JPH10155792A - Photographing method and device by wave, and ultrasonic imaging device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To reduce a load for a data processing, and prevent effects due to an unevenness of characteristics of individual wave receivers from appearing on an image by performing a Fourier transform by a combination of an optical fractional Fourier transform and a fractional Fourier transform by a data processing. SOLUTION: When an ultrasonic wave is emitted on a sound field to be inspected FLD by driving a wave sending part SND, an echo is emitted on an input surface IN of an ultrasonic wave propagation medium MDA, and propagates in the inside thereof and is output from an output surface OUT. Then, the echo is received by a wave receiving part RCV, and a data collecting part ACQ collects complex amplitudes of wave receiving signals of respective wave receivers as digital data. A data processing part PRC read the data from the data collecting part ACQ and forms an image, and a display part DIS displays it as a visible image. A fractional Fourier transform (FRFT) for the image forming is performed by a serial operation by an optical FRFT by the ultrasonic wave propagation medium MDA, and a FRFT by a data processing by the data processing part PRC.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method and an apparatus for imaging by waves and an ultrasonic imaging apparatus, and more particularly, to receiving and receiving waves from an object to be imaged using a two-dimensional array of receivers. Orthography (orthogr
The present invention relates to a method and apparatus for generating an image, that is, an emmetropic image, by a wave motion and an ultrasonic imaging apparatus. Note that the category of the wave includes at least the electromagnetic wave and the sound wave.

[0002]

2. Description of the Related Art As a technique for capturing an orthographic image using a two-dimensional array of receivers, a wave hologram (h
There is a method of generating an image by a Fourier transform of an ologram). As shown in FIG. 7, a two-dimensional array A of a plurality of receivers R receives a wave W arriving from an object to be imaged. The hologram data of the wave W is obtained by storing the received signals of the individual receivers R in a memory M, and the hologram data is subjected to a two-dimensional Fourier transform by the image generation unit I. An orthographic image of a wave generation source, that is, a stereoscopic image of an imaging target is generated. This image is displayed on the display unit D.

[0003] As another technique for capturing an orthographic image using a two-dimensional array of receivers, there is a capturing method using a focal plane array. In this method, as shown in FIG. 8, a wave W arriving from an object to be imaged is focused by a lens (lens) V.
A stereoscopic image of an imaging target is formed on a two-dimensional array A of a plurality of receivers R. At this time, the two-dimensional array A becomes a focal plane array. Pixel data is obtained by storing the received signals of the individual receivers R in the memory M. The image generation unit I generates an orthographic image based on the pixel data, and displays the image on the display unit D.

[0004] Imaging by a focal plane array is
As shown in FIG. 9, the wave can be focused on the two-dimensional array A using a concave reflecting mirror C instead of a lens.

In imaging by