. These command signals may be generated based on a command signal for starting beam forming for one frame.

  When the digital delay is performed in the transmission delay, unlike the analog delay, an error determined by the clock frequency for generating the digital control signal is inevitably generated. Therefore, the analog delay is better for the transmission delay. In addition, if a digital delay is applied in reception to realize reception dynamic focusing, an error is caused by the above-described interpolation approximation processing. Therefore, the sampling frequency of the AD converter is increased sufficiently at a cost, or the above-described high There was no choice but to apply low-speed beam forming by applying an accurate digital delay (phase rotation processing).

  In the case of the former with interpolation approximation processing, the phasing addition may simply add echo signals from the position including the coordinate position of the signal value to be generated, bi-linear or multi-dimensional polynomial The accuracy may be improved by interpolation using the above. The former is much faster than the latter, which uses a complex exponential function, but the accuracy is low. The latter is highly accurate but extremely slow. This phasing addition is often performed under the assumption that the wave propagation velocity is known or assumed to be constant within the region of interest. On the other hand, the propagation velocity is measured and phase aberration correction is performed. Before or after beamforming, for example, the cross-correlation function between adjacent beam signals or between beam signals at different angles is evaluated to evaluate the phase. Aberration can be determined (if the propagation velocity is uniform, it becomes an interferometry).

  Compared to the case where the aperture elements are distributed or arrayed in a one-dimensional space, the aperture elements are distributed in two dimensions or three dimensions, or the aperture elements constitute a two-dimensional or three-dimensional array. In some cases, it is necessary to perform more processing for beam forming, and a large number of processors are installed to perform parallel processing. In some cases, parallel reception processing is performed for beam forming at a remote position with little interference, transmission beam forming in a plurality of directions with different steering angles, and single transmission beam forming.

  In terms of communication control, it is necessary for waves to be generated appropriately, reflecting the type and amount of communication data, or the characteristics of the medium, and optimized under these observations. It is desirable that communication be performed. It is also possible to separate the interfering waves using analog devices or by analog or digital signal processing. Controlled waves of propagation direction, coding, frequency and / or bandwidth are important.

  As another invention of the inventor of the present application similar to the above-described multidirectional aperture plane synthesis processing, it is possible to perform multidirectional reception beamforming with respect to one transmission beamforming and improve the frame rate. In addition, apodization may be important in beam forming. For example, each of transmission and reception apodization may be performed to reduce side lobes, but this has a trade-off relationship with lateral resolution and should be appropriately performed. On the other hand, a simple beam former that does not perform apodization is often used with an emphasis on spatial resolution. However, the inventor of the present application reports that appropriate apodization is necessary to obtain lateral resolution while suppressing side lobes during steering. Further, in the past inventions of the inventors of the present application, there are those that remove side lobes in the frequency domain.

  In addition, contrast agents (for example, microbubbles in medical ultrasound imaging) may be used in order to apply the nonlinear characteristics of waves in the subject. Irradiates waves with high intensity and high harmonic waves (broadband transmission), and performs non-linear processing on received coherent signals and coherent signals after phasing addition. Invented high contrast imaging by suppressing lobes. The inventor of the present application also invented highly accurate tissue displacement (vector) measurement based on the nonlinear processing.

  It is also possible to generate an imaging signal using a virtual source. As for the virtual source, there have been reports in the past that the virtual source is installed before the physical aperture and that the virtual source is installed at the transmission focal position. Furthermore, the inventor of the present application can install not only a virtual source but also a detector at an arbitrary position without using a focal point, an arbitrary physical source or detector of a wave, and an arbitrary scatterer or diffraction grating. We report that we can install in position. It is possible to increase the spatial resolution and widen the field of vision (FOV).

  As the imaging form, orthogonal detection, envelope detection, or square detection is used, but the inventors of the present application are also actively displaying the wave itself as a color image or a gray image, and phase information Emphasis on display including As described above, development of multi-dimensional devices using various waves is under progress for various purposes.

  There are some digital beam forming using fast Fourier transform disclosed so far, and one of them is analog processing (Fourier transform is an analytical solution of classical monostatic aperture synthesis ( Digitize (see Non-Patent Document 1), and exactly perform classical aperture synthesis at high speed and high accuracy through Fast Fourier Transform (see Non-Patent Document 2). In this process, interpolation approximation is not required, but in the case of steering (deflection) or multi-static aperture synthesis (generally, reception using the element or a plurality of peripheral elements in one-element transmission) Digital processing is not disclosed.

  All other digital beam forming disclosed requires interpolation approximation processing and has low accuracy. For example, a method of performing wave number matching through fast Fourier transform including the case of steering in plane wave transmission is disclosed (see Non-Patent Document 3-5), but in this case, the aperture shape of the array is not flat. In some cases, when calculating or displaying an image (when the array opening is an arc (see Non-Patent Document 6)), an interpolation approximation process is required, and the accuracy is low. Although the thing using the fast Fourier transform at the time of plane wave transmission is disclosed also in patent documents 1-4, all perform wave number matching through interpolation approximation. By performing wave number matching by the interpolation approximation, the multi-dimensional spectrum is obtained with the angular vector wave vector coordinate system at equal intervals, and fast inverse Fourier transform is performed, so that beam forming can be completed at high speed.

  Recent Non-Patent Document 5 discloses that wave number matching is Fourier-transformed with respect to non-uniform sampling signals, but this is also based on interpolation approximation processing. As mentioned above, digital beam forming has a long history, but when the most important is the real-time performance (calculation speed) until the image is displayed, interpolation approximation is often performed, providing the best accuracy. I don't mean. In addition, the most general fixed focus processing known to perform DAS processing, steering at that time, and the like are not disclosed even by a processing method performed through digital fast Fourier transform.

  There is also a report on the migration method (see, for example, Non-Patent Document 7), which also requires interpolation approximation in wave number matching. In order to obtain accuracy in processing involving these interpolation approximations, it is usually necessary to perform oversampling sufficiently by increasing the sampling frequency of the AD converter.

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  As described above, if a digital delay is applied in reception to realize reception dynamic focusing, an error is generated according to the above-described interpolation approximation processing. Therefore, the sampling frequency of the AD converter is sufficiently increased at a high cost. Alternatively, the above-described high-precision digital delay (phase rotation processing) was applied to achieve low-speed beam forming.

  Up to now, reflected waves, transmitted waves, scattered waves (forward) are targeted for vibration waves (mechanical waves) including electromagnetic waves, sound waves (compression waves), shear waves, surface waves, etc., or heat waves. Scattered or backscattered waves, etc.), refracted waves, surface waves, shock waves, or methods of digital beamforming for those waves generated from self-emanating wave sources are disclosed. As described above, the present invention is limited to monostatic type aperture surface synthesis that does not include steering, plane wave transmission that includes steering, and the migration method. Other than the monostatic aperture plane synthesis, digital beam forming could not be performed without requiring interpolation approximation. Therefore, the accuracy was low.

  On the other hand, when using a transmission or reception transducer array device having an arbitrary aperture shape (sometimes used for both transmission and reception, or transmission and reception may be related to different waves) or passive When only receiving transducers are used in beam forming, no interpolation approximation is required, regardless of whether transmission or reception focusing or steering is used, even if the coordinate system of the transmitted and received beams is different from the coordinate system for image display. In addition, it is desired to perform arbitrary beam forming at high speed and with high accuracy.

  In the case of active beamforming, transmit and receive transducer array devices with arbitrary aperture shapes (transducers may be used for both transmit and receive) are used. In the case of passive beamforming, only a receiving transducer array device having an arbitrary aperture shape is used. In those cases, it is desired to realize arbitrary beam forming at high speed and with high accuracy by digital processing. It is desired that virtually any focusing and any steering (deflection) be performed using a transducer array device having an arbitrary aperture shape.

  After beam forming with phasing addition, linear or non-linear signal processing is performed on a plurality of beams in which at least one of wave parameters such as frequency, bandwidth, pulse shape, beam shape in each direction is different, A beam having a different value for at least one of those wave parameters may be generated (frequency modulation, wide band, multi-focus, etc.). In such beam forming, focusing is performed. Steering (deflection) and apodization are performed using a transducer array device having an arbitrary aperture shape based on DAS processing. Further, as described later, a beam having a different value for at least one of the wave parameters may be generated and utilized due to a linear or nonlinear phenomenon in the medium.

  The wave propagation speed is determined by the physical properties of the medium under physical conditions. Therefore, when the aperture element forms a two-dimensional or three-dimensional distribution or a multidimensional array to perform imaging in a multidimensional space, it is a one-dimensional case. Compared to, a lot of beam forming will be performed, and the number of processing data used for one beam forming will increase, so it will take a lot of time, but acquiring the high speed of beam forming, It is desirable to use a device that processes these beam formings in a so-called real time or a device that can display the results in a short time.

  Up to now, digital beam forming through Fourier transform has been disclosed through interpolation approximation in a Cartesian coordinate system mainly using a one-dimensional or two-dimensional linear array transducer. Even when the coordinate system between the reception and the result (image) display is different, it is desirable to perform digital beam forming without performing any interpolation approximation.

  A method disclosed for a case where the aperture shape of the array is not flat (for example, when the array aperture is an arc) also performs interpolation approximation. As a typical example, when a convex transducer is used, or when electronic or mechanical sector scan or IVUS (intravascular ultrasound) scan is performed, transmission and reception are performed in an arbitrary coordinate system such as a polar coordinate system. It is desired to obtain a signal that is directly beamformed in an arbitrary image display system (arbitrary coordinate system) such as a Cartesian coordinate system without processing the digital signal obtained from the wave and performing interpolation approximation.

  In recent years, memory and AD converters have become very inexpensive, but without oversampling, sampling waves based on the Nyquist theorem, it takes time to perform DAS processing that does not require interpolation approximation. It is desired that the corresponding beam forming can be performed at high speed. Proper implementation of apodization can also be important.

  As a result of solving these problems, the spatial resolution and contrast (including the effect of suppressing side lobes) of the image signal obtained in real time or in a short time are high, and the motion (displacement) of the object is obtained from the obtained signal. ), Deformation, or temperature, etc., it is desired to realize highly accurate measurement. For example, in the field of medical ultrasound, in recent years, the Doppler method has been applied to echo signals to measure tissue displacement and speed, and then subjected to spatiotemporal differentiation to obtain acceleration and strain, etc. became. Spatio-temporal differentiation is a process that amplifies high-frequency measurement errors and degrades the signal-to-noise ratio (SN ratio), so it is necessary to realize highly accurate displacement measurement using phase. High-accuracy beam forming that realizes this is dynamic focusing based on so-called DAS processing. A three-dimensional imaging apparatus using a two-dimensional array or a three-dimensional array also tends to become widespread. In this way, it is desired to achieve arbitrary beam forming including dynamic focusing at high speed and with high accuracy without interpolation approximation.

  The inventor of the present application has recently developed a highly accurate measurement method for tissue displacement and shear wave propagation that moves relatively quickly, based on high-speed beam forming by deflection plane wave transmission (transmission and reception within the region of interest is fast). Although realized, it is desirable to perform beam forming with high accuracy at high speed without requiring interpolation approximation even when such focusing is not performed. By performing high-speed beam forming while changing the steering angle and performing coherent addition, it is possible to obtain almost the same high image quality (spatial resolution and contrast) at high speed compared to scanning using a normal focusing beam. . High-speed beamforming is also effective for multidimensional imaging using a multidimensional array.

  In addition, steering and multistatic aperture synthesis in classical aperture synthesis (monostatic type) based on scanning by driving one element at a time, which has not been disclosed so far, do not require interpolation approximation at high speed. It is desirable to carry out with high accuracy. In addition, even when so-called migration processing is used, it is desirable to process arbitrary beam forming at high speed and with high accuracy without performing interpolation approximation in an arbitrary coordinate system. Other specific examples of beam forming that are desired to be realized are as described in other parts of the present specification, and it is desirable that these beam forming can be performed at high speed and with high accuracy as well. It is.

  Accordingly, one of the objects of the present invention is to use a digital beam former having a digital calculation function and perform arbitrary beam forming at high speed and high accuracy without performing approximate calculation. This makes it possible to implement various applications of the wave described below, including super-resolution using nonlinear processing. There are various other applications such as imaging, displacement measurement, temperature measurement, etc., and the multidimensional Fourier disclosed in Non-Patent Document 13 is required to enable high-speed implementation of these applications. High-accuracy and high-speed Hilbert transform processing using transform (multi-dimensional Fourier transform is performed on the received multi-dimensional signal, and zero-padding of the spectrum in the frequency domain is performed. In this case, a quadrant (Quadrant spectrum is generated and a multidimensional inverse Fourier transform is performed), which is faster and simpler to calculate.

The present invention has been made to solve at least a part of the above problems. A beamforming method according to one aspect of the present invention is an orthogonal coordinate system that uses an axial direction determined by an aperture direction of an arbitrary receiving aperture element array and at least one lateral coordinate orthogonal thereto, and is positioned in an arbitrary direction. Waves are transmitted from at least one wave source toward the measurement object, and waves arriving from the measurement object are transmitted or received in the axial direction or a direction symmetric with respect to the axial direction by beam forming. Processed and subjected to lateral modulation in which two waves in the two-dimensional case and three or four waves in the three-dimensional case are superimposed, at least one wave coming from the measurement object is received Step (a) for receiving by an aperture element and generating a reception signal, and a beacon for the reception signal generated in step (a). A step (b) of generating a multidimensional received signal by performing lateral modulation by performing a forming process, and a step of performing a Hilbert transform process on the multidimensional received signal generated in step (b) (c) ), And the step (c) performs partial differential processing or one-dimensional Fourier transform in the axial direction or the lateral direction, and in the case of two dimensions, the analysis signal of the multidimensional received signal of each of the two waves And generating an analysis signal of the multi-dimensional received signal of each of the three or four waves in the three-dimensional case.
In addition, a measurement imaging apparatus according to one aspect of the present invention provides an arbitrary direction in an orthogonal coordinate system using an axial direction determined by the direction of the aperture of an arbitrary receiving aperture element array and at least one lateral coordinate orthogonal thereto. Waves are transmitted toward the measurement object from at least one wave source located at, and waves arriving from the measurement object are transmitted or received in the axial direction or a direction symmetric with respect to the axial direction by beam forming. In the case of performing lateral modulation in which two waves in the two-dimensional case and three or four waves in the three-dimensional case are superimposed, at least one wave coming from the measurement object is processed. Receiving means for receiving by two receiving aperture elements and generating a received signal, and a beam beam for the received signal generated by the receiving means. The apparatus main body comprises a device body that performs a Hilbert transform process on the generated multidimensional reception signal and generates a multidimensional reception signal by performing a lateral modulation by performing a teaming process. A partial differential process or a one-dimensional Fourier transform is performed in the axial direction or the horizontal direction to generate an analysis signal of a multidimensional received signal of each of the two waves in the two-dimensional case, and the three-dimensional case in the three-dimensional case. An analysis signal of the multidimensional received signal of each of the four or four waves is generated.
Furthermore, a communication device according to one aspect of the present invention is an orthogonal coordinate system that uses an axial direction determined by the orientation of an aperture of an arbitrary receiving aperture element array and at least one lateral coordinate orthogonal thereto. Waves transmitted from at least one located wave source toward the measurement object, and waves arriving from the measurement object are transmitted or received in the axial direction or a direction symmetric with respect to the axial direction by beam forming In the case of performing lateral modulation in which two waves in the two-dimensional case and three or four waves in the three-dimensional case are superimposed, at least one wave coming from the measurement object is obtained. Receiving means for generating a reception signal received by the receiving aperture element, and beam forming for the reception signal generated by the receiving means And performing a lateral modulation to generate a multidimensional received signal and a device body that performs a Hilbert transform process on the generated multidimensional received signal. In the two-dimensional case, an analysis signal of each of the two-dimensional received signals of the two waves is generated, and in the three-dimensional case, the three Alternatively, an analysis signal of the multidimensional reception signal of each of the four waves is generated.

In addition, a beamforming method according to another aspect of the present invention is an arbitrary direction in a Cartesian orthogonal coordinate system using the coordinate of the axial direction y determined by the direction of the aperture of the flat receiving aperture element array and the lateral direction x orthogonal thereto. An arbitrary wave is transmitted from the wave source located at the position toward the measurement object, and the wave arriving from the measurement object is transmitted in a direction in which the deflection angle (deflection angle) θ formed with the axial direction is zero or non-zero. The object to be measured is processed as received, and the same wave coming from the object to be measured is subject to dynamic focusing in the direction in which the deflection angle (deflection angle) φ formed with the axial direction is zero or non-zero. Receiving a wave coming from an object by at least one receiving aperture element to generate a received signal, and the reception generated in step (a) And (b) performing beam forming processing by performing at least Fourier transform and wave number matching on the signal, and step (b) performs interpolation approximation processing in the wave number domain or frequency domain for the received signal. The wave number k ₀ (= ω ₀ / c) and the imaginary number expressed by using the wave number k of the wave and the carrier frequency ω ₀ of the wave as a result of Fourier transform of the received signal with respect to the axial direction y without performing wave number matching including Perform wave number matching in the lateral direction x by multiplying the complex exponential function (101) expressed using the unit i,
Further, the product is Fourier transformed with respect to the lateral direction x to have a resolution with respect to the axial direction y, and a complex exponential function that can be implemented without the effect of wave number matching performed in the lateral direction x is obtained. 102) and at the same time multiplying the complex exponential function (103) to perform wavenumber matching in the axial direction, where the transverse wavenumber is represented as k _x ,
It includes directly generating an image signal in a Cartesian coordinate system by performing wave number matching without performing interpolation approximation processing.
In addition, the beamforming method according to another aspect of the present invention is an array type aperture element group (each element is independently driven and receives independently) in various beamforming such as Fourier beamforming and DAS processing. (With independent transmit or receive channels from which signals can be obtained), use the same transmit or receive delay or transmit or receive apodization on adjacent or distant elements as a single aperture This includes using a wave having a higher strength than transmission or reception using one element for beamforming for transmission or reception.

  The present invention is based on the proper implementation of fast Fourier transform, complex exponential function multiplication, and Jacobi calculation, without performing the approximate calculation required in normal digital processing, An apparatus and a method for performing arbitrary beam forming at high speed and high accuracy in an arbitrary orthogonal coordinate system are included. In order to solve the problem, reflected waves, transmitted waves, and scattered waves are targeted for waves such as electromagnetic waves, vibration waves (mechanical waves) including sound waves (compression waves), shear waves, surface waves, etc., or heat waves. Waves (such as forward scattered waves or back scattered waves), refracted waves, surface waves, shock waves, those generated from self-emanating wave sources, waves emitted from moving objects, or unknown wave sources For an observed wave, such as a wave coming from, an appropriately configured digital signal processing algorithm (in the implemented digital circuit or software) or analog or digital hardware is used.

  The hardware configuration may include a device equipped with a normal digital beamformer phasing addition device of each wave device, and further a device having an arithmetic function for performing digital wave signal processing. May be implemented, or a digital circuit that realizes the calculation may be configured and used. As other necessary devices, at least a normally used transducer, transmitter, receiver, storage device for received signals, and the like may be provided, as described in detail later. Harmonic waves are also processed. Beam forming using a virtual source and a virtual receiver is also performed. Parallel processing is also performed to generate multiple beams simultaneously.

  In the present invention, in order to realize high-speed and high-precision processing, in addition to the analog device such as level adjustment or analog filtering by the above-described analog amplification or attenuation, an analog signal processing device (the waveform of the drive signal) Effective application of linear elements and especially non-linear elements for changing waveforms, such as emphasizing and diminishing features, as well as devices and computers with general-purpose calculation processing capabilities as described above, PLD (Programmable Logic Device) ), FPGA (Field-Programmable Gate Array), DSP (Digital Signal Processor), GPU (Graphical Processing Unit), or microprocessor may be used, but a dedicated computer or dedicated digital circuit, or Digital processing may be performed on the stored signal using a dedicated device.

  It is important that these analog devices, AD converters, memories, and devices that perform digital signal processing (multi-core, etc.) have high performance, but the number of communication between devices, communication line capacity, wiring, or Broadband wireless communication is also important. In particular, in the present invention, in addition to the case where these functional devices are appropriately mounted on one chip or substrate (when detachable), the functional devices are directly mounted on one chip or substrate. (Including lamination) is desirable. Parallel processing is also important. If the device is non-detachable, when the computer doubles as a control unit, it is possible to obtain much higher security performance than that obtained under normal program control. On the other hand, the current law will require more disclosure of processing details.

  According to one aspect of the present invention, various applications such as wave imaging, displacement (vector) measurement, and temperature measurement are performed at high speed by a new Hilbert transform using (partial) differentiation processing or (fast) Fourier transform. Can be implemented (the former is faster than the latter). When multiple beams and waves with different wave parameters such as ultrasonic waves and beam forming parameters are generated in each time phase, the number of received signals received by the receiving transducer increases, resulting in beam forming and Hilbert transform. This is effective in such a case. In some cases, a plurality of beamformed signals are superimposed and Hilbert transform is performed at one time. When the physical aperture elements form a two-dimensional or three-dimensional distribution or a multi-dimensional array, the problem that a lot of processing time is required can be solved more effectively, and the high speed of the Hilbert transform becomes more effective. .

In addition, using a digital beam former having a digital operation function, it is possible to perform arbitrary beam forming with high speed and high accuracy without performing approximate calculation through fast Fourier transform (Fourier beam forming). . As will be described in detail later, the present invention is based on the proper use of multiplication of complex exponential functions and Jacobi arithmetic, and can perform any beamforming at high speed in any orthogonal coordinate system including a curved coordinate system. And realization with high accuracy without interpolation approximation. When multiple beams and waves with different wave parameters such as ultrasonic waves and beam forming parameters are generated, the received echo signals received by the receiving transducer may be superimposed and beam formed at once. .
Any beamforming including conventional beamforming can be realized by using a DAS (Delay and Summation) process. However, according to the present invention, when a physical aperture forms a one-dimensional array, a general-purpose PC (personal computer) is used. ), The calculation speed is significantly faster than 100 times. When the aperture elements form a two-dimensional or three-dimensional distribution or a multi-dimensional array, the problem of requiring a lot of processing time can be solved more effectively, and the high speed of beam forming becomes more effective. Of course, DAS processing may be used.

  That is, according to the present invention, a transmission or reception transducer array device (which may be used for both transmission and reception) or a sensor array device having an arbitrary aperture shape is used, and an arbitrary beam forming is interpolated at high speed. It can be realized by digital processing with high accuracy without performing the above. Virtually any focusing, any steering (deflection), any apodization can be performed with an array device having any aperture shape.

  For example, in the field of medical ultrasonic imaging, in addition to the Cartesian coordinate system using linear transducers, in the convex type, sector scan, or IVUS (intravascular ultrasound), physical transmission, reception, and digitization are performed using a polar coordinate system. What is to be done is popular and can be used according to the observation target. For example, when observing the dynamics of the heart from the gap between the sternum, a sector scan is usually performed. In addition, in the case of an array-type opening shape or a PVDF (polyvinylidene fluoride) based transducer, the opening may be deformable. That is, according to the present invention, a digital signal obtained from a wave transmitted and received in an arbitrary coordinate system is processed, and a signal directly beamformed in an arbitrary coordinate system such as an image display system is obtained without interpolation approximation. be able to. As a transducer that can generate high-frequency ultrasonic waves and PVD that can generate low-frequency but high-power ultrasonic waves and PZT (lead zirconate titanate) can generate broadband or multiple carrier frequencies simultaneously Sometimes used. For generating a plurality of different ultrasonic waves, elements having different element sizes, element intervals, or element thicknesses are arranged in an array, or variously configured arrays are stacked. There are cases.

  In multi-static aperture synthesis, echo data frames composed of echo signals received at the same position among a plurality of reception positions with respect to the transmission position are generated by the number of receiving elements, and each echo is generated in the frequency domain. The data frame is subjected to monostatic type aperture surface synthesis processing according to the present invention, and the result of superimposing these processing results is subjected to inverse Fourier transform. As a result, echo data can be generated by aperture surface synthesis processing equal to the number of channels of the reception aperture, so low spatial resolution image signals are generated and superimposed by DAS, which is known as a multistatic processing method, and high spatial resolution is achieved. It is faster than the method of generating an image signal.

  Further, based on the multi-static processing according to the present invention, dynamic reception and steering at the time of general transmission fixed focus can be performed at high speed and with high accuracy. Either can be accomplished by performing an appropriate phase rotation process using complex exponential multiplication.

  As for the coordinate system, the present invention is based on performing a Jacobi operation in the Fourier transform. For example, in the convex, sector scan, or IVUS signal processing, echo data transmitted / received in the polar coordinate system is used. Based on this, echo data can be generated directly in the Cartesian coordinate system of the display system with high accuracy and high speed without interpolation approximation.

  According to the present invention, even when so-called migration processing is used, arbitrary beam forming can be processed at high speed and with high accuracy without performing interpolation approximation in an arbitrary coordinate system. Further, according to the present invention, high-SNR and high-resolution imaging using a virtual source can be performed at high speed. Furthermore, according to the present invention, the frequency modulation and widening of the beam performed under linear processing and non-linear processing, multi-focus, parallel processing, virtual source and virtual receiver, etc. are also highly accurate at high speed under digital processing. Can be realized. The present invention is also useful in the optimization of beam forming that requires a calculation amount.

  In addition, the beamforming method according to another aspect of the present invention is an array type aperture element group (each element is independently driven and receives independently) in various beamforming such as Fourier beamforming and DAS processing. (With independent transmit or receive channels from which signals can be obtained), use the same transmit or receive delay or transmit or receive apodization on adjacent or distant elements as a single aperture This includes using a wave having a higher strength than transmission or reception using one element for beamforming for transmission or reception. For example, in a one-dimensional array type transducer, when the element width and the element interval are shortened in order to improve the spatial resolution in the axial direction and the lateral direction, the intensity of wave of transmission and reception becomes weak (the present inventor High-precision displacement vector observation is realized at an element pitch of about 0.1 mm or less). This is also the case when a two-dimensional array or a higher-dimensional array is used (the element width and the element interval in the direction of the number of dimensions are shortened). In the case of increasing the frequency by thinning the element thickness, or in the case of using PVDF or the like whose transmission intensity is weaker than that of PZT or the like in the ultrasonic wave, the intensity of the wave becomes weak. This is effective in such cases. By the way, if the element pitch is rough, the signal that causes aliasing in the element array direction (originally digital space) is received and beamforming is performed. Therefore, in the angular spectrum of the received raw signal or the signal after beamforming, Filter out the signal in the specified band. When the element width is reduced and the element pitch is shortened as described above, a wide band is generated in the horizontal direction as confirmed by the angular spectrum, and a wide band signal can be generated in the horizontal direction by beam forming. Need to be processed. These processes are necessary in the case of all beam forming processes. Since the beam forming signal can be generated within the signal band of the angular spectrum of the received raw signal, the steering angle that can be realized by using the element array can be confirmed.

  As described above, according to the present invention, for electromagnetic waves, vibration waves (mechanical waves) including acoustic waves (compression waves), shear waves, shock waves, surface waves, etc., or waves such as heat waves, Arbitrary beamforming, regardless of transmission / reception focusing, transmission / reception steering, and transmission / reception apodization, even when the coordinate system for transmitting and receiving and the coordinate system for generating the beamformed signal are different Can be performed with high accuracy and high speed without performing interpolation approximation based on digital processing.

  This not only improves the frame rate when displaying the beamformed signal as an image, but also provides high spatial resolution and high contrast in terms of image quality, and also uses the beamformed signal for displacement and deformation. Alternatively, if the temperature or the like is measured, the measurement accuracy can be improved. The high speed of processing has a great effect in multidimensional imaging using a multidimensional array. The present invention relates to a mathematical algorithm related to wave propagation, is a result of deriving a solution through digital computation but not including approximate calculation, and cannot be easily conceived.

1 is a representative block diagram illustrating a configuration example of a measurement imaging apparatus or a communication apparatus according to a first embodiment of the present invention. The typical block diagram which shows the structural example of the apparatus main body shown in FIG. 1 in detail. The schematic diagram which shows the example of arrangement | positioning of the several transmission aperture element in a transmission transducer. The block diagram which shows the structure of the receiving unit or receiver which mounts a phasing adder, and its peripheral device. The schematic diagram of the transmission of a deflection plane wave. The flowchart which shows the digital signal processing at the time of a deflection plane wave transmission. The schematic diagram in the case of transmitting a wave wide in the angle θ direction in the polar angle (r, θ) in the radius r direction (cylindrical wave transmission). Schematic diagram of a case where a wide wave is transmitted in the direction of the radius r in the angle θ direction of the polar coordinate system (r, θ) using a virtual source installed behind a physical aperture having an arbitrary aperture shape (cylindrical wave transmission) . The schematic diagram in the case of producing | generating another opening or a wave in the position of the physical opening of arbitrary opening shapes, or the back or front. Schematic diagram of monostatic type aperture surface synthesis. Schematic diagram of spectrum generated by steering in monostatic type aperture plane synthesis (θ is steering angle). Schematic diagram of multi-static type aperture plane synthesis. Schematic diagram of fixed focusing using a linear array. The flowchart which shows the digital signal processing at the time of cylindrical wave transmission. Schematic diagram of fixed focusing using convex array. The flowchart which shows the migration process at the time of transmitting a deflection | deviation plane wave. The schematic diagram for demonstrating the example of phase aberration correction when not implementing steering in the case of using a linear one-dimensional array type transducer. The schematic diagram for demonstrating the example of a phase aberration correction when implementing a steering, when a linear one-dimensional array type transducer is used. The schematic diagram for demonstrating the example of phase aberration correction at the time of implementing steering in the case of using a two-dimensional array type transducer. The schematic diagram of the motion compensation performed by moving the search area | region provided in the next frame of a process target using the estimated value of the displacement vector of the local area | region including a point of interest or a point of interest in the case of two dimensions. The flowchart which shows an example of the signal processing by the Fourier-transform using Jacobian calculation. The figure which shows the numerical phantom used in simulation. The figure which shows the sound pressure waveform of the transmission pulse used in simulation. The figure which shows the image obtained using the method (1) in deflection | deviation plane wave transmission. The figure which shows the image obtained using the method (1) in deflection | deviation plane wave transmission. The figure which shows the deflection angle and error which were obtained using the method (1) in deflection plane wave transmission with respect to a setting angle. The figure which shows the error of the deflection angle obtained using the method (1) in the deflection plane wave transmission. The figure which shows the image obtained by using the method (1) with the compound method in deflection plane wave transmission. The figure which shows the point spread function implement | achieved using the method (1) in deflection | deviation plane wave transmission. The figure which shows the image obtained using the migration method of the method (6) in deflection | deviation plane wave transmission. The figure which shows the image obtained by the monostatic type aperture surface synthesis | combination of the method (2). The figure which shows the image obtained by the multistatic type aperture surface synthesis | combination of the method (3). The figure which shows the point spread function implement | achieved by the multistatic type aperture surface synthesis | combination of the method (3). The figure which shows the image obtained by fixed focusing transmission of the method (4). The image obtained by the method (5-1) in the cylindrical wave transmission using the convex array and the image obtained by the method (5-1 ′) in the cylindrical wave transmission using the linear array are shown. Figure. The figure which shows the image obtained by the fixed focusing transmission of the convex type | mold array and the method (5-2). The figure which shows the example of 2 steering beams in the case of two dimensions, and the horizontal modulation | alteration of those superimposition. The figure which shows the example of 4 steering beams in the case of three dimensions, and the horizontal modulation | alteration of those superimposition. The block diagram which shows the structural example of the imaging device which concerns on the 3rd Embodiment of this invention. The block diagram which shows the structural example of the imaging device which concerns on the 4th Embodiment of this invention and its deformation | transformation. The schematic diagram which shows the example of arrangement | positioning of a some transducer. The figure for demonstrating the form of the wave in the case of using a one-dimensional transducer array. The figure which shows the angle of the beam direction in the space area | region and frequency domain in the case of two-dimensional measurement, the angle of the arrival direction of a wave, and the gravity center of a spectrum. The figure which shows two deflection | deviation beams used for a horizontal direction modulation method in two-dimensional space. The figure which shows the example which reads and processes a frequency coordinate axis, when a folding arises in the two-dimensional spectrum of the band 2A of a depth direction by the demodulation at the time of two-dimensional lateral modulation. The figure which shows the example which reads and processes a frequency coordinate axis, when a folding arises in the two-dimensional spectrum of the horizontal band 2B by the demodulation at the time of two-dimensional horizontal modulation. The figure which shows the change of the spectrum of the echo signal by one Embodiment of this invention. The figure which shows the change of the autocorrelation function of the echo signal by one Embodiment of this invention. The figure which shows the change of the autocorrelation function of the echo signal by one Embodiment of this invention. The figure which shows the change of the autocorrelation function of the echo signal by one Embodiment of this invention. The figure which shows the change of the B mode echo image by one Embodiment of this invention. The figure which shows the change of the B mode echo image by one Embodiment of this invention. The figure which shows the change of the B mode echo image by one Embodiment of this invention. The figure which shows the image of the displacement vector, distortion tensor, and relative shear modulus which were measured in the agar phantom by one Embodiment of this invention. The figure which shows the sound pressure change by one Embodiment of this invention at the time of using a concave HIFU applicator.

  Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings. In addition, the same code | symbol is used for the same component and the overlapping description is abbreviate | omitted. The apparatus according to the present invention can be used as a measurement imaging apparatus or a communication apparatus. In the following, mainly when the wave is a sound wave such as an ultrasonic wave, the sound pressure or the particle velocity, and as a mechanical wave, a compression wave (longitudinal wave) or a shear wave, a shock wave, a surface wave, a stress wave or When distorted waves and electromagnetic waves are targeted, image signals of electric or magnetic fields, and when heat waves are targeted, transmitted signals of temperature or heat flux, refracted waves, reflected waves, scattered waves (forward scattered waves, backward scattered waves, etc.) The case of generating will be described.

<< First Embodiment >>
First, the configuration of the measurement imaging apparatus or the communication apparatus according to the first embodiment of the present invention will be described. FIG. 1 is a representative block diagram illustrating a configuration example of a measurement imaging apparatus or a communication apparatus according to the first embodiment of the present invention. As shown in FIG. 1, a measurement imaging apparatus (or communication apparatus) according to the present embodiment includes a transmission transducer (or applicator) 10 that is a transmission unit, a reception transducer (or reception sensor) 20 that is a reception unit, A device main body 30, an input device 40, an output device (or display device) 50, and an external storage device 60 are provided.

  FIG. 2 is a representative block diagram showing in detail the configuration example of the apparatus main body shown in FIG. The apparatus main body 30 mainly includes a transmission unit 31, a reception unit 32, a digital signal processing unit 33, and a control unit 34. Here, the receiving unit 32 may include a digital signal processing unit 33. FIG. 1 and FIG. 2 are appropriately simplified block diagrams, and the present embodiment is not limited to these, and details of the present embodiment are as follows. As an example, communication is appropriately performed between the devices described above, between the units in the device main body 30, and within each unit based on wired technology or wireless technology, and may be installed at a remote location. The apparatus main body 30 is composed of a plurality of such units, and is referred to as such for convenience.

<Transmission transducer>
The transmission transducer (or applicator) 10 shown in FIG. 2 generates a wave by a drive signal supplied from the transmission unit 31 in the apparatus main body 30 and transmits it. In the present embodiment, the plurality of transmission aperture elements 10a of the transmission transducer 10 form an array.

  FIG. 3 is a schematic diagram illustrating an arrangement example of a plurality of transmission aperture elements in the transmission transducer. FIG. 3 (a1) shows a plurality of transmission aperture elements 10a densely arranged in a one-dimensional array, and FIG. 3 (b1) shows a plurality of transmission aperture elements 10a sparsely arranged in a one-dimensional shape. Is shown. FIG. 3 (a2) shows a plurality of transmission aperture elements 10a that are densely arranged in a two-dimensional array, and FIG. 3 (b2) shows a plurality of transmission aperture elements 10a that are sparsely arranged in two dimensions. Is shown. FIG. 3 (a3) shows a plurality of transmission aperture elements 10a densely arranged in a three-dimensional array, and FIG. 3 (b3) shows a plurality of transmission aperture elements 10a sparsely arranged in a three-dimensional shape. Is shown.

  Each transmission aperture element 10a has a rectangular, circular, hexagonal, or other aperture shape, and may be flat, concave, or convex, and the array may be one-dimensional, two-dimensional, or There are three-dimensional ones. The directivity of one transmission aperture element 10a is determined by the frequency and bandwidth of the generated wave and the shape of the aperture of the transmission aperture element 10a, and is usually expressed in a two-dimensional space or more, but at least orthogonal. A so-called opening that faces two directions orthogonal to each other so as to have directivity in two directions may be counted as one element, and three directions that so-called openings cross so as to have directivity in three directions orthogonal to each other. There is also a case where the one suitable for the device is counted as one element. There is also an element having an opening in which the opening is directed in more directions than three directions so as to have directivity in more directions than three independent directions. They differ depending on the position and may be mixed.

  Although the transmission aperture elements 10a may exist spatially densely or sparsely (separated positions), the present embodiment will be described without being particularly distinguished from a one-dimensional to three-dimensional array type. Aperture element array is used for IVUS in linear type (element arrangement is flat), convex (convex arc arrangement), focus type (concave arc arrangement), circular type (for example, medical ultrasound) ), Spherical, convex or concave spherical shells, and other shapes that are arranged in a convex or concave shape, various aspects can be taken for objects (communication objects) that propagate waves and observation objects. However, it is not limited to these. By appropriately driving these aperture element arrays, wave transmission, steering, aperture synthesis, fixed transmission focus, etc., in which the wavefront of the plane wave or the like spreads in the horizontal direction are performed, and one beam or generated A transmission wave having a wavefront is realized.

  Regarding electronic scanning, as described in detail later, in order to generate a transmission wave having one transmission beam or wavefront, the driving is performed by independent drive signals generated by a plurality of transmission channels included in the transmission unit 31 shown in FIG. The same number of transmission aperture elements 10a as the number of signals can be driven independently. A transmit aperture element array used to generate a transmit wave having one transmit beam or wavefront is also referred to as a transmit effective aperture. Further, it is distinguished from a physical aperture element array that collectively refers to all aperture elements, and the transmission aperture realized by the transmission aperture element 10a that is driven simultaneously is also referred to as a transmission sub aperture element array or simply a transmission sub aperture. is there.

  In order to observe the entire region of interest at once when the wave propagation object (communication object) is wide, the number of transmission channels of the total number of aperture elements in the physical aperture element array is provided, and all of them can be used at all times. However, in order to reduce the cost of the apparatus, the transmission channel is electronically switched to shift the transmission sub-aperture element array (electronic scanning), or the physical aperture element array is mechanically scanned (mechanical scanning). A wave may be transmitted throughout the region of interest using a minimum number of transmission channels. When a wave propagation target (communication target) is wide or an observation target is large in size, both electronic scanning and mechanical scanning may be performed.

  When sector scanning is performed, a spatially fixed aperture element array of the above type is electronically driven and scanned (electronic scanning), or the aperture element array itself is mechanically scanned. (Mechanical scanning) or both may be performed together. In classic aperture plane synthesis, electronic scanning is performed electronically for each element of an aperture element array, or mechanical transmission of one aperture element is used to transmit at different positions to form a transmission aperture array. In this case, the transmission unit 31 may have the number of transmission channels corresponding to the number of elements of the physical aperture array. However, if a switching device is used, the number of transmission channels can be reduced. Need. When transmitting polarized waves, the transmission unit 31 needs to have at least the number of channels obtained by multiplying the number of elements driven at one time by the number of polarized waves.

<Receiving transducer>
The reception transducer (or reception sensor) 20 shown in FIG. 2 may also serve as the transmission transducer 10, but may be an array type sensor dedicated to reception that is used separately from the transmission transducer 10. Accordingly, the receiving transducer 20 may be set at a position different from that of the transmitting transducer 10. The receiving transducer 20 may sense a wave different from the wave generated by the transmitting transducer 10. Such a receiving transducer 20 may be installed at the same position as the transmitting transducer 10 or may be integrated.

  As in the case of the transmission transducer 10, the reception transducer 20 in the present embodiment includes at least one reception aperture element 20 a constituting an array, and signals received by the respective elements are in an independent state in the apparatus main body 30. To the receiving unit 32 (FIG. 2). Similar to the transmission aperture element 10a, the reception aperture element 20a has a rectangular, circular, hexagonal, or other aperture shape, and may be flat, concave, or convex. There are dimensions, two dimensions, or three dimensions. The directivity of one reception aperture element 20a is determined by the frequency and bandwidth of the wave to be received and the shape of the aperture of the reception aperture element 20a, and an element having a plurality of apertures may be counted as one element. The number of openings in one element varies depending on the position and may be mixed. Further, there are cases where the reception aperture elements 20a are spatially dense or sparse (separate positions), and are not distinguished from the array type here (see the example of the transmission array in FIG. 3).

  Similar to that of the transmission transducer 10, the aperture element array is linear type (element arrangement is flat), convex (convex arc arrangement), focus type (concave arc arrangement), circular type (for example, For objects that propagate waves (communication objects) and observation objects such as spherical, convex or concave spherical shells, and other shapes that are aligned in a convex or concave shape. However, various aspects are taken, and the present invention is not limited to these. Waves are received using these aperture element arrays, and wave reception, steering, aperture synthesis, fixed reception focus, dynamic focus, etc., in which the wavefront of the plane wave or the like spreads widely in the lateral direction, is performed. Received waves with beams and generated wavefronts are realized.

  Transducer apertures (elements) are not spatially dense and may exist in sparse (remote positions), and the measurement target may be mechanically scanned and transmitted or received. In the case of using a transducer that is not referred to as an array type, the received signal may be processed in the same manner. However, in this application, the case where an array type device is used is described without particular distinction. The present invention will be described. For example, when there is a radar aperture at a remote location on land, each radar may or may not constitute an array.

  In addition to radar mounted on satellites and airplanes, the object to be measured may be mechanically scanned by a transducer. Even in such a case, the transducer may or may not form an array. The signal may be transmitted or received continuously in high density or spatially sparsely in remote locations. Therefore, in addition to classical aperture plane synthesis (transmission by a single aperture element), signals may be received while performing transmit beamforming. The aperture element may exist in a one-dimensional form, or may exist in a two-dimensional or three-dimensional space. In addition, mechanical scanning may be performed while performing electronic scanning.

  Regarding electronic scanning, as will be described in detail later, in order to realize a reception wave having one reception beam or a generated wavefront, independent reception signals of the number of reception channels included in the reception unit 32 are received at a time at the aperture element. (The reception effective aperture is determined). The reception effective aperture may be different from the transmission effective aperture. It is distinguished from a physical aperture element array that collectively refers to all aperture elements, and the reception aperture realized by the reception aperture element 20a used at the same time may be referred to as a reception sub aperture element array or simply as a reception sub aperture.

  In order to observe the entire region of interest at a time when the wave propagation object (communication object) is wide, the receiving unit 32 includes the number of reception channels of the total number of aperture elements provided in the physical aperture element array. All may be used, but in order to reduce the cost of the device, the receiving channel is electronically switched to shift the receiving sub-aperture array (electronic scanning), or the physical aperture element array is mechanically scanned. (Mechanical scanning) may receive waves coming from the entire region of interest using a minimum number of received channels.

  When a wave propagation target (communication target) is wide or an observation target is large in size, both electronic scanning and mechanical scanning may be performed. When a sector scan is performed, a spatially fixed aperture element array of the above type is electronically driven to scan while repeating transmission and reception (electronic scanning), or The aperture element array itself may be mechanically scanned (mechanical scanning) or both may be performed together. Also, in the classic aperture plane synthesis, as described above, transmission is performed at different positions through electronic scanning that is electronically driven for each element of the aperture element array or mechanical scanning of one aperture element as described above. In order to constitute the transmission aperture array, the transmission unit 31 may have as many transmission channels as the number of elements of the physical aperture array in electronic scanning. However, at least one channel is always required by using a switching device as in the case of mechanical scanning. Need.

  On the other hand, regarding the reception at that time, in the case of the monostatic type in which reception is performed only by the same element as the active transmission element, the reception unit 32 may be provided with the reception channel in the same manner as the transmission channel. Further, in the multi-static type in which reception is often performed by a plurality of surrounding elements including active transmission elements, the reception unit 32 may have the number of reception channels corresponding to the number of elements of the physical aperture array in electronic scanning. By using the switching device, it is only necessary that the receiving unit 32 has at least the number of reception channels equal to the number of elements of the reception effective aperture in both electronic scanning and mechanical scanning. When receiving polarized waves, the receiving unit 32 needs at least the number of channels obtained by multiplying the number of receiving elements by the number of polarized waves.

<Specific examples of transducer>
There are various transducers 10 or 20 that can generate or receive electromagnetic waves, light, dynamic vibrations, sound waves, or arbitrary waves such as heat waves. For example, the transducer 10 may transmit an arbitrary wave to the measurement target and receive a reflected wave reflected in the measurement target, a backscattered wave, or the like (also serves as the transducer 20). For example, when an arbitrary wave is an ultrasonic wave, an ultrasonic transducer that transmits an ultrasonic wave according to a drive signal and receives the ultrasonic wave to generate a reception signal can be used. It is well known that the ultrasonic elements (PZT (Pb (lead) zirconate titanate), polymer piezoelectric elements, etc.) are different depending on the application, and the structure of the transducer is different.

  In medical applications, blood flow measurement has historically used narrow-band ultrasound, but the inventor of the present application has found that soft tissue displacements and strains that have been put into practical use in recent years (in static cases). Including the measurement of shear wave propagation (velocity), the use of a broadband transducer for (echo) imaging has been realized for the first time in the world. The same applies to HIFU treatment, and continuous wave may be used, but the inventor of the present application has also developed an applicator using a high-frequency type or broadband type device in order to realize high-resolution treatment. Yes. When using high-intensity ultrasound, the tissue may be stimulated within a range that does not produce a heating effect, and a force source may be generated in the measurement target as described above. A transducer for (echo) imaging is used. Sometimes. Heat treatment, force source generation, and (echo) imaging may be performed simultaneously. The same applies to other wave sources and transducers.

  In the digital signal processing unit 33, a plurality of force sources can be generated in the object in time or space, and the propagation direction of the shear wave can be controlled by overlapping the shear waves. It is possible to measure the shear modulus and the anisotropy of the propagation velocity. Since shear waves generated almost simultaneously overlap physically, shear waves may be separated under spectral analysis after observation of shear waves through ultrasonic displacement meter measurement. In addition, when there is no physical overlap, the shear wave generated by each force source is observed by analyzing the ultrasonic signal, and the results are superimposed and (viscosity of propagation direction, propagation speed, propagation direction) ) The shear modulus (Patent Document 11 etc.) may be required, but the ultrasonic signals when each force source is generated are superposed and analyzed, and the superposition of shear waves is observed to obtain them. Sometimes. The same applies when generating heat sources and observing heat waves and thermal properties. Thereafter, various other processes are performed.

  The shape of the heat source, force source, and sound pressure can be adjusted by transmission / reception apodization, delay, and radiation intensity. By detecting the transmitted or reflected waves when they are generated and optimizing them, Desired heat source, force source, and sound pressure can be realized. The shape of the signal may be observed with high sensitivity using a hydrophone, or the shape of the signal may be estimated by obtaining an autocorrelation function for the signal captured by the detector (Patent Document 11, etc.) Based on these processes, linear or non-linear optimization is performed. The propagation direction of shear waves and heat waves may be optimized. In each of these cases, it is desirable to use estimated results of mechanical properties and thermophysical properties.

  For example, when a concave applicator is used, high-intensity ultrasonic waves can be converged at the focal position, resulting in a wide band in the lateral direction. However, since the sound pressure shape has a distribution that draws a foot from the focal position, the sound pressure shape is made elliptical by processing (filtering, weighting, etc.) the spectrum obtained after receiving the reflected wave or transmitted wave. It can be processed (Patent Document 7). What is necessary is just to apply that the spectral component in each direction of the wave or beam is confirmed as a spectrum in the same direction in the frequency domain. As a result, the quality of imaging is improved and the accuracy of displacement measurement is improved.

  Wave parameters and beam forming parameters include focus position with transmission focusing, plane wave, cylindrical wave, spherical wave without transmission focusing, deflection angle (including zero degree without deflection), with apodization or None, F number, transmission ultrasonic frequency or transmission band, reception frequency or reception band, pulse shape, beam signals with different wave shapes, etc. When generating a wave or beam with new characteristics that cannot be generated by wave generation or beam forming due to multiple transmissions and receptions (for example, when a wave or beam is crossed and overlapped to be laterally modulated or widened, multi-focus Etc.), the same effect may be obtained by performing the same processing. Note that superposition may be performed in real time at the same time, or may be performed with respect to those received at different times in the same time phase of interest. Each of them may be superposed by receiving beam forming, or may be superposed on those that have not been subjected to receiving beam forming, and may be superposed on the receiving beam.

  A single wave or beam, or a received signal obtained from superposition of a plurality of waves or beams, may be weighted in the frequency domain to be broadened and super-resolution may be performed (high resolution). . This is so-called inverse filtering or deconvolution. The method described in paragraph 0009 may be used in combination, and the observed wave may be subjected to conjugate or reciprocal frequency response as inversion of the beam characteristics. In addition, conjugate of the observed wave or frequency response may be performed (these are detection processes, the former obtains the square of the envelope, and the latter produces the self spectrum, ie, the autocorrelation function. can get). Super-resolution may be applied to those that have undergone beam forming (including aperture synthesis), or super-resolution to those that have not been subjected to receive beam forming or that have not been subjected to beam forming at all (transmission / reception signals for aperture synthesis). Beam forming may be performed after image processing.

  Further, in displacement (vector) measurement, in order to increase the accuracy of the displacement component, the frequency in the direction of the displacement component may be increased. When higher resolution is required, it is necessary to increase the bandwidth. For example, the low-frequency spectrum can be discarded to increase the frequency, and the displacement measurement can be made highly accurate. The calculation amount can also be reduced. When a plurality of waves or beams are physically generated or a spectrum is divided by signal processing to generate a plurality of waves or beams, an over-determined system is configured to perform highly accurate displacement measurement, etc. (It is often better to divide the beam after beam forming if the angular spectrum before beam forming is divided and beam forming is performed for each). For imaging, envelope detection, square detection, and absolute value detection are performed. By overlapping a plurality of waves or beams after detection, speckles can be reduced and specular reflection can be enhanced.

  Note that these processes can be similarly performed not only in the case of using ultrasonic waves and in medical treatment, but also in the case of using electromagnetic waves and in various fields. For example, it is possible to observe audible sound waves using ultrasonic waves (that is, Doppler effect), observe sound waves and heat waves using electromagnetic waves and light, and observe seismic waves using them. In conjunction with this, it is also possible to observe related physical properties (distribution).

  There are two types of transducers: contact type and non-contact type. Each time, an alignment material is used (in the case of ultrasonic waves, gel, water, etc.), or an alignment material is previously incorporated in the transducer (ultrasonic wave). In this case, the matching layer is used, and the impedance matching of each wave is appropriately performed on the object to be measured. Aperture element level and array include power, carrier frequency, bandwidth (determines broadband or narrow bandwidth, axial spatial resolution), waveform shape, element size (determines lateral spatial resolution), directivity, etc. Those designed in both aspects of performance are used (details omitted). As ultrasonic transducers, there are composite ones such as those in which PZT and PVDF are laminated and have both transmission acoustic power and broadband characteristics.

  In the case of forced oscillation by the drive signal, the frequency and band of the generated ultrasonic wave may be adjusted or encoded by the drive signal (with respect to reception, the signal in the transducer band Or band selection using analog or digital filters). In some cases, aperture elements having different characteristics such as frequency and sensitivity are arranged. Medical ultrasonic transducers were originally handy and easy to use, but recently, non-cable type transducers have been used with handy size device bodies. If the sound has a low frequency (for example, an audible sound), there are a speaker and a microphone. Other wave transducers may be realized from a similar point of view, but are not limited thereto.

  Alternatively, the transducer 10 may be a transmission transducer that generates an arbitrary wave, and the transducer 20 may be a reception transducer (sensor) that receives the arbitrary wave. In that case, the transmitting transducer transmits an arbitrary wave to the measurement target, and the sensor reflects the reflected wave or the back-scattered wave reflected in the measurement target, or the transmitted wave transmitted through the measurement target or the like. Refractive waves, forward scattering, etc. can be received.

  For example, when an arbitrary wave is a heat wave, a heat source that is not intentionally generated such as sunlight, lighting, or metabolism in the living body may be used, but an infrared heater, heater, etc. Ultra-sound transducers that transmit heating ultrasonic waves that are often controlled according to drive signals (sometimes generating a force source in the measurement target), electromagnetic wave transducers, lasers, etc. used. Infrared sensors that receive heat waves and generate received signals, pyroelectric sensors, microwave and terahertz wave detectors, temperature sensors such as optical fibers, and ultrasonic transducers (temperature dependence such as ultrasonic sound velocity and volume change) The temperature change can be detected by using a magnetic property) or a nuclear magnetic resonance signal detector (temperature can be detected by using a chemical shift of nuclear magnetic resonance). For each wave, a transducer that can receive properly is used.

  Optical digital cameras and mammography use CCD (charge coupled device) technology, and an integrated circuit and a sensor body may be integrated. The same technology is also applied to an ultrasonic two-dimensional array, and real-time three-dimensional imaging is possible. A combination of scintillator and photocoupler is used for X-ray detection, but it has been a long time since it can be observed as a wave. In capturing a high-frequency signal as a digital signal, it is effective to perform analog detection or modulation for pre-processing, and to perform AD conversion at a low frequency and store it in a memory or a storage device (storage medium). Sometimes digital detection is performed. These may be integrated by a chip or a substrate together with a transmitter and a receiver.

  In addition, for example, each aperture may form an array, such as when a radar is located at a remote location on land, and there are cases where the aperture is not limited thereto. The aperture may be scanned mechanically to obtain a wide directivity. Openings are irregular in a spatially continuous high density, spatially sparse at distant locations, at regular intervals, etc., and under physical constraints In some cases, it is installed. In addition, the position may be fixed with respect to the object (communication object) to propagate the wave and the observation position, such as in the ocean, in a building, or indoors. They may be dedicated openings for wave transmission or reception. In addition, each opening may serve as both, but it does not necessarily receive a response of a wave transmitted by itself, and may receive a wave transmitted by another opening. In medical and biological observations, it is called photoacoustic, and ultrasonic waves generated by laser irradiation are sometimes observed (a plurality of wave transducers may be integrated). According to the present invention, for example, photoacoustics using an ultrasonic diagnostic apparatus and OCT can be measured not only for distinguishing between arteries and veins but also for measuring blood flow velocity in each (super-resolution can also be performed). it can). In addition, a magnetic substance having affinity for a lesion can be intravenously injected as a contrast medium, and vibrations such as ultrasonic waves can be applied to the affected area to observe electromagnetic waves. It may communicate with various mobile objects using radio waves.

  Various transducers (arrays) used for passive observations such as seismic waves (seismic meters), magnetoencephalograms (SQUID arrays), brain waves, electrocardiograms, neural networks (electrode arrays), radio waves (antennas), radars, etc. Some of them are used to observe wave sources. The propagation direction of the arriving wave is obtained based on multidimensional spectral analysis (the past achievements of the inventor of the present application). Further, in the apparatus of the present invention, a plurality of transducers or reception effective apertures provided at different positions are obtained. It is possible to geometrically determine the position of the wave source even when the information about the propagation time is not obtained (usually, the position of the wave source is determined from the time when the waves are observed at a plurality of positions). Is possible. Waves can be observed with continuous waves instead of pulse waves and burst waves. Through any process, when the direction of arrival of the wave is known, various beams can be steered and focused in that direction for detailed observation. In those processes, receive beamforming is always performed while changing the steering angle, focusing on the likely direction, and the resulting image or imaging, spatial resolution, contrast, signal strength, etc. are observed, or The direction of the wave source can also be specified through multidimensional spectral analysis. Therefore, the transducer used in the apparatus of the present invention is also used for steering and may be provided with a mechanism for performing electronic scanning, mechanical scanning, or both scanning.

  As transducers that can demonstrate the effectiveness of the present invention, some typical transducers that are relatively familiar and special ones are listed, but those used in the present invention include those including applications. The present invention is not limited, and various types that can generate or receive electromagnetic waves, light, dynamic vibrations, sound waves, or arbitrary waves such as heat waves can be used.

<Beam forming>
One or more beam forming at each aperture at the same time, or at the same time or at the same time, or at the same time or in the same state of the object to be propagated (communication object) or observation object Alternatively, transmission or reception may be performed. Similarly, one or more beamforming or transmission or reception may be performed with one combination of apertures. Similarly, each of a plurality of combinations of apertures may perform one or more beamforming, transmission, or reception. In these cases, new data may be generated through linear or non-linear calculations using them, including cases where a plurality of beamforming and reception results are obtained. There are cases where the received signals to be processed are overlapped with each other and are processed in an overlapping manner.

  Also, for example, in the case of a spatially moving object such as a radar mounted on a satellite or an airplane, the mounted aperture may or may not constitute an array, and mechanical scanning may be performed. In some cases, wide directivity can be obtained, and the regularity such as spatially continuous high density, spatially sparseness at a distant position, or equidistant spacing. Alternatively, transmission and reception may be performed irregularly as necessary. There are various other moving objects such as cars, ships, trains, submarines, and mobile robots. In addition, there are cases where things such as distributed items, creatures, etc. move regularly or randomly. In such a case, a movable communication device is used. An RFID (Radio Frequency Identification) tag, an IC card, or the like may be used.

  At that time, not only classical aperture synthesis (aperture synthesis based on transmission for each aperture element) is performed, but reception beamforming may be performed while generating transmission beamforming. In addition, mechanical scanning may be performed regularly or irregularly while electronic scanning is performed. Waves are propagated appropriately over a wide spatial range (communication), and a wide spatial range is appropriately observed. Sometimes. Of course, by using a multi-dimensional array, waves can be appropriately propagated over a wide spatial range (communication) only by electronic scanning, or a wide spatial range can be appropriately observed (physical aperture). Not only increases but also allows multi-directional steering).

  The mounted aperture may serve as both apertures for wave transmission and reception, but not only receive the response of the wave transmitted by itself, but also receive the wave transmitted by any other aperture Sometimes. In addition, a plurality of moving objects may have openings, and at the same time, a simultaneous phase in which the wave propagation target (communication target) and the state of the observation target are the same or substantially the same, or another time or In another time phase, one or more beamforming, or transmission or reception may occur at each aperture.

  Similarly, one or more beamforming, transmission, or reception may be performed with one combination of apertures. Further, similarly, each of a plurality of combinations of apertures may perform one or more beam forming, transmission, or reception. Also, in these cases, new data may be generated through linear or non-linear calculations using them, including cases where a plurality of beamforming and reception results are obtained. In the above, a combination of an aperture of a moving object and a fixed aperture may be used for an object (communication object) for propagating a wave or an observation object.

  Thus, in the present embodiment, there are a plurality of transmission aperture elements 10a and a plurality of reception aperture elements 20a (one aperture element may serve as both the transmission aperture element 10a and the reception aperture element 20a). Beam forming is actively performed. In this active beam forming, arbitrary beam forming can be realized by digital processing without performing interpolation approximation at high speed through fast Fourier transform. Also, virtually any focusing and any steering can be implemented using a transducer array device having any aperture shape.

  The transmission is generally performed in an orthogonal coordinate system determined by the shape of the physical aperture element array in order to place importance on the direction of each aperture element (virtual sound source will be described separately). In order to generate a signal directly representing a wave in a simple display coordinate system, it is mainly to perform reception digital beam forming without performing interpolation approximation processing. There is also forming. In addition, a virtual source, a virtual receiver, or the like may be used, and beam forming is performed as in the case of the physical aperture element array.

<Transmission unit>
Next, the transmission unit 31 (FIG. 2) provided in the apparatus main body 30 will be described. The transmission unit 31 includes a plurality of transmission channel transmitters 31a. The number of transmission channels is the number of lines for sending different drive signals to the aperture elements used for performing one beamforming. For example, as described below, there are various forms of this transmission channel. The frequency, bandwidth, waveform, and directivity of the wave generated in each transmission aperture element 10 a are determined by the transmission aperture element 10 a and the transmission unit 31.

  When an impulse signal is applied to the transmission aperture element 10a, a wave determined by the shape (thickness and size and shape of the aperture) of the transmission aperture element 10a and the material (single crystal as a typical ultrasonic element) is generated. The frequency and band of a wave generated by forcibly exciting the transmission aperture element 10a with a drive signal generated in the transmission unit 31 and having a frequency, a bandwidth, and a waveform (which may be encoded) The width, waveform, and directivity are adjusted. The characteristics of the generated drive signal are set as parameters under the control of the control unit 34. Although the control unit 34 recognizes the transducer to be used and the recommended setting may be automatically performed, the setting or adjustment using the input device 40 is also possible.

  Normally, in order to drive a plurality of aperture elements with drive signals multiplied by different delays when performing one beam forming, the transmission unit 31 is equipped with an analog or digital delay pattern, and an operator can input the input device 40. A delay pattern that realizes a transmission focus position, a steering direction, and the like that can be selected using the. These patterns are programmable, and the patterns to be used and selectable patterns may be installed through various media such as a CD-ROM, floppy disk, or MO depending on the purpose. In some cases, a program can be started and a pattern can be selected interactively from the input device 40, a delay (pattern) value can be directly input, or a file in which data is recorded can be read and set. There are cases. In particular, in the case of an analog delay, the delay value to be used may be changed in an analog or digital manner, or the delay circuit or the pattern itself may be replaced with another one or switched.

  In the apparatus main body 30 (FIG. 2), a command signal for generating a drive signal (which may be encoded) for driving the corresponding transmission aperture element 10a is transmitted from the control unit 34 to the transmitter 31a of a plurality of channels. The These command signals may be generated based on a command signal for starting beam forming for one frame. When the transmission delay is digital, for example, a digital delay is applied with a command signal sent to the transmitter 31a for the transmission aperture element to be driven first as a trigger, and the command signal is sent to each transmitter 31a. is there. A digital circuit delay device may be used for the digital delay.

  In addition, an analog delay may be applied to the drive signal itself generated in the transmitter 31a for the element to be driven first, and transmitted to each aperture element. In this case where an analog delay that does not require synchronization is used, the transmitter 31a can drive a plurality of transmission aperture elements 10a with at least one device. Therefore, the transmission analog delay is provided before and after or inside the transmitter 31a or in the control unit 34, while the transmission digital delay is provided in or before the transmitter 31a or in the control unit 34. There is.

  A pattern may be selected by switching between an analog circuit or an analog device, or a digital circuit or a digital device, but the delay of these delay devices may be changed under the control of the control unit 34. It may be programmable through installation, input settings, and the like. In addition, a delay device may be provided in the control unit 34. Further, when the control unit 34 is configured by a computer or the like as described below, a command signal delayed by software control may be directly output from the control unit 34.

  The control unit 34 and the digital delay are devices and computers having general-purpose calculation processing capability, PLD (Programmable Logic Device), FPGA (Field-Programmable Gate Array), DSP (Digital Signal Processor), GPU (Graphical Processing Unit), or , A microprocessor, etc., or a dedicated digital circuit or a dedicated device. They are desirably high performance (such as multi-core) and may also be responsible for analog devices, AD converter 32b, memory 32c, and / or digital signal processing unit 33 that performs transmit or receive beamforming processing.

  In addition, the number of communication between devices, communication line capacity, wiring, or broadband wireless communication is important. In particular, in the present invention, when these functional devices are appropriately mounted on one chip or substrate ( Detachable). In addition, they may be directly mounted on one chip or substrate (including stacking). Parallel processing may be performed. If the device is non-detachable, when the computer also serves as the control unit 34, it is possible to obtain much higher security performance than security obtained under normal program control. On the other hand, the current law will require more disclosure of processing details.

  Some control software and delay values are coded or input directly, and some are installed. The method of applying the digital delay is not limited to these. When this digital delay is performed in the transmission delay, unlike the analog delay, an error determined by the clock frequency for generating the digital control signal is inevitably generated. Therefore, in terms of accuracy, the transmission delay is preferably the analog delay. Basically, a high clock frequency is used at a cost to reduce errors. On the other hand, the analog delay can be changed in an analog manner, or can be made digitally programmable. However, the degree of freedom is lower than that of a digital delay, and when the cost is reduced, a delay pattern mounted as an analog circuit may be switched and used.

  Note that the transmission apodization is performed by changing the energy of the driving signal of the aperture element and the time change of the amplitude of a waveform (which may be encoded) that changes with time. The drive signal is adjusted based on the calibration data of the conversion efficiency (convertibility) of the drive signal of the aperture element into the wave. For other purposes, adjustments to the drive signal may be performed solely for calibration purposes. The command signal sent from the control unit 34 to the transmitter 31a may represent the waveform and phase information of the drive signal generated by the transmitter 31a as a time series, or the transmitter 31a recognizes the predetermined signal. It may be an encoded signal that can generate a drive signal, or it simply gives a transmission command to the transmitter 31a that generates a predetermined drive signal for the position of each aperture element to be driven within the effective aperture. There may be.

  Similarly to the delay, the transmitter 31a may be programmable so as to generate a predetermined drive signal for the position of each aperture element to be driven within the effective aperture, and can take various forms. A power supply or an amplifier is used to generate a drive signal, but power supplies with different power or energy supply amounts or amplifiers with different amplification levels are switched and used simultaneously to generate one drive signal. In addition, as with the transmission delay pattern, it may be set directly or programmable as described above. The delay and the apodization can be implemented in the same or different forms at the same or different hierarchical levels in the transmission unit.

  The transmission channel for driving the aperture element in the transmission effective aperture is switched through a switching device such as a shift register or a multiplexer, and the region of interest is scanned while performing beam forming using the effective aperture at another position. There is. Some delay elements have variable delay values, and delay patterns (delay element groups) may be switched. Further, steering in a plurality of directions may be performed at one effective opening, and further steering may be performed in a plurality of directions while appropriately changing the opening position and the effective opening width.

  In the case of switching a high voltage signal, a dedicated switching device is used. In some cases, the apodization value of the apodization element is variable in the transmission time direction and the array direction of the aperture element, and the apodization pattern (apodization element group) may be switched, and the aperture position, range direction, or steering direction Depending on the beam shape, the beam shape may be adjusted. Specifically, it means that a transmitting element with zero apodization value is not active and is off, and apodization can also act as a switch for the effective element and can determine the effective aperture width (apodization in the direction of the aperture element array). If the function is a rectangular window, the switch is on. If it is not a constant value, the switch is on).

  Further, regarding the delay pattern and the apodization pattern, the apparatus main body 30 may be provided with a plurality of patterns or may be programmable. Based on the response from the transmission target and the result of beam forming by the receiving unit 32 described below, In the digital signal processing unit 33 (FIG. 2) in the apparatus main body 30 to be described later, wave attenuation and scattering (forward scattering, back scattering, etc.), transmission, reflection, refraction, or sound velocity frequency dispersion in a propagation medium. And spatial distribution may be calculated, and the delay and intensity of the wave transmitted from each aperture, the steering direction of the beam and wavefront, the apodization pattern, etc. may be optimized.

  In addition, in the classical aperture plane synthesis, there are a monostatic type and a multistatic type performed in transmission by a single aperture element, and the active transmission aperture element 10a is subjected to switching or apodization as described above. Can be switched. In some cases, all transmission elements have a transmission channel including the transmitter 31a. In aperture plane synthesis, it is necessary to generate a wave of sufficient intensity or energy, and the transmission apodization function itself is not necessarily important. In practice, the aperture plane synthesis is usually performed simultaneously with reception apodization in the phasing adder, and in the present invention, it is often performed simultaneously with reception apodization in the digital signal processing unit 33. The representative transmission unit of the present embodiment has been described above. However, any transmission unit that can perform transmission beamforming can be used, and is not limited to the description.

<Receiving unit and digital signal processing unit>
Next, the receiving unit 32 and the digital signal processing unit 33 (FIG. 2) included in the apparatus main body 30 will be described. The reception unit 32 includes a receiver 32a of a plurality of reception channels, an AD converter 32b, and a memory (or storage device or storage medium) 32c. The frequency, bandwidth, waveform, and directivity of the reception signal generated in each reception aperture element are determined by the reception aperture element 20a and the reception unit 32. When the wave arrives at the reception aperture, a reception signal is generated which is determined by the shape (thickness or size and shape of the aperture) of the reception aperture element 20a and the material (single crystal as a typical ultrasonic element). The frequency, bandwidth, and directivity of the received signal generated by the filtering process in the unit 32 (which may also serve as an analog amplifier) are adjusted. The generated reception signal is substantially adjusted based on filter parameters (frequency characteristics such as frequency and bandwidth) set under the control of the control unit 34. Although the control unit 34 recognizes the transducer to be used and the recommended setting may be automatically performed, the setting or adjustment using the input device 40 is also possible.

  A normal digital receiving unit or digital receiving apparatus has such a function, and further has a phasing addition function. That is, the DAS process in the digital reception unit or the digital reception apparatus performs a phasing process on a plurality of reception signals and adds the plurality of reception signals subjected to the phasing process. As the phasing process, the received signals are AD-converted in the reception channels of a plurality of reception apertures, and are basically stored in a memory, a storage device, a storage medium, or the like that can be read and written at high speed. It takes a lot of time to delay the reception signal read from the storage destination by interpolating approximation processing in the spatial domain in order to adjust the phase of interest, but it takes a lot of time. In the present invention, a delay is applied with high accuracy based on the Nyquist theorem by phase rotation multiplied by a complex exponential function (the invention of the present inventor, Patent Document 6, Non-Patent Document 15, etc.). In addition, at the storage destination, the reception signals of the respective reception openings may be stored at positions corresponding to the reception delay, and these reception signals are read out and added, or the above processing is further performed on them. May be added.

  FIG. 4 is a block diagram showing a typical configuration of a receiving unit or a receiving apparatus equipped with a phasing adder that realizes a phasing addition process and its peripheral devices. The receiving unit (or receiving device) 35 shown in FIG. 4 performs a phasing addition process in addition to a receiver 35a, an AD converter 35b, and a memory (or storage device or storage medium) 35c of a plurality of receiving channels. A phasing adder 35d to perform and another data generation unit 35e for digitally processing the generated image signal are provided. For example, the other data generation unit 35e generates image display data, calculates a displacement based on the Doppler method, calculates a temperature, and the like by a high-order calculation. Perform analysis.

  By performing this phasing addition process at each position in the region of interest, dynamic focusing is performed. Originally, dynamic focusing was a term used in the range direction received at the effective aperture, but in fact, it is not limited to the reception digital beamforming performed by the present invention. The receiving unit 32 in the embodiment of the present invention shown in FIG. 2 is a high-precision digital that does not require high-speed and approximation processing that is different from the above-described calculation processing represented by its name in the calculation process for performing phasing addition (DAS) processing Beam forming is performed. Therefore, in the embodiment of the present invention, the digital signal processing unit 33 shown in FIG. 2 is used instead of the phasing adder 35d shown in FIG. In the digital signal processing unit 33, other data as described above may be generated based on the image signal. For example, the digital signal processing unit 33 performs a beam forming process on the reception signal generated by the reception unit such as the transducer 20 to perform lateral modulation, thereby generating a multidimensional reception signal. Hilbert transform processing is performed on the received multidimensional received signal.

  A normal phasing adder can be similarly realized by the digital signal processing unit 33 in the embodiment of the present invention. In particular, the feature of the receiving unit 32 in the embodiment of the present invention is high speed and high accuracy. In order to realize the processing, normally, the received signal generated in the receiving aperture element 20a is level-adjusted or analog-filtered by analog amplification or attenuation (programmable and operates under the frequency characteristics and parameters set through the control unit 34. In addition to ensuring signal strength and reducing noise using analog devices such as), the advantage of analog signal processing being faster than digital signal processing is linear or particularly non-linear as required Through the effective use of devices that perform analog signal processing and through those processing The resulting signal is AD converted and stored in the fast memory (or storage device or storage medium) 32c of reading and writing digital signal obtained as a result.

  Further, as the digital signal processing unit 33 to be mounted, a device or a computer having general-purpose calculation processing capability, a PLD (Programmable Logic Device), an FPGA (Field-Programmable Gate Array), a DSP (Digital Signal Processor), a GPU (Graphical Processing). Unit) or a microprocessor or the like, or a dedicated computer, a dedicated digital circuit, or a dedicated device is used, and the digital wave signal processing of the present invention is performed on the stored digital signal. Applied.

  It is important that these analog devices, AD converter 32b, memory (or storage device or storage medium) 32c, and device responsible for digital signal processing unit 33 (multicore, etc.) have high performance. The number of communications, communication line capacity, wiring, or broadband wireless communication is important. In particular, in the present invention, when these functional devices are properly mounted on a single chip or substrate (when removable) In addition, they may be directly mounted on a single chip or substrate (including stacked layers). Parallel processing may be performed.

  When the device is non-detachable, it is possible to obtain much higher security performance than the security obtained under normal program control when the computer also serves as the control unit 34. On the other hand, the current law will require more disclosure of processing details. The digital signal processing unit 33 may also serve as a control unit 34 that sends command signals to other units and controls them.

  In the receiving unit 32 implemented in the present invention, a trigger signal (that is, starting AD conversion) that causes the AD converter 32b to start sampling (AD conversion) of the reception signal generated in the reception transducer (or reception sensor) 20 is performed. The acquisition start command signal (starting to store the digital signal in the memory (or storage device or storage medium) 32c) is the same as the trigger signal used in the normal receiving unit. For example, any command signal generated by the control unit 34 may be used so that the transmitter 31a generates a transmission signal to the transmission aperture element 10a to be driven. When receiving a wave, a command signal for the element to be driven first, a command signal for the element to be driven last, or a command signal for driving another element is used. AD conversion may be started by applying a digital delay.

  These command signals may be generated based on a command signal for starting beam forming for one frame. In other words, the number of occurrences of the transmission trigger signal is counted, and the hardware or the number that has reached a predetermined number or a programmable parameter such as input and set from the input device 40 or the like as appropriate is reached. When confirmed in the control program, a command signal may be generated that initiates the generation of a new frame. The number may be installed through various media such as CD-ROM, floppy disk, or MO, as well as other parameters. There are cases where the program can be started and interactively selected from the input device 40, and there are various cases such as inputting a numerical value directly, or reading and setting a file in which data is recorded. The number can also be determined using a dip switch or the like. When the number of reception delay patterns is not required to be large, a signal obtained by multiplying a received signal by an installed analog delay pattern may be AD converted.

  In order to realize high-speed reception dynamic focusing, a normal high-speed operation is performed without using a method based on the Nyquist theorem by applying a product of a complex exponential function to a signal in the frequency domain, which is a past invention of the inventors of the present application. When the reception digital delay is multiplied, an error determined by the AD conversion sampling interval is generated. Therefore, the sampling frequency of the AD converter 32b is sufficiently increased at a high cost, or by a highly accurate digital delay (phase rotation processing). There was no choice but to do low-speed beamforming. On the other hand, according to the present invention, if the received signal is digitally sampled in synchronism as described above, high-speed received digital beamforming can be performed without causing such an approximation error. Such reception digital beamforming is much faster than the method of calculating the product of complex exponential functions in the frequency domain which is the past invention of the inventors of the present application.

  In the present invention as well, normally, the number of channels for transmitting a signal received by the reception aperture element 20a used for performing one beamforming to the reception unit 32 is the number of reception channels. In that respect, the receiving unit 32 is as follows, and there are various types of receiving channels. That is, in order to apply different delays to the signals generated in the plurality of reception aperture elements 20a when performing normal beam forming once, the reception unit 32 is equipped with an analog or digital delay pattern as described above. A delay pattern that realizes a reception focus position, a steering direction, or the like that can be selected by the operator using the input device 40 may be used.

  These patterns are programmable, and patterns to be used and selectable patterns may be installed through various media such as a CD-ROM, floppy disk, or MO depending on the purpose. In some cases, a program can be started and a pattern can be selected interactively from the input device 40, a delay (pattern) value can be directly input, or a file in which data is recorded can be read and set. There are cases. In particular, in the case of analog delay, the delay value to be used may be changed in an analog or digital manner, or the delay circuit or pattern itself may be replaced with another one or switched separately. Sometimes.

  When the reception delay is digital, the reception signal stored in the memory (or storage device or storage medium) 32c of each reception channel is read and phased (added). In the apparatus of this embodiment, the digital signal processing unit 33 delays the digital reception signal, passes the digital reception signal through the delay device of the digital circuit, or the AD converter 32b and the memory (or storage device or It is possible to apply a delay to the command signal to start loading from the control unit 34 for turning on the storage medium 32c. Therefore, the digital delay can be applied at an arbitrary position or in the control unit 34 as long as it is after the inside of the AD converter 32b.

  In the case of an analog delay, a delay can be applied at an arbitrary position or in the control unit 34 as long as a reception signal is generated in the reception aperture element 20a. When the analog delay pattern is used, the receiver 32a can receive the reception signals of a plurality of aperture elements with at least one device. Therefore, in the storage destination of the reception signal, the reception signal of each reception opening may be stored at a position corresponding to the reception delay, or the reception delay may not be applied at all. The digital signal processing unit 33 may perform digital wave signal processing described later (the digital signal processing unit 33 may also perform normal phasing addition processing).

  A pattern may be selected by switching between an analog circuit or an analog device, or a digital circuit or a digital device. In addition, the delays of these delay devices may be programmable under the control of the control unit 34, or may be programmable through installation, input settings, or the like. Further, a delay device may be provided in the control unit 34. When the control unit 34 is configured by a computer or the like as described above, a command signal delayed by software control is controlled. It may be output directly from the unit 34.

  The control unit 34 and the digital delay may be a device or a computer having general-purpose calculation processing capability, a PLD, FPGA, DSP, GPU, or a microprocessor, or a dedicated digital circuit or a dedicated device. They are desirably high performance (such as multi-core) and may also be responsible for analog devices, AD converter 32b, memory 32c, and / or digital signal processing unit 33 that performs transmit or receive beamforming processing.

  In addition, the number of communication between devices, communication line capacity, wiring, or broadband wireless communication is important. In particular, in the present invention, when these functional devices are appropriately mounted on one chip or substrate ( Detachable). In addition, they may be directly mounted on one chip or substrate (including stacking). Parallel processing may be performed. If the device is non-detachable, when the computer also serves as the control unit 34, it is possible to obtain much higher security performance than security obtained under normal program control. On the other hand, the current law will require more disclosure of processing details. Some control software and delay values are directly coded or input, and others are installed. The method of applying the digital delay is not limited to these.

  In the present embodiment, a trigger signal (command signal) for instructing the start of AD conversion based on the trigger signal sent from the control unit 34 (FIG. 2) of the apparatus body 30 is the AD of each reception channel. It is supplied to the converter 32b. In accordance with this command signal, AD conversion of the received analog signal of each channel and storage of the digitized signal in the memory (or storage device or storage medium) 32c are started. The transmission unit 31, the reception unit 32, and the digital signal processing unit 33 are controlled by the control unit 34 until the reception signal for one frame is completely stored, or the transmission aperture position, the transmission effective aperture width, or While changing the transmission steering direction, etc., every time a wave or beam is transmitted, the process from transmission to storing the digital signal is repeated while changing the reception aperture position, reception effective aperture width, or reception steering direction. Each time a received signal for one frame is stored, a digital wave signal processing method used in the present invention, that is, a digital beam forming method is applied to the received signal group to generate a coherent signal.

  Therefore, even if the device according to the present invention is equipped with the above-mentioned analog or digital delay, it is not necessarily used as a delay for beam forming, and it saves memory, a storage device, or a storage medium. In order to effectively use the data and shorten the access time, it may be used to delay the timing of starting AD conversion of received signals and storing them in the memory (or storage device or storage medium) 32c. The reception delay in beam forming is always digital wave signal processing performed by the digital signal processing unit 33, and in the present invention, the significance of saving and shortening of access time is significant. Also, physical beam forming at the time of transmission (for example, physical processing using a computer or a dedicated device, which is different from that performed in software beam forming using a computer or a dedicated device). When performing classical aperture synthesis that does not perform focusing, steering, apodization processing, etc. that may be performed at the time of reception or reception, the transmission delay is the same as the reception delay in digital wave signal processing. Multiply with timing.

  From the above, in the present invention, the receiving unit 32 always has an independent analog or digital delay, receiver 32a, AD converter 32b, and memory (or storage device or storage medium) in each reception channel. 32c, and if necessary, level adjustment by analog amplification or attenuation, an analog filter, and other analog arithmetic devices. That is, in the apparatus of the present invention, when this digital delay is performed by the reception delay, an error that depends on the clock frequency does not occur as in the case of the analog delay unless a delay for beam forming is applied.

  In other words, an error that depends on the clock frequency always occurs in the digital delay of transmission, so it is necessary to reduce the error by using a high clock frequency at a high cost, but that is not necessary in the digital delay of reception. . If a digital delay is used for the reception delay, the accuracy is not lowered and the freedom of setting the delay pattern is high. If an analog delay is used for the transmission delay, the accuracy is high and the clock frequency can be lowered. The analog delay can be changed in an analog manner or can be made digitally programmable. However, the analog delay has a lower degree of freedom than the digital delay, and when the cost is reduced, the delay pattern mounted as an analog circuit may be used by switching or may be used by replacing it with an appropriate one. When a high degree of freedom is required for setting the transmission delay pattern, it is necessary to operate the digital delay with a high clock.

  Hereinafter, a coherent signal generated by the beam forming itself of the present invention is referred to as an image signal. The reception effective aperture elements and their positions are controlled in the same manner as the transmission effective aperture elements (details will be described later). The digital beam forming is not always performed every time a reception signal for one frame is stored. For example, the digital beam forming is input from the input device 40 or the like as appropriate, for example, an effective aperture width or a predetermined number other than that. The number of hardware channels, such as the number of hardware signals that are set, may be set at every timing when a number of received signals that may be programmable parameters are stored (there are various input means as described above). In addition, an image signal generated by partial beamforming may be combined into an image signal of one frame.

  In that case, the received signals processed at consecutive positions in the scanning direction may be overlapped. When these received signals are combined, simple overlaying (overlapping in the frequency domain) is performed. May be combined and inverse Fourier transformed), suitably weighted and superimposed, or simply connected. The number of stored reception signals can be confirmed in hardware or a control program by counting a trigger signal (command signal received from the control unit 34) for receiving the reception signal. The command signal for starting the digital wave signal processing of one frame generated by the control unit 34 for each frame can be confirmed in the same manner, and the image signal of one frame is appropriately generated continuously.

  The maximum frame rate that can be achieved depends on the form of beam forming to be performed, and is basically determined by the wave propagation speed. However, in actual applications, it is the time required to digitally calculate one frame of image signal. Determined. Therefore, it is useful to perform the process of generating the image signal partially by parallel processing. In addition, as described above, the inventor of the present application has developed multidirectional aperture surface synthesis, generates a reception beam at a plurality of positions and a reception beam in a plurality of directions for one transmission beam, and performs multifocus. It is useful to implement, and in order to implement them at high speed, it is useful to perform parallel processing. In any case, on the basis of performing the above transmission and reception, a reception signal for beam forming for one frame or a part thereof may be stored, and digital wave signal processing in the present invention described in detail later may be performed. In addition, when the image signal cannot be generated in real time, the frame rate may be lowered or may be processed offline.

  The reception apodization weights the reception signal in the reception channel of each aperture element and may be variable with respect to the range direction. It is not impossible to make it variable in analog, but it is easy to make it digitally variable. In a normal receiving unit, when performing phasing addition, it is carried out at each position, each range position, etc. and is often variable, but in the apparatus according to the present invention, it is carried out by the digital signal processing unit 33. become. On the other hand, although it is rare that non-variable apodization is performed, in that case, apodization is performed when performing level adjustment by analog amplification or attenuation on the reception signal generated by the aperture element.

  Although it has a different meaning from apodization, at least level calibration may be performed based on calibration data of the conversion efficiency (conversion capability) of the driving signal of the aperture element into a wave, and apodization is also performed at the same time as level calibration. May be. The processing may be aimed at, or the dynamic range of the waveform of the received analog signal may be nonlinearly expanded or compressed, and other analog devices such as nonlinear elements are used in each reception channel. Sometimes. The analog devices used, including those amplifiers and the like, may be programmable, and the setting method may take various forms. Like other parameters, it may be set directly using various input devices. Usually, the delay and the apodization are implemented in the receiving unit 32 in the same or different hierarchical levels in the same or different forms, but usually in a phasing adder, in the present invention. Can be implemented in the digital signal processing unit 33 with a high degree of freedom.

  The reception channel of each aperture element in the reception effective aperture is switched through a switching device such as a shift register or a multiplexer, and the region of interest may be scanned while performing beam forming using the effective aperture at another position. Further, the delay value of the delay element may be variable, and the delay pattern (delay element group) may be switched. Further, steering in a plurality of directions may be performed at one effective opening, and steering may be performed in a plurality of directions while changing the opening position and effective opening width as appropriate. The access time may be shortened by saving the device or the storage medium. The effect of storing frequently used data in a small memory that is easy to read and write as appropriate is also great.

  In the present invention, the saving and the shortening of the access time are significant. The apodization element group constituting the apodization pattern may be switched. The beam shape may be adjusted depending on the opening position, the range direction, and the steering direction. In detail, it means that the receiving element with zero apodization value is not active but is off, and the apodization also serves as a switch for the effective element and can determine the effective aperture width (apodization in the direction of the aperture element array). If the function is a rectangular window, the switch is on. If it is not a constant value, the switch is on). Therefore, the apodization element is of the same level as the switch.

In addition, when the delay pattern or the apodization pattern includes a plurality of patterns or is programmable, propagation is performed in the digital signal processing unit 33 in the apparatus main body 30 based on the response from the transmission target or the result of beam forming. Wave attenuation and scattering (forward scattering, backscattering, etc.), transmission, reflection, refraction, impedance, or sound velocity frequency dispersion and spatial distribution in the process medium are calculated, transmitted from each aperture, and received at each aperture The wave delay and intensity, the steering direction of the beam and wavefront, or the apodization pattern may be optimized. Instead of using the instantaneous frequency or instantaneous phase of the received wave for the transmitted wave such as a pulse wave, the frequency characteristic of those media characteristics is to divide the frequency response of the received wave at each frequency by the frequency response of the transmitted wave. It is effective to obtain the spatio-temporal distribution of the characteristics of the medium by applying inverse Fourier transform to it. At that time, as described in paragraphs 0363 and 0371, it is effective to correct the waveform distortion generated in the observation apparatus (device) and perform processing. As in the case of super-resolution using division, regularization, Wiener filtering, and the like are effective because noise is increased and a large error occurs when divided by a small spectral component. Maximum likelihood estimation is also effective, and MAP (maximum a posteriori) may be used in combination. They may also be integrated and fused. In some cases, echoes at the same location are acquired multiple times and processed. Also, similar to another super-resolution, conjugate of frequency response may be effective instead of dividing by frequency response. Various super-resolutions including those super-resolutions are also described herein. Even in the case of using the above instantaneous frequency and phase, and when performing various other imaging (for example, including reflection and transmission methods such as basic normal echo imaging, etc.) in the observation device (device) It is effective to process after correcting the generated waveform distortion.
In addition, instead of the frequency response of the transmitted wave, the same transmitted wave is used as a reference material (the simple one has a uniform propagation characteristic of the medium such as an irregular scatterer distribution, or a reflector or scatter provided at a representative position). For other elaborate things such as the body, it is possible to cancel the accumulation of changes in the wave spectrum caused by the characteristics of the medium during the propagation of a homogeneous medium, such as propagation speed, impedance, scattering, attenuation, etc., with frequency dependence It is also effective to divide by the frequency response of the received wave obtained by applying to the non-homogeneous, etc.), estimate the maximum likelihood, or multiply the conjugate of the frequency response. (It is an application of a linear system).
The above calculation may be performed for the entire region of interest at once, locally or locally depending on the spatial heterogeneity of the point spread function represented by the propagation characteristics of the wave itself. It may be performed every time (the former is easy to calculate). The latter local processing has precedents in super-resolution processing (Non-Patent Documents 35 and 36), and the point spread observed locally for a reference substance (irregular distribution of scatterers or scatterers at representative positions) is targeted. In some cases, the frequency response of the function is used to divide. In the other super-resolution processing, it is equally effective to perform the entire region of interest at once or to be performed locally.

  In classical aperture plane synthesis, all receiving elements may have a receiving channel including the receiver 32a. In general, aperture synthesis is performed simultaneously with reception apodization in the phasing adder. In the present invention, aperture synthesis may be performed simultaneously with reception apodization in the digital signal processing unit 33.

  In addition, the ultrasonic frequency and bandwidth as parameters in the transmission unit 31 and the reception unit 32, code, delay pattern, apodization pattern, analog device for signal processing, effective aperture width, focus position, steering direction, and The number of transmissions and receptions necessary for performing beamforming is installed on each functional device in the unit through various media such as CD-ROM, DVD, floppy disk, or MO. Sometimes.

  In some cases, the program can be started to select them interactively from the input device 40, or numerical values can be directly input, they can be selected on the operation panel of the input device 40, or other files in which data is recorded can be selected. There are various cases, such as when reading and setting. It is also possible to define them using a dip switch or the like. It may be due to unit replacement or switching. In addition, when a measurement target is selected or a transducer to be used is attached to the apparatus, the apparatus may be recognized and automatically operate under recommended parameters. Subsequent adjustments are possible. In addition, if a functional device of a normal receiving unit is mounted, an image image obtained by using the apparatus of the present invention and an image image obtained by processing including interpolation interpolation through normal phasing addition as appropriate. Can be compared.

<Input device>
The input device 40 is used, for example, for setting various parameter values as described above. Examples of the input device 40 include, but are not limited to, a keyboard, a mouse, a button, a panel switch, a touch command screen, a foot switch, or a trackball. Install operating system (OS) and device software from a storage medium such as general-purpose memory, USB memory, hard disk, flexible disk, CD-ROM, DVD-ROM, floppy disk, or MO, upgrade, various parameters The value may be set or updated. The input device 40 includes various devices that can read data from the storage medium, or the input device 40 includes an interface, and various devices are mounted and used as necessary.

  The input device 40 is used not only for setting parameters of various operation modes of the device according to the present embodiment, but also for controlling and switching the operation modes. When the operator is a human, the input device 40 can be a so-called man-machine interface, but is not necessarily controlled by a human. As described above, parameter values, data, or control signals are received from other devices through various standards and connectors, or are received through wired or wireless communication (that is, communication devices having at least a reception function). The effect is obtained, and the present invention is not limited to the above example. A dedicated or regular network may be used.

  The input data is stored in a memory, a storage device, or a storage medium inside or outside the apparatus, and functional devices in the apparatus operate with reference to the stored data. Alternatively, when the functional device in the apparatus is equipped with a dedicated memory, data is written to it and the operation setting is determined by software, updated, or hardware is set, Or it may be changed. In some cases, the calculation function in the apparatus operates, and optimized setting parameters are calculated and used based on the input data, sometimes taking into account the resources of the apparatus. The operating mode may be determined by a command. In addition, the wave to be measured (wave type and characteristics, intensity, frequency, bandwidth, sign, etc.), the object to be propagated and the medium (propagation speed, physical property value related to the wave, attenuation, forward scattering, backscattering, Additional information regarding transmission, reflection, refraction, etc., or their frequency dispersion, etc.) may be provided and the received signal may be appropriately analog or digitally processed.

<Output device>
A typical output device 50 is a display device. The display device not only displays the generated image signal, but also displays various results measured based on the image signal as numerical values, images, and the like. Used to display. The image signal is converted (scan converted) into an image display or moving image or still image format by calculation processing, but a graphic accelerator may be used. A luminance image (gray image) or a color image may be displayed, and the meaning represented by the luminance or color may be displayed on a scale (bar) or logo. In addition, the result may be displayed as a bird's eye view or a graph, and the method of displaying the result is not limited to them.

  When the result is displayed, various parameter values and patterns (names) when the operation mode is operating may be appropriately displayed as a logo or a character together with each operation mode. In addition, supplementary information and various data related to the measurement target input from the operator or another device may be displayed. In addition, the display device may be used to display a GUI (Graphical User Interface) used when setting each parameter value or pattern using the input device 40, and uses a touch command screen. This is also used when an arbitrary position or range of an image to be rendered is designated and displayed in an enlarged manner or various numerical values are displayed, and may serve as one end of the input device 40.

  As the display device, various devices such as a device using a CRT, a liquid crystal, or an LED are used. However, the display device is not limited to such as a dedicated three-dimensional display device. Also, the output data is not necessarily used by human being directly interpreted or interpreted, but the device body (computer) understands the output data based on predetermined calibration data and calculation and displays the result. In some cases (for example, understanding the composition and structure of the measurement object from the spectrum analysis of the received signal), the output data is output to another device and interpreted by the other device, and the same device (for example, a robot). Or another device may apply the output data.

  One device may receive a plurality of types of waves to generate image signals, and data mining and fusion may be performed, or another device may be used to perform that type of processing. is there. The characteristics (intensity, frequency, bandwidth, code, etc.) of the generated image signal may be analyzed. As described above, data obtained by the apparatus according to the present embodiment may be used in another apparatus, and a communication device having at least a transmission function may be one of the output apparatuses 50 in practice. A dedicated or regular network may be used.

<Storage device>
The generated image signal and various results (numerical values, images, etc.) measured based on the image signal are stored in a memory, a storage device, or a storage medium inside or outside the device that also becomes the output device 50. Here, they are distinguished from display devices as “storage devices”. An external storage device 60 is also shown in FIG. When storing an image signal, an operation mode, a setting parameter value, supplementary information about an object input from an operator or another device, or various data may be stored together with the image signal. As the storage device, general-purpose or special memory, USB memory, hard disk, flexible disk, CD-R (W), DVD-R (W), video recorder, image data capturing device, or the like is used. The device is not limited to them. The storage device is appropriately used in accordance with the application, including the amount of data to be stored and the time for writing and reading.

  Although image signals and other data stored in the past may be read out from the storage device and played back, the main point is that the storage device is important for storing the OS, device software, or setting parameters. It is. Each functional device may have a dedicated storage device. A removable storage device may be used in other devices.

  The apparatus main body 30 reads out the image signal stored in the storage device, performs high-order digital signal processing, and re-synthesizes the image signal (frequency modulation or broadening by linear processing or non-linear processing, multi-focus, etc.), Perform various measurements such as image processing of image signals (super-resolution, enhancement, smoothing, separation, extraction, CG conversion, etc.), displacement and deformation of the object, and other various temporal changes, etc. Measurement results may be output and displayed on the display device.

  The stored measurement results include wave attenuation and scattering (forward scattering, backscattering, etc.), transmission, reflection, and refraction, which are read out and optimized for various parameters that generate image signals. In some cases, it is used for storage and stored in a storage device. The optimization is performed by a calculation function provided in the control unit 34 or the digital signal processing unit 33.

<Control unit>
The control unit 34 controls the operation of the entire apparatus. The control unit 34 is composed of various computers, a dedicated digital circuit, and the like, and may also serve as the digital signal processing unit 33. Basically, the control unit 34 performs wave transmission / reception and wave digital signal processing based on various control programs and various data read from the storage device in response to various requests input via the input device 40. The transmission unit 31, the reception unit 32, and the digital signal processing unit 33 are controlled so as to generate an image signal.

  When the control unit 34 is configured by a dedicated digital circuit, the parameter may be variable, but there may be a case where only a fixed operation can be realized including switching the operation by switching. When a computer is used as the control unit 34, the degree of freedom is high, including when upgrading. The basics of the control unit 34 are the number of transmission and reception aperture elements (the number of each channel), the number of beams to be generated, the number of frames (some operations will continue unless specified and stopped), the frame rate, etc. In response to this, the transmission unit 31 and the reception unit 32 are provided with repetition frequency, transmission / reception position information, and the like to perform scanning control and image signal generation control. Also controls. In addition, various interfaces are provided, and various devices may be used in conjunction with each other.

  The apparatus according to the present embodiment may be used as one of devices such as a general network and a sensor network, and may be controlled by a control device of the network system, and control for controlling the network device. It may be used as a device or a control device that controls a locally configured network. An interface for this purpose may be provided.

<Beam forming method>
Next, useful high-speed through digital Fourier transform in the case of using a plurality of transmission / reception aperture elements (including those in the form of an array) implemented in the digital signal processing unit 33 of the apparatus main body 30 shown in FIG. A digital beam forming method will be described. In digital signal processing, intermediate data generated in the calculation process or data to be used repeatedly may be stored in a storage device or a built-in memory as appropriate, and when generating a plurality of image signals in the same phase. However, the storage device is used efficiently. Small-sized memory may come in handy.

  The generated image signal may be displayed as a moving image or a still image on the output device 50 such as a display device, or may be stored in the external storage device 60 using a recording medium such as a hard disk. In the case where the digital signal processing unit 33 is a computer, various languages can be used and the assembler is useful. In particular, when the computer is operated under a high-level language program such as C language or Fortran. In some cases, optimization and parallel processing are performed at the time of compilation to realize high-speed computation. A general-purpose one such as Matlab, various control software, or a graphic interface may be used, or a special one may be used.

  In the following, as an example, a beam forming method used in the apparatus of the present invention will be described through the case where the wave is an ultrasonic wave. The beam forming methods that can be used in the present embodiment are the following methods (1) to (7). In the method (7), in addition to various beam forming methods, the digital signal processing unit 33 generates the beam forming method. Disclose representative observation data.

  Method (1) is an interpolation that has been required so far in performing wave number matching in Fourier space in plane beam transmission and / or reception beamforming at the time of reception including the case where the transmission direction is deflected (steered). This method does not require approximation processing. Method (1) is an invention in which wave number matching in the depth direction and the transverse direction is performed by dividing a complex exponential function related to the cosine and sine of the deflection angle and multiplying the received signal by the wave number matching in the case of performing deflection. In addition, the measurement results are improved in accuracy as in the case of the classical monostatic type aperture plane synthesis. Furthermore, as a method (2), high-speed digital processing of deflection dynamic focusing by monostatic aperture surface synthesis is disclosed.

  Furthermore, as a method (3), a high-speed digital process of multistatic aperture surface synthesis is disclosed. In the digital monostatic type aperture surface synthesis that performs deflection, the centroid (center) or instantaneous frequency of the multidimensional spectrum of the generated image signal is ideally expressed using the deflection angle and the carrier frequency (described later). As in the method (1), the wave number matching is performed so that the wave vector becomes the component of the carrier frequency multiplied by the sine and cosine of the deflection angle. Can be realized with accuracy. On the other hand, multi-static aperture surface synthesis generates echo data frames including echo signals received at the same position of a plurality of reception positions with respect to the transmission position, as many as the number of receiving elements, and each echo is generated in the frequency domain. The data frame is subjected to the above-mentioned monostatic type digital aperture synthesis processing, and the result of superimposing these processing results is subjected to inverse Fourier transform to achieve high accuracy. As a result, in the method (3), echo data can be generated by digital aperture plane synthesis processing equal to the number of channels of the reception aperture, and so-called low spatial resolution image signal frames are generated and superimposed to generate a high spatial resolution image signal. This is much faster than the conventional DAS (Delay and Summation) method for generating a frame.

  Incidentally, in the DAS method, phasing is realized by delaying the received signal at high speed with interpolation approximation processing in the spatial domain and by delaying in the frequency domain with high accuracy ( Inventor of the present application, the received signal is summed in the spatial domain. The former has high speed but low accuracy, and the latter has high accuracy but extremely low speed.

  As a method (4), a method of performing digital dynamic focus reception at the time of fixed transmission focus with high accuracy based on the beam forming of the method (1) and the method (3) is disclosed. As method (5), echo data transmitted / received in the polar coordinate system is processed through Jacobi calculation for high precision display without interpolation approximation processing, for convex, sector scan, or IVUS applications. Disclose that echo data can be generated directly in the Cartesian coordinate system of the system.

  Further, as a method (6), it is disclosed that migration processing can be performed with high accuracy and high speed without performing interpolation approximation processing in the same manner using the present invention. All the beam forming processes of the method (1) to the method (5) can be performed based on the migration process. Finally, as a method (7), an application based on these beamforming is disclosed. With these, it is possible to demonstrate that any beam forming based on focusing and steering can be performed.

Method (1): Beam forming for plane wave transmission and / or plane wave reception (i) Echo signal (image signal) during plane wave transmission
FIG. 5 is a schematic diagram of transmission of a deflected plane wave. Plane wave transmission is a method of emitting a plane wave by radiating ultrasonic waves simultaneously from all elements in a linear array type transducer. When the wave number is k and a plane wave of the wave vector represented by the equation (0) is transmitted (x is the scanning direction, y is the depth direction), the position of the reception effective aperture element array is set to zero in the y coordinate. And the sound pressure field at the position (x, y) is expressed by the equation (1).

Here, A (k) is the frequency spectrum of the transmitted pulse and has the relationship of equation (2).

When there is a scatterer having a reflection coefficient f (x, y _i ) at a depth y = y _i , the echo signal from this scatterer is expressed by Equation (3).
The angular spectrum of this equation is expressed by equation (4).

If the frequency response of the probe is T (k), the angular spectrum at the aperture (y = 0) of the echo signal from depth y = y _i is expressed by equation (5) based on the principle of angular spectrum. Is done.

Therefore, by adding the angular spectra from the respective depths, the angular spectrum of the echo signal represented by equation (6) is obtained.

Therefore, by performing wave number matching as Expression (7) and Expression (8), an echo signal (image signal) can be expressed as Expression (9) by this inverse Fourier transform.

  Considering transmission and reception in reverse, arbitrary transmission beamforming (for example, deflection plane wave, deflected fixed focusing beam, steering dynamic focusing based on aperture synthesis, undeflected wave and beam, etc.) Is performed on the measurement object, it is possible to realize a situation in which the wave arriving from the measurement object is received as a plane wave having a deflection angle θ (including the case of zero degree). This idea has not been disclosed so far. In this way, it is possible to receive a wave at the same or different steering angle θ (zero or non-zero) when transmitting an arbitrary beam or arbitrary wave with an arbitrary steering angle (zero or non-zero). . Furthermore, an arbitrary wave source, an arbitrary transmit effective aperture array (for example, an aperture having the same shape as the receive effective aperture array or having an aperture in an arbitrary direction different from the receive effective aperture array, or existing at a different position) Alternatively, reception beam forming can be performed in a coordinate system defined by the reception aperture for any wave transmitted from the same physical aperture but from an effective aperture at a different position.

  In addition, when the plane wave is transmitted, the steering is physically performed at the deflection angle α (including the case of zero degree), and the steering of the deflection angle θ (including the case of zero degree) of the method (1) is softly performed. Then, the plane wave is steered at the deflection angle (α + θ) (the transmission deflection angle finally generated is an average thereof). This soft steering (deflection angle θ) can be considered to reinforce the physical transmission steering (deflection angle α) or to realize purely plane wave transmission steering in software, It can also be considered that the reception steering is performed with a plane wave.

  In the method (1), the plane wave is steered at the physical deflection angle α, the soft deflection angle θ, or both the deflection angles α + θ at the time of transmission, and the dynamic focusing is performed at the steering angle φ at the time of reception. In this case, the soft steering described in the method (2) may be performed, which will be described later (the finally generated deflection angle is an average of the transmission deflection angle and the reception deflection angle). In this case, the soft steering (deflection angle θ) can be considered to reinforce the physical transmission steering (deflection angle α) or to realize purely plane wave transmission steering in software. In addition to reception dynamic focusing (including the case where the deflection angle φ is zero degree), it can be considered that reception steering is performed by a plane wave in software.

  In these cases, software transmission and reception can be considered in reverse. The process is the same (equivalent) even if the software deflection plane wave transmission (including the case where the deflection angle is zero degree) and the reception deflection dynamic focusing (including the case where the deflection angle is zero degree) are interchanged. It is also possible to interpret the signal generated by the transmission beamforming as being physically received by a deflected plane wave (including a case where the deflection angle is zero degree) and beamformed. Normally, it is not reasonable to perform transmission dynamic focusing physically with or without deflection, but it can also be interpreted as having been physically received by a deflected plane wave.

  Also, using this method, arbitrary transmit beamforming (for example, deflection plane waves, deflected fixed focusing beams, steering dynamic focusing based on aperture synthesis, undeflected waves and beams, etc.) it can. That is, by the same processing using a plane wave for transmission, it is possible to handle an arbitrary wave or beam (for example, the above example) generated by physical beam forming. In other words, reception beam forming (such as dynamic focusing) can be performed regardless of what transmission is performed. It can also be processed at a time when a plurality of transmissions are performed. Further, in addition to the transmission deflection angle (including the case of zero degree), it is possible to apply a steering of plane wave or dynamic focusing (including the case where the steering angle is zero degree) in transmission or reception in software. (The finally generated deflection angle is the average of the transmission deflection angle and the reception deflection angle). Further, as described above, transmission and reception can be considered in reverse, and various combinations of beam forming are possible. Beam forming is performed in each of transmission and reception, and both transmission and reception may be subjected to plane wave processing in software. The same applies to three-dimensional beam forming using a two-dimensional array described later.

Based on the above theory, the calculation method disclosed by J.-y. Lu et al. (Non-Patent Documents 3 and 4) first performs fast two-dimensional Fourier transform on the received signal with respect to time and space, and R (k _x , k) is calculated, and then wave number matching is performed by equation (7) to perform high-speed two-dimensional inverse Fourier transform (also described in paragraph 0354). Wave number matching is performed through linear interpolation approximation or approximation with the nearest neighbor data itself, and it is required to oversample the received signal in order to obtain accuracy. A high-order interpolation approximation may be performed, or a sinc function may be used. In the case of three dimensions, high-speed three-dimensional Fourier transform and high-speed three-dimensional inverse Fourier transform are similarly used. One feature of the present invention is that wave number matching is performed without interpolation approximation. However, when applied to various beam forming as described in paragraphs 0192 to 0196, interpolation approximation processing is performed to perform approximation at high speed. It is also characterized by finding solutions.

(Ii) Calculation procedure of echo signal (image signal) at the time of transmission and / or reception of plane wave according to the present invention A case where a plane wave having a deflection angle θ is transmitted and / or received will be described below. In the present invention, wave number matching is performed in the lateral direction by multiplying the received signal by a complex exponential function (formula (9a)) before the Fourier transform of the received signal in space (lateral direction), and in the depth y direction. Is multiplied by the complex exponential function (formula (9c)) at the same time as the complex exponential function (formula (9b)) excluding the above-described horizontal matching processing is applied to have resolution in the depth y direction. . Of course, the deflection angle θ can be used not only at non-zero degrees but also at zero degrees. This process is not disclosed in prior art documents.

FIG. 6 is a flowchart showing digital signal processing during deflection plane wave transmission. The calculation procedure is as follows. First, in step S11, as shown in Expression (10), the received signal is Fourier transformed with respect to time t (FFT is good).
However, when ω is an angular frequency (angular frequency) and c is the speed of sound, the wave number k = ω / c. Thus, an analysis signal is obtained. Here, in accordance with the above description, a process is shown in which the sign of the core of the complex exponential function is positive as the Fourier transform, but the sign of the core of the complex exponential function is calculated as negative as in the normal Fourier transform. It is also possible. In any case, in the inverse Fourier transform to be calculated later, a complex exponential function whose sign is opposite to that at the time of the Fourier transform is always used (that is, the first and last conversion processes have the core sign of the complex exponential function reversed). It is sufficient that the inverse Fourier transform is generally performed first, and the Fourier transform generally referred to is finally performed, and the order may be reversed. The same applies to the other methods (2) to (7).

Next, in step S12, it performs a matching process with respect to the wave number _{k x} for deflecting, multiplied by equation (11) into equation (10), in step S13, Fourier transform (FFT regard lateral x received signal By doing so, equation (12) is obtained. For the calculation of the product of the result (10) of the fast Fourier transform with respect to time t and the complex exponential function (11), a dedicated fast Fourier transform that directly generates the calculation result is useful.
Incidentally, the result of equation (12) can also be obtained by direct calculation.

The received signal is decomposed into plane wave components by the two Fourier transforms. As described above, the angular spectrum that each plane wave creates at an arbitrary depth y is obtained by multiplying the phase by multiplying the equation (13).

Furthermore, in step S14, the matching process is simultaneously performed on the wave number ky by simultaneously multiplying the equation (14).

In step S15, an angular spectrum of each depth y is calculated. That is, the equation (16) is obtained by multiplying the equation (15).

The sound pressure field generated by each plane wave component at the depth y is obtained as an equation (17) by performing an inverse Fourier transform (IFFT) on the lateral direction x.
An image signal is obtained by adding a plurality of wave number k components (or frequency components).
Here, the integration of the wave number k (or frequency) and the spatial frequency kx can be changed in order. Therefore, adding the wavenumber k component of the angular spectrum in step S16, even if the inverse Fourier transform with respect to the transverse direction of the wave number _{k x} a (IFFT) in step S17, the image signal is obtained in step S18. In this case, calculation can be performed by one inverse Fourier transform, and the calculation is faster. The same applies to the other methods (1) to (6). The wave number matching for deflection is performed by the equations (11) and (14). Unlike the method of performing wave number matching through interpolation approximation in the frequency domain (Non-Patent Documents 3 and 4), the present invention does not perform approximation processing, and therefore can calculate with high accuracy.

In addition, both physically and mathematically, wave number matching can be performed during the first Fourier transform, and wave number matching can be performed during the last inverse Fourier transform. The same applies to the other methods (1) to (6). As described in paragraph 0199, in accordance with the above description, a process in which the core of the complex exponential function is positive as a Fourier transform is shown, but the sign of the complex exponential function is negative as in the normal Fourier transform. It is also possible to calculate. In any case, in the inverse Fourier transform to be calculated later, a complex exponential function whose sign is opposite to that at the time of the first Fourier transform is always used (that is, the first and last transformation processes are the core sign of the complex exponential function). Can be reversed, the first commonly referred inverse Fourier transform can be performed, and the last generally referred Fourier transform can be performed, and the order can be reversed. First, when performing wave number matching together in the first Fourier transform, the received signal r (x, y) (here, unlike the equation (10), the wave propagation time t (Instead, the depth distance y is used), the equation (11) is used to perform the Fourier transformation in the lateral direction x as in the equation (12), and the equation (13) is used for the Fourier transformation in the depth direction y. ) And Expression (15) expressed by using Expression (14), except that ksinθ is not corrected in Expression (15) because wave number matching is simultaneously performed in two directions.
(This is the result of applying the inverse Fourier transform, which is generally called). When the deflection angle θ is 0 degree, first, the one-dimensional Fourier transform may be performed in the lateral direction x, and the fast Fourier transform is effective (in general, when calculating as in the above formula, Inverse Fourier transform is applied). And in order to perform Fourier transform in the depth direction y and wave number matching for the calculated R ′ (kx, y),
And one-dimensional processing. It is faster than calculating each R ′ (kx, ky) according to equation (16 ′). Finally, the two-dimensional inverse Fourier transform in the x direction and the y direction is performed on the equation (16 ′) or the equation (16 ″) to obtain the image signal f (x, y). A one-dimensional inverse Fourier transform may be applied to each of the x direction and the y direction, and a fast inverse Fourier transform is effective (a general two-dimensional Fourier transform is applied when calculated as in the above equation). become).
Conversely, when performing wave number matching together in the last inverse Fourier transform, first, R (kx, k) is obtained by performing a two-dimensional Fourier transform on the received signal r (x, y), and finally In order to realize the equation (8) in the inverse Fourier transform, the equation (11) is used in the inverse Fourier transform in the lateral direction x, and the equations (13) and (14) are used in the inverse Fourier transform in the depth direction y. However, since wave number matching is simultaneously performed in two directions, correction of ksinθ is not necessary in Equation (15), and the image signal is
It is obtained. When the deflection angle θ is 0 degree, first, in order to perform inverse Fourier transform in the depth direction y and to perform wave number matching,
And then one-dimensional inverse Fourier transform is performed in the horizontal direction x, and fast inverse Fourier transform is effective. It is faster than calculating each f (x, y) according to equation (16 ′ ″).
Also, in these, in the wave number matching, the parts of the equations (11) and (14) are instead subjected to frequency modulation relating to kx and ky that are multiplied by the space-time signal using their complex exponential functions. You may add. In this case, first, it is sufficient to perform one-dimensional conversion in the horizontal direction x, and high-speed conversion is effective. It can be done at high speed.
The same applies to the three-dimensional case, and a three-dimensional Fourier transform and a three-dimensional inverse Fourier transform may be performed. The same applies to the other methods (1) to (6).

In addition, by using a two-dimensional aperture element array, an arbitrary wave is transmitted from a wave source located in an arbitrary direction toward the measurement object, and a wave arriving from the measurement object is received as a plane wave to receive a three-dimensional wave. In the case of performing digital signal processing, for example, a Cartesian orthogonal coordinate system (x, y, z) using the coordinate of the axial direction y determined by the direction of the aperture of the flat receiving aperture element array and the lateral directions x and z orthogonal thereto. ), When the zero-degree or non-zero-degree deflection angle formed by the plane wave receiving direction and the axial direction is expressed using the elevation angle θ and the azimuth angle φ, the Fourier transform is performed in the depth y direction and the lateral directions x and z. As in the case of performing the above-described two-dimensional wave digital signal processing, the three-dimensional Fourier transform R ′ (k _x , k, k _z ) of the received signal is
Is performed without interpolation approximation as follows. As in the case of the two-dimensional case, when applied to various beam forming as described in paragraphs 0192 to 0196, wave number matching is performed by interpolation approximation processing according to the equations (7 ′) and (8 ′) to perform high speed. In this case, F (k _x ', k _y ', k _z ') is subjected to three-dimensional inverse Fourier transform.

When interpolation approximation processing is not performed in wave number matching, first, a complex exponential function (C21) expressed by using wave number k of wave and imaginary unit i is multiplied by the Fourier transform of the received signal with respect to the axial direction y. Perform wave number matching in the horizontal direction x and z,
Furthermore, the product can be implemented on the angular spectrum obtained by Fourier transform with respect to the lateral directions x and z so as to have a resolution with respect to the axial direction y, excluding the effect of wave number matching performed in the lateral directions x and z. The wave number matching in the axial direction is performed by multiplying the complex exponential function (C22) at the same time as the complex exponential function (C23), where the transverse wavenumber is represented by k _x and k _z ,
By performing wave number matching without performing interpolation approximation processing, an image signal can be directly generated in a Cartesian coordinate system. That is, the sound pressure field generated by each plane wave component at the depth y is subjected to two-dimensional inverse Fourier transform (IFFT) with respect to the lateral directions x and z, and a plurality of wave number k components (or frequency components) are added. Thus, an image signal is obtained. Of course, it can also be used when the deflection angle is zero degrees (that is, the elevation angle θ and the azimuth angle φ are zero degrees) or at least one of the angles is zero degrees.

  In the above calculation, only signal components within the band determined by the transmission signal or within the band determined in consideration of the SN ratio of the reception signal are to be calculated. For example, when generating an analysis signal based on Expression (10), only a signal within a necessary band may be generated and stored (corresponding to downsampling). In the method or apparatus of the present invention, interpolation approximation processing is not performed when performing wave number matching, but by oversampling the echo signal in the depth direction or in the lateral direction, an effect that is robust against mixed noise is obtained. is there. The same applies to the other methods (1) to (6).

  Further, in the formulas (13) to (15), the formula (C22), and the formula (C23), by determining the position coordinate and range in the depth y direction to be calculated, the interval of the coordinates, etc., an arbitrary depth position or An image signal can be generated within an arbitrary depth range or at an arbitrary interval or an arbitrary density in the depth direction without performing an interpolation approximation process (regardless of the downsampling described in the previous paragraph). Up-sampling is possible, and the down-sampling is effective as long as the Nyquist theorem is satisfied, but the high-frequency signal component may be intentionally processed out of band (filtering out), as described in the previous paragraph. Regardless of whether or not downsampling is performed, downsampling is possible as long as the Nyquist theorem is satisfied). Further, in the inverse Fourier transform in the lateral direction such as the equation (17), by determining the position coordinate and range in the lateral x direction to be calculated (if necessary, the complex exponential function of the past invention of the inventor of the present application is determined. Analog space shifting by phase rotation using multiplication), image signals in any horizontal position and any horizontal range can be generated without performing interpolation approximation processing, and the inverse Fourier In the conversion, the band is narrowed in the horizontal direction excluding frequency coordinates in the high frequency band (spatial density is reduced), or is widened in the horizontal direction by zero padding of the angular spectrum (spatial density is increased). Thus, an image signal having an arbitrary interval or an arbitrary density in the horizontal direction can be generated without performing interpolation approximation.

  In this way, an image signal can be generated at any desired position, range, interval, and density. That is, the image signal can be generated at an interval shorter than the sampling interval of the received signal and at a pitch shorter than the interval between the receiving aperture elements. It is also possible to coarsen the image signal spacing in each direction (however, the Nyquist theorem must be satisfied). Similarly to the two-dimensional case (paragraph 0205), wave number matching can be performed at the first Fourier transform both physically and mathematically, and wave number matching can be performed at the last inverse Fourier transform. Is possible. Similarly, in the case where the steering is not performed, in the conversion process with wave number matching, the conversion process can be performed first in the x direction or the z direction in the horizontal direction, and finally the conversion process in the depth direction y can be performed. . Also, in these, in the wave number matching, the parts of the equations (C21) and (C23) may be added by performing frequency modulation by multiplying them by the space-time signal using their complex exponential function instead. good. In this case, first, it is sufficient to perform one-dimensional conversion in the x or z direction in the horizontal direction, and high-speed conversion is effective. Next, conversion in the depth direction y is performed using equation (C22) and the wave number is converted. Matching can be performed, and the speed can be increased. In addition, in order to increase the accuracy when performing wave number matching through interpolation approximation according to equations (7) and (8) or equations (7 ′) and (8 ′), at the expense of an increase in calculation amount, It needs to be processed under appropriate oversampling. In that case, it is necessary to be careful that the number of data of the Fourier transform increases, unlike the case where the signal at an arbitrary position can be selectively generated when the interpolation approximation process is not performed. The same applies to the other methods (1) to (6).

  In convex transducers, sector scans, or IVUS, when transmitting or receiving in the radius r direction of polar coordinates to generate a wide wave (cylindrical wave) in the angle θ direction (FIG. 7), or in other aperture shapes, In the case of performing the same beam forming (cylindrical wave) using a virtual source installed at the back (see FIGS. 8A (a) to (c), Patent Document 7, Non-Patent Document 8, etc.), in the above method, The Cartesian coordinates (x, y) can be read and processed as polar coordinates (r, θ), and an image signal can be generated at the polar coordinates (r, θ). The same applies to spherical waves in a spherical coordinate system. 8B (d) to (f), transmission or reception at an arbitrary distance position using a physical aperture element array represented by the polar coordinate system as described above or a physical aperture having an arbitrary aperture shape, Alternatively, both plane waves may be generated and beam forming may be performed in the same manner. This is equivalent to generating a virtual linear aperture array (or plane wave) at the distance position. If the distance position is set to zero, this corresponds to a case where a linear aperture array is virtually used. The distance position can be set not only in front of the physical aperture but also in the rear, and a virtual linear aperture array (or plane wave) can be generated at these positions. A virtual linear aperture array may be used as a virtual receiver instead of a virtual source, or may also serve as a virtual source.

  FIG. 7 is a schematic diagram of a case where a wide wave in the direction of the angle θ in polar coordinates (r, θ) is transmitted or received in the direction of the radius r (cylindrical wave transmission). 7A shows a cylindrical wave transmission using a convex aperture element array, and FIG. 7B shows a cylindrical wave transmission using a sector type aperture element array. (C) shows a cylindrical wave transmission using an IVUS (circular type) aperture element array. In FIG. 7B, an opening having an arc shape is shown, and a sector having a flat opening may be used to perform sector scanning. These apertures may also be used to generate a focus beam.

  FIG. 8A shows a case where a wide wave is transmitted in the direction of the angle θ of the polar coordinate system (r, θ) in the radius r direction using a virtual source installed behind a physical aperture having an arbitrary aperture shape (cylindrical wave transmission). ). 8A (a) shows a cylindrical wave transmission using a linear aperture element array, and FIG. 8A (b) shows a cylindrical wave transmission using a convex aperture element array. (C) has shown the cylindrical wave transmission using the other arbitrary aperture element array. The reception may be performed in the same way. 8B (d) to 8 (f) show a case where a transmission plane wave is generated at an arbitrary distance position using a physical aperture element array represented by a polar coordinate system or a physical aperture having an arbitrary aperture shape. (In the figure, a convex aperture element array is physically used). When the distance position is set to zero, this corresponds to a case where a linear aperture array is virtually used (FIG. 8B (d)). The distance position can be set not only behind the physical aperture (Fig. 8B (e)) but also forward (Fig. 8B (f)), and a virtual linear aperture array (or plane wave) is generated at those positions. You can also The reception may be performed in the same way. FIG. 8B (g) is a special case where, for example, when a linear array type transducer is physically used, a case where a cylindrical wave is generated using a virtual source behind a physical aperture is applied to an arbitrary distance position. It is a schematic diagram in the case of generating a plane wave or a linear array transducer virtually extending in the horizontal direction. The reception may be performed in the same way. The virtual linear array type transducer is not a virtual source but may be used as a virtual receiver or may also serve as a virtual source.

  In the case of transmission focus, there is a report in Non-Patent Document 6, and similarly, a result is obtained in polar coordinates (r, θ). For example, there is an effect that a wide FOV can be obtained. As a method different from Non-Patent Document 6, as a feature of the present invention, the present method (1) is used for these, and steering is also provided at the coordinate positions of these polar coordinate systems (r, θ). It is possible to generate a beam, and the same applies when the following methods (2) to (4) and (6) are used, in which Cartesian coordinates (x, y) are converted into polar coordinates (r, θ). You just need to replace it. However, when these beam forming operations are performed, it is necessary to perform an interpolation process to obtain a signal value at the coordinate position of the Cartesian coordinate system of the display system, and the phase rotation by the product of complex exponential functions in the frequency domain The exact interpolation process used is performed over time, or the interpolation approximation process is performed as a short-time process with an approximation error. The same applies to spherical coordinates.

  In these cases where beam forming is performed in the polar coordinate system, displacement measurement can also be performed. For example, a displacement component in the radius r direction or the angle θ direction can be measured, or the displacement component in both directions can be measured. A displacement vector can be measured. However, in order to obtain the measurement result at the coordinate position of the Cartesian coordinate system of the display system after measurement, it is necessary to perform interpolation processing, and the phase rotation by the product of the complex exponential function in the frequency domain is performed as in the case of interpolation of the echo signal. The exact interpolation process used is performed over time, or the interpolation approximation process is performed as a short-time process with an approximation error. The same applies to the spherical coordinate system.

  From the result of displacement measurement, strain, strain velocity (tensor), velocity (vector), acceleration (vector) are obtained by partial differential processing using a differential filter. Furthermore, mechanical characteristics (for example, bulk modulus, The shear modulus (for example, Non-Patent Document 7), other elastic modulus tensors of anisotropic media, and the like may be obtained through computation. When interpolation approximation is performed, it is often possible to shorten the calculation time by performing approximation processing and performing the calculation in the Cartesian coordinate system. However, calculation is performed in the polar coordinate system, and the result is obtained by interpolation approximation. Display, and the propagation of error can be reduced. That is, the error that occurs in the process after displacement measurement is only interpolation approximation when obtaining the last display data (a plurality of display data may be obtained from the same displacement data).

  As described above, the echo signal can be represented in a Cartesian coordinate system through the interpolation process, and displacement measurement and a series of measurements can be performed. An error occurs when the approximation process is performed in the interpolation process, but the total amount of calculation is small. Even when measurement based on other echo signal processing is performed, processing can be performed as described above. The same applies to three-dimensional beam forming using a two-dimensional array.

  In addition, with respect to any of the above, the same processing is possible for any orthogonal coordinate system other than the polar coordinate system.

  On the other hand, similarly, in a convex transducer, sector scan, or IVUS, a wide wave in the direction of angle θ in polar coordinates (r, θ) is transmitted or received in the direction of radius r (cylindrical wave) (FIG. 7). Then, using a virtual source installed behind a physical aperture of an arbitrary aperture shape, a wide wave in the direction of angle θ of the same polar coordinate system (r, θ) as in FIG. 7 is transmitted in the direction of radius r (cylindrical wave) In the case where the image signal is directly generated (see FIGS. 8A to 8C), the method of directly generating the image signal in Cartesian coordinates is the method (5), the method (5-1), and the method (5-1 ′), respectively. ) Etc. In addition, using a physical aperture element array represented by the polar coordinate system as described above or a physical aperture of an arbitrary aperture shape, a plane wave of transmission or reception or both is generated at an arbitrary distance position, and the beam is similarly generated. Forming may be performed, and an image signal may be generated in a Cartesian coordinate system (see FIGS. 8B to 8F). This is equivalent to generating a virtual linear aperture array (or plane wave) at the distance position. If the distance position is set to zero, this corresponds to a case where a linear aperture array is virtually used. The distance position can be set not only behind the physical aperture but also at the front, and a virtual linear aperture array (or plane wave) can be generated at these positions. A virtual linear aperture array may be used as a virtual receiver instead of a virtual source, or may also serve as a virtual source. Similarly, the beamforming method is described as method (5), methods (5-1), (5-1 ′), and the like. In these cases, echo signal imaging, displacement measurement, and the like can be performed consistently in the same Cartesian coordinate system. The same applies to the polar coordinate system. In such a case, it is also possible to convert echo signals and measurement values from a Cartesian coordinate system to a polar coordinate system through interpolation processing. The same applies to three-dimensional beam forming using a two-dimensional array. Transmission focusing may be performed.

  In addition, with respect to any of the above, the same processing is possible for any orthogonal coordinate system other than the polar coordinate system. In addition, as described above, the virtual source and the virtual receiver are not necessarily installed behind the physical aperture, but may be installed in front of the aperture, and can be installed arbitrarily regardless of the shape of the physical aperture. (Patent Literature 7, Non-Patent Literature 8). Thus, the present invention is not limited to the above. In addition, in wave number matching in such beam forming, interpolation approximation processing may be performed to obtain an approximate solution at high speed. In addition, any of the methods (1) to (7) may be similarly processed.

  Further, in the present methods (1) to (7), transmission, reception, or both apodization processes for a received signal can be performed at various timings because they are linear processes. In other words, it can be performed in hardware at the time of reception, or can be performed at various timings in software after reception. As described above, it may be physically apodized at the time of transmission (the same applies hereinafter).

  As a matter of course, when beam forming is performed by receiving a transmitted wave instead of an echo signal, the coordinate y is half of the round trip distance (expressed as ct / 2 using the propagation time t). Instead, it is the distance (ct) from the aperture element in the coordinate system determined by the reception aperture element array.

Next, a case where aperture surface synthesis is performed will be described. There are monostatic type and multistatic type for aperture plane synthesis.
Method (2): Monostatic Type Opening Surface Synthesis FIG. 9 is a schematic diagram of monostatic type opening surface synthesis. In the monostatic type aperture plane synthesis, an ultrasonic wave is emitted from one element of the array, and an echo is received by the element itself. Also in aperture synthesis, echo signals (image signals) can be calculated by performing wave number matching according to the procedure of FIG.

In monostatic aperture synthesis, since transmission and reception are performed by the same element, the propagation path of sound to the scatterer during transmission and the propagation path of reflected sound from the scatterer during reception are the same. Therefore, in the Cartesian Cartesian coordinate system in which the position of the reception effective aperture element array is zero in the axial y-coordinate, when steering is not performed (θ is zero degree), the wave number k is doubled as shown in the equation (18a). (When reflected wave, s = 2, the same applies hereinafter), and matching of the wave numbers represented by Expression (7) and Expression (8) is performed. In the case of a transmitted wave, k is used instead of wave number 2k (s = 1, the same applies hereinafter).

When the steering angle θ is non-zero, the wave number with respect to the wave vector (0, k ₀ ) having the wave number k ₀ (= ω ₀ / c) expressed using the carrier frequency ω ₀ of the ultrasonic signal. Beam forming is performed to shift the spectrum to generate an image signal having the vector (sk ₀ sin θ, sk ₀ cos θ) as the centroid (center) or instantaneous frequency of the multidimensional spectrum (see FIG. 10). That is, the wave number matching represented by Expression (18b) is performed in Expression (7) and Expression (8).

Signal processing is performed in the same manner as in the method (1), and in particular, wave number matching is performed by using ultrasonic waves instead of the complex exponential function (equation (9a)) in the previous stage of Fourier transforming the received signal with respect to space (lateral direction) Multiplying the complex exponential function (equation (19a)) expressed by using the carrier frequency ω _{0 of the} signal, first, it is carried out in the horizontal direction, and with respect to the depth y direction, in order to have resolution in the depth y direction, At the same time as the complex exponential function (formula (9b)) is multiplied by the complex exponential function (formula (19b)) excluding the horizontal matching process (formula (19a)), the complex exponential function (formula (9c)) Instead, a complex exponential function (formula (19c)) is multiplied. Of course, it can also be used when the deflection angle is zero. This process is not disclosed in prior art documents.

Further, for example, in the echo method (reflection method), the deflection angles of the transmission beam and the reception beam may be different. In this case, if the deflection angles of the transmission beam and the reception beam are θ _t and θ _r , In Expressions (7) and (8), wave number matching represented by Expression (18c) is performed under s = 2.

The signal processing is performed in the same manner as in the case where the deflection angles of the transmission beam and the reception beam are equal to each other. In particular, the wave number matching is performed in a complex exponential function (formula) in a stage before Fourier-transforming the reception signal with respect to space (lateral direction). (19a)) is multiplied by the complex exponential function (equation (19d)) expressed using the carrier frequency ω ₀ of the ultrasonic signal, and is first performed in the lateral direction, and the depth y direction is the depth. In order to have a resolution in the y direction, a complex exponential function (formula (19e)) excluding the horizontal matching process (formula (19d)) is multiplied instead of the complex exponential function (formula (19b)) and at the same time complex This is performed by multiplying the complex exponential function (formula (19f)) instead of the exponential function (formula (19c)). Of course, it can also be used when the deflection angles θ _t and θ _r are zero degrees. This process is also not disclosed in the prior art documents.

From the equations (19a) to (19c) and the equations (19d) to (19f), the two-dimensional Fourier transform R ′ (k _x , k) of the received signal is expressed as in equations (7) and (8). Thus, it is possible to realize a situation where each of the wave number matchings of the equations (18b) and (18c) is performed without interpolation approximation. On the other hand, there is a case where beam approximation is performed at high speed by performing an interpolation approximation process. In this case, F (k _x ', k _y ') is two-dimensionally inverse Fourier transformed. Similarly to the method (1), regarding the equations (18a) to (18c), wave number matching can be performed at the time of the first Fourier transform, both physically and mathematically, and the last inverse Fourier transform is performed. Sometimes wavenumber matching can also be performed (paragraph 0205 and paragraph 0210). However, in these cases, even during steering, in the conversion process involving wave number matching, the one-dimensional conversion process is first performed in the x direction, and then the one-dimensional conversion process in the y direction (wave number mapping in the x direction). Since this is a later process, the expression (19b) or the expression (19e) is used), and the speed can be increased. Also, in wave number matching, the expressions (19a) and (19c), (19d) and (19f) are replaced by kx multiplied by a spatio-temporal signal using their complex exponential function instead. You may implement the frequency modulation regarding ky. In addition, in the expressions (18b) and (18c), these approximation processes including the approximate wave number matching process corresponding to the expression (18a) when the deflection angle is set to zero are also disclosed in the prior art documents. Absent.

Further, in the case of performing three-dimensional wave digital signal processing using a two-dimensional aperture element array, for example, the axial direction y determined by the aperture direction of a flat receive aperture element array (the y of the position of the receive effective aperture element array) In Cartesian Cartesian coordinate system (x, y, z) using the coordinates of x and z in the transverse direction orthogonal to this) and zero or non-zero deflection formed by the direction and axis of the generated beam In the case where the angle is expressed using the elevation angle θ and the azimuth angle φ, the Fourier transform performs a three-dimensional Fourier transform on the depth y direction and the lateral directions x and z (the wave numbers in the axial direction y and the lateral directions x and z are calculated). The wave number regions (k _x , k _y , k _z ) are considered as k _y , k _x , and k _z , respectively. Similarly to the case of performing the above two-dimensional wave digital signal processing, the following processing is performed. The

First, for a wave vector (0, k ₀ , 0) having a wave number k ₀ (= ω ₀ / c) expressed using the wave carrier frequency ω ₀ , a wave vector (sk ₀ sinθcosφ, sk ₀ cosθ, The received signal is Fourier-transformed with respect to the axial direction y in order to perform dynamic focusing of transmission and reception with shifting of the spectrum to generate an image signal having sk ₀ sinθsinφ) as the centroid (center) or instantaneous frequency of the multidimensional spectrum. In addition, a parameter s having a value of 2 when the y-coordinate of the transmission aperture element is zero and a value of 1 when the y-coordinate of the transmission aperture element is non-zero, a centroid (center) frequency k _{0 of} the wave, and , By multiplying the complex exponential function (C41) expressed using the imaginary unit i, wave number matching in the horizontal direction x and z is performed,
Further, the product can be applied to an angular spectrum obtained by Fourier transform with respect to the lateral directions x and z so as to have a resolution with respect to the axial direction y, excluding the effect of wave number matching performed in the lateral directions x and z. Multiplying the exponential function (C42) and simultaneously performing the complex exponential function (C43) to perform wave number matching in the axial direction,
By performing wave number matching without performing interpolation approximation processing, an image signal can be directly generated in a Cartesian coordinate system. That is, the sound pressure field created by each plane wave component at the depth y is subjected to a two-dimensional inverse Fourier transform on the lateral directions x and z, and an image signal is obtained by adding a plurality of frequency k components. Of course, the calculation can be performed when the deflection angle is zero degrees (that is, the elevation angle θ and the azimuth angle φ are zero degrees) or at least one of the angles is zero degrees.

As a result, the following wave number matching (formula (C44)) is performed on the three-dimensional Fourier transform R ′ (k _x , k, k _z ) of the received signal as in formulas (7 ′) and (8 ′). Can realize the situation. Similarly to the two-dimensional case, wave number matching can be performed at the time of the first Fourier transform, and wave number matching can be performed at the time of the last inverse Fourier transform, both physically and mathematically with respect to the expression (C44). It is also possible (paragraph 0229). Even during steering, in the conversion process with wave number matching, first, the one-dimensional conversion process is performed in the x direction or the z direction, and finally the one dimensional conversion process in the y direction (after wave number mapping in the x direction and the z direction is performed). Since this is a process, the equations (C42) and (C43) can be used), and the processing speed can be increased. In addition, in the wave number matching, the components of the equations (C41) and (C43) may instead be subjected to frequency modulation that is multiplied by a spatio-temporal signal using their complex exponential functions (each kx And kz, ky frequency modulation). In the above, this wave number matching is performed without interpolation approximation. However, interpolation approximation processing may be performed at high speed according to equation (C44). In this case, F (k _x ′, k _y ', k _z ') is subjected to a three-dimensional inverse Fourier transform. This process is also not disclosed in the prior art documents.

Further, for example, in the echo method (reflection method), the deflection angles of the transmission beam and the reception beam may be different, and in this case, the respective deflection angles are (elevation angle, azimuth angle) = (θ _t , φ _t ) And (θ _r , φ _r ), the signal processing is performed in the same manner as in the case where the deflection angles of the transmission beam and the reception beam are equal under s = 2, The wave number matching is a complex exponential function (expressed by using the carrier frequency ω ₀ of the ultrasonic signal instead of the complex exponential function (formula (C41)) before the Fourier transform of the received signal with respect to space (lateral direction). Multiply (D41)) first, in the horizontal direction, with respect to the depth y direction, in order to have resolution in the depth y direction, the horizontal matching instead of the complex exponential function (formula (C42)) Complex exponential function excluding processing (formula (D41)) Simultaneously multiplying (formula (D42)), is performed by multiplying the complex exponential function instead of complex exponential function (Equation (C43)) (formula (D43)). Of course, it can also be used when the deflection angles of the transmission beam and the reception beam are zero degrees (that is, θ _t , φ _t , θ _r , and φ _r are zero degrees). This process is also not disclosed in the prior art documents.
In aperture synthesis in which both transmission and reception beam forming are performed in software, the same processing is performed even if beam transmission is performed by switching between transmission and reception.

As a result, the following wave number matching (formula (D44)) is performed on the three-dimensional Fourier transform R ′ (k _x , k, k _z ) of the received signal as in formulas (7 ′) and (8 ′). Can realize the situation. Similarly, with respect to the formula (D44), wave number matching can be performed at the time of the first Fourier transform, and wave number matching can be performed at the time of the last inverse Fourier transform, both physically and mathematically. (Paragraph 0232). Even during steering, in the conversion process with wave number matching, first, the one-dimensional conversion process is performed in the x direction or the z direction, and finally the one dimensional conversion process in the y direction (after wave number mapping in the x direction and the z direction is performed). Since this is a process, the equations (D42) and (D43) can be used) and the processing speed can be increased. In addition, in the wave number matching, instead of the parts of the equations (D41) and (D43), frequency modulation by multiplying by the space-time signal using their complex exponential functions may be performed (each kx And kz, ky frequency modulation). In the above, this wave number matching is performed without interpolation approximation. However, interpolation approximation processing may be performed at high speed according to equation (D44). In this case, F (k _x ′, k _y ', k _z ') is subjected to a three-dimensional inverse Fourier transform. This process is also not disclosed in the prior art documents.

Aperture synthesis can generate arbitrary beamforming using echo signals collected for aperture synthesis (not only in the monostatic method of this method (2) but also in the multistatic method of method (3)). However, an image signal can be generated even if the processing described in the methods (1) and (4) to (7) is performed on the data. In the plane wave processing of the method (1), the aperture plane synthesis processing can be performed by using a code. That is, an aperture plane synthesis signal can be obtained by decoding the received signal at the time of coded plane wave transmission.
Further, as described in the method (1), the steering can be performed in the dynamic focusing. In the method (1), the steering is physically performed at the deflection angle α (including the case of zero degree) when the plane wave is transmitted, and the steering of the deflection angle θ (including the case of zero degree) of the method (1) is performed. When applied, it can be interpreted that the plane wave is steered at the steering angle (α + θ) (the average steering angle is finally generated). Therefore, in the method (1), when a plane wave is steered at a deflection angle α, θ, or α + θ at the time of transmission, and dynamic focusing is performed at a steering angle φ (including a case of zero degree) at the time of reception, The reception steering described in the method (2) may be performed, and the finally generated steering angle is an average of the transmission deflection angle and the reception deflection angle. As described in the method (1), this soft plane wave steering (deflection angle θ) reinforces the physical transmission steering (deflection angle α) or purely performs plane wave transmission steering. In addition to reception dynamic focusing (including the case where the deflection angle φ is zero degree), it can be considered that reception steering is performed with a plane wave in software.

That is, in the two-dimensional case, (9a) and (19a), (9b) and (19b), (9c) and (19c) are respectively combined, (F41), (F42), (F43) Can be processed in the same way.

In the three-dimensional case, that is, when a plane wave is physically transmitted by steering with a deflection angle (α, β) of an elevation angle α and an azimuth angle β, or when at least one of the angles is zero degrees In case of software, steering a plane wave at a deflection angle (θ ₁ , φ ₁ ) and steering dynamic focusing at a deflection angle (θ ₂ , φ ₂ ) (at least one of the angles is zero degree) (Including cases), (G41), (G42), and (G43) are used in which (C21) and (C41), (C22) and (C42), (C23) and (C43) are respectively combined. The same processing can be performed, and finally, an average deflection angle of the transmission deflection angle and the reception deflection angle can be generated.

  As described in the method (1), the processing is the same even if the beam forming for software transmission and reception is interchanged, and is equivalent to the one performed for the interchanged beam forming. In other words, in these cases, soft transmission and reception beamforming can be considered in reverse, and any physical transmission beamforming (for example, deflection plane wave, deflected fixed focusing beam, aperture surface) In combination with steering dynamic focusing based on synthesis, undeflected waves and beams, etc., various combinations of beam forming are possible in software. In addition to the steering angle (including the case of zero degrees) of any physically generated wave or beam (eg, in the above example), it can be soft, plane wave or dynamic focusing steering (steering) in transmission or reception (Including the angle is zero degrees). This soft plane wave steering can be thought of as enhancing the physical transmit steering, or purely steering any physically transmitted wave or beam, or receiving dynamic focusing (deflection). In addition to the case where the angle φ is zero degrees, it can be considered that the reception steering is performed in software. The same applies to three-dimensional beam forming using a two-dimensional array. In addition, it is as having described in the method (1).

Similarly to method (1) and method (2), wave number matching can be performed physically and mathematically at the first Fourier transform, and wave number matching is performed at the last inverse Fourier transform. Is also possible. Depending on the steering, in the conversion process with wave number matching, the conversion process can be divided into directions to perform one-dimensional processing, and the speed can be increased. In addition, in the wave number matching, the expressions (F41) and (F43), the expressions (G41) and (G43) are instead frequency-modulated by multiplying them by a space-time signal using their complex exponential functions. May be implemented (frequency modulation of kx, kz, and ky, respectively).
Wave number matching in beam forming using the two-dimensional equations (F41), (F42), and (F43) and the three-dimensional equations (G41), (G42), and (G43) is performed through interpolation approximation. Sometimes you get results fast.
In the case of the two-dimensional case, the wave number matching of the formula (18b) or the formula (18c) is interpolated and approximated with the formulas (7) and (8) for the two-dimensional Fourier transform R ′ (k _x , k) of the received signal. (Expression (F44)), and F (k _x ', k _y ') is subjected to two-dimensional inverse Fourier transform. This approximation process is also not disclosed in the prior art documents.
In the case of the three-dimensional case, with respect to the three-dimensional Fourier transform R ′ (k _x , k, k _z ) of the received signal, together with the formulas (7 ′) and (8 ′), the formula (C44) or the formula (D44 ) Is performed through interpolation approximation (formula (G44)), and F (k _x ', k _y ', k _z ') is subjected to three-dimensional inverse Fourier transform. This process is also not disclosed in the prior art documents.

  Further, in a convex transducer, sector scan, IVUS, or the like, when a wide wave is transmitted or received (cylindrical wave) in the angle θ direction in polar coordinates (r, θ) in the radius r direction (FIG. 7), When a wide wave is transmitted in the direction of the angle θ of the polar coordinate system (r, θ) in the same polar coordinate system (r, θ) as in FIG. (Refer to FIGS. 8A (a) to 8 (c)), and for the echo signals collected for aperture plane synthesis in the polar coordinate system, Cartesian coordinates (x, y) are converted into polar coordinates (as in method (1)). The image signal can be generated in a Cartesian coordinate system (x, y) or polar coordinates (r, θ). In addition, a transmission or reception plane wave may be generated at an arbitrary distance position using a physical aperture element array represented by the polar coordinate system as described above or a physical aperture having an arbitrary aperture shape, and beamforming may be performed in the same manner (FIG. 8B (d) to (f)). This is equivalent to generating a virtual linear aperture array (or plane wave) at the distance position. If the distance position is set to zero, this corresponds to a case where a linear aperture array is virtually used. The distance position can be set not only behind the physical aperture but also at the front, and a virtual linear aperture array (or plane wave) can be generated at these positions. A virtual linear aperture array may be used as a virtual receiver instead of a virtual source, or may also serve as a virtual source. The same applies when other transmission beamforming is performed or when they are performed in a spherical coordinate system. On the other hand, when a convex transducer, sector scan, IVUS, or the like is used, or when a virtual source installed behind a physical aperture having an arbitrary aperture shape is used, directly according to method (5). An image signal can be generated in Cartesian coordinates. In addition, a transmission or reception plane wave may be generated at an arbitrary distance position using a physical aperture element array represented by the polar coordinate system as described above or a physical aperture having an arbitrary aperture shape, and beamforming may be performed in the same manner (FIG. 8B (d) to (f)). This is equivalent to generating a virtual linear aperture array (or plane wave) at the distance position. If the distance position is set to zero, this corresponds to a case where a linear aperture array is virtually used. The distance position can be set not only behind the physical aperture but also at the front, and a virtual linear aperture array (or plane wave) can be generated at these positions. A virtual linear aperture array may be used as a virtual receiver instead of a virtual source, or may also serve as a virtual source. In these cases, echo signal imaging, displacement measurement, and the like can be performed consistently in the same Cartesian coordinate system. The same applies to the polar coordinate system. In these, similarly to the method (1), the same processing can be performed in an arbitrary orthogonal coordinate system or by converting to an arbitrary orthogonal coordinate system. In these cases, transmission focusing may be performed. In addition, as described above, the virtual source and the virtual receiver are not necessarily installed behind the physical aperture, but may be installed in front of the aperture, and can be installed arbitrarily regardless of the shape of the physical aperture. (Patent Literature 7, Non-Patent Literature 8). Thus, the present invention is not limited to the above. In addition, in wave number matching in such beam forming, interpolation approximation processing may be performed to obtain an approximate solution at high speed.

  In addition, since apodization processing for transmission, reception, or both for the received signal is linear processing, it can be performed at various timings (hardware at the time of reception or software after reception). As described above, it may be physically apodized at the time of transmission. In the case where the accuracy is increased in the case where wave number matching is performed through interpolation approximation using Equation (7) or Equation (7 ′), processing is performed under appropriate oversampling at the cost of an increase in calculation amount. There is a need. In that case, it is necessary to be careful that the number of data of the Fourier transform increases, unlike the case where the signal at an arbitrary position can be selectively generated when the interpolation approximation process is not performed. These processes can be performed in the same manner as the method (1), and are also performed in the same manner in the other methods (3) to (7).

Method (3): Multistatic Type Aperture Synthesis FIG. 11 is a schematic diagram of multistatic type aperture synthesis. Multistatic aperture surface synthesis is a method in which ultrasonic waves are emitted from one element of an array and echoes are received by a plurality of elements around the element. A low resolution image signal is obtained for each radiation, and a high resolution image signal is generated by superimposing a plurality of low resolution image signals obtained. The present invention may be used to generate this low resolution echo signal.

  As described above, it is a conventional method to generate a low resolution echo signal from echo signals received for each element radiation and superimpose them. On the other hand, in the present invention, a signal group composed of signals having the same transmission / reception position relationship is set as one set, and digital monostatic aperture synthesis is performed for each set, and a plurality of values are obtained by this method (3). The processing is finished by superimposing these low resolution image signals. Actually, the superimposition that is linear processing can be performed in the frequency domain before the inverse Fourier transform processing in the horizontal direction, which is faster, and the horizontal alignment for performing the superposition is also When superimposing, an image signal can be generated without performing interpolation approximation at high speed by multiplying the complex exponential function for performing the shifting process in the horizontal direction and rotating the phase in the horizontal direction. The inverse Fourier transform may be performed once by the fast inverse Fourier transform. In addition, when performing the inverse Fourier transform in the horizontal direction to generate each low-resolution echo signal, the phase is rotated in the horizontal direction by multiplying the complex exponential function for performing the horizontal shifting process at the same time. It is also possible to overlap in the area. In that case, a dedicated fast inverse Fourier transform may be performed.

However, what is important is that when applying the monostatic aperture plane synthesis processing program, when s = 2, when the distance in the x direction between the reception position y = 0 and the transmission position y = 0 is Δx, This is to calculate and use a converted distance y ′ of the propagation path until reception at a position that is separated by Δx with respect to the distance y (coordinate y) of the point of interest. ) To calculate the conversion distance represented by Further, when s = 1, if the distance in the x direction between the reception position of y coordinate y = 0 and the transmission position of non-zero y coordinate y = Y is Δx, it is deflected with respect to the distance y (coordinate y) of the point of interest. When the angle is zero degree, the conversion distance represented by the equation (20b) is calculated (the y coordinate of the transmission position and the reception position may be considered in reverse).

  When the deflection angle is θ (including zero degree), multistatic aperture synthesis is performed to generate a beam that has been subjected to at least reception dynamic focusing (when s = 2, transmission dynamic focusing can also be realized). As a beam forming method to be performed, a wave is transmitted from each of a plurality of transmission aperture elements in a transmission effective aperture element array, and a wave arriving from a measurement object is transmitted by at least one of a plurality of reception aperture elements at different positions. Receives and generates a received signal (can be processed by the device of the present invention even if there is only one), and the transmission aperture element has a wave generated by at least reflection or backscattering in the measurement object (S = 2) or generated by at least transmission, forward scattering, or refraction in the measurement object In the receiving effective aperture element array having an arbitrary x coordinate and a zero y coordinate so as to be (s = 1) without depending on the x coordinate of the receive aperture element generating the received signal. A position opposite to the reception effective aperture element array, each serving as one of the reception aperture elements, or one of a plurality of transmission aperture elements different from any of the reception aperture elements, or having a non-zero constant y coordinate Each of the plurality of transmission aperture elements in the transmission effective aperture element array (when s = 1, the y coordinates of the transmission position and the reception position may be considered in reverse).

That is, when steering is performed, the steering process described in the method (2) is applied to each of the monostatic aperture synthesis data groups generated by the same combination of the positions of the transmitting element and the receiving element. And the same processing may be performed. The same applies when the transmission and reception steering angles are different. However, even when the deflection angle is non-zero, in applying the monostatic aperture surface synthesis processing program, as with the case where the deflection angle is zero, the distance y (coordinate y) of the point of interest is s. When = 2, the conversion distance represented by the equation (20a) is used, and when s = 1, the conversion distance represented by the equation (20b) is used. Therefore, similarly to the methods (1) and (2), the deflection angle may be set to zero degree or non-zero degree in the deflectable program.
Further, the transmission can be processed when the plane wave of the method (1) is transmitted, and can also be processed when arbitrary transmission beam forming such as fixed focusing is performed.

As another method, the y coordinate of the transmission and reception aperture elements is zero for each of the reception signal groups obtained by arranging the reception signals having the same distance Δx in the horizontal coordinate between the transmission position and the reception position. When (s = 2), between the transmission aperture element, the point of interest, and the reception aperture element expressed using the deflection angle θ, the y coordinate of the point of interest including the positions of the transmission and reception apertures, and the distance Δx. When the y-coordinate of the transmission aperture element is non-zero (s = 1, the y-coordinate of the transmission position and the reception position may be reversed) , The distance between the transmission aperture element, the point of interest, and the reception aperture element expressed by using the deflection angle θ, the y coordinate of the point of interest, the y = Y coordinate of the transmission aperture element, and the distance Δx (formula (20d)) And the image signal obtained by setting the deflection angle in the above monostatic aperture synthesis Can be corrected with respect to the position in the horizontal direction in the frequency domain, and these can be superimposed to generate an image signal without performing interpolation approximation processing. Although the spatial resolution in the depth direction is reduced, a large steering angle can be generated.

Also, when performing three-dimensional wave digital signal processing using a two-dimensional aperture element array, for example, an axial direction y determined by the orientation of the aperture of a flat receiving aperture element array and lateral directions x and z orthogonal thereto In a Cartesian Cartesian coordinate system using the coordinates of, the same processing can be performed, and the zero or non-zero deflection angle formed by the generated beam direction and the axial direction is expressed using the elevation angle θ and the azimuth angle φ. , A wave is transmitted from each of the plurality of transmission aperture elements in the transmission effective aperture element array, and a wave arriving from the measurement target is received and received by at least one of the plurality of reception aperture elements at different positions. The transmission aperture element generates a signal whose wave is generated by at least reflection or backscattering on the measurement object (s = 2), or the measurement object Any x-coordinate and z-coordinate without depending on the x-coordinate and z-coordinate of the receiving aperture element that generates the received signal so that it is generated at least by transmission, forward scattering, or refraction (s = 1). One of the plurality of transmit aperture elements in the receive effective aperture element array, or one of a plurality of transmit aperture elements different from any of the receive aperture elements, , One of a plurality of transmit aperture elements in the transmit effective aperture element array having a non-zero constant y coordinate and facing the receive effective aperture element array (when s = 1, transmit The y coordinate of the position and the receiving position may be considered in reverse). Similar to the two-dimensional wave digital signal processing using the one-dimensional aperture element array described above, when the deflection angle is zero degree (without steering) or non-zero degree (with steering), the transmission element and the reception element What is necessary is just to perform the processing with or without steering as described in the method (2) on each of the data groups for monostatic aperture plane synthesis generated from the same combination of positions, and perform the same processing. The same applies when the transmission and reception steering angles are different. However, it is important to apply the monostatic aperture plane synthesis program when the deflection angle is zero (no steering) or non-zero (steering). When s = 2, y If the distance in the x direction (lateral direction) between the reception position of = 0 and the transmission position of y = 0 is Δx, and the distance in the z direction (elevation direction) is Δz, reception is performed at a position separated by Δx and Δz in two directions. It is to calculate and use the conversion distance y ′ of the propagation path until the calculation, and to calculate the conversion distance represented by the equation (20e). Further, when s = 1, if the distance in the x direction between the reception position with the y coordinate y = 0 and the transmission position with the non-zero y coordinate y = Y is Δx and the distance in the z direction is Δz, the equation (20f) The calculated conversion distance is calculated (the y coordinate of the transmission position and the reception position may be considered in reverse).

  Further, the transmission can be processed when the plane wave of the method (1) is transmitted, and can also be processed when arbitrary transmission beam forming such as fixed focusing is performed.

  As another method, transmission and reception are performed for each reception signal group obtained by arranging reception signals having the same distances Δx and Δz in the horizontal x-coordinate and z-coordinate between the transmission position and the reception position. When the y coordinate of the aperture element is zero (s = 2), the transmission aperture represented by using the elevation angle θ and the azimuth angle φ, the y coordinate of the point of interest including the transmission and reception aperture positions, and the distances Δx and Δz. The distance between the element, the point of interest, and the receiving aperture element is half the linear distance, or the y coordinate of the transmitting aperture element is non-zero (s = 1, the y coordinates of the transmitting position and the receiving position may be considered in reverse) Between the transmission aperture element, the interest point, and the reception aperture element expressed using the elevation angle θ and the azimuth angle φ, the y coordinate of the point of interest, the y coordinate of the transmission aperture element, and the distances Δx and Δz. Set the deflection angle in the above monostatic aperture synthesis using the distance of Each image signal obtained Te was corrected for lateral position in the frequency domain, can generate an image signal without performing the interpolation approximation process by superimposing them. Although the spatial resolution in the depth direction is reduced, a large steering angle can be generated.

  Also, in order to generate an image signal representing the propagation of an unknown wave source or the wave it generates (so-called passive mode), the y coordinate of the estimated unknown wave source is set to the y coordinate of the transmission aperture element, It is good to perform beam forming. It is also effective to make observations while changing the y coordinate by trial and error. For example, effects such as image formation, increased spatial resolution, increased signal intensity, increased contrast, etc. should be obtained, and a series of processing is automatically performed using these as criteria. Is also possible.

  As will be described later, as the information on the wave source position or the transmission aperture element, the position with respect to the reception aperture element, the direction or distance of the existing position, the direction of the aperture, or the propagation direction of the generated wave may be given. In addition, the time at which a wave is generated by an arbitrary wave source may be given. It may be observed by other devices, and the received signal itself or a wave propagating at a higher speed may be emitted and transmitted from the wave source.

  Obtain the center of gravity (center) frequency or instantaneous frequency of the multi-dimensional spectrum for the received signal, determine the direction in which the wave source exists or the propagation direction of the wave from this, adjust the deflection angle for transmission or reception, and adjust the beam Forming may be performed. In addition, the center-of-gravity (center) frequency or instantaneous frequency of the multi-dimensional spectrum is obtained from the beam-formed image signal, and the direction in which the wave source exists or the propagation direction of the wave is obtained from this, and the deflection angle of transmission or reception is obtained. The beam forming may be performed by adjusting. These processes can be performed in a plurality of reception apertures or reception effective apertures to geometrically determine the position or direction where the wave source exists. These processes are useful and may be applied to other beam forming.

  As described in the method (2) for monostatic aperture synthesis, in the method (3) for multistatic aperture synthesis, an arbitrary beamforming can be generated using echo signals collected for aperture synthesis. (Actually, an image signal can be generated even if the processing described in the methods (1) and (4) to (7) is performed on these data). Although it may be effective that the amount of data is abundant compared to the monostatic type, the amount of calculation increases. In the plane wave processing of the method (1), the aperture plane synthesis processing can be performed by using a code. Further, in a convex transducer, sector scan, IVUS, or the like, when a wide wave is transmitted or received (cylindrical wave) in the angle θ direction in polar coordinates (r, θ) in the radius r direction (FIG. 7), When a wide wave is transmitted in the direction of the angle θ of the polar coordinate system (r, θ) in the same polar coordinate system (r, θ) as in FIG. (Refer to FIGS. 8A (a) to 8 (c)), and for the echo signals collected for aperture plane synthesis in the polar coordinate system, Cartesian coordinates (x, y) are converted into polar coordinates (as in method (1)). The image signal can be generated in a Cartesian coordinate system (x, y) or polar coordinates (r, θ). The same applies when other transmission beamforming is performed or when they are performed in a spherical coordinate system. On the other hand, the image signal can be directly generated in Cartesian coordinates according to the method (5) in the convex transducer, sector scan, IVUS or the like. In that case, imaging of the echo signal, displacement measurement, and the like can be performed consistently in the same Cartesian coordinate system. In these, similarly to the method (1), the same processing can be performed in an arbitrary orthogonal coordinate system or by converting to an arbitrary orthogonal coordinate system. In addition, the beam forming described in paragraphs 0221 to 0222 of the method (1) and the paragraph 0240 of the method (2) can be performed in the same manner. For example, a virtual source, a virtual receiver, or the like It can be installed arbitrarily without depending on the shape (Patent Document 7, Non-Patent Document 8). The present invention is not limited to this (hereinafter the same).

  In addition, as described above, the spatial resolution in the depth direction is reduced, but it is possible to deflect as another method in order to generate a large steering angle. In this case as well, transmission beam forming and reception beam forming are possible. The case where the steering angle is different can be processed in the same manner. The conversion distance may be calculated using the lateral distance between the transmission aperture element and the reception aperture element, the transmission steering angle and the reception steering angle, and in the case of the transmission type, the distance between the transmission aperture element and the reception element.

  Any steering in the method (3) is basically performed in a software manner. In addition, apodization may or may not be performed at the time of transmission. In addition, since the reception apodization process is also a linear process, it can be performed at various timings (hardware or software). In consideration of the amount of calculation that depends on the effective aperture width and the like that determines the number of the above, it can be easily implemented at an appropriate timing. For example, each set for initiating generation of a low resolution echo signal can be weighted or apodized in the frequency domain or spatial domain to the generated low resolution signal.

In addition, in applying the monostatic aperture surface synthesis of method (2), wave number matching can be performed at the first Fourier transform, both physically and mathematically, and wave number matching can be performed at the last inverse Fourier transform. It is also possible to do this. Also, wave number matching may be performed at high speed through the above-described interpolation approximation. In the interpolation approximation, approximation may be performed using linear interpolation approximation or nearest neighbor data itself, higher-order interpolation approximation may be performed, or a sinc function may be used. In order to increase the accuracy of wave number matching through the interpolation approximation, it is necessary to perform processing under appropriate oversampling at the cost of increasing the amount of calculation. In that case, it is necessary to be careful that the number of data of the Fourier transform increases, unlike the case where the signal at an arbitrary position can be selectively generated when the interpolation approximation process is not performed.
Further, in the horizontal alignment for performing superposition described in paragraphs 0243, 0247, and 0250, the phase is rotated in the horizontal direction by multiplying by a complex exponential function for performing the shifting process in the horizontal direction. Instead, spatial shifting processing may be performed through interpolation approximation in order to realize faster processing. In the interpolation approximation, approximation may be performed using linear interpolation approximation or nearest neighbor data itself, higher-order interpolation approximation may be performed, or a sinc function may be used. Even in this case, in order to improve the accuracy of the interpolation approximation, it is necessary to perform processing under appropriate oversampling at the cost of an increase in calculation amount.

Method (4): Fixed Focusing FIG. 12 is a schematic diagram of fixed focusing using a linear array. Fixed focusing is a method in which each element is delayed so that one point is a focus point and ultrasonic waves reach the focus point simultaneously. A part or all of the physical aperture of the array type transducer is received as an effective aperture, and the measurement target is scanned. Of course, steering may be performed. The transmission and reception steering angles may be different.

In the fixed focusing, the image signal is generated by the method (1): beam forming during plane wave transmission, or the method (3): multi-static aperture synthesis, or the beam forming and method of plane wave transmission in method (1). This is performed by a method combining the reception dynamic focusing of (2) or method (3). In that case, there are the following three methods.
(I) Each received signal obtained in the effective aperture width is subjected to one image signal generation process on the superposition.
(Ii) A so-called normal low-resolution image signal is generated using the received signal for each transmission, and they are superimposed.
(Iii) Similar to the multi-static aperture plane synthesis, image signals are generated by setting the same transmission / reception positional relationship as a set, and then superimposed.

  When performing transmission and reception in the radius r direction of polar coordinates in convex transducers, sector scans, or IVUS, or when performing beamforming using a virtual source placed behind in an arbitrary aperture shape, Cartesian coordinates ( Processing may be performed by replacing x, y) with polar coordinates (r, θ), and an image signal can be generated at polar coordinates (r, θ). As described above, interpolation approximation may be required after the image is generated. The same applies to transmission and reception using a spherical coordinate system. There is a report (Non-Patent Document 6) of processing performed with approximation processing when transmission focus is performed, and similarly, a result is obtained in polar coordinates (r, θ). The inventor of the present application directly generates an image signal in a Cartesian coordinate system as a result of beam forming for transmission or reception in the polar coordinate system, spherical coordinate system, or arbitrary orthogonal curve coordinate system (5). , (5-1), (5-1 ′) and (5-2) were also invented. In that case, imaging and displacement measurement of transmission signals, reflection signals, scattering signals, attenuation signals, etc. can be performed consistently in the same Cartesian coordinate system. In these, similarly to the method (1), the same processing can be performed in an arbitrary orthogonal coordinate system or by converting to an arbitrary orthogonal coordinate system. In addition, the beam forming described in paragraphs 0221 to 0222 of the method (1) and the paragraph 0240 of the method (2) can be performed in the same manner. For example, a virtual source, a virtual receiver, or the like It can be installed arbitrarily without depending on the shape (Patent Document 7, Non-Patent Document 8). The present invention is not limited to this (hereinafter the same). Further, as described above, it is possible to deflect, but it is also possible to handle a case where the deflection angles of physical transmission beam forming and soft reception beam forming are different. Transmission steering can also be applied in software. In that case, the deflection angle may be different from other deflection angles. It is also possible to physically perform beamforming at the time of reception. Transmission and reception can be interpreted in reverse. Apodization may be performed at the time of transmission, or reception apodization processing may be performed on the received signal (hardware at the time of reception or software after reception). When apodization is performed in software, it is performed according to method (1) or method (3). Apodization is performed in the same manner when using a method that combines the beam forming of plane wave transmission and the reception dynamic focusing of method (2) or method (3).

  Any processing of the method (4) using the method (1) for performing the plane wave processing can theoretically and actually perform any physical transmission or reception beamforming, By processing as described above, various combinations of beam forming can be performed (for example, physical using a computer or a dedicated device other than that performed in a soft beam forming using a computer or a dedicated device). Plane wave transmission and reception processing can be performed for each or both of the processing, such as focusing, steering, and apodization, which may be performed at the time of transmission and reception, or transmission and reception can be reversed as described above. Can be captured and processed). For example, regarding simultaneous transmission of a plurality of beams described in paragraphs 0109, 0112, 0365, 0367, 0368, etc., the beams interfere or do not interfere with each other with or without physical deflection. In some cases, or when the focus beamforming is performed at different timings in the target simultaneous phase, or when both received signals are mixed, the physical focus (sub aperture width, distance and depth, Regardless of whether the position, etc.) are the same or different, and regardless of whether the physical transmission deflection angle is the same or different, the above processing of method (4) is effective, and in particular, (i If a method of performing one image signal generation process on the superposition of received signals obtained at the effective aperture width of It is intended to. In method (4), it is not always necessary to perform beam forming at a position where waves do not interfere (described in paragraphs 0030, 0364, etc.). High frame rate can be realized by processing. At this time, if the software transmission deflection angle and the reception deflection angle applied to the plurality of focus beams to be performed are the same, the above-described processing may be performed. In addition, in the case where multiple transmissions are performed, such as when performing focusing at a plurality of positions or transmission dynamic focusing in the target simultaneous phase, the same processing can be performed for superimposing received signals. With respect to the received signal group received in the target simultaneous phase, this processing can be applied to all of the received signals in a state in which the time is aligned based on the position and timing of the transmitting element.

  Also, if any of the software transmission deflection angles and reception deflection angles applied to multiple focus beams is different, divide them into the same ones, apply the same processing to the same ones, and obtain the final result. What is necessary is just to superimpose in the frequency domain to obtain. For a single physical transmit beam (with or without deflection), multiple deflected receive beams (including a deflection angle of 0 °) may be generated and processed similarly. Even when a plurality of different physical deflections are performed, the processing results may be obtained by dividing them into the same one, or they may be processed without being divided. In the case of division, superposition may be performed in the spatial domain or the frequency domain.

  When transmitting in multiple directions physically, there may be software-specific transmission and reception deflections for each transmission deflection angle, in which case the transmission beam is separated in the frequency domain. Or, separation processing such as independent component analysis (ICA: There are many documents such as Te-Won Lee, Independent Component Analysis: Theory and Applications, Springer, 1998 etc. which are relatively old books as a reference) May be applied and processed. Analog devices may be used. As an example, software transmission and reception deflection angles may be set in the same manner as the respective physical deflection angles. Others are described for signal separation (eg, paragraph 0370).

  Here, it has been described that the present method is implemented for various fixed focusing processes. However, the present method is not limited thereto, and can be used when other transmission beam forming is performed. With or without focusing (multi-focus that realizes multiple different focus positions with respect to the effective aperture) or without, with or without deflection (multiple steering with different deflection angles) or without apodization (including different cases for each position) Even when performing a plurality of transmissions or receptions with different waves or ultrasonic parameters such as none, F number, transmission ultrasonic frequency or transmission band are different, reception frequency or reception band, pulse shape is different, beam shape is different, etc. The beam forming can be performed in the same manner and with new features that cannot be generated by a single beam forming with them fixed. For example, it is known that a plurality of focus points can be obtained by superposition, and that a wide band (high resolution) can be obtained both in the depth direction and in the horizontal direction, but these processes can be performed at high speed. In order to obtain harmonics, when using a so-called pulse inversion method (emitting pulses having different polarities as ultrasonic parameters) or the like, received signals can be superimposed and similarly processed at high speed. Of course, it is also possible to superimpose received signals after beamforming. The received signals of two or more beams may be superimposed.

  The above processing may be applied to simultaneous reception beamforming on the basis of considering the transmission and reception in reverse. In addition, the above processing may be performed for both transmission and reception.

  In addition, when processing is divided into a plurality of beam forming, it may be processed in parallel. Depending on various waves such as the above deflection angle, ultrasonic parameters, position of the region of interest, etc., there are cases where it is divided into a plurality of beam forming. One received signal may be used for multiple purposes such as imaging, measurement, treatment, etc., and a large amount of information, for example, high-accuracy, high-resolution, transmitted, reflected, scattered, attenuated signals, etc. A signal that is generated by forming and subjected to post-processing such as filtering may be generated according to the purpose. However, appropriate beam forming may be performed according to the purpose, and they may be processed in parallel.

In addition to an arbitrary beam such as a fixed focus beam, beam forming at the time of transmission of an arbitrary wave (including a wave not subjected to beam forming), superposition processing at the time of transmission of a plurality of beams and waves, and simultaneous multiple beams And processing at the time of wave transmission. In other words, reception beamforming (such as dynamic focusing) can be performed at a time regardless of whether one or a plurality of transmissions are performed. The plurality of beam forming operations may be performed using a multidirectional aperture plane synthesis method, and in this case as well, the beam forming operations are performed at high speed in the same manner. The present invention is not limited to these.
In addition, both physically and mathematically, wave number matching can be performed during the first Fourier transform, and wave number matching can be performed during the last inverse Fourier transform. One of the features of the present invention is that interpolation approximation processing is not performed in wave number matching, but this method (4) applying the method described in the above methods (1) to (3) is also applicable. As in methods (1) to (3), interpolation approximation processing may be performed in wave number matching, and approximate wave number matching described therein is performed, and beam forming is performed at high speed. There is. In order to perform approximate wave number matching with high accuracy, it is necessary to appropriately oversample the received signal at the cost of an increase in the amount of calculation. In that case, it is necessary to be careful that the number of data of the Fourier transform increases, unlike the case where the signal at an arbitrary position can be selectively generated when the interpolation approximation process is not performed.

Method (5): Image signal generation in a polar coordinate system Method (5) transmits or receives (part of) an ultrasonic cylindrical wave in a two-dimensional polar coordinate system (r, θ) such as convex array, sector scan, or IVUS. This is a method of generating an image signal in a Cartesian coordinate system in the case (see FIG. 7). The methods (1) to (4) and (6) can be performed.

Hereinafter, polar coordinate display of Fourier transform will be described. The two-dimensional Fourier transform is expressed by equation (22).
Since the received echo signal in the polar coordinate system is expressed as f (r, θ), Equation (23) is established.
Therefore, the equation (24) is obtained through the Jacobi operation. In this way, the wave represented in the polar coordinate system can be decomposed into plane wave components (k _x , k _y ) in the Cartesian coordinate system. Similarly, a wave represented by arbitrary orthogonal curve coordinates can be decomposed into plane wave components (k _x , k _y ) in a Cartesian coordinate system.

Method (5-1): Cylindrical Wave Transmission or Reception Image Signal Generation FIG. 13 is a flowchart showing digital signal processing during cylindrical wave transmission. From Expression (24), the Fourier transform in the angle θ direction on the opening is expressed by Expression (25).
Here, r ₀ is the radius of curvature of the convex probe, and x ₀ and y ₀ are the x-axis and y-axis coordinates representing the array element position of the convex probe. In step S21, the received signal is Fourier-transformed with respect to time t, and in step S22, the received signal is Fourier-transformed (FFT) with respect to the angle θ, whereby the received signal in the polar coordinate system is converted into a plane wave component (k _x , k _y ).

Therefore, for example, an image signal can be generated by performing wave number matching represented by the equation (26) (step S23) and performing inverse Fourier transform on the space (x, y).

Further, in step S24, the two-dimensional spectrum is multiplied by the following complex exponential function to calculate an angular spectrum of each depth y.
Alternatively, the calculation may be performed with step 23 and step 24 reversed.

Alternatively, without using Equation (26a) and Equation (26b), the following complex exponential function is applied in accordance with Method (5), wave number matching is performed, and angular spectra at each depth position y are obtained. good.

  Further, for example, the frequency component k of the angular spectrum is added in step S25, and an inverse Fourier transform (IFFT) is performed on the horizontal wave number kx in step S26, whereby an image signal is obtained in step S27. A purely two-dimensional inverse Fourier transform may be applied.

  When steering is performed, according to method (1), wave number matching in the x direction and y direction may be performed and spatial resolution may be obtained according to equations (9a) to (9c) using the deflection angle θ. As will be described later, when the calculation is performed in the polar coordinate system (r, θ), a steering angle (an angle formed with the radial direction) is provided in the polar coordinate system, and the steering can be similarly performed. Physical steering can be implemented, transmission, reception, transmission / reception soft steering can be implemented, or physical steering and soft steering can be implemented in combination. There are other methods such as method (1).

  This method does not require interpolation processing for wave number matching and coordinate system conversion to obtain image signal of Cartesian coordinate system (x, y) from polar coordinate system (r, θ) signal, and it is fast and highly accurate. Beam forming is performed. Similar to the plane wave transmission in a linear array transducer, a cylindrical wave can be deflected in a polar coordinate system. The same processing can be performed when the transmission beam forming and the reception beam forming have different steering angles. Soft steering can also be applied. Apodization can be performed similarly. In the case of a cylindrical wave, at the different positions in the z-axis direction orthogonal to the two-dimensional polar coordinate system (that is, the z-axis in the cylindrical coordinate system (r, θ, z)) The above processing may be performed by superimposing those received by performing the above transmission at the same time phase but at different times. The z-axis direction may be focused by an analog device (lens), or arbitrary processing can be performed by the digital signal processing of the present invention. The same calculation can be performed when the wave propagation direction is in the center direction (for example, useful for various imaging or CT using a circular-based array transducer surrounding a HIFU treatment or an object). Of course, reception-only beamforming may be performed in them, and the same processing is performed. The received signal represented by polar coordinates (r, θ) can be processed by replacing the Cartesian coordinates (x, y) in method (1) with polar coordinates (r, θ). , θ), the image signal can be generated as described above, and interpolation approximation is performed in the subsequent processing. In these, similarly, steering can be performed. The methods (2) to (4) and (6) can be similarly performed.

  Also, when the received signal is represented as a digital signal with Cartesian coordinates (x, y), f (x, y) is Fourier-transformed with respect to the radius r and the angle θ and processed, contrary to the equation (22). After all, the image signal can be generated in the polar coordinate system (r, θ), or the image signal can be generated in the Cartesian coordinate system (x, y) using each method. Steering and apodization may occur as well.

  Further, as shown in FIGS. 8B (d) to 8 (f), transmission or reception is performed at an arbitrary distance position using a physical aperture element array represented by the polar coordinate system as described above or a physical aperture having an arbitrary aperture shape. Alternatively, both plane waves may be generated and beam forming may be performed in the same manner, and an image signal is generated in a Cartesian coordinate system, a polar coordinate system, or an orthogonal curved coordinate system set in accordance with a physical aperture shape. Sometimes. This is equivalent to generating a virtual linear aperture array (or plane wave) at the distance position. If the distance position is set to zero, this corresponds to a case where a linear aperture array is virtually used. The distance position can be set not only behind the physical aperture but also at the front, and a virtual linear aperture array (or plane wave) can be generated at these positions. The plane wave may be steered or the virtual linear opening may be tilted (virtual mechanical steering). Of course, if necessary, the physical opening is mechanically steered. When only these plane waves are transmitted or received, other beam forming is sometimes performed on the basis of the case of transmitting and receiving cylindrical waves, respectively.

Method (5-1 ′): Image signal generation using virtual source and other arbitrary shape aperture array When transmitting wave from arbitrary aperture shape such as linear array type transducer as well as circular aperture array A case where a part of a cylindrical wave is generated using an installed virtual source (see FIGS. 8A (a) to (c)) will be described.

  (I) When the received signal acquired for monostatic aperture plane synthesis is used, if necessary for the received signal transmitted and received in each element and stored in a memory or the like, a complex exponential function is applied to the Fourier transform. Multiply the response of the wave emitted from the virtual source into a digital received signal represented by polar coordinates (r, θ), and then follow method (5) or use method (5-1) The image signal can be generated directly in the (x, y) coordinate system. Similarly, the received signal can be represented as a digital signal of polar coordinates (r, θ), and the process of replacing the Cartesian coordinates (x, y) in method (1) with polar coordinates (r, θ) can be performed. An image signal can also be generated at (r, θ). Of course, monostatic processing of method (2) is also possible in the polar coordinate system (r, θ).

  (Ii) In addition, when using the received signal acquired for multi-static aperture plane synthesis, there is a need for the received signal transmitted in each element and received by the surrounding elements and stored in the memory etc. For example, multiply the Fourier transform by the complex exponential function, and use the response of the wave emitted from the virtual source as the digital received signal represented by polar coordinates (r, θ), and implement the multistatic aperture plane synthesis method (3) it can. Another process is to follow the method (5) or superimpose the digital received signal at each receiving element and then use the method (5-1) to directly (x, y) coordinate system. Can generate an image signal. Similarly, it is possible to superimpose the digital reception signal at each receiving element, and then to perform the processing in which the Cartesian coordinates (x, y) in method (1) are read as polar coordinates (r, θ). An image signal can also be generated at (r, θ). Of course, the multi-static processing of the method (3) can be performed in the polar coordinate system (r, θ) without superposition.

  (Iii) In these processes, in order to omit the process of rewriting the signal received by the physical aperture array into the digital signal of the polar coordinate system (r, θ), the sampling is originally performed in the polar coordinate system (r, θ). A transmission or reception delay pattern may be used to transmit and receive samples from each aperture element. Based on the method (5-1), the method (2) based on the method (5), and the method (3), an image signal can be directly generated in the (x, y) coordinate system. Similarly, the received signal is represented as a digital signal of polar coordinates (r, θ), and the processing in which the Cartesian coordinates (x, y) in methods (1) to (3) are replaced with polar coordinates (r, θ) is performed. It is also possible to generate an image signal in polar coordinates (r, θ).

  (Iv) Similarly, in the case where a part of a cylindrical wave is generated by using a virtual source installed at the rear in an arbitrary opening shape (see FIGS. 8A (a) to (c)), the above (i) to ( In iii), the Fourier transform of the received signal received by each element and stored in the memory or the like is multiplied by a complex exponential function to represent the received signal as a digital signal in Cartesian coordinates (x, y) (however, the time is Or interpolation approximation, and conversely to equation (22) in method (5-1), f (x, y) is Fourier transformed with respect to radius r and angle θ, and finally, polar coordinates The image signal can be generated in the system (r, θ), or each method can be used to generate the image signal in the Cartesian coordinate system (x, y). In the orthogonal curve coordinate system (curved coordinate system) set in accordance with the opening shape, an image signal can be generated in the same manner.

  In (i) to (iv), various beam forming described in the method (5-1) can be performed.

  As described in the method (1) and the like, a virtual source (FIG. 8A (FIG. 8A (FIG. 8A) (FIG. 8A)) is set behind an arbitrary opening (a linear array type transducer opening or other pseudo array opening obtained by mechanical scanning). (see a) to (c)), when transmitting a cylindrical wave (using a transmission delay), the coding is performed at each element in the same manner as in the case of plane wave transmission, and then received. Generate received signal group for aperture plane synthesis by decoding received signal, and directly generate image signal in arbitrary Cartesian coordinate system such as Cartesian coordinate system or polar coordinate system by the above processing. Can do. In addition, a virtual receiver may be set instead of the virtual source, and the virtual receiver may also serve as the virtual source.

In addition, a virtual source (see FIG. 8A (FIG. 8A) shown in the method (1) or the like, which is set behind an arbitrary same opening (a linear array type transducer opening or other pseudo array opening obtained by mechanical scanning) In the case of transmitting a cylindrical wave using a) to (c) (using transmission delay), the following method can be used.
(A) Method (1) itself is applied directly to the received signal expressed in the Cartesian coordinate system (x, y) obtained by linear array type transducer or mechanical scan, and the image is displayed in the Cartesian coordinate system. Get a signal.
(B) The signal received at each receiving position by a linear array type transducer or mechanical scan is spatially multiplied in the y direction by multiplying the frequency response obtained by (fast) Fourier transformation in the y direction by a complex exponential function. In the polar coordinate system (r, θ) with the virtual source as the origin, the position coordinate in the radius r direction is corrected under θ determined by the reception position, and method (5) or method (5-1) is performed. The image signal is obtained in the Cartesian coordinate system (x, y) or the polar coordinate system (r, θ). Rather than spatial shifting using a complex exponential function, approximate spatial shifting may be performed by zero padding of signal values in the r coordinate system, but in order to improve accuracy, oversampling is appropriately performed. Note that a high sampling rate AD converter and a large amount of memory are required, and the number of data increases before Fourier transform.
(C) A method (5) or a method (5-1) is applied to a signal received in an arbitrary aperture shape other than a linear array type transducer or a pseudo linear array aperture by mechanical scanning. In the coordinate system (x, y), the polar coordinate system (r, θ), or the orthogonal curve coordinate system (curved coordinate system) set in accordance with the aperture shape, an image signal can be generated in the same manner.
(D) A virtual receiver may be used instead of a virtual source, and the virtual receiver may also serve as a virtual source.

As a result of these methods (5-1 ′), for example, using another type of transducer or another mechanical scan, a convex type or sector type transducer as shown in FIG. Image signal when using (Omitted) can be generated in Cartesian coordinate system (x, y), polar coordinate system (r, θ), or orthogonal curve coordinate system (curved coordinate system) set according to the aperture shape .
In addition, conversely, when a linear type transducer is virtually used by using a physically different type transducer (for example, FIG. 8B (d) to (f) when a convex type transducer is physically used. ), The image signal of the virtual source or virtual receiver in the position or behind or in front of the physical aperture) is similarly applied to the Cartesian coordinate system (x, y) or polar coordinate system (r, θ), and can also be generated in an orthogonal curve coordinate system (curved coordinate system) set in accordance with the aperture shape.
In addition, as a special case, for example, when a linear array type transducer is physically used, a case where a cylindrical wave is generated using a virtual source or a virtual receiver behind the physical aperture is applied. An image signal can also be generated in the case where a plane wave or a linear array type transducer virtually generated in the direction (FIG. 8B (g)) is generated.
In these, the generated wave to be transmitted or received may be steered, or the opening may be virtually tilted (virtually mechanically steered). Of course, if necessary, the physical opening is mechanically steered.

Method (5-2): Image Signal Generation at Fixed Focus FIG. 14 is a schematic diagram of fixed focusing using a convex array. Also in the convex array, fixed focusing can be performed as shown in FIG. Each of FIGS. 14A and 14B is a schematic diagram when, for example, the fixed focusing position is equidistant from each effective opening and the arbitrary distance position is set from the convex array. As in the case of the linear array type (method (4)), an image signal can be generated by the same calculation process as that for cylindrical wave transmission. That is, there are the following three methods based on the processing of method (1) or method (3).
(I) Each received signal obtained in the effective aperture width is subjected to one image signal generation process for superposition.
(Ii) A so-called normal low-resolution image signal is generated using the received signal for each transmission, and they are superimposed.
(Iii) Similar to the multi-static aperture plane synthesis, image signals are generated by setting the same transmission / reception positional relationship as a set, and then superimposed.
As described above, the image signal can be directly generated in the Cartesian coordinate system. However, the method (4) can be performed using the coordinate axes of the polar coordinate system to generate the image signal in the polar coordinate system. Similarly, deflection and apodization can be performed. The z-axis direction can be processed in the same manner as (5-1).

  When the received signal is expressed as a digital signal in Cartesian coordinates (x, y), f (x, y) is Fourier-transformed with respect to the radius r and the angle θ. As a result, the polar coordinate system (r , θ) or an image signal in the Cartesian coordinate system (x, y) can be generated using each method. Steering, apodization, and processing in the z-axis direction may be performed in the same manner.

  In the case of steering, the wave number matching in the x direction and the y direction may be performed and the spatial resolution may be obtained according to the method (4). As will be described later, when the calculation is performed in the polar coordinate system (r, θ), a steering angle (an angle formed with the radial direction) is provided in the polar coordinate system, and the steering can be similarly performed. Physical steering can be implemented, transmission, reception, transmission / reception soft steering can be implemented, or physical steering and soft steering can be implemented in combination. There are other methods such as method (1).

  When a virtual source or a virtual receiver is used, a virtual aperture is realized at the position or front and rear using the physical aperture described in the method (5-1 ′), and the above-mentioned Transmission fixed focusing can be performed. For example, a linear array transducer may be virtually realized. In addition, a transducer having an arbitrary opening shape may be realized. An image signal is generated in a Cartesian coordinate system, a polar coordinate system, or an orthogonal curvature coordinate system set in accordance with a physical aperture shape. Physical steering can be implemented, transmission, reception, transmission / reception soft steering can be implemented, or physical steering and soft steering can be implemented in combination. There are other methods such as method (1). In these, the generated wave to be transmitted or received may be steered, or the opening may be virtually tilted (virtually mechanically steered). Of course, if necessary, the physical opening is mechanically steered.

  As described above, the beam forming of the methods (1) to (4) can be performed. However, the present invention is not limited thereto, and the same effect can be obtained by adapting to any beam forming. In particular, when the method (4) is used, reception beam forming can be performed for any transmission beam or wave other than the transmission fixed focus beam. Needless to say, beam forming of overlapping reception signals for each transmission and reception signals at the time of simultaneous transmission of a plurality of different beams or waves can be similarly performed.

Method (5-3): Image signal generation at the time of reception in a spherical coordinate system When a spherical core wave aperture element array is used, three-dimensional digital wave signal processing is performed. When the element array is so, the wave is received in the spherical coordinate system (r, θ, φ), and therefore the received signal of the received wave is represented as f (r, θ, φ). In this case as well, various beamforming can be performed through the Jacobi calculation, as in the case of the two-dimensional polar coordinate system (r, θ).

Specifically, a Cartesian coordinate system (by a three-dimensional Fourier transform performed on the received signal f (r, θ, φ) to decompose the received wave into a plane wave in the Cartesian coordinate system (x, y, z). The equation (27) expressed in the wave number domain or frequency domain (k _x , k _y , k _z ) of _x , _y , _z ) is converted into Jacobi using x = rsinθcosφ, y = rcosθ, and z = rsinθsinφ. By calculation, it is possible to generate an image signal directly in the Cartesian coordinate system without performing the interpolation approximation process by calculating as in Expression (28). Of course, the beam forming of the methods (1) to (4) and (6) can be performed, but the present invention is not limited to these methods, and the same effect can be obtained by adapting to any beam forming. In particular, when the method (4) is used, reception beam forming can be performed on all transmission beams or waves in addition to the transmission fixed focus beam as in the case of the two-dimensional case. Needless to say, beam forming of overlapping reception signals for each transmission and reception signals at the time of simultaneous transmission of a plurality of different beams or waves can be similarly performed. Also, when using a virtual source or a virtual receiver, or when performing steering, etc., all can be carried out in the same manner as in the two-dimensional case, and according to the Cartesian coordinate system, spherical coordinate system, or physical aperture shape. An image signal can be generated in the set orthogonal music coordinate system.

Method (5 "): Image signal generation in an arbitrary orthogonal curve coordinate system when transmitted or received in a Cartesian coordinate system In contrast to the above-described series of methods, reception obtained by transmitting or receiving in a Cartesian coordinate system An image signal represented by a two-dimensional polar coordinate system or a spherical coordinate system can be directly obtained from the signal without performing interpolation approximation, and can be realized by a similar calculation, for example, if the received signal is f (x, y, z), the Fourier transform is performed in the r, θ, and φ directions, and the calculation for decomposing the received signal into a circular wave or a spherical wave corresponding to a plane wave in the Cartesian coordinate system is performed through Jacobian calculation. These methods may also be used to change the FOV (eg, it can be widespread), using Jacobi operations, as well as image signals in any Cartesian coordinate system. Even when transmitted or received in an arbitrary coordinate system, an image signal can be generated in an arbitrary orthogonal coordinate system (different Cartesian coordinate systems such as an orthogonal Cartesian coordinate system and various curved orthogonal coordinate systems). (Including the case where the coordinate system is different, the origin is different or rotated, or the origin position is different or rotated even in the same orthogonal coordinate system) Other methods described in method (5) As with, any transmit beam or wave can be processed, steering can be performed as well, and virtual sources and receivers can be used.

  In addition, both physically and mathematically, wave number matching can be performed during the first Fourier transform, and wave number matching can be performed during the last inverse Fourier transform. One of the features of method (5) is that beam forming is performed in an arbitrary coordinate system without performing interpolation approximation processing in wave number matching, but method (1) is applied by applying method (5). When performing the beam forming described in the method (4), the method (6), and the method (7) in an arbitrary coordinate system, interpolation approximation processing may be performed in wave number matching, which are described in each of them. Approximate wave number matching is performed, and beam forming may be performed at high speed. In order to perform approximate wave number matching with high accuracy, it is necessary to appropriately oversample the received signal at the cost of an increase in the amount of calculation. In that case, it is necessary to be careful that the number of data of the Fourier transform increases, unlike the case where the signal at an arbitrary position can be selectively generated when the interpolation approximation process is not performed.

Method (6): Migration Method Also in the migration process, the apparatus of the present invention can perform the processing without performing the interpolation approximation process in the wave number matching. The migration equation (the following equation (M6 ′)) itself is well known, and the derivation of the equation is also well known, so the derivation of the equation is omitted here.

  Non-Patent Document 12 describes a normal migration process based on 1-element reception based on 1-element transmission (that is, corresponding to a non-deflecting process using transmission / reception data for monostatic aperture synthesis in method (2)). As a basis, in the case of plane wave transmission and / or reception with and without steering (processing corresponding to method (1)), a wave is generated from any transmission aperture element for any identical position. Since the propagation time, which is the time until the wave is received by the reception aperture element that also serves as the transmission aperture element, is different from that in the case of the normal migration, the propagation speed and the coordinates of the target position are reread (the following formula (M1 )), A method of calculating a value represented by the same form (formula (M6)) is disclosed.

  However, the other methods (2) to (5) are not disclosed in Non-Patent Document 12 (when steering is performed in method (2), they are not disclosed). Furthermore, in calculating the equation (M6 ′), conventionally, interpolation approximation has been performed when performing wave number matching (equation (M4) and equation (M4 ′)). In the apparatus of the present invention, Wave number matching is performed with high accuracy without performing interpolation approximation (formula (M7) and formula (M7 ′)).

Take a two-dimensional coordinate with the horizontal direction as the x-axis and the depth direction as the y-axis, and the time coordinate as t. Specifically, in the normal migration, the propagation time required for the wave to reciprocate between the arbitrary aperture element position (x, 0) and the arbitrary position (x _s , y _s ) is expressed by the equation (M0). Is done.

On the other hand, in the plane wave transmission with the steering angle θ (including 0 °), the propagation time is expressed by the equation (M0 ′).

Therefore, in the calculation performed based on the migration method at the time of deflection plane wave transmission in method (1), each of the transport speed c and the coordinate system (x _s , y _s ) representing the target position is replaced with equation (M1). A normal migration formula is calculated (formula (M4) and formula (M5)).

  In summary, among the methods (1) to (5), migration is performed in the same manner except for normal migration that performs non-deflecting processing using transmission / reception data for monostatic aperture surface synthesis in method (2). It can be processed. For example, the calculation procedure of migration during deflection plane wave transmission (including 0 °) in method (1) will be mainly described.

  FIG. 15 is a flowchart showing migration processing when a deflected plane wave is transmitted. When the received signal is represented as r (x, y, t), the received signal at the aperture element array position is represented as r (x, y = 0, t).

First, as shown in the equation (M2), the received signal is subjected to two-dimensional Fourier transform with respect to time t and the horizontal direction x (two-dimensional fast Fourier transform is good).
Here, k = ω / c, and the wave number k and the angular frequency (angular frequency) ω are related by a proportional constant 1 / c and correspond one-to-one, and can be expressed using ω instead of k Can be calculated.

  As described above, a special two-dimensional fast Fourier transform method can also be used. As a general method, first, in step S31, a time t The spectrum of the analytic signal is obtained by performing a fast Fourier transform (FFT) on. In addition, fast Fourier transform in the horizontal direction x may be performed at each frequency coordinate in the band k (which is faster than calculating each two-dimensional spectrum according to the equation (M2)).

When the plane wave is not deflected and transmitted, the above calculation may be performed. However, when the plane wave is deflected, trimming must be performed. Multiply R ′ (x, 0, k) after conversion by a complex exponential function (M3) (similar to the complex exponential function (11) in method (1)) The calculation can be performed directly at once, or a dedicated fast Fourier transform capable of such calculation is also useful).

In step S33, the received signal is subjected to fast Fourier transform (FFT) in the horizontal direction x. Here, the result is expressed as R ″ (k _x , 0, k). By the way, even if it is programmed so that trimming can be performed, a case where a plane wave is transmitted without deflection (steering angle 0 °) can be processed.

Normally, wave number matching (or mapping) is then performed. In the case of the methods (1) to (5) other than the normal migration (when the steering is not performed in the method (2)), the propagation velocity c and the coordinate system (x _s , y _s ) are expressed by the above formula. As shown in (M1), the propagation speed (E1) and the coordinate system (E2) for each beamforming are read and processed.

For the two-dimensional Fourier transform R ″ (k _x , 0, k) calculated in the case of a method (including method (1)) other than normal migration (when method (2) is not steering), Or, for the above R (k _x , 0, k) calculated in normal migration, through interpolation approximation (such as bi-linear interpolation using the angular spectrum closest to the frequency coordinate) , Wave number matching represented by Expression (M4) or Expression (M4 ′) is performed.
However, when the received signal is a reflected signal, s = 2, and when the received signal is a transmitted signal, s = 1.
However, when interpolation approximation is not performed in the wave number matching of the equations (M4) and (M4 ′), the wave number in the depth direction represented in the proviso in each equation is used. Each wave number in the depth direction is obtained by dividing the angular frequency ω by the propagation velocity c and the equation (E1). The same applies hereinafter.

In this way, wave number matching is performed to obtain the following function (M4 ″).
Further, using the function (M4 ″), the following equation (M5) or equation (M5 ′) is obtained.

'To the formula (M6) or formula (M6 formula (M5) or (M5)' as represented by) by performing two-dimensional inverse Fourier transform about the wave number _{k x} and wavenumber (E3), image A signal f (x, y) is generated.
The two-dimensional inverse Fourier transform in the calculation of the equations (M6) and (M6 ′) may be performed by performing a fast two-dimensional inverse Fourier transform (IFFT), and a special fast two-dimensional inverse Fourier transform can be used. As a general method, in each of the equations (M6) and (M6 ′), first, a fast inverse Fourier transform for one wave number k _x in the signal band is performed on the other wave number (E3). Then, a fast inverse Fourier transform with respect to the wave number k _x (within the signal band) may be performed on each coordinate of the generated spatial coordinate y (each of the two-dimensional image signal is expressed by Equation (M6) or Faster than calculating according to equation (M6 ′)).

Non-Patent Document 12 does not disclose the formula (M6) using y _S in the formula, but discloses that calculation is performed using y instead of y _S , and correction of coordinates is performed after the calculation. . The correction of the coordinates is performed without approximation processing by performing approximation processing or by multiplying time based on the multiplication of the complex exponential function which is the past invention of the inventor of the present application. Equation (M6) can also be used when the deflection angle is 0 °.

In the apparatus of the present invention, wave number matching is performed together with a two-dimensional inverse Fourier transform or with an inverse Fourier transform in the depth direction without interpolation approximation. That is, the two-dimensional Fourier transform R ″ (k _x , 0, k) calculated in the case of a method (including method (1)) other than the normal migration method (when method (2) is not steering) is used. On the other hand, for the above R (k _x , 0, k) calculated in the normal migration method, first, as represented by the equation (M7) or (M7 ′), Integration for k is performed for each k _x , wave number matching of the wave number (E3) in the depth direction and inverse Fourier transform (IFFT) are performed simultaneously (step S34), and then the lateral (x) direction Perform fast inverse Fourier transform.
Non-Patent Document 12 does not disclose the formula (M7) using y _S in the formula. Equation (M7) can also be used when the deflection angle is 0 °. Similar to the methods (1) to (6), after adding the frequency k components of the spectrum, the inverse Fourier transform (IFFT) with respect to the wave number k _x in the lateral direction is performed, and the calculation can be performed by one inverse Fourier transform. Calculation is fast.

Further, in the process of calculating the formula (M6) and the formula (M7), in the process of calculating the formula (M6) and the formula (M7), when the migration is different from the normal migration (the processing corresponding to the case of no steering in the method (2)). It can be performed. For example, when the deflection plane wave of method (1) is transmitted, first, in step S34, the calculation relating to the wave number (E3) is performed as described above, and in step S35, each result is obtained for position correction. for the function (M8), multiplied by a complex exponential function (M9), carried out thereafter, in step S36, inverse fast Fourier transform relates to lateral wavenumber _{k x} a (IFFT). Alternatively, it may be calculated by multiplying the complex exponential function of the inverse Fourier transform with respect to the wave number k _{x in the} horizontal direction by multiplying the equation (M9), or a dedicated fast inverse Fourier transform may be performed. Equation (M9) can also be used when the deflection angle is 0 °. As described above, the image signal f (x, y) is generated in step S37.
In summary, new processing can be performed using the equation (M6), the equation (M7), or the equation (M7 ′), and the image signal f (x, y) is removed at high speed except for errors due to interpolation approximation. ) Can be generated.

If the same result is obtained without the approximation process without multiplying the equation (M9), the following equation (N4) instead of the equation (M4) is used to calculate the equation (M6) or the equation (M7). good.
That is, in wave number matching, when interpolation approximation is not performed, the wave number in the depth direction shown in the proviso in the equation is used, but the wave number in the depth direction when interpolation approximation is performed propagates the angular frequency ω. It is divided by the speed (E1).
The expression of the wave number in the depth direction expressed in this expression is similar to the expression (13) in the method (1), but in the method (1), kx in the expressions (13) to (15) In the case where the same result is obtained when calculation is performed without using -ksinθ of -ksinθ (as zero), as in the case of performing inverse Fourier transform by multiplying equation (M9) in method (6), paragraph 0204 Before performing the described processing, the equation (16) may be multiplied by the equation (M9). However, the deflection of the plane wave realized by the method (6) is only realized under approximate calculation. Therefore, when the equations (N4) and (M7) are used in the method (6), Although the accuracy is improved without any approximation processing, the accuracy decreases when the equation (M9) is used in the method (1). Further, when the last inverse Fourier transform is performed by a two-dimensional fast inverse Fourier transform (as described later, a three-dimensional fast inverse Fourier transform in the case of three dimensions), when these processes are performed, the calculation speed is The method (6) is faster, but the method (1) is slower (the process described in paragraph 0204 is faster).
In each of these modified methods (1) and (6), when interpolation approximation processing is performed in wave number matching, the same result is obtained using equations (M9) and (N4). The interpolation approximation formula changes correspondingly (described in paragraphs 0354 (A) and (B)).
Further, in each of these modified methods (1) and (6), when interpolation approximation processing is performed in wave number matching, when the above equations (11) and (M3) are used (deflection angle data θ ) And when the same result is obtained when Expressions (11) and (M3) are not used (deflection angle θ is zero), the interpolation approximation expression changes correspondingly (when not used). In paragraphs 0354 (A ′) and (B ′)).
Beam forming in the case of using plane wave transmission is applied to various beam forming as described in the present specification, but the processing described in this paragraph may be used instead in these applications. It should be noted that when receiving dynamic focusing is performed on a beam that has been subjected to transmission beam forming such as that subjected to transmission focusing by applying the method (6), as described later, the angular frequency ω And (M3 ″) expressed using the wave number expressed by using the converted propagation velocity (E1) (formula (M13)) instead of the formula (M3), −ksinθ in the interpolation approximation formula _For the wave number k of _t , it is necessary to use the equation (M13) instead.
In each of the method (1) and the method (6), the methods described in this paragraph may be performed in combination. For example, in the method (6), wave number matching is performed in the same manner as the method of J.-y. Lu et al. (See paragraph 0197, the equation is described in (C ′) of paragraph 0354) that performs interpolation approximation in method (1). Can be performed through interpolation approximation, and the first two-dimensional Fourier transform and the last two-dimensional inverse Fourier transform can be performed by a high-speed two-dimensional Fourier transform (described in (D ′) of paragraph 0354, as described later). 3D fast Fourier transform in the case of 3D). In each of these, there is a case where Expression (11) is used (deflection angle data θ is used) and an expression (M3) is used (described in each of (C) and (D) of paragraph 0354). Of course, it can be used even when it is not deflected.
As described above, the plane wave transmission based on the method (1) and the method (6) is applied to various beam forming.

  Here, the description has mainly been given of performing the beam forming at the time of plane wave transmission with and without steering in the method (1) at high speed without interpolation approximation in wave number matching using the migration method. Method (2) (monostatic aperture synthesis method including the case of steering), method (3) (multistatic method with or without steering), method (4) (transmission fixed focus with or without steering), and All the beam forming described in each of the methods (5) (Beam forming in a polar coordinate system or an arbitrary orthogonal coordinate system) can be similarly performed. The same processing can be performed when the deflection angle differs between transmission and reception. Apodization may be performed as well.

  The same process can be applied to the three-dimensional case. When the received signal obtained using the two-dimensional aperture element array is expressed as r (x, y, z, t), the received signal at the aperture element array position (y = 0) is r (x, y = 0, z, t).

First, as shown in the equation (M′2), the received signal is subjected to a three-dimensional Fourier transform with respect to time t, lateral direction x, and elevation direction z (three-dimensional fast Fourier transform is good).
Here, k = ω / c.

Generally, the received signal is subjected to fast Fourier transform (FFT) with respect to time t at each position coordinate (x, 0, z) to obtain a spectrum R (x, 0, z, k) of the analysis signal. It is done. Then, in each frequency coordinate in the band k, fast Fourier transform is performed with respect to the horizontal direction x and the elevation direction z to obtain R (k _x , 0, k _z , k) (each of the three-dimensional spectra Faster than calculating according to equation (M′2)).

When plane waves are not deflected and transmitted, the above calculation may be performed, but when a zero or non-zero deflection angle formed by a plane wave transmission direction and an axial direction is expressed using an elevation angle θ and an azimuth angle φ. Needs to be trimmed, and for this purpose, R ′ (x, 0, z, k) after the fast Fourier transform for time t is multiplied by a complex exponential function (M′3) (fast Fourier for time t). Conversion and multiplication of complex exponential functions can be calculated directly at once, or a dedicated fast Fourier transform that can do such calculations is also useful).

Then, a fast Fourier transform (FFT) is performed on the received signal in the lateral direction x. The result is R ″ (k _x , 0, z, k). By the way, even if it is programmed so that trimming can be performed, a case where a plane wave is transmitted without deflection (steering angle 0 °) can be processed.

Next, wave number matching (or mapping) is performed. In the case of the methods (1) to (5) other than the normal migration (when the steering is not performed in the method (2)), the propagation speed c and the coordinate system (x _s , y _s , z _s ) are set. Processing is performed by replacing the propagation velocity (E′1) and the coordinate system (E′2) for each beamforming.

For the 3D Fourier transform R ″ (k _x , 0, z, k) calculated in the case of methods other than normal migration (when method (2) is not steering) (including method (1)) Or the above approximation R (k _x , 0, z, k) calculated in normal migration, bi-linear using the nearest angular spectrum of frequency coordinates Through the interpolation etc., wave number matching represented by the equation (M′4) or the equation (M′4 ′) is performed, respectively.
However, when the received signal is a reflected signal, s = 2, and when the received signal is a transmitted signal, s = 1.
However, when interpolation approximation is not performed in the wave number matching of the equations (M′4) and (M′4 ′), the wave number in the depth direction represented in the proviso in each equation is used. The wave number in the depth direction in the case of performing is obtained by dividing the angular frequency ω by the propagation velocity c and the equation (E′1). The same applies hereinafter.

In this way, wave number matching is performed to obtain the next function (M′4 ″).
Further, using the function (M′4 ″), the following equation (M′5) or equation (M′5 ′) is obtained.

For the equation (M′5) or (M′5 ′), the wavenumbers k _x and k _z as represented by the equation (M′6) or the equation (M′6 ′) An image signal f (x, y, z) is generated by performing a three-dimensional inverse Fourier transform on the wave number (E′3).

The three-dimensional inverse Fourier transform in the calculation of the equations (M′6) and (M′6 ′) may be performed by performing a fast three-dimensional inverse Fourier transform (IFFT), and using a special fast three-dimensional inverse Fourier transform. However, as a popular method, in each of the equations (M′6) and (M′6 ′), first, for the two wave numbers k _x and k _z in the signal band, Perform fast inverse Fourier transform on the other wave number (E′3), and then, for each coordinate of the generated spatial coordinate y, fast inverse Fourier transform on wave numbers k _x and k _z (in the signal band) (It is faster than calculating each of the three-dimensional image signals according to the equation (M′6) or the equation (M′6 ′)).

In the apparatus of the present invention, wave number matching is performed together with a three-dimensional inverse Fourier transform or with an inverse Fourier transform in the depth direction without interpolation approximation. That is, the three-dimensional Fourier transform R ″ (k _x , 0, k _z ,) calculated in the case of a method (including method (1)) other than the normal migration method (without steering in method (2)). k) or the above R (k _x , 0, k _z , k) calculated in the normal migration method, expressed by the equation (M′7) or (M′7 ′). First, the integration with respect to k is performed for each (k _x , k _z ) in the band, and the wave number matching of the wave number (E′3) in the depth direction and the inverse Fourier transform (IFFT) are performed. Performed simultaneously, followed by fast inverse Fourier transform in the lateral (x) direction and elevation (z) direction.

Non-Patent Document 12 does not disclose formulas (M′6) and (M′7) that use y _S in the formula. Both types can also be used when the deflection angle is 0 °. Similarly to the methods (1) to (6), after adding the frequency k components of the spectrum, the inverse Fourier transform (IFFT) is performed on the wave numbers k _x and k _z in the horizontal direction and the elevation direction, and the inverse of 1 degree is performed. The calculation can be performed by Fourier transform, and the calculation is fast.

Furthermore, in the process of calculating the formula (M′6) and the formula (M′7) when the migration is different from the normal migration (the processing corresponding to the case of no steering in the method (2)), the lateral (x) direction And the position in the elevation direction (z) can be corrected. For example, when the deflection plane wave of the method (1) is transmitted, first, as described above, the calculation regarding the wave number (E′3) is performed, and the function (M′8) obtained as a result for each position correction. Is multiplied by a complex exponential function, and then fast inverse Fourier transform (IFFT) is performed with respect to wave numbers k _x and k _{z in} the horizontal and elevation directions.
In summary, new processing can be performed using the equation (M′6), the equation (M′6 ′), the equation (M′7), or the equation (M′7 ′). The image signal f (x, y, z) can be generated at high speed except for errors.

In the case of obtaining the same result without approximation processing without multiplying the complex exponential function corresponding to the two-dimensional expression (M9), the following expression (N′4) is used instead of the expression (M′4). Is used to calculate the equation (M6) or the equation (M7).
That is, in wave number matching, when interpolation approximation is not performed, the wave number in the depth direction shown in the proviso in the equation is used, but the wave number in the depth direction when interpolation approximation is performed propagates the angular frequency ω. It is divided by the speed (E′1).
The expression of the wave number in the depth direction expressed in this expression is similar to the expression (C22) in the method (1), but in the method (1), kx in the expressions (C22) and (C23) If the same result is obtained when (without zero) -ksinθcosφ and -ksinθsinφ of -ksinθcosφ and kz-ksinθsinφ is obtained, the complex corresponding to equation (M9) in the two-dimensional case in method (6) Similar to the case of performing an inverse Fourier transform by multiplying by an exponential function, the multiplication may be performed while performing the processing described in paragraph 0207. However, the deflection of the plane wave realized by the method (6) is only realized under approximate calculation. Therefore, as in the two-dimensional case, the expression (N′4) in the method (6) is used. And the equation (M7), the accuracy is improved without any approximation processing. However, when the complex exponential function corresponding to the equation (M9) in the two-dimensional case is used in the method (1), the accuracy is descend. Further, when the last inverse Fourier transform is performed by the three-dimensional fast inverse Fourier transform, if these processes are performed, the calculation speed is increased in the method (6) as in the two-dimensional case. The method (1) is slow (the processing described in paragraph 0204 is fast).
Further, in each of these modified methods (1) and (6), when an interpolation approximation process is performed in wave number matching, a complex exponential function corresponding to the two-dimensional equation (M9) and the equation (N When the same result is obtained using '4), the interpolation approximation formula changes correspondingly as described in the two-dimensional case (described in each of paragraphs 0354 (A) and (B)).
Further, in each of these modified methods (1) and (6), when interpolation approximation processing is performed in wave number matching, when the above equations (C21) and (M′3) are used (deflection angle) The case where the same result is obtained when the data θ and φ are used) and when the equations (C21) and (M′3) are not used (all the deflection angles θ and φ are set to zero) are also two-dimensional cases. Similarly, the interpolation approximation formula changes correspondingly (the case where it is not used is described in each of paragraphs (A ′) and (B ′) of paragraph 0354).
Beam forming in the case of using plane wave transmission is applied to various beam forming as described in the present specification, but the processing described in this paragraph may be used instead in these applications. As in the case of the two-dimensional case, it should be noted that when receiving dynamic focusing is performed on an object subjected to arbitrary transmission beam forming such as transmission focused by applying the method (6). As will be described later, (M′3 ″) expressed using the wave number (formula (M′13)) expressed using the angular frequency ω and the converted propagation velocity (E′1) is expressed by the formula (M Since it is used instead of '3), it is necessary to use the equation (M'13) instead for the wave number k of -ksinθ ₁ (cosφ ₁ x + sinφ ₁ z) in the interpolation approximation formula.
In each of the method (1) and the method (6), the methods described in this paragraph may be performed in combination. For example, in the method (6), wave number matching is performed in the same manner as the method of J.-y. Lu et al. (See paragraph 0197, the equation is described in (C ′) of paragraph 0354) that performs interpolation approximation in method (1). Can be performed through interpolation approximation, and the first three-dimensional Fourier transform and the last three-dimensional inverse Fourier transform can be performed by fast Fourier transform (described in paragraph (D ′) of paragraph 0354). In each of these, there are cases where the expression (C21) is used (the deflection angle data θ is used) and the expression (M′3) is used (described in each of (C ′) and (D ′) of the paragraph 0354). . Of course, it can be used even when it is not deflected.
As described above, the plane wave transmission based on the method (1) and the method (6) is applied to various beam forming.

  Also in this migration method, monostatic or multistatic aperture plane synthesis can be performed without performing interpolation approximation processing in wave number matching in the same manner as the methods (2) and (3).

In the case of monostatic aperture plane synthesis, if the software transmission deflection angle and reception angle are θt and θr, respectively, the ultrasonic angular frequency ω ₀ and the propagation velocity c are used instead of the equation (M3). Wave number
Represented using
In the equation (M7 ′) in the case where no interpolation processing is required in the wave number matching of the normal migration processing,
However, when the received signal is a reflected signal, s = 2, and when the received signal is a transmitted signal, s = 1.
What should I do?

In the three-dimensional case, suppose that the deflection angles of the transmission beam and the reception beam are expressed using (elevation angle, azimuth angle) = (θ _t , φ _t ) and (θ _r , φ _r ), respectively. Similarly to the method (2), the wave number matching is first performed in the lateral direction by multiplying the complex exponential function (formula (D41)) expressed using the carrier frequency ω ₀ of the ultrasonic signal, and the depth y With respect to the direction, in order to have resolution in the depth y direction, the complex exponential function (formula (D42)) excluding the horizontal matching process (formula (D41)) is multiplied, and at the same time, the complex exponential function (formula (D43) )). That is, the expression (D41) is used instead of the expression (M3 ′) in the case of the two dimensions, and the product of the expression (D42) and the expression (D43) is used instead of the expression (M11).

  As described above, the migration processing according to the present invention corresponding to the method (2) and the method (3) based thereon is equivalent to the method (2) and the method (3).

Also in these cases, as in the normal migration process, it is possible to perform a fast inverse Fourier transform by performing an interpolation process in wave number matching. In this case, the method (2) and a method based on this ( 3) is not equivalent, and after the above processing using the equation (M3 ′), etc., instead of the equation (M4 ′) that is wave number matching with the interpolation processing, based on the equation (M11),
However, when the received signal is a reflected signal, s = 2, and when the received signal is a transmitted signal, s = 1. When interpolation approximation is not used in wave number matching, the wave number in the depth direction shown in the proviso in the formula is used, but the wave number in the depth direction when interpolation approximation is performed is based on the angular frequency ω as the propagation speed. divided by c. The same applies hereinafter.
Whether the two-dimensional inverse Fourier transform (formula (M6 ′)) of the formula (M5 ′) represented using the same ky of (M4 ′ ″) is performed. Or instead of the formula (M4 ′)
However, when the received signal is a reflected signal, s = 2, and when the received signal is a transmitted signal, s = 1. When interpolation approximation is not used in wave number matching, the wave number in the depth direction shown in the proviso in the formula is used, but the wave number in the depth direction when interpolation approximation is performed is based on the angular frequency ω as the propagation speed. divided by c. The same applies hereinafter.
Equation (M4 ″) is obtained by performing wave number matching with interpolation processing expressed as follows, and in equation (M5 ′) expressed using the same ky of (M4 ″ ″),
The two-dimensional inverse Fourier transform (corresponding to the equation (M6 ′)) may be performed.

  Also in this case, multistatic aperture synthesis is performed in the same manner as when method (3) is realized by applying method (2), and instead of method (2), monostatic by this migration method This can be realized by applying the aperture synthesis method.

The same process can be applied to the three-dimensional case. That is, after processing using the equation (M′3 ′) in the case of the three dimensions, instead of the equation (M′4 ′) that is wave number matching with the interpolation processing, the equation (D42) and the equation ( D43) product (corresponding to (M11) in the case of two dimensions)
However, when the received signal is a reflected signal, s = 2, and when the received signal is a transmitted signal, s = 1. When interpolation approximation is not used in wave number matching, the wave number in the depth direction shown in the proviso in the formula is used, but the wave number in the depth direction when interpolation approximation is performed is based on the angular frequency ω as the propagation speed. divided by c. The same applies hereinafter.
The expression (M′4 ″) represented by the following equation is obtained, and the three-dimensional inverse Fourier transform (expression (M′4 ′)) of the expression (M′5 ′) represented by using the same ky of (M′4 ′ ″). 6 ′)) or instead of the formula (M′4 ′)
However, when the received signal is a reflected signal, s = 2, and when the received signal is a transmitted signal, s = 1. When interpolation approximation is not used in wave number matching, the wave number in the depth direction shown in the proviso in the formula is used, but the wave number in the depth direction when interpolation approximation is performed is based on the angular frequency ω as the propagation speed. divided by c. The same applies hereinafter.
Equation (M′4 ″) is obtained by performing wave number matching with interpolation processing expressed as follows, and the equation (M′5 ′) expressed using the same ky of (M′4 ″ ″) )
And a three-dimensional inverse Fourier transform (corresponding to the equation (M′6 ′)) may be performed.

  In this case, the multistatic aperture plane synthesis is performed in the same manner as when the method (3) is realized by applying the method (2), and the monostatic aperture plane by this migration method is used instead of the method (2). It can be realized by applying the synthesis method.

  Based on these migration methods, all the beam forming described in the methods (2) and (3) can be similarly performed.

  Further, any beam such as a fixed focus beam of the method (4) can be used without performing interpolation approximation in wave number matching using the migration process (formula (M7), etc.) at the time of plane wave transmission corresponding to the method (1). In addition, beam forming during transmission of arbitrary waves (including waves that have not been beam-formed), superposition processing during transmission of multiple beams and waves, and processing during simultaneous transmission of multiple beams and waves can be performed. . A plurality of beam forming operations may be performed using a multidirectional aperture surface synthesis method, and in this case as well, it is performed at high speed in the same manner. It is not limited to those. In these cases, as in the case of using the method (1), as a combination with the method (2), the deflection dynamic focusing of reception can be performed for an arbitrary transmission beamforming.

When the physical transmission deflection angle of the focus beam is A, if each of the soft transmission deflection angle and the reception angle is θ (= θt) and θr, the angular frequency ω is expressed in place of the equation (M3). Wave number expressed using reduced propagation velocity (E1)
Represented using
, And when the physical transmission deflection angle of the plane wave is A and the soft transmission deflection angle and the reception angle are θ (= θt) and θr, respectively, instead of the equation (M3) In addition,
Are used in the same manner, and in formula (M7):
What should I do?

In the case of a three-dimensional case, the same processing can be performed. When the physical transmission deflection angle of the focus beam is expressed by an elevation angle A and an azimuth angle B (including the case where at least one of the angles is zero degrees), a soft transmission deflection angle (elevation angle θ ₁ and When steering is performed at an azimuth angle φ ₁ ) and steering dynamic focusing is performed at a deflection angle (elevation angle θ ₂ , azimuth angle φ ₂ ) (including a case where at least one of the angles is zero degrees), an expression Wave number expressed using angular frequency ω and converted propagation velocity (E′1) instead of (M′3)
Represented using
, And when the plane wave physical transmission deflection angle is expressed by an elevation angle A and an azimuth angle B (including the case where at least one of the angles is zero degrees), the soft transmission deflection angle Steering at (elevation angle θ ₁ and azimuth angle φ ₁ ) and steering dynamic focusing at deflection angles (elevation angle θ ₂ , azimuth angle φ ₂ ) (including the case where at least one of the angles is zero degrees) ) In place of formula (M′3)
Are used in the same manner, and in formula (M′7):
What should I do?

Also in this case, it is possible to perform fast inverse Fourier transform by performing interpolation processing in wave number matching, as in the case of normal migration processing, and in this case, an equation that is wave number matching with interpolation processing is used. Instead of (M4), based on the formula (M11 ′ ″)
However, when interpolation approximation is not used in wave number matching, the wave number in the depth direction shown in the proviso in the formula is used. It is divided by the speed (E1). The same applies hereinafter.
Whether the two-dimensional inverse Fourier transform (formula (M6)) of formula (M5) represented using the same ky of (M4 ′ ″ ″) is performed. Or instead of formula (M4)
However, when interpolation approximation is not used in wave number matching, the wave number in the depth direction shown in the proviso in the formula is used. It is divided by the speed (E1). The same applies hereinafter.
Equation (M4 '') is obtained by performing wave number matching with interpolation processing expressed as follows, and in equation (M5) expressed using the same ky of (M4 ''''''),
The two-dimensional inverse Fourier transform (corresponding to equation (M6)) may be performed.

In the above, if each of the expressions (M3 ″) and (M3 ′ ″) is exchanged, the image forming position is shifted when soft transmission steering is performed (when θt is non-zero). Produce. In these processes, the wave number represented by using the ultrasonic angular frequency ω ₀ and the converted propagation velocity (E1) instead of the equation (M10) which is the wave number corresponding to the ultrasonic frequency.
When soft reception steering is performed (when θr is non-zero), an error (deflection angle of 20 °) is generated where the generated deflection angle is larger than when using the equation (M10). In this case, an image is obtained.

In the case of a three-dimensional case, the same processing can be performed. That is, after processing using the equation (M′3 ″) in the case of the three-dimensional case, the equation (M′11 ″) is used instead of the equation (M′4) that is wave number matching with interpolation processing. ')On the basis of the,
However, when interpolation approximation is not used in wave number matching, the wave number in the depth direction shown in the proviso in the formula is used. It is divided by the speed (E′1). The same applies hereinafter.
And a three-dimensional inverse Fourier transform of the equation (M′5) expressed by using the same ky of (M′4 ′ ″ ″) (the equation (M '6)) or instead of formula (M'4)
However, when interpolation approximation is not used in wave number matching, the wave number in the depth direction shown in the proviso in the formula is used. It is divided by the speed (E′1). The same applies hereinafter.
Equation (M′4 ″) is obtained by performing wave number matching with the interpolation processing expressed as follows, and the equation (M′4 ′) expressed using the same ky of (M′4 ″ ″ ″) 5)
The two-dimensional inverse Fourier transform (corresponding to equation (M′6)) may be performed.

In the above description, if each of the expressions (M′3 ″) and (M′3 ′ ″) is exchanged, processing is performed when soft transmission steering is performed (when the deflection angle is non-zero). An error occurs in the image position. In these processes, the wave number represented by using the ultrasonic angular frequency ω ₀ and the converted propagation velocity (E ′ 1) instead of the equation (M ′ 10) that is the wave number corresponding to the ultrasonic frequency.
When a soft reception steering is performed (when the deflection angle is non-zero), an error is generated in which the generated deflection angle is larger than when the equation (M′10) is used. However, imaging is obtained.

In this case, when the migration method based on the equation (N4) described in paragraph 0316 is used, when the physical transmission deflection angle of the focus beam is A, the soft transmission deflection angle and the reception angle Is represented by using the wave number (M13) represented by using the angular frequency ω and the converted propagation velocity (E1) instead of the equation (M3) (M3 ′). )) And when the physical transmission deflection angle of the plane wave is A, and the software transmission deflection angle and reception angle are θ (= θt) and θr, respectively, the equation (M3) Instead of (M3 ′ ″), the following formula (N4 ′) may be used in the same way in the formula (M6) or (M7) instead of the formula (N4).
However, when interpolation approximation is not performed in wave number matching, the wave number in the depth direction shown in the proviso in the equation is used, and the wave number in the depth direction when interpolation approximation is performed is obtained by converting the angular frequency ω to the converted propagation velocity ( Divided by E1). The same applies hereinafter.

In the case of the three-dimensional case (when the migration method based on the formula (N′4) described in paragraph 0331 is used), the same processing can be performed. When the physical transmission deflection angle of the focus beam is expressed by an elevation angle A and an azimuth angle B (including a case where at least one of the angles is zero degrees), a soft transmission deflection angle (elevation angle θ ₁ and When steering is performed at an azimuth angle φ ₁ ) and steering dynamic focusing is performed at a deflection angle (elevation angle θ ₂ , azimuth angle φ ₂ ) (including the case where at least one of the angles is zero degrees), the formula In place of (M′3), the equation (M′3 ″) expressed using the wave number (M′13) expressed using the angular frequency ω and the converted propagation velocity (E′1) is similarly applied. When a plane wave physical transmission deflection angle is expressed by an elevation angle A and an azimuth angle B (including a case where at least one of the angles is zero degree), a soft transmission deflection angle (elevation angle θ) is used. ₁ and azimuth angle phi ₁₎ steering to the deflection angle at (elevation theta _2, the azimuth angle In the case of performing the steering dynamic focusing in ₂₎ (including those which are the zero either at least one angle), instead of equation (M'3), similarly formula (M'3 ''') In the formula (M′6) or (M′7), the following formula (N′4 ′) may be similarly used instead of the formula (N′4).
However, when interpolation approximation is not performed in wave number matching, the wave number in the depth direction shown in the proviso in the equation is used, and the wave number in the depth direction when interpolation approximation is performed is obtained by converting the angular frequency ω to the converted propagation velocity ( Divided by E′1). The same applies hereinafter.

  In this manner, beam forming based on these migration methods can be performed with or without performing interpolation approximation processing in wave number matching in the same manner as the methods described in paragraphs 0316 and 0331.

Further, the processing described in paragraphs 0316 and 0331 with respect to method (1) is a combination of method (1) and method (2) (when receiving deflection dynamic focusing is performed in method (1) described in paragraphs 0235 to 0238). ) In the same manner. That is, in the two-dimensional case, when the same result is obtained when the deflection angle θ in the equations (F42) and (F43) is calculated to be zero, the method (6) is multiplied by the equation (M9) and reversed. Similar to the case of performing the Fourier transform, the formula corresponding to the formula (16) may be multiplied by the formula (M9) before the processing described in the paragraph 0204 is performed. In the case of the three-dimensional case, when the same result is obtained when all the deflection angles θ and φ in the equations (G22) and (G23) are calculated to be zero, the case of the two-dimensional case in the method (6) As in the case of performing the inverse Fourier transform by multiplying the complex exponential function corresponding to the equation (M9), the multiplication may be performed while performing the processing described in paragraph 0207.
These beam forming can also be performed with or without interpolation processing in wave number matching as described in paragraphs 0316 and 0331. Others are as described in the same paragraph.

  Based on these migration methods, all the beam forming described in the method (4) can be similarly performed.

  Further, as described in the method (5), when transmission / reception is performed in an orthogonal coordinate system such as a polar coordinate system other than a Cartesian coordinate system, the expressions (M6), (M6 ′), ( It is possible to obtain the result directly in the Cartesian coordinate system by calculating the M7) and the equation (M7 ′) obtained by performing the Jacobian operation and performing the beam forming described above. In the case of the three-dimensional case, Jacobian calculation is similarly applied to the expressions (M′6), (M′6 ′), (M′7), and (M′7 ′) in the same manner. Can be processed. In addition, all beam forming described in the method (5) can be similarly performed.

One of the objects of the present invention is to realize high-speed and high-accuracy beam forming on the basis of Fourier transform, and performs interpolation approximation using the above methods (1) to (6). Any processing that does not exist can be modified and used for processing with various forms of interpolation approximation, and may be used at a higher speed, although the accuracy is reduced. Whether the wave number matching in at least one direction or two directions among all three directions of the horizontal direction, the elevation direction, and the depth direction is approximated or whether multiplication of complex exponential functions is used, etc. It is possible to modify and use the method. If many approximations are performed, the speed can be increased, but the accuracy decreases. Some of the descriptions so far have already been described. In this paragraph, (A), (A ′), (B), (B ′), (C), (C ′), (C) described in paragraphs 0316 and 0331 regarding the two-dimensional and three-dimensional cases. Interpolation approximation formulas are shown for the eight cases of D) and (D ′).
For example, the same processing can be performed when plane wave steering is performed by the migration method of method (6), and interpolation approximation is performed for wave number matching in all directions (corresponding to (D ′)), and interpolation approximation is performed by method (1). Similar to the method of J.-y. Lu et al. (Refer to paragraph 0197, corresponding to (C ′)) for processing, the calculation is the fastest when migration is used. However, accuracy is the lowest in migration. On the other hand, in the method of J.-y. Lu et al. (Refer to paragraph 0197, corresponding to (C ′)), for example, if only horizontal wave number matching is performed before Fourier transformation, the accuracy is improved. Decreases (corresponds to (C)). In addition, including the cases of (A), (A ′), (B), and (B ′), an interpolation process (expression) in the case of two dimensions (paragraph 0316) is shown below (in the case of three dimensions (paragraph 0331). ) Is also expressed in the same way, abbreviated) Note that (A), (A ′), (C), and (C ′) are expressed according to the equations (7) and (8). In (B ′) and (D ′), the inverse Fourier transform in the horizontal direction is performed not on kx but on kx ′.
The wave number k _y in the depth direction when interpolation approximation is performed in wave number matching is obtained by dividing the angular frequency ω by the propagation velocity c, but can be processed as described above when interpolation approximation is not performed.
The wave number k _y in the depth direction when interpolation approximation is performed in wave number matching is obtained by dividing the angular frequency ω by the propagation velocity c, but can be processed as described above when interpolation approximation is not performed.
However, when interpolation approximation is not used in wave number matching, the wave number in the depth direction shown in the proviso in the formula is used. It is divided by the speed (E1).
However, when interpolation approximation is not used in wave number matching, the wave number in the depth direction shown in the proviso in the formula is used. It is divided by the speed (E1).
The wave number k _y in the depth direction when interpolation approximation is performed in wave number matching is obtained by dividing the angular frequency ω by the propagation velocity c, but can be processed as described above when interpolation approximation is not performed.
The wave number k _y in the depth direction when interpolation approximation is performed in wave number matching is obtained by dividing the angular frequency ω by the propagation velocity c, but this is one of the present invention. According to (1), the processing can be performed as described above.
However, when interpolation approximation is not performed in wave number matching (one of the methods (6)), which is one aspect of the present invention, the wave number in the depth direction represented in the proviso in the equation is used. The wave number in the depth direction when performing the above is obtained by dividing the angular frequency ω by the converted propagation velocity (E1).
However, when interpolation approximation is not used in wave number matching, the wave number in the depth direction shown in the proviso in the formula is used. It is divided by the speed (E1).
Also in these cases, the method (2) may be used in combination in the reception beam forming.
It is important to perform the first multidimensional Fourier transform and the multidimensional inverse Fourier transform at high speed, and various fast Fourier transform algorithms can be appropriately used. In addition, both physically and mathematically, wave number matching can be performed during the first Fourier transform, and wave number matching can be performed during the last inverse Fourier transform. In addition, all other than the beam forming described in this specification (method (1) to method (6), etc.) can be similarly realized without interpolation approximation processing or processing through the approximation processing. When performing interpolation approximation processing, the sampling frequency may be increased in order to increase the accuracy. However, unlike the case where a signal at an arbitrary position can be generated without interpolation approximation processing, the number of data of the Fourier transform increases. You need to be careful. However, even when the interpolation approximation process is not performed, it is important to realize a situation where the signal is processed with a moderate oversampling and a signal having a high SN ratio.
In such a case, even when based on the migration process (method (6)), the beam forming described in the methods (1) to (5) (a collective reception signal at the time of simultaneous transmission of a plurality of different beams or waves) The beam forming of the received signal for each transmission, including the case of using a virtual source and a virtual receiver, and the like can be performed with or without interpolation approximation.

Method (7): Others The above methods (1) to (6) have mainly been described for the case of using a one-dimensional array. However, in the case of a two-dimensional array or a three-dimensional array, the method is as described above. In each case, the processing performed in the lateral direction may be similarly performed in the other one or the other two axial directions. These can be implemented in all orthogonal coordinate systems, including orthogonal coordinate systems. That is, the above methods (1) to (6) may be simply extended to higher order dimensions. Further, during the processes of the methods (1) to (6) and the method (7) described herein, a DC component or a low frequency component in the horizontal direction or the vertical direction may be generated. It is advisable to perform zero padding of the spectrum at the stage before the inverse Fourier transform. When digital signal processing is started, analog processing or digital processing is performed as a preprocessing to cut off direct current, but the spectrum may be zeroed in the angular spectrum.
In addition, when digital Fourier transform is performed, the upper and lower boundaries of the region of interest are assumed in order to assume the periodicity (that is, cyclicity) of the distribution of the raw signal before processing and the processed image signal in a finite spatial region. Etc. (mainly the boundary in the direction parallel to the surface of the physical aperture element array, the boundary traveling in the so-called lateral direction or the elevation direction, etc.), the other side surface, the boundary in the vertical direction, etc. (mainly the surface of the physical aperture element array A raw signal component before processing or an image signal after processing may appear to circulate around a boundary in a direction orthogonal to the boundary or a boundary traveling in a so-called axial direction.
In both the case of the reflected wave target and the case of the transmitted wave target, the signal intensity decreases due to the phenomenon of diffusion, attenuation, scattering, and reflection as it propagates away from the transmission aperture surface. Have such a raw signal, the upper and lower boundaries of those regions of interest (mainly boundaries parallel to the plane of the physical aperture element array or boundaries that run in the so-called lateral and elevation directions) Etc.) may not be a problem, but it is a problem when the intensity of the raw signal is not small at the upper and lower parts. When the reception aperture is different from the transmission aperture for the transmitted wave, the signal strength at the reception aperture position may be a problem. In such a case, the region of the zero signal (strictly speaking, the distance between the upper and lower parts) is measured in the direction of approaching the length of the transmission aperture from the upper part of the region of interest (length direction) to the region of interest of the raw signal. A region with a length) or a zero signal region (strictly, a region with a distance between the top and bottom) in the direction away from the transmission aperture surface (length direction) from the bottom of the region of interest In addition, after processing the region of interest in a direction away from the transmission aperture and reception aperture (length direction), the image signal obtained in the added region is discarded or the raw signal is still in a discontinuous state. Therefore, instead of emphasizing the image signal obtained by processing the raw signal by applying a so-called window in the length direction in the vicinity of the bottom of the window.
On the other hand, on other side surfaces, vertical boundaries, etc. (mainly boundaries in a direction perpendicular to the surface of the physical aperture element array or boundaries that run in the so-called axial direction), raw signals representing different spatial positions are used. The image signal is synthesized, and the raw signal is often strong, and in most cases, the same phenomenon (artifact) becomes a problem. In such a case, the region of interest of the raw signal is separated from the region of interest (width direction) from at least one of the two boundaries that form a pair of the side or vertical boundary of the region of interest. The image signal obtained in the region added after processing the region of interest by extending the region of interest in the horizontal direction by adding the zero signal region (strictly, the region having the larger effective aperture width for transmission or reception) to However, since the raw signal has a discontinuous state, instead of processing the raw signal by applying a so-called width window, the image signal obtained near the bottom of the window may not be emphasized. is there. In the case of three dimensions, the windows are multidimensional in the lateral direction and the elevation direction, so-called separable windows or non-separable windows. Even when steering is not performed, there is a problem, but when steering processing is performed, the processing is often necessary.
It may be useful to perform these processes simultaneously. When using windows, the windows are multidimensional, so-called separable or non-separable windows. In addition, in the image signal obtained without performing such processing, when there is an image signal that appears in a cyclic manner, the region of the image signal may be excluded from the region of interest.

In beam forming using other Fourier transforms described in Non-Patent Document 9 or the like, the method disclosed in the methods (1) to (7) can be used, and the same effect can be obtained. .
For example, Section 2.4 of Non-Patent Document 9 discloses a method for calculating an arbitrary beam or wave using a general solution (green function) of a wave equation. There, spherical waves, cylindrical waves, and plane waves are handled as examples for analytical calculation. As a feature using the Green function, the signal to be obtained is in the denominator in the frequency domain,
have. Using this method, calculation can be performed using a Green function in a cylindrical coordinate system, a spherical coordinate system, or any other orthogonal coordinate system.
That is, in the method or formula disclosed in the methods (1) to (7) (when the interpolation approximation is not performed in the wave number matching), the spectrum of the signal to be obtained is expressed by the formula (GR1) or (GR2) in the denominator. It may be calculated in a situation with The methods and formulas described in the methods (1) to (7) can be applied to various other methods and beam forming.
In these cases using the Green function, a point source can be considered, which is suitable for representing a virtual source (Patent Document 7 or Non-Patent Document 8) set before and after the physical aperture. In that case, the processing for the actual radiation pattern of the physical aperture (element) described in the next paragraph is important.

  In addition, the present methods (1) to (7) can be applied, for example, with a calculation in consideration of the radiation pattern of the aperture (element) described in Section 3.2 of Non-Patent Document 9. In that case, signal strength may be appropriately corrected by physical or soft apodization, and signal processing may be performed. As described many times in this specification, for example, ISAR (the motion of the observation target may be applied), nonlinear processing, adaptive beamforming (Non-Patent Document 10), and other various processing are also performed. In some cases, high resolution (in particular, a direction orthogonal to the propagation direction) and high contrast are suppressed by suppressing side lobes. The coherent factor etc. which exist in nonpatent literature 11 etc. are applicable. Further, the present invention is not limited to these, and apodization (which may also serve as a delay using a complex signal) is appropriately performed. The apodization includes a case where the apodization is variable not only in the propagation direction but also in the scanning direction.

  In addition, the methods (1) to (7) can be used when transmission or reception apertures at various positions are used or when performing various other beam forming. For example, Non-Patent Document 9 provides abundant examples. For example, there are descriptions such as Geophysical Imaging (for example, pay attention to the form of Equation 7.9 to 7.12) and so-called X-ray CT (Computed Tomography) in Section 7.3. In addition, the present methods (1) to (7) can be used. Also noteworthy are FIG. 7.3 and Equations 7.5 to 7.9 disclosed in the case of transmission imaging described in Section 7.2 of Non-Patent Document 9. In these, processing can be performed without performing interpolation approximation processing including wave number matching or the like (in which interpolation interpolation processing is sometimes performed).

  In addition, the present methods (1) to (7) are predetermined biplanes, multiple planes, planes or tomographic planes extending in a desired arbitrary direction (in which, planes, tomographic planes and the like are not necessarily flat but curved surfaces). Or an image signal that is not a plane but a line (a line is a straight line or a curve) can be selectively and directly generated. For example, while images can be presented based on three-dimensional or two-dimensional image signals, images may be presented based on those image signals, or those images may be presented independently. Is possible. In signal processing, these image signals and images may be presented through interpolation approximation. In these, measurement data such as displacement, strain, temperature, etc. measured based on the image signal or image may be displayed independently or may be displayed superimposed on those images.

  As described herein multiple times, apodization can be determined and implemented in various ways. There are various adaptive beam forming, minimum variance beam forming, Capon method, etc. described in Non-Patent Document 10 and the like. In these, when the covariance matrix is regularized, a parameter (regularization parameter) for adjusting the degree of regularization can be appropriately determined at each position based on the signal-to-noise ratio of the signal at each position. It is possible to process spatially variants. It is also possible to use other positive definite operators such as gradient operators and Laplacians instead of using unit matrices as regularization operators. The resolution of the image signal can be increased (particularly, the direction orthogonal to the propagation direction), and the contrast can be increased by suppressing the side lobes. Also in the independent component analysis (independent signal separation), it is effective to regularize the covariance matrix in the same manner. These regularization methods have not been disclosed so far. Alternatively, in both processes, the rank is lowered and the process is stabilized based on singular value decomposition or eigenvalue decomposition. These processes are also effective in other methods in beam forming. As described elsewhere, MIMO (Multiple-input and Multiple-output: a wireless communication technology that combines a plurality of antennas on the transmitting side and the receiving side to widen the band of transmission and reception signals) and SIMO (Single-input and Multiple-output) : It is also effective to use a wireless communication technique that uses one antenna on the transmission side and uses a plurality of antennas on the reception side to widen the band of received signals. Further, the inventor of the present application has favored and used absolute value detection and power detection in addition to envelope detection, but the coherence factor described in Non-Patent Document 11 and the like is effective. Absolute value detection and power detection are effective in visualizing the undulation of waves. If absolute value is taken or raised, it will have a high frequency component, especially when the order is high, but brightness may be assigned to the amplitude of the wave itself or color may be assigned for display. Can also be viewed as a biased detector). Non-Patent Document 10 describes various other adaptive beamforming, and also in this specification, MUSIC (Multiple Signal Classification: wireless communication technology using eigenvalues or eigenvectors of a correlation matrix of a received signal), etc. Various processes are described. Further, the effective processing is not limited to this, and there are various other processes. Such various processes can be performed before, during and after beamforming, and can be performed at the level of apodization. In that case, it is extremely effective to perform processing after performing spatiotemporal alignment based on correlation processing (details will be described later).

  In the present invention, in particular, integration processing (calculation) may be performed in the time direction (distance direction) in which the rf data is acquired to improve the signal-to-noise ratio of the signal. This integration processing is also performed by analog processing (so-called integrator) or digital processing (integrator or integration calculation).

  Further, in the above description, calculation of a product with a weight value that has a small amount of calculation and is easy for apodization processing has been described. However, the present invention is not limited to this, and in a linear system, a spatial domain and a frequency domain are calculated. Convolution integration may be performed based on the dual relationship between the product and the convolution integration in. It is possible to appropriately apodize at each depth position or at equal distances from each aperture element.

By using the methods (1) to (6) to superimpose multidirectional deflected beams and plane waves generated by the apparatus according to the present embodiment, the above-described lateral modulation signal (image signal) and a wide band in the lateral direction are used. In some cases, a signal (image signal) having a high resolution in the horizontal direction is generated. As in the case of the single transmission, both the physical and / or soft steering operations may be performed in each case, and all the same steering operations may be performed. Although reception beam forming has been described mainly with respect to software, reception beam forming using reception delay and reception apodization may be physically or individually performed as necessary. On the other hand, transmission beam forming has been described centering on physical implementation. For example, a high-speed frame rate can be obtained by transmitting a plane wave or transmitting a plurality of beams or waves, while opening an aperture. In order to perform surface synthesis, transmission may be performed for each element (multidirectional aperture surface synthesis is also possible. Plane wave, cylindrical wave, spherical wave, etc. are transmitted by coding, decoding and aperture surface synthesis. Can also be performed). As described above, transmission and reception can be considered and implemented in terms of software. The plane wave reaches a deeper position than the focus beam (obtained from the deep position by comparing the echo), but the S / N ratio as a wave or beam is compared for the purpose of measuring displacement. And low. In the first place, the horizontal resolution is also low. On the other hand, when multi-directional plane waves are superposed, almost equal lateral resolution can be obtained regardless of the position. On the other hand, when using a focus beam, it is effective to cross beams in multiple directions at the focus position. However, if high lateral resolution is to be obtained at multiple positions, multi-focusing is used. Will be done. In any case, it is possible to achieve beam forming at high speed with respect to a reception signal when a plurality of waves or beams are transmitted at the same time, or a superposition of signals received and transmitted at different times even in the same phase. . In addition, a plurality of waves having different carrier frequencies may be used to generate a signal (image signal) having a wide bandwidth in the axial direction and a high resolution in the axial direction. In these cases, the spectrum may be widened to increase the resolution so that the spectra overlap. The plurality of beams may be generated in parallel at the same time, and the measurement target may be generated at the same time phase but at different times. Multidirectional waves may be generated by the multidirectional aperture plane synthesis described above.
When the deflection angle is increased, the imaging positions of the reflector and the strong scatterer may be spatially shifted. For example, when the deflection angle is transmitted to the front surface of the aperture element and a plane wave is transmitted by changing the deflection angle in small increments (for example, by 1 °) to ± 45 ° and the signals formed by beam formation are superimposed, the aperture opens in the front direction. The case of surface synthesis can be simulated, and a band corresponding to a deflection angle of ± 45 ° cannot be obtained in the horizontal direction (the signal is canceled at the time of superposition). It is natural to consider the case where the beam forming in the front direction is decomposed into a plane wave as an angular spectrum. When widening in the horizontal direction by superposition in space-time or frequency space, not only in the case of deflected plane wave transmission, but also in the case of performing other deflected beam forming, the spectrum does not overlap in the frequency space. Although it is necessary to superimpose, there can be found the cause of the spatial shift of the imaging position. That is, as phase aberration, an error occurs in focusing and propagation direction control due to spatial inhomogeneity of the sound velocity of the medium (depending on temperature and pressure) and particularly in steering with a large steering angle, due to the directivity of the aperture. Therefore, when superimposing signals with a large deflection angle, at the time of transmission at the time of beam forming, or at least one time point after the beam forming, the received signal before receiving beam forming, during receiving beam forming, It may be necessary to perform signal position correction (phase aberration correction). When super-resolution by spectral processing or nonlinear processing of these signals is performed, when superimposing processing (superimposing spectral processing or nonlinear processing, or superposition of spectral processing or nonlinear processing, etc.) is used together, The influence of the position shift on the result (position error, etc.) becomes significant, and such position correction may be important. In addition, the frequency dependence of the converted propagation speed is a factor that causes misregistration, and the same problem may occur when signals of different frequencies are superimposed and may be processed in the same manner. In addition, waveform distortion may occur due to frequency-dependent phase delay or phase change in the device (for example, phase change in the sensor or phase delay in the amplifier in the circuit). There is a case where the waveform is corrected to correct the waveform (it is effective to perform analog shifting of the digital signal that rotates the phase of each signal component by multiplying the complex exponential function for each frequency in the frequency domain). The phase change that occurs in the device is obtained in advance, and the sensor is appropriately electrically driven with the goal of generating a wave having a desired waveform or generating a desired waveform at the observation position or reception position. There is also. Thereby, the observation of the observation target is made highly accurate (various observations using the phase, observations of propagation speed, scattering, attenuation, etc. having frequency dependence). Only the amount that occurs at the receiving device may be corrected. The same processing may be performed for the above-described other misalignment. The position correction is also described in paragraph 0371 and the like. Various signal processing techniques such as motion compensation and phase aberration correction can be used. The signal intensity correction is also described in paragraph 0689. In addition, regarding the beam forming component and the speckle component of the weakly scattered signal, unlike those decisive signals, a virtual sound source or virtual receiver assuming a scatterer invented by the inventors of the present application (Patent Document 7, As confirmed through experiments using Non-Patent Document 8), it can be used for imaging and displacement measurement without performing position correction processing (for example, combined use of plane wave transmission and Gaussian apodization is effective for displacement measurement). In the focusing, a power apodization such as a square function is effective, and the latter has a high resolution even in single beam forming).

  Further, it is different to form a multi-focus (including not only a normal multi-focus that forms a transmission focus at a plurality of positions in the beam propagation direction but also a transmission focus at a plurality of arbitrary positions including the horizontal direction). There may be a case where a plurality of waves focused on the position are transmitted to perform reception beam forming. In addition, processing for generating reception beams at a plurality of positions and reception beams in a plurality of directions may be performed on one transmission beam. In addition, beam forming based on transmission in a plurality of directions with different steering angles may be performed. In addition, there is a case where beam forming is performed at a position where there is little interference, and beam forming is performed at each part divided within one frame on the basis of performing transmission and reception. In some cases, parallel beamforming is performed, such as processing in parallel, and in each case, processing is performed to superimpose the results at each position in the region of interest from which a plurality of beamforming results are obtained. The method (4) itself has a feature that if a wave propagates in the region of interest, it can process the received signal of the interfering wave, and this can be used to realize a high frame rate. (Method (4) is capable of receiving beam forming for any transmission beam, wave, single or multiple transmissions). In addition, beam forming may be performed using an appropriate signal component after performing various signal separation processes. Depending on the degree of interference, processing may be performed without removing waves outside the region of interest.

  In addition, the wave transmission / reception apertures may be dedicated apertures, but they may also serve as both, and not only receive the response of the wave transmitted by themselves, but are transmitted from other apertures. Waves may be received and again the generated beamforming results may be superimposed, including when processed in parallel. In summary, the above superposition is performed at the same time, at the same time, or at the same time or at the same time when the state of the object to be propagated (communication object) or the observation object is the same or substantially the same. In phase, one or more beamforming or transmission or reception may occur at each aperture, and similarly one or more beamforming or transmission or reception may be performed with one combination of apertures. Sometimes done. Similarly, each of a plurality of combinations of apertures may perform one or more beamforming, transmission, or reception. Also, in these cases, when a plurality of beamforming or transmission or reception results are obtained, new data may be generated through the calculation of the superposition thereof.

  Since these superposition processes are linear processes, a plurality of complex spectrum signals having the same frequency in the frequency domain can be superposed in the calculation process of the above methods (1) to (6). In this case, it is only necessary to perform inverse Fourier transform on the superimposed complex spectrum at one time. Processing can be completed faster than necessary. Although not limited to this, such as an incoming wave, what is superimposed in the state of an angular spectrum may be processed in a single direction or a plurality of directions, for example. As the processing itself, it is preferable to perform a Fourier transform by superimposing a plurality of waves in a spatial domain, and obtain a superposed angular spectrum (the effect of performing the Fourier transform only once). In some cases, the position of the object can be confirmed.

  In the above, when transmitting a plurality of beam-formed waves (at least, a predetermined transmission delay is applied and a transmission apodization may be applied) (among methods (1) to (6)) In methods (2) and (3) other than the aperture plane synthesis), the first excited aperture element in the effective aperture array for each wave transmitted when physically transmitted simultaneously Since each received signal is stored in a memory or a storage device (storage medium) in an overlapped state, the image signal generation process for one frame may be performed according to each method. (Parallel processing may be performed in which one frame is divided and processed in each part).

  On the other hand, in the above-mentioned another case where beam forming is performed a plurality of times at different times, in the channel of each receiving aperture element, the timing transmitted from the aperture element that is excited first in the effective aperture array can be grasped. In the apparatus according to the embodiment, in the digital signal processing unit, a plurality of received signals can be appropriately overlapped and processed in the same manner to obtain the same signal as the received signal when a plurality of waves are transmitted simultaneously ( In this case as well, parallel processing may be performed in which one frame is divided and processed in each part). In these cases, the first Fourier transform is substantially one time (there may be divided and processed in each part).

  In such an active state, the beam forming can be completed at a higher speed in the beam forming except for the aperture plane synthesis (methods (2) and (3)). However, the aperture-synthesized received signals collected for the methods (2) and (3) are subjected to transmission beamforming (transmission delay or transmission apodization is applied as necessary) and superimposed as necessary. May be processed in the same way. Incidentally, by superimposing the reception signals without applying transmission delay, in this case, it is possible to generate a reception signal when a plane wave is transmitted without steering. In the aperture synthesis processing, division parallel processing may be performed to increase the speed, but in particular, when performing multidirectional aperture synthesis, which is the past invention of the inventor of the present application, one time phase. In the case of processing in the apparatus or method of the present invention, the same angle obtained by one Fourier transform can be obtained under the deflection angle in each direction. The calculation using the spectrum data is performed, and finally, the multidimensional spectrum obtained by superimposing the multidimensional spectrum with respect to each deflection angle is overlapped without performing the inverse Fourier transform a plurality of times. A final image signal can be generated at high speed by Fourier transform (division processing may be performed). However, in the case of aperture synthesis, when performing passive processing in reception fixed focusing or other beam forming, as described above, with respect to the superimposed received signal (that is, one angular spectrum), For example, it is effective to perform processing in a single direction or a plurality of different directions.

  In addition, in the case where a superposition of a plurality of waves obtained in these processes is obtained, it is also effective to separate the spectrum if the propagation direction, frequency, or band is different, for example. In addition, it can be separated in the digital signal unit using encoding, MIMO, SIMO, MUSIC, independent signal separation (independent component analysis), principal component analysis, code, or parametric method. Note that the overlay process may be effective in other cases (for example, the SN ratio is improved by using a plurality of signals obtained in the same phase).

  Independent signal separation (independent component analysis) is effective, for example, in separating a specular reflection signal and a scattered signal, and separates an independent scattered signal between two or more frames with respect to those including the specular reflection signal. When processing is performed by realizing a state of holding or a state in which an independent scattered signal is mixed, it is possible to effectively separate specular reflection signals existing in common. Useful for automating the detection / separation (removal) of high-intensity signals from blood vessels, etc. when measuring tissue displacement such as blood flow, and the identification (detection) of the range of blood flow regions is there. In addition, it is useful for detection and extraction of boundaries of organs and tumors, and similarly, specular reflection (tissue) can be detected, separated (removed), and the range of characteristic regions can be specified (detected). . At the same time, it is also possible to separate mixed scattered signals, and independent component analysis (independent) rather than detecting the corresponding signal from each of the sum (ie, averaging) and difference of signals between frames. The component separation) has higher specular reflection signal detection capability and mixed signal separation capability. Those capabilities are higher when processed after detection (envelope detection, square detection, absolute value detection, etc.). This can be confirmed not only visually, but also quantitatively evaluated deterministically or probabilistically. Moreover, if the measurement of displacement, distortion, etc. is applied, and motion compensation (translation, rotation, expansion / contraction) is performed on translation, rotation, deformation, etc., and alignment is performed for processing, those capabilities are improved (for example, 3 MHz) When the cross-correlation-based displacement measurement is performed in the frequency simulation, even when the standard deviation of the scattered signal is 1.0, the specular reflectance distribution of 0.1 to 0.5 is mixed with the scattered signal of the same intensity. Motion compensation). Processing with spatial resolution is desirable. It should be noted that the measurement of displacement or the like is more accurate when performed before detection, but may be performed after detection. Also, when displacement measurement is performed with high accuracy using various measurement methods before detection, block matching (phase matching) in the spatio-temporal domain, which may be performed through oversampling or upsampling, or in the frequency domain Motion compensation by phase matching based on phase rotation is effective. If the independent signal is a medical ultrasonic transducer, the transducer can be tilted to pick up the specular reflection signal at the same position from another angle, or the signal can be picked up using another sub-aperture based on the steering process. It is also effective to collect signals including specular reflection signals from the same specular reflection signal source (a sequence of the same structure and composition) by shifting the scan plane (measurement technique). It is also possible to positively apply the movement of the target (the scan plane is displaced or a signal from another tissue is mixed) or deformation (considered as a state containing noise). It is only necessary to collect the signal including the signal. Similarly, when using ultrasonic waves (such as sonar) and electromagnetic waves other than medical ultrasonic waves, the movement of sensors, signal sources, detectors (including camera shake and disturbance of their cages), waves, The reflected wave or transmitted wave may be collected and processed by applying the beam steering and the movement and deformation of the object. Noise generated in the circuit may be mixed to create an effect, or may be mixed with analog or digital (including software-based software) noise that is actively generated. These processes can be used not only to separate the specular reflection signal and the scattered signal but also to obtain the same effect in the common signal and the mixed signal between the signals, and the application range is limited to this. It is not a thing. The spatio-temporal shift of the signal is not limited to displacement or distortion, but the directivity of the aperture (especially during steering), the inhomogeneous propagation speed of the medium itself, the disturbance of the medium, and changes in conditions (for example, changes in pressure and temperature) Etc.) and may be processed purely in signal analysis. In addition, waveform distortion may occur due to frequency-dependent phase delay or phase change in the device (for example, phase change in the sensor or phase delay in the amplifier in the circuit). There is a case where the waveform is corrected to correct the waveform (it is effective to multiply the complex exponential function for each frequency in the frequency domain to rotate the phase of each signal component). The phase change that occurs in the device is obtained in advance, and the sensor is appropriately electrically driven with the goal of generating a wave having a desired waveform or generating a desired waveform at the observation position or reception position. There is also. Thereby, the observation of the observation target is made highly accurate (various observations using the phase, observations of propagation speed, scattering, attenuation, etc. having frequency dependence). Only the amount that occurs at the receiving device may be corrected. The same processing may be performed for the above-described other misalignment. Although the frame signal has been described, it may be applied to those that have been subjected to beam forming (including aperture plane synthesis), or those that have not been subjected to beam forming at all before reception beam forming (transmission / reception signals for aperture plane synthesis) Beam forming may be performed after processing. That is, it may be performed at least before, during, or after beamforming. In each case, super-resolution may be used together. In addition to correcting the spatio-temporal shift, the motion compensation process described above is also effective in correcting a shift or the like when, for example, comparing and referring to a signal during transmission of a focusing beam or a plane wave (for example, in super-resolution). . Further, the motion compensation process that may be performed before or during beam forming may also serve as a delay process in the DAS process. Further, detection (absolute value detection, square detection, envelope detection, etc.) and higher resolution through linear or nonlinear processing, which will be described in detail later, are similarly applied to those subjected to beam forming (including aperture synthesis). In some cases, beam forming may be performed after processing is performed on a beam that has not been subjected to beam forming at all or on which no beam forming has been performed (transmission / reception signal for aperture plane synthesis). That is, it may be performed at least before, during, or after beamforming. When performing band broadening in these processes, oversampling or upsampling is performed in space-time, or widening through zero padding of the spectrum is performed in the frequency domain as necessary (inverse Fourier transform is performed). For example, the result of oversampling or upsampling is obtained).

  For the above-described position correction and phase aberration correction, a cross-correlation method can be used as a correlation-based method, and various displacement measurement methods can be applied. It may be processed as a one-dimensional signal or may be processed as a multidimensional signal. For example, there are (multi-dimensional) cross spectrum phase gradient method, (multi-dimensional) autocorrelation method, (multi-dimensional) Doppler method and the like. Similar to the cross-correlation method, such as the cross-spectral phase gradient method and the autocorrelation method, the effect of the matched filter is robust against the noise included in the wave signal as described above. As described above, it is effective to use the (matching) phase matching method (shift in time space or phase rotation in frequency space) when applying these displacement measurement methods to phase aberration measurement. Here, an example of an automatic determination method of phase aberration and effective aperture width in beam forming using an array type aperture to which these are applied will be shown. As shown below, discrimination based on correlation values between local signals (for example, in the case of ultrasonic waves, local echo signals and local transmitted ultrasonic signals) and detection of errors in estimation of delay time (time difference) in beamforming are detected. By doing so, it is possible to automatically determine the effective aperture width and perform beam forming. In that case, the iterative phase matching method is effective. For example, as described above, when applied to coherent compounding (superposition) in beam forming with different steering angles, an image can be obtained, and the effect of increasing the contrast and increasing the resolution can also be obtained. In addition, as described above, MIMO, SIMO, MUSIC, independent signal separation (independent component analysis), principal component analysis, parametric methods, adaptive beamforming, minimum variance beamforming, Capon method, etc. (non-patent literature) 10). Not only are these highly accurate, but the amount of calculation can be reduced. The adaptability itself depends on the reflection characteristic, scattering characteristic, or attenuation characteristic in the measurement target, and it is desirable that there is a spatial resolution.

  A description will be given of at least a received signal that has not been subjected to reception beamforming (as described above, processing may be performed on a signal that has undergone reception beamforming). Transmission beam forming includes, but is not limited to, fixed focus beam forming, waves that spread widely in the direction intersecting with the propagation direction of waves such as plane waves and spherical waves, and the like. The latter realizes a high frame rate as described above. In addition, when transmission beam forming is not performed, this method is used for so-called classical aperture synthesis, which may be effective in both the monostatic type and the multistatic type.

Among those signals, in the signal sequence received at each position around the reception position (position where beamforming is performed) that received the local signal including the signal from the position of interest in the region of interest. The local signal having the highest correlation and the reception time thereof are searched for (see FIGS. 16 to 18). The search area for that purpose is set so as to include a local signal with high correlation. High-precision phase rotation by multiplying the complex exponential function in the frequency domain is applied to the signal in the search domain, and the signal that appears in a round is within the local signal domain (local domain) that is cut out by the window to obtain the phase aberration The search area should be set appropriately larger than the local area so that it does not appear in (the calculation amount increases only if it is increased to the dark cloud, and it is not necessary to set the local area in the center. Appropriately determined from the magnitude and sign of the estimated phase aberration). When the phase aberration between the local signals is estimated to be Δt, exp {iωΔt} is added to the spectrum A (ω) of the search region signal to correct the phase aberration by shifting the search region signal by −Δt. Multiplication and inverse Fourier transform may be performed (Patent Document 6, Non-Patent Document 15, etc.). Although calculation time is required, if this process is repeatedly performed on the same pair of signals, the correlation between the local signals gradually increases, and the phase aberration can be estimated with high accuracy. (Repetitive phase matching is detailed in Patent Document 6 and Non-Patent Document 15).
FIG. 16 is a schematic diagram for explaining an example of phase aberration correction when steering is not performed when a linear one-dimensional array transducer is used. FIG. 17 is a schematic diagram for explaining an example of phase aberration correction when steering is performed when a linear one-dimensional array type transducer is used. FIGS. 16A and 16B show received signal groups obtained using different parameters, and FIGS. 17A and 17B are obtained using different parameters. The received signal group is shown. As shown in FIGS. 16 (a) and 17 (a), when processing is performed only in a frame composed of a reception signal group including a point of interest A where beamforming is performed, and FIGS. 16 (b) and 17 (a). As shown in b), received signal groups (frames) having different wave parameters and beam forming parameters are obtained, and received signals at the point of interest A shown in FIGS. 16 (a) and 17 (a), respectively. In some cases, phase aberration correction is performed. In these drawings, a case where a plurality of frames obtained at different steering angles for transmission or reception is processed is shown.
FIG. 18 is a schematic diagram for explaining an example of phase aberration correction when steering is performed when a two-dimensional array type transducer is used. FIGS. 18A and 18B show received signal groups obtained using different parameters. Although this transducer is of a linear type, there are various two-dimensional array type transducers as well as a one-dimensional array type, and the transducer is used on the basis of an arc-shaped transducer or sector scan. There are also transducers (some transducers other than the linear type may be steered with respect to the axial direction determined by the direction in which the element aperture faces). Since digital signals stored in memory after reception are processed, when cross-correlation is performed, local signals with high correlation will be evaluated at the sampling interval for signal reception time. The inventor has reported a cross-spectral phase gradient method capable of analog evaluation of a digital signal based on the Nyquist theorem. For example, this method can be used. As described above, other displacement measurement methods can be used for phase aberration correction. However, when the SN ratio of the received signal is high, processing using a window (Patent Document 6 and Non-Patent Document 15). In the case of iterative phase matching, it is often necessary to use a rectangular window, and it is desirable that a rectangular window be used at the end of the number of iterations). Estimation using the received signal (instantaneous data) of the point of interest A shown in FIG. In addition, the received signal to be processed in this process may be a signal that has already been subjected to transmission or reception beamforming.
In this cross spectrum phase gradient method, if the time difference between the local signals is large, the phase spectrum is inverted, so that it is necessary to perform unwrapping. Therefore, first, so-called coarse estimation and phase matching (spatial shift) using the cross-correlation method itself including the effect of unwrapping are performed, and then fine estimation using the cross spectrum phase gradient method is performed. In this Fine estimation, phase rotation using a complex exponential function is performed as phase matching, and it is possible to improve accuracy while improving the correlation value repeatedly (the processing target is a digital signal, but the phase is matched in an analog manner) it can). This approach is based on the phase matching method that we have established as a displacement measurement method (Patent Document 6, Non-Patent Document 15, etc.). The cross-spectral phase gradient method is faster than the cross-correlation method. Therefore, the cross-spectral phase gradient method with unwrapping is also effective (basically the distance between the point of interest and the element position). Unwrapping determined by the difference may be performed, which is easier than when observing displacement when moving in any direction). In this iterative phase matching, it is possible to gradually shorten the window length and finally obtain a high-resolution result. Coarse searches the possible range of the corresponding signal, which is physically determined by the assumed propagation speed, and then performs Fine estimation, without requiring Coarse estimation, only Fine estimation, In some cases, unwrapping is not required.
The effective aperture width is a direction away from the point of interest A at each element position where beam forming is performed in the aperture array (FIG. 16 and FIG. 17: left and right in the case of a one-dimensional array, (FIG. 18: 2 In the case of dimensions, the above processing is performed on the received signal received at the position in the peripheral direction), and (i) the correlation value obtained by the inner product between the local signals after matching processing is below the set threshold value And (ii) before the time difference with the obtained local signal becomes larger than a preset threshold value (the estimated value increases discontinuously during the processing) May change and may be considered to detect errors).
It is also effective to perform this processing when beamforming is performed only with the received signal in its own frame. For example, in the case of plane wave transmission realizing a high frame rate, it is generated in the case of single transmission. Since this wave has a narrow band in the lateral direction, it is also effective to perform this process when performing a coherent compounding process (broadbanding) by performing a plurality of steering transmissions with different steering angles as described above. Even in focusing beam forming, the effect of broadening the band is obtained and, of course, is effective. Received signals when beamforming with different beamforming parameters and wave parameters different from the steering angle are also processed (see FIGS. 16 and 17). The above process can be compounded by performing the same process at each position A in the received signal frame under the same or different receive steering angle as the transmit steering angle. May not be imaged. Therefore, after determining the transmission steering angle of the wave to be generated, one reception steering angle that is the same as or different from the transmission steering angle is determined. The same processing is performed including not only the signal frame (only the frame is processed when compounding is not performed) but also reception signal frames of other transmission steering angles. When pursuing accuracy, the transmission and reception steering directions should be determined in the direction of strong directivity of the aperture as much as possible (that is, the front direction of the aperture surface). Furthermore, it is possible to generate and compound by different combinations of transmission and reception steering angles, but if the transmission and reception steering angles are greatly different, there is a case where no image is formed.
As for compounding, for example, a plurality of signals are generated at a plurality of different reception steering angles with respect to one transmission steering angle in the front direction or an arbitrary direction, and the multi-direction is obtained by using aperture synthesis data. It has also been reported that transmission and reception steering and compounding are performed, and this can be applied to the transmission steering in a plurality of different directions.
In this processing, the length of the local signal (window length) needs to be set appropriately (the first window length when iterative matching is performed). If the shorter one, a higher correlation value is obtained, and the spatial resolution of the local signal estimation result (that is, the phase aberration estimation value) is high, but another similar signal may be detected. If the window length is long, the correlation value becomes low and the signal cannot be searched (for example, when an ultrasonic plane wave is transmitted at a nominal frequency of 7.5 MHz with an agar graphite phantom of human soft tissue, the echo signal is 30 MHz. 64 points and 128 points were appropriate when sampling at, but 32 points and 256 points were inappropriate). This is the same as the case of observing the displacement or displacement vector. As mentioned above, it is better to perform phase matching with such an appropriate window length, and when performing iterative phase matching, it is effective to gradually shorten the window length during repeated phase matching. Yes (finally high resolution results are obtained). In the case of aperture surface synthesis or the like, a scattered signal that is not imaged when the number of phase matching is several times may be imaged by repeating the number of repetitions, and iterative phase matching is effective. Although the above-described highly accurate phase aberration correction or repetitive processing requires calculation time, it is suitable for close inspection. Although real-time characteristics are important in medical ultrasound, the above processing may be a novel medical ultrasound precision inspection method. The iterative phase matching can set an upper limit value for the number of executions, and is terminated when the update value of the estimated value of phase aberration becomes smaller than a preset value or becomes sufficiently small. While the condition i) or (ii) is satisfied, the same process is performed on the received signal at the next position in the horizontal direction. In order to shorten the calculation time, it is also effective to use the estimation result obtained as the initial value of the phase aberration at the next position. In the case of the one-dimensional array type, it is possible to carry out processing left and right with the point A as the center (the effective aperture width obtained by the processing (i) or (ii) described above is determined for each position A). The center is not necessarily symmetrical). In the case of the secondary array type, it is possible to perform processing in the peripheral direction around the point A. Alternatively, the maximum effective aperture width including the point A is determined in advance, the phase aberration is estimated from the end, and the correlation value of the condition (i) is larger than the predetermined value or the phase of (ii) It is also possible to determine the effective aperture width based on the estimated aberration value itself. In any case, every time the estimation result of the phase aberration is obtained, the local signal subjected to the phase aberration correction (the local signal multiplied by the delay) is obtained, so each time when the final estimation is finished, It is efficient to perform the addition processing (that is, DAS processing using phase aberration). At that time, independent signal separation (independent component analysis) and principal component analysis are performed, and the signal has the same component as the reference signal (signal with higher accuracy than the above summation (addition average)). It is useful to perform the addition process on the former signal component by separating the signal component (a signal having higher accuracy than the above subtraction). For discrimination between the former and latter signal components, the correlation with the reference signal is calculated, the signal with the higher correlation value is set as the former, and the signal with the lower correlation value is set as the latter. The latter signal component may also be used after performing an addition process. Then, phase aberration correction can be performed in the same manner with respect to another position A in the depth direction or the lateral direction within the region of interest. If only phase aberration estimation is intended, no addition processing is necessary. Further, independent signal separation is performed at once on the signal group subjected to the phase aberration correction within the effective aperture width estimated at each point of interest A, and the signal component common to all (the signal having the highest correlation value) And the former may be used as a result of DAS processing.
When signals with different transmission or reception wave parameters or beam forming parameters are overlapped, phase aberration estimation and phase aberration correction may be performed on the signals as they are. For example, separation is performed in the frequency domain. In some cases, phase aberration estimation and phase aberration correction are performed on each separated signal (for example, processing can be performed on signals at each steering angle). . Similarly, spectrums may be divided in the frequency domain for overlapping signals and non-overlapping signals to generate new waves, and phase aberration estimation and phase aberration correction may be performed. When the signal is separated in the frequency domain, wave parameters and beam forming parameters can be realized, for example, pseudo-steered waves in various directions, new waves and beam shapes can be generated (not limited to this) ). In each case, signals subjected to phase aberration correction may be superimposed.
It has been confirmed that the contrast and spatial resolution of the image are higher in the processing in the frame alone than in the image without phase aberration correction, and a plurality of frames are processed and compounded (superposed) as described above. And it has been confirmed that it is more effective. This compounding is to perform coherent processing on the raw signal, but it performs detection (envelope detection, square detection, absolute value detection, etc.) and then superimposes (incoherent compounding) to reduce speckle. Thus, it is also effective in generating an image with improved contrast and CNR (Contrast-to-noise ratio) by emphasizing deterministic signals such as specular reflection signals and strong scattering signals.
When using other methods such as the (multidimensional) autocorrelation method and the (multidimensional) Doppler method, the cross correlation method can be used for coarse estimation, and they can be used for fine estimation without phase unwrapping. Like the cross-spectral phase gradient method, it may be used alone or unwrapped. The effective aperture width and phase aberration estimated as described above are the minimum resolution, beamforming, independent component analysis, principal component analysis, super-resolution by nonlinear processing (addition processing is performed by applying nonlinear processing, addition processing) It can be used for various applications including the above-mentioned application such as applying non-linear processing after applying. It should be noted that the average effective aperture width at each distance position can be made into a database based on the method (i) or (ii) and used without phase aberration correction. The above process is the same as in the passive second embodiment.

  Signal separation or frequency domain after processing with higher frequency and wider band (when the order is greater than 1) or lower frequency and narrower band (when the order is less than 1) by a power operation In this case, it may be performed with high accuracy. It is easy to reconstruct the signal after separation by multiplying the power of the power using the inverse power.

The above phase aberration correction is effective in various other cases. Phase aberration correction even in various observation data (between), such as when the observed quantity (physical quantity, chemical quantity, etc.) is different, or when the conditions and parameters that may affect the observed quantity are different even with the same observed quantity In some cases, various processes described in the present specification are performed after performing the above-described correction and phase aberration correction. For example, in fusing and integrating ultrasound (echo) and OCT themselves and observation data obtained using them, characteristic position accuracy is obtained from OCT data, and phase aberration correction of ultrasound (echo) is performed. (The physical properties of light and sound are different, but in particular the positions where they change or the positions where scattering occurs can be used, and the matching process itself may be performed between coherent signals. May be performed between incoherent signals or image data obtained in this manner). After matching, for coherent signals or incoherent signals (or image data), as described later, in addition to ICA, opportunity learning, deep learning, neural network (back-propagation type, hop field type, etc., or Other models such as models deformed based on these) or other processes may be performed.
The inventor mainly uses medical imaging and remote sensing (various types of radar, ground radar, extraterrestrial radar, stars, satellites, airplanes, meteorological observation, various earth observations, environment and resource exploration, space and astronomical observations. , Sonar, etc.), innovative multidimensional digital signal processing technology (electronics) that has been developed in various wave applications in fields such as nondestructive inspection (including structural studies, material research, physical properties and functions, and life) ), Inverse analysis / inverse problems, and information processing including statistical processing (based on mathematics). In particular, it can be applied comprehensively in fields such as human biological tissues (including microscopes), biotechnology, materials, structures, and the environment, and create innovative science and technology that can disrupt social and economic changes. It becomes possible. For example, the observation results can be obtained numerically, graphed, imaged, visualized, medical and life sciences (human health promotion, human tissue examination, generation, treatment, processing, application, (small) animals, Tissue, cells, drugs, etc.), materials (electric, thermal, elasticity, composite materials, etc.) development, environmental observation (gas, liquid, solid), energy development, security (monitoring and monitoring, observation of moving objects) , Various high-precision observations (large and small, short and long-term phenomena, distant and close-range objects, and the world's first in silico measurement standard is realized The three basic physics and other phenomena (biology, chemistry, biochemistry, etc.) that can be applied in a wide range of applications such as possibilities In addition, we can realize innovative non-destructive inspection techniques related to physical quantities, chemical quantities and physical properties in various phenomena), measurement (inspection and diagnosis), repair (repair and treatment, regeneration), manufacturing ( Enables growth of materials and three-dimensional culture of tissues) and applications (including creation of new functions and physical properties). As a result, in-situ measurement of basic physical quantity, chemical quantity, and spatio-temporal distribution of physical properties in the object that could not be observed until now becomes possible, and it becomes possible to observe without preparing conditions for observation. For example, it is possible to observe a working device, a living thing, or a cell under natural conditions, or to observe the process under conditions of a material growth process. Furthermore, through the advanced fusion of these various simultaneous observation / analysis technologies and cutting-edge information science and statistical mathematics, various latent factors (mechanisms), new phenomena, new principles, etc. are elucidated in detail, new physical properties and It can contribute to the creation, synthesis and repair of functions. Rather than simply over-determined system (additional averaging or least squares) to exceed the limit of accuracy of a single observation, for example, the following intelligent integration / fusion technology (high-precision common information multiplexing and (Separation of independent information, separation of independent signal sources) makes it possible to dramatically exceed (precision digital signal processing to increase the accuracy of multiplexing common information and separation of independent information and independent signal sources) ICA with new applications, machine learning and deep learning, and new applications of neural networks such as integrated learning and integrated recognition). Of course, if necessary, it can be dismantled, and in humans, the craniotomy, laparotomy, laparoscope, endoscope, oral / nasal cavity (camera), capsule (model camera), and puncture needle can be used to monitor the sensor. Sometimes it is observed in the vicinity. In addition, phase aberration correction may not be performed at all or may not be performed precisely (for example, when a cross-correlation method is used, but a shorter sampling interval is better). The signal source mentioned here may be a physical signal source itself, or may be a reflection source or a scattering source. In particular, when the received signal includes signals of multiple reflections and multiple scattering, etc., it is considered that signals to be observed are included at different positions and times. It is effective to perform the above processing, such as processing while shifting the position, such processing may also serve as signal detection processing (correlation values can be used as indicators of the accuracy and reliability of the detected signal) . Thereby, signals of multiple reflections and multiple scattering can be separated.

For example, as described in paragraph 0380, in situ imaging by wave sensing (including inverse analysis) of the distribution of physical quantities in the observation object, including electromagnetism, mechanics, and thermology, is realized, and based on those observations. Realization of physical property distribution reconstruction (inverse analysis). The source of the phenomenon can also be reconfigured. Moreover, another physical quantity can also be calculated | required using one physical quantity and those reconstruction. It can also be observed for energy. In some cases, three-dimensional or two-dimensional multidimensional observation is desirable in order to realize high-precision observation. For example,
(1) Electrical physical properties (both conductivity and dielectric constant, or one of them) based on current density (vector) distribution measurement, distribution of current source or voltage source, reconstruction of potential distribution (imaging), Or, electrical properties and current density (vector) based on potential distribution measurement, reconstruction of current source, etc. (2) mechanical properties based on distribution measurement of displacement (speed, acceleration) vector and strain (rate) tensor (shear elastic modulus, Viscosity modulus, compressibility (Poisson's ratio), incompressibility, viscosity, density, etc.) distribution and force source distribution reconstruction (imaging), mean normal stress (internal pressure) distribution is observed simultaneously or separately, inertia force vector and Observation of stress tensor distribution, etc. (3) Reconstruction of acoustic properties (volume modulus, viscoelasticity, density, static pressure, specific heat, etc.) distribution, sound source distribution, sound pressure, particle displacement / velocity distribution based on sound wave propagation measurement (Imaging) etc. (4) Temperature Thermophysical properties based on fabric measured (thermal conductivity and heat capacity, thermal diffusivity, perfusion, convection) distribution and heat distribution, there is a reconstruction (imaging), etc. heat flux distribution. These observations in the observation object, which is the medium of each wave, can be performed by means of nuclear magnetic resonance imaging (MRI), superconducting quantum interference device (SQUID) (observed wave is magnetic field), terahertz (electric field), other direct current ( (Not waves), power, radio waves, microwaves, infrared rays, visible light, ultraviolet rays, radiation, cosmic rays and other electromagnetic waves, observation of sound pressure distribution by Doppler effect using optical pulses and lasers, OCT (Optical Coherent Tomography) It can be realized on the basis of an optical microphone (inventor: Yoshito Sonoda), an ultrasonic echo (sound wave) device (modality), and others (many patents of the present inventor). The reconstruction of physical property distributions (1) to (4) reconstructs a relative physical property distribution from one physical quantity distribution, and many inverse analyzes (such as X-ray CT and electrical impedance CT) are observed. In contrast to solving the integral equation to observe the inside of the object from the physical quantity observed at the boundary position of the object, the partial differential equation or ordinary differential equation (substitution equation is substituted for the governing equation such as wave equation and diffusion equation) Since it is to be solved, it is called a differential inverse problem / inverse analysis with respect to the integral type. If a reference value (measured value, typical value, etc.) of physical properties is given to an appropriate position (reference region) in the region of interest, an absolute distribution can be obtained. When a region whose value is considered to be constant is set as a reference region and a unit size value is set as a reference value, a relative value distribution is obtained. Of course, an integral inverse problem may be used.
In any case, the equation Ax = b holds for the unknown distribution (vector x) (the number of unknowns may be equal to the number of equations, may be over-determined, or may be fewer-determined). In the case of a linear equation, the unknown distribution x is often the distribution itself that is desired, and in the case of a nonlinear problem, the estimation result is often updated by repeated estimation. In many cases, the distribution Δx. Of course, this is not the case. In the case of a nonlinear problem, the matrix A or the vector b depends on the unknown distribution x, and A (x) or b (x obtained by using the unknown distribution x estimated in each step of performing repeated estimation. ) Is used to determine Δx at that step. Then, x is updated by Δx. If the magnitude (norm) of Δx becomes smaller than a predetermined value, it is determined that the value has converged, and the repetition estimation is finished.

Furthermore, it is possible to fuse and integrate the inverse problem with those electromagnetic wave and sound wave sensing. For medical images, fusion devices of X-ray CT (morphological information), MRI (morphological and functional information), and PET (functional information) have been put into practical use. In such a situation, in addition to ultrasonic waves (longitudinal waves) and shear phenomena (transverse waves), various characteristics of each wave are utilized, for example, MRI and ultrasonic waves, ultrasonic waves and terahertz, OCT, laser, etc. Fusion of electromagnetic waves and dynamic waves, as well as heat waves, is also possible.
For example, the application of fusion and integration of (1) to (4) (hereinafter referred to as (5)) varies as described in paragraph 0380. For example, in the field of life science, based on new measurement of functions and physical properties, it can contribute to highly efficient culture (especially three-dimensional culture), its control, and elucidation of the pathogenesis of lesions (simultaneous observation of organic and inorganic, etc.) ). While iPs cells are attracting attention, for example, activity can be observed at the same time as kinetics and electrical phenomena in an in situ state where cultured cardiomyocytes are naturally active (multiplication and fusion of new observations are also possible). In addition, operating electrical and electronic circuits can be observed in situ (device function and bonding inspection). Also, in the process of growth and operation of various functional materials and various device developments, physical quantities and physical properties are observed in situ (for example, in ultrasonic elements such as piezoelectric PZT elements and polymer film PVDF, At the same time, the energy conversion efficiency, electrical impedance, vibration mode, and thermal phenomena of electric machines can be observed, and in addition, it can contribute to the creation and synthesis of new functions (miniaturization, high speed, energy efficiency). Materials, elastic bodies, thermal materials, etc.). In addition, effective observations will be conducted in various fields as described in paragraph 0380.
Information science and statistical mathematics are effective in their inverse analysis and fusion. As described in paragraph 0381, various optimizations, maximum likelihood estimation, Bayesian estimation, EM (Expectation-Maximization), and unbias regularization with partial differential operators as regularization terms (in the past) Implement the world's first spatiotemporal variant regularization, and set the regularization parameter as large as possible in absolute or relative physical property reconstruction for homogeneous materials to stabilize as much as possible to reduce variation The world's first in silico standard may be realized), singular value decomposition, equivalent and sparse modeling, signal (source) separation and feature analysis by ICA and MUSIC, new super-resolution (in silico harmonic imaging, etc.) (Patent application), in the evaluation of displacement (vector) measurement error, we assume a steady process or use Cramer-Rao Lower Bound (CRLB) or Ziv-Zakai Lower Bound (ZZLB) (A priori and a posteriori that also applied to the regularization). It is also possible to establish an error model for each observation target and apply it to them. In addition, KL information, maximum likelihood, mutual information minimization / maximization, and entropy minimization are used for integration and fusion of heterogeneous information (including the above-mentioned different observations, observations under different conditions and parameters, etc.). In addition to the use of the new ICA in combination with precise digital signal processing as described above (in particular, precise matching of time and space of multiple digital signals (digital If the signal is processed after being subjected to analog phase rotation without approximation processing), the common information extraction ability exceeds the averaging and the independent component separation ability is improved.) Integrated learning and judgment (recognition, approach to integrate / analyze multiple three-layer neural networks, differential diagnosis / recognition of lesions, etc.) Can encode a variety of recognition target is not limited to medical diagnosis), inter-image or another clinical data, mapping the like to the desired objectives and goals and new features, not limited to the same medical applications) can be performed or the like. Integration and fusion of phenomena with different stochastic processes are also effective (for example, multiplexing or separating noises according to normal distribution and ultrasonic scattering signals according to Rayleigh distribution, mixing events of different probabilistic processes, etc.). Terahertz signals and SQUID signals have a low S / N ratio, and in the same way, high accuracy by signal processing using ICA (exceeding addition average) or MUSIC is also effective. In addition, when sensing data in 3D space or space-time is big data, pursuit of real-time performance (high-speed computation), precise and high-speed Fourier beam forming (including data compression) and parallel Processing may be performed. Of course, so-called data mining is also effective. Of course, various ordinary compression techniques are also effective.

  New observation technologies developed in parallel or integrated and integrated in this way will establish a position as innovative non-destructive inspection techniques for each observation object in the future, and new prospects (new engineering) in various fields. Etc.), and is considered to advance the development of science. It can also contribute to international measurement standards for basic physical properties (especially distribution constants) (it has the potential to become the first in silico international standard such as using regularization), and it is extremely industrial. Demonstrate the effect (Achieving accuracy equivalent to the effective number of digits of the computer). The above in situ remote sensing application (approach) is not limited to these, and the ripple effect on other fields is immeasurable, and can be returned to various fields, fusion / integration fields, and society as described above.

Examples of applications realized by the above (1) to (4) are listed below in itemized form. Applications are not limited to these. In addition, it is possible to observe the distribution of changes in the thickness of the observation object with high accuracy from the reconstruction of the distribution of physical properties (thermal conductivity and electrical conductivity), and apparent observation may be effective. At least one value may be observed instead of the distribution.
(1) Electrical physical properties (both conductivity and dielectric constant, or one of them) based on current density (vector) distribution measurement, distribution of current source or voltage source, reconstruction of potential distribution (imaging), Or, electrical properties, current density (vector), and reconstruction of current source distribution based on potential distribution measurement.
Platform: MRI, terahertz, SQUID, electrode array (electroencephalogram, electrocardiograph, etc.), electrostatic potential sensor array, etc.
Observation target: MRI, electrode array, electrostatic potential sensor array are human and animal (mouse, etc.) neural network, electrical network, electrical material (resistor and dielectric), current field, electric field, potential field; Terahertz is an electric circuit, electric material (resistor or dielectric), piezoelectric element (PZT, PVDF), etc .; SQUID is all of them. When MRI or SQUID is used, the distribution of the current density vector is obtained by solving the inverse problem of Bio-Sabert's law (integral inverse problem).
(2) Mechanical properties (shear elastic modulus, shear elastic modulus, compressibility (Poisson's ratio, etc.), incompressibility, viscosity, density, etc.) based on displacement (speed, acceleration) vector and strain (rate) tensor distribution measurement Reconstruction of distribution and force source distribution (imaging), observation of average normal stress (internal pressure) distribution simultaneously or separately, observation of inertial force vector and stress tensor distribution, etc.
Platform: MRI, terahertz, ultrasound, OCT, laser, light pulse, etc.
Observation target: Soft tissues of humans and animals (such as mice) (brain tumors, cancerous lesions such as liver cancer and breast cancer, vascular disease models such as sclerosis, hemodynamics including heart, blood vessels, and blood flow, especially MRI, Intracranial cancer lesion model difficult to observe with OCT); Terahertz is also an animal lesion model, tooth and bone disease, inorganic solid piezoelectrics (PZT, PVDF, etc.), and other deformations such as PVDF, rubber, etc. Viscoelasticity, fluids (including blood) containing powders (tracers) such as medicines and metals (conductors and magnetic materials), fluids such as gases, gases and waste fluids containing dust, etc.
(3) Reconstructive imaging of acoustic properties (volume elastic modulus, viscoelastic modulus, density, static pressure, specific heat, etc.) distribution, sound source distribution, sound pressure, particle displacement / velocity distribution based on sound wave propagation measurement, and the like.
Platform: optical pulse, optical microphone, laser, MRI, ultrasound, OCT, etc.
Observation target: In addition to the above-mentioned organic observation targets, gas (helium, oxygen, air, etc.), liquid (pure liquid, mixed solution, water, saline, liquids including blood, blood, etc.), solid (inorganic type) Including). Special environment (indoor, outdoor, altitude, mountain, depth, sea, narrow space, etc.)
(4) Thermophysical properties (thermal conductivity and heat capacity, thermal diffusivity, perfusion, convection) distribution, heat source distribution, reconstruction imaging of heat flux distribution, etc. based on temperature distribution measurement.
Platform: MRI, terahertz, ultrasound, optical fiber, pyroelectric sensor, etc.
Observation target: Thermal material, inorganic solid piezoelectric (terahertz), etc., perfusion effect in animal (mouse, etc.) neural network, metabolism, cancer lesions and inflammation, heart and blood vessels, blood (perfusion) model, piezoelectric element And PVDF, convection of gas and liquid.
In addition to (1) to (4), as (5), (1) to (4) and other inverse analyzes fused and integrated or data mined. For example, the following applies.
(I) Simultaneous or multifaceted observation of the same object by (1) to (4) using the same or different devices, and multiple objects related to the same event (phenomenon) are simultaneously or multifacetedly observed.
・ In situ observation in medical care (health checkup, medical examination, human dog, diagnosis of disease, monitoring in various treatments, the same organ, tissue, lesions are observed simultaneously or from multiple perspectives, one disease or a disease that coexists, or Multiple independent diseases and related organs and tissues can be observed simultaneously or from multiple perspectives, which can be implemented with a small number of devices (hardware)).
・ In situ observation in regenerative medicine and life science (highly efficient culture, especially 3D culture and its control, elucidation of pathogenesis of lesions, simultaneous observation of organic and inorganic).
・ Observation of both myodynamics and electrical phenomena (activity etc.) at the same time in situ, where cultured cardiomyocytes (iPs cells, etc.) are naturally active, multiplexing of new observations, high accuracy, and fusion are also possible.
・ Human and mouse lesions (brain tumor, liver cancer, breast cancer) models and myocardium, blood vessels, blood in the heart chambers and blood (including drugs) (viscosity) (including hemodynamics) and thermal characteristics (and temperature) Simultaneous observation.
・ Ultrasonic and terahertz observation of drug delivery by mechanics and electromagnetic induction, development of new drugs.
・ Simultaneous observation of electrical activity, heat generation (temperature), and blood perfusion effects on human and animal neural networks and metabolism.
・ In minimally invasive hyperthermia treatment (HIFU: heating or heating using High Intensity Focus Ultrasound etc.) for human cancer lesions or Parkinson's disease, the therapeutic effect of the affected area (temperature rise, changes in viscoelasticity, etc.) by MRI or ultrasound Degeneration), perfusion itself, and neural network control of perfusion are monitored at the same time, and treatments are monitored in multiple ways in real time to improve treatment performance. In addition, only abnormal sites are efficiently treated (repaired).
・ Integrated medicine (general diagnosis, treatment, surgery, physical / chemotherapy, medication, etc.), Theranosis (the present inventor has developed a reconstruction method of tissue shear elasticity based on the ultrasonic echo method in the past. We have succeeded in monitoring the diagnosis before and after heat treatment consistently under the same index, which is considered as one successful example of Theranosis), and changes in viscoelasticity due to inflammation after treatment (blood Simultaneous observation of flow).
-Check Wiedemann-Franz's law on conductivity and thermal conductivity, and provide high-precision or inexpensive techniques (for example, using an infrared camera without using a SQUID meter).
・ Optimizing the material, structure, generation process, etc., targeting the desired characteristics in synthesis problems (composite materials, etc.).
・ In the ultrasonic element such as piezoelectric PZT element and polymer film PVDF, the energy conversion efficiency, electric impedance, vibration mode and thermal phenomenon of electric machine are observed at the same time, contributing to the creation and synthesis of new functions. (Electric materials, elastic bodies such as rubber, thermal materials, etc.).
・ Spontaneous robot movement based on in silico integration.
-Realize new measurement that has not been realized even in conventional large-scale facilities at a relatively low cost (for example, it can be used with a small number of devices such as one).
・ For example, in ultrasound, ultrasonic echo, MRI, OCT, laser, or light pulse is used to observe the distribution of displacement (vector), deformation, etc. of the observed tissue and (viscosity) distribution of physical properties such as shear modulus The image is reconstructed, and the original images and their observation results are fused to diagnose and differentiate the lesion (in addition to various fusion and integration processes, the images are simply watermarked and superimposed to simultaneously display multiple observation data. When performing some kind of treatment (surgery or physical / chemotherapy), even the treatment effect (mainly degeneration) is diagnosed using the same index (observed physical properties), that is, In addition, it is effective to observe the diagnosis, monitoring, and progress before and after treatment. In particular, in the heating and warming treatment, the temperature dependence of the ultrasonic velocity and volume change is used. Nuclear Using chemical shift of gas resonance frequency (Larmor frequency), temperature dependence of light (refractive index, etc.) when using light such as OCT, temperature dependence of observed (viscous) shear modulus The temperature (change) distribution can be observed by using the sex, etc., and the therapeutic effect can be monitored, and the thermophysical property (distribution) is reconstructed from the other observed temperature (distribution) data, Estimate (Calculate the heat source based on the inverse problem, or obtain the autocorrelation function by observing the heating / heating wave by sensing to obtain the shape of the heat source, and estimate the power of the heat source in consideration of the transmission power and the physical properties of the tissue. Or, the shape data can be used for the inverse problem, and the wavelength and propagation velocity distribution of the wave can be observed using the autocorrelation function) (Patent Document 11). Jill becomes a temperature distribution estimation and predictable, integrated decision with their observations, sequentially make a heat-warming plan, it can be realized minimum-invasive therapy. If the receiver is capable of receiving during HIFU transmission, the echo signal generated by HIFU transmission can be processed and used. If reception is not possible, an observation ultrasonic wave is transmitted to obtain a received signal. There is also a thing. Either can be used for imaging. Phase aberration correction (due to temperature dependence of sound speed, sound speed inhomogeneity, wave directivity, etc.) is calculated using at least one of these received signals, and phase aberration correction is performed for HIFU treatment and observation imaging To improve the positioning accuracy of the treatment position. On the basis of the observation result and the prediction result, the HIFU beam and treatment parameters may be sequentially determined by optimization (a variety of linear and non-linear optimization methods can be used). Linear or non-linear programming is also effective. There are cases where optimization is performed with a target of tissue properties and tissue pressure such as a desired temperature distribution, exposure amount, or (viscosity) modulus. In that case, typical data, actual measurement values, or models of the heat receiving characteristics and degeneration characteristics of the treated tissue may be used. The present invention is based on the above observation, prediction, or optimization realized by making full use of the signal processing described in the present application, and the irradiation power, irradiation intensity, continuous irradiation time, irradiation interval, irradiation position (focus point) of the HIFU. This includes electronically or mechanically controlling the HIFU treatment with respect to (position), irradiation shape (apodization), HIFU execution interval, etc. to realize a minimum-invasive treatment. Treatment control itself can be manually controlled by the clinician based on observations, predictions, or optimization results for lesions marked by clinicians or mechanically diagnosed lesions. Yes, it may be automatically controlled mechanically, but in the latter case, it is necessary to always allow the clinician to change the treatment policy and switch to manual control mode. It needs to be possible. Switching from manual mode to automatic mode may also be effective. In any case, lesion tracking is important (cross-correlation-based processing such as cross-correlation method and cross-spectral phase gradient method is robust to changes in ultrasound images (noise sources) caused by heating. ) The interface may be realized centering on a PC and peripheral devices, or may be realized as a dedicated machine.
This measure is one way to realize Theranosis, has a very high spatial resolution for diagnosis as well as treatment, and minimizes invasiveness under the differentiation of diseased tissue, nerves, blood (tubes), lymph, niche Realize the best possible treatment. Application to microsurgery is also important. In addition to early precision diagnosis, a single device can simultaneously diagnose multiple or multiple organ diseases (brain, liver, kidney, breast, prostate, uterus, heart, eye, thyroid, blood vessels, skin, etc.) Enables integrated diagnostic imaging that can be performed early and with precise HIFU treatment, even under the same indicators (physical and thermodynamic physical quantities, tissue viscoelasticity and thermophysical properties, markers, etc.) Diagnostic imaging and monitoring of therapeutic effects, as well as follow-up after treatment are possible. Both diagnosis and treatment are both minimally invasive, simple and short, and therefore less expensive than other techniques. Medical care that can be implemented can be realized. It is a medical technology that will be useful for a long time in the future while developing a new clinical style (short-term diagnosis and treatment, medical examination, etc.) under the development of medical technology suitable for a super-aging society. These means are effective not only in HIFU but also in radiotherapy and heavy particle beam therapy. Combinations including drugs are also effective. In addition, the wave to be observed is not limited to the ultrasonic wave, and various sensing waves such as MRI, OCT, and X-ray can be used (many other are described). These may be fused and integrated. Similar observations may be effective not only in medical applications but also in diagnosis, repair, creation, etc. in material engineering.
・ Elucidation of the function of human and animal brain tissues: In the cultured neural network, the process of learning and recognition, the effect of drug administration, etc. are observed electrically in situ, blood vessels in the heart and brain (viscoelasticity), blood flow ( Fluid), microflow, etc., can be observed simultaneously, and in addition, external stimulation tools and processing techniques for these tissues and cells can be developed.
(Ii) Application to environment, industrial biotechnology, energy saving and environmental conservation (recycling, observation of air, soil, water, etc.). Various gas acoustic properties (light pulse, light microphone), gas containing various dust (flow observation by terahertz), etc.
(Iii) Development of new synthesis theories such as equivalent media and functional substitution (material engineering).

Next, the above-mentioned (1) to (4), other inverse analysis, and the means for fusion / integration of (5) are listed. Technology related to information science and statistical mathematics, including inverse analysis. Basically it aims to exceed the normal measurement limits. For example, the following processing is effective.
(A) Inverse analysis: In wave sensing,
・ Uses equivalent system and sparse modeling (including identification, reduction in dimension, rough sampling data based on downsampling (regularization effect in inverse analysis), band compression in Fourier beam forming, etc.) Faster and more stable, data compression.
・ When performing the reverse in measurement and reconstruction by optimization (weighted least squares, Bayesian estimation, maximum likelihood estimation (with or without MAP), singular value decomposition method, linear / nonlinear programming, convex projection, etc.) (bio)・ Integral inverse problem such as obtaining current density (vector distribution) data and current (distribution) from magnetic field (vector distribution) data in inverse analysis of Sabert's law) and physical property reconstruction (linear or nonlinear differential inverse) Problem: Stabilization of the solution by optimizing the reference region (initial value) and integral inverse problem (nonlinear inverse problem similar to impedance CT etc.) in the initial value problem using partial differential equations.
・ Unique existence and adaptive stabilization by unbias regularization when performing inverse analysis (This inventor is a space-time variant regularization parameter that depends on the accuracy of the world's first measurement data in the past. , Set the regularization parameter as large as possible to stabilize the observation target as much as possible, and reduce the variation, the world's first in silico standard may be realized. In the past, displacement (vector) observation and (viscous) shear Implemented by elastic modulus reconstruction, etc.).
・ In addition to each observation target (strain tensor, temperature, current density vector, each physical property, etc.), an error model (variation and dispersion) of the directly observed sensing signal is established to improve accuracy (displacement (vector) in the past) In the estimation of measurement error, it is assumed that the stationary process is locally in space and time, or Cramer-Rao Lower Bound (CRLB) or Ziv-Zakai Lower Bound (ZZLB) is used, specifically when regularizing the system Use regularization parameters in a priori and a posteriori in proportion to the variance (thus making them spatiotemporally variable), and use of simultaneous equations for displacement vector components and spatiotemporal distribution of various observation objects Each equation is used for weighting reliability by using the reciprocal of dispersion or reciprocal of variance (weighted least squares), and regularization and weighting may be performed simultaneously.
・ Super-resolution (high resolution, world's first in silico harmonic generation imaging and instantaneous phase imaging, known inverse synthetic aperture and inverse filtering), new minimum variance beamforming (phase aberration correction is effective), the above signal (source ) High resolution. Maximum likelihood estimation or the like has been used for a long time in image processing. For example, a point spread function that can be variously estimated by obtaining an autocorrelation function is used (for example, Non-Patent Documents 31 to 34). There are various other methods.
・ Analog or digital linear processing or non-linear processing of wave signals, generation and utilization of new waves due to linear or non-linear phenomena in the propagation process (inside or outside of the observation target), multiple waves with single or different parameters, This includes cases where observed quantities (physical quantities or chemical quantities) are different.
・ Signal (source) separation and feature analysis (independent component analysis ICA, principal component analysis PCA, MUSIC, application of regularization and singular value decomposition, machine learning, neural network, deep learning, etc.)
It is not limited to these.
Also,
(B) Integration and fusion of heterogeneous information, multiplexing of the same information and separation of independent information (not just exceeding the limits of accuracy due to single observation by over-determined system (addition averaging or least squares)) Exceeded by high-precision multiplexing of common information and separation of independent information: Especially in signal processing and image processing, MRI (electromagnetic wave) and ultrasound (mechanical wave), ultrasound and terahertz (simultaneous observation of organic and inorganic), ultra In addition to using KL information, maximum likelihood estimation, mutual information minimization / maximization, entropy minimization, etc. for multiplexing and separation by new integration and fusion of sound waves (longitudinal waves) and shear waves (transverse waves), In order to dramatically improve accuracy,
・ Common information when processed after ICA (in the past, ultrasonic echo signal (random signal) of human tissue is subjected to precise time-space matching of multiple data (phase rotation without approximation in digital signal)) The extraction ability of the product exceeds the average and the separation ability of independent components is improved.
・ Neural network (deep integrated learning and integrated judgment / recognition): An approach for integrated learning / integrated recognition of multiple three-layer neural networks that receive heterogeneous feature vectors (information) (multiple layers in the recognition layer Combine neural networks, do not learn deeply with closed data of each feature vector (information), connect them after learning to some extent, and learn using the closed data of all feature vectors (information) And, from the beginning, the learning speed is dramatically increased and the recognition rate is drastically improved compared to learning using closed data of all feature vectors (information) using a connected network. The recognition rate is dramatically improved compared to the case where only a single feature vector (information) is used. Is a novel neural network that has already been learned, comparing the weight distribution of the network when using a combined network from the beginning of learning and when deeply learning by combining after some learning as described above, for example, It is effective to visualize the weight distribution or interpret the common component and independent component by applying ICA or PCA processing to the weight distribution. In the differential diagnosis / recognition of the lesion, the target disease and the type of the lesion are newly determined. Encoding (using an independent code) to learn the recognition object by encoding, etc., or the same or different observation data related to the recognition object, related observation data or related recognition object (eg, disease or lesion) ), Desired objectives and goals, new physical properties and functions (in silico creation and synthesis and their utilization, simpler than when it is difficult to make a device) In some cases, it may be operated in conjunction with other dedicated devices, etc.) In addition to the back projection type, the hop field type (learning and recognition of associative memory), etc. In addition to models and neural networks, optimization and other processes described in this specification (in silico processing) can also be used.
-Targeting phenomena with different stochastic processes (for example, ultrasonic Rayleigh scattering and normal distribution of observation noise), multiplexing common components and separating independent components, transitioning to different stochastic processes (probability models, Elucidate changes in random variables.
Also,
(C) Big data processing:
・ High-speed and high-precision Fourier beam forming and parallel processing are performed at the time of sensing in order to realize high-speed computation in pursuit of real-time characteristics when handling a lot of big data such as sensing data (space-time).
Data mining (including the above-described statistical processing and correlation processing, feature amount extraction by ICA, PCA, neural network, etc.).
Also,
(D) Improvement of observed signal S / N ratio: For example, generally observed terahertz signals, SQUID signals, light, etc. have a low S / N ratio, and learning from correlation analog processing in OCT, digitization processing, ICA High-precision technology based on signal processing (signal is real-time signal or complex signal) such as MUSIC, Wiener filter, matched filter, correlation processing, signal detection, etc.
In the present invention, the above processing and the like are performed, but the object and processing means of the present invention are not limited to these.

  (1) to (4) of measurement / inverse analysis (imaging) performed using hardware (devices, platforms) and computers, and (5) fusion / integration (information science, statistical mathematics, etc.) Innovative technology that realizes non-destructive inspection of physical quantities and chemical quantities in physical chemistry, biochemistry, distribution of physical properties in an integrated and real-time in situ, electromagnetic and dynamics, basic physics related to heat (Measurement / analysis method), innovative measurement (inspection and diagnosis), repair (repair, treatment, regeneration), manufacturing (material growth and tissue three-dimensional culture), application (new by synthesis, etc.) in various fields Create functions and physical properties). This research concept makes it possible to detect physical quantities / material states, changes, latent factors, etc. that have not been captured so far, as well as to make multifaceted observations of the actual behavior and function of the measurement target. Is the promotion of human health through medical and life sciences, the development of new engineering through the development of materials (including synthesis), food engineering (eg, management of freshness and quality), high-efficiency energy development and resource exploration, energy conservation, and the environment Assessment, environmental conservation (including earth and celestial bodies), weather forecast (weather forecast, rainfall, gas convection, ocean current, etc.), security, satellite, radar, sonar, international standard (may be the first standard by in silico) Etc., and the ripple effect is great both economically and socially, including industry and social infrastructure. The techniques that are developed will be fundamental technologies that contribute to the creation of science and technology innovation, the creation of new industries, and social contribution.

On the other hand, in the methods (1) to (6) relating to beam forming, the wave number of the received signal stored in the memory or the storage device (storage medium) to frequency-divide the spectrum and generate the image signal of one frame. In some cases, a plurality of processed waves are obtained in a state where the spectrum is divided in the frequency domain represented after the matching. Each may be processed in the state of the angular spectrum. In any case, the signal component band may be limited. Even when a plurality of waves are overlapped, the spectrum may be similarly frequency-divided. This corresponds to the generation of a physically pseudo wave having new wave parameters (frequency, band, propagation direction, etc.) by frequency division of these spectra. These divided spectra may be processed in parallel. The superimposing process is a process for generating a new wave parameter. However, the superposition process may be performed by superimposing the angular spectra in the spatial domain, and may superimpose the spectrum before the inverse Fourier transform. However, if necessary, the angular spectra after Fourier transformation may be superimposed or the signals after inverse Fourier transformation may be superimposed. The reversibility of Fourier transform (Fourier transform and inverse Fourier transform) is applied, and the generated signal is returned to the signal before reception beamforming (before transmission / reception beamforming in the case of aperture plane synthesis), and other beamforming is performed. (For example, different transmission or reception steering angles or a plurality of waves with different steering angles for one transmission).
As super-resolution processing, the following is the spectrum weighting processing (not so-called inverse filtering or deconvolution, but processing to perform filtering so as to have a desired point spread function after performing these processing) Nonlinear processing and imaging of instantaneous phase excluding phase rotation will be described, but in addition to the present Fourier beam forming, processing may be performed under DAS processing. For example, when transmitting a wave that spreads widely in the horizontal direction, such as a plane wave, a circular wave, a cylindrical wave, and a spherical wave, as described above, high-speed imaging is possible. In this way, it is effective to generate and superimpose a plurality of waves with different steering angles for transmission or reception and to widen the width in the lateral direction and then apply their super-resolution processing to enhance their effects. It is. Superposition of plane waves, etc. is realized when uniform focusing is performed regardless of the depth position with respect to the phase, and for example, when apodization using a Gaussian function is performed based on the above weighting processing of the spectrum It is effective to compensate for the spectral intensity by targeting high resolution imaging using aperture synthesis based on apodization using a square wave or a power function. In other words, the superposition corresponds to calculating the inverse of the calculation of the Angular spectrum based on plane wave separation in Fourier imaging. In some cases, the focus and aperture surface composition are overlapped. It is important to adjust the steering angle to be overlapped. If the angle difference is small, it is not widened only by looking at the spectral intensity relatively in the lateral direction (the band with relatively low spectral intensity is not widened). If there is an S / N ratio of a certain band (especially during aperture plane synthesis processing), a wide band can be obtained in a situation where there is a spectrum intensity when overlapping with a certain degree of angle difference. For the band having a relatively low spectral intensity when the angle difference is small, for example, weighting processing of the spectrum is effective. Since signal strength is low due to superposition of different phases, it is necessary to perform double-precision calculation processing (such as beam forming or super-resolution processing) as necessary. On the other hand, when there is a certain degree of angular difference, a broadband signal can be easily obtained with a small number of waves or beams. In these, it is also effective to normalize and superimpose wave energy. Similarly, the other two super-resolutions are also effective. Of course, the superposition processing performed by superposing waves with different focus positions and ultrasonic frequencies is also effective as a super-resolution method. Although the results obtained by super-resolving each wave can be superimposed, the amount of processing is smaller and the effect is higher when they are processed by superposition. Phase compensation in superposition (compensating for inhomogeneity in wave propagation velocity) is important.
As a method for observing a displacement vector (distortion tensor) of an observation object based on an ultrasonic echo method (that is, a reflection method) or a transmission method, the present inventor has previously used a cross-spectral phase gradient method, a multidimensional autocorrelation method, Reported (many others). It can also be used when using waves other than ultrasonic waves. In order to improve the measurement accuracy when using these techniques, it is effective to extend the lateral modulation method to use more waves or to implement an over-determined system by using spectral frequency division. Regularization (a priori or a posteriori, cross-validation method) and weighted least square method (a priori or a posteriori) are effective. Maximum likelihood estimation (for example, non-patent document 37) is also effective (with or without MAP). It is also effective to combine, integrate and mix them. When using variation, local steady processes can be assumed, Cramer-Rao Lower Bound (CRLB), Ziv-Zakai Lower Bound (ZZLB), etc. can be used. It has been found that the estimated variability can also be used (described later). Furthermore, by applying such displacement vector (distortion tensor) observation, it is possible to increase the resolution of an image (for example, an ultrasonic echo image or the like) obtained from a wave signal acquired by a reflection method or a transmission method. For example, phase matching performed in the present invention is applied to a plurality of wave signal frames (for example, ultrasonic rf echo data frames) that are temporally continuous or an image frame obtained therefrom, and motion based on a Markov model Such as superposition processing of the present invention and application of signal separation such as superposition processing and ICA processing, etc., and fusing statistically (multiplexing and separation, etc.), and various super-resolution (for example, non-resolution) Patent document 38 etc.) can be applied effectively. Fusion processing after super-resolution is also possible. As the phase matching performed in these, block matching is also effective, but as described above, highly accurate phase matching based on phase rotation is particularly effective.
In addition, so-called Compressed sensing may be performed. Similarly, it may be performed in the DAS process. Similar to the above three super-resolutions, it may be applied to the superposition of a plurality of waves. The above three super-resolutions require less computation, but combinations of them, including compressed sensing, may be processed.

Here, some examples of DAS processing that may be implemented in the present invention are summarized. The method DII of the present invention is also included. In the following, processing of real-time signals and analysis signals is described, but other processing may be applied to signals that have been subjected to various processing described in this specification.
-DAS processing (method D1) performed by a normal digital diagnostic device
In order to perform reception dynamic focusing, in the reading of the received signal stored in the memory of each channel after AD (Analogue-to-Digital) conversion processing, it is determined by the distance between each receiving element position of each channel and each point of interest. The stored signal is read from the memory at the address indicating the digital reception time (ie, Delay). Then, those signals within the effective aperture width are added (Summation). According to this method, an error determined by the sampling frequency of the received signal occurs in the delay, so that sampling is naturally performed based on the Nyquist theorem, but sampling is performed at a high frequency as much as possible. Has the characteristics of being fast. The signal to be processed may be an analysis signal in addition to the digital real signal after AD conversion processing. The calculation may be performed using a general-purpose CPU in addition to the dedicated circuit, and an embodiment of a calculation protocol is also shown below. The sampled time and space coordinates (integer values) may be considered as an index of an array in which a digital signal is stored in the program, or may be considered as an address of a memory in which the digital signal is stored (hereinafter the same). ).
For example, in the DAS processing at the sampling position i = I represented by an integer value closest to the interest point A or the interest point A, an actual signal or an analysis signal
r (I) (DAS1)
If the signal from the point of interest A received by another receiving element to be added to is present at a position where the propagation distance is longer by Δx in the received signal r ′ (in the case of the reflection method, the outgoing path synthesis, etc. Or, when performing beam forming for transmission, the difference in propagation distance at that time is also included. When the sampling interval is expressed as sampx, Δi = nint (Δx / sampx) (where nint ( x) represents a rounded integer function), or Δi = inta (Δx / sampx) (where inta (x) represents a rounded integer function), or Δi = intd (Δx / sampx) (where intd (x) represents a rounded down integerization function) or a real signal or analysis signal expressed using an integer value Δi calculated using a function or calculation that converts the argument x to an integer
r '(I + Δi) (DAS1')
Is added. The integer value Δi is preferably such that Δi × sampx is closest to the analog value Δx (nint is preferable in the above), and the calculation method is not limited to these. This process is added to the digital signal received by the receiving element within the effective aperture width at each position and added. Under the assumption that the propagation speed is constant, the same explanation can be made by using time instead of distance.
Alternatively, there are various interpolation processing methods for digital signal values, and using them, the signal value at the position of Δx may be obtained by interpolation approximation (bilinear interpolation, high-order interpolation, Lagrangian method, spline interpolation, etc.) In addition to these, various interpolation approximations can be performed).
-DAS processing with high accuracy of method D1 (method D2)
While performing DAS processing based on the method D1, in order to increase the accuracy of the delay processing, the analysis signal a (t) of the received signal calculated based on the Hilbert transform is multiplied by a complex exponential function, and phase rotation is performed. By multiplying the delay to perform, the accuracy of the time t ₀ shorter than the sampling time interval samt is obtained, and the addition processing is performed.
a (t + t ₀ ) = a (t) exp [jω ₀ (t) t ₀ ] (DAS2)
Here, j is an imaginary unit, and a relationship of t = i × sampt (i is an integer value of ₀ to N−1) is established, and ω ₀ (t) is a nominal angular frequency at a sampling time (position) t. , The center of gravity (center) angular frequency, or the instantaneous angular frequency. Expression (DAS2) is an approximate calculation of a signal of time (position) moved by an analog amount t ₀ in the positive direction of the sampling coordinate system with respect to the sampling time (position) t. In the DAS processing at the sampling position i = I that is closest to the point of interest A and is represented by an integer value, the delay value Δt of the analog amount to be applied (for the reflection method) for the sampling time (position) t as in the method D1. In this case, Δi (for example, Δi = nint (Δt / sampt)) calculated on the basis of the forward or transmission beamforming such as aperture synthesis is also used. It is desirable to use an analysis signal a (t) (= a ((I + Δi) × sampt)) of the represented sampling time (position) I + Δi. That is, it is desirable to use a signal having a sampling time (position) t closest to the ideal analog time (position) T = I × sampt + Δt. Therefore, when T> t, the equation uses a positive value t ₀ = Tt = Δt−Δi × sampt, and when T <t, the equation uses a negative value t ₀ = Tt. This process is added to the digital signal received by the receiving element within the effective aperture width at each position and added.
Although it is more accurate than the method D1, it is an approximation process using the sampled time (position) frequency ω ₀ (t). It is affected by frequency modulation such as attenuation and scattering. As with method D1, the sampling frequency should be higher. Has high speed.
Incidentally, when the sampling signal is expressed clearly at discrete positions x (= i × sampx, i is an integer value of 0 to N−1) instead of time, the equation (DAS2) is expressed by the wave number k ₀ (= ω _0). / c = 2πf ₀ / c = 2π / λ) (where c is the wave propagation velocity, f ₀ is the nominal frequency, centroid (center) frequency, and instantaneous frequency, λ is the wavelength),
a (x + x ₀ ) = a (x) exp [jk ₀ (x) x ₀ ] (DAS2 ′)
It is expressed. Similarly, in the DAS process at the sampling point i = I represented by an integer value closest to the point of interest A or the point of interest A, the distance difference Δx of the analog amount to be applied to the discrete position x (in the case of the reflection method, Δi (eg, Δi = nint (Δx / sampx)) calculated based on the difference in propagation distance at the time of forward or transmission beamforming, such as aperture synthesis, is used. It is desirable to use an analysis signal a (x) (= a ((I + Δi) × sampx)) at a sampling position I + Δi expressed as follows. That is, it is desirable to use the signal at the sampling position x closest to the ideal analog position X = I × sampx + Δx. Therefore, when X> x, the expression uses a positive value x ₀ = X−x = Δx−Δi × sampx, and when X <x, the expression uses a negative value x ₀ = X−x.
Alternatively, in each of the equations (DAS2) and (DAS2 ′), phase rotation is performed on the digital signal of the ideal analog time (position) T and the sampling time (position) t and position x closest to the ideal analog position X. Rather than multiplying, each receiving element position within the effective aperture width when each sampling position i (x = i × sampx i) of each generated beam or each wave is considered as each interest point A is the respective interest. Using the Delay Δt and the distance difference Δx with respect to the point A as discrete (digital) data Δt (i) and Δx (i) represented for each point of interest i, reception within the effective aperture width at each position The analytic signal a (i) of each digital received signal received by the element is multiplied by a complex exponential function as follows,
a (i) exp [jω ₀ (i) Δt (i)] (DAS2 ″)
a (i) exp [jk ₀ (i) Δx (i)] (DAS2 ''')
to add.
-DAS treatment improved from method D2 (method DII)
The method D2 is an approximation process using the frequency and wave number of the sampling position in the analysis signal. However, the present invention, which is the method DII, similarly enables high-speed calculation without using the frequency and wave number of the sampling position.
Center-of-gravity (center) frequency (analog value obtained at frequency coordinate i represented by integer value in discrete Fourier transform) obtained as centroid of amplitude spectrum S (i) in the frequency domain (non-positive frequency spectrum is zero)
M ₀ = ΣiS (i) / ΣS (i) (DASII1)
However, the amplitude spectrum S (i) (where i = 0 to N-1) is the product of the Fourier transform of the digital spatial signal r (x) (where the sampling position is x = i × sampx) and its conjugate. It is obtained from the square root. In the equation, the addition range of Σ is i = 0 to N / 2.
Therefore, the wave number k ₀ is
k ₀ = (2πM ₀ ) / (N × sampx) (DASII2)
It is. Here, the analytic signal a (x)
a (x) = A (x) exp {jk ₀ (x) x}
= A (x) exp {jk ₀ (x) x (i x sampx)} (DASII3)
Try to express.
Based on this, each receiving element position within the effective aperture width when each sampling position i (x = i × sampx i) of each generated beam or each wave is considered as each interest point A is each interest point. The distance difference Δx with respect to A is used as discrete (digital) data Δx (i) represented for each point of interest i, and each digital received signal received by the receiving element within the effective aperture width at each position The analytic signal a (i) is multiplied by a complex exponential function as follows,
a (i) exp {j (2πΔx (i) / sampx) / (N × sampx) × (i × sampx)}
= a (i) exp {j (2πΔx (i)) / (N × sampx) × i} (DASII4)
And calculate. As the DAS-processed signal advances in the positive x direction, an effect is obtained in which the direction orthogonal to the signal is strongly widened (higher resolution). Note that i (= 0 to N) in the formula (DASII4) is
Ni (i = 0 ~ N-1) (DASII5)
You may calculate using. In this case, as the DAS-processed signal returns to the negative x direction, an effect is obtained in which the direction orthogonal to the signal is strongly broadened (high resolution). If Δx is made constant without depending on the point of interest i, this means that frequency modulation that is invariant in the i direction is applied. In other words, this process performs frequency modulation on the received signal at each receiving element position within the effective aperture width for each point of interest i.
M ₀ + Δx (i) / sampx (DASII6)
Is a process of multiplying and adding. Similarly, when the signal is represented not as a digital spatial signal but as a digital time signal r (t), the analysis signal a (i) represented using the instantaneous frequency ω ₀ (i) is as follows: Is multiplied by the complex exponential function,
a (i) exp {j (2πΔt (i) / sampt) / (N × sampt) × (i × sampt)}
= a (i) exp {j (2πΔt (i)) / (N × sampt) × i} (DASII4 ′)
And calculate. Others are the same.
It is also effective to apply desired frequency modulation to a specific position or to apply frequency modulation uniformly in space. If the modulation wavelength applied to the signal at position x and time t is k ₀ ′ and the modulation frequency is ω ₀ ′,
a '(x) = a (x) exp [jk ₀ ' (x) x] (DASII7)
a '(t) = a (t) exp [jω ₀ ' (t) t] (DASII7 ')
It is obtained. Similarly, it can be applied to discrete signals.
Superimposing unmodulated waves and modulated waves is also effective for widening the bandwidth (higher resolution) and improving the accuracy of observation using phase (displacement observation, etc.).
・ Theoretical most accurate DAS processing (Method D3)
A method invented in the past by the present inventor (Patent Document 6 and Non-Patent Document 15), wherein a spectrum A (ω) of a local signal including a signal at a position of interest is multiplied by a complex exponential function in the frequency domain, Delay is performed by rotating the phase of the signal.
A '(ω) = A (ω) exp [jωt ₀ ]
This is an interpolation process that satisfies the sampling theorem, and theoretically has the highest accuracy, but requires calculation time.
Fourier beam forming (Method D4)
It is beam forming which is the basis of the present invention. In this method, digital wave number mapping is performed in the multi-dimensional frequency domain of the received signal. Fast Fourier transform is performed, and the accuracy equivalent to method D3 can be calculated at a much higher speed. As a feature different from other reported normal Fourier imaging methods, interpolation approximation processing is not required in the digital wave number mapping, but interpolation near processing can also be performed in order to increase the speed. However, in that case, it is required to increase the sampling frequency in order to cause artifacts and reduce the decrease in accuracy.
In these beam forming processes, the analysis signal is not necessarily processed, and the calculation time may be shortened by omitting the calculation for converting the received signal into the analysis signal. However, in the process of multiplying the complex exponential function in space-time, it is not theoretically correct and includes errors, but imaging of the ultrasonic signal itself and various imaging performed by applying it (such as elastic imaging, Many others) may be practical.
In addition, each delay process in these DAS processes (methods D1 to D3) is not limited to the DAS process, but is also performed during other beam forming such as Fourier beam forming, adaptive beam forming, and minimum variance, and the signals described in the present application. This is useful when shifting signals such as phase aberration correction, motion compensation, phase matching, alignment, and position correction in time coordinates, space coordinates, and space-time coordinates. Moreover, it is not restricted to the thing as described in this application. As in the case of the one-dimensional analysis signal, the multi-dimensional analysis signal at the position (x, y, z) or time (t1, t2, t3) can be processed. For example, in method D2,
In the case of two dimensions,
a (t1 + t1 ₀ , t2 + t2 ₀ ) = a (t1, t2) exp [j {ω1 ₀ (t1, t2) t1 ₀ + ω2 ₀ (t1, t2) t2 ₀ }] (2DAS2)
a (x + x ₀ , y + y ₀ ) = a (x, y) exp [j {kx ₀ (x, y) x ₀ + ky ₀ (x, y) y ₀ }] (2DAS2 ′)
In the 3D case,
a (t1 + t1 ₀ , t2 + t2 ₀ , t3 + t3 ₀ ) = a (t1, t2, t3)
× exp [j {ω1 ₀ (t1, t2, t3) t1 ₀ + ω2 ₀ (t1, t2, t3) t2 ₀ + ω3 ₀ (t1, t2, t3) t3 ₀ }] (3DAS2)
a (x + x ₀ , y + y ₀ , z + z ₀ ) = a (x, y, z)
Xexp [j {kx ₀ (x, y, z) x ₀ + ky ₀ (x, y, z) y ₀ + kz ₀ (x, y, z) z ₀ }] (3DAS2 ')
Can be calculated. However, (ω1 ₀ , ω2 ₀ , ω3 ₀ ) are the nominal angular frequency, centroid (center) angular frequency, and instantaneous angular frequency in each time direction at each time (t1, t2, t3), and (kx ₀ , ky ₀ , kz ₀ ) is the wave number in each direction at each position (x, y, z). Shifting can be similarly performed in a multidimensional signal of a combination of position (x, y, z) or time (t1, t2, t3). In other words, in the digital signal, discrete coordinates (requires high accuracy) using the nominal angular frequency in each time direction at each time, the center of gravity (center) angular frequency, and the instantaneous angular frequency or wave number in each direction at each position. In some cases, it is desirable to have a high sampling frequency). As in the case of the one-dimensional case, the accuracy can be increased compared to the method D1 (corresponding to block matching or fragment matching of signals in the spatiotemporal domain), and other methods (phase matching based on phase rotation in the frequency domain of the method D3) Compared with Fourier beam forming in method D4), the accuracy is low, but the calculation speed is fast. This is suitable when high calculation speed is required.
Similarly to the case of the one-dimensional analysis signal, the modulation in the method DII can be performed on the multi-dimensional analysis signal at the position (x, y, z) or the time (t1, t2, t3).
For example, in the case of two dimensions,
a '(x, y) = a (x, y) exp [j {kx ₀ ' (x, y) x + ky ₀ '(x, y) y}] (2DASII7)
a '(t1, t2) = a (t1, t2) exp [j {ω1 ₀ ' (t1, t2) t1 + ω2 ₀ '(t1, t2) t2}] (2DASII7')
In the 3D case,
a '(x, y, z) = a (x, y, z) exp [j {kx ₀ ' (x, y, z) x + ky ₀ '(x, y, z) y + kz ₀ ' (x, y, z) z}]
(3DASII7)
a '(t1, t2, t3) = a (t1, t2, t3) exp (j {ω1 ₀ ' (t1, t2, t3) t1 + ω2 ₀ '(t1, t2, t3) t2 + ω3 ₀ ' ( t1, t2, t3) t3}]
(3DASII7 ')
It is obtained. Where (kx ₀ ′, ky ₀ ′, kz ₀ ′) is the modulation wavelength in each direction applied to the multidimensional signal at each position (x, y, z), and (ω1 ₀ ′, ω2 ₀ ′, ω3 ₀ ') Is a modulation frequency in each time direction applied to the multidimensional signal at each time (t1, t2, t3). The same applies to multidimensional signals with spatial and temporal coordinates. Applications are not limited to DAS processing, including one-dimensional cases.
Other delay processes can also be multidimensional and can be applied to multidimensional signals.

  In addition, the beam forming method according to another aspect of the present invention is an array type aperture element in all beam forming such as Fourier beam forming and DAS processing described in (1) to (6) and (7) above. In groups (with independent transmit or receive channels where each element is driven independently and can independently receive the received signal) in adjacent or remote locations (not necessarily equally spaced) At least two or more elements are subjected to the same transmission or reception delay or transmission or reception apodization and used as one aperture, thereby transmitting a wave having a strength stronger than transmission or reception using one element or Including use for receive beamforming. For example, in a one-dimensional array type transducer, when the element width and the element interval are shortened in order to improve the spatial resolution in the axial direction and the lateral direction, the intensity of wave of transmission and reception becomes weak. This is also true when a two-dimensional array or a higher-dimensional array is used (the element width and the element interval in the direction of the number of dimensions are shortened). In the case of increasing the frequency by thinning the element thickness, or in the case of using PVDF or the like whose transmission intensity is weaker than that of PZT or the like in the ultrasonic wave, the intensity of the wave becomes weak. This is effective in such cases. That is, it is possible to increase the S / N ratio of the reception signal received by the reception transducer by increasing the intensity of the transmission or reception wave. For example, it is effective when performing classical aperture synthesis (monostatic or multistatic). In this case, the effective aperture width can be shifted by a physical element interval (one element at a time), or can be shifted by an arbitrary number of elements. It is possible to make the distance shifted during scanning variable. In a multi-dimensional array type transducer, scanning may be performed with different numbers of elements and different distance intervals in each direction of dimension. The combination of adjacent or distant elements considered as one aperture may be changed during the scan. Further, as is done in normal beam forming, the effective aperture width may be changed during scanning. It can be implemented in various types of array type transducers, and this process itself is not only a digital device, but also an analog device or a fusion device with a digital device (for example, a transmission circuit including transmission delay, transmission apodization, etc. is an analog circuit). May also be implemented. In this process, the number of elements regarded as one element for transmission or reception, their position (combination), effective aperture width for transmission or reception, and distance for shifting the effective aperture width for transmission or reception are added to the above beam forming parameters. If necessary, the above wave parameters are also used, and if necessary, a plurality of effective apertures are used together to generate a plurality of waves and beams (simultaneous transmission or different targets in the same time phase). In the same way, various applications described in the present invention may be performed. In transmission or reception in classical aperture plane synthesis or normal beam forming, a plurality of aperture elements that are regarded as one aperture may be used simultaneously at a plurality of locations within at least one effective aperture width. When an object to be observed is mechanically scanned with a strong intensity wave using an array element with a large physical aperture width or a transducer with a single aperture (the position of transmission or reception changes digitally or analogly), Beam forming may be applied to a beam transmitted or received spatially densely or sparsely compared to the width of the aperture.

  This simultaneous driving of a plurality of elements may obtain the same effect by adding reception signals of those elements even when receiving by one element or a plurality of elements in one element driving. The same effect may be obtained by processing in the same way even when receiving by one element or a plurality of elements in the simultaneous driving of a plurality of elements. Also, when performing transmission beamforming by driving an element group within the effective aperture width, transmission may be performed simultaneously from various combinations of elements existing within the effective aperture width. There are also cases in which transmission is performed simultaneously from a plurality of effective aperture widths.

Performing simultaneous transmission of a plurality of elements in various manners as described above is equivalent to increasing the width of the transmission elements and the pitch of the transmission elements, resulting in a grating lobe. As described above, the width of the transmitting element is increased, and the pitch of the transmitting element may be smaller than the element width. In some cases, the device width or pitch is physically large (signals may be collected more densely than the device width or pitch distance by mechanical scanning). These depend on the wave carrier frequency and the steering angle (including 0 °) (the direction of the grating lobe can also be estimated by geometric calculation). In the first place, side lobes are generated from the aperture elements. Usually, since these cause false images (artifacts), the beam forming is performed by optimizing the element width, pitch, element shape, wave carrier frequency, steering angle, apodization, and the like. Actually, the sensitivity of transmission and reception is different, but the same is often considered. Likewise, grating lobes and side lobes are generated in reception alone, and may occur in both transmission and reception. is there.
As the inventor discloses in Patent Document 7 and Non-Patent Document 19, it is possible to separate waves with different steering angles in the frequency domain (see also paragraph 0623). From the centroid of the spectrum and the instantaneous frequency of the analysis signal corresponding to the spectrum, the propagation direction of the wave and the steering angle actually generated can be estimated. This method can also be used when separating or removing the grating lobes and side lobes from the main lobe. Usually, the spectrum of the grating lobe and side lobe is separated in the frequency space, and it is easy to identify and separate them (extract only the spectrum of interest or make the spectrum of other bands zero). Just fine).

  In fact, these grating lobes and side lobes can be used actively as they are or processed to achieve lateral modulation, and can be used in various applications such as wave imaging and displacement (vector) observation. it can. Usually, lateral modulation refers to the situation where the waves intersect, but is sometimes applied separately to each steered wave (sometimes weighted simultaneously). In these, for example, the separated waves can be detected and imaged as incoherent signals, or the incoherent signals can be superimposed (compounded) and imaged to reduce speckle. Further, a new coherent signal may be synthesized by dividing (or weighting) the spectrum in a certain band while maintaining the coherent signal. It is also possible to generate one or more waves having different parameters such as a steering angle, and detect and image each of them or superimpose images. Also, each of the coherent signals generated by these processes can be used for observation of displacement or used simultaneously to solve simultaneous equations and over-determined systems for the same displacement and displacement vector components. Sometimes. Some of the waves corresponding to the grating lobe and side lobe have a steering angle larger than the steering angle set by beam forming, in which case the lateral frequency does not cause a grating or side lobe. Compared to this, the measurement accuracy of the lateral displacement (Non-Patent Document 19) and displacement vector is improved. Some have a steering angle larger than or substantially the same as the steering angle set by beam forming, and these may be used together. Although multiple grating lobes and side lobes are generated, the higher the frequency in the lateral direction, the weaker the signal strength, and the spectrum is made zero in the frequency domain so that it can be discarded when the signal SN ratio is low. Rather, it is used as a wave component with a low frequency in the lateral direction. As with normal steering beam forming, if the frequency in the lateral direction is high, the frequency in the front direction is low, but when observing the displacement vector, the effect of improving the measurement accuracy of the lateral displacement is superior to the low frequency In addition, the measurement accuracy of the displacement in the front direction may be improved.

  A displacement vector (multidimensional autocorrelation method, multidimensional self-Doppler method, etc. (non-patent document 13) using a plurality of waves generated in these processes and moving in an arbitrary direction in the digital signal unit is used. By solving the simultaneous equations related to the components, the inventor of the present application can measure the displacement in one normal direction with high accuracy (derived more equations than the number of displacement components to be obtained, and overdetermined. In an (over-determined) system, the least square method, the average value of calculation results, and high-precision and high-frequency results are obtained in a state where the waves overlap and have a high frequency and a wide range, etc. (Patent Document 5). One equation is derived from each generated wave. A normal Doppler method may be applied to one wave. Each wave may be a combination of waves, or a spectrum may be frequency-divided or processed. It is desirable that each wave has a high frequency, a low-frequency spectrum removed may be used, and if a high spatial resolution is also required, a wide band is desirable (Non-patent) Reference 14). A window capable of weighting the spectrum may be used for the division and processing. From the displacement (vector), strain (tensor), strain velocity (tensor), velocity (vector), and acceleration (vector) are obtained by partial differentiation using a differential filter related to space or time. These can be used to determine (viscous) shear modulus, viscosity, average normal stress, density, and the like. In addition to this, as a method for measuring displacement (vector), a multidimensional cross spectrum phase gradient method (one of block matching methods, Patent Document 6, Non-Patent Document 15, etc.), which is the past invention of the inventor of the present application. Reference) and a digital demodulation method (Patent Document 7), and similarly, distortion and the like can be measured. Moreover, when these are used, the propagation of shear waves and low-frequency vibration waves can be measured. The (viscous) shear modulus, shear wave propagation velocity, propagation direction, shear wave displacement, frequency, phase, vibration amplitude, vibration velocity, vibration acceleration, and the like can be measured. These can also be obtained as distributions.

  In order to increase the accuracy of this displacement measurement, the inventors of the present application have invented regularization in the past. In order to determine the regularization parameter of the punishment term, for example, a posteriori is used by estimating the variation of the measured displacement (vector) under a (local) stationary process (Patent Document 6), or a priori, The inventors have invented the use of Ziv-Zakai Lower Bound (ZZLB, for example, variation shown in Non-Patent Document 16) using wave or beam characteristics (for example, Non-Patent Documents 17 and 18). It is also possible to apply the variation derived by the one-dimensional autocorrelation method (Non-Patent Document 20), which is a velocity measurement method in one direction (used in power Doppler).

  In the present invention, these variations and ZZLB can be used for weighting in order to adjust the reliability of each equation when the Doppler equations derived as described above are combined (the one with high reliability is heavy. Set low for low reliability). That is, at each position in the region of interest, the value is obtained from each of the waves or beams described above, and the Doppler equations derived from the corresponding waves or beams at each position are weighted to obtain the simultaneous equations. solve. Weighted Least Squares Solusion (WLSQS) can be determined for a posteriori or a priori using the least squares method.

The simultaneous equations of the above derived Doppler equations are
Where u is a point of interest or an unknown displacement vector of the local region including the point of interest or distribution thereof, b is a vector representing the phase change or distribution of the local region related to the point of interest or point of interest generated between frames, and A is a corresponding one. Each of the points of interest or the frequency components of the local region related to each point of interest or a matrix thereof, and the components A and b may be subjected to moving average processing in the time direction or the spatial direction. In addition, when demodulated, the Doppler equations in a state where only the two-direction or one-direction displacement component having the carrier frequency is unknown are in a continuous state.
, Using the dispersion or the inverse of ZZLB, weighting it using the matrix W representing itself, its power, or its distribution.

Specifically, focusing on a single point of interest or local region, one or more Doppler equations derived from one of the waves or beams p (= 1 to N) (or multiple, ie, cross-spectral phase gradient methods). Is used, the number of simultaneous equations for the phase spectrum in the signal band with respect to the cross spectrum obtained in the local region, and the block based on the multidimensional autocorrelation method and the multidimensional Doppler method When matching is performed, the reciprocal value Wp of ZZLB calculated at the point of interest or the local region is the number of equations at the point of interest or the local region. Since it is the reciprocal of ZZLB of the displacement in the beam direction, for example, when the unknown displacement of the point of interest or the local region is a three-dimensional vector u = (Ux, Uy, Uz) ^T ,
However, Axp, Ayp, and Azp (p = 1 to N) are frequency components in the x, y, and z directions, are components of the matrix A in the formula (A1) or the formula (A2), and bp (p = 1 to N) is a phase change between frames, is a component of the vector b of the same equation, and Wp is a diagonal component of the matrix W of the equation (A2). In the case of using the cross spectrum phase gradient method (one of the block matching methods) and the case of performing block matching based on the multidimensional autocorrelation method or the multidimensional Doppler method, Wp is included in all of the simultaneous equations. (Ie, in one p, a plurality of equations are coupled and all of them are multiplied by Wp).

For example, according to ZZLB described in Non-Patent Document 16, when Cramer-Rao Lower Bound (CRLB) is established, the variance that is the square is

However, T is the moving average width for obtaining the frequency and phase change in the case of the multidimensional autocorrelation method and the multidimensional Doppler method, and is used in the multidimensional cross spectrum phase gradient method, the multidimensional autocorrelation method, and the multidimensional Doppler method. When performing block matching, it is the length in the beam direction of the local region of displacement measurement (if T is the same in simultaneous beams or equations, the variable T need not be used, and an arbitrary constant such as 1 F _0b is the ultrasonic frequency in the beam direction, B _b is the Rectangular bandwidth in the beam direction, and SNRc is the SNRe that is the SN ratio of the echo and SNRρ that is the correlation SN ratio (for displacement and deformation of the object). The signal ratio to the noise component generated by the waveform being distorted and the correlation being reduced)
However, ρ is a correlation value obtained when a local cross spectrum is obtained between frames or a correlation value obtained locally by the length of the moving average width.
Combined signal-to-noise ratio
It is.

Therefore, the variation may be estimated by measuring and using T, f _0b , B _b , SNRc, SNRe, SNRρ, and ρ as described in Patent Document 17, for example. Arbitrary constants and typical values may be used without measurement. As described in Non-Patent Document 19, f _0b may be obtained as an instantaneous frequency or a first moment (center of gravity, that is, a weighted average value), and B _b is a second-order center moment. It can be estimated by finding the square root.
S (fb) in equation (S1) and equation (S2) is obtained by dividing the raw spectrum by using the total energy calculated using the raw spectrum and fb = 1 in equation (S1), and the total energy is It is normalized to be 1. Alternatively, in the formulas (S1) and (S2), a raw spectrum may be used as S (fb), and each calculation result may be divided by the total energy, and the latter has a smaller calculation amount. B _b obtained by the equation (S2) may be used after being converted to represent the Rectangular bandwidth based on the actual transmitted or received pulse shape or spectrum shape (the second-order central moment below is used). The same applies when used). In the case of a multi-dimensional received signal, the calculation may include two axes orthogonal to the frequency axis in the beam direction (that is, three dimensions) or one axial direction (two dimensions). In this case, the following equation is used.

Similarly, the spectra in the formulas (S1 ′) and (S2 ′) are normalized so that the energy is 1. Alternatively, similarly, the raw spectrum may be used in the formula (S1 ′) and the formula (S2 ′), and each calculation result may be divided by the total energy, and the latter has a smaller calculation amount. B _b obtained by the equation (S2 ′) may be used after being converted so as to represent the rectangular bandwidth based on the actual transmitted or received pulse shape or spectrum shape (the following second-order central moment) It is the same when using.
On the other hand, the echo SN ratio SNRe can be statistically estimated by repeatedly collecting echoes for the object or the calibration phantom. In some cases, the typical value is determined a priori based on the object, its state, measurement experience, and the like. On the other hand, the correlation SN ratio SNRρ can be estimated using the correlation value ρ evaluated locally at each point of interest. These ways of obtaining are not limited to these. In addition, if any value is missing and the variation cannot be estimated absolutely, a typical value can be used, but when setting a regularization parameter, it is represented in the possible range. The result of the best situation may be obtained from the quality of the result obtained by multiplying the undetermined variation by an undetermined proportionality constant and changing the proportionality constant (for example, Patent Document 6, Non-Patent Document 17 and 18).

In addition, when applying the variation (used in power Doppler) derived by the one-dimensional autocorrelation method (Non-patent Document 20), which is a velocity measurement method in one direction, the autocorrelation function is slow. -time-axis τ
And the mean and variance of the Doppler angular frequency ω are respectively
If the velocity in the beam direction is constant within the pulse repetition period I, approximately
If the pulse repetition period I is short, approximately
Is required. Incidentally, R (0) may be obtained from the integration of signal energy or power spectrum based on Wiener-Khinchine theorem.
Although the above autocorrelation function is not expressed using spatial coordinates, it is processed using a signal of a one-dimensional local region in the beam direction at a point of interest or a two-dimensional local region including the point of interest or a three-dimensional local region. (One-dimensional, two-dimensional, or three-dimensional moving average processing may be included. In the two-dimensional or three-dimensional local region, the beam direction does not have to be an orthogonal coordinate axis (including not only a Cartesian coordinate system but also a curved coordinate system) of the local region, and the average and variation obtained are determined by the local region. Is the average and variation of the velocity in the beam direction.
Accordingly, the average and dispersion of the displacement in the beam direction are obtained by multiplying the formulas (AUTO2) or (AUTO2 ′) and (AUTO3) or (AUTO3 ′) by the squares of I and I, respectively. Here, the weighted measurement of the displacement using the variation of the displacement is shown. However, the Doppler equations of speed and acceleration may be derived, and each variation may be weighted and measured.

Here, when the first moment and the second central moment in the beam direction are not directly estimated but are estimated in each direction (for example, when the signal is three-dimensional), The first moment f _0x and the second center moment Bx are
In the case where a method different from ZZLB is used, if the variation in the displacement vector components is estimated without directly estimating the variation in the beam direction displacement, it can be estimated as follows. That is, the propagation of the error to the beam direction displacement may be considered under the assumption that the stochastic process of the measurement error of these displacement components is independent. For example, when the average value and variation of the displacement of the three-dimensional displacement vector are estimated as (mx, σx), (my, σy), and (mz, σz), the average value m _beam of the displacement in the beam direction Each of the variations σ _beam can be estimated as follows.

Further, parameters described in equation (A4) ~ formula _{(A6) (T, f 0b} , B b, SNRc, SNRe, SNRρ) is given for each of a plurality of directions, the average f _0x in each direction of displacement, f _0y , f _0z and variation σ _CRLBx, σ _CRLBy, σ _CRLBz are each when estimation variance sigma _CRLB beam direction of displacement, according to equation (A8),
Can be estimated.

When the unknown displacement at the position of interest is a two-dimensional vector u = (Ux, Uy), it is derived in the same way (when there is one unknown displacement, a displacement U in one direction or a displacement U in the beam direction). Is the estimated value itself obtained).

  In the case of obtaining the displacement in each of the interest points or the local regions related to the interest points, the weighted Doppler equation (A3) (p = 1 to N) established at the position is solved to solve the equation (A2). The number of waves or beams (ie, the number of equations) N needs to be greater than or equal to the number of unknown displacement components. However, when the above block matching is performed, a plurality of equations (A3) are established from one wave or beam p as described above. Therefore, the measurement may be performed with a smaller number of waves or beams than in the case of using other displacement measurement methods.

At the same time, when regularization is also performed, when all of the equations (A3) established in a plurality of points of interest in the region of interest or the local region related to the points of interest are simultaneous, and the unknown vector u is a displacement component distribution The regularized weighted least squares solusion (RWLSQS) may be obtained by obtaining the following equation (A2). In this case, variation or ZZLB may be used as the regularization parameter (a value proportional to the variation, a value proportional to the power, etc.). Regularization is detailed in, for example, Patent Document 6. Variations in the propagation direction of each wave and displacement in the beam direction may be used as the regularization parameters for displacement in all directions, and variations in displacement in each direction estimated for each wave and beam may be used. It may be used as a regularization parameter for displacement in the direction of. For example, as an unknown three-dimensional displacement vector (Ux, Uy, Uz) ^T distribution, an unknown vector whose partial vectors are Ux, Uy, Uz, which are distributions of displacement components Ux, Uy, Uz in the x, y, and z directions. u = (Ux, Uy, Uz) When obtaining ^T , a matrix W having a variation in displacement Wp (p = 1 to N) in the beam direction as a diagonal component, or a variation in displacement Wpx, Wpy in each direction, When the matrices Wx, Wy, and Wz having diagonal components of Wpz (p = 1 to N) are used, the error energy E (u) and its solution u that are least squared are expressed as follows.

In addition, the variation and ZZLB may be averaged with respect to the measurement result of the displacement component obtained by simultaneously selecting the selected Doppler equations, and may be used for weighting in that case. The reciprocal number Wp (p = 1 to N) of the variation in displacement in the beam direction or the reciprocal number of the variation in displacement in each direction (Wpx, Wpy, Wpz) (p = 1 to N) is used to calculate the weighted average. Sometimes required.

  In addition to the steady process and ZZLB, the variation may be obtained based on an ensemble average under an unsteady process, may be obtained using a calibration phantom, or may be obtained from a measurement object itself. As described above, the regularization parameter and the weighted matrix are determined, but there are cases where the typical value is determined a priori based on the target, its state, measurement experience, and the like. This is not the case.

In this way, the weight value and regularization parameter can be set with high accuracy in a state having spatial resolution, but when the deformation is small or the amount of calculation is reduced, the region (wider than the point of interest or the local region ( For example, the entire region of interest or, for example, a partial region in the region of interest such as a partial region provided for each propagation direction distance or depth within the observation target) is estimated, and variation is estimated for each wave or beam. It may be set and processed globally. The phase matching method (Patent Document 6, Non-Patent Document 15) invented in the past by the inventor of the present application is required to make the measurement itself possible and to increase the measurement accuracy. For the conversion, other reported stretching methods are useful.
FIG. 19 shows motion compensation (phase matching) performed by moving a search region provided in a next frame to be processed using an estimated value of a displacement vector of a local region including a point of interest or a point of interest in a two-dimensional case. FIG. 19A shows translational motion compensation, and FIG. 19B shows motion compensation including rotation. In the case of three dimensions, the same processing is performed using a three-dimensional or two-dimensional local area or search area in a three-dimensional space.
When performing translation processing in phase matching (Non-Patent Documents 13 and 15), for example, each point of interest or each point of interest is set in an arbitrary orthogonal coordinate system such as a Cartesian coordinate system using a linear array probe. For each included local region, use the signal of the search region or region of interest (see FIG. 19 (a)) that includes the point of interest or the location of the local region that includes the point of interest in the next frame (referred to as frame Ne). . The spectrum is multiplied by the spectrum in the same manner as the phase rotation of the one-dimensional signal in method D3 of paragraph 0384. For example, in the case of two dimensions, the displacement vector of the local signal is (Δ ₁ , Δ ₂ ) (1 and 2 are two-dimensional Represents the axis of Cartesian Cartesian coordinate system), the complex exponential function exp {i (k ₁ Δ ₁ + k ₂ Δ) is added to the two-dimensional spectrum A (k ₁ , k ₂ ) of the wave signal in the search region. ₂ )} to shift the search region by (−Δ ₁ , −Δ ₂ ) in the direction opposite to the displacement vector, and the displacement vector of the local signal becomes (Δ ₁ , Δ ₂ , Δ ₃ ) in the three-dimensional case. (1 and 2 and 3 represent axes of a three-dimensional Cartesian coordinate system), it is complex in the three-dimensional spectrum A (k ₁ , k ₂ , k ₃ ) of the wave signal in the search region. Multiply by exponential function exp {i (k ₁ Δ ₁ + k ₂ Δ ₂ + k ₃ Δ ₃ )} to shift the search area in the direction opposite to the displacement vector by (−Δ ₁ , −Δ ₂ , −Δ ₃ ) (Patent Literature 6, Non-Patent Literature) 15 etc.). That is, when an inverse Fourier transform is applied to the multiplied spectrum, a local (time) space signal expressed in a Cartesian coordinate system phase-matched (shifted) at the same position is obtained. Incidentally, when shifting the local region in the direction of the displacement vector, exp {−i (k ₁ Δ ₁ + k ₂ Δ ₂ )} or exp {−i (k ₁ Δ ₁ + k ₂ Δ ₂ + k ₃ Δ ₃ )} may be multiplied, but in digital signal processing, since the cyclicity of the digital signal becomes a problem as described later, the wave signal in the search region Should be shifted.
When performing rotation processing in phase matching, the Cartesian coordinate system using, for example, a linear array probe is used in the same manner as in translation phase matching (see Non-Patent Documents 13 and 15, FIG. 19A). For any Cartesian coordinate system, such as, for each local area that includes each point of interest or each point of interest, a search that includes the position of that local point or area of interest in the next frame (referred to as frame Ne) The Fourier transform (ie, spectrum) of the polar coordinate system (the center of the polar coordinate system is the position of each point of interest or the position within or outside the region of interest) of the signal of the region or the region of interest (see FIG. 19B), It is obtained directly without approximation processing through the Jacobian operation implemented in the book.
That is, in the two-dimensional case, for example, when x = rsinθ and y = rcosθ, the Jacobian matrix is the reverse of the case of the Fourier transform expressed by the equation (22) (the inverse function theorem).
In the three-dimensional case, for example, when x = rsinθcosφ, y = rcosθ, and z = rsinθsinφ, the Jacobian matrix is the reverse of the case of the Fourier transform expressed by equation (27) (inverse function theorem).
(The origin of the polar coordinate system is a singular point), and the Fourier transform (spectrum) of the polar coordinate system is calculated directly in the same way with the signal of the local area including the point of interest or the signal at the same position in the frame Ne. The displacement of radial direction, polar angle, elevation angle, and azimuth angle estimated from displacement vector measurement methods such as local cross spectrum phase gradient (cross spectrum phase gradient method, Non-Patent Document 15) and multidimensional autocorrelation method Motion compensation is performed by applying a phase rotation by multiplying the Fourier transform (spectrum) of the polar coordinate system of the signal in the frame Ne in the Fourier space of the polar coordinate system by a complex exponential function in the Fourier space of the polar coordinate system using the vector component. And phase matching. For example, when the displacement vector of the local signal is estimated to be (Δ _r , Δ _θ ) in the two-dimensional case, the complex exponential function exp is added to the two-dimensional spectrum F (k _r , k _θ ) of the wave signal in the search region. _{{i (k r Δ r +} k θ Δ θ)} obtained by multiplying by search area displacement vector in the opposite direction to (-Δ _r, -Δ _θ) is moved by the displacement vector of the local signal in the case of a three-dimensional There _{(Δ r, Δ θ, Δ} φ) when it is estimated that the 3-dimensional spectrum F of the wave signal of the search area _{(k r, k θ, k} φ) to a complex exponential function exp {i (k _{r Δ r + k θ Δ θ +} k φ Δ φ)} obtained by multiplying by search area displacement vector in the opposite direction to _{(-Δ r, -Δ θ, -Δ} φ) is moved by. That is, a local signal expressed in a Cartesian coordinate system or a polar coordinate system phase-matched at the same position can be obtained from an inverse Fourier transform of this. That is, in the two-dimensional case, since k _x = k _r sin θ ′ and k _y = k _r cos θ ′,
In the three-dimensional case, k _x = k _r sin θ′cos φ ′, k _y = k _r cos θ ′ and k _z = k _r sin θ′sin φ ′,
It is.
In the local region and the search region, the point of interest is often set at the center, but the latter can efficiently provide the search region in the direction when the direction of tissue displacement is given a priori. The same applies to the purpose of phase aberration correction and motion compensation. When using, for example, a multidimensional autocorrelation method other than the cross-spectral phase gradient method, the (analysis) signal of each frame may be obtained by a polar coordinate system, and similarly, if Fourier transform using Jacobian operation is performed. good. In this way, rotational phase matching can be performed with high accuracy in the same manner as translational phase matching. Without approximation processing of digital signals and discrete Fourier transforms (discrete spectrum) expressed in any orthogonal coordinate system, such as when using sector scans or convex probes, by Fourier transform using the above Jacobian operation Any other orthogonal coordinate system (different Cartesian coordinate system such as Cartesian Cartesian coordinate system or various curved Cartesian coordinate system, origin is different or rotating, origin is different even in the same Cartesian coordinate system (Including the case where the position is different or rotated) (the exact interpolation approximation using phase rotation described in paragraph 0026, paragraph 0132, 0214, etc. is also highly accurate, It takes time to calculate). FIG. 20 is a flowchart showing an example of signal processing by Fourier transform using Jacobian arithmetic, but the above signal processing is not limited to this.
In phase matching, first, translation phase matching is first performed on a signal represented by each orthogonal coordinate system, and then rotation phase matching is often performed, but this is not a limitation. It may be carried out alternately or in the reverse order. Further, as described in Non-Patent Documents 13 and 15, each phase matching may be repeatedly performed (when the correction displacement amount becomes smaller than a preset threshold value, the repetition is terminated). There are also cases where stretching treatment is used.
Note that the local region and the search region are not necessarily rectangular but may have other shapes such as a circle (data is stored in a rectangular array, for example, a square, rectangular, cube, or rectangular parallelepiped array. In some cases, the array of positions that fall outside the actual area such as a circle or sphere may be zero-padded). The search area needs to be appropriately larger than the local area so that the signal circulated in the search area does not appear in the region of interest due to phase rotation by multiplying by the complex exponential function in the frequency domain. Only the amount increases, and it is determined a priori from the magnitude of the displacement vector to be observed a priori). Incidentally, when there is no displacement in the radial direction and the observation target is only the displacement in the rotation direction, the size of the search area may be the same as that of the local area. In addition, a search area may be provided in the previous frame. In addition, in order to shorten the processing time, phase matching may be performed by discrete shifting of a digital signal instead of phase matching by multiplying by a complex exponential function. In this case, it is not always necessary to perform motion compensation on the search area, and the local area may be directly searched (block matching) in the search area of another frame to perform phase matching.
In addition to the above-described phase rotation processing in the frequency domain of the polar coordinate system, the phase matching is not limited to the DAS processing described in paragraph 0384 (interpolation processing in method D1 or processing for performing phase rotation on the analysis signal in the spatiotemporal domain in method D2). In the same way as when shifting multidimensional signals based on delay processing (shifting through), phase matching (radial direction shifting and rotation) is performed on multidimensional analysis signals expressed in a polar coordinate system. Processing). The phase rotation process in the frequency domain of the polar coordinate system is based on the delay process of the method D3. These processes can also be used for DAS processing in the polar coordinate system, and can also be performed during other beam forming such as Fourier beam forming, adaptive beam forming, and minimum variance in the polar coordinate system. This is useful when shifting or rotating signals such as motion compensation, phase matching (including a new processing method), positioning, position correction, etc. in the time, space, and space-time coordinates.
For example, in the case of two dimensions,
f (r + r ₀ , θ + θ ₀ ) = f (r, θ) exp [j {k _r (r, θ) r ₀ + k _θ (r, θ) θ ₀ }] (2DASr)
In the case of 3D,
f (r + r ₀ , θ + θ ₀ , φ + φ ₀ ) = f (r, θ, φ)
× exp [j {k _r (r, θ, φ) r ₀ + k _θ (r, θ, φ) θ ₀ + k _φ (r, θ, φ) φ ₀ }] (3DASr)
Can be calculated. However, (k _r , k _θ , k _φ ) is the wave number in each direction at each position (r, θ, φ). That is, in the digital signal, analog shifting can be performed in a discrete polar coordinate system (high sampling frequency is desirable when high accuracy is required) by using the wave number in each direction at each position. As in the one-dimensional case, the accuracy can be higher than the method D1 (corresponding to block matching or fragment matching of signals in the spatio-temporal domain), and the accuracy is lower than other methods (method D3 and method D4). However, the calculation speed is fast. This is suitable when high calculation speed is required.
It should be noted that in these processes, the point spread function is shifted in the radial direction and the rotational direction at the same time as the observation target itself (which may be a phase matching error source). In addition, these processes may be performed on a signal having no carrier frequency (for example, image processing).

A Wiener filter can also be applied as Wp. In the spatio-temporal region, the signal itself is weighted directly, and signal imaging or displacement measurement is performed. The signal is a signal r (x, y, z) before or after detection.

  The noise signal n (x, y, z) can be statistically estimated by repeatedly collecting echoes for the object or the calibration phantom. For example, variation can be used, and estimation may be performed locally using an addition average or an ensemble average assuming a steady process. In some cases, the typical value is determined a priori based on the object, its state, measurement experience, and the like. This is not the case. Further, in order to detect the signal r (x, y, z) for imaging, when performing envelope detection, square detection, and absolute value detection, the expressions (A12) and (A13) are multiplied at each position. Sometimes. Similarly, when the self-function is obtained by multiplying the analysis signal by the conjugate of the analysis signal to obtain the power spectrum, weighting can be performed in the same manner. In addition, auto-correlation method and Doppler method, which are displacement measurement methods using analysis signals, and other pre-processing of signals before using cross-spectral phase gradient method or cross-correlation method (analysis signals may not be used) Can be used.

  Even when the signal is two-dimensional or one-dimensional, instead of r (x, y, z) and n (x, y, z) in equations (A12) and (A13), r (x, y) And n (x, y) and r (x) and n (x) can be processed in the same manner. In addition, in each beam or a region of interest obtained by scanning with each beam, Expression (A12) or Expression (A13) may be obtained and used on a global basis. In place of the expressions (A12) and (A13), the expressions (A4) to (A6) may also be directly used for echo weighting.

In particular, when the multidimensional cross spectrum phase gradient method (Patent Document 6, Non-Patent Document 15) is used, the Wiener filter can be applied not only in the spatio-temporal domain but also in the frequency domain. As described above, the frequency domain (ωx) of the cross spectrum Hp (ωx, ωy, ωz) (p = 1 to N) between the signals before and after the deformation or displacement acquired under the same conditions for each wave or beam. , ωy, ωz) to obtain the gradient (three-dimensional unknown displacement vector) of the phase spectrum θ (ωx, ωy, ωz) using the least square method,
However, PWpn (ωx, ωy, ωz) and PWps (ωx, ωy, ωz) are the power spectrums of noise and signal, respectively. The square (|| Hp (ωx, ωy, ωz) || ² ) may be used. q is an arbitrary positive value.
The least square is obtained by weighting. For example, in the equations (1) to (14 ′) of Patent Document 6, a description in the case where the square of the size of the cross spectrum (|| Hp (ωx, ωy, ωz) || ² ) itself is used for weighting. However, Wp (ωx, ωy, ωz) may be used instead of the weight. (As mentioned above, the variation in displacement in the beam direction and ZZLB may be used separately.) is there). Note that least squares are evaluated for each of N waves or beams with p = 1 to N and are least squared at each location of interest.

  Note that the noise power spectrum PWpn (ωx, ωy, ωz) can be statistically estimated by repeatedly collecting echoes for the object or the calibration phantom. In some cases, the typical value is determined a priori based on the object, its state, measurement experience, and the like. This is not the case.

  In addition, n (x, y, z) / r (x, y, z) represented in the expressions (A12) and (A13), and the expressions (A12 ′) and (A13 ′) PWpn (ωx, ωy, ωz) / PWps (ωx, ωy, ωz) is the reciprocal of the above-mentioned echo SN ratio SNRe or the combination of SNRe and SNRρ, which is the correlation SN ratio (Combined) SN It may be set based on the reciprocal of the ratio. Also, in a state where there is a spatial resolution, or in each region of interest or obtained by scanning with each beam, equations (A12 ′) and (A13 ′) are obtained globally, and equations (A12) and Similar to the equations (A13) and (A4) to (A6), it may be used directly for weighting the echo (imaging or displacement measurement). Further, when detecting the signal r (x, y, z) for imaging (envelope detection, square detection, absolute value detection, etc.), the expressions (A12) and (A13) may be used. However, in that case, the square norm of the first spectrum Hp (ωx, ωy, ωz) in the equation (where the spectrum of the signal extending over the local signal or the region of interest) may not be used. The same applies to the case of obtaining the autocorrelation function signal by multiplying the conjugate of the local spectrum Hp (ωx, ωy, ωz) by the spectrum Hp (ωx, ωy, ωz) to obtain the power spectrum.

  When the unknown displacement is a two-dimensional vector u = (Ux, Uy) and the unknown displacement is U (one) in the beam direction, H (ωx, ωy, ωz in Equation (A12 ′) and Equation (A13 ′) In the same way, weights similarly expressed using respective Wiener filters for the cross spectrums H (ωx, ωy) and H (ωx) between signals before and after deformation or displacement can be used.

  Further, when regularization is performed, the regularization parameter may be set by using the above-described variation or the like in accordance with Expression (10) or Expression (10 ′).

  When using the cross-spectral phase gradient method or other block matching methods, displacement vectors in two or more directions can be obtained using one wave or beam alone, or one wave or beam can be used independently. You can still configure an over-determined system.

  In addition, in any of the above displacement measurements, it is possible to perform the measurement without using an over-determined system, and even in that case, the above weighting and regularization may be performed.

The displacement is obtained from at least two signals. When the displacement is large in the above displacement (interesting point or local region including the interest point) measurement, the instantaneous phase (multi-dimensional or One-dimensional autocorrelation method, multi-dimensional or one-dimensional Doppler method, Non-Patent Document 13) and local phase (multi-dimensional or one-dimensional cross-spectral phase gradient method, Non-Patent Document 15) may be reversed. As described above, it is possible to observe tissue displacement and strain in the first place, instead of unwrapping the phase of the tissue, phase matching (spatial shifting or phase rotation multiplied by a complex exponential function) may be performed. It is also an epoch-making processing method, for example, C. Sumi et al, World Congress of Ultrasound in Medicine and Biology, Sapporo, 1994). In paragraph 0405, shifting processing in the radial direction and the rotation direction in the polar coordinate system by the same processing is also described. Various shifting processes that can be used for the delay process of the DAS process described in paragraphs 0384 and 0405 are also effective. Use cross-correlation-based multi-dimensional or one-dimensional cross-correlation method (block matching is effective in this case) and cross-spectral phase gradient method (process with coarse sampling interval) that enable estimation of large displacements Perform coarse estimation and perform phase matching (may be iteratively processed), then use those methods to make fine estimation (similarly it may be iteratively processed and cross In the spectral phase gradient method, the sampling interval may be restored to the original processing). As already described, it may also be used for phase aberration correction.
Various processes can be performed by modifying these as a base (for example, the demodulation method described in Patent Document 7). Basically, the autocorrelation method uses the phase of the complex autocorrelation function, and is obtained by multiplying the imaginary part / real part of the complex autofunction by the inverse tangent function based on Euler's formula to stabilize the estimation. Apply the moving average processing of time or space to the instantaneous phase (Method Ai), apply the moving average to the complex self-function in the same way, and multiply the imaginary part / real part by the inverse function of the tangent in the same way to obtain the phase Can be used (Method Aii). In the case of the Doppler method, in order to stabilize the estimation using the difference in instantaneous phase of the analysis signal itself, the instantaneous phase obtained by multiplying the imaginary part / real part of the analysis signal by the inverse function of the tangent, or the difference between them, Similarly, moving average processing can be performed (method D). The cross spectrum phase gradient method uses the cross spectrum phase of the local signal (Method C).
Among these, when the coarse displacement is estimated using the cross-correlation method and phase matching (spatial shifting) is performed, when processing is performed based on the method Ai and the method D, it is spatially ineffective. Displacement cannot be obtained correctly because the time or space moving average is applied to the instantaneous phase that may have a continuous distribution (error occurs, and the final result of phase matching is a discontinuous displacement distribution. turn into). Therefore, after phase matching (spatial shifting), for example, in 3D observation, the instantaneous frequency should be updated to (fx, fy, fz) and coarse estimation results (dx0, dy0, dz0) (Ux, uy, uz), and the equation is expressed as fx ux + fy uy + fz uz = θ, where θ is the instantaneous phase that may have a spatially discontinuous distribution before moving average processing In this case, θ ′ = θ + fx dx0 + fy dy0 + fz dz0 is calculated using a coarse estimation result (dx0, dy0, dz0) for the phase θ, and a coarse estimation result (dx0, dy0, Solve for fx dx + fy dy + fz dz = θ ″ by applying phase matching (corresponding to phase rotation) to add the phase of (dz0) and performing moving average processing to obtain θ ″ The estimation result of unknown displacement (dx, dy, dz) can be obtained directly (new phase matching). In those calculations, the instantaneous frequency (fx, fy, fz) may or may not be subjected to moving average processing. By this phase matching, it is possible to avoid adding the estimated value (ux, uy, uz) that cannot be obtained correctly to the coarse estimation result (dx0, dy0, dz0). Also, the instantaneous phase θ ′ after phase matching is not averaged, and the estimated result of unknown displacement (dx, dy, dz) can be obtained directly by solving the equation using θ ′ instead of θ ″. Yes, the same result as the result of adding the estimated value of the displacement (ux, uy, uz) to be updated to the coarse estimation result (dx0, dy0, dz0) is obtained. The same applies to two-dimensional observations and one-dimensional observations.
On the other hand, when the coarse displacement is similarly estimated using the cross-correlation method and phase matching (spatial shifting) is performed, when processing based on the method Aii, the spatially discontinuous distribution The moving average of time or space is not applied to the instantaneous phase that may be moving, and it does not matter if the moving average instantaneous phase has a spatially discontinuous distribution. . That is, for example, in the case of processing based on the method Aii in the case of three-dimensional observation, an estimation result that is coarse with respect to the moving averaged instantaneous phase θ ″ obtained after phase matching (spatial shifting) Phase matching that calculates the phase of coarse estimation result (dx0, dy0, dz0) by calculating θ '''=θ''+ fx dx0 + fy dy0 + fz dz0 using (dx0, dy0, dz0) (Corresponding to phase rotation) to obtain θ ''', fx dx + fy dy + fz dz = θ''' is solved and the unknown displacement (dx, dy, dz) estimation result directly The displacement to be updated by solving the equation fx ux + fy uy + fz uz = θ ″ using θ ″ instead of θ ′ ″ as before (new phase matching) , uy, uz) are obtained and added to the coarse estimation result (dx0, dy0, dz0) to obtain the estimation result. In these calculations, the frequency (fx, fy, fz) may or may not be moving average processed. The same applies to two-dimensional observations and one-dimensional observations.
In addition, when processing is performed based on the method D, when the coarse displacement is similarly estimated using the cross-correlation method and phase matching (spatial shifting) is performed, the phase characteristic (frequency) of the cross spectrum is obtained. (Characteristic) may have a spatially discontinuous distribution, but it will not be a problem because the moving average is not applied to the distribution (the frequency characteristics of the phase will be discontinuous in each local region) There is no). The equations related to displacement may typically be set up at the center of gravity frequency or in the vicinity of the center frequency (in the case of one-dimensional, two-dimensional, and three-dimensional, respectively, at least one, two, three, It may be necessary to stand in frequency), or may be combined in an over-determined manner within the signal band. Even in this case, after phase matching (spatial shifting), for example, in three-dimensional observation, the frequency within the signal band is (Fx, Fy, Fz), and the coarse estimation result (dx0, dy0, dz0) If the equation is expressed as Fx ux + Fy uy + Fz uz = α, where the unknown displacement to be updated is (ux, uy, uz) and the cross spectrum phase at the same frequency is α, the phase α For the coarse estimation result (dx0, dy0, dz0), calculate α '= α + Fx dx0 + Fy dy0 + Fz dz0 and add the phase of the coarse estimation result (dx0, dy0, dz0) By performing phase matching (corresponding to phase rotation) to obtain α ', Fx dx + Fy dy + Fz dz = α' can be solved to directly obtain the estimation result of unknown displacement (dx, dy, dz). (This is a new phase matching). Estimated amount of displacement (ux, uy, uz) to be updated by solving equation Fx ux + Fy uy + Fz uz = α using α instead of α 'as before To the coarse estimation result (dx0, dy0, dz0) Calculated to be estimated result is obtained. The same applies to two-dimensional observations and one-dimensional observations.

Multiple waves with different wave and beam forming parameters generated at the same position (physical waves generated by superposing waves with different wave and beam forming parameters in addition to those generated physically, (Including pseudo waves generated by frequency-splitting the spectrum), one equation is derived, and the same number of equations as the unknown displacement components are combined, or more than the same number of equations are combined and over -Determined system may be realized or equations derived at different positions may be solved simultaneously. When these equations are established, the above phase matching that makes the spatial distribution of those phases continuous is applied. It may be processed.
In particular, when the optimization process (paragraph 0402 and paragraph 0403, etc.) and other optimization processes described in the present application and other optimization processes are performed in order to increase or stabilize the displacement measurement (estimation), all displacement measurement methods are used. Should be processed after applying the above-mentioned phase matching to make the spatial distribution of phases continuous. First, the local average or variance or covariance is estimated by assuming a local stationary process with respect to the phase of the complex autocorrelation function, the instantaneous phase difference of the analysis signal, and the phase of the local cross spectrum. If the phase includes the above error, an error occurs. For example, this corresponds to the case where maximum likelihood estimation is performed (may be performed together with Maximum a posteriori (MAP)). Normal simultaneous equations or excess equations (over-determined systems) at the point of interest
And the likelihood function is
Therefore, log likelihood L is obtained by multiplying equation (LM3) by logarithm.
Get.
Incidentally, as super-resolution, a matrix F representing a blur function (considered as a point-spread function of a linear spatio-temporal invariant system or a linear spatio-temporal variable system), a vector O representing an original image (target), and a vector B representing a blur image Similarly, when performing maximum likelihood estimation when solving FO = B using
When the wave signal does not include direct current, the average value may be calculated as zero as in equation (LM9 ′) instead of equation (LM9). In the restoration of blurred images and super-resolution, it is necessary to pay attention because the calculation of the covariance matrix often takes time.
This processing in the spatio-temporal region is effective in the case of spatially variant. Averages the point spread function (one-dimensional autocorrelation function or multidimensional autocorrelation function in the depth direction or lateral direction) estimated from the point spread function at each distance position from the physical aperture. It is effective to estimate this (Non-patent Documents 35 and 36). A point spread function estimated at the position of interest without averaging may be used. For the processing in these spatiotemporal regions, for example, a conjugate gradient method can be used. When this maximum likelihood estimation is performed, MAP (Maximum a posteriori, for example, Non-Patent Document 42) described later is effective, but a method using an EM algorithm (Non-Patent Document 31) has also been reported. For these processing results, it is also effective to convolve a point spread function desired as shaping filtering in the spatio-temporal domain or to multiply the frequency response in the frequency domain.
In the case of processing in the spatio-temporal domain, if the spatio-temporal invariant of the point spread function can be assumed, devolution will be performed, but considering the calculation speed, the processing is performed in the frequency domain described in this application. It is better to perform the inverse filtering process in. In that case, the point spread function may be used after being averaged in a region considered to be space-time invariant. This applies to classical aperture synthesis where the spatial resolution is almost uniform or to receive dynamic focusing by performing plane wave transmission, but it is assumed that the spatio-temporal invariance occurs even when the focus beam is generated. The same processing may be performed in the frequency domain. Similarly, it is also effective to convolve the processing result with a point spread function desired as shaping filtering in the spatio-temporal domain, or multiply the frequency response in the frequency domain.
In addition, a posteiori estimates the variance from the displacement measurement result and determines the regularization parameter to be proportional to it (regularization, Non-Patent Document 18), or weights with the reciprocal as a weight (reliability of the equation) When the least square method is performed, an error occurs if the displacement measurement result includes an error due to the phase error.
Further, these statistics are implemented in an equation relating to the displacement (ux, uy, uz) to be updated with respect to the coarse estimation result (dx0, dy0, dz0). Therefore, the variation (used in power Doppler) derived by the one-dimensional autocorrelation method (Non-patent Document 20), which is a velocity measurement method in one direction, and the multidimensional self Variations derived with respect to the correlation method and Ziv-Zakai Lower Bound (ZZLB) are a priori and do not assume a steady process for displacement measurement, but also cause errors. When performing this type of optimization processing, it is necessary to perform the processing after performing the above-described phase matching that makes the spatial distribution of the phase continuous in all displacement measurement methods. Do not perform moving average processing or optimization on the displacement (residual displacement) itself to be updated during phase matching or the corresponding phase data. Even if this new phase matching is not necessary, several types of optimization methods can be used to obtain multiple estimation results, or they can be integrated or judged to obtain final results. There are some things that should be done in this way.
Here, MAP estimation effective in maximum likelihood estimation will be described, and the similarity to regularization will be described (Non-patent Document 42).
The MAP estimate of D in equation (LM1) is the a posteriori probability density function of D
However, p (θ | D) is a formula (LM3) of a posteriori probability density function (maximum likelihood estimation) of θ,
Is the probability density function of D.
Can be implemented with the maximum. This MAP estimation is a cost function as a weighted least squares method.
Is equivalent to minimizing and the solution is
Where P is a regularization operator and λ is a hyperregularization parameter.
Will be solved. As the regularization operator P, a unit matrix can be used, and the regularization parameter λ in this case can be spatially variable (Non-patent Document 17). Since this regularization operator is a full-band pass filter, the result of D may be smaller than the true value. As another regularization operator P, a high-pass filter or a differential filter (Laplacian operator G ^T G using a gradient operator G or its n-th norm) may be used. Although errors are effectively suppressed, high frequency components may be lost (but can also be used for blurry image restoration and super-resolution). Multiple regularization operators may be used simultaneously. For convenience, instead of using the derived formula (REG1), λ is used as a regularization parameter, a typical value is used, the variance of θ at the time of new phase matching, the variance of the difference between the left side and the right side of formula (LM1), In some cases, it is determined so as to be proportional to the variance (increasing the regularization parameter increases the regularization effect). In addition, the weighted least square method using the weight matrix W of the formula (A2) uses a reciprocal of the variance of D for W ^T W (emphasis is given to formulas with small variations in D and high accuracy). Increase).
From the similarity of the formula (MAP2) and the formula (REG1), it is also effective to use a mixture of both formulas. In these, even if E [D] is not a zero vector, it may be calculated as a zero vector for convenience.
In the restoration and super-resolution of a blurred image, when maximum likelihood estimation is performed in the system FO = B, the equations (LM7) to (LM9) are solved, and, similarly to the displacement measurement described above. It is possible to perform MAP estimation or use an EM algorithm, and it is also effective to process in the frequency domain as a space-time invariant system. As in the case of the displacement measurement described above, it is also effective to regularize and stabilize the system in the spatio-temporal region (Non-Patent Document 43), but high-speed processing is performed by the processing in the frequency domain disclosed in the same document. Is possible.
However, * represents conjugate, and here, the frequency response of the spatial distribution represented by each matrix or vector is represented using the same character. This document reports that regularization is more effective than ordinary Wiener filters. In the present invention, application of the Wiener filter described in the present application (including anomalous type) and spatiotemporal variant regularization (regularization parameter is spatiotemporal variant) are performed. Further, the shaping filter may be applied as described above.
This regularization is at the cost of reduced spatial resolution when the received signal has a low signal-to-noise ratio, processing between signals with different ultrasonic parameters or beamforming parameters, or processing between physically different sensing signals. However, such a smoothing process may be useful.
In addition, for example, optimization can be similarly performed in the inverse analysis shown in paragraph 0377 and various other inverse analyzes (when the system is expressed as Ax = b). In addition to maximum likelihood estimation, MAP, and regularization, Bayesian estimation can be performed in the same manner, and various other effective methods can be applied. Incidentally, when a vector such as a displacement vector or a current density vector is an observation target, another regularization parameter or another regularization operator may be used for each direction component (Non-patent Document 17).

The new phase matching process includes a plurality of waves with different wave and beam forming parameters generated at the same position (physical wave generated in addition to a pseudo wave generated by frequency-splitting the spectrum in addition to those generated physically) ) And the pseudo wave itself generated by superimposing those waves (widening and high resolution by coherent addition), or phase aberration correction during the beam forming process (high precision applying displacement measurement method) It is also effective in high-accuracy phase matching based on phase aberration measurement), and signal separation by ICA (Independent Component Analysis) processing (there is more effective multiplexing than averaging) and super-resolution by nonlinear processing Etc. are also effective. If there is tissue displacement in the phase aberration correction, motion compensation can be performed at the same time, and the received signal in a single frame received continuously when the observation target is clearly displaced or acquired continuously It is also effective to perform phase aberration correction during beam forming or after beam forming, and to perform super-resolution during beam forming or after beam forming, for received signals in multiple frames that are often generated (super-resolution to superimposed waves). Image processing and super-resolution results). It is also effective to process these signals between different sensing signals such as MRI, ultrasound, X-ray CT, OCT, terahertz and the like. In such a process using a plurality of frame data, a large amount of displacement or deformation of the observation target, particularly a lack of signal due to spontaneous displacement of the observation target under non-control (for example, the observation target is one-dimensional, two-dimensional or three-dimensional) Because the accuracy of phase matching between multiple frame data decreases due to physical action such as heating (treatment) and chemical action such as chemotherapy, the displacement measurement described in this application (shifting) Optimization including regularization and maximum likelihood estimation (including processing) is effective, but even in those cases, new phase matching is useful. The speckle signal may be processed or the specular signal may be processed. If necessary, edge extraction, enhancement, and feature points (for example, a tissue structure such as a blood vessel branch position when viewing a human) The obtained displacement tracking is effective. Alternatively, depending on the signal, it may be effective to perform smoothing in the above regularization or processing after performing envelope detection.
In this manner, the new phase matching processing includes DAS processing (methods D1 to D3) described in paragraph 0384, in addition to phase matching in displacement measurement, etc., and other types such as Fourier beam forming, adaptive beam forming, and minimum variance. Delay estimation in beam forming (phase aberration correction), phase aberration correction during beam forming described in paragraph 0372, motion compensation, alignment, position correction, etc. Signal shifting in time coordinates, space coordinates, and space-time coordinates Useful for estimating quantities.

There are various techniques to detect and image the movement of the target based on the observed waves. For example, in the field of medical ultrasound, based on the average velocity and dispersion of blood flow and tissue displacement and deformation. Some of them can display speed information, presence / absence of movement, complexity, and the like. A contrast agent (microbubble) is actively used, and measurement imaging may be performed in a state where the intensity of the wave from blood in the blood vessel or the heart chamber is increased. It may be useful not only for morphological observation but also for functional measurement. As a self-emanating contrast agent, a radioisotope used in PET (Positron Emission Tomography) is a typical example, and observation based on the count of the number of occurrences is performed. This is the target type of the passive device of the second embodiment. For example, a magnetic substance (which may have an affinity for a target such as a cancer lesion) is intravenously injected, and then mechanically there. A vibration may be applied to generate a magnetic field. Therefore, the stimulation is dynamically stimulated by the transmission transducer as the transmission means, and the electromagnetic wave is observed as the response by the reception transducer as the reception means. Moreover, the above-mentioned photoacoustic (photoacoustic) etc. are also possible. For example, ¹⁸ FDG ( ¹⁸ F-fluorodeoxyglucose, labeled with a positron-emitting nuclide) is a typical PET contrast agent, and cancer cells ingest more glucose (3 to 20 times) than normal cells. Applying properties, it is used for early detection of cancer in the whole body, but by applying photoacoustics (photoacoustics) to this, it can detect cancer early by receiving ultrasound (the integration mechanism by metabolic trapping is Yes, like glucose, it is taken into the cell membrane via the glucose transporter of the cell membrane and metabolized by the enzyme hexokinase, but unlike glucose, it stays in the cell without going into the glycolytic system.) Although it may be used in combination with PET, an ultrasonic examination may be performed separately from PET. The processing itself is based on reception beam forming for incoming ultrasonic waves (transmitted waves) using a trigger based on the timing of laser irradiation. A positron is emitted from a positron emitting nuclide (positron nuclide) due to β? Decay, attracts the electron, disappears by combining with the electron after moving several mm, and at that time, two photons emitted in almost opposite directions Although the spatial resolution is low by observing gamma rays (ie, annihilation radiation), there is an advantage that the portion that can observe the generated ultrasonic waves can be observed with high resolution. It is also suitable for early detection.It is also possible to determine the degree of malignancy and progression by observing the presence or absence of disease according to the presence or absence of accumulation, or by observing the extent from the intensity of the photoacoustic signal ( Malignant tumor cells have increased glucose metabolism and high accumulation). In addition to D-type glucose present in the body, “The Department of Integrated Functional Physiology, Hirosaki University Graduate School of Medicine outside the field of optical ultrasound, which applies the characteristic that cancer lesions specifically capture L-type to fluorescent L-glucose” (Lecture) Katsuya Yamada's research group results (oral or ingestion by injection) ”, the use of L-type glucose is also effective. In addition, for example, the brain has the highest glucose metabolism in the human body, and Alzheimer's dementia is accompanied by metabolic abnormalities from an early stage. In the myocardium, glucose metabolism increases (positive) when ischemia progresses, but glucose metabolism does not occur when necrosis occurs. Photoacoustic can also be used for these observations. In the case of the brain, there may be craniotomy, and when targeting diseases of deep organs in the abdomen, laser irradiation or near the disease, such as using a laparoscope (laparoscope) or catheter, etc. Ultrasonic detection may be performed. In many of these applications, the optical absorption frequency characteristics of contrast agents have been clarified, and in many cases, the frequency dispersion of the irradiation laser and the generated ultrasonic signal may be actively used (ie, Ultrasonic waves generated during laser irradiation in a wide band or a specific band are observed in a wide band as described below, or attention may be paid to a specific ultrasonic frequency band, or ultrasonic waves generated during laser irradiation in a different band It may observe sound waves in a wide band, focus on a specific ultrasonic frequency band at that time, or superimpose the observed ultrasonic signals to realize broadband laser irradiation in a pseudo manner. In some cases, ultrasonic sensors with the same characteristics in a wide band or a specific band are arranged in a one-dimensional, two-dimensional, or three-dimensional array. May be arranged in an array (for example, locally continuously, alternately, or periodically), and the light source and the ultrasonic sensor may have different bodies. May be integrated, or the light source and the ultrasonic sensor may be replaced and installed at the same location for observation.) Also, imaging is not always performed, and quantification based on numerical values Sometimes only observations are made. As described above, the glucose concentration is an observation target, and it can be applied to blood glucose level observation and imaging. In addition to sugar, PET contrast agents include oxygen, water, amino acids, nucleic acids, neurotransmitters and the like labeled with positron-emitting nuclides ( ¹¹ C-methionine, ¹¹ C-acetic acid, ¹¹ C-choline, ¹¹ C-methylspiperone, ¹³ N-ammonia, ¹⁵ O-water, ¹⁵ O-oxygen gas, ¹⁸ F-fluorodova etc.) have been put into practical use and have been developed separately such as those developed for Photoacoustics. It can also be used for various contrast media. In these photoacoustics, Doppler measurement (including vector measurement) may be performed on blood, urine, and body fluids with or without a contrast agent, and soft tissue or hard tissue Displacement and deformation of organs, viscoelasticity and thermodynamic characteristics may be observed (including not only diagnosis and examination but also various treatments). When exposed to radiation, as usual, it is necessary to prevent exposure and to reduce the amount of exposure to a safe value or less. Contrast agents can also have therapeutic effects. Conversely, the therapeutic agent may have the effect of a contrast agent.
Various contrast agents may be used at the same time, but may not be used. Ultrasonic sensors that have a wide-band reception characteristic are actively used. In some cases, the frequency band is selected by filtering (analog or digital) and used in the above application (including imaging of the photoacoustics signal itself). The observation results of the above application using the photoacoustics signal of each frequency or frequency band may be used by superimposing or averaging. In the case of imaging, a color may be assigned to the numerical value of the observation data to be displayed, or the same color may be displayed with shades to give resolution. In addition, the observed results at each observed frequency or frequency band may be imaged and displayed superimposed. In that case, a different color may be assigned to the observation result of each observed frequency or frequency band, and further, the resolution may be given to the numerical value of the observation data to be displayed with shading. Understand which contrast medium or observation target substance is the photoacoustics signal of each frequency band (It is also important to actually measure the dispersion of optical ultrasound, but for example human tissue or human lesion tissue Absorbance data from 400nm to 25μm of related substances is abundant and can be used as a reference), Photoacoustics signals in the frequency band suitable for those targets may be actively used, but not necessarily Useful (that is, when there are multiple markers, such as when there is at least one from within the observation target, at least one from outside the observation target, or when both exist together, In such a case, for example, when there is no marker without being aware of the marker, light having a bandwidth in which a Photoacoustics signal is generated is emitted). It may be imaged as described above, and may be used for observation of displacement and temperature described in the present application, and other inverse analysis (observation) using them. Further, as described in the present application, spectrum processing (analog or digital filtering), signal processing such as ICA (including the case where phase aberration correction is performed or not), and other image processing (for example, deterministic or probability statistics) May be used by separating into signals from different markers. It is also effective to use the difference in signal intensity or spectrum size (effective value) itself. It may be the marker analysis itself. In that case, the signal when the contrast medium is used and when it is not used may be targeted. Similarly, imaging may be performed as described above, and the separated signal may be used for the displacement and temperature observation described in the present application, and for other inverse analysis (observation) using them. In addition, for example, when imaging fluids in a medium that is stationary or moving slowly, such as blood flow, or observing their movement, the Photoacoustics signal itself or ultrasonic waves that may be used together (echo) Using Doppler observations on signals and separating them directly using the clutter rejection filter used in normal blood flow Doppler observations or differences in signal intensity, or identifying and separating blood flow positions (regions) Is also useful. Of course, this processing is also effective in the case of observing by setting the frequency and band of the irradiation light appropriately for the target fluid, and the OCT and other frequencies that match the frequency or band or that do not match the frequency. It is also useful to perform processing in combination with Doppler observation using an optical device (light pulse or electromagnetic wave pulse). Importantly, detailed evaluation is also possible for the media surrounding the separated fluid (displacement, temperature, inverse analysis, etc.). These are also useful methods in life analysis / analysis and synthesis.
For these Photoacoustics signals (received signals), various beam forming methods and signal processing described in this specification are used in addition to a known beam forming method. Therefore, the application includes imaging of the Photoacoustics signal itself as described above. For the detection process, a method described in this specification is used in addition to a known method. For signal separation, various signal processing methods such as ICA described in this specification can be used. For example, the spectrum can be divided, the beam spectrum can be divided, or the angular spectrum before beam forming can be divided. May be divided. When the angular spectrum is divided, various beam forming such as DAS processing can be performed in addition to Fourier beam forming. In superposition, coherent addition or incoherent addition is performed. In particular, if the beam forming method and signal processing described in this specification are used, weak signals can be processed without leaking, and detailed observation can be performed with high accuracy. Basically, because the photoacousics signal is broadband, not only can high-resolution observations (including the above-mentioned applications) be realized, but it can also be applied as a microscope. The ultrasonic sensor unit uses a handy photoacoustics microscope. It can also be realized. Even in this case, the above-described application is performed. In addition, light irradiation may be performed over a wide range such as plane wave, spherical wave, cylindrical wave, etc., and light beam scanning (mechanical scanning or electronic scanning) may be performed, the latter being more than the former. High-resolution observation is possible.
In addition, when the reception characteristics of the ultrasonic sensor are narrow, each Photoacoustics signal received using a plurality of ultrasonic sensors with different reception bands may be used as described above. Sometimes.
These observed photoacoustic signals are processed in the same manner instead of the ultrasonic echoes, and various signal processing (including inverse analysis) described in the present specification is applied to various applications. For example, Doppler observation, dynamic reconstruction, thermodynamic reconstruction based on temperature observation, and the like are not limited thereto.

  In addition, the wave is separated and detected before the last inverse Fourier transform (square detection, envelope detection, etc.), separated after the last inverse Fourier transform and then detected, or separated from the original Can be detected before and after Fourier transform (Non-Patent Document 1), and imaging representing the intensity distribution of each wave is performed, or incoherent signals resulting from the detection are superimposed. Emphasize deterministic signals (eg reflected or specular signals), reduce stochastic signals (eg scattered or speckle signals), and space in the structure of objects and media The change is effectively depicted (the past invention of the inventor of the present application).

  In some cases, a coherent signal with overlapping waves is detected and its intensity distribution is imaged. In addition, a non-detected coherent signal may be imaged to image the wave itself, or an image of a phase distribution obtained together with an image of signal strength (amplitude) may be presented. A single wave may be similarly imaged.

  Gray images and color images are popular (popular). If quantitativeness is required, numerical values corresponding to the displayed brightness and color may be displayed as bars. is there. In addition, it may be displayed as a bird's eye view or the like, or may be displayed together with CG. They may be displayed as still images or videos, videos may be displayed frozen, they may be displayed in real time, or processed and displayed offline. There is also. Wave data or image data stored in a storage device (or storage medium) may be read out and displayed. An arbitrary numerical change with time may be displayed as a graph.

  In addition, for example, it is also possible to observe the temperature distribution of the measurement object using a microwave, an infrared ray, or a terahertz band signal. The wave transmitted to the radiating object is modulated and detected (the passive device according to the second embodiment also measures the temperature distribution of the target from the radiated wave itself. Sometimes). As with other waves, spatial resolution can be obtained by using pulse waves, burst waves, and beam forming instead of continuous waves. Infrared rays are mainly used for observing the temperature distribution of the target surface ( In some cases, it may be considered that only the surface of the object is constrained), and if microwaves or terahertz is used, the temperature distribution inside the object can also be observed. Based on these observed physical quantities and chemical quantities, high-order processing such as an inverse problem approach is performed, and viscoelastic modulus, elastic modulus, viscosity (Patent Document 9), thermophysical property (Patent Document 10). , Electrical properties (conductivity and dielectric constant, Patent Document 8), magnetic permeability, wave propagation speed (light speed, sound speed, etc.), attenuation, scattering (forward scattering, backscattering, etc.), transmission, reflection, refraction, surface wave, Or a wave source etc. may be calculated | required including frequency dispersion. Patent Documents 8 to 10 disclose a method capable of reconstructing a physical property distribution related to a physical quantity from one physical quantity (observed quantity) in a region of interest. In addition, the physical property distribution may be directly evaluated from the wave itself directly sensed by the sensor. In medical applications, including the use of ultrasound and MRI, during the treatment of cancer lesions and heating / heating treatment, in addition to the temperature and thermophysical properties of the inflamed part after such treatment and surgery, observation of viscoelastic modulus And monitoring. In addition, body temperature observation (morning, noon, night, metabolism, growth, aging, before and after eating, before and after smoking, load on peripheral system, including electrophysiological nerve control, etc.), exercise load in various organs, etc. May be observed. It is not limited to medical applications, but other organic and inorganic substances and mixed substances may be the object of observation, and various observations and monitoring are linked in diagnosis, restoration, application, etc. May be implemented. The application of terahertz can be used for imaging of transmitted waves and reflected waves, as well as other waves, and can also be applied to Doppler measurements and the like. Characteristically, it can be applied to observation of inorganic substances as well as X-rays. Other waves may be used for observation of organisms and inorganics, but can be used simultaneously with other waves to create a fusion.

  Physical quantities such as measured displacement and temperature may be displayed in the same manner, but may be displayed superimposed on the morphological image obtained at the same time. An image representing these distributions is often required to be quantitative, and numerical values corresponding to the displayed luminance and color may be displayed as bars. In addition, it may be displayed in a bird's eye view or the like, or may be displayed in combination with CG. They may be displayed as still images or videos, videos may be displayed frozen, they may be displayed in real time, or processed and displayed offline. There is also. Wave data or image data stored in a storage device (or storage medium) may be read out and displayed. An arbitrary numerical change with time may be displayed as a graph.

  Further, additional information on the wave to be observed may be provided from another device through the input device, and observation data of other physical quantities or chemical amounts may be provided. In the digital signal processing unit, In addition to the above processing, data mining and independent signal separation (independent component analysis), principal component analysis, sign, multidimensional spectral analysis, signal separation by MIMO, SIMO, MUSIC, signal separation based on object identification by parametric methods, Super-resolution that may use these methods in combination, or higher-order processing such as ISAR (Inverse synthetic aperture) may be performed. In other words, super-resolution may be applied to the beam-formed (including aperture synthesis), or it may be applied to the signal that has not been subjected to receive beam forming or is not subjected to beam forming at all (transmission / reception signal for aperture synthesis). Beam forming may be performed after performing super-resolution processing. In each case, these methods may be used in combination.

  These processes are also performed in the passive device according to the second embodiment, and will be described in detail there. However, unlike the passive device, the active device according to the present embodiment has a wave motion. The position of interest can be specified in the received signal that is received is greatly different, and if transmission focus or multifocus is performed, the state and function of those focus positions, and the wave source there If there is any information about the wave source, it modulates and demodulates the waves with high resolution and understands them. Also, plane waves (flat arrays), cylindrical waves (ring-shaped arrays), spherical waves (spherical shell-shaped arrays) It is possible to capture them at a high frame rate and at high speed by using similar waves.

  In communication, the position of the communication destination can be narrowed down from the transmission transducer, and energy saving and communication security can be improved. In performing the observation, the degree of freedom is high in configuring the measurement system. Further, in the processing based on these system theories, it is easy to identify the point spread function to be generated and adjust it according to the purpose. It is possible to use multiple transmitting and receiving transducers (sometimes serving as transmitting transducers), and the waves to be transmitted and received may be the same or different. As mentioned above, a plurality of device bodies dedicated to a plurality of transducers operating in synchronization may be used, or a passive device according to the second embodiment may be used together. It may be connected to other devices including a device for controlling the network through a dedicated or normal network, or the device main body may have a network control function.

  Based on various observation data, devices such as materials and structures manufacturing devices, treatment and repair devices, and applied devices (robots, etc.) may operate in conjunction with each other, but are not limited thereto. . In addition, measurement and high-order calculation processing using these waves may be performed by another device using wave data stored in a removable storage device (storage medium). Data may be stored in the same type of storage device (storage medium) and used in another device.

  Note that if the received signal received and stored in the memory or storage device (storage medium) contains harmonic components generated in the target or medium, the fundamental wave or harmonics before the beamforming process is performed. A beam forming process (normal phasing addition) may be performed by separating a wave (sometimes only the second harmonic and sometimes dealing with multiple harmonics without ignoring higher-order components) However, it may be separated after beamforming is performed. Some of the separation methods separate the spectrum in the frequency domain, but the bands may overlap. So-called medical ultrasonic waves generate waves with opposite polarities in the simultaneous phase called the pulse inversion method. In the apparatus according to the present embodiment, when the reception signals for the respective transmissions are superimposed before or after beamforming, the second harmonic component can be extracted and the fundamental wave can also be obtained.

  In addition, a method of separating using a polynomial is also known. In the apparatus according to the present embodiment, one-dimensional processing of the wave propagation direction, or when the wave is modulated in the lateral direction, It is possible to perform multidimensional processing taking into account changes in position and can be performed before or after beamforming. However, in the case of performing beam forming after separation, when performing beam forming of each of the fundamental wave and the harmonic wave, each beam forming process is performed. Although processing may be performed, separation after beam forming is faster.

  On the other hand, when the wave transmitted from each transmission aperture is encoded, the wave generated from which transmission aperture element is generated with respect to the reception signal received by each reception aperture element when performing beamforming. The components are separated by signal detection based on a matched filter, and not only dynamic focusing for reception but also dynamic focusing for transmission may be performed, which is widely known. This is effective for high-speed transmission by plane wave transmission, and is also effective when a focus beam or steering is performed.

  When transmitting a plurality of waves or beams at the same time, for example, the above-mentioned plurality of waves having different frequencies and a plurality of different propagation directions are transmitted as encoded signals, and received signals May be decoded in the same manner and separated into received signals generated by their respective waves and transmission beams. This is effective, for example, in the case where the propagation directions are the same due to waves with overlapping bands, refraction, reflection, transmission, scattering, or the like. This is based on the basic idea of encoding the separated waves with another code. It may be simply encoded under the same physical parameters.

  In these, simultaneous equations can be solved, but the processing is fast and the effect of a matched filter can be obtained. Codes suitable for the target and medium have also been developed. However, as the number of elements used increases, the code length increases and the signal energy increases. It is important to make effective use of this, but on the other hand, for example, if the target or medium is deformed, the accuracy is increased. Is known to be unsuitable due to a decrease in the frequency, and the same problem occurs in chirp signal compression.

  In communication, information is encoded on the wave transmitted from each transmission aperture element, and then coded and transmitted (for example, a plane wave, a cylindrical wave, or a spherical wave is used as beam forming) If the information is widely communicated, focusing may be performed at multiple positions, the accuracy at those positions is guaranteed, and security may be ensured to communicate with local or specific objects, or energy may be saved. ) The received signal is subjected to beam forming and then decoded. The application of encoding in the apparatus according to the present embodiment is not limited thereto, but these processes are performed in a digital signal processing unit (also including a memory built-in type), a memory, or a storage device (storage medium). .

  In addition, physical quantities (size, direction, temperature, etc. of displacement, velocity, acceleration, strain, strain rate, etc.), chemical amounts, or additional information that are observed by the apparatus according to this embodiment or provided by others. In addition, viscoelastic modulus and elastic modulus related to wave, viscosity, thermophysical properties, electrical properties (conductivity) obtained by performing the above high-order processing such as an inverse problem approach (Patent Documents 8 to 10). Rate, dielectric constant), magnetic permeability, wave propagation speed (light speed, sound speed, etc.), attenuation, scattering, transmission, reflection, refraction, surface wave, wave source, material, structure, or their frequency dispersion Beamforming parameters (transmission intensity, transmission and reception apodization, transmission and reception delay, steering angle, transmission and reception time intervals (scan rate), frame rate, always or as appropriate or at fixed time intervals ,査線 number, number and shape and size and orientation and position of the effective aperture, the shape and the size and orientation of the aperture element, the physical opening orientation, or polarization mode, etc.) may be optimized. Thus, for example, spatially uniform quality (spatial resolution, contrast, scan rate, etc.), and certain targets (based on shape, material, structure, motion characteristics, temperature, humidity, etc.) can be detected High-quality (spatial resolution, contrast, scan rate, etc.) at the target position and related positions. Optimized beamforming is performed such as appropriately capturing waves, refracted waves, or surface waves, or observing from a wide range of directions.

  The wave propagation speed is determined by the physical properties of the medium, but the physical properties vary depending on the environmental conditions such as pressure, temperature, and humidity, and the physical properties are often inhomogeneous in the medium. It is. The propagation velocity may be measured in real time, and the propagation velocity can be obtained from the observed environmental conditions based on calibration data for the environmental conditions. The apparatus according to the present embodiment further includes a phase aberration correction unit that corrects the inhomogeneity of the propagation velocity, and substantially adjusts the transmission delay of each channel described above or the delay dedicated to correction during transmission. Phase aberration correction can be performed. Further, after reception, the digital signal unit can be corrected by multiplication with a complex exponential function in the digital signal unit in order to correct non-uniformity in propagation speed in the transmission and / or reception propagation path. Alternatively, it is also possible to perform correction directly in the calculation of the Fourier transform and the inverse Fourier transform. The reliability of the measured propagation velocity is determined by generating an imaging signal for the measurement object itself or a reference object that exists in the vicinity of the measurement object, and the imaging state, spatial resolution, signal intensity, contrast, etc. It can be confirmed as an index, and it may be further adjusted based on this. Also in the second embodiment, which will be described later, transmission and / or reception phase aberration correction may be performed after reception.

  A wave propagates and spreads under the influence of attenuation, scattering, transmission, reflection, refraction, and the like. Basically, the intensity of the wave decreases with the propagation distance. Therefore, in the apparatus according to the present embodiment, for example, based on Lambert's law, a function for correcting the attenuation of the signal before or after beamforming is installed, or the operator reduces the attenuation from the input apparatus. There is a case where a function capable of adjusting the correction at each position and each distance is provided. However, as described above, there is a case where a function of performing an optimal correction before or after the beam forming process in conformity with an object may be provided. In these processes, although the degree of freedom is low, analog processing by an analog device or a circuit may be performed instead of digital processing with an emphasis on high-speed processing.

  In the above processing, superposition and spectral frequency division were linear processing. However, after the generation or generation of the wave by the beam forming in the above methods (1) to (6), nonlinear processing is performed, A signal having wave parameters is generated. In the beam forming process, when the received signal is an analog signal, it is based on analog signal processing using an analog circuit (diode, transistor, amplifier, dedicated non-linear circuit, etc.), and when it is a digital signal, digital using a digital signal processing unit Based on the signal processing, the received signal may be subjected to a power operation, multiplication operation, or other non-linear processing. In the frequency domain, nonlinear processing may be performed on the spectrum.

  In addition, as a modification of DAS, DAM (Delay and Multiplication) processing, which is the inventor's invention, may be performed in the frequency domain in the apparatus of the present invention. Calculation of products such as power and multiplication in the space-time domain can be performed by convolution integration in the frequency domain. For signals that have a higher frequency, a wider band, simulated harmonics, or a steered wave, it is possible to obtain a signal that has been detected from at least one arbitrary direction in all directions. For example, the resulting wave In some cases, a displacement vector can be measured using a normal one-direction displacement measurement method.

  It is also possible to generate an imaging signal using a virtual source. As for the virtual source, there have been reports in the past of installing a virtual source before the physical aperture and installing a virtual source at the transmission focal position, and the inventor of the present application is not only a virtual source but also a detector. Have been reported to be installed at an arbitrary position, and a physical source and detector of a wave can be installed at an arbitrary position of an appropriate scatterer or diffraction grating (Patent Document 7, Non-Patent Document 8). The invention can also be implemented in these virtual sources and virtual detectors as described above. It is possible to increase the spatial resolution and widen the field of view (FOV). In addition, when performing transmission or reception or transmission / reception beamforming on a reception signal obtained by transmission using an aperture of one or more elements (when not performing beamforming, transmission / reception for aperture plane synthesis) A plurality of wave parameters, a plurality of beam forming parameters, and a plurality of transducer parameters (element shape and size, arrangement, number, effective aperture width, element material, etc.) are different from each other. By doing this, multiple beams or waves with different characteristics can be generated (including obtaining multiple beams or waves from the same received signal), and an over-determined system can be constructed. Similarly, an over-determined system can be configured by changing the position and distribution (shape, size, etc.) Kill. In this case, a plurality of beams or waves having different characteristics may be generated from the same received signal. The characteristics of the dominant decision system, such as high signal-to-noise ratio and high resolution due to their coherent superposition, and speckle reduction due to incoherent superposition through their detection, may be effective for imaging. In addition, the effect of improving the accuracy of various measurements such as displacement measurement and temperature measurement can be obtained. Along with the virtual source and the virtual receiver, at least one of the plurality of wave parameters, the plurality of beamforming parameters, and the parameters of the plurality of transducers may be different (eg, electrical or electronic or mechanical). To change the steering angle physically or softly).

A coordinate system in which the wave is rotated by a coordinate system determined by the receiving aperture element array around an arbitrary position or spatially shifted by an arbitrary wave source (for example, the coordinate of the axis and the horizontal axis of the transmission aperture) In some cases, the beam forming is performed after correcting the coordinates of the received signal. For example, when it is desired to directly generate an imaging signal in a state where the above-described two-dimensional Cartesian coordinate system (x, y) is rotated by θ around the origin, an analysis signal obtained by the first time Fourier transform However, it is only necessary to proceed with the calculation by multiplying by equation (29), rather than performing the rotation of the wave vector (kx, √ (k ² -kx ² )) and coordinates (x, y) and the Jacobian. The image signal can be generated at high speed without losing the high speed achieved by the present invention.

However, in the case of a reflected wave, s = 2, and in the case of a transmitted wave, s = 1. If the transmission is substantially corrected, it may be carried out with s = 1. Spatial shifting (translation) can also be performed by multiplying a complex exponential function in the frequency domain. The above-described method for calculating the wave vector (kx, √ (k ² -kx ² )) and coordinates (x, y) and calculating the Jacobian is a transmission beamforming involving conversion to a coordinate system determined by the receiving aperture element array. (S = 1) is performed, and under the circumstances, reception beamforming (s = 1) is performed and the speed is low.

  In the active type device according to the present embodiment, the same applies to the passive type device according to the second embodiment to be described later, but as an analog device, it may be incorporated in the transducer or the device body. Lenses and reflectors (mirrors), scatterers, deflectors, polarizers, polarizers, absorbers (attenuators), multipliers, conjugates, phase delay devices, adders, differentiators, integrators, matching devices, Special devices such as filters (space or time, frequency), diffraction gratings, spectrometers, collimators, splitters, directional couplers, or nonlinear media, wave amplifiers may be used in combination. In addition, for light, polarizing filter, ND filter, shield, optical waveguide, optical fiber, optical Kerr effect device, nonlinear optical fiber, optical mixing optical fiber, optical fiber for modulation, optical confinement device, optical memory, dispersion shift Optical node technology, optical cross-connect (OXC), optical fiber, bandpass filter, time inverter, encoding with optical mask, etc., and optical control (wavelength conversion, switching, routing) of them An optical add / drop multiplexer (OADM), an optical multiplexer / demultiplexer, or an optical switch element is used, and the device itself may be an optical transmission network or an optical network. This is not the case. In beamforming, they are to be controlled with the device either personally, naturally, or equally optimally under the mechanism described above. In the frequency domain, nonlinear processing may be performed on the spectrum.

  Also, under such a combination, the device according to the present invention is also used in a normal device using waves. Examples of medical devices include ultrasonic diagnostic devices (including reflection / echo methods and transmission types), X-ray CT (contrast agents that enhance attenuation effects may be used), X-ray X-rays, Angiography, mammography, MRI (Magnetic Resonance Imaging, contrast media may be used), OCT (Optical Coherent Tomography), PET (Positron Emission Tomography, applicable to the second embodiment), SPECT (Single Photon Emission Computed) Tomography), endoscopes (also capsule type), laparoscopes, catheters equipped with various sensing functions, terahertz imaging devices, various microscopes, various radiotherapy devices (chemotherapy may be used in combination to enhance therapeutic effect) ), SQUID meter, electroencephalograph, electrocardiograph, HIFU (High Intensity Focus Ultrasound), and the like. Above all, the nuclear magnetic resonance imaging apparatus is originally a digital apparatus, and its application range is very wide including its capability. For example, using the electromagnetic wave observation and inverse problem that the inventor is working on, current distribution and electrical property reconstruction (measurement), observation of displacement and mechanical wave propagation, mechanical property reconstruction (measurement), temperature It can also be applied to all observations of distribution and heat wave, and reconstruction (measurement) of thermophysical properties (Patent Documents 8 to 10). Patent Documents 8 to 10 disclose a method capable of reconstructing the distribution of physical properties related to a physical quantity from one physical quantity (observed quantity) in a one-dimensional, two-dimensional, or three-dimensional region of interest. The observed physical quantity is a surface wave (electromagnetic wave, elastic wave, thermal wave, etc.) or a physical quantity at the boundary, and their physical properties may be similarly reconstructed based on the observation. When terahertz is used, an electric field can be observed, and current density, electrical properties, and the like can be observed. Doppler observation using terahertz is also important. In addition, the physical property distribution may be directly evaluated from the wave itself directly sensed by the sensor. Regarding these, in addition to the nuclear magnetic resonance imaging apparatus, an approach using ultrasonic waves or the like is being carried out, and the same applies. As another approach, for example, in OCT, absorption spectra can be measured, and based on infrared spectroscopy, for example, basal cell carcinoma of the skin, oxygen and glucose concentrations in blood can be imaged. become. Although application to normal Near InfraRed (NIR) is also possible, it is possible to capture the distribution with higher spatial resolution as compared with reconstruction based on so-called NIR. Also, in these cases, an ultrasonic sensor device (also a microscope) may be used in combination with OCT or a laser device to perform photoacoustic imaging, and the application is not limited thereto. In addition, using a laser or OCT device, imaging may be performed with high sensitivity to fluctuations in the tissue when mechanical stimulation is not given (observation of surface waves such as Doppler observation and its application) There is also.) In addition, responses to all (dynamic) stimuli including those caused by laser light or the like may be targeted for imaging (including observation using dynamic light generated using light). In other imaging, a chemical sensor or the like may be used. The combination of waves is not limited to these, and another sensor such as a chemical sensor may be used in combination with the physical sensor. The apparatus according to the present invention is also used in various radars, sonars, optical system apparatuses, and the like. The wave is not limited to a pulse wave or a burst wave, and a continuous wave may be used. Also, digital processing with a high degree of freedom may be realized and used by a dedicated analog circuit with a fast operating time, and vice versa. There are various devices in each field such as resource exploration, nondestructive inspection, and communication fields, and the device according to the present invention is also used in these devices. The apparatus of the present invention can be used in a normal apparatus as an apparatus and with respect to operation modes (for example, an imaging mode, a Doppler mode, a measurement mode, a communication mode, etc.). It is not limited.

When any beam or wave, such as the above-mentioned fixed focusing beam, multi-focusing, or other plane wave, is transmitted physically at the same time, a high frame rate can be obtained if it can be transmitted to a wide range at once. realizable. There are cases where the same effective aperture is simultaneously transmitted in a plurality of directions, and cases where different effective apertures are simultaneously transmitted in the same direction or different directions. In addition to the case where the steering angle and focus position are the same or different, the ultrasonic frequency and bandwidth (beam direction, wave propagation direction, direction orthogonal to them), pulse shape, wave number, aperture shape and apodization The same or different beam forming parameters such as the beam shape due to the same or different transducer parameters such as the element shape, size and arrangement state may be transmitted simultaneously.
In a physical multiple transmission, when these parameters are different, the following can be considered as a typical case.
(A1) When the same soft steering is applied to all.
(A2) When a plurality of different soft steerings are performed (for example, when the same steering is performed softly at different transmission steering angles).
When these parameters are the same, the following can be considered as a typical case.
(B1) When performing soft steering.
(B2) When performing a plurality of soft steering operations.
However, they may be implemented in combination. So-called adaptive beamforming may be performed due to obstacles in the propagation process and the influence of scattering and attenuation (including cases depending on frequency). At that time, if the same combination of software transmission and reception steering and apodization is implemented, they are processed at a time in a state where they are superimposed. In addition, when different combinations are included, each is processed at a time in a state where the combinations to be implemented are overlapped for each same one, and are overlapped before the last inverse Fourier transform.
In the case of (A1) and (B1), one software process can be performed on the received echo signal received as a superposition of echo signals for each transmitted ultrasonic wave.
In the case of (A2), the signals are classified into echo signals that are subjected to the same software processing, and are superposed for each one subjected to the same soft steering, and the software processing is performed once for each. They are superimposed before the inverse Fourier transform of. The signal separation may be performed using the above-described various methods, and is not limited thereto.
In the case of (B2), a plurality of different soft processes are applied to all the overlapped angular spectra, and they are superimposed before the last inverse Fourier transform.
In addition, when these beams and waves are not transmitted physically at the same time, if the target time phase is the same, or if a plurality of transmissions / receptions are performed under that assumption, the above simultaneous May be processed according to the transmission case. In addition, when the same combination of steering and apodization of software transmission and reception is implemented, they are superimposed and processed at once, and implemented when different combinations are included Each combination is superposed and each is processed at once and overlaid before the final inverse Fourier transform. What was sent simultaneously and what was not sent at the same time may be treated similarly under the same conditions or assumptions described above. Note that these parameters in physical transmission may be known in advance, or may be used after the beam or wave is analyzed. This also applies to the passive type described later.
By performing simultaneous or non-simultaneous transmission of multiple beams and waves, it is possible to achieve a high frame rate and focusing at the same or multiple locations, as well as to generate beams and waves with new parameters based on the same processing including overlay processing. It can be generated (for example, high resolution by broadening the bandwidth), and with the frequency division processing of the spectrum, a beam or wave having a new parameter can also be generated, and the beam or wave generated by them can be parameterized. May be used separately (for example, measurement of displacement in a generated beam direction or wave propagation direction or displacement vector measurement). There is a case where the band-width based on the nonlinear or linear processing described later is performed on the superposed state, the spectral frequency-divided one, or the separated one. In addition, superposed or spectral frequency-divided, separated, non-linear or linearly processed ones may be used for displacement measurement or the like. Each of them may be detected and imaged, or they may be superimposed and imaged (eg, speckle can be reduced). Applications are not limited to these and are various as described above, and are not limited thereto.

<Simulation results>
The following mainly shows the results of confirming the feasibility of the beam forming methods (1) to (7) by simulation when the wave is ultrasonic waves (plane wave transmission and monostatic opening during steering). In addition to surface synthesis, multi-static aperture surface synthesis, image signal generation by fixed focusing, image signal generation in Cartesian coordinate system during transmission and reception in polar coordinate system, result of migration method).

  FIG. 21 is a diagram showing a numerical phantom used in the simulation. Here, a numerical phantom including five point scatterers existing at an interval of 2.5 mm at a depth of 30 mm in an echo-free and non-attenuating medium was handled. Field II (see Non-Patent Document 21) was used to generate the echo signal. Here, the depth direction is the z-axis and the horizontal direction is the x-axis.

  In the plane wave transmission, the migration method, and the monostatic aperture surface synthesis, a one-dimensional linear array transducer (128 elements, element width 0.1 mm, gap 0.025 mm, slice direction thickness 5 mm) was used. In fixed focusing and multi-static aperture synthesis, a one-dimensional linear array transducer (256 elements, element width 0.1 mm, gap 0.025 mm, slice direction thickness 5 mm, effective aperture width 33 to 129 elements) was used. A convex transducer (128 elements, element width 0.1 mm, gap 0.025 mm, slice direction thickness 5 mm, curvature radius 30 mm) was used for transmission and reception in the polar coordinate system. The center frequency of the emitted ultrasonic pulse is 3 MHz, and the sound pressure waveform is shown in FIG. The deflection angle is defined with respect to the depth direction of the front, and will be represented as “θ” in the following.

(1) Transmission of deflection plane waves FIG. 23A (respectively, (a) to (d)) shows simulation results when deflection plane waves having deflection angles θ = 0 °, 5 °, 10 °, and 15 ° are transmitted. . Further, FIG. 23B shows a simulation result when interpolation approximation is performed in wave number matching when the deflection angle is θ = 0 °. These are the results of receiving at the same angle. In FIG. 23A and FIG. 23B, the horizontal axis represents the position [mm] in the horizontal direction (Lateral x), and the vertical axis represents the depth (Depth) z [mm]. As shown in FIG. 23A, it is also possible to confirm that the formed echo image is obtained and further deflected. Both are results of down-sampling from 100 MHz to 10 MHz in the frequency domain (paragraphs 0208, 0209) and generating image signals at intervals corresponding to the sampling frequency of 25 MHz (the same applies to others).
On the other hand, interpolation approximation is performed in wave number matching when the deflection angle is θ = 0 °, and FIG. 23B (e) shows sampling frequencies of 100 MHz (left) and 25 MHz (right) when replaced with nearby spectra. FIG. 23B (f) shows the results when the sampling frequency is 100 MHz (left) and 25 MHz (right) when linear interpolation approximation is performed on the spectrum. The image was more stable when the sampling frequency was high and linear interpolation approximation was performed, but the image was not as good as FIG. 23A (a) when interpolation approximation was not performed. When the deflection angle was set to a non-zero degree, an unstable result was obtained.

  24 and 25 show the result of calculating the obtained deflection angle from the spectrum of the generated image signal. For this evaluation, the number of scatterers in the numerical phantom was increased, and 300 scatterers were randomly arranged at a depth of 0 to 40 mm. The reflection coefficient of each scatterer was set to a random value of −1 to 1. An error of 0.5 to 0.8 degrees was confirmed regardless of the set deflection angle. The error depends on the position of the scatterer relative to the generated wave. Increasing the number of scatterers improves accuracy (omitted).

  FIG. 26 shows a result of superimposing a plurality of images obtained at different deflection angles. The deflection angle is set at 1 ° intervals, and 1 wave (0 °), 11 waves (−5 ° to 5 °), 21 waves (−10 ° to 10 °), and 41 waves (−20 ° to 20 °) Each was superimposed. FIG. 27 is a diagram in which the distribution in the horizontal direction of the point spread function estimated from the generated image signal is plotted. In FIG. 27, the horizontal axis represents the position (mm) in the horizontal direction (Lateral x), and the vertical axis represents the relative value of brightness (Brightness). As shown in FIG. 27, it can be confirmed that the resolution is improved as the number of superpositions is increased.

Migration method (Applying method (6) to beamforming during transmission of the same plane wave)
FIG. 28 shows the result of generating an image signal by the migration method according to the present invention. The deflection angles were set to θ = 0 °, 5 °, 10 °, and 15 ° as in FIG. 23A. In wave number matching, the result of interpolation approximation is omitted, but the image is unstable.

(2) Deflection Monostatic Type Aperture Synthesis FIG. 29 shows a simulation result at the time of deflection by monostatic type aperture synthesis of method (2). Similar to FIG. 23A, the deflection angles were set to θ = 0 °, 5 °, 10 °, and 15 °. As shown in FIG. 29, it can be confirmed that an image is formed and deflected.

(3) Multistatic Type Aperture Synthesis FIG. 30 shows a simulation result by multistatic type aperture synthesis of the method (3). FIG. 30 (a) shows a low-resolution image generated using only signals (that is, one set) received with the receiving element equal to the transmitting element (that is, the same as the monostatic type). FIG. 30B shows a result of superposing 33 sets of results in which 16 elements on the left and right sides are used for reception in addition to the element at the transmission position. FIGS. 30C and 30D show the result of superimposing 65 sets (32 elements on the left and right of the transmitting elements) and the result of superposing 129 sets (64 elements on the left and right of the transmitting elements), respectively. As shown in FIG. 30, it can be confirmed that the image is formed. Moreover, the result of having plotted each point spread function is shown in FIG. From FIG. 30 and FIG. 31, it can also be confirmed that the side lobe is suppressed as the number of overlapping is larger, and the resolution is higher.

(4) Fixed Focusing FIG. 32 shows the result of fixed focusing transmission. Here, method (1) was used. FIG. 32A shows the result of superimposing the echo signals received at each transmission effective aperture and performing one echo signal generation process. FIG. 32B shows a result of generating and superposing low-resolution echo signals for each effective aperture width. FIG. 32 (c) shows the result of generating and superimposing echo signals with a set of the same positional relationship in transmission and reception as in the multi-static aperture plane synthesis. As shown in FIG. 32, images are formed in any case, and no particular difference is seen. Method (1) is faster and more effective than the other two methods. In addition, the result of the method (1) shows that reception beam forming is possible even using reception signals when ideally transmitting a plurality or all of the beams simultaneously (for a transmission beam having interference). Received signals can also be processed and high frame rates can be achieved). This processing is not limited to fixed focusing transmission, but can be performed even when a plurality of transmissions of all types of waves (including combinations of different waves) are included. In other words, there may be cases where multiple waves include those with different transmit beamforming, cases where beamforming is present or not, and cases where different types of waves (electromagnetic waves, mechanical waves, thermal waves, etc.) are included. However, there may be cases in which processing such as nonlinear processing, detection processing, super-resolution, adaptive beamforming, minimum variance processing, or signal separation is performed. These processes may be performed during beam forming. Of course, the received signal for each transmission may be superimposed. Interpolation approximation processing may also be performed in wave number matching in these cases.

(5) Generation of image signal in Cartesian coordinate system for transmission and reception in polar coordinate system (5-1) Cylindrical wave transmission Echo signal when transmitting ultrasonic wave from all elements of convex array simultaneously and transmitting cylindrical wave in frequency The result of processing in the area is shown in FIG. Actually, as described in (5-1 ′), a plane wave or a virtual linear array is generated at a position of a depth of 30 mm in transmission and reception. As shown in FIG. 33A, it can be confirmed that the scatterer has been imaged.
(5-1 ′) Cylindrical Wave Transmission Using Linear Array Next, an echo signal when a cylindrical wave is transmitted using a linear sound source and a virtual sound source (FIG. 8A (a)) set at the position behind the linear array. The result of generating is shown. FIG. 33B shows the result of using the method (1) described in the method (5-1 ′) with the virtual sound source 30 mm behind, and FIG. 33C shows the virtual sound source. The result of using the method (2) described in the method (5-1 ′) at a position 60 mm rearward is shown. It can be confirmed that the scatterer has been imaged.
In addition, when a linear array type transducer is used, the method (1) described in the method (5-1 ′) is used to generate a cylindrical wave using a virtual source located 30 mm behind the physical aperture. FIG. 33 (d) shows the result when a plane wave or virtual linear array type transducer (FIG. 8B (g)) extending in the lateral direction is generated at a distance position of 30 mm (FIG. 8B (g)).

(5-2) Fixed Focusing FIG. 34 (a) and FIG. 29 (b) show the results of processing the received signal when fixed focusing is performed at a distance of 30 mm from each element (FIG. 14 (a)) using a convex array. . FIG. 34 (a) shows the result of superimposing received signals obtained at each effective transmission aperture and performing one echo signal generation process. FIG. 34 (b) shows a low resolution for each transmission. The result of generating and overlaying images is shown. Similar to multi-static aperture plane synthesis, echo signals are generated and superimposed with the same positional relationship in transmission and reception as a set, but the result of superimposing is omitted, but these three operations are almost the same as in (4). I hesitated the result. FIG. 34 (c) shows the result of performing echo signal generation processing once on the received signal when the depth of 30 mm is fixedly focused (FIG. 14 (b)). The scatterer was well imaged.
These results were obtained in the same manner as in (4), and it was shown that reception beam forming is possible even using reception signals when multiple or all beams are ideally transmitted at the same time. (The received signal for the transmission beam with interference can be processed, and a high frame rate can be realized). This processing is not limited to these fixed focusing transmissions, but can be performed even when a plurality of transmissions of all types of waves (including combinations of different waves) are included. In other words, there are cases where multiple waves include those with different transmit beamforming, cases with and without beamforming, and types of waves (electromagnetic waves, mechanical waves, thermal waves, etc.). In some cases, processing such as nonlinear processing, detection processing, super-resolution, adaptive beamforming, minimum variance processing, or signal separation is included. These processes may be performed during beam forming. Of course, the received signal for each transmission may be superimposed. Interpolation approximation processing may also be performed in wave number matching in these cases.

  The beam forming using the digital Fourier transform according to the present invention performed in the above simulation is based on the appropriate use of complex exponential multiplication and Jacobi calculation, and arbitrary beam forming processing in an arbitrary orthogonal coordinate system. It was proved that it can be realized with high accuracy without interpolation approximation. Any of the beam forming can be realized by using the DAS (Delay and Summation) method. However, the beam forming according to the present invention is speeded up by the difference between wave number matching and lateral Fourier transform, and can be used for a general purpose in a one-dimensional array. When a PC is used, the calculation time is significantly faster than 100 times. If the aperture elements form a two-dimensional or three-dimensional distribution, or a two-dimensional or three-dimensional array, the above method may be further increased in number of dimensions, and more processing can be performed than in the case of a one-dimensional case. This solves the problem that it requires, and the high speed becomes more effective. In addition, an example in which superposition or the like at the time of plane wave transmission with different deflection angles is effective has been described. The effect of increasing the resolution and increasing the contrast by suppressing the side lobes can be obtained at high speed.

  In the above example, it has been confirmed that arbitrary focus (including no focus) and steering can be performed in any array type aperture surface shape, and arbitrary beam forming processing in an arbitrary orthogonal coordinate system can be performed at high speed without interpolation approximation. It was confirmed that it could be realized with accuracy. The time for obtaining high-order measurement results such as displacement measurement based on the generated image signal is also shortened, and the effect of improving the measurement accuracy is also obtained. In the present invention, as described in the methods (1) to (7), interpolation approximation processing may be performed in wave number matching of arbitrary beam forming, and beam forming may be performed at a higher speed. In order to perform approximate wave number matching with high accuracy, it is necessary to appropriately oversample the received signal at the cost of an increase in the amount of calculation. In that case, it is necessary to be careful that the number of data of the Fourier transform increases, unlike the case where the signal at an arbitrary position can be selectively generated when the interpolation approximation process is not performed.

  As described above, the example using the representative transducer, the reception sensor, the transmission unit and the reception unit, the control unit, the output device, the external storage device, and the like in the first embodiment has been described. The fact that the beam forming of the methods (1) to (7) was possible proved that arbitrary beam forming based on focusing and steering can be performed in an arbitrary orthogonal coordinate system, and the apparatus of the present invention. The beam forming and applications that can be realized using the above are not limited to those described in the others.

<< Second Embodiment >>
Next, the configuration of a measurement imaging apparatus or a communication apparatus according to the second embodiment of the present invention will be described. FIG. 1 is a representative block diagram showing a configuration example when the device according to the first embodiment is an active type, and FIG. 2 is a representative block diagram showing a detailed configuration example of the device main body. However, in the second embodiment, a passive device is used. Therefore, the device according to the second embodiment does not include at least a transducer for transmission in FIG. 1, and further transmits from the control unit. It does not have a wired or wireless path for sending drive signals to the transducer.

  In the case of the active device according to the first embodiment, the detailed configuration example of the device and unit has been described with reference to FIGS. 1 and 2 as a representative configuration. However, the active device has an arbitrary opening shape. The transmission and reception transducer array devices (transducers may be used for both transmission and reception) are necessarily used, while passive devices are used in them in any shape of the transmission transducer array device. Do not use.

  In other words, the basic configuration of the device according to the second embodiment includes a receiving transducer (or receiving sensor) 20 that is a receiving means, a device main body 30, an input device 40, an output device (or display device) 50, an external device. And a storage device 60. The apparatus main body 30 mainly includes a receiving unit 32, a digital signal processing unit 33, a control unit 34, and a storage unit (memory or storage device or storage medium) not shown. Furthermore, the apparatus main body 30 may include a transmission unit 31. The description of these components in the first embodiment is also applied to the second embodiment.

  As in the first embodiment, each of these devices and each unit in the device main body 30 can be installed at a remote location. The apparatus main body 30 is composed of a plurality of such units, and is referred to as such for convenience. Similarly to the first embodiment, reception may be performed by mechanically scanning the reception transducer 20. In general, even when not called an array type, the same processing may be performed.

  However, unlike the apparatus according to the first embodiment, the apparatus according to the second embodiment comes from an arbitrary wave source, as will be described in detail below, in order to sense the timing at which the wave is generated. The control unit senses the timing signal generated by receiving the observed wave itself or generates a timing signal through another process, via wired or wireless communication, and receives the data of each receiving unit (each receiving channel). It may be used as a trigger signal for starting (AD conversion and writing to memory).

  As a method for the control unit to sense a timing signal that informs the timing at which the wave is generated, when the wave itself coming from the wave source is used as the timing signal, the receiving transducer (or receiving sensor) of the apparatus according to the present embodiment The reception signal itself received by the 20 reception aperture elements 20a is used, or a timing signal received by a dedicated reception apparatus that may be provided in the apparatus main body 30 is used.

  In this case, the reception aperture element 20a (may be all elements, but the element or the like at the end or the center position may be used sparsely in the physical aperture) or a dedicated reception device (at least a plurality of reception channels). For example, information on the signal strength, frequency, band, code, etc. of the received signal through various input means as described above is detected. However, it is set to the control unit 34 (built-in memory) or an analog determination circuit (in this case, neither software nor hardware is variable and some hardware is fixed). Alternatively, the detection of the timing at which the wave is generated is performed by detecting the signal received by the receiving aperture element 20a or the dedicated receiving device in the memory or the storage device (storage medium), the threshold value, the value, and the characteristic of the wave to be observed. It is based on collating with discriminating data such as databases.

  In the case of discriminating the received signal in an analog manner, the trigger signal for data acquisition is generated only when the received signal is discriminated by a dedicated analog circuit provided, and only when the received signal is determined to be an observation target. There are cases where the beam forming process is performed after being converted and stored in a memory or a storage device (storage medium).

  When the received signal is digitally determined, the received signal is continuously AD-converted in time and stored in a memory or a storage device (storage medium). ) At a predetermined time interval (set through the input device, etc.), the digital signal processing unit 33 reads the stored signal and makes a determination based on the comparison with the determination data, and determines that the signal is an observation target signal. Only in such a case, the beam forming process may be performed.

  Since the storage capacity of the memory and the storage device (storage medium) is limited, the wave signal to be observed was not observed within a predetermined time (such as set through the input device) when digitally discriminating. In this case, the memory address is initialized. Further, although it is not efficient in terms of energy saving, the wave signal may be discriminated using the discrimination data based on the image signal that has been subjected to beam forming at any time and the accuracy has been improved by the beam forming. The processing is the same when a normal wave for communication purposes is an observation target.

  In addition, the dedicated receiving device may be installed at another position away from the units of other devices, for example, near the wave source to be measured, or at a position where the timing signal reception environment is good. There is a case where a wave propagating at a higher speed than a wave received at the receiving aperture (wave which becomes a timing signal) is used, and the timing signal is transmitted to the control unit in the apparatus body via the dedicated receiving apparatus. . A dedicated line (wired or wireless) that may use a relay station may be used. In this case, using the timing signal as a trigger signal, reception of the received signal (AD conversion and storage in a memory, a storage device, or a storage medium) and beam forming are performed.

  In addition, after the apparatus of the present invention receives a wave, a timing signal at which the wave is generated may arrive. In other words, the propagation speed is slow or such a mechanism may be used, but as a result, such a case may occur. In order to cope with such a case, the reception signal is constantly taken in, the reception signal stored in the memory or the storage device (storage medium) is read back in time, and beam forming is performed. . In that case, the timing signal is added with additional information on the wave obtained by other observers and observation devices as additional information at the relay station, etc., and the timing signal with additional information added is transmitted for dedicated reception. Information including additional information is read by the device and may be used not only in the device of the present invention but also in other devices. The line used is not limited to a dedicated line, and a normal network may be used. A similar timing signal may be used even when a wave for normal communication purposes is an observation target. The additional information may be transmitted by a wave or signal other than the timing signal.

  In addition to the generation of the wave to be observed, a wave that propagates at a higher or lower speed than the wave received by the receiving aperture element before, during, or after the generation (wave that becomes a timing signal) is a wave source. The dedicated receiving device and the dedicated line may be similarly installed and used. In that case, information about the wave to be observed may be added to the wave that becomes the timing signal, and information about the wave obtained by another observer or observation device is added by the relay station and transmitted. In some cases, information including additional information is read by the dedicated receiving device and used by the device of the present invention or other devices. The line used is not limited to a dedicated line, and a normal network may be used. A similar timing signal may be used even when a wave for normal communication purposes is an observation target. The additional information may be transmitted by a wave or signal other than the timing signal.

  As these dedicated receiving devices, dedicated sensing devices capable of sensing timing signals or reading additional information are used, but any observer or any observation device (observation object to be observed) can be used. Any active-type or passive-type observation device related to a wave or similar observation device, etc., or any other signal that is a precursor to the generation of the wave, is generated simultaneously with the wave, or is generated after the wave is generated Any active or passive observation device or similar observation device relating to the above phenomenon or wave) is used. In an irregular manner, only the timing signal is received by the dedicated receiving device, and the reading of the additional information itself may be performed by the digital signal processing unit via the dedicated device or the control unit in the device body.

  Even when the active or passive device itself of the present invention is used as a sensing device, the additional information may be read by the digital signal processing unit 33 in the same manner. The timing signal may be generated by a sensing device provided. When you don't know when, where, when, when, where, when and where the wave is generated, increase the efficiency of data acquisition and beam forming process, save power, memory and storage This is important for saving (storage media). Data capture and beam forming are performed based on the clock signal of the control unit 34. If the wave source is digital, it is better to synchronize, and the apparatus may operate at a high clock frequency and a high sampling frequency based on digital reception of the wave to be observed. The same applies to the case where the timing signal is an analog signal. However, when the timing signal is a digital signal, synchronization may be obtained in the apparatus main body.

  The object of observation is the wave itself generated by a self-emanating wave source, the characteristics of the wave source (strength, what kind of source, etc.), position, time when the wave source was activated, etc. May be observed. Similarly to the case where the apparatus is an active type, the distribution of temperature (distribution), displacement, velocity, acceleration, strain, strain rate, or the like of the target may be obtained from the wave spectrum. In addition, the characteristics of the medium in the propagation process (propagation speed, physical properties related to waves, attenuation, scattering, transmission, reflection, refraction, etc., or their frequency dispersion) are observed, and the structure and composition of the observation target and medium May be revealed. For example, radioactive materials (such as isotopes in PET), materials with non-zero thermodynamic temperatures, seismic sources, neural activity, astronomical observation, weather, arrivals, moving objects, communication equipment including mobile communication equipment, physical Alternatively, an object that responds to chemical stimulation, an electric source, a magnetic source, a radiation source, or various energy sources are observed, and the observation target is not limited to these.

Multiple different types of wave receiving transducers and sensors may be used to integrate measurement results (Fusion) and data mining through multi-physics or multi-chemistry. Of course, they may be observed by a single transducer or sensor (e.g., in medical ultrasound imaging, strain and blood flow representing tissue deformation and related tissue properties are selectively Depending on the size of the physical quantity and physical property value, and the direction of the physical quantity, such as superimposing images with different colors on the echo image at the same time, imaging optical ultrasound of different markers in a wide band with different colors, etc. Display images with different colors, or image with different color densities). Multifaceted behavior of the whole subject (whole body in the case of humans) and local behavior for those that function based on multiple functions and many physical properties, or that affect the surroundings in different ways In addition, the behavior of the whole subject (whole body in the case of humans) and local behavior is also understood. For example, various neural controls (body temperature, blood flow, metabolism, etc.) performed in a short time or for a long time in an organism, effects (radiation) on a living organism for a short time or for a long time It can be used for the development of artificial organs and cultured tissues, their hybrids, drugs, or supplements that contribute to prolonging life and prolonging life, and monitoring their operations.
Japan and other developed countries face an aging society, so it is important to improve QOL and reduce medical costs. Cancer lesions such as human liver cancer, pancreatic cancer, kidney cancer, thyroid cancer, prostate cancer, breast cancer, etc. are increasing (more than 1.5 million in Japan, 1 in 2 people in the country suffering from 1 death) And uterine fibroids, brain disease (brain tumor and cerebral hemorrhage, cerebral infarction, more than 1.3 million people), ischemic heart disease (myocardial infarction and angina, more than 1.7 million people), arteriosclerosis / thrombosis (1 in 4 people) Causes of death), dyslipidemia (over 2,060,000), diabetes (etc., over 10 million) and other diseases of adult disease, focusing on the network of nerves, blood flow, and lymph in the linkage of these organs and diseases However, the present invention opens up an innovative integrated diagnostic imaging system and technique and clinical style (including screening) that can perform early non-invasive differential diagnosis with high accuracy, convenience, and low cost.
Many cancer metastases are metastasis to lymph nodes where lymph flow is concentrated (lymphatic metastasis), as well as metastasis to areas where blood flow is abundant, such as lung, liver, brain, and bone (hematogenous metastasis). . Currently, when lymphoma is first diagnosed as swollen or lump, its spread (stage) and general condition are diagnosed. Also, via the bloodstream, for example, pancreatic cancer is in the liver, peritoneum, etc., breast cancer is in the liver, lungs, brain, etc., stomach cancer is in the lungs, liver, kidney, pancreas, etc., lung cancer is in the liver, kidneys, brain, etc. Colon cancer is known to metastasize between organs in the liver, lungs, brain, and the like. Since metastatic cancer has the characteristics of primary cancer, it is important to identify the primary cancer for appropriate treatment. Of course, for example, it is also important to capture hepatitis, viral chronic hepatitis, cirrhosis, etc. (development mechanism itself) that cause it as in the case of primary hepatocellular carcinoma. In addition, there is a large amount of blood flow in the vegetative artery around advanced cancer tumors and in advanced cancer tumors, and if blood flow is low, there is a high possibility of prostate disease and uterine fibroids. Diabetes, hyperlipidemia, high blood sugar viscosity, 1.2 to 1.3 times the probability of developing cancer with or without a history of diabetes, and 3 times the risk of developing ischemic heart disease in the diabetic group. Dyslipidemia (20-50% of diabetes) and they promote arteriosclerosis, increase in blood flow due to temperature rise due to heating (perfusion), kidney adjusts the number of red blood cells (oxygen) and blood pressure The present invention for observing the pathology, nerve control, and hemodynamics of these various tissues simultaneously in real time with high accuracy is important. Regarding thrombus, it is also desirable to improve the observation accuracy of hemodynamics in the daily life of the postoperative and cardiac pacemaker user (welfare).
For example, under the above approach focusing on the network of nerves, blood flow, and lymph, specifically, MRI (nuclear magnetic resonance imaging), SQUID (superconducting quantum interference device), (light) ultrasound device, OCT (optical coherence tomography) New high-precision and simple real-time three-dimensional in vivo based on the three basic physics mathematical inverse problems of electromagnetics, mechanics and thermology (described in paragraph 0377). Using image diagnostic techniques, early integrated imaging techniques (related simultaneous observation and fusion imaging by simultaneous multiple observations of the same or multiple organs) can be performed, and cancer and brain / High-intensity focused ultrasound (HIFU), electromagnetically heated coagulation, chemotherapy, pharmaceutical therapy, various types of radiation therapy, etc. as minimally invasive treatments for heart disease Performed breakthrough fusion can be carried out early treatment of highly accurate and inexpensive early differential diagnosis and minimally invasive. Innovative clinical style that can perform heat treatment in the shortest time following short-term early diagnosis will be developed.
(1) <Electromagnetics-based> Imaging of current density vector and electrical properties using MRI and SQUID: Based on magnetic field measurement, imaging of 3D distribution of current density vector and electrical properties (conductivity and dielectric constant) Visualize the network (superimposed on MRI diffusion imaging). Inverse problem of Bio-Savart's law and differential inverse problem using observed current density vector. For example, perfusion (blood flow) control can be monitored in the fusion with HIFU heat treatment described in (6) below.
(2) <Mechanical base> Imaging of blood flow vector, blood pressure, and shear viscosity using MRI, (optical) ultrasound, and OCT: In MRI, based on distribution imaging of hydrogen, carbon, phosphorus, etc. In the case of acoustic echography and optical ultrasound (when differentiating between arteries and veins, or when using D-type glucose or L-type glucose that is specifically taken up by recently reported cancers as a contrast agent, In the case of LDL, HDL cholesterol, and neutral fat due to dyslipidemia as markers, the multi-dimensional Doppler method is used to image the three-dimensional flow velocity vector and the three-dimensional distribution of the strain rate tensor (normal Doppler and In contrast, it is possible to observe vectors in any direction just by pointing the sensor to the target), and based on the differential inverse problem from the observed flow velocity data, Imaging the three-dimensional distribution of shear viscosity and density. MRI is the intracerebral blood flow in the skull, ultrasonic echo is in the heart cavity and abdominal organs (liver, pancreas, kidney, prostate, uterus), and in the body surface tissue (breast, thyroid, eye, skin). Blood flow, optical ultrasound, and OCT are used to monitor blood flow in organs, eyes, and skin during body opening (observation of eyes related to diabetes). Finally, the blood flow network is observed. Diagnosis of ischemic heart disease (myocardial infarction and angina) focusing on dyslipidemia and blood glucose, brain disease (brain tumor, cerebral hemorrhage, cerebral infarction), arteriosclerosis, thrombus by quantifying blood pressure, heart pressure and viscosity. In the integrated imaging of (5), the soft tissue of (3) is simultaneously observed. Or the perfusion (blood flow) in the HIFU heat treatment of (6) is monitored.
(3) <Mechanical base> Imaging of dynamic dynamics and shear (viscosity) of soft tissues using MRI, (optical) ultrasound, and OCT: Ultrasonic echo method and optical ultrasound (focusing on soft tissue components 3D distribution of soft tissue and strain tensor using the same multidimensional Doppler method as in (2) in the case of broadband observation of irradiation light and optical ultrasound without contrast agent or marker) In addition, based on the observed displacement data, the body pressure (tissue pressure and intraocular pressure) and shear (viscosity) elasticity (hardness), density, force source (radiation pressure and HIFU) 3 In situ imaging of dimensional distribution. MRI for intracranial brain tissue and lymph network, ultrasound echo method for heart tissue (myocardium and valves) and abdominal organs (liver, pancreas, kidney, prostate, uterus), body surface tissue (breast, thyroid, eye, skin) , Lymph network, optical ultrasound and OCT diagnose the pathological condition (organizational condition) of organs, eyes, and skin during open body. In (5) integrated imaging, (2) blood flow is simultaneously observed. Alternatively, the effect of HIFU heat treatment (6) (degeneration such as tissue coagulation) is monitored.
(4) <Thermologic base> Imaging of soft tissue temperature and thermophysical properties using MRI, (optical) ultrasound, and OCT: Chemical monitoring of so-called MRI Larmor frequency to monitor metabolism and HIFU heating treatment in (6) In-situ observation of three-dimensional temperature distribution using temperature dependence of shear (viscosity) modulus using (3) in addition to observation using shift and temperature dependence of (optical) ultrasonic velocity and volume. Conducted practical observations that are robust to tissue displacement. Furthermore, based on the differential inverse problem, we image the three-dimensional distribution of thermophysical properties (thermal conductivity, heat capacity, thermal diffusivity), perfusion (the blood flow observation in (2) can be applied), and heat source (HIFU). (6) Applied to the heat treatment plan in the HIFU heat treatment.
(5) <Integrated imaging> Simultaneous multiple observation of multiple organs using (1) to (4): Focusing on the network of nerves, blood flow, and perfusion based on three-dimensional imaging of tissue physical properties of electromagnetism, mechanics and thermology Integrated imaging diagnosis that simultaneously observes multiple organs from multiple angles. Simple and short time diagnosis.
(6) <Integration of integrated imaging and treatment> HIFU heat treatment control (automatic treatment) using integrated imaging of (5): (2) blood flow data and ( 4) Use the temperature and thermophysical observation data and HIFU heat source database on the temperature distribution calculation simulator to predict the temperature distribution, and also use the monitoring data of the therapeutic effect (degeneration) by the shear (viscoelastic) imaging of (3) Using an updated automatic heating treatment plan, controlling the focus (heating) position, beam shape, beam intensity, irradiation time, and irradiation interval of the HIFU beam under phase aberration correction It is possible to improve the accuracy, reliability, and safety of treatment, and to treat organ cancers other than prostate cancer and uterine fibroids that are widely used without obstacles such as bones and can be installed nearby.
The treatment means is desirably minimally invasive, and is not limited thereto as described above. The present invention is a simple, inexpensive and high QOL technique for aging societies, which has led to widespread use of medical examinations that lead to prevention and early detection, and also implements short-term treatment measures (ideally at the same time) It is a promising candidate for possible technology (Theranosis). The above imaging and treatment can be performed from the surface of the body, during surgery (directly applied to the organ during opening or through the organ) or during laparoscopic surgery, orally, through the nares, through the portal, and through the vagina. Can also be implemented.
Moreover, it includes a case where a substitute for various sensors possessed by living organisms, a supplement to them, or a case where a new sensor is provided. When living organisms are targeted, there may be a need for a compact and wearable form or material that is easy to adapt to living organisms. Processing contents are also various.For example, when multiple compression waves and shear waves arrive as dynamic waves at the same time, an analog dedicated device is used using the mode, frequency, band, code, propagation direction, etc. Alternatively, beam forming may be performed after separating the waves using the digital signal processing unit as in the first embodiment. When there are a plurality of electromagnetic wave sources, a plurality of electromagnetic waves having different characteristics may be superimposed and may be separated in the same manner. Alternatively, a high-precision image signal may be generated even when a plurality of waves arrives due to the phasing addition effect by beam forming (for example, when the medium is a scattering medium).

  Of course, after beam forming is performed, signals may be separated based on the same processing. In order to obtain the effect of phasing addition, it is necessary to determine the arrival direction of the wave and the position of the wave source, and steering in that direction or focusing to the position may be performed. In reception, in addition to dynamic focusing, fixed focusing is also useful. In order to obtain them, the center-of-gravity (center) frequency, instantaneous frequency, band, so-called MIMO, SIMO, MUSIC, independent component analysis, code, various parametric methods, etc. of the wave received by the receiving aperture element array May be used. The same processing may be performed after performing beam forming, but in addition, waves may be observed using geometric information, particularly after performing beam forming at a plurality of positions. . The processing method is not limited to these, and may be implemented under an inverse problem approach, for example.

  For example, the propagation direction of an incoming wave is obtained based on multidimensional spectral analysis of a received signal (the past achievements of the inventor of the present application), and in the apparatus of the present invention, a plurality of transducers provided at different positions Or, when information about the propagation time is not obtained using the reception effective aperture (normally, the position and distance of the wave source are calculated from the time when the wave is observed at a plurality of positions), the geometrical It is possible to determine the position and distance. Waves can be observed with continuous waves instead of pulse waves and burst waves. Through any processing, when the direction of arrival of the wave is known, the received beam can be steered and focused in that direction (monostatic or multistatic aperture synthesis) and observed in detail. If necessary, transmission beam forming may also be performed in the active type of the first embodiment. In those processes, receive beamforming is always performed while changing the steering angle, focusing on the likely direction, and the resulting image or imaging, spatial resolution, contrast, signal strength, etc. are observed, or The direction of the wave source can also be specified through multidimensional spectral analysis. It may be automatically controlled.

  The resolution of the image signal may be increased by super-resolution. There are also descriptions in paragraphs 0009 and 0425. It may be easy to measure the wave source, the object to be measured, scattering in the medium, the size, intensity, position, etc. of the reflector. The band is always limited by the physically generated wave field, but typical super-resolution is to broaden this by inverse filtering and restore them as the original signal source or signal. is there. In addition, the wave is usually affected by frequency-dependent attenuation, may not be in focus, the wave source may be a moving object, and the intervening medium may be disturbed. . Super-resolution may be performed to correct these. As described in paragraph 0383, it may be useful to perform further filtering to have the desired point spread function, not just a broad band, and in various super-resolutions, the filtering can be combined with inverse filtering and frequency Implementing in the region or spatio-temporal region is one of the features of the present invention.

  In addition, the measurement target or the like may move during transmission and / or reception necessary for generating one image signal, and it may be necessary to perform motion compensation. In many cases, the point spread function is unknown, and in this case, blind deconvolution may be performed including the case where the above signal separation processing (particularly, blind separation) is used in combination. The method described in paragraph 0425 is known. In addition, there are various other methods such as a maximum likelihood method (for example, non-patent documents 39-41). It is desirable to evaluate the point spread function by some method, such as obtaining an autocorrelation function, and ideally to obtain a coherent point spread function. However, inverse filtering is possible even if it is obtained. Even in such a case, it is useful to perform filtering together so as to have a desired point spread function.

  If the point spread function cannot be obtained when the observation is desired, for example, the point spread function may be evaluated and stored as a database when the observation is possible. One effective method of performing inverse filtering is to weight the observed spectrum so that it is the same as the desired spectral distribution of the signal distribution such as the point spread function or echo distribution (of course, the spectral intensity distribution). Is possible. The desired spectral distribution of signal distribution such as point spread function and echo distribution may be set through analysis, simulation, optimization, etc., and beam forming is performed under ideal parameters for the measurement target. , It can be done once, ensemble averaging can be done under multiple measurements, or it can be averaged under local steady-state assumptions ( For example, Non-Patent Documents 35 and 36), which have been used for a long time, may be obtained in the same manner using a phantom (calibration phantom) of a measurement object. Estimating a one-dimensional point spread function in the direction of wave propagation or in a direction perpendicular thereto by obtaining a one-dimensional autocorrelation function, or estimating a multidimensional point spread function by obtaining a multidimensional autocorrelation function (Non-Patent Documents 8 and 14). Each is equivalent to a one-dimensional spectrum or a multi-dimensional spectrum in the propagation direction or orthogonal direction (ie, self-spectrum). These are used when evaluating the wavelength of the wave, the shape of the force source, and the spatial resolution of the wave (Patent Document 11 etc.), and are used for super-resolution. For example, a fixed wave or aperture synthesis (Non-Patent Document 15) is performed using a power function apodization to obtain a desired signal distribution such as a point spread function or an echo distribution, and a plane wave capable of high-speed transmission / reception A low resolution signal (Non-patent Document 15) obtained by performing transmission using Gaussian apodization may be increased in resolution. The latter is suitable for high-speed measurement of high-speed movement and shear wave propagation, and can simultaneously realize the measurement and high-resolution ultrasonic imaging. Alternatively, inversion can be performed using the power spectrum of the signal itself. These processes can be applied to the angular spectrum before wave number matching or the spectrum after wave number matching. That is, super-resolution can be performed using a desired point spread function, an angular spectrum or spectrum of a signal distribution such as an echo distribution, or an angular spectrum or spectrum of a received signal. In weighting, care must be taken when dividing by a zero value or a small spectrum.In particular, it is not effective to amplify various types of noise contained in the received signal. ), Wiener filter (suppresses amplification of frequency components with low signal-to-noise ratio), singular value decomposition (throws out small singular values and spectrum and does not use signal components of corresponding frequency), Likelihood estimation (with or without MAP) is effective.

  It is possible to perform inverse filtering also in the process of the methods (1) to (7) in the digital wave signal processing. The resolution of the image signal is increased, and an effect may be obtained in terms of quantitativeness (numerical value), but the same effect may be obtained when displayed as an image. An effect of restoring a blurred image or focusing can be obtained. Inverse filtering may be performed on an incoherent signal, or it is effective when performed in the state of a coherent signal, and in particular, a spatial change in a physical property distribution may be understood. In some cases, super-resolution is performed on a superimposed image or a spectrum whose frequency is divided. The application of super-resolution is not limited to these.

  A new super-resolution can also be implemented. One is based on non-linear processing described later, and the other is to image the instantaneous phase described here.

Now, the signal of the position coordinate s in the propagation direction (coordinate axis t) in the region of interest obtained using a single wave or beam
T = 0 represents the reference position in the t-axis direction, that is, the position of the wave source (t = 0), and δθ (t) represents a phase change caused by reflection or scattering at the position coordinate t.
Then, from this, the instantaneous angular frequency ω (t) in the propagation direction t, the instantaneous phase θ (t), and the like are obtained and imaged. The propagation direction t may be directed to the front without steering, may be steered and have a deflection angle, and is two-dimensional or one-dimensional when the region of interest is three-dimensional. Sometimes. As described in Non-Patent Document 19, the propagation direction of a wave or beam can be measured with spatial resolution (using the center of gravity and instantaneous frequency of the spectrum), and at the same time, the frequency in that direction can be measured. The frequency in the direction of the integration path (tangential direction) set in the spatial integration process can be obtained and calculated with high accuracy. For example, the integration path is linear in the steering direction (angle) of the wave or beam set at the time of transmission or in the generated wave or beam in the same manner, but in a globally estimated steering direction (angle). Can take. In order to simplify the processing, the nominal frequency and the frequency in the direction estimated globally can also be used. Performing integration in the propagation direction estimated with spatial resolution involves frequency distribution interpolation processing, which is not impossible but not practical.

Incidentally, A (s) is the amplitude and represents the reflection intensity and the scattering intensity at the position coordinate t = s. For example, it is obtained by envelope detection (square root of the sum of the squares of the IQ signal) through orthogonal detection of Equation (30-1). Or, through the Hilbert transform using the Fourier transform,
And is also obtained by the square root of the sum of the squares of Equation (30-1) and Equation (31) (Patent Literature 7 and Non-Patent Literature 14). The latter is particularly suitable for digital signal processing.

Using the expression (30) and the expression (31), a complex analysis signal (Patent Document 6 or Non-Patent Document 7) is displayed,
It can be expressed.

In order to obtain the instantaneous phase θ (s), first, the instantaneous angular frequency is obtained. As a conventional means, it is assumed that the instantaneous frequency at the next sampling position coordinate t = s + Δs is equal and the instantaneous phase is not equal at the position coordinate t = s in the methods described in Patent Document 6 and Non-Patent Document 7 ( δθ (t) is a phase change (that is, random) determined by random scattering intensity and reflectivity (that is, randomly changes greatly with respect to t)),
Assuming that the signal at its position coordinate t = s + Δs is
When the conjugate product of Expression (32) and Expression (35) is obtained, under the assumptions of Expression (33) and Expression (34),
Therefore, the instantaneous frequency at the position coordinate t = s is
It is estimated to be.

As described in Patent Document 6 and Non-Patent Document 7, in practice, noise is mixed in the signal r (s), and estimation is performed under the assumptions of Expression (33) and Expression (34). In some cases, the moving average process is performed in the s-axis direction or in two directions or one direction orthogonal to the s-axis direction to improve the accuracy. When this moving average process is performed on the equation (36) and obtained according to the equation (37)
And when applied to equation (37) itself
However, it has been confirmed that the accuracy of the equation (38-1) is higher in displacement (vector) measurement.

It is only necessary to detect the instantaneous frequency at each coordinate using the instantaneous frequency subjected to the moving average. The instantaneous frequency estimate is unbiased, and in the case of digital signal processing,
By assuming that the instantaneous phase θ (s) is an integrated value of phase change (ie, random) determined by random scattering intensity and reflectance.
Is obtained.

  Note that the center of gravity obtained from the first moment of the spectrum (the center of gravity, that is, the weighted average value) is used instead of the moving average of the instantaneous frequency obtained by the equations (38-1) and (38-2). A frequency (× 2π) may be used. The equation is shown in equation (S1).

  T = 0 in the expression representing the observed signal represents a reference position in the t-axis direction, that is, a wave source position. On the other hand, the reference position t = t ′ in the equation (39) may also be set to t ′ = 0 (wave source position), and in this case, θ ′ (s) obtained as a distribution of position coordinates t = s. Is an estimated value of the instantaneous phase (Expression (30-2)) itself represented by an integral value of the phase change caused by reflection or scattering. The instantaneous frequency is averaged, and θ ′ (s) obtained is an estimated value obtained in the situation.

Also, the instantaneous frequency is obtained from the wave source position (t = 0) to t = s ′ (non-zero, not equal to s) due to the influence of the moving average process and the influence of the window length when obtaining the spectrum. If not, t ′ = 0 and using the nominal angular frequency or the previously measured / estimated angular frequency ω ₀ ,
Equation (39) is used as Alternatively, Equation (39) may be used as t ′ = s ′ (non-zero, but not equal to s). In this case, the estimated bias value θ ′ (s) includes the following bias error: Will occur.

However, when estimating Δθ (s), which is the change amount of the instantaneous phase at the sampling Δs interval, based on the equations (30-2) and (34), the bias does not pose a problem. The estimation result is
It is obtained as A conjugate product with a complex exponential function having ω (s) Δs as a core may be obtained for Expression (36). In the above equations (34), (36), (43), etc., the case where the subtraction of the phase is obtained using the forward difference is described, but instead, the backward difference can be performed. Further, in the equations (37), (38-1), and (38-2), the calculation of the phase differentiation is performed by approximation by dividing the above-described phase difference by the sampling interval, but it has a high cutoff frequency. Differentiation processing may be performed using a differentiation filter. For integration of the estimated value of the instantaneous frequency in the equation (39), various known integration operations including a trapezoidal rule can be performed.
In addition, in order to obtain the estimation result of the instantaneous phase (Expression (30-2)) not including the phase rotation expressed by Expression (40), the imaginary number of the analysis signal expressed by Expression (32) without depending on the above. Arctan (inverse function of tangent) is applied to the part / real part to obtain the cosine angle (ie, instantaneous phase including phase rotation) in equation (30-1), and s ′ = s in equation (42) It is also possible to directly subtract using a moving average of the instantaneous frequency or a phase rotation obtained by integrating the first moment of the spectrum. However, since the direct calculation result of arctan is a result of −π to π, it is necessary to perform a subtraction process after unwrapping the result. Since the instantaneous phase including phase rotation is monotonically increasing, the unwrapping may be obtained by adding 2π multiplied by an integer m when the arctan result is negative. Here, m is the number of times that the arctan result observed in the beam direction or wave propagation direction becomes negative. Similar to the above case, the equation (41) may be used, or a bias error represented by the equation (42) may be generated. Further, in order to estimate Δθ (s), which is the amount of change in instantaneous phase of sampling interval Δs that does not include a bias error, phase rotation estimated at positions separated by Δs is not included, apart from equation (43). The difference from the instantaneous phase estimate can also be calculated directly by subtraction.
The image related to the phase expressed using the equation (40) or the equation (43) has a wide band and is a kind of super-resolution. These phases themselves can be displayed, can be displayed by being multiplied by a cosine or a sine function, and can also be displayed by being weighted with an envelope. Incidentally, the square root of the sum of the squares of the real part and the imaginary part of the complex analysis signal for which the phase of Equation (40) is obtained is the same as that of the envelope signal. Therefore, it is better to image the square wave detection, the absolute value detection, and ideally, without damaging the wave (the sign and phase of the signal value) (can be displayed as a gray image or a color image). The image mainly represents the signal intensity, phase, and phase change determined by reflection and scattering. On the other hand, when the obtained instantaneous frequency is imaged, an image representing the influence of frequency modulation due to attenuation or scattering is obtained (similarly, gray and color can be displayed).

In addition, although it described that said Hilbert transformation was performed based on (fast) Fourier transformation (nonpatent literature 13), of course, you may calculate the original Hilbert transformation. In addition, the accuracy decreases when noise is mixed in the signal, but the differential processing is performed on the target real-time signal to generate a signal whose phase is advanced by 90 °, and multiplied by −1 to obtain an imaginary number. It is also possible to calculate the component (the angular frequency multiplied by the differentiation process is obtained by calculating the phase obtained by applying the inverse function of the cosine or sine signal to the original real time signal at the neighboring position (phase ) And the difference (so-called forward difference, backward difference, center difference, etc., multiplied by 1 and -1 and added or subtracted) and corrected by the distance of those positions (difference approximation) It may be sufficient to use differential filtering instead of differential approximation).
For example, when differential processing is performed on an arbitrary signal represented by Expression (30-1), the spatial differentiation (change in space (s)) of the amplitude A (s) is compared with the instantaneous frequency ω (s). In the case where the value is small or the assumption thereof is made, and regarding the result of the expression (30-1) or the derivative thereof, in the multi-dimension including the partial differential direction or by applying the moving average to the partial differential direction, To approximate.
In some cases, the moving average processing is not performed on the signals themselves. In addition to the above calculation, ω (s) can be estimated as follows, for example. The equation (30-1 ′) is further differentiated, and under the above conditions, assumptions, and processing, and further, the case where the spatial differentiation of ω (s) is also small or the assumption thereof is made and approximated as follows.
At that time, the moving average processing may not be performed on the signals themselves. If equation (30-1 ″) is divided by equation (30-1) and multiplied by −1, ω ² (s) can be estimated. However, the estimation result of ω ² (s) may be a negative value, and it may be replaced with a positive value in the vicinity of the partial differential direction s in multiple dimensions including the partial differential direction s. Interpolation approximation using only values, median filtering, moving average processing, or a combination of these may be performed. The median filter is particularly effective in removing a large estimation error that occurs suddenly. Further, median filtering or moving average processing may be performed on ω (s) obtained by applying a square root to a positive value. Through these processes, ω (s) may be obtained. By dividing the equation (30-1 ′) by ω (s) and multiplying by −1, the imaginary component of the analytic signal of the equation (30-1) is obtained (that is, the analytic signal is obtained). This second order differentiation may be obtained by applying a differential filter or differential approximation twice to equation (30-1), or using a second order differential filter or second order differential approximation (using a so-called central difference, -2, multiplied by 1 and added, and divided by the square of the distance between those positions). In addition, for differentiation, for example, a differential filter using an operational amplifier in an analog circuit may be used, or differential calculation based on a differential filter or differential approximation may be performed in a digital circuit or digital signal processing. Since these differentiation processes are a kind of high-pass filtering, they may be processed with a high cut-off frequency, or a moving average process may be performed on the result of the differentiation process. Further, in order to simplify the calculation, instead of the instantaneous frequency ω (s), a nominal frequency or a globally estimated frequency (such as a first moment of spectrum) can be used instead. This detection process is much faster than other detection processes. This process can also be used for envelope imaging of r (s) (the magnitude of the analysis signal can be obtained) and measurement of displacement, velocity, acceleration, strain, distortion, temperature, and the like. The displacement measurement accuracy is substantially the same as when (high speed) Fourier transform is performed, but the echo image is experienced to be higher in intensity than in the deep part. This Hilbert transform method is faster than the Hilbert transform using Fourier transform (Non-patent Document 13), and a plurality of beams and waves having different wave parameters and beam forming parameters are generated in each time phase. In this case, the number of reception signals received by the reception transducer increases and the number of times beamforming and Hilbert conversion are performed increases, which is effective in such a case. The Hilbert transform may be performed at one time by regarding a superposition of a plurality of beamformed signals as one beamformed signal, and in this case also, the effective frequency (the instantaneous frequency obtained by differentiation is This is the combined frequency in the differential direction of the superposition of those beams and waves). The instantaneous phase imaging described above may also be performed on the superimposed composite wave as well. When performing these measurements, multiple Doppler equations derived from each of them are used by using multiple waves and beams, or using multiple pseudo waves and beams obtained through frequency division of the spectrum. System equations may be obtained (which may be an over-determined system), in which case equation (30-1) represents their respective wave or beam or pseudo wave or beam. Each analysis signal is similarly determined and used. In addition, even when the received signal is a multidimensional received signal and the carrier frequency exists in a plurality of orthogonal coordinate axis directions (when lateral modulation or steering is performed), the instantaneous phase can be similarly estimated (details will be described later). To do).

FIG. 35 is a diagram showing an example of two steering beams in a two-dimensional case and lateral modulation of their superposition. FIG. 36 is a diagram illustrating an example of four steering beams in a three-dimensional case and lateral modulation of their superposition (in the case of three steering beams, one of the steering beams shown in FIG. 36). 3 steering beams can be used, or three steering beams that are all symmetrical with respect to the axis may be generated (the figure is omitted). 35 and 36 show linear one-dimensional and two-dimensional array apertures, but other arbitrary-shaped array apertures can be used, and the coordinate system can be any rectangular coordinate. You can use the system. Regardless of which array aperture type or Cartesian coordinate system is used, a steering beam that is symmetrical with respect to a plane that spatially delimits the four quadrants with an axis or an axis that intersects the axis is used (not symmetric). (In some cases, the coordinate system may be translated or rotated to make it symmetrical). Here, although referred to as a steering beam, the present invention can be applied to any wave that is steered (something that is not steered may be included). In the case of lateral modulation, for example, in the case of two dimensions, as shown in FIG. 35, two cross waves generated by steering are processed in a state where they are not superimposed and a state where they are superimposed. Similarly, in the case of the three-dimensional case, as shown in FIG. 36, the three or four cross waves generated by the steering are processed in a state where they are not overlapped with each other. The same applies to the case where the steering is performed and processed as a multidimensional received signal. As described in Non-Patent Document 19, the propagation direction of a wave or beam can be measured with spatial resolution (using the center of gravity and instantaneous frequency of the spectrum), and at the same time, the frequency in that direction can be measured. The frequency in the direction of the integration path (tangential direction) set in the spatial integration process can be obtained and calculated with high accuracy. In the case of the above-described one-dimensional signal, as an example, the integration path is similarly estimated in the steering direction (angle) of the wave or beam set at the time of transmission, or in the generated wave or beam. In this multi-dimensional case, the integration path can theoretically be arbitrarily taken in the dimensional space. However, in the actual calculation of integration, it is important to set the integration path in a state suitable for the coordinate system in which beam forming has been performed, such as those that draw straight lines or arcs, or those that connect them. Often used. In addition, in order to simplify the processing, it is possible to use a nominal frequency or a frequency estimated globally at the same time (projected on an integration path). Performing integration in the propagation direction estimated with spatial resolution involves frequency distribution interpolation processing, which is not impossible but not practical. Now, the signal in the region of interest
Then, the instantaneous angular frequency (ω ₁ (t ₁ , t ₂ , t ₃ ), ω ₂ (t ₁ , t ₂ , t ₃ ), ω in each direction (t ₁ , t ₂ , t ₃ ) ₃ (t ₁ , t ₂ , t ₃ )) and the instantaneous phase θ (t ₁ , t ₂ , t ₃ ) and the like are imaged. When the region of interest is 2D,
It is expressed. The same processing as in the following three-dimensional case is performed.

Incidentally, A (s ₁ , s ₂ , s ₃ ) is an amplitude, and represents the reflection intensity and the scattering intensity at the position coordinates (s ₁ , s ₂ , s ₃ ). For example, it is obtained by envelope detection (square root of the sum of the squares of the IQ signal) through orthogonal detection of Equation (30′-1). Or, through the Hilbert transform using the Fourier transform,
And is also obtained from the square root of the sum of the squares of Expression (30′-1) and Expression (31 ′) (Patent Document 7 and Non-Patent Document 14). The latter is particularly suitable for digital signal processing.

Using the expression (30 ′) and the expression (31 ′), a complex analysis signal (Patent Document 6 or Non-Patent Document 7) is displayed.
It can be expressed.

In order to obtain the instantaneous phase θ (s ₁ , s ₂ , s ₃ ), first, the instantaneous angular frequency is obtained. The usual practice, the method described in Patent Document 6 and Non-Patent Document 7, in the position coordinates _{(s 1, s 2, s} 3), for example, t ₁ the direction of the next sampling position coordinates (s ₁ + Δs _1, Assuming that the instantaneous frequencies in s ₂ , s ₃ ) are equal and the instantaneous phases are not equal (δθ (t ₁ , t ₂ , t ₃ ) is a phase change determined by random scattering intensity and reflectance (ie, random ) And (t ₁ , t ₂ , t ₃ ) vary greatly and randomly)
Assuming that the signal at its position coordinates (s ₁ + Δs ₁ , s ₂ , s ₃ ) is
When the conjugate product of the equation (32 ′) and the equation (35 ′) is obtained, under the assumption of the equation (33 ′) and the equation (34 ′),
It is expressed as, Accordingly, the position coordinates _{(s 1, s 2, s} 3) s 1 direction instantaneous frequency omega ₁ in _{(s 1, s 2, s} 3) are
It is estimated to be.

As described in Patent Document 6 and Non-Patent Document 7, in practice, noise is mixed in the signal r (s ₁ , s ₂ , s ₃ ), and Expressions (33 ′) and (34 ′) As a presumption under the above assumption, a moving average process may be performed including the s ₁ axis direction and two or one direction orthogonal to the s ₁ axis direction to increase the accuracy. When this moving average process is performed on the equation (36 ′) and obtained according to the equation (37 ′)
And when applied to ω ₁ (s ₁ , s ₂ , s ₃ ) itself
However, it has been confirmed that the accuracy of the equation (38′-1) is higher in displacement (vector) measurement. The instantaneous frequency in the direction of s ₂ and s ₃ can be obtained in the same manner by obtaining R ₂ (s ₁ , s ₂ , s ₃ ) and R ₃ (s ₁ , s ₂ , s ₃ ).

It is only necessary to detect the instantaneous frequency at each coordinate using the instantaneous frequency subjected to the moving average. The instantaneous frequency estimate is unbiased, and in the case of digital signal processing, for equation (32 ′)
By assuming that the instantaneous phase θ (s ₁ , s ₂ , s ₃ ) is an integrated value (ie random) of phase changes determined by random scattering intensity and reflectance.
Is obtained.

  In addition, instead of using the moving average on the instantaneous frequency obtained by the equations (38′-1) and (38′-2), the first moment of the spectrum (center of gravity, that is, the weighted average value) is used. The obtained center-of-gravity frequency (× 2π) may be used. The equation of the center of gravity in the x-axis direction of one axis of the three-dimensional orthogonal coordinate system is shown in the equation (S1 ″). The other directions are obtained in the same manner, and are obtained in two dimensions.

The integration path c in the expression representing the observed signal is an arbitrary line from the start point 0 to the point of interest (s ₁ , s ₂ , s ₃ ) where the position where the instantaneous phase is zero is considered as the reference position. 0 represents the position of the wave source. On the other hand, the starting point of the integration path c ′ in the equation (39 ′) may also be 0 (wave source position), in which case the position coordinates (t ₁ , t ₂ , t ₃ ) = (s ₁ , s _2, s ₃ obtained theta 'as _{distribution) (s 1, s 2,} s 3) is the instantaneous phase represented by the integral value of the phase change caused by reflection or scattering (formula (30'-2)) itself Is an estimated value. The instantaneous frequency is averaged, and θ ′ (s ₁ , s ₂ , s ₃ ) obtained is an estimated value obtained in that situation.

In addition, due to the influence of the moving average processing and the influence of the window length when obtaining the spectrum, the instantaneous frequency changes from the wave source position 0 to (t ₁ , t ₂ , t ₃ ) = (s ₁ ′, s ₂ ′, s ₃ ′ ) (Not the wave source position and not equal to (s ₁ , s ₂ , s ₃ )), the starting point of the integration path c ′ is set to 0 and the nominal angular frequency or previously measured / estimated Using the angular frequency (ω ₀₁ , ω ₀₂ , ω ₀₃ ) in each direction,
Equation (39 ′) is used as Alternatively, the starting point of the integration path c ′ is (t ₁ , t ₂ , t ₃ ) = (s ₁ ′, s ₂ ′, s ₃ ′) (not the wave source position 0 but (s ₁ , s ₂ , s ₃ (39 ′) may be used, and in this case, the following bias error occurs in the estimated value θ ′ (s ₁ , s ₂ , s ₃ ).

However, for example, Δθ ₁ (s ₁ , s ₂ , s ₃ ), which is the amount of change in the instantaneous phase in the t ₁ axis direction at sampling Δs ₁ intervals, is calculated based on equations (30′-2) and (34 ′). When estimating, the bias does not matter. The estimation result is
It is obtained as A conjugate product with a complex exponential function having ω ₁ (s ₁ , s ₂ , s ₃ ) Δs ₁ as a core may be obtained for the equation (36 ′). In addition, the estimated value Δθ ₂ ′ (s ₁ , s ₂ , s ₃ ) Δθ ₃ ′ (s ₁ , s ₂ , s ₃ ) of the phase change in the direction of t ₂ or t ₃ is also the sampling interval Δs _{2 in} each direction. Δs ₃ can be obtained. In the above formulas (34 ′), (36 ′), (43 ′), etc., the case where the phase subtraction is obtained using the forward difference is described, but instead, the backward difference can be performed. is there. Further, in the equations (37 ′), (38′-1), and (38′-2), the phase differentiation is calculated by approximation by dividing the phase difference by the sampling interval. Differentiation may be performed using a differential filter having a frequency. For integration of the estimated value of the instantaneous frequency in the equation (39 ′), various well-known integration operations including a trapezoidal rule can be performed. In order to obtain the estimation result of the instantaneous phase (formula (30′-2)) not including the phase rotation represented by formula (40 ′), the analysis represented by formula (32 ′) is not dependent on the above. Arctan (inverse function of tangent) is applied to the imaginary part / real part of the signal to obtain the cosine kernel (ie, instantaneous phase including phase rotation) in equation (30′-1), and in equation (42 ′) (s ₁ ′, s ₂ ′, s ₃ ′) = (s ₁ , s ₂ , s ₃ ), directly using the moving average of the instantaneous frequency or the phase rotation obtained by the integral operation of the first moment of the spectrum You can also subtract. However, since the direct calculation result of arctan is a result of −π to π, it is necessary to perform a subtraction process after unwrapping the result. Since the instantaneous phase including phase rotation is monotonically increasing, the unwrapping may be obtained by adding 2π multiplied by an integer m when the arctan result is negative. Here, m is the number of times that the arctan result observed in the beam direction or wave propagation direction becomes negative. Similar to the above case, the equation (41 ′) may be used, or a bias error represented by the equation (42 ′) may be generated. In addition, in order to estimate Δθ ₁ (s ₁ , s ₂ , s ₃ ) that does not include a bias error and is an amount of change in the instantaneous phase of the sampling interval Δs _{1 in} the t ₁ direction, The difference from the estimated value of the instantaneous phase not including the phase rotation estimated at the position separated by Δs _{1 in the} t ₁ direction can also be calculated directly. Similarly, the estimated value Δθ ₂ ′ (s ₁ , s ₂ , s ₃ ) Δθ ₃ ′ (s ₁ , s ₂ ) of the amount of change in instantaneous phase at sampling intervals Δs ₂ and Δs ₃ in the direction of t ₂ and t ₃ , s ₃ ) can also be obtained.
The image related to the phase expressed using the equation (40 ′) or the equation (43 ′) has a wide band and is a kind of super-resolution. These phases themselves can be displayed, can be displayed by being multiplied by a cosine or a sine function, and can also be displayed by being weighted with an envelope. Incidentally, the square root of the sum of the squares of the real part and the imaginary part of the complex analytic signal for which the phase of the equation (40 ′) is obtained is the same as that of the envelope signal. Therefore, it is better to image the square wave detection, the absolute value detection, and ideally, without damaging the wave (the sign and phase of the signal value) (can be displayed as a gray image or a color image).

The Hilbert transform described above is performed based on a multidimensional (fast) Fourier transform (Non-patent Document 13, in a state where cross beams and cross waves are separated without overlapping even if they overlap in space. However, as will be confirmed later, the former processing can Fourier-transform all received signals at one time and requires less computation, and the separated signals are processed after being actively superimposed. Of course, the calculation of the original Hilbert transform may be applied as in the case of one-dimensional.
Also, the accuracy decreases when noise is mixed in the signal, but as with the one-dimensional case, the target real-time signal is differentiated to generate a signal whose phase is advanced by 90 °. The imaginary component can also be calculated by multiplying by -1 (the amount obtained by multiplying the angular frequency by the differentiation process is the neighborhood obtained by applying the inverse function of the cosine or sine signal to the original real-time signal. It is sufficient to calculate the difference (so-called forward difference, backward difference, center difference, etc.) from the calculation result (phase) at the position of, and divide by the distance of those positions (difference approximation). And a differential filter may be applied). However, the method described in this paragraph is limited to the case where the steered waves are not superimposed as shown in FIGS. 35 and 36 when the lateral modulation is performed. It is also possible to process a single steered wave independently (this paragraph). One processing method in the case of overlapping is described at the end of this paragraph, and the other two processing methods are described in the following paragraphs.
For example, when partial differential processing is performed on an arbitrary signal represented by the equation (30′-1) or the like, partial differentiation is performed on one direction from s ₁ to s ₃ . The spatial partial differentiation (spatial change) of the amplitude A (s ₁ , s ₂ , s ₃ ) is the instantaneous frequency ω ₁ (s ₁ , s ₂ , s ₃ ) or ω ₂ (s ₁ , s ₂ , s ₃ ), ω ₃ (s ₁ , s ₂ , s ₃ ) and the case where it is smaller or its assumption, and the partial differential direction is expressed in relation to the expression (30′-1) or the partial differential result thereof. It approximates as follows by performing a moving average in the multi-dimensionality to include or the partial differential direction. For example, when the partial differentiation in s ₁ direction is as follows.
In some cases, the moving average processing is not performed on the signals themselves. For example, in the case of lateral modulation, the instantaneous frequency in that direction may be lower than the instantaneous frequency in other directions depending on the direction. In such a case, the direction of partial differentiation is taken in that direction. However, if the direction is a steered direction, the sampling interval of the signal may be coarse, and care must be taken when performing the approximate calculation. In addition to the above calculation, ω ₁ (s ₁ , s ₂ , s ₃ ) can be estimated as follows, for example. If the equation (30′-1 ′) is further partially differentiated in the same direction, and the spatial differentiation of ω ₁ (s ₁ , s ₂ , s ₃ ) is small under the above conditions, assumptions, and processing, or Make assumptions and approximate as follows.
At that time, the moving average processing may not be performed on the signals themselves. If equation (30′-1 ″) is divided by equation (30′-1) and multiplied by −1, ω ₁ ² (s ₁ , s ₂ , s ₃ ) can be estimated. However, the estimation result of ω ₁ ² (s ₁ , s ₂ , s ₃ ) may be negative, and in multiple dimensions including the partial differential direction or a positive value near the partial differential direction s ₁ , Interpolation approximation using only positive values in the vicinity, median filtering, moving average processing, or a combination of these. The median filter is particularly effective in removing a large estimation error that occurs suddenly. Further, median filter or moving average processing may be applied to ω ₁ (s ₁ , s ₂ , s ₃ ) obtained by applying the square root to the positive value. Through these processes, ω ₁ (s ₁ , s ₂ , s ₃ ) may be obtained. By dividing the equation (30′-1 ′) by ω ₁ (s ₁ , s ₂ , s ₃ ) and multiplying by −1, the imaginary component of the analytic signal of the equation (30′-1) is obtained (that is, Analytical signal is obtained). This second-order differentiation may be obtained by applying a differential filter or difference approximation twice to the equation (30′-1), or by obtaining a second-order differential filter or second-order difference approximation (so-called center difference). May be. Similarly, when partial differentiation is performed in each direction of s ₂ and s ₃ other than s ₁ , ω ₂ (s ₁ , s ₂ , s ₃ ) and ω ₃ (s ₁ , s ₂ , s ₃ ) The analysis signal is obtained, but as described above, it is desirable to appropriately select the direction of partial differentiation. For example, in a two-dimensional case, when a steering beam having a steering angle of ± 20 ° is used, there is no significant difference between the case where the direction of partial differential processing is set to the depth direction and the case where it is set to the horizontal direction. Although the case has been experienced, in comparison with the Hilbert transform through the multidimensional (fast) Fourier transform (Non-patent Document 13), the echo intensity in the deep part is strongly obtained in comparison with the use of this approximation process. Sometimes. On the other hand, even in such a case, we have experienced that the accuracy of displacement vector measurement is almost the same. In addition, for differentiation, for example, a differential filter using an operational amplifier in an analog circuit may be used, or differential calculation based on a differential filter or differential approximation may be performed in a digital circuit or digital signal processing. Since these differentiation processes are a kind of high-pass filtering, they may be processed with a high cut-off frequency, or a moving average process may be performed on the result of the differentiation process. In addition, instantaneous frequencies such as ω ₁ (s ₁ , s ₂ , s ₃ ) above are used instead of the nominal frequency or the globally estimated frequency (the first moment of the spectrum) to simplify the calculation. Etc.) can also be used. This detection process is much faster than other detection processes. This processing includes envelope imaging of r (s ₁ , s ₂ , s ₃ ) (the magnitude of the analysis signal can be obtained), displacement (vector), velocity (vector), acceleration (vector), distortion (tensor) ), Distortion (tensor), etc. When measuring vectors and tensors, use multiple waves and beams, or multiple pseudo waves and beams obtained through spectral frequency division, etc., and use the Doppler equations derived from each of them. To obtain simultaneous equations (which may be a lateral modulation or over-determined system), in which case equation (30'-1) can be used to express each of those waves and beams, pseudo waves and beams. And each analytic signal is similarly determined and used. Similarly, it may be used for measuring temperature and the like.
This Hilbert transform method is faster than the Hilbert transform using multidimensional Fourier transform (Non-patent Document 13), and generates multiple beams and waves with different wave parameters and beam forming parameters in each time phase. If the steering direction is the same (however, the steering direction is the same, and the steering direction is not necessarily symmetrical with respect to the axis), the reception signal received by the reception transducer increases and beamforming and Hilbert conversion are performed. Since the number of times of implementation increases, it is effective in such a case. In some cases, the Hilbert transform may be performed at one time by regarding a superposition of a plurality of beamformed signals as one beamformed signal (formula (30′-1)). Yes (the instantaneous frequency obtained by partial differentiation is the combined frequency in the partial differential direction of the superposition of these beams and waves). The instantaneous phase imaging described above may also be performed on the superimposed composite wave as well. In the case where the physical aperture elements form a two-dimensional or three-dimensional distribution or a multi-dimensional array, the problem that a lot of processing time is required can be solved more effectively, and the high speed of this Hilbert transform becomes effective.

Further, the echo signal itself subjected to the transverse modulation by overlapping the intersecting beams or the intersecting waves can be directly processed as follows (FIG. 35 for the two-dimensional case and FIG. 35 for the three-dimensional case). 36).
In the two-dimensional case, the echo signal itself subjected to lateral modulation by superimposing two cross waves can be directly processed as follows. The echo signal is
When the first and second partial derivatives of s ₁ are obtained,
From (30A-1) and (30A-3), the instantaneous angular frequency ω ₁ (s ₁ , s ₂ ) is obtained in the same manner as described above. From (30A-2),
Is obtained. Here, in (30A-1), the initial value of the cosine function in the directions of s ₁ and s ₂ is omitted. Also, if (30A-2) is partially differentiated with respect to s ₂ ,
The instantaneous angular frequency ω ₂ (s ₁ , s ₂ ) obtained in the same manner by obtaining the first and second partial derivatives of s _{2 from} (30A-1), and the instantaneous angular frequency obtained above. Using ω ₁ (s ₁ , s ₂ ),
Is obtained. To determine the (30A-6) may be partially differentiated by s ₁ the (30A-1) in the next s _2, in this case, instead of (30A-4),
Is also found. An analysis signal is obtained by adding or subtracting (30A-1), (30A-4), (30A-6), or (30A-7).
Or
When,
Or
And subjecting these two independent analysis signals to displacement measurement methods such as a multidimensional autocorrelation method, a multidimensional Doppler method (Non-patent Document 13), and a demodulation method (Patent Document 7) to obtain a displacement vector Each envelope detection can also be obtained and each of them can be imaged. A plurality of obtained envelope detection results may be overlapped and used for imaging (speckle reduction effect). The detection is not limited to envelope detection, and other detection processing such as square detection can be performed, the real component and / or the imaginary component of the analysis signal can be used, and each of them can be used for imaging, A plurality of detection results obtained may be used for imaging by superimposing them (speckle reduction effect).
Since the actual calculation result of (30A-6) differs when the order of partial differentiation is reversed, two (30A-6) are obtained in this way, and (30A-8), (30A-8 ') , (30A-9), (30A-9 ′), and the analysis signals represented by the same equation may be used by superimposing and averaging (displacement measurement or imaging). An over-determined system for unknown displacement vector components may be realized (displacement measurement and imaging). A plurality of obtained envelope detection results may be overlapped and used for imaging (there is a speckle reduction effect).
In addition, the echo signal itself subjected to lateral modulation by overlapping the cross beams is as follows:
The analysis signal and the over-determined system can be obtained and used by the same procedure applied to (30A-1). In (30A-1 ′), (30A-1 ″), and (30A-1 ′ ″), as in (30A-1), cosine functions and sine functions in the directions of s ₁ and s ₂ are used. The initial value of is omitted.
In the three-dimensional case, the echo signal itself subjected to lateral modulation by superimposing three or four cross waves is
In the same way as in the two-dimensional case, the analysis signal is processed through the partial differentiation process.
And the analysis signal independent of this, and the total number of cross waves (3 or 4) can be obtained, and at least three of them can be combined or there are three unknown displacement components. Simultaneously, an over-determined system is obtained. Here, in (30B-1), initial values of cosine functions in the directions of s ₁ , s _2, and s ₃ are omitted. Similar to the two-dimensional case, three-dimensional echo imaging is also possible. Each signal may be imaged through detection such as envelope detection or square detection. In addition, the images may be overlapped to form an image (there is also a speckle reduction effect). Multiple analysis signals can be obtained by changing the order of the partial differential direction in the same way as two-dimensional detection signals, and multiple analysis signals represented by the same formula can be obtained, and an over-determined system can be realized using them. Displacement measurement and imaging may be performed (there is also a speckle reduction effect).
In addition, the echo signal itself subjected to lateral modulation by overlapping the cross beams is as follows:
Similarly, it is possible to obtain and use three or four analysis signals and signals when the order of the directions in which the partial differentiation process is performed is changed. However, (30B-1 ′), (30B-1 ″), (30B-1 ′ ″), (30B-1 ″ ″), (30B-1 ′ ″ ″), (30B- 1 '''''') , (30B-1 ' in the''''''), (30B-1) and similarly, the cosine function and sine function in the direction of the s ₁ and s ₂ and s ₃ The initial value is omitted.

Further, in the lateral modulation by superposition of cross waves (FIG. 35 in the case of two dimensions and FIG. 36 in the case of three dimensions), the Hilbert transform using multidimensional (fast) Fourier transform (Non-patent Document 13). Unlike the partial differential processing in the previous paragraph, it is also possible to realize a Hilbert transform by performing a one-dimensional (fast) Fourier transform.
In the case of two dimensions, if a two-dimensional echo signal in which cross waves overlap is expressed as (30A-1), a one-dimensional (fast) Fourier transform for each of s ₁ and s ₂ is performed, and each half-band is obtained. 1-dimensional inverse Fourier transform with zero-padded (negative band) spectrum,
as well as,
And (30C-1) or (30C-2) is similarly processed with respect to the coordinates of the cos function of the imaginary term (ie, s ₂ and s ₁ ),
Get. From these (30C-1), (30C-2), and (30C-3) real terms (common to them) and imaginary terms, the analytic signals (30A-8), (30A-8 '), (30A −9) and (30A-9 ′) can be obtained. As described above, independent two of these four expressions are obtained, and the multidimensional autocorrelation method and the multidimensional Doppler method (Non-patent Document 13) are obtained. The displacement vector can be obtained using a demodulation method (Patent Document 7). Further, detection results such as envelope detection and square detection of each of these two independent types are also obtained (there is also a speckle reduction effect). Regarding the amount of calculation, the total number of one-dimensional Fourier transforms or one-dimensional inverse Fourier transforms is the same as the number of methods for performing the two-dimensional Fourier transform reported in Non-Patent Document 13 (total number of times in six directions).
Also, in the case of three dimensions, if a laterally modulated echo signal in which three or four cross waves overlap is expressed as (30B-1), as in the case of the two dimensions, one-dimensional Fourier transform and Through the one-dimensional inverse Fourier transform, the analysis signal (30B-2) and the analysis signal independent of this can be combined to obtain the total number of cross waves (three or four), and at least three of them are simultaneous. Or, since there are three unknown displacement components, all of them can be combined to obtain an over-determined system. Similar to the two-dimensional case, three-dimensional echo imaging is also possible. The same number of one-dimensional Fourier transforms and one-dimensional inverse Fourier transforms are performed as in the method using the three-dimensional Fourier transform reported in Non-Patent Document 13. (When there are four waves, the total number of directions is 15).
In these cases, the displacement vector is similarly measured. In addition, each signal may be imaged through detection such as envelope detection or square detection. In addition, the images may be overlapped to form an image (there is also a speckle reduction effect). In the case of an over-determined system, displacement measurement and imaging may be performed in the same way (there is also a speckle reduction effect).
In the above, a new high-speed Hilbert transform method has been described for signals themselves that have undergone lateral modulation with overlapping cross waves, but the overlapped cross waves are the signals that are transmitted simultaneously and the received signals for each transmission. It is a stack of things. On the other hand, when the cross waves described before are separated (that is, the received signal when each is transmitted and the received signal when the signals are transmitted at the same time are processed and separated), For example, in the two-dimensional case, two independent wave signals ((30A-8) or (30A-8 ') and (30A-9) or (30A-9') when two crossing waves do not overlap. Real signal)
as well as,
Are each subjected to a one-dimensional Fourier transform and a one-dimensional inverse Fourier transform each time in two directions (that is, two-dimensional Fourier transform and two-dimensional inverse Fourier transform once), for a total of 8 Conversion processing for the number of directions is required. As described in Non-Patent Document 13 and as described above, the received signals that have been separated are superimposed, and the amount of calculation is smaller when a plurality of waves are received simultaneously. The same applies to the case of three dimensions (one-dimensional conversion processing is performed for a total of 18 directions when there are three cross waves, and a total of 24 directions when there are four cross waves; 6 times and 8 times).

  When this method is used, the image mainly represents the signal intensity determined by reflection or scattering and the phase or phase change. On the other hand, when the obtained instantaneous frequency is imaged, an image representing the influence of frequency modulation due to attenuation or scattering is obtained (similarly, gray and color can be displayed). Note that the presence of the instantaneous phase described above degrades the measurement accuracy even if it is a micro displacement when the tissue displacement measurement method based on the Doppler method or the classical measurement method is carried out independently. However, the inventor of the present application developed a phase matching method between frames to overcome this (for example, Non-Patent Document 15). Other reported methods of expanding and contracting signals representing tissue deformation may be effective, but the former phase matching method is used for high-intensity and random signals in tissue displacement and strain measurement. Indispensable for measurement (translation and rotation are possible). Normally, blood flow is measured using a narrowband signal, but according to this method, high-resolution measurement is possible, which opens up highly accurate viscosity measurement and the like. Measurement of multidimensional vectors and tensors is also possible. For blood flow measurement, it is possible to carry out a precision inspection by performing a process for performing phase matching.

  Further, the envelope detection described above is a conventional means to be performed on the generated image signal. However, in the frequency domain, the calculation based on the angular spectrum or the conjugate product of the spectrum, and each before the addition processing is performed. Those operations relating to the wave number (frequency) component are also useful (one of the non-linear processes in the present invention). In addition to the above, square detection, absolute value detection, or the like may be performed for amplitude detection. Note that what is obtained through Fourier transform from an image signal obtained by beam forming (that is, focus and deflection realized by applying delay or apodization) is a spectrum, but further, beam forming is performed. In this case, the result of Fourier transform in the axial direction and at least one lateral direction is an angular spectrum. That is, after the image signal is generated, beam forming processing may be further performed. In addition, this processing and other processing (spectral weight processing, nonlinear processing on signals, inverse filtering, etc., described in detail later), which has undergone super-resolution processing, are used for the above coherent addition And may be used for the incoherent addition described above. The target of addition is different or the same signal (they are before or after beamforming) and other processings, or their raw signals. Coherent addition is suitable for wideband (higher resolution) and higher SN ratio, while incoherent addition is suitable for speckle reduction and higher SN ratio. The reduction in speckle may be accompanied by a reduction in spatial resolution. However, processing with super-resolution may cause a high spatial resolution result without causing a problem. Incoherent addition is basically applied to a signal that has been subjected to some kind of detection (including power detection) and made positive. However, detection processing other than the envelope detection described above is performed by detection. This is a process in which coherence remains in the signal (at least the vibration of the wave is known). Envelope detection is also useful, but detection with such coherence is particularly useful as detection processing that does not impair spatial resolution. Compared with this, according to the envelope detection, the spatial resolution may be easily lowered.

  The operating mode may be determined by a command (signal) input to the apparatus. In addition, the wave to be observed (wave type and characteristics, intensity, frequency, bandwidth, sign, etc.) and propagating medium (propagation velocity, physical property value related to wave, attenuation, scattering, transmission, reflection, refraction, or , Their frequency dispersion, etc.) are given, and the received signal may be appropriately analog processed or digitally processed. The characteristics (intensity, frequency, bandwidth, code, etc.) of the generated image signal may be analyzed. Data obtained by the device according to the present embodiment may be used in other devices. The apparatus according to the present embodiment may be used as one of network devices, may be controlled by a network system control apparatus, and may be used as a control apparatus that controls the network device. In some cases, the control device controls a locally configured network.

  When the passive device according to the present embodiment is used as an active device, the transmission transducer (or applicator) 10 is connected to the transmission unit 31 of the device body 30, and the transmitter 31a is an analog device and is a trigger signal. If the control unit 34 generates and applies a trigger signal, or if the transmitter 31a has a mode in which the transmitter 31a operates in accordance with an external clock signal, any of the devices in the device main body 30 is provided. Or a clock signal from the control unit 34, or a mechanism in which the apparatus main body 30 operates with the clock signal of the transmitter 31a may be provided. In the case where the transmitter 31a is a digital device, the transmission and reception clock signals are synchronized by any one of these mechanisms. This is important when one image signal is generated based on a plurality of transmissions. If synchronization cannot be achieved, errors may be reduced in situations where the clock frequency or sampling frequency is high.

  As described above, arbitrary beam forming can be realized by digital processing without performing high-speed interpolation approximation through fast Fourier transform. Virtually any focusing and any steering (deflection) can be performed using a transducer array device with any aperture shape. In the present invention, as described in the methods (1) to (7), interpolation approximation processing may be performed in wave number matching of arbitrary beam forming, and beam forming may be performed at a higher speed. In order to perform approximate wave number matching with high accuracy, it is necessary to appropriately oversample the received signal at the cost of an increase in the amount of calculation. In that case, it is necessary to be careful that the number of data of the Fourier transform increases, unlike the case where the signal at an arbitrary position can be selectively generated when the interpolation approximation process is not performed. The second embodiment can be used in an ordinary apparatus as an apparatus and with respect to an operation mode (for example, an imaging mode, a Doppler mode, a measurement mode, a communication mode, etc.), and those and the above-described ones. It is not limited to.

  In the first and second embodiments described above, an electromagnetic wave, a vibration wave (mechanical wave) including a sound wave (compression wave), a shear wave, a shock wave, a surface wave, etc., or a wave such as a heat wave (surface wave or Regardless of transmission / reception focusing, transmission / reception steering, or transmission / reception apodization, the transmission / reception coordinate system differs from the coordinate system that generates the beam-formed signal. Arbitrary beam forming can be performed with high accuracy and high speed without performing interpolation approximation based on digital processing. Not only the frame rate when displaying the beam-formed signal is improved, but also high spatial resolution and high contrast can be obtained with respect to image quality, and further, displacement and deformation using the beam-formed signal, or Measuring temperature etc. will improve measurement accuracy. In the present invention, as described in the methods (1) to (7), interpolation approximation processing may be performed in wave number matching of arbitrary beam forming, and beam forming may be performed at a higher speed. In order to perform approximate wave number matching with high accuracy, it is necessary to appropriately oversample the received signal at the cost of an increase in the amount of calculation. In that case, it is necessary to be careful that the number of data of the Fourier transform increases, unlike the case where the signal at an arbitrary position can be selectively generated when the interpolation approximation process is not performed. High-speed beamforming realizes various applications by superimposing and spectral frequency division of waves or beams that are beamformed at high speed, and in the situation where received signals of unreceived beamforming are superimposed or spectral frequency divided To do. The application of the present invention is not limited to this. The high speed of processing has a great effect in multidimensional imaging using a multidimensional array. In addition, in the Fourier transform or inverse Fourier transform processing performed in the above calculation algorithm, it is desirable to perform fast Fourier transform including performing dedicated fast Fourier transform or fast inverse Fourier transform. Further, the present invention is not limited to the above-described embodiments, and many modifications can be made within the technical idea of the present invention by those who have ordinary knowledge in the technical field.

There are various measurement objects such as organic substances, inorganic substances, solids, liquids, gases, objects that follow rheology, living creatures, astronomical objects, the earth, and the environment, and the application range is extremely wide. Non-destructive inspection (Recent topics include inspection of inexpensive and simple ultrasonic metals and plastics (particularly Fiber-Reinforced Plastics using carbon fiber, glass fiber, etc.). In the past, we have proposed ultrasonic observation of rubber, which has strong ultrasonic attenuation), diagnosis, resource exploration, generation and production of materials and structures, and various physical and chemical repair and treatment monitoring This contributes to the application of the functions and physical properties that have been clarified, and in these cases, the subject to be measured is not disturbed greatly, and the conditions are non-invasive, minimally invasive and non-invasive. In some cases, accuracy is required. Ideally, the object may be observed in situ in situ. For example, when a three-dimensional wave can be observed, a three-dimensional displacement vector can be Doppler-observed, and if it is a normal Doppler, it is necessary to direct the propagation direction of the wave toward the observation target, but the sensor is directed toward the observation target. It is possible to observe the movement in any direction only (for example, ultrasonic echo method). Measurement techniques are also simplified. For example, when the eyelid is open, ultrasonic echo method is used when passing through or closing water, and when the eyelid is open, OCT is used to strain the eyeball distortion tensor, distortion rate tensor, shear wave. By observing the propagation, the viscoelasticity distribution and intraocular pressure of the eyeball can be reconstructed by the mathematical inverse problem. It is also possible to reconstruct blood viscosity, cardiac cavity pressure, blood pressure, etc. by ultrasonic Doppler observation of blood flow vectors in the heart cavity, blood vessel, fundus and retina. In addition, not only light but also ultrasonic waves can be applied to various biometric authentication including fingerprint identification (authentication) and iris authentication (including functional observations such as dynamics and temperature and various physical property observations). In some cases, the observation target can be observed in situ. For example, we can reconstruct the distribution of electrical properties such as the electrical conductivity and dielectric constant of neural networks and electrical and electronic circuits that are operating using mathematical inverse problems by observing the current density vector distribution based on the magnetic field distribution observation. The temperature distribution is observed to reconstruct the thermophysical distribution, and the internal strain tensors and strains of tires such as running cars, rubber pipes that are flowing fluid, and rubber of electric wires that are carrying current. Ultrasonic Doppler observation of the rate tensor to reconstruct the distribution of viscoelastic modulus and internal pressure, observation of the temperature inside them to reconstruct the distribution of thermophysical properties, heat generation, and perfusion, during human movement Viscoelasticity and tissue pressure can be reconstructed by observing muscle motion vectors in the same way. In addition, during the generation and growth of materials, the generation and growth processes can be monitored without changing physical conditions for observation. Paragraph 0094 describes a method of observing elastic waves for observing the anisotropy of elastic modulus (ultrasonic waves, MRI, OCT, etc. can be used for the observation). Isotropy can be observed by observing waves (various electromagnetic waves, mechanical waves, heat waves, etc.) related to each physical property in the same way. In other words, by adjusting the position and number of sources, directivity, etc., the overlapping of the waves to be observed (each electromagnetic wave, light, radiation, audible sound wave, ultrasonic wave, elastic wave, thermal wave) It is possible to control the propagation direction by observing and superimposing. Or, it is possible to adjust the position and number of sources, directivity, etc., and generate and observe a plurality of purely independent waves to improve the accuracy of reconstruction of physical properties (an over-determined system can be generated) ). For example, it can be applied to the design of devices (medium, source, etc.) that realize various surface waves and guided waves. Although the observation target is described as a wave here, a static or pseudo static field (strain tensor distribution, potential distribution, current density vector distribution, temperature distribution, etc.) may be set as the observation target. Sometimes static properties are reconstructed by observing critical fields.
In addition, when the S / N ratio of a wave directly sensed to observe those waves and fields is low, the superposition or addition averaging of the waves is effective. For example, when observing a current density vector by observing a human or animal brain magnetic field (which is very weak and often buried in the surrounding magnetic field) with a SQUID meter, visual, auditory, or somatic sensation By reconstructing the distribution of the current density vector by superimposing the cerebral magnetic field induced by (addition averaging), the accuracy may be obtained and the distribution of the electrical properties may be reconstructed. The current density vector distribution is observed for each induction, and they are superimposed (added and averaged) to reconstruct the electrical property distribution. In addition, when an object such as epilepsy that occurs suddenly is used as a target, reconstruction may be performed after overlapping observation magnetic fields or integrating observation time series. In addition, although addition averaging is performed in order to improve the SN ratio in terahertz observation (electric field observation), the electrical physical properties may be reconstructed based on such superposition. When the signal components of a plurality of events are included in superposition (addition averaging) or integration, their accumulation can be observed simultaneously, and the random signal components are suppressed. It is possible to carry out reconstruction of such superposed signals, for example, visualization of the running structure of the neural network used during observation by reconstructing the distribution of current density vectors and electrical properties. Or
The frequency dispersion of physical properties may be reconfigured by changing the frequency of the wave or observing a wideband wave.
In addition, treatment or repair may be performed on the target by the action of the wave itself, and the situation may be observed by performing beam forming on the response from the target at that time. Also, beam forming is performed in satellite communication, radar, sonar, etc., and an energy-saving and information-safe environment is realized, and accurate communication is possible. The present invention is also effective in normal communications including ad hoc communication devices and mobile devices. It can also be applied to sensor networks. When the object is dynamic, real-time characteristics are required. However, according to the present invention, digital beam forming can be completed quickly and with high accuracy in a short time.

<< Third Embodiment >>
In a wave such as an electromagnetic wave, light, dynamic vibration, sound wave, or heat wave, the behavior as a wave varies depending on the frequency, bandwidth, intensity, or mode. Many various wave transducers have been developed so far, and imaging using transmitted waves, reflected waves, scattered waves, and the like of these waves has been performed. For example, it is well known that ultrasonic waves having a high frequency among sound waves are used in non-destructive inspection, medical care, and sonar. Also in the radar, electromagnetic waves (microwaves, terahertz waves, infrared rays, visible light, radiation such as X-rays, etc.) having an appropriate frequency according to the object to be observed are used. The same applies to other waves.

  In imaging using these waves, the distribution of amplitude data obtained through orthogonal detection, envelope detection, and square detection is usually displayed as a gray image or color image in one, two, or three dimensions. . In Doppler measurement using these waves, raw coherent signals are processed (ultrasonic Doppler, radar Doppler, laser Doppler, etc.). Further, in the field of image measurement, it is well known that motion is observed using a signal made incoherent through detection (cross-correlation processing, optical flow, etc.). In medical ultrasound and sonar, imaging using physically generated harmonics, chords, and difference tones is also performed.

  Under such circumstances, the inventor of the present application has developed an ultrasonic imaging technique for differential diagnosis of cancerous lesions and sclerosis in human tissues. The inventor of the present application has improved the resolution and efficiency of HIFU (High Intensity Focus Ultrasound) treatment along with higher resolution of echo imaging and high-precision measurement imaging of tissue displacement. Their imaging based on reception of echoes during ultrasound emission is also performed. Such imaging is based on performing appropriate beam forming, and an appropriate detection method and tissue displacement measurement method are required.

  For example, the inventor of the present application has, as a beam forming method, a lateral modulation method using crossed beams, a spectral frequency division method, a method using many crossed beams, an over-determined system method, etc. Especially, quadrature detection and envelope detection as well as quadrature detection as detection methods for multidimensional received signals, and multidimensional autocorrelation method, multidimensional Doppler method, multidimensional cross spectrum phase gradient method as displacement vector measurement methods In addition, a phase matching method has been devised, and other techniques for reconstructing imaging of (viscous) shear modulus distribution and thermophysical property distribution based on displacement and strain measurement have been reported (Non-Patent Documents 13 and 30). reference). Some of them are already in clinical use. The present inventor's recent reports include ITEC (International Tissue Elasticity Conference), IEEE Trans. on UFFC, Ultrasound Study Group, Acoustic Imaging Study Group, etc.

  In this regard, the inventor of the present application has focused on nonlinear imaging. In medical ultrasound, nonlinear imaging (so-called harmonic imaging) based on the result of physical action in the propagation process of ultrasound is currently being performed. In the following, the application to diagnosis and treatment of nonlinear ultrasound will be described in particular.

  Harmonic imaging is due to the high propagation velocity of wave components with high sound pressure intensity (usually explained by the fact that the bulk modulus is large for high-intensity sound pressure), and the harmonics generated during propagation. It is for imaging wave components. In this harmonic imaging, a contrast agent (ultrasound contrast agent) may be used to enhance nonlinear effects in ultrasonic propagation.

  The effectiveness of the capillary blood flow imaging has been recognized in clinical practice, and there is already a long history (see Non-Patent Document 22). Doppler measurement using a non-linear component (harmonic component) is also possible, and in such a case, a report on multi-dimensional vector measurement realized by the present inventor will be made. In Non-Patent Document 23, a so-called pulse inversion method is used, and separation from the fundamental wave is performed.

  In addition, tissue imaging has a history of being performed prior to blood flow imaging. Originally, harmonics were separated by filtering (see Non-Patent Document 24), but now, the above-described pulse-in Separated by version method. When the transmitted signal has a wide band, the filtering method has a limit because it covers the fundamental and harmonic bands. In addition, there is a report that separates a fundamental wave and a harmonic wave represented by each dimension term based on the least square method in a multidimensional power polynomial composed of a power term (see Non-Patent Document 25).

  Recently, there are reports of applying harmonic components and chords in ultrasonic microscopes (see Non-Patent Document 26) and radiation pressure imaging (see Non-Patent Document 27). In addition, the nonlinear propagation and heat absorption are deeply related, and the HIFU is used by concentrating high-intensity ultrasonic waves at the focal position, including the case where cavitation occurs (Non-patent Document 28). Etc.). Also, when energy (or mode) is converted from ultrasonic waves to shear waves (for example, when sound waves are obliquely incident on a boundary where the acoustic impedance between soft tissue and bone changes greatly, or when shear occurs due to scattering) The generated high-frequency shear wave is easily absorbed by the tissue during propagation in the vicinity of the generation position (Girke).

  A contrast agent (see Non-Patent Document 29, etc.) used for the purpose of enhancing the nonlinear effect in HIFU treatment is also considered effective in these respects. The inventor of the present application has referred to the effect of coagulating blood and blocking the feeding artery for the treatment of cancer lesions 17 years ago, and believes that this effect can also be obtained. . Recently, an applicator having a frequency band comparable to that of a probe for clinical diagnosis has become available at a low cost, but the present inventor believes that it is necessary to develop a dedicated contrast agent. . The inventor of the present application considers at least a fragile characteristic and a hard-to-break characteristic as attractive characteristics, but recently, it is possible to use the same characteristic or several types for diagnosis. is there.

  Waves are affected by attenuation while propagating, so the wave energy decreases as the propagation distance increases. In addition, diffusion waves are also affected by diffusion. Under such circumstances, transmitted waves, reflected waves, or scattered waves reflect impedance changes, the presence of reflectors, or scatterers, and are used for imaging and Doppler measurements. In these merging, it is desirable that the signal includes a high-frequency component and has a wide band as much as possible or within a required range, and the same applies to Doppler measurement.

  However, normally, high-frequency signal components are strongly affected by attenuation, and as the propagation distance increases, the energy is lost, the signal is lowered in frequency, and becomes narrower. That is, imaging at a position far from the signal source is affected by a low signal-to-noise ratio (SN ratio) and a low spatial resolution. In Doppler measurement, the accuracy decreases. Reducing those effects of attenuation is extremely important in the engineering sense.

  In addition, if a high-frequency signal that cannot be realized by a single signal source can be generated, higher-resolution imaging and high-precision Doppler measurement can be performed. It may be possible to simply generate a high-frequency signal. Usually, the influence of attenuation is strong against high-frequency components. For example, in a microscope that is susceptible to the influence of attenuation, it is desirable to observe as deep as possible at a high frequency. Further, low frequency imaging or measurement using low frequency signals may be possible. Further, it may be possible to generate a low-frequency signal that cannot be realized by a single signal source. For example, the deep part of the object can be deformed at a low frequency. In medical ultrasonic images, nuclear magnetic resonance images, OCT, and laser applications, a deep tissue is deformed at a low frequency using a plurality of signal sources (Tissue Elasticity).

  For example, a vibration wave with a frequency lower than that frequency is generated by applying vibrations from multiple directions, or a plurality of ultrasonic beams are crossed at their focal positions to realize a low frequency force source there. The generated vibration wave may be an ultrasonic wave (longitudinal wave), and the generated vibration wave is a shear wave (transverse wave). In some cases, it may be observed with ultrasound. The propagation direction of the generated waves may be adjusted. If these signals can be realized theoretically or based on computation, the generated waves may be controlled. In addition, a detection method that can be easily performed in a short time, instead of processing of normal quadrature detection, envelope detection, and square detection is also important.

  Therefore, in view of the above points, the second object of the present invention is to enhance a high-frequency component having a relatively weak intensity or a lost high-frequency component in an arbitrary wave propagating from within a measurement target. It is an object of the present invention to provide an imaging apparatus capable of improving spatial resolution and measurement accuracy by performing or newly generating. The imaging device also enhances or simulates non-linear effects in the measurement target, or newly generates or performs virtual imaging when there is no non-linear effect in the measurement target. May be. A third object of the present invention is to generate a high-frequency signal that cannot be realized with a single wave source. Furthermore, a fourth object of the present invention is to realize a detection method that can be easily implemented in a short time.

  In order to solve the above problems, an imaging apparatus according to one aspect of the present invention performs (i) nonlinear processing using a nonlinear device at an arbitrary position in a propagation path for an arbitrary wave propagating from within a measurement target. And (ii) a process of generating an analog reception signal by receiving by the transducer and performing an analog nonlinear process on the analog reception signal; and (iii) a transducer. A non-linear reception processing unit for generating at least one of processes for generating a digital non-linear process on a digital received signal obtained by digitally sampling the analog received signal, Generates an image signal representing an image to be measured based on the reception signal obtained by the reception processing unit And an image signal generating unit.

  According to one aspect of the present invention, non-linear processing is generally performed on a signal having a frequency at which the influence of attenuation is not a problem in an arbitrary wave propagating from within a measurement target, so that the intensity is generally relatively weak. Spatial resolution and measurement accuracy can be improved by enhancing or newly generating high frequency components or lost high frequency components. In addition, waves arriving from signal sources of arbitrary waves such as electromagnetic waves, light, dynamic vibrations, sound waves, or heat waves, and transmitted waves, reflected waves, or scattered waves of waves emitted from those signal sources The non-linear effect in the measurement target can be enhanced by the processing including the multiplication and the power in the wave propagation and the processing including the analog calculation and the digital calculation for the coherent signal obtained by detecting the signal with the transducer. Alternatively, the same effect can be simulated, newly generated, or virtually realized.

  For example, in imaging and Doppler measurement using coherent signals, high-resolution imaging is realized using wideband signals containing high-frequency components compared to imaging using original signals, and the original signals are used. Compared with Doppler measurement, it is possible to realize measurement of displacement, speed, acceleration, strain, or distortion rate with higher accuracy. In addition, the same processing is performed on the same problem for the incoherent signal. As the hardware, a normal device can be used. Of course, analog processing (circuit) is faster than digital processing (circuit). A computer or a device having an arithmetic function (FPGA, DSP, or the like) can be used when performing calculations including higher-order calculations or having a wide degree of freedom.

  In particular, it is robust against the influence of attenuation in the wave propagation process, and it is also possible to generate a high-frequency component that cannot be realized with a single signal source, enabling high-resolution imaging and highly accurate Doppler measurement. It is also possible to generate a high-frequency signal that cannot be physically realized with a single signal source. When a plurality of 100 MHz ultrasonic transducers are used, it is possible to physically generate ultrasonic waves that are several times as high as that number, and to realize a high frequency that cannot be generated by a normal transducer. Further, it may be possible to simply generate a high-frequency signal. According to the present invention, such a high frequency can also be realized by calculation. Therefore, high-frequency waves and signals that cannot be physically realized can be generated. Similarly, measurement using low-frequency imaging or low-frequency signals can be realized. It is also possible to generate a low-frequency signal that cannot be physically realized with a single signal source. These signals can be realized theoretically or on the basis of computation to control the generated waves.

  For example, in an ultrasonic microscope, high frequency ultrasonic waves (signals) of several hundred MHz are applied to generate ultrasonic waves having a frequency higher than the frequency determined by the sound source, and the ultrasonic waves are robust against attenuation. Therefore, it is possible to realize an ultrasonic microscope capable of higher-resolution imaging and higher-precision Doppler measurement than usual. Also, low-frequency imaging and measurement using low-frequency signals can be performed. Moreover, when measuring the deformability of a structure | tissue, the deep part of object can be deformed with a low frequency, for example. In medical ultrasonic images, nuclear magnetic resonance images, OCT, laser applications, and the like, a deep tissue is deformed at a low frequency using a plurality of signal sources. The same applies to other imaging devices and Doppler devices. In addition, effects such as heating, heating, cooling, freezing, welding, heat treatment, cleaning, or restoration can be improved, and high resolution can be achieved at that time. Similar effects can be obtained for incoherent signals after various detections.

  Further, in terms of the technical aspect of signal processing, it is possible to easily perform processing of quadrature detection and envelope detection. For example, when the present invention is applied to a deflected beam or a deflected wave, an IQ signal obtained by orthogonal detection with respect to all coordinate axes can be obtained, so that envelope detection is facilitated. Further, when the present invention is applied to the cross beam, an IQ signal orthogonally detected with respect to each coordinate axis can be obtained. Therefore, only by performing normal Doppler signal processing in each direction, a displacement vector, velocity vector, acceleration vector, distortion tensor, Alternatively, the distortion rate tensor can be measured. Of course, in imaging, square detection can also be performed as detection processing.

  Transducer waves that have arrived from a signal source of arbitrary waves such as electromagnetic waves, light, mechanical vibrations, sound waves, or heat waves, or transmitted waves, reflected waves, or scattered waves of waves emitted from those signal sources Imaging and Doppler measurement using a coherent signal obtained by detection by means of radar is widely performed using an appropriate frequency for each medium in radar, sonar, nondestructive inspection, diagnosis, or the like. The wave generated from the signal source is also applied to heating, heating, cooling, freezing, welding, heat treatment, cleaning, restoration, and the like. Furthermore, recently, image measurement such as motion using an incoherent signal has been performed, and various imaging and measurement have been performed based on image processing and signal processing. The present invention is effective in all of these, and the applicability and marketability of the present invention are very high.

  FIG. 37 is a block diagram illustrating a configuration example of an imaging apparatus according to the third embodiment of the present invention. This imaging apparatus captures a physical object such as a displacement or a physical quantity in a measurement object based on an arbitrary wave such as an electromagnetic wave, light, dynamic vibration, sound wave, or heat wave coming from the measurement object. This is a non-destructive measuring device.

  As shown in FIG. 37, the imaging apparatus includes at least one transducer 110 that is both a transmission unit and a reception unit, and an imaging apparatus main body 120. The transducer 110 may be capable of generating and receiving an arbitrary wave such as an electromagnetic wave, light, dynamic vibration, sound wave, or heat wave. In this case, the transducer 110 can transmit an arbitrary wave to the measurement target 1 and can receive a reflected wave or a scattered scattered wave reflected in the measurement target 1. For example, when an arbitrary wave is an ultrasonic wave, an ultrasonic transducer that transmits an ultrasonic wave according to a drive signal and receives the ultrasonic wave to generate a reception signal can be used. It is well known that the ultrasonic elements (PZT, polymer piezoelectric elements, etc.) are different and the structure of the transducer is different depending on the application.

  Historically, narrowband ultrasound has been used in blood flow measurement, but the present inventor has found that soft tissue displacement and strain (including static cases) and shear waves that have been put to practical use in recent years. Including the measurement of propagation (velocity), the use of a broadband transducer for (echo) imaging has been realized for the first time in the world. The same applies to HIFU treatment, and continuous wave may be used, but the present inventor has developed using a broadband device in order to realize high-resolution treatment. When intense ultrasound is used, the tissue is stimulated within a range that does not produce a heating effect, and a force source may be generated in the measurement object 1 as described above. A transducer for (echo) imaging is used. Sometimes. Heat treatment, force source generation, and (echo) imaging may be performed simultaneously. The same applies to other wave sources and transducers. There are two types of transducers, contact type and non-contact type, and impedance matching of each wave is appropriately performed and used.

  Alternatively, as the transducer 110, a transmission transducer that generates an arbitrary wave and a reception transducer (sensor) that receives the arbitrary wave may be used. In this case, the transmitting transducer transmits an arbitrary wave to the measurement target 1, and the sensor transmits the reflected wave or scattered scattered wave reflected in the measurement target 1 or transmitted through the measurement target 1. Waves etc. can be received.

  For example, when an arbitrary wave is a heat wave, a heat source that is not intentionally generated such as sunlight, lighting, or metabolism in the living body may be used, but an infrared heater, heater, etc. An ultrasonic transducer that transmits a heating ultrasonic wave that is often controlled according to a drive signal (which may generate a force source in the measurement target 1), an electromagnetic wave transducer, a laser, etc. Also used. Infrared sensors that receive heat waves and generate received signals, pyroelectric sensors, microwave and terahertz wave detectors, temperature sensors such as optical fibers, and ultrasonic transducers (temperature dependence such as ultrasonic sound velocity and volume change) The temperature change can be detected by using a magnetic property) or a nuclear magnetic resonance signal detector (temperature can be detected by using a chemical shift of nuclear magnetic resonance). For each wave, a transducer that can receive properly is used.

  When the transducer 110 actively generates a wave according to the drive signal, the transducer 110 may positively generate a wave including harmonics. For example, the transducer 110 generates a wave according to the nonlinear characteristics of the wave source or the circuit of the transmitter 121 that drives it. The transducer 110 may have one transmission surface or reception surface, or may have a plurality of transmission surfaces or reception surfaces. The transmission surface of the transducer 110 may be provided with a nonlinear device 111 that performs nonlinear processing on the generated arbitrary wave. The receiving surface of the transducer 110 may be provided with a nonlinear device 111 that performs nonlinear processing on an arbitrary wave propagating from within the measurement target 1. The nonlinear device 111 is not necessarily in contact with the transmission surface and the reception surface of the transducer 110, and may be provided at an arbitrary position on the propagation path of an arbitrary wave.

  Further, an action device 112 such as a filter (a spectroscope or the like), a shield, an amplifier, or an attenuator may be provided between the measurement target 1 and the transmission surface or the reception surface of the transducer 110. When the nonlinear device 111 is used, the action device 112 may be provided on both the front and rear sides of the nonlinear device 111. The transducer 110, the non-linear device 111, and the action device 112 may be separated or may be integrated in combination.

  FIG. 37 also shows a case where a wave source is provided in the measurement object 1, or it may be directly controllable by the control unit 133. In addition, a wave generated by the transducer 110 may be concentrated using a lens or the like, or a focus transmission may be performed using a plurality of transducers 110 to generate a wave source (such as a dynamic wave or Using a heat wave source or mechanical waves or electromagnetic waves, for example, to generate a new electromagnetic wave for a magnetic material that may be a contrast agent, or to a physical action or physical property between waves Including the case of controlling the intensity and direction of propagation of waves by the stimulation of

  Of course, there may be a wave source in the measurement object 1 (for example, the electrical activity of the brain and the heart is the current source, and the heart is the force source). In addition, the wave source may be controllable or the wave source may not be controlled, and the measurement target 1 may be observed in situ, or the wave source itself may be an imaging target or a measurement target. Sometimes it is. Alternatively, such a wave source may exist outside the measurement target 1 from the beginning, and may be handled in the same manner and become a measurement target. In some cases, the nonlinear device 111 and the action device 112 are appropriately provided between the wave source and the measurement target 1.

  Furthermore, in order to obtain a non-linear effect in the measurement object 1 or to positively enhance the non-linear effect in the measurement object 1 at least partially in the measurement object 1, a contrast agent (non-linear enhancement such as a microbubble) Agent) 1a may be injected. As the contrast medium 1a, a substance having affinity for a target lesion or fluid in the measurement target 1 may be used. As described above, a wave generated by a plurality of wave sources may arrive at a transducer that receives a wave.

  The transducer 110 is supplied with a drive signal from the imaging apparatus main body 120 by wire or wireless and / or outputs a reception signal to the imaging apparatus main body 120. In the case of wireless, a wireless receiver and / or a wireless transmitter is provided in the transducer 110, and a wireless transmitter and a wireless receiver are also provided in the imaging apparatus main body 120.

  In Part A, the imaging apparatus main body 120 includes a transmitter 121, a receiver 122, a filter / gain adjustment unit 123, a nonlinear element 124, a filter / gain adjustment unit 125, a detector 126, an AD (Analogue- to-digital) converter 127 and storage device 128 may be included. In Part B, the imaging apparatus main body 120 includes a reception beamformer 129, a calculation unit 130, an image signal generation unit 131, a measurement unit 132, a control unit 133, a display device 134, and an analog display device 135. May be included. The control unit 133 controls each unit of the imaging apparatus main body 120.

  When a plurality of transducers 110 are used, part A having the same number of channels as the number of transducers 110 may be provided. The case where these transducers 110 form an array will be described later. As shown in FIG. 37, when a multi-channel part A is provided, a reception signal output from the multi-channel part A storage device 128 may be supplied to the receive beamformer 129 of the part B. . Alternatively, each part A may be connected to each part A in cascade and processed independently, and in this case, the received signal output from the storage device 128 of each channel part A is transmitted to each channel. To the receiving beamformer 129 of Part B. The plurality of transducers 110 may be related to different types of waves, and in that case, the nonlinear effects of different types of waves may be observed simultaneously, and not the nonlinear effects in the same wave. May observe non-linear effects between different types of waves.

  In Part A, the transmitter 121 to the detector 126 may be configured by analog circuits, or at least some of them may be configured by digital circuits. Further, in Part B, the reception beamformer 129 to the control unit 133 may be configured by a digital circuit, or a central processing unit (CPU) and software for causing the CPU to perform various processes are recorded. It may be constituted by a recording medium. As the recording medium, a hard disk, flexible disk, MO, MT, CD-ROM, DVD-ROM, or the like can be used. Note that at least a part of the reception beamformer 129 to the control unit 133 may be configured by an analog circuit.

  The transmitter 121 includes a signal generator such as a pulser that generates a drive signal in accordance with a trigger signal supplied from the control unit 133. The control unit 133 may control the frequency, carrier frequency, bandwidth, transmission signal strength (apodization), or the waveform or shape of a pulse wave, burst wave, or the like. The control unit 133 may set the trigger signal timing or delay time for each channel. Alternatively, the timing of the trigger signal output from the control unit 133 may be constant for all channels, and the transmitter 121 may further include a delay element that delays the trigger signal according to the delay time set by the control unit 133. .

  The transmitter 121 causes the transducer 110 to generate an arbitrary wave by applying the generated drive signal to the transducer 110. For example, the transmitter 121 includes a drive signal amplifier (can also serve as apodization) to adjust the intensity of transmitted waves and the intensity of generated harmonics, and a delay whose delay time is set by the control unit 133. An element may be further included. A drive signal including harmonics may be generated and used. When apodization is performed instead of resonance, or when forced oscillation is performed, various waves are generated and used, such as generating a chirp wave. When the drive signals generated by the multi-channel transmitters 121 are applied to the plurality of transducers 110, transmission beam focusing, steering, and plane wave transmission can be performed by setting a delay time by the control unit 133. (A plane wave is a narrow-band wave in a direction orthogonal to the propagating direction, and is effective when the bandwidth is increased).

  The transmitter 121 may further include a non-linear element (an analog device such as a transistor, a diode, or a non-linear circuit, or a digital device such as a non-linear arithmetic unit) in which the non-linear effect is similarly set. The frequency and carrier frequency, bandwidth, apodization, delay, and nonlinear effect prepared in advance may be set, but they may be controlled by the operator via the control unit 133, In the arithmetic unit 130, they may be determined and controlled adaptively according to the observation situation.

  When driving a plurality of transducers 110, the frequency, carrier frequency, bandwidth, apodization, delay element, and nonlinear element of each channel are controlled, but these patterns are set in advance. In some cases, these patterns may be controlled by the operator via the control unit 133. In the calculation unit 130, these patterns may be determined and set adaptively according to the observation situation. is there.

  The receiver 122 includes, for example, an amplifier that amplifies the received signal or an attenuator that attenuates (can also serve as an apodization or a filter), and may further include a delay element whose delay time is set by the control unit 133. The receiver 122 may further include a non-linear element that generates a non-linear effect (an analog device such as a transistor, a diode, or a non-linear circuit, or a digital device such as a non-linear arithmetic unit). Similar to those of the transmitter 121, they may be set, including when receiving waves by multiple transducers 110. The receiver 122 amplifies the reception signal generated by the transducer 110 that has received the arbitrary wave, and outputs the amplified reception signal to the filter / gain adjustment unit 123 and the AD converter 127.

  The filter / gain adjustment unit 123 includes a filter that limits the frequency band of the reception signal, or an amplifier or attenuator that adjusts the gain of the reception signal. The filter / gain adjustment unit 123 adjusts the frequency band or gain of the received signal and outputs the received signal to the nonlinear element 124.

  The nonlinear element 124 includes, for example, an analog device such as a transistor, a diode, or a nonlinear circuit, and performs analog nonlinear processing on the received signal. This non-linear processing may be a power operation for at least one frequency component signal included in the received signal, or may be a multiplication operation for a plurality of frequency component signals included in the received signal ( Hall effect elements can be used).

  The filter / gain adjustment unit 125 includes a filter that limits the frequency band of the reception signal, or an amplifier or attenuator that adjusts the gain of the reception signal. The filter / gain adjustment unit 125 adjusts the frequency band or gain of the received signal and outputs the received signal to the detector 126 and the AD converter 127.

  The filter / gain adjusting units 123 and 125 and the nonlinear element 124 may be set to those prepared in advance by the control unit 133, but they are controlled by the operator via the control unit 133. In addition, they may be determined and controlled adaptively in accordance with the observation state in the calculation unit 130. When a plurality of transducers 110 are driven, they are controlled independently in each channel. However, in some cases, the patterns may be set in advance, or the patterns may be set by the operator via the control unit 133. May be controlled, and those patterns may be determined and set adaptively in accordance with the observation state in the calculation unit 130.

  For example, when the reception beamforming is not performed, the detector 126 performs an envelope detection process or a square detection process on the reception signal to generate an analog image signal. In addition, displacement measurement may be performed through quadrature detection. The analog display device 135 displays an image of the measurement target 1 or the wave source based on the image signal generated by the detector 126 and the measurement result.

  The AD converter 127 selects the reception signal output from the filter / gain adjustment unit 125 when performing analog nonlinear processing on the reception signal, and receives the receiver 122 when not performing analog nonlinear processing on the reception signal. The received signal output from is selected. The AD converter 127 digitally samples an analog reception signal to convert it into a digital reception signal. A digital reception signal obtained by the AD converter 127 is output to the storage device 128. The storage device 128 is configured by a memory such as a RAM, for example, and stores a reception signal.

  The reception signal stored in the storage device 128 is supplied to the reception beam former 129. Note that while signals are processed by the receive beamformer 129, the signals being processed may be temporarily stored in the storage device 128 or the external storage device 140, and these signals are read out as necessary. When a single or a plurality of transducers 110 are used, the reception beamformer 129 may perform harmonic separation or the like by a pulse inversion method, a polynomial fitting method, or the like (the same processing is performed in the arithmetic unit 130). Sometimes).

  When a plurality of transducers 110 are used, the reception beamformer 129 performs reception beamforming processing on the reception signals supplied from the storage devices 128 of a plurality of channels. For example, the reception beamformer 129 synthesizes the reception signals by delaying the reception signals of a plurality of channels in accordance with the delay time set by the control unit 133 and performing an addition or multiplication operation to obtain a focal point. Is generated, a new received signal is generated.

  Alternatively, when the receiver 122 includes a delay element, the multi-channel receiver 122 may delay each received signal according to a delay time set by the control unit 133. The reception beamformer 129 synthesizes reception signals by performing addition or multiplication operations on the reception signals of a plurality of channels. During reception beam forming, the reception beam former 129 may perform apodization.

  In addition, a (multi-dimensional) fast Fourier transformer is mounted on the imaging apparatus main body 120 to obtain the spectrum of the received signal, so that filtering, beam or wave characteristics (frequency, carrier frequency, bandwidth) The frequency or carrier frequency in any direction, bandwidth in any direction, waveform, beam shape, steering direction, propagation direction, etc.) may be adjusted. Spectral frequency division (see Non-Patent Document 30) can be used to obtain a plurality of received signals (corresponding to a plurality of pseudo different beamformings) from a single received signal, and to perform nonlinear processing on these signals. is there. These processes may be performed on a signal subjected to nonlinear processing.

  In this imaging apparatus, the plurality of wave signals generated by using a single or a plurality of transducers (those subjected to or not subjected to nonlinear effects) are stored in the storage device 128 or the external storage device 140, The reception beamformer 129 or the calculation unit 130 reads out the results and performs addition (overlay, linear processing) or multiplication (nonlinear processing) calculations, which may be used for imaging or various measurements. In that case, a phasing process is appropriately performed.

  The arithmetic unit 130 mainly performs digital non-linear processing on the digital reception signal output from the reception beamformer 129. This non-linear processing may be a power operation for at least one frequency component signal included in the reception signal, or may be a multiplication operation for a plurality of frequency component signals included in the reception signal. As described above, the calculation unit 130 may also serve as the reception beamformer 129. Including such cases, while the signals are processed, the signals being processed may be temporarily stored in the storage device 128 or the external storage device 140, and these signals are read as necessary.

  Here, the transducer 110 to the action device 112 and the receiver 122 to the calculation unit 130 perform nonlinear processing on an arbitrary wave propagating from the measurement target 1 or a reception signal obtained by receiving the arbitrary wave. A non-linear reception processing unit is configured. In the non-linear reception processing unit, at least one of the non-linear device 111, the non-linear element 124, and the calculation unit 130 generates an arbitrary wave propagating from the measurement target 1 or a received signal obtained by receiving the arbitrary wave. Non-linear processing is applied to this. In other cases, the nonlinear effect may be obtained as described above.

  That is, the non-linear reception processing unit performs (i) non-linear processing using the non-linear device 111 at an arbitrary position on the propagation path for an arbitrary wave propagating from within the measurement target 1 and then receives it by the transducer 110. Processing for generating a reception signal may be performed. Further, the non-linear reception processing unit generates an analog reception signal by receiving (ii) an arbitrary wave propagating from the measurement target 1 by the transducer 110, and converts the analog reception signal into, for example, an analog non-linear signal. The element 124 may be used to perform analog nonlinear processing. The non-linear reception processing unit is obtained by (iii) receiving an arbitrary wave propagating from the measurement target 1 by the transducer 110 to generate an analog reception signal, and digitally sampling the analog reception signal. For example, digital non-linear processing may be performed on the digital received signal using the digital arithmetic unit 130. In other cases, the nonlinear effect may be obtained as described above.

  The image signal generation unit 131 and the measurement unit 132 select the reception signal output from the calculation unit 130 when performing digital nonlinear processing on the reception signal, and receive the signal when the digital nonlinear processing is not performed on the reception signal. A reception signal output from the beamformer 129 is selected.

  The image signal generation unit 131 generates an image signal representing an image of the measurement target 1 based on the reception signal obtained by the nonlinear reception processing unit. Alternatively, the image signal generation unit 131 may generate an image signal based on a reception signal obtained by non-linear processing and a reception signal not subjected to non-linear processing. Further, the image signal generation unit 131 may generate an image signal representing an image of the measurement target 1 by selectively using a reception signal obtained when non-linear processing is not performed. For example, the image signal generation unit 131 generates an image signal by performing an envelope detection process or a square detection process on the received signal. The display device 134 generates an image signal representing an image of the measurement target 1 based on the image signal generated by the image signal generation unit 131.

  The measurement unit 132 measures a displacement or the like in the measurement target 1 using at least one of a plurality of signals obtained by nonlinear processing. For example, when observing the propagation of a mechanical or electromagnetic wave, the measurement unit 132 measures the particle displacement or particle velocity caused by the wave propagation of its own wave or another wave based on the measured displacement. In that case, the image signal generation unit 131 generates an image signal representing wave propagation based on the particle displacement or particle velocity measured by the measurement unit 132. In the case where a plurality of waves arrive, measurement may be performed through separation of the waves in advance or separation through analog processing or digital processing after reception.

  Alternatively, when observing the propagation of thermodynamic waves, the measuring unit 132 uses an infrared sensor, a pyroelectric sensor, a microwave or terahertz wave detector, a temperature sensor such as an optical fiber, an ultrasonic transducer (ultrasonic wave) as the transducer 110. Temperature change is detected using temperature dependency such as sound velocity and volume change of sound waves) or nuclear magnetic resonance signal detector (temperature is detected using chemical shift of nuclear magnetic resonance). You may do it. In that case, the image signal generation unit 131 generates an image signal representing the propagation of thermodynamic waves based on the heat wave measured by the measurement unit 132. The image signal generated by the image signal generation unit 131 and the measurement data obtained by the measurement unit 132 can be stored in the external storage device 140.

  In the above, the non-linear reception processing unit obtains the result of the power calculation by the non-linear processing for the arbitrary wave propagating from within the measurement object 1 or based on the arbitrary wave by the non-linear processing being the power calculation. Thus, as a result of chords, difference tones, and overtones, a reception signal that is higher or lower in frequency than the reception signal obtained when non-linear processing is not performed may be obtained. Further, the nonlinear processing may be a multiplication operation. The non-linear processing may be a higher-order non-linear processing, and the result of the power operation or multiplication operation may be mainly obtained from the effect.

  Thus, the received signal has a wider band than the received signal obtained when the non-linear processing is not performed when the arbitrary wave has a plurality of different frequency components. Alternatively, the high frequency received signal becomes a higher frequency, higher spatial resolution, lower side lobe, or higher contrast harmonic signal than the received signal obtained when non-linear processing is not performed. . Alternatively, the low-frequency received signal becomes a signal in a band including a direct current obtained by substantially quadrature detection of the harmonic signal. The image signal generation unit 131 generates an image signal based on at least one signal obtained by nonlinear processing.

  Alternatively, a plurality of arbitrary waves propagating from within the measurement target 1 are transmitted in the measurement target 1 in the propagation direction, steering angle, frequency, carrier frequency, pulse shape, beam shape, frequency or carrier frequency in any direction, Alternatively, when at least one of the bandwidths is different, the non-linear reception processing unit applies at least one of the processes (i) to (iii) to a plurality of arbitrary waves that arrive in an overlapping manner. Also good. The image signal generation unit 131 generates an image signal based on the reception signal obtained by the nonlinear reception processing unit.

  Here, the non-linear reception processing unit passes a plurality of arbitrary waves by passing the plurality of arbitrary waves to at least one of the analog delay device and the analog storage device as the action device 112 before receiving the plurality of arbitrary waves. The wave may be overlapped at each position in the measurement target 1. This is so-called aberration correction.

  In addition, the nonlinear reception processing unit obtains the result of the power calculation by the nonlinear processing for the superposition of a plurality of arbitrary waves propagating from the measurement target 1, or the nonlinear processing is a power calculation, Based on a plurality of arbitrary waves, as a result of chords, difference tones, and harmonics, a reception signal that is higher or lower in frequency than a reception signal obtained when non-linear processing is not performed may be obtained. This also provides the same effect as described above. The image signal generation unit 131 generates an image signal based on at least one signal obtained by the nonlinear reception processing unit.

  Alternatively, a plurality of arbitrary waves propagating from within the measurement target 1 are propagated within the measurement target 1 in the propagation direction, steering angle, frequency, carrier frequency, pulse shape, beam shape, and frequency or carrier in any direction. When at least one of frequency or bandwidth is different, the non-linear reception processing unit performs at least one of the processes (i) to (iii) for a plurality of arbitrary waves that arrive in a superimposed manner. In addition, at any time after receiving a plurality of arbitrary waves, the received signal may be separated into a plurality of signals by using an analog or digital device or based on analog or digital signal processing. The image signal generation unit 131 generates an image signal representing the image to be measured based on at least one of the plurality of signals separated by the nonlinear reception processing unit. In the non-linear operation, a multiplication effect is obtained. In addition, after analog or digital aberration correction is performed, these signals are added again to obtain a power effect.

  Alternatively, a plurality of arbitrary waves propagating from within the measurement target 1 are propagated within the measurement target 1 in the propagation direction, steering angle, frequency, carrier frequency, pulse shape, beam shape, and frequency or carrier in any direction. Waves that do not overlap, waves that are shielded with the action device 112 so that they do not overlap, and devices (analog or digital) when at least one of frequency or bandwidth is different, The non-linear reception processing unit may perform at least one of the processes (i) to (iii) on at least one of the waves separated using analog or digital signal processing. . The image signal generation unit 131 generates an image signal based on the reception signal obtained by the nonlinear reception processing unit.

  Here, the non-linear reception processing unit passes a plurality of arbitrary waves by passing the plurality of arbitrary waves to at least one of the analog delay device and the analog storage device as the action device 112 before receiving the plurality of arbitrary waves. The wave may be overlapped at each position in the measurement target 1. This is so-called aberration correction.

  Alternatively, the non-linear reception processing unit passes the analog reception signal through at least one of the analog delay device and the analog storage device, or delays the digital reception signal by digital calculation, or the digital reception signal May be passed through the digital storage device so that a plurality of arbitrary waves overlap at each position in the measurement object 1.

  In addition, the nonlinear reception processing unit obtains the result of the power calculation by nonlinear processing for each of a plurality of arbitrary waves propagating from within the measurement target 1, or the nonlinear processing is a power calculation. As a result of chords, difference tones, and overtones, a received signal that has a higher or lower frequency than the received signal that is obtained when non-linear processing is not performed may be obtained based on each of the arbitrary waves . This also provides the same effect as described above. The image signal generation unit 131 generates an image signal based on at least one signal obtained by the nonlinear reception processing unit.

  Alternatively, the non-linear reception processing unit obtains the result of the multiplication operation by non-linear processing for each of the plurality of arbitrary waves propagating from within the measurement target 1, or the non-linear processing is a multiplication operation, so that a plurality of arbitrary Based on the wave, as a result of chords and difference tones or overtones, a reception signal having a higher or lower frequency than the reception signal obtained when non-linear processing is not performed may be obtained.

  As a result, the received signal has a wider band than the received signal obtained when non-linear processing is not performed when a plurality of arbitrary waves have a plurality of different frequency components. Alternatively, the received signal whose frequency is increased or decreased is made higher in spatial resolution, lower sidelobe, or higher in contrast to the received signal obtained when non-linear processing is not performed, and at least any arbitrary 1 The signal is substantially orthogonally detected in the direction and includes a direct current, and becomes a signal in a band including a harmonic frequency in another at least one direction. The image signal generation unit 131 generates an image signal based on at least one signal obtained by nonlinear processing.

  In the above, the image signal generation unit 131 performs arbitrary detection processing on at least one of the plurality of signals obtained by the nonlinear processing, or performs arbitrary detection processing on the superposition of the plurality of signals, Alternatively, an image signal may be generated by superposing a plurality of signals after performing arbitrary detection processing on the plurality of signals.

<< Fourth Embodiment >>
Next, a fourth embodiment of the present invention will be described. FIG. 38 is a block diagram illustrating a configuration example of an imaging apparatus according to the fourth embodiment of the present invention and a modification thereof. The imaging apparatus according to the fourth embodiment and its modification is an apparatus that generates a wave by driving a plurality of transducers 110 or transducer arrays, or receives a wave by them to perform imaging (see FIG. 38). Indicates a transducer array), and components having the same performance as the components in the third embodiment can be used.

  In the imaging apparatus according to the fourth embodiment shown in FIG. 38A, a plurality of transducers 110 or transducer arrays are used in the imaging apparatus according to the third embodiment shown in FIG. A transducer 110 or element is connected to a plurality of transmitters 121 or receivers 122, respectively. However, in the imaging apparatus main body 120a, a plurality of transmitters 121 or receivers 122 are provided in one part A ′.

  An output from a plurality of transducers 110 or a transducer array is phased using a delay element in the receiver 122, or an addition processing unit adds (linear processing) to an unphased analog reception signal. ) Or a multiplication processing unit performs multiplication (non-linear processing, Hall effect element or the like is used) analog processing. As a result, reception beamforming is performed, and therefore the reception beamformer 129 (FIG. 37) is unnecessary in Part B.

  In addition, a digital reception signal obtained through the AD converter 127 is stored in the storage device 128. Part B of the imaging apparatus main body 120a is configured so that the control unit 133 controls each unit to obtain all nonlinear effects that can be realized by the third embodiment, based on the received signal. Similarly, imaging and measurement imaging are performed. In FIG. 38, wiring from the control unit 133 to the receiver 122 and the like is omitted.

  Also in the fourth embodiment, similarly to the transmitter and receiver in the third embodiment, a delay can be given to the drive signal or reception signal of each transducer, and transmission or reception focusing, steering, etc. It is also possible to perform processing. In the fourth embodiment, one AD converter 127 and one storage device 128 are provided as compared with the third embodiment in which the same number of AD converters 127 and storage devices 128 as the number of channels are required. Since it suffices to provide it, the apparatus can be simplified.

  On the other hand, in the imaging apparatus according to the modification of the fourth embodiment shown in FIG. 38B, in part A ″ of the imaging apparatus main body 120b, the transmission delay element 121a and the reception delay element 122a are replaced by the transmitter 121 and the reception. It is provided outside the container 122. Unlike the imaging apparatus shown in FIG. 38 (a), the imaging apparatus shown in FIG. 38 (b) is phase-adjusted in the reception delay element 122a or added to an unphased analog received signal. The processing unit performs analog processing of addition (linear processing), or the multiplication processing unit performs analog processing of multiplication (non-linear processing), and then receives by the receiver 122. Therefore, since only one transmitter 121 and one receiver 122 are provided, the apparatus can be greatly simplified, and the same nonlinear effect as in the third embodiment can be obtained.

  An imaging apparatus according to the third embodiment shown in FIG. 37, an imaging apparatus according to the fourth embodiment shown in FIG. 38 (a), and an imaging according to a modification of the fourth embodiment shown in FIG. 38 (b). Devices or other types of imaging devices and components thereof can be used simultaneously. For example, each of the coherent or incoherent image signals and measurement results obtained by using a plurality of types of devices can be displayed, or can be displayed side by side at the same time, or they can be superimposed or multiplied. You can also display things. Basically, signals obtained from received signals at the same time or the same time phase can be targeted. Even in the same imaging apparatus, the same processing may be performed when a plurality of image signals and measurement results are obtained using signals received at the same time or in the same time phase. The target signal is an analog signal or a digital signal after phasing, and the addition or multiplication is performed by analog processing (using a Hall effect element or the like) or digital processing (using a calculator or an arithmetic unit). .

  The imaging apparatus according to the first or fourth embodiment of the present invention uses an analog computing unit, a digital computing unit, a computer, or a similar device (FPGA, DSP, etc.) of various devices to perform nonlinear calculation on a signal. Is based on. As will be described in detail later, the non-linear operation is centered on obtaining a power or multiplication effect. However, the operation itself is not limited to this, and may be a high-order calculation having other non-linear characteristics. The effects can be extracted or separated through polynomial fitting, spectral analysis, pulse inversion method, numerical calculation, signal processing, or the like. Non-linear operations may be performed not only on signals but also on waves, and before reception, the waves are extracted using devices (time or space, or filters or spectrometers of those frequencies) Or can be separated. A dedicated device may be available.

  As described above, the imaging apparatus includes the transducer 110 for arbitrary waves, the transmitter 121, and the receiver 122, and includes the nonlinear device 111, the nonlinear element 124, or the arithmetic unit 130, and is necessary. According to the above, a data storage device (memory, hard disk, photograph, CD-RW, or other recording medium), a display device, and the like are provided. Each of these general-purpose devices can be assembled and configured, or the non-linear device 111, the non-linear element 124, the arithmetic unit 130, or other non-linear devices can be subjected to the non-linear processing of the present invention. Non-linear processing can also be performed by adding devices to be performed.

  As a wave transmitted from the transmitter 121 or the transducer 110 serving as a wave source, a pulse wave, a burst wave, a coded wave such as phase modulation or the like is used, and imaging and measurement with spatial resolution are possible. is there. However, when measurement is possible without requiring spatial resolution, this is not the only case, and a continuous wave may be used.

  The generated wave is determined by a conversion characteristic from an electric signal (driving signal) to a wave in the transducer 110, and an appropriately designed device and driving signal are used. For example, in the case of light waves, various light sources (coherent or incoherent, light emitting diodes (LEDs), light mixing LEDs, (variable wavelength) lasers, optical oscillators, etc.) are used. An acoustic transducer or vibrator is used. In the case of a vibration wave, an actuator-based vibration source is used, and in the case of a heat wave, a heat source or the like is used. Thus, in the present embodiment, the transducer 110 that generates various types of waves can be used.

  The transducer 110 to be used includes typical transducers for the above-described various waves, and it is also possible to actively use a transducer that is not normally used because it has nonlinear characteristics. Usually, in ultrasonic elements, when high pressure is applied, ultrasonic waves containing harmonics are generated by nonlinear phenomena, but harmonic imaging is performed to extract nonlinear components generated in the medium by the pulse inversion method. In some cases, only the signal in the fundamental band is used by filtering out harmonic components.

  Also in this embodiment, a nonlinear wave may be actively generated and used. That is, when nonlinear characteristics appear at the time of transmission, the transmission wave is in a state including harmonics, but in the present invention, this may be effectively applied. On the other hand, a wave that does not contain a nonlinear component is generated to search for a nonlinear phenomenon in the measurement object.

  In addition, in a wave having a non-linear component, a non-linear phenomenon may occur in the harmonics. When the transmitted wave contains harmonics from the beginning or there are multiple intersecting waves (frequency, carrier frequency, pulse shape, beam shape, frequency or carrier frequency seen in each direction, or bandwidth (That is, the wave parameters other than the propagation direction and the steering angle are different), including the pulse inversion method, spatio-temporal filtering, spectral filtering, or polynomial fitting for the received signal as described later. The present invention may be implemented after separation by analog processing or digital processing such as signal processing or the like, or may be performed without separation. In addition, the refractive index of the medium is changed by applying a physical stimulus to the propagation process, such as an obstacle such as an obstacle, a filter device, or a spectroscope (in time or space, or those frequencies). Each of the waves may be received in a state where the waves are separated in advance using a switch). If the source of each wave can be controlled, each wave may be generated independently and observed separately.

  In addition, after a wave is generated in the transducer 110 and before the wave propagates to the measurement target, a device that directly generates a non-linear phenomenon with respect to the wave is used. May be propagated to. It is also possible to use a device that generates a non-linear phenomenon after or during propagation within the measurement object. A multiplication effect may be obtained by combining or mixing waves or signals.

  For example, with respect to light, (i) nonlinear optical elements (for example, optical harmonic generation devices used for wavelength conversion of laser light to a short wavelength region, etc.), (ii) optical mixing devices, and (iii) optical parametric generation , Stimulated Raman scattering, coherent Raman scattering, stimulated Brillouin scattering, stimulated Compton scattering, or devices that produce optical parametric effects such as four-wave mixing, (iv) multiphoton transitions such as normal Raman scattering (spontaneous emission Raman scattering) (V) a device that generates a nonlinear refractive index change, (vi) a device that generates an electric field dependent refractive index change, and the like can be used. Couplers and optical fibers can also be used effectively. Multi-point observation (multi-channel) is possible, and it is also suitable for signal processing.

  When light is used, it relates to a wide range of fields such as optoelectronics, nonlinear optical effects, or laser engineering for light generation, control, or measurement. Optical devices that are normally used can be used as the working device 112 and the nonlinear device 111, and a dedicated device may be used. These include optical amplifiers (photon multitubes, etc.), absorbers (attenuators), reflectors, mirrors, scatterers, collimators, (variable focus) lenses, deflectors, polarizers, polarizing filters, ND filters, deflected beams Splitter (separation), shield, optical waveguide (using photonic crystal, etc.), optical fiber, optical Kerr effect device, nonlinear optical fiber, optical mixing optical fiber, optical fiber for modulation, optical confinement device, optical memory, coupler (coupler) , Directional coupler, distributor, mixer / distributor, spectrometer, dispersion-shifted optical fiber, bandpass filter, phase conjugator (by degenerate four-wave mixing or photorefractive effect, etc.), switch by phase control of ferroelectric semiconductor, phase For delay devices, phase correction devices, time inverters, optical switches, optical masks, etc. The that coding etc., some when used alone, sometimes in combination. This is not the case. Under optical control (wavelength conversion / switching / routing), optical node technology, optical cross-connect (OXC), optical add / drop multiplexing (OADM), optical multiplexer / demultiplexer, or optical switch element is used. May constitute an optical transmission network or an optical network, and optical signal processing may be performed.

  For detection, a CCD camera, a photodiode, a mixed photodiode, or a virtual source (also as a wave source) described herein can be used. Optical signal processing includes time and spatial filters, correlation calculation and matched filter processing, signal extraction, heterodyne and superheterodyne (low frequency signals can be obtained and demodulated), homodyne, etc., and electromagnetic wave detection A vessel may be used.

  In particular, examples of nonlinear media include carbon disulfide, sodium vapor, semiconductors such as silicon and gallium arsenide, quantum wells, and organic dyes such as fluorescein and erythrosin. For crystals such as barium titanate, there is also a self-pump that performs four-wave mixing without supplying a pump wave from the outside.

  For other waves such as visible light, infrared light, microwaves, terahertz waves, and radiation, each general-purpose device can be used, but a dedicated device may be realized and used. Not only SAW but also devices having a relationship between vibration system and electromagnetic system are useful. Nonlinear devices can also be used. There are various things that exhibit nonlinearity in heat conduction, such as alumina and zirconia synthesis, solder, and layered cobalt oxide. Heat acts on optical devices, creating non-linearities, and their applications can be widely considered.

  In addition, although the transducer 110 has a contact type and a non-contact type with respect to a measurement object, an impedance matching device for each wave may be required as an action device. This is also true between devices in the apparatus and in electrical circuits, but a matching device may be used between devices in the measurement space. For example, when observing a living tissue by ultrasonic waves, gel or water is used as a matching material. In an ultrasonic microscope, a sample is usually observed on a gantry, but an array type or a mechanical scan type (the element or element array moves mechanically through a matching material such as water in the housing). In some cases, it is easy to install on the sample (the direction can be freely determined, etc.). It may also be possible to observe directly in situ or in vivo without being cut out (in vitro). Many ultrasonic microscopes have a fixed type whose focal position is determined by a lens or the like, and this is a good method particularly when such an element or an element array is used. Therefore, the mechanical scan is not limited to the horizontal direction and the elevation direction, and may be movable in the propagation direction. For RF waves, an antenna is used, and an electrolyte gel and an electrode, or a SQUID meter, etc. are used for observing biological tissue potentials and magnetic fields. Smaller ones may be used (such as a microscope). A weak signal may not have non-linearity. In such a case, the non-linearity may be generated in a pseudo manner or virtually. When the non-linear signal is weak and cannot be observed, the non-linearity is also enhanced.

  The nonlinear device may be integrated with the transmitter 121 or the transducer 110, or the nonlinear device may be separately assembled and used. In this way, non-linear devices can perform non-linear operations on the wave itself by using non-linear devices at arbitrary positions, not only for signals after reception, including high frequency and wide band. it can.

  In addition, when passively observing waves, the present invention may be applied to cases where the wave source cannot be controlled. Various methods or devices may be used to determine the signal source position and direction of arrival, signal source strength, signal source size and distribution, and the present invention may be applied. Sometimes the source location and direction of arrival are required. At that time, they may be obtained by separating the waves and signals, or the waves and signals may be separated after obtaining the source and direction of arrival of the signals and waves, or both are obtained at the same time. Sometimes. Once the wave source and direction of arrival are determined, the accuracy of receive beamforming is improved. The signal is subjected to signal processing such as analog processing or digital processing, and a filter, a spectroscope, or the like of time or space or those frequencies can be used for the wave.

  When a wave propagated through a medium including a measurement object is received by the transducer, the transducer used for transmission may be used for reception (when a reflected signal is observed). On the other hand, a transducer other than the transducer used for transmission may be used for reception. In that case, when the transmitting transducer and the receiving transducer are in the vicinity (when a reflected signal is observed), or when the transmitting transducer and the receiving transducer are in different positions (for example, observing a transmitted wave, a refracted wave, etc.) In some cases.

  In addition, the transducer 110 may have a single aperture, or a plurality of transducers 110 may be arrayed in a closely adjacent state (one-dimensional array, two-dimensional array, or three-dimensional array). There are also cases where a sparse arrangement or a remote arrangement is used at the same time. There are various shapes of openings (circular, rectangular, flat, concave, convex, etc.), and their directivities vary. Some elements are integrated with openings in multiple directions, and others have multidirectional directivity at the same position. In addition to scalar measurement such as potential, pressure, or temperature, there are some that perform vector measurement such as electromagnetic wave and electric field vector. Some are polarized. Of course, even with the same wave, the materials and structures of the elements are diverse. Moreover, the arrangement | positioning using them is also various, for example, there exist some which the opening has faced in many directions.

  FIG. 39 is a schematic diagram illustrating an arrangement example of a plurality of transducers. 39, (a1) shows a plurality of transducers 110 that are densely arranged in a one-dimensional array, and (b1) shows a plurality of transducers 110 that are sparsely arranged in a one-dimensional array. . (A2) shows a plurality of transducers 110 that are densely arranged in a two-dimensional array, and (b2) shows a plurality of transducers 110 that are sparsely arranged in two dimensions. (A3) shows a plurality of transducers 110 densely arranged in a three-dimensional array, and (b3) shows a plurality of transducers 110 sparsely arranged in a three-dimensional shape.

  A beam may be generated or adjusted in an analog manner using a lens or the like at the opening of the transducer, but may be adjusted by the drive signal. In addition, the imaging apparatus according to the present embodiment includes a mechanical scanning device having a maximum of 6 degrees of freedom (degrees of freedom in three translational directions and three rotational directions), and the mechanical scanning device includes at least one transducer 110 or at least one transducer. By mechanically moving the array in at least one direction, scanning of the measurement object 1, adjustment of the focal position, and steering may be performed.

  On the other hand, when a plurality of transducers 110 are used, transmitters 121 having the same number of channels as the number of transducers 110 are provided to generate the same number of drive signals as the number of transducers 110 to be driven. Alternatively, by using a delay element group, a plurality of drive signals are generated from a limited number of generation signals, thereby forming a desired beam forming (focusing at a desired position or steering in a desired direction). ) May be performed.

  A normal analog or digital beamformer can also be used. The beam forming (including the case of receiving only) may be performed in parallel processing to improve the real-time property when scanning the measurement target.

  In addition, at the same time, a plurality of transducers 110 may be driven to perform a plurality of beam forming simultaneously. Alternatively, beam forming may be performed a plurality of times using different transducers 110 at different times within a time period in which simultaneous phase signals are allowed to be received, including when the transmitter 121 is switched and used. The same transducer may be subjected to mechanical scanning, and beam forming may be performed multiple times.

  In each beamforming, classical aperture synthesis may be performed, including the case of performing mechanical scanning, and normal delay addition (Delay-and-Summation) or delay multiplication based on the present invention (Delay) -and-Multiplication) (both monostatic type and multistatic type). At the time of transmission, a plane wave may be generated without performing focusing. In this case, a wide area can be observed in a short time. At that time, the plane wave may be steered. A wave may be received as a plane wave or may be dynamically focused (when steering during transmission, it is better to steer during reception). A plane wave is a narrow-band wave in a direction orthogonal to the propagating direction, and is effective when the band is widened.

  FIG. 40 is a diagram for explaining the form of waves when a one-dimensional transducer array is used. In FIG. 40, (a) shows wave focusing, and a wave beam narrowed down to a focus position determined by setting a delay time is formed during transmission or reception. (B) shows wave steering, and a wave beam deflected in a direction determined by setting of a delay time is formed at the time of transmission or reception. (C) shows transmission or reception of a plane wave, and a plane wave directed in a direction determined by the setting of the delay time is formed. A plane wave is a narrow-band wave in a direction orthogonal to the propagating direction, and is effective when the band is widened.

  Note that, before reception by the transducer 110, the waves are passed through at least one of the analog delay device and the analog storage device, so that the plurality of waves overlap at each position in the measurement target 1. is there. Further, an analog signal obtained after reception by the transducer 110 is passed through at least one of an analog delay device and an analog storage device, or a digitally sampled digital signal obtained after reception is delayed by digital computation, Alternatively, a plurality of waves may be overlapped at each position in the measurement target by passing through a digital storage device. So-called phase aberration correction may be performed as described above or may be performed in connection with the phasing of the beam forming described above. There are various devices. For example, in light, an optical fiber can be a delay line, and an optical confinement device can be a delay device or a storage device.

  On the other hand, with respect to the measurement target, there may be a case where a signal that is strongly subjected to a nonlinear phenomenon as a result of propagation through the measurement target may be observed, but conversely, a nonlinear component may not be obtained. In general, a nonlinear phenomenon is easily observed when the intensity of the wave is strong, and it is difficult to observe the nonlinear phenomenon when the intensity is weak. In any case, the present invention can be implemented. The received signal may be separated into independent signals by performing appropriate signal processing or the like, and the present invention may be implemented.

  For the signal separation, analog devices of various waves (time or space, or filters or spectrometers of those frequencies) may be used, and analog processing or digital processing (based on signal processing ( (Decoding for the above coding, processing for obtaining the center of gravity of the spectrum through spectral analysis, processing for obtaining an analysis signal and obtaining instantaneous frequency, MIMO, SIMO, MUSIC, or independent signal separation processing) is there. In the passive case, the signal source position and direction of arrival, the intensity of the signal source, the size and distribution of the signal source may be obtained using various methods or devices, and the present invention was implemented. Later, the signal source position and direction of arrival may be determined. Simultaneously with beam forming, the signal source position and direction of arrival, the intensity of the signal source, and the size and distribution of the signal source may be required. As will be described in detail later, signal separation may be performed with high accuracy in a situation represented by harmonics or the like by performing nonlinear processing. Specifically, in the frequency domain after performing high frequency and wide band (when the order is greater than 1) by low power calculation or low frequency and narrow band (when the order is less than 1) , Sometimes done with high accuracy. It is easy to restore the signal after separation by multiplying the power of the power using the inverse power.

FIG. 41 is a diagram illustrating the angle of the beam direction and the arrival direction of the wave and the center of the spectrum in the spatial domain and the frequency domain in the case of two-dimensional measurement. 41A shows the beam direction angles θ1 and θ2 of the beam 1 and the beam 2 at the point of interest (x, y) in the spatial domain. Further, (b) shows the centroid of the spectrum of the beam 1 and the beam 2 and the instantaneous frequency (fx, fy) of the beam 1 in the frequency domain. In some cases, the beam 1 or the beam 2 corresponds to a wave of a grating lobe or a side lobe.
By the way, in the array type sensor, if the element pitch is coarse, a signal that causes aliasing in the element array direction (originally digital space) is received and beamforming is performed. Therefore, the angular spectrum of the received raw signal or after beamforming is performed. In the signal, the signal in the folded band is filtered and removed. When the element width is reduced and the element pitch is shortened as described above, a wide band is generated in the horizontal direction as confirmed by the angular spectrum, and a wide band signal can be generated in the horizontal direction by beam forming. Need to be processed. These processes are necessary in the case of all beam forming processes. Since the beam forming signal can be generated within the signal band of the angular spectrum of the received raw signal, the steering angle that can be realized by using the element array can be confirmed.

  Basically, beam forming is performed in analogy with respect to a wave, or when a plurality of transducers 110 are used, beam forming (focusing or steering) is performed. As described above, signal separation may be performed and then beam forming may be performed, but signal separation may be performed after beam forming.

  In addition, when performing aperture plane synthesis processing, it is possible to generate focusing signals at different positions and steering signals in different directions from the same received signal set (Delay-and-Summation or Delay based on the present invention). -and-Multiplication). It is also possible to implement the present invention for those generated signals. The transmitter 121 and the receiver 122 may be integrated or separated.

  There are various non-linear elements 124, and diodes and transistors can be used for electrical analog signals received by the transducer 110. In addition, any non-linear element that applies a non-linear phenomenon to a signal by a circuit can be used, including those applying a superconducting phenomenon. Also, a distributed-constant nonlinear element can be used. An appropriate one is used in accordance with the frequency of the wave (signal). Waves or signals may be appropriately gain adjusted using various amplifiers and attenuators.

  The non-linear operation may be performed using a non-linear device that produces a non-linear phenomenon directly on the wave before being received at the transducer 110. For example, with respect to light, (i) nonlinear optical elements, (ii) optical mixing devices, (iii) optical parametric effects, (iv) multiphoton transitions such as normal Raman scattering (spontaneous emission Raman scattering), (v Non-linear refractive index change or (vi) electric field dependent refractive index change can be used. For other waves as well, non-linear devices can be used as well. The nonlinear devices may be integrated with the transducer 110, or the nonlinear devices may be separately assembled and used. Further, the nonlinear phenomenon itself at the time of conversion from a wave to an electric signal in the transducer 110 used at the time of reception may be used.

  In any of the above cases, there are a case where an analog operation (nonlinear processing) is applied to the wave itself and an analog operation is applied to the signal after reception. In some cases, the signal is subjected to a nonlinear operation using a computer or a similar device (FPGA, DSP, or the like).

  When the imaging apparatus according to an embodiment of the present invention is referred to as an analog type, the calculation is performed by analog processing as described above. It is displayed by a display device such as digital) and recorded on a storage medium such as a photograph (analog or digital) or holography as necessary. Alternatively, it may be digitized through AD conversion, recorded in a digital data storage medium such as a memory, a hard disk, or a CD-RW as necessary, and displayed using a display device.

  On the other hand, when referred to as a digital type, the digital nonlinear arithmetic processing includes the case where the analog signal is AD converted after appropriate analog processing (gain adjustment or filtering) and the signal is stored in a memory or a hard disk as a recording medium. As necessary, data is stored in a data storage device (the above-mentioned photograph or digital recording medium) and displayed on a display device.

  In the above configuration, a nonlinear phenomenon in the measurement object may be included in the received signal. In this case, the effect can be enhanced by using the analog device or the digital device, but the nonlinear component In a received signal that does not include, it is possible to newly generate a nonlinear effect, simulate a nonlinear effect, or virtually realize it. Further, the nonlinear effect (harmonic component) generated in the measurement target, the nonlinear component (harmonic component) generated in the signal source, and the effect of the nonlinear calculation may be separated. In exceptional cases, including the case where non-linear operation is not performed, the above-described devices and signal processing may be used to separate the former two non-linear effects (non-linear components).

  In the above description regarding the imaging apparatus, the case where a transducer (transducer) for the wave to be observed is used has been described. The propagation of shear waves that dominate as vibration waves having a low frequency in human tissues can be observed using the Doppler effect of ultrasonic waves that are also vibration waves.

  It is also possible to optically capture the propagation of sound such as audible sound waves and ultrasonic waves. The optical treatment is a treatment of electromagnetic waves in general and includes radiation such as X-rays. Sometimes audible sound waves are observed using ultrasonic waves. The heat wave can also be observed by using an infrared camera based on radiation, a change in sound velocity of microwaves, terahertz waves and ultrasonic waves, a change in volume of the object, a chemical shift of nuclear magnetic resonance, or using an optical fiber. This is due to incoherent processing such as coherent signal processing or image processing. The cases where the behavior of the wave of interest can be observed using other waves are not limited to those, and in any case, the measurement result is an analog signal or a digital signal. Therefore, the present invention can also be implemented for those observed waves (signals). In addition to the Doppler effect, the physical properties of the medium are modulated by the wave of the observation target, and the wave used for sensing may be interpreted as being modulated. In these, the process which detects the wave which received the Doppler effect and modulation is useful. In particular, electromagnetic waves can easily observe waves propagating in various directions by applying polarized waves, and can easily grasp structures having various directions. On the other hand, sound waves can be measured in various ways based on divergence as described herein. Radiation measurement is also important. Various remote sensing is performed using microwaves in addition to temperature distribution measurement. For example, scattering and attenuation are measured, and distributions such as raindrops, moisture, and atmospheric pressure are measured. Even in such a case, it is effective to obtain a high spatial resolution by various processes including the beam forming described in the present specification, and in particular, an effect of observing a desired position at a high speed is obtained. An effect of observing an arbitrary surface, region, and space directly and at high speed can be obtained without depending on image processing after the image is generated.

  In the above description of the imaging device, the nonlinear arithmetic device for electromagnetic waves, vibrations including sound, thermal waves, or signals corresponding to them has been described. However, the nonlinear effect between different types of physical energy can be enhanced. , Simulate non-linear effects, or virtually realize non-linear effects (that is, do not produce non-linear effects other than to produce non-linear effects physically, chemically, or biologically) In this case, the signals received at different times can be obtained by simultaneously using the devices related to the plurality of types of waves used, or by receiving the waves at the same time. As a basis, the present invention can also be implemented. That is, the present invention can handle a case where a plurality of types of waves are generated simultaneously and a case where a single type of waves are generated independently.

  In addition, in vibration and heat wave including electromagnetic waves and sound, if the frequency is different, the dominant behavior is different depending on each measurement object (medium), and the name is different (the type may be different). For example, regarding electromagnetic waves, there are radiations such as microwaves, terahertz waves, and X-rays, and regarding vibrations, shear waves are not transmitted as waves in the megahertz band due to the influence of attenuation when human soft tissue is targeted. Ultrasonic waves are dominant, but at low frequencies such as 100 Hz, the characteristics of incompressibility are strong, and shear waves are dominant.

  The present invention can enhance the nonlinear effect between waves with different behaviors, simulate the nonlinear effect, or virtually realize the effect. In that case, the present invention can also be implemented on the basis of signals received at different times in the case of simultaneous reception of waves using devices related to a plurality of types of waves. Of course, there is a limit that phenomena such as attenuation, scattering, or reflection of these waves have dispersion characteristics and should be used appropriately in consideration of the S / N ratio of the received signal. However, the scope of application of the present invention is very wide, including the ability to physically generate high frequency components or to generate high frequency components that cannot be captured.

  In addition, when actively observing the nonlinear effect in the measurement object and when performing the nonlinear processing according to the present invention, both of them can be used by switching them, or both can be used at the same time. Through computation, it is sometimes performed to elucidate nonlinear effects in a measurement object.

  Next, an embodiment in which the present invention is applied to an ultrasonic echo signal using the configuration of the imaging apparatus described above will be described. Generation of harmonics in the ultrasonic propagation process is represented by multiplication or power. In particular, chords and difference tones are represented by multiplication of waves having different propagation directions or frequencies (see Non-Patent Document 27), and harmonics are generally represented by the power of waves of the same frequency ( (See Non-Patent Document 25). It is likely to occur as a physical phenomenon when the wave intensity is high. The wave distortion has an effect of increasing with propagation with respect to the high-intensity component, but is more susceptible to attenuation during propagation than the fundamental wave during propagation. On the other hand, when the intensity is not so strong, only superposition (sum or difference) is strongly observed as wave interference, and an application of this is the lateral modulation method developed by the present inventor ( (See Non-Patent Documents 13 and 30).

  FIG. 42 is a diagram showing two deflected beams used in the lateral modulation method in a two-dimensional space. In FIG. 42, the horizontal axis indicates the horizontal position y, and the vertical axis indicates the depth direction position x. Here, as a representative example, there are 2 cases where beam forming is performed in any one direction (direction of angle θ in the figure) and when lateral modulation is performed with any one direction as an axis (X axis). In one case, the effect of nonlinear calculation after reception beamforming is confirmed. This calculation can be easily extended to a three-dimensional space, and it can be confirmed that the same effect can be obtained in a three-dimensional space. In the following, “λ” is a wavelength corresponding to the centroid frequency of the ultrasonic wave. In addition, the distance x in the depth direction and the distance y in the lateral direction are t at the time until the ultrasonic wave transmitted from the origin is reflected at a certain point and returns to the origin, and the ultrasonic wave propagates at time t / 2. It represents the distance.

<0> Lateral modulation: Superposition of two beams or waves (plane waves, etc.) in the directions of angles θ ₁ and θ ₂ (simultaneous transmission / reception or superposition of each transmission / reception)
The superposition (addition, that is, sum) of two RF echo signals is expressed by the following equation.
A (x, y) cos [2π (2 / λ) (xcosθ ₁ + ysinθ ₁ )]
+ A ′ (x, y) cos [2π (2 / λ) (xcosθ ₂ + ysinθ ₂ )] (0 ′)

Here, assuming that reflection or scattering is equal and A (x, y) = A ′ (x, y), a coordinate consisting of the X axis in the center of the propagation direction of the two waves and the Y axis perpendicular to it. In (X, Y), the superposition of two RF echo signals is expressed by the following equation.
A (x, y) cos {2π (2 / λ) cos [(1/2) (θ ₂ −θ ₁ ) X]}
× cos {2π (2 / λ) sin [(1/2) (θ ₂ −θ ₁ ) Y]} (0)
In this way, lateral modulation is realized in the (X, Y) coordinate system. The two waves may have different frequencies. For example, in the following <2> and <3>, non-linear processing is performed. In the case of lateral modulation in a three-dimensional space, there are two directions of modulation, and therefore it is necessary to generate at least three cross beams (see Non-Patent Documents 13 and 30).

<1> Calculation of Power of One Beam or One Wave in θ Direction The RF echo signal is expressed by the following equation.
A (x, y) cos [2π (2 / λ) (xcosθ + ysinθ)]
In this case, for example, the square is expressed by the following equation (51).
(1/2) A ² (x, y) × {1 + cos [2π (2 · 2 / λ) (xcosθ + ysinθ)]} (51)
In this way, the second harmonic component is generated at the same time as the DC component, and the basebanded signal is also obtained at the same time (the envelope signal is also obtained directly). The calculated square echo signal has a wider bandwidth than the spectrum of the fundamental wave due to the effect of the product of different frequencies in the band, and the pulse length and beam width are shortened, resulting in a high spatial resolution.

As a further easy-to-understand example, for example, when the RF echo signal at the position in the depth direction x has the frequencies f ₁ and f ₂ , the square echo signal is expressed by the following equation by the square calculation.
e _I (x; f ₁ , f ₂ ) ² = e _II (x; 0,2f ₁ , 2f ₂ , f ₁ + f ₂ , f ₁ -f ₂ )
Thus, the square echo signal has direct current (frequency 0) and signal components of frequencies 2f ₁ , 2f ₂ , f ₁ + f ₂ , and f ₁ -f ₂ .

  That is, those signals generated by the power operation have a plurality of different frequency signal components compared to a wave received when the wave has a plurality of signal components having different frequencies compared to a wave received without a non-linear operation. The harmonics are widened with respect to the direction having a higher frequency, higher spatial resolution, lower side lobe, or lower than the wave received when non-linear operation is not performed. A signal that has at least one effect of increasing the contrast, and a signal (baseband signal) generated in a band including direct current is a signal obtained by substantially quadrature detection of harmonics. Waves can be imaged based on at least one.

  When higher power calculation is performed, a signal component having a high frequency n times the fundamental wave is obtained by the nth power, and the spatial resolution is further increased. Strictly speaking, the basebanded signal is different from the signal obtained by quadrature detection of the second harmonic (normal baseband signal), and the calculation result purely includes direct current, but it does not depend on the processing. High-resolution images can be easily obtained as compared with the echo images. Note that the DC component generated by the nonlinear calculation is obtained from the intensities of high frequency, low frequency, harmonics, etc. generated at the same time, and the DC component included in the baseband signal is basically excluded. Sometimes the calculation is simplified and all direct current of the basebanded signal is removed. By this processing, it may be possible to image deeper than the case of including direct current, without adjusting the luminance depending on the depth.

  Harmonic signals and low-frequency signals are expressed in various forms (four arithmetic operations of sine waves and cosine waves) according to the double angle or dividing angle theorem, and when necessary, digital Hilbert conversion (Non-Patent Document 13) See). Measured harmonics can also be used. These are obtained by calculating a nonlinear signal at each position for a wave of arbitrary intensity. Unlike nonlinear components that are physically accumulated in the propagation process and are affected by attenuation, new harmonics or low It realizes frequency imaging.

<2> Calculation of Power of Lateral Modulation Echo Signal For example, the square of the equation (0) is expressed by the following equation (52).
A (x, y) ² × cos ² {2π (2 / λ) cos [(1/2) (θ ₂ −θ ₁ ) X]}
× cos ² {2π (2 / λ) sin [(1/2) (θ ₂ −θ ₁ ) Y]}
= A (x, y) ² × [1 + cos {2π (2 · 2 / λ) cos [(1/2) (θ ₂ −θ ₁ ) X]}
+ Cos {2π (2 · 2 / λ) sin [(1/2) (θ ₂ −θ ₁ ) Y]}
+ Cos {2π (2 · 2 / λ) cos [(1/2) (θ ₂ −θ ₁ ) X]}
× cos {2π (2 · 2 / λ) sin [(1/2) (θ ₂ −θ ₁ ) Y]}] (52)
In this manner, a direct current (the above-described baseband signal), two signals of the second harmonic detected in different directions, and a lateral modulation signal of the second harmonic are obtained. As in <1>, high resolution is also achieved. Basebanded signals and other high-order harmonic signals can be calculated in the same manner as in <1>.

As an easy-to-understand example, the cross-echo signals at position (x, y) are e ₁ ((x, y); (f ₀ , f ₁ )) and e ₂ ((x, y); (f ₀ , When expressed as f ₂ )) and symmetric in the y direction, the square signal of the superposition signal is expressed by the following equation.
[e ₁ ((x, y); (f ₀ , f ₁ )) + e ₂ ((x, y); (f ₀ , f ₂ ))] ²
= E ₁ ((x, y); (f ₀ , f ₁ )) ² +2 e ₁ ((x, y); (f ₀ , f ₁ )) e ₂ ((x, y); (f ₀ , f ₂ )) + e ₂ ((x, y); (f ₀ , f ₂ )) ²
= E ₁ '((x, y); (0,0), (2f ₀ , 2f ₁ )) + e ₁₂ ' ((x, y); (2f ₀ , 0), (0,2f ₁ ), (0,2f ₂ ))
+ E ₂ '((x, y); (0,0), (2f ₀ , 2f ₂ ))
Thus, the square signal of the superposition signal has the frequencies (0,0), (2f ₀ , 2f ₁ ), (2f ₀ , 2f ₂ ), (2f ₀ , 0), (0,2f ₁ ), ( It can be seen that it has 0,2f ₂ ) signal components.

  That is, those signals generated by the power operation are the harmonic signal of each of the linearly superimposed signals (the signals corresponding to the crossed waves) and the basebanded signal (in a band including at least one direction of direct current). Signal), and when the wave has signal components of a plurality of different frequencies, the band is broadened with respect to the direction having the plurality of different frequency signal components compared to the wave received when non-linear operation is not performed. The harmonics are at least one of higher frequency, higher spatial resolution, lower side lobe, or higher contrast than the corresponding wave received when non-linear operation is not performed. The baseband signal is a signal obtained by performing quadrature detection or substantially quadrature detection of harmonics in each direction or in a plurality of directions, and at least one of these signals. Based on, it is possible to image the wave. When crossed waves and beams have different frequencies or are not symmetrical with respect to the coordinate axis, the same processing can produce chords and difference sounds in a multidimensional space. Used for. They also work in situations where other parameters are different.

  In the three-dimensional space, the lateral modulation needs to generate at least three crossed beams as described above. In this case, the harmonics of each beam are similarly set as the obtained baseband signal. In addition to a signal subjected to quadrature detection (a nearby signal including a direct current), a signal obtained by quadrature detection in only one arbitrary direction or two arbitrary directions is obtained. That is, the polarity of the frequency in the symmetric direction is opposite to the symmetric axis, so the sum becomes zero. All waves and beams may be generated symmetrically with respect to the coordinate axis, but this is not a limitation. Also, the frequency and other parameters may be different.

<3> Multiplication of Two Waves of Lateral Modulation Echo Signal For example, since two waves in the equation (0 ′) can be handled separately, in considering the product, in order to show an easy-to-understand equation, the propagation direction is x Assuming that the two directions are symmetric with respect to the axis, θ ₁ = −θ ₂ , and the multiplication (product) of the two RF echo signals is expressed by the following equation (53).
A (x, y) cos [2π (2 / λ) (xcosθ ₁ + ysinθ ₁ )]
× A '(x, y) cos [2π (2 / λ) (xcosθ ₁ −ysinθ ₁ )]
= A (x, y) A '(x, y) × {cos [2π (2 · 2 / λ) cosθ ₁ x]
+ Cos [2π (2 · 2 / λ) sinθ ₁ y]} (53)
Thereby, two signals of the detected second harmonic are obtained in different directions. These are signal components obtained also in the equation (52).

As an easy-to-understand example, the cross-echo signals at position (x, y) are e ₁ ((x, y); (f ₀ , f ₁ )) and e ₂ ((x, y); (f ₀ , When expressed as f ₂ )) and symmetric in the y direction, signal multiplication is expressed by the following equation:
e ₁ ((x, y); (f ₀ , f ₁ )) × e ₂ ((x, y); (f ₀ , f ₂ ))
= E ₁₂ '((x, y); (2f ₀ , 0), (0,2f ₁ ), (0,2f ₂ ))
Thus, it can be understood that signal multiplication has signal components of frequencies (2f ₀ , 0), (0,2f ₁ ), and (0,2f ₂ ).

  That is, the signal generated by the multiplication operation is a basebanded signal (a signal in a band including a direct current in at least one direction) for each linearly superimposed signal (a signal corresponding to a crossed wave), When the wave has a plurality of signal components having different frequencies, the band is broadened in the direction having the plurality of different frequency signal components compared to the wave received when non-linear operation is not performed. The signal has at least one effect of higher frequency, higher spatial resolution, lower sidelobe, or higher contrast than the corresponding wave received when non-linear operation is not performed. A signal obtained by orthogonally detecting a harmonic signal in each direction or in a plurality of directions, and a wave can be imaged based on at least one of the signals. When crossed waves and beams have different frequencies or are not symmetrical with respect to the coordinate axis, the same processing can produce chords and difference sounds in a multidimensional space. Used for. They also work in situations where other parameters are different.

  In the three-dimensional space, the lateral modulation needs to generate at least three cross beams as described above. In this case, as a baseband signal obtained, only one arbitrary direction or two arbitrary A signal orthogonally detected in the direction is obtained. That is, the polarity of the frequency in the symmetric direction is opposite to the symmetric axis, so the sum becomes zero. All waves and beams may be generated symmetrically with respect to the coordinate axis, but this is not a limitation. Also, the frequency and other parameters may be different.

  In addition to the case where the propagation direction and steering angle of each beam and wave are different as in the above cross beam, other parameters are different, for example, frequency, carrier frequency, pulse shape, beam shape, frequency seen in each direction. Or the carrier frequency or bandwidth may be different. Also, in the case of transverse modulation, unlike the case of generating two or three intersecting waves or beams in the two-dimensional case (sometimes three), in each dimension. More waves or beams may be used. In particular, when a plane wave, a cylindrical wave, or a spherical wave is transmitted, high-speed transmission / reception is possible, and even when a plurality of waves are used like that, it is faster than beam forming in normal imaging. In addition, even when focusing beams are used, it is possible to apply high-speed beam forming using fast Fourier transform to the received signals that have been superimposed. (As described above, interpolation approximation may be performed in wave number matching as described above). In order to stabilize nonlinear processing, it is also effective to perform transmission / reception multiple times with the same parameters and to superimpose them (addition average). The same processing can be applied to signals received when so-called pulse inversion transmission is performed, and harmonics obtained by superposition of received signals at the time of pulse transmission with different polarities It is possible to perform the same processing on the image and perform the same processing before superposition. When these superpositions (that is, addition) are performed, a harmonic having a frequency that is an even multiple of the fundamental frequency is obtained, but when subtraction is performed instead of addition, a harmonic that is an odd multiple is obtained. It is also important to use them for imaging (a third harmonic is mainly obtained by simple subtraction of the received signal of pulse inversion). When superimposition of harmonic signals is obtained using the present invention for a signal whose bandwidth is limited by applying transducer or analog or digital filter at the time of reception, filtering (analog or digital) ), Or by performing signal processing (analog or digital) with various superpositions and fundamental waves, harmonics can be separated. Further, instead of pulse inversion, a signal having a phase difference other than 180 ° may be transmitted, but this can also be applied to such a case. In other words, even in a beam or wave having at least one of different parameters, the same non-linear effect can be obtained in an overlapped state, a separated state, a non-overlapped state, etc., and is used effectively. Sometimes. Through theory or calculation, it can be understood that waves and beams generated by nonlinear effects as well as linear effects can be designed (wave and beam parameters such as propagation direction) and controlled.

  The harmonic signals, chords, difference tones, overtones, and the like generated by these non-linear operations have the above characteristics and improve the image quality of echo imaging. There is no attenuation effect that occurs in normal harmonic imaging. The present invention is also effective for interpreting a physically generated nonlinear signal that virtually generates a nonlinear component at each position. The present invention is also effective when it is weak and cannot be observed. Furthermore, in displacement measurement, higher frequencies are welcomed, and phase rotation is faster, which is expected to enable high-accuracy measurement. However, in the phantom experiment shown below, the spatial resolution is high. When high spatial resolution was measured as it was, there was a tendency for noise to increase.

  In such a case, regularization (see, for example, non-patent document 18), the weighted least square method or the average processing through the above-described statistical evaluation, and the like are effective. For example, two signals of second harmonics detected in different directions obtained in <2> and <3> should be used for displacement measurement in each direction using the normal unidirectional displacement measurement method. Can do. In order to measure displacements or displacement vectors that occur between different time phases, for a signal that has a carrier frequency only in one arbitrary direction, the instantaneous phase change that occurred between the time points at each point of interest is the instantaneous frequency and centroid frequency. Alternatively, the displacement in that direction can be measured by dividing by the nominal frequency or the like, and further, the displacement vector can be synthesized based on the measurements in different directions. In the past, although it requires a calculation amount compared with the multidimensional autocorrelation method (see Non-Patent Document 13), in order to realize displacement vector measurement using a normal unidirectional displacement measurement method, digital of a lateral modulation echo signal A demodulation method was devised and reported (calculating the product and conjugate product of analytic signals: see Non-Patent Document 30 etc.). According to the present invention, a lateral modulation echo signal can be demodulated with a small amount of memory and a calculation amount in each stage, and the obtained signal is a harmonic signal. In addition, the noise can be averaged after the received raw signal or the non-linear processing after reception when a plurality of the same waves can be obtained in the same condition, and the received raw signal or It is effective to reduce by performing integration processing after performing nonlinear processing after reception. Further, a square norm or inner product can be calculated instead of the power or multiplication, and in that case, the spatial resolution is determined by the signal length at the time of the calculation. These methods may be effective in imaging other than displacement measurement.

The digital demodulation method described in Non-Patent Document 30 invented by the present inventor specifically derives a phase determined only by a displacement component in each direction and obtains a displacement component in each direction. As shown below, for example, when measuring a two-dimensional displacement vector (dx, dy), the instantaneous phase difference between two different phases in a two-dimensional region of interest is generated by two cross beams or waves. Are represented as the phases of the complex autocorrelation signals exp [j (fxdx + fydy)] and exp [j (fxdx-fydy)] using two independent single quadrant spectra Exp [j (2fxdx)] and exp [j (2fydy)] are obtained by calculating the product or conjugate product, and the instantaneous phase differences 2fxdx and 2fydy in each direction are obtained by the instantaneous frequencies 2fx and 2fy in each direction. By dividing, the unknown displacement vector (dx, dy) is obtained. When measuring a three-dimensional displacement vector (dx, dy, dz), exp [j (fxdx + fydy + fzdz)], exp [j () of complex autocorrelation signals obtained from four or at least three cross beams or waves. fxdx + fydy−fzdz)], exp [j (fxdx−fydy + fzdz)], exp [j (fxdx−fydy−fzdz)], or at least three of them can be easily obtained in the same manner. . This digital demodulation method or the non-linear calculation of <2> or <3> has a carrier frequency in each direction of the symmetry axis of an arbitrary wave crossing an arbitrary direction and the direction orthogonal thereto. Since it generates waves (waves detected in one direction or two directions), avoid the location where obstacles or shields related to those waves exist, and cross the waves in that way behind it Can generate a wave with a carrier frequency in an arbitrary direction that cannot be generated directly via an obstacle or shielding object behind the obstacle or shielding object. Imaging and displacement measurement behind can be performed. For example, when a wave having a carrier frequency in the depth direction and the lateral direction is generated via an obstacle or a shield, this is equivalent to realizing a situation where the obstacle or the shield is watermarked from the front. Yes, and in that case, the movement of the target in any direction can be measured. This imaging and displacement measurement can be performed not only from the front direction of an obstacle or a shield, but also from an arbitrary direction. In those cases, at least one mirror may be used to generate a reflected wave and observe the back of an obstacle or a shield. For example, a wave that is steered from the front direction such as an obstacle or a shield is generated, reflected by a mirror in the steered direction, and the wave may cross behind the obstacle or the shield, There may be a wave source in a direction other than the front direction. Although the steering angle and the carrier frequency can be used in various combinations, considering that it is necessary to obtain the effect of complex products and complex conjugates, the method for solving simultaneous equations is not restricted in terms of the combination and the amount of calculation is small.
In these digital demodulation methods or <2> or <3> non-linear calculation, a frequency twice as large as the instantaneous frequency in each direction is generated, so that the bandwidth is widened in advance based on the Nyquist theorem. Therefore, it is necessary to perform beam forming, perform interpolation of the number of beams in space, or perform widening (data interpolation) by zero-filling a spectrum other than the signal spectrum in the frequency domain. That is, the folding phenomenon may be prevented from occurring. These processes are also a kind of signal separation. Alternatively, when aliasing occurs in these digital demodulation methods or <2> or <3> nonlinear calculations, the Nyquist theorem can be applied to the signal before processing without widening the band. In the satisfied situation, each of these processes is performed in the same way, and the instantaneous phase difference in each direction calculated in that case is 2fxdx, 2fydy, 2fzdz, whereas the instantaneous frequency fx, fy in each direction , Fz can be found in the original signal, and they can be doubled to remove their instantaneous phase difference. There is an effect that the processing for widening the bandwidth is not required, the calculation amount is small, the speed is high, and the memory is small. Note that the sum of the instantaneous frequencies in each direction estimated for each wave or each beam may be used instead of twice the above instantaneous frequency. In those cases, instead of the instantaneous frequency, the center of gravity (the center of gravity frequency or the center frequency) of the spectrum of the original signal may be obtained and a double value or a sum may be obtained and used. Alternatively, a double value such as a nominal frequency or a typical value obtained in advance may be used without obtaining it by calculation. Further, as shown in the schematic diagrams of the spectral distributions of FIGS. 43 and 44, in the situation where the aliasing phenomenon occurs, the frequency region of the frequency coordinate where the aliasing phenomenon occurs is changed to the positive or negative half-band frequency region. It is also possible to directly calculate the double frequency from the centroid of the spectrum (because the Nyquist theorem is satisfied for the signal before processing, it can always be calculated). The spectral distribution may be calculated for the region of interest or an echo signal within a region, or may be calculated for a local region echo signal that includes each point of interest by looking at the point of interest. FIG. 43 shows an example in which the frequency coordinate axis is read and processed when a folding phenomenon occurs in the two-dimensional spectrum of the band 2A (−A to A) in the depth direction due to the demodulation during two-dimensional lateral modulation. Show. FIG. 44 shows an example in which the frequency coordinate axis is read and processed when a folding phenomenon occurs in the two-dimensional spectrum of the band 2B (−B to B) in the horizontal direction due to demodulation during two-dimensional horizontal modulation. Is shown. Although there are a plurality of combinations of independent analysis signals, FIG. 43 shows that the aliasing phenomenon occurred in the depth direction for two analysis signals whose instantaneous (center of gravity) frequencies are (fx, fy) and (fx, -fy). In this case, the center of gravity frequency in the depth direction can be calculated as 2fx. Further, FIG. 44 shows that when the aliasing phenomenon occurs in the horizontal direction with respect to two analysis signals whose instantaneous (centroid) frequencies are (fx, fy) and (fx, −fy), the horizontal center-of-gravity frequency is 2fy. An example that can be calculated is shown. A folding phenomenon may occur simultaneously in the depth direction and the lateral direction. Similarly, in the case of the three-dimensional case, the frequency region of the frequency coordinate where the aliasing phenomenon occurs may be read as a positive or negative half-band frequency region, and the double frequency may be calculated directly from the center of gravity of the spectrum. Similarly, in the situation where the aliasing phenomenon occurs, the frequency region of the frequency coordinate where the aliasing phenomenon occurs is similarly read as the positive or negative halfband frequency region, and then the half spectrum frequency region of the zero spectrum is added. The analysis signal can be obtained by the inverse Fourier transform of the broadband to satisfy the Nyquist theorem (at this timing, the change in instantaneous frequency and instantaneous phase can be calculated by widening the band and interpolating the signal. The amount of calculation can be reduced as compared with the case where the bandwidth is broadened or interpolated in advance, but the amount of computation is large compared to those processes that do not have a bandwidth). Of course, if no aliasing occurs in these digital demodulation methods or <2> or <3> non-linear calculations, the instant of double or sum that can be obtained directly without re-reading frequency coordinates or widening the bandwidth. What is necessary is just to remove | eliminate the difference of those instantaneous phases using a frequency or a gravity center frequency. Moreover, you may use a double value, such as a nominal frequency and the typical value calculated | required previously, without calculating and calculating | requiring. There is no problem in the range until the frequency coordinate is read, but if the bandwidth is widened by zeroing the spectrum or interpolation processing, not only will the amount of calculation increase enormously, but the accuracy may decrease, and processing without widening the bandwidth It is useful also in these respects. When the bandwidth is increased and when the bandwidth is not increased, regularization processing may be performed as necessary.

  In the above, some examples in which the present invention is applied to ultrasonic imaging or ultrasonic measurement have been presented. When the band of the signal component calculated and generated by the present invention overlaps with the band of other signals, the two cannot be separated in the frequency domain. In that case, the pulse inversion method or multi-dimensional term separation is used, but the inventor of the present application has reported in the past that the spectrum in the superimposed state is handled or divided and processed ( (Refer nonpatent literature 30). In the present invention, as another method for accurately separating the waves, including the case where the spectra are superimposed, in order to obtain the effect of separating them in the frequency space, a nonlinear process is applied to the superimposed waves. In a situation where a multiplication operation is performed and the band is widened and expressed as a harmonic, the frequency space may be separated. Conversely, a high frequency signal may be displayed at a low frequency or a wideband signal may be displayed in a narrow band. Perform high-frequency and wide-band processing (when the order is greater than 1), or low-frequency and narrow-band processing (when the order is less than 1), and perform high-precision in the frequency domain. May be. The propagation direction of the wave is the centroid of the generated harmonic spectrum (local direction, i.e., spatial resolution, or macroscopic low spatial resolution, or no), or the instantaneous frequency ( There is a spatial resolution) and can be calculated. Using the power of the power performed, other wave parameters such as the frequency and bandwidth of the original wave can be obtained by reverse calculation and restored in a separated situation (the power of the power using the restoration of the signal after separation) It is easy to raise to the reciprocal of. Including such cases, the signal source position and direction of arrival, the intensity of the signal source, and the size and distribution of the signal source can be measured with high accuracy. In addition, when a signal having a higher frequency than the original signal is generated, it is necessary to widen the bandwidth that can be calculated in advance before performing the calculation. Therefore, zero padding of the spectrum is effective without approximation (see Non-Patent Document 30), but the sampling interval may be shortened directly in space-time based on interpolation approximation.

  In recent years, it has become possible to simulate nonlinear propagation at low cost. Therefore, the nonlinear calculation of the present invention or such a simulation technique can be applied to an unbeamformed signal (plane wave or the like) or an aperture synthesis echo signal to generate a nonlinear signal. On the basis of these, it is also possible to analyze (inverse analysis) the actually measured nonlinear signal based on an inverse problem approach and apply it to tissue diagnosis.

  For example, in the case of targeting ultrasonic waves, it is applied to diagnosis by evaluating the tissue properties of a living body such as sound velocity, bulk modulus, acoustic impedance, reflection, Rayleigh scattering, backscattering, multiple scattering, or attenuation. Sometimes. For other waves, the inverse analysis of related phenomena and physical property values is effective (Mie scattering in light, scattering in radiation, Compton scattering, etc.).

  In addition, in the treatment by heating and heating, it is necessary to clarify the heat receiving characteristics (for example, the characteristics with respect to the sound pressure of high-intensity ultrasonic waves and the effect of contrast medium) and the characteristics of temperature rise. However, even in such cases, calculations including nonlinear calculations are effective. In the treatment, it is useful to evaluate and apply the effect based on the imaging of the non-linear effect according to the present invention. As another example, echo imaging and tissue displacement measurement can be performed on a received signal that has been subjected to a physically nonlinear effect, a separated baseband signal, and a plurality of harmonics using the present invention.

  In addition to ultrasonic waves, the present invention applies non-linear operations such as multiplication and power to electromagnetic waves, light, radiation, dynamic vibration, sound waves other than ultrasonic waves, and coherent signals of arbitrary waves such as heat waves. The present invention relates to an imaging apparatus that increases the frequency, bandwidth, or contrast of a signal. According to the present invention, the harmonic signal can be enhanced, simulated, or newly generated. Furthermore, a harmonic signal can be virtually realized.

  In addition, it is possible to simultaneously obtain a baseband signal and a detection signal in an arbitrary direction of a harmonic signal with a small amount of calculation compared to a normal detection process. As a result, for example, high frequency and wide band, high contrast, or sidelobe suppression can be achieved, and non-linear imaging with high S / N ratio becomes possible. Further, the displacement vector can be easily measured with a small amount of calculation by using a normal one-direction displacement measuring method. From the viewpoint of generating chords, difference tones, harmonics, etc., high-frequency signals and low-frequency signals can be obtained, including when the wave and beam frequencies, carrier frequency, steering direction, or propagation direction are different. They are sometimes used effectively for imaging and measurement. Through theory or calculation, it is possible to design waves and beams generated not only by linear effects but also by nonlinear effects (wave and beam parameters such as propagation directions) and control them.

  On the other hand, in the field of image measurement, using a signal (result display is an image) made incoherent by applying various types of detection to the coherent signal (including those that simply take the absolute value of the waveform) It is well known that observations are made. A cross-correlation process, an optical flow, or a method according to the SAD (Sum and Difference) method may be used. Moreover, even if the present invention is applied to an incoherent signal, it is possible to increase the bandwidth (high resolution). The high-resolution detection signal obtained by the present invention can also be used. The situation where the data density is increased due to the increased bandwidth is suitable for such processing, and the motion measurement accuracy is also improved. Note that the above method can also be applied to coherent signals, and the wide band is effective for improving accuracy. That is, the present invention can be applied to arbitrary coherent signals and incoherent signals.

  In addition, according to the present invention, heating, heating, cooling, freezing, welding, repairing, cancer in medical treatment of any object performed using waves (laser, ultrasonic waves, focused intense ultrasonic waves, etc.) In heating, freezing treatment of lesions, etc., or cleaning of an arbitrary object (glasses, etc.), the effect is enhanced through a non-linear phenomenon, the resolution is increased, and the effect is predicted (for example, overpowering) The effect can be improved not only by the power effect during heating using sound waves, but also by the multiplication effect as well as the addition in the case of enhancing the effect by using cross beams.

  In heat treatment using intense ultrasonic waves, harmonics are generated by the non-linear effect of the tissue, and because of its high frequency, its absorption effect as thermal energy is strong, so it is easy to understand and predict heat generation in the tissue. It is also possible to do. From this point of view, transmitting high-frequency signals, transmitting broadband signals, transmitting harmonics, generating superimposed beams, or generating crossed beams are effective for treatment. Yes, it is easy to understand and predict. Specifically, in a system that can simulate a sound field or obtain a received signal, it is possible to estimate a sound pressure shape and a point spread function based on evaluating an autocorrelation function, In particular, it is possible to evaluate the harmonic signal, and it is also effective to perform a nonlinear operation on the fundamental wave signal. The same applies to other waves.

  In addition, the present invention obtains a nonlinear effect under physical conditions in which a nonlinear effect cannot be physically obtained (for example, when the strength cannot be increased with respect to a measurement target or when a high strength cannot be obtained due to a high frequency). Also effective. Conversely, for example, the present invention can be implemented under conditions in which a nonlinear effect is enhanced by using a contrast agent such as microbubbles during ultrasonic echo imaging, displacement measurement, or treatment. Although the tissue may be targeted in a state where it has permeated the tissue, it is also suitable for measurement and imaging for blood in blood vessels and heart chambers. That is, the present invention can enhance the nonlinear effect, can be simulated, or can be newly generated. Furthermore, the present invention can virtually realize the nonlinear effect. As described above, it is also possible to evaluate non-linear effects. Contrast agents may be used to enhance the effects of heat treatment. The same applies to other waves.

  In addition, when generating a high-frequency signal that cannot be realized with a single signal source, higher-resolution imaging and high-precision Doppler measurement are possible. Usually, the influence of attenuation is strong against high-frequency components. For example, in a microscope that is susceptible to the influence of attenuation, it is desirable to observe as deep as possible at a high frequency. For example, when a plurality of 100 MHz ultrasonic transducers are used, it is possible to physically generate ultrasonic waves that are several times as high as that number, and realize high frequencies that cannot be generated by ordinary transducers. In addition, simply a high frequency signal (chord) can be generated. According to the present invention, such a high frequency can also be realized by calculation. Therefore, according to the present invention, it is possible to generate high-frequency waves and signals that cannot be physically realized. Similarly, low-frequency imaging and measurement using a low-frequency signal (for example, difference sound) can be realized. It is also possible to generate a low-frequency signal that cannot be physically realized with a single signal source. These signals can be realized theoretically or on the basis of computation to control the generated waves.

  In the following, in order to prove the effect of the present invention, experimental data, simulation results, and materials such as photographs will be described. These demonstrate the effectiveness of the present invention by performing ultrasonic echo imaging and measurement imaging through an ultrasonic simulation and an agar phantom experiment. The present invention can be applied to any signal other than the ultrasonic echo method (familiar, laser, light wave, OCT, electricity, magnetic field signal, radiation such as X-ray, and heat wave) and between different signals. It is. This is applied in raw coherent signals or incoherent signals after signal processing.

  Front-facing beamforming and lateral modulation of 3.5 MHz laterally for echo data (linear array probe, 7.5 MHz) for aperture surface synthesis of an agar phantom disclosed in Non-Patent Document 30 The processes <1> to <3> were performed using the respective echo signals when performing the above.

  FIG. 45 is a diagram showing changes in the spectrum of an echo signal according to an embodiment of the present invention. In FIG. 45, the horizontal axis indicates the horizontal frequency [MHz], and the vertical axis indicates the depth direction frequency [MHz]. 45, (a1) and (a2) show the spectrum of the original echo signal and the spectrum of the square of the echo signal, respectively, when there is no steering. (B1), (b2), and (b3) show the spectrum of the original echo signal, the spectrum of the square of the one-way steering echo signal, and the spectrum of the square of the transverse modulation echo signal in the lateral modulation. Each is shown. (C) shows the product spectrum of the crossed steering beam echo signal. From FIG. 45, the spectrum of each signal derived by the above theory can be confirmed. In any echo signal, as a result of squaring or multiplication, a spectrum of the second harmonic is generated, and its bandwidth is wider than the original spectrum.

  46A to 46C are diagrams illustrating changes in an autocorrelation function of an echo signal according to an embodiment of the present invention. Here, the horizontal axis indicates the horizontal position [mm], and the vertical axis indicates the normalized autocorrelation function. FIG. 46A shows a comparison between the autocorrelation function of the original echo signal and the autocorrelation function of the second harmonic by the square of the echo signal without steering. FIG. 46B shows a comparison between the autocorrelation function of the original transverse modulation echo signal and the second harmonic autocorrelation function based on the square of the transverse modulation echo signal during lateral modulation. FIG. 46C shows the autocorrelation function of the transverse component and the depth component for the product of the cross beam echo signal and the square of the transverse modulation echo signal. Based on the autocorrelation function, the lateral profile of the sound pressure and the point spread function can be evaluated (in the case of a center depth of interest of 19.1 mm). Although omitted here, if a two-dimensional autocorrelation function is obtained for this two-dimensional echo signal, a two-dimensional distribution of sound pressure and point spread function can be estimated, and a three-dimensional autocorrelation for a three-dimensional echo. Find the function.

  47 to 49 are diagrams showing changes in the B-mode echo image according to the embodiment of the present invention. The depth of these echo images is 10.0 mm to 28.1 mm, and the lateral width is 20.7 mm. In the agar phantom, there is a claw having a columnar shape (diameter 10 mm) whose shear modulus is about 3.29 times higher than that of the surrounding, centering on a depth of 19 mm.

  47 to 49, (a1), (a2), and (a3) are the echo image based on the original echo signal, the echo image based on the basebanded signal, and the echo signal in the case without steering. The echo images based on the second harmonic by the square are respectively shown. When there are two images on the left and right, the left image is based on envelope detection, and the right image is based on square detection.

  (B1), (b2), (b3), (b4), and (b5) are an echo image based on an original laterally modulated echo signal, an echo image based on a basebanded signal, An echo image based on the second harmonic by the square of the directionally modulated echo signal, an echo image based on the lateral component of the second harmonic by the square of the laterally modulated echo signal, and a second by the square of the laterally modulated echo signal Each echo image based on the depth direction component of the second harmonic is shown.

  Further, (c1) and (c2) respectively show an echo image based on the lateral direction component and an echo image based on the depth direction component for the second harmonic due to the product of the cross beam echo signals. In the case where a plurality of waves exist, detection of superposition of coherent signals has been reported in the past, but here, the result of superposition of the respective detection signals is shown.

  It can be confirmed from FIG. 46A to FIG. 46C and FIG. 47 to FIG. 49 that the spatial resolution has increased in response to the broadening of the spectrum shown in FIG. Here, the DC of the basebanded data is not cut off. If the direct current or, if necessary, the extremely low frequency spectrum in the depth direction or the horizontal direction is removed by filtering or the like, the high or low luminance lines (vertical stripes) that run in the vertical direction can be completely removed (illustrated). Is omitted). From FIG. 46A to FIG. 46C, it can be confirmed that the side lobe is lowered. Corresponding to these, the effect of increasing the contrast can also be confirmed from FIGS. Since the original echo signal is not corrected for attenuation, the image obtained from the processed signal has a shallower signal intensity at a deeper position than the original signal image as a result of increased contrast due to the uncorrected signal. Extremely low compared to that of the position.

  In imaging using the original signal, correction of attenuation in the so-called wave propagation process is performed on the coherent signal or the incoherent signal after detection. In this apparatus, the original coherent signal is corrected in advance. Then, the coherent signal is subjected to nonlinear processing, or the coherent signal or incoherent signal is corrected after the nonlinear processing. The correction process itself may be performed mainly on the basis of signal strength, before or after reception beamforming, or after imaging, as in normal correction. Corrections may be made according to Lambert's law.

  In this case, an average attenuation coefficient may be used, but the attenuation coefficient at each position on the wave or beam path is calculated by signal processing or inverse analysis in the calculation unit 130, and correction is performed with high accuracy. Sometimes implemented. That is, it may be performed adaptively or automatically. Alternatively, the operator may adjust the intensity within a predetermined range at each depth via the control unit 133 while viewing the generated image. Depending on the measurement target, a selectable pattern may be prepared.

  Gain adjustment is performed by an amplifier or attenuator in the receiver 122, the filter / gain adjustment unit 123 or 125, an amplifier or attenuator or digital processing in the reception beamformer 129, or an analog processing or digital processing in the arithmetic unit 130. Is called. In the transmitter 121, the intensity of the transmitted beam or wave may be adjusted. In addition, an amplifier or an attenuator may be used as the action device 112 to adjust the intensity of the wave itself. Since the contrast agent 1a has a great influence on the determination thereof, attention is required.

  In the square calculation (<2>) of the lateral modulation echo signal in the above experiment, the spectrum and the second harmonic detected in the lateral direction of the two signals of the second harmonic detected in different one directions Since the waves overlapped, the inventor divided the spectrum with a glance. The result was compared with the result of multiplication (<3>) of two waves of the laterally modulated echo signal in the autocorrelation function (see FIG. 46C), except that the harmonic frequency was slightly lowered. There was no difference.

  In addition to these experiments, displacement vector measurement, strain tensor measurement, and shear modulus reconstruction were performed using the multidimensional autocorrelation method. As a result, FIG. 50 shows a result of displacement measurement in each direction using two of the second harmonic signals detected in only one different direction in <3>.

FIG. 50 is a diagram illustrating an image of a displacement vector, a strain tensor, and a relative shear modulus measured in an agar phantom according to an embodiment of the present invention. In part of FIG. 50, the average value and the variation (in parentheses) evaluated at the center of the nail are also shown. There was a tendency for noise to increase compared to the result of digital demodulation of the laterally modulated echo data (distortion variation in the lateral direction (y) was 3.08 × 10 ⁻³ to 9.52 × 10 9 ³ ), the spatial resolution is doubled, and the result of regularizing the shear modulus reconstruction is improved (improved from 3.37 to 3.23).

  Although the results are omitted here, as described in paragraph 0655, many waves and beams are generated and nonlinear processing is performed in a superimposed state, or nonlinear processing is performed in a non-superposed state. May be overlapped after applying. In addition, as described elsewhere, nonlinear processing may be performed on a raw reception signal that has not been subjected to beamforming (for example, only transmission beamforming or aperture surface synthesis). A plurality of waves or beams generated under the same wave and beam forming parameters may be processed, but waves or beams generated under different parameters may be processed.

For high resolution, super-resolution in the above linear model is effective, and such super-resolution may be used for such a plurality of waves and beams. That is, individual waves or beams that are not superimposed may be super-resolved and superimposed, or super-resolution may be performed in a superposed state. In some cases, both are mixed and processed. There are cases where noise is reduced by superposition (addition averaging) under the same parameters. A remarkably high spatial resolution can be realized with respect to the original signal (including the case of a harmonic). Various super-resolutions have been described. For example, as described in paragraph 0363, in the case where inverse filtering is performed using a spectrum of a signal distribution such as a desired point spread function or echo distribution as described in paragraphs 0390-0415, As described together with the displacement measurement, the Wiener filter can be applied and weighted for imaging of the signal itself. Among them, for example, the Wiener filter used in the equations (A12 ′) and (A13 ′) is used. When using the basic weight (excluding the square norm of the first signal spectrum), the inverse filter
However, each of Hp (ωx, ωy, ωz) and G (ωx, ωy, ωz) is a spectrum of a signal to be processed and a target signal.
Weighted to the norm of
However, PWpn (ωx, ωy, ωz) and PWps (ωx, ωy, ωz) are the power spectrum of noise and signal, respectively. q is an arbitrary positive value.
It is sufficient to process using Similarly, in other super-resolutions in the linear model described above, it is possible to suppress noise amplification by applying a Wiener filter. When the norm of (AA1) is applied without using the Wiener filter, ε (<1) times the norm (maximum norm, L ₂ norm, L ₁ norm, etc.) of the signal spectrum Hp (ωx, ωy, ωz) Only the spectrum of the frequency having the above spectrum may be processed (the spectrum of other frequencies is set to zero). In these, irregularly, (AA1) itself may be used instead of the norm of (AA1), and the phase may be matched. In that case, Gp (ωx, ωy, ωz) often has phase information to be measured.
In addition, these weighting processes may be performed in blind deconvolution. In addition, including the case of whitening by inverse filtering using a separately obtained point spread function or system transfer function, the case of multiplying the conjugate of the point spread function or system transfer function, or the conjugate of equation (AA1), These weighting processes are useful even when they are implemented before or after beam forming (a state in which only transmission beam forming is performed or a received signal obtained for aperture plane synthesis). In particular, regularization may be performed in inverse filtering. Further, it may be performed based on maximum likelihood estimation (with or without MAP).

  The nonlinear processing described above may be performed on a signal subjected to super-resolution under such a linear model. Furthermore, the resolution is increased, and the contrast can be increased. As a result of the super-resolution obtained under the linear model, the original (including the case where it is a harmonic, the same applies hereinafter) super-resolved signals, and those super-resolved signals are A plurality of objects that are superposed, a plurality of originals that are super-resolved, a thing that is processed by mixing them, and the like are processed. There are also cases where there are a plurality of original signals, each of which is super-resolved under a linear model and subjected to non-linear processing and superimposed. They may be mixed and processed.

  Further, as described above, super-resolution performed by a linear model may be performed on a non-linearly processed signal. Although the resolution is increased, the contrast may be lowered. As a result of super-resolution obtained by nonlinear processing, the original (including harmonics) signals are super-resolved, and there are multiple super-resolved signals that are superposed. What is processed, what is super-resolved by superimposing a plurality of originals, what is processed by mixing them, and the like are processed. In addition, there are a plurality of original signals, each of which is super-resolved by non-linear processing, and super-resolution performed by a linear model is performed on each of the signals to be superimposed. They may be mixed and processed.

It should be noted that when the nonlinear processing is applied to a plurality of signals (a signal representing a beam or a wave, which is not limited to a fundamental wave but may be a harmonic) at the same position of interest, If the intensity of the original signal itself before processing differs due to the effects of scattering and attenuation (including frequency-dependent cases) in the target, the difference may be emphasized, especially high-order harmonics. When generated, it may become noticeable. This difference may be positively imaged or may be quantitatively confirmed in the spectrum image (there may be confirmed by enhancing their frequency characteristics). On the other hand, in order to reduce the difference and perform imaging, imaging may be performed by weighting the signal energy or the spectrum of a specific frequency before or after nonlinear processing. These multiple signals may be superimposed and imaged. The spectrum or energy of the signal may be evaluated in a local region including the position of interest, or may be evaluated in the entire region of interest. Needless to say, weighting may be performed in the same manner during the linear superimposition process, regardless of whether or not the nonlinear process is performed.
Further, the signal intensity is weak in the distance direction due to the attenuation of the propagation process and the influence of reflection / scattering. For example, the degree of attenuation of the plane wave is weaker than that at the time of focusing. When nonlinear processing is performed, the higher the order, the more the effect is emphasized. Therefore, as described above, the signal strength may be corrected before or after the nonlinear processing (the correction may be performed even when the nonlinear processing is not performed). It is processed before or after detection.
There are various other types of super-resolution, and at least one of them may be used in combination, applied to the same or different signals, coherently added, and used. As described above, it may be applied to the superimposed signals. In addition, they may be added incoherently, and speckle may be reduced. Incoherent addition through super-resolution may not reduce the spatial resolution as described above.
In each of these super-resolution processes, addition may be performed spatially non-uniformly depending on the signal strength, the SN ratio, and the spatial resolution. That is, the parameters of each method may be variable depending on those at each position. When the spectrum is processed, it is as described above. For example, in the case of nonlinear processing, the order of the power, the number of multiplications, and the like. In addition, when addition of a coherent signal or an incoherent signal is performed, an addition number, a weighting value, or the like is used. Of course, it may be processed spatially uniformly.
In addition, as an effect of increasing the contrast by non-linear processing, scatterers and reflectors in the tissue may be noticeably well visualized. When the power order and the number of multiplications are increased, the signal intensity (a gray image is obtained). In some cases, an effect that the difference in the level of the brightness) becomes significant is obtained. For example, it may be easier to capture calcification after necrosis of biological tissue. In addition, for example, coloring may be performed depending on the signal intensity, and the image may be superimposed and displayed on a normal gray image, Doppler image, power Doppler image, or contrast image. Processing may be performed after the intensity of the signal distribution is corrected. For example, nonlinear processing is performed after correction to make the intensity of the signal received from within the region of interest (before or after detection) spatially uniform, and the scattering intensity distribution, the scattering intensity of a plurality of scatterers, or the reflection intensity distribution The level of reflection intensity of a plurality of reflectors may be visualized. Processing may be performed for the purpose of counting the number of reflectors and scatterers. When plane waves, spherical waves, or cylindrical waves are used in addition to the focus beam and aperture synthesis, the spatial resolution is low, and even in such cases, various super-resolutions including nonlinear processing are useful. In particular, when nonlinear processing is performed, scattered waves and reflected waves may be remarkably visualized at the generation position. For example, when these cross waves are generated, a cross-shaped waveform is highlighted and displayed at the scatterer position as a scattered wave.

  In addition, when a concave aperture HIFU applicator (simulation, frequency 5 MHz, aperture diameter 12 mm, focal depth 30 mm) is used (single aperture and two apertures are used), the power or multiplication of the point spread function is calculated. . As described above, this type of calculation is effective for considering the heating effect. By collecting experimental data, it is possible to formulate the relationship between sound pressure (point spread function), harmonic sound pressure, heat reception, etc. Design of applicator and radiation sound pressure (ultrasonic parameters), etc. Can be used to improve the efficiency of heat treatment. The same applies when other waves are used.

FIG. 51 is a diagram showing a change in sound pressure according to an embodiment of the present invention when a concave HIFU applicator is used. 51, (a1) and (a2) are images of the sound pressure by the original signal and the sound pressure of the square signal (left includes DC, right only harmonics) when one aperture is used. The image is shown. (B1) and (b2) are images of the sound pressure of the original signal and the sound pressure of the multiplication signal (left is direct current) when two openings are used (the crossing angle is ± 5 ° with respect to the horizontal direction). , And the right shows only the harmonics). The image is obtained by envelope detection, and the image size is 3.8 × 12.8 mm ² . It can be confirmed that in the second harmonic component obtained by each of the square and multiplication, the sound pressure is concentrated in a desired region and the contrast is high. In this way, it is possible to estimate the intensity of the fundamental wave (Intensity, ie, power) and the sound pressure distribution shape of the generated harmonics (second and higher harmonics). In addition, the power consumed by harmonics (Intensity) can also be evaluated. The same can be done for the actually observed harmonics.

  In the above, the imaging apparatus according to the embodiment of the present invention has been described mainly with respect to electromagnetic waves, vibrations including sound, thermal waves, or nonlinear arithmetic apparatuses for corresponding signals. Enhance the effect, simulate the non-linear effect, or virtually realize the non-linear effect (ie, unless the effect is physically, chemically, or biological) Including the case where it does not occur). In that case, the present invention can be implemented on the basis of signals received at different times if they are received simultaneously using devices related to the wave used, or if they are in the same phase. That is, the present invention can handle a case where a plurality of waves are generated simultaneously and a case where a wave is generated independently.

  In addition, in electromagnetic waves, vibrations, or heat, if the frequency is different, the dominant behavior differs depending on each measurement object (medium), and the name is obviously different (for example, regarding electromagnetic waves) As for vibrations such as radiation such as microwaves, terahertz waves, and X-rays, for example, in the case of human soft tissue, shear waves are not transmitted as waves due to the attenuation in the megahertz band, and ultrasonic waves are dominant. However, at low frequencies such as 100 Hz, the characteristics of incompressibility are strong and shear waves are dominant), and the present invention enhances the nonlinear effect between those different in such behavior, Can be simulated or realized virtually.

  In that case, the present invention can be implemented on the basis of signals received at different times if they are received simultaneously using devices related to the wave used, or if they are in the same phase. Of course, there is a limit that phenomena such as propagation speed, attenuation, scattering, and reflection of each wave have dispersion characteristics and should be used appropriately in consideration of the SN ratio of the received signal. However, the scope of application of the present invention is very wide, including the ability to generate high-frequency signals and low-frequency signals that cannot be physically generated or captured.

  In addition, it describes that non-linear calculation and nonlinear effects in the measurement object are imaged or applied to other measurements, and that harmonics may be actively propagated to the measurement object. In some cases, the fundamental wave is actively used together. An over-determined system can also be configured. The fundamental wave is processed in the same way as the harmonics.

  Further, arbitrary detection processing is performed on at least one of the plurality of signals obtained through the non-linear operation, or the plurality of signals that may include the fundamental wave are subjected to arbitrary detection processing and are superimposed, or In addition, an arbitrary detection process may be performed on a superposition of a plurality of signals that may include a fundamental wave as they are, and other measurements such as imaging or displacement may be performed. Regarding superposition, the former incoherent addition (incoherent compounding) is effective in reducing speckles, and the spatial resolution is not lowered when a high frequency signal is generated and used. Low spatial resolution often caused by normal speckle reduction is not a problem. When a low frequency signal is generated and used, it may be useful although the spatial resolution is reduced. On the other hand, the latter coherent addition (coherent compounding) can increase the bandwidth of the signal, that is, increase the spatial resolution. In particular, when a high frequency signal is generated and used, the frequency can be increased, and when a low frequency signal is generated and used, the frequency can be decreased. As a result, the imaging can have a high spatial resolution, and the displacement and other measurements can be made highly accurate. As described above, a signal obtained by generating a plurality of beams and waves or through spectrum frequency division is also included in these processing targets including nonlinear processing.

  The displacement measurement can be applied as described above, for example. The range of applications such as radar, sonar, and environmental measurement is immeasurable. In addition to displacement, for example, temperature may be measured. The temperature sensing may be performed directly using a temperature sensor, or the temperature dependence of wave propagation characteristics is detected. For example, when ultrasonic waves are used, the thermal velocity reflects changes in sound velocity and volume due to temperature changes. The temperature distribution may be measured based on signal processing for the purpose of strain measurement. The chemical shift of the nuclear magnetic resonance frequency may be detected based on signal processing. Thermal waves are observed, and it is possible to image the nonlinearity and to apply heat treatment with high efficiency.

  In addition, when actively observing the nonlinear effect in the measurement object and when the nonlinear processing according to the present invention is actively performed, both of them can be used by switching them, or both can be used simultaneously. In some cases, non-linear effects in the measurement object are clarified through simple calculations. That is, by using the nonlinearity of the signal source, the contrast agent, and the analog or digital nonlinear calculation to be used, the nonlinearity effect in the measurement object can be measured with high accuracy and imaged.

  The above imaging and measurement are based on performing appropriate beam forming, and an appropriate detection method and tissue displacement measurement method are also important. The inventor of the present application has used a lateral modulation method using a cross beam as a beam forming method, such as square detection as well as quadrature detection or envelope detection, in particular as a detection method of a multidimensional reception signal (Non-Patent Document 13). And 30), spectral frequency division (see Non-Patent Document 30), wave or beam shape adjustment by spectral filtering, method using many crossed beams, and over-determined system As a displacement vector measurement method, a multidimensional autocorrelation method, a multidimensional Doppler method, a multidimensional cross spectrum phase gradient method, a phase matching method, etc. (see Non-Patent Documents 13 and 30) are developed. In addition, (viscous) shear modulus distribution and thermophysical property distribution can be reconstructed and imaged based on displacement and strain measurement. In addition to the original wave and signal, multiple waves and signals are superimposed, or waves and beams generated by nonlinear effects (which may include pseudo) may be simulated in spectral frequency division. And a beam can be generated, and in the filtering of the spectrum, the wave and the shape of the beam can be adjusted.

  A signal obtained by superimposing a plurality of signals that may contain a fundamental wave, or a signal obtained by spectrally dividing or filtering at least one of a plurality of signals that may contain a fundamental wave in the frequency domain ( (See Non-Patent Document 30), or an original signal that has not been subjected to these processes, or an over-determined system using these signals in combination, and imaging can be performed by the above process. Alternatively, other measurements such as displacement may be performed.

  As described above, the present invention superimposes a non-linear response or wave to high intensity during wave propagation on a coherent signal obtained by detecting a transmitted wave, reflected wave, or scattered wave of an arbitrary wave with a sensor. Imaging using the original signal by obtaining non-linear effects (generation of harmonics, chords, difference tones, etc.) such as multiplication and power, for example, by performing analog computation or digital computation using a computer, for example Compared to the above, imaging with high frequency, wide bandwidth, high contrast, and high spatial resolution is realized. It is also possible to perform imaging with lower frequency instead of higher frequency. Also, under the same effect, displacement, velocity, acceleration, distortion, or distortion rate can be measured with higher spatial resolution and higher accuracy than Doppler measurement using the original signal.

  The wave superposition means what is physically realized during beam forming, or between beam-formed waves and non-beam-formed waves. When the wave intensity is weak, the superposition theory established by the linear rule is mainly observed. Waves, chords, and difference sounds) are observed, and the present invention focuses on this latter phenomenon. The present invention is also characterized in that it can be used for all of these wave components and superimposed waves without depending on their strength. Of course, the present invention also applies to a wave including a harmonic component artificially radiated with a fundamental wave or generated during propagation. Examples of harmonics generated during propagation include, for example, an ultrasonic harmonic signal.

  On the other hand, the present invention, for example, a beam generated by beam forming (physical or calculation based on apodization, delay processing, or addition processing), or a wave not subjected to beam forming. As for any wave such as itself (including plane wave and received signal group for aperture surface synthesis), transmitted wave, reflected wave, scattered wave, etc. Non-linear effects such as multiplication and power that occur when waves (the same wave of the same physical quantity differ only in direction, waves with different parameters of the same physical quantity, waves of different types of physical quantities) overlap, etc. can be measured with high accuracy In order to simulate, for example, after detecting a signal by a transducer, the signal is actively transmitted using an analog arithmetic unit or a digital arithmetic unit. To are those subjected to these operations, it is possible to obtain broadband and harmonic or chords, the difference tone. In addition to creating a nonlinear effect physically, chemically, or biologically, the effect may be emphasized or a nonlinear effect may be created when the nonlinear effect cannot be observed or does not occur. Is possible. In addition, a plurality of detection signals can be obtained simultaneously. In addition, the application of the basebanded signal generated by the physical action is also included in the present invention (the harmonics obtained by the pulse inversion method, the filtering method, etc. are removed from the received signal, or the above calculation is performed. And applying signals estimated by calculation).

  The inventor of the present application has disclosed a transverse modulation method using a cross wave (plane wave or the like) or a cross beam based on a linear rule in the past (having carrier frequencies in the depth direction and the horizontal direction). According to the invention, a power effect can be obtained even in this lateral modulation, and a multiplication effect between cross waves can be obtained. In general, power effects and product effects can be obtained by increasing the wave intensity. However, according to the present invention, these nonlinear effects can be obtained without depending on the intensity.

  In addition, according to the present invention, a basebanded signal can be obtained by a new detection process that can be easily performed with a small amount of calculation instead of normal quadrature detection or envelope detection, and its effect in echo imaging and Doppler measurement. Is obtained. However, the detection signal is different from the baseband signal as usual, and includes direct current, so it is used as it is, or is used after removing direct current by analog processing or digital processing. In addition, the application of a baseband signal obtained by receiving a physical action is also included in the present invention. A baseband signal generated by calculation is also called a baseband signal.

  For example, in the field of medical ultrasound and sonar, nonlinear phenomena in the propagation process of ultrasound in a living body (when the sound pressure is high, the volume elastic modulus acts high, so the sound speed is fast, the waveform is distorted, and the propagation process Although it is applied clinically as harmonic (harmonic) echo imaging caused by (accumulated in), it is not disclosed to apply a physically generated baseband signal. Application of a baseband signal that is physically generated by other nonlinear phenomena is not disclosed. Note that the baseband signal, basebanded signal, and incoherent signal such as envelope detection or square detection are also included in the processing target of the present invention.

  In particular, regarding the Doppler measurement, the inventor of the present application uses a multi-dimensional received signal, unlike normal Doppler measurement that measures the displacement in the wave propagation direction, the displacement vector in any direction, velocity vector, acceleration vector, The strain tensor or strain rate tensor can be measured with high accuracy. According to the present invention, unlike normal detection, a signal (basebanded signal) detected in any one direction from a multidimensional received signal can be obtained simultaneously, and using a normal one-direction displacement measurement method, It is also possible to easily measure them in a short time with a small amount of calculation. Even in this case, echo imaging using the harmonics obtained at the same time or the above baseband signal is possible. In addition, side lobe suppression and high contrast are possible. The temperature measurement is also performed as described above.

  Basically, multiplication between sine and cosine signals of different single frequencies produces chords and difference sounds, and when power calculation is performed, the frequency of the signal is doubled by the power of the power (by using only the double angle) In addition, a signal having a plurality of frequency components (distorted wave) is not only high-frequency but also wideband. In addition to this, an effect of suppressing the so-called side lobe is obtained, and the contrast is increased. These effects are often observed as propagation effects of particularly strong waves, but in the present invention, the nonlinear effect is enhanced by applying analog or digital arithmetic processing to arbitrary signals regardless of the intensity. Or simulated or newly generated. It can also be realized virtually. Not only in the case of having spatial resolution, but also in continuous waves, harmonics and detection signals can be obtained physically or artificially. If a physically generated baseband signal can be understood under the present invention, its application will also be engineeringly useful. For example, displacement and displacement vector components can be measured (a normal one-dimensional displacement measurement method can be used). It is also possible to measure displacement and displacement vector components using the observed harmonics (you can use the various multidimensional displacement vector measurement methods described above), or configure an over-determined system. As in the case of using the nonlinear processing of the present invention, it can be applied to imaging (high signal-to-noise ratio, high resolution, speckle reduction, etc.), displacement component measurement (high accuracy), and the like. In these cases, it is also effective to enhance the nonlinear effect by actively applying the contrast agent.

  In addition, the present invention relates to heating, heating, cooling, freezing, welding, repairing of cancerous lesions in medical treatment, etc. of any object performed using waves (laser, ultrasonic waves, focused intense ultrasonic waves, etc.) , Cryotherapy, or cleaning of an arbitrary target (glasses etc.), etc., to enhance the effect through a non-linear phenomenon, to increase the resolution, and to predict the effect (for example, using high intensity ultrasound) The effect is improved not only by the power effect during heating, but also by high frequency and high spatial resolution as the effects of multiplication as well as high spatial resolution by addition when enhancing the effect by using crossed beams) It becomes possible. In these cases, a continuous wave may be used, and the same effect can be obtained.

  The present invention is also capable of obtaining a nonlinear effect under physical conditions in which a nonlinear effect cannot be physically obtained (for example, when the strength cannot be increased with respect to a measurement target or when a high strength cannot be obtained due to high frequencies). While effective, conversely, for example, the present invention is implemented under conditions in which nonlinear effects are enhanced by using contrast agents such as microbubbles during ultrasound echo imaging, displacement measurement, temperature measurement, or treatment. It is also effective. That is, the present invention can enhance the nonlinear effect, but it can also be simulated, newly generated, or virtually realized. The present invention can also be implemented for the purpose of purely high resolution, high accuracy, and high efficiency in imaging, displacement measurement, treatment, and the like.

  According to the present invention, similarly to harmonic imaging, it is possible to increase the frequency, increase the bandwidth, increase the contrast, or suppress side lobes, and enable nonlinear imaging with a high S / N ratio. In addition, analog detection or digital detection can be performed simultaneously without requiring a large amount of memory and calculation.

  The effectiveness of the present invention has been demonstrated through ultrasonic echo imaging and measurement imaging through simulations and agar phantom experiments. The present invention can be applied to any coherent signal other than the ultrasonic echo method (light wave, OCT, electricity, magnetic field signal, radiation such as X-ray, heat wave, etc.), and different types of coherent signals. Can also be applied. A signal including an incoherent signal by analog processing (for example, energy detection of a received signal using a sensor or energy detection using a non-linear element) or digital processing may be processed together with the coherent signal.

  On the other hand, in the field of image measurement, it is often possible to observe motion using an incoherent signal (result display is an image) through various detections (physical phenomenon or normal signal processing) for the coherent signal. Known (various such as cross-correlation processing and optical flow). If this method is used for an incoherent signal, the bandwidth can be increased (high resolution). The high-resolution detection signal obtained by the present invention can also be used. The measurement accuracy of those movements is also improved. That is, the present invention applies to any coherent or incoherent signal.

  Imaging and motion measurement using the above-mentioned coherent signal and incoherent signal have been performed in various fields including the above-mentioned examples, etc., and have a very long history. Alternatively, it is effective and useful to perform wide-band high-resolution and high-contrast imaging including low frequencies and to measure displacement with high accuracy. It is effective including the engineering effects unique to multidimensional signal processing. Further, in the above-mentioned other applications such as treatment, it is also effective and useful to evaluate and apply the effect based on imaging of the non-linear effect.

  In an imaging apparatus, it is useful to generate a harmonic component and a basebanded signal (the above-mentioned new detection signal) by performing multiplication or calculation, and to generate an image signal based on them, but multiplication and calculation are used. The same effect can be obtained not only when the high-order nonlinear processing is performed. In view of cost and the like, it may be selectively adopted or used together with the prior art.

  The present invention is not limited to the above-described embodiments, and many modifications can be made within the technical idea of the present invention by those having ordinary knowledge in the technical field. Reflecting waves, transmitted waves, scattered waves (forward scattered waves or backward waves) for waves such as electromagnetic waves, vibration waves (mechanical waves) including thermal waves (compression waves), shear waves, surface waves, etc., or heat waves Scattered waves, etc.), refracted waves, surface waves, shock waves, those waves generated from self-emanating wave sources, waves emitted from moving bodies, waves coming from unknown wave sources, etc. For the observed wave, an appropriately set digital signal processing algorithm (in a mounted digital circuit or software) such as displacement (vector) measurement or temperature measurement, or analog or digital hardware is used. Patent Documents 5 to 7 and 11 relating to displacement measurement methods (determining the propagation direction of sensing waves with high accuracy and observing object displacement, particle displacement, medium displacement, etc. with high accuracy, and wave propagation is the object of observation. Various measurement methods disclosed in other cases, such as detailed high-precision observation) and others, are often disclosed centering on examples in the reflection method and the echo method. However, the present invention is not limited to these.

  The present invention can be used in a beam forming method for performing beam forming using an arbitrary wave arriving from a measurement object, and a measurement imaging apparatus and a communication apparatus using such a beam forming method. is there.

  Generation of wave signals such as radar, sonar, other optical waves, sound waves, heat waves, etc. is often already generated by digital devices, and it is highly aimed at applying the signals. It can be applied in conjunction with signal generation only by providing processing capability for performing the next calculation. The multi-dimensionalization of various devices is also being attempted, and the importance of the present invention will increase. Measurement objects are solid, fluid, rheology, inorganic, organic, creatures, environments, etc., and the measurement range is expected to expand. In the future, miniaturization of each device in the device will further progress, and the calculation stress will be sufficiently high, and it will be possible to incorporate a computer at a lower cost, and many useful devices with real time will be realized. We can expect to go. In addition to the simple wave imaging device, the development of applications through measurement using waves will become more popular and the application range will be broadened. The digitization of various devices is expected to progress further in the future, and at that time, it is considered that the demand for high-precision and high-speed beam forming capable of generating a high-precision signal according to the present invention in real time will increase. After all, in addition to being fast, there is no need to perform the necessary interpolation approximation so far. However, in the present invention, further high speed is emphasized, and processing with interpolation approximation may be performed as necessary, although the accuracy is reduced. It is also an effective device for normal communications and sensor networks. The applicability and marketability of digital beamforming according to the present invention based on digital signal processing is much higher.

  DESCRIPTION OF SYMBOLS 10 ... Transmission transducer (or applicator), 10a ... Transmission aperture element, 20 ... Reception transducer (or reception sensor), 20a ... Reception aperture element, 30 ... Apparatus main body, 31 ... Transmission unit, 31a ... Transmitter, 32 ... Reception Unit, 32a ... receiver, 32b ... AD converter, 32c ... memory (or storage device or storage medium), 33 ... digital signal processing unit, 34 ... control unit, 35 ... reception unit (or reception device), 35a ... reception 35b ... AD converter, 35c ... memory (or storage device or storage medium), 35d ... phasing adder, 35e ... other data generation unit, 40 ... input device, 50 ... output device, 60 ... external storage device, DESCRIPTION OF SYMBOLS 1 ... Measurement object, 1a ... Contrast agent, 110 ... Transducer, 111 ... Non-linear device, 112 ... Action device, 120, 1 DESCRIPTION OF SYMBOLS 0a, 120b ... Imaging apparatus main body, 121 ... Transmitter, 121a ... Transmission delay element, 122 ... Receiver, 122a ... Reception delay element, 123 ... Filter / gain adjustment part, 124 ... Non-linear element, 125 ... Filter / gain adjustment part , 126 ... detector, 127 ... AD converter, 128 ... storage device, 129 ... reception beamformer, 130 ... calculation unit, 131 ... image signal generation unit, 132 ... measurement unit, 133 ... control unit, 134 ... display device, 135: Analog display device, 140: External storage device

Claims (3)

In an orthogonal coordinate system using an axial direction determined by an aperture direction of an arbitrary receiving aperture element array and at least one lateral coordinate orthogonal thereto, from at least one wave source located in an arbitrary direction toward the measurement object Waves are transmitted, and waves coming from the measurement object are processed as if they were transmitted or received by beamforming in the axial direction or a direction that is symmetric with respect to the axial direction. In the case of a lateral modulation where 3 or 4 waves are superimposed in the dimension case,
Receiving a wave coming from the measurement object by at least one receiving aperture element to generate a received signal;
(B) generating a multidimensional received signal by performing beam-forming processing on the received signal generated in step (a) and performing lateral modulation;
Performing a Hilbert transform process on the multidimensional received signal generated in step (b);
Comprising
Step (c) performs partial differential processing or one-dimensional Fourier transform in the axial direction or the horizontal direction, and in the case of two dimensions, generates an analysis signal of each of the two-dimensional received signals of the two waves. A beamforming method including generating an analysis signal of a multidimensional received signal of each of the three or four waves. In an orthogonal coordinate system using an axial direction determined by an aperture direction of an arbitrary receiving aperture element array and at least one lateral coordinate orthogonal thereto, from at least one wave source located in an arbitrary direction toward the measurement object Waves are transmitted, and waves coming from the measurement object are processed as if they were transmitted or received by beamforming in the axial direction or a direction that is symmetric with respect to the axial direction. In the case of a lateral modulation where 3 or 4 waves are superimposed in the dimension case,
Receiving means for receiving a wave coming from the measurement object by at least one receiving aperture element and generating a received signal;
A beam forming process is performed on the received signal generated by the receiving unit to perform lateral modulation, thereby generating a multidimensional received signal and a Hilbert transform process on the generated multidimensional received signal. A device body to perform;
Comprising
The apparatus main body performs partial differential processing or one-dimensional Fourier transform in the axial direction or the horizontal direction, and in the case of two dimensions, generates an analysis signal of each of the two-dimensional received signals of the two waves, A measurement imaging apparatus that generates an analysis signal of a multidimensional received signal of each of the three or four waves in some cases. In an orthogonal coordinate system using an axial direction determined by an aperture direction of an arbitrary receiving aperture element array and at least one lateral coordinate orthogonal thereto, from at least one wave source located in an arbitrary direction toward the measurement object Waves are transmitted, and waves coming from the measurement object are processed as if they were transmitted or received by beamforming in the axial direction or a direction that is symmetric with respect to the axial direction. In the case of a lateral modulation where 3 or 4 waves are superimposed in the dimension case,
Receiving means for receiving a wave coming from the measurement object by at least one receiving aperture element and generating a received signal;
A beam forming process is performed on the received signal generated by the receiving unit to perform lateral modulation, thereby generating a multidimensional received signal and a Hilbert transform process on the generated multidimensional received signal. A device body to perform;
Comprising
The apparatus main body performs partial differential processing or one-dimensional Fourier transform in the axial direction or the horizontal direction, and in the case of two dimensions, generates an analysis signal of each of the two-dimensional received signals of the two waves, In some cases, the communication device generates an analysis signal of a multidimensional reception signal of each of the three or four waves.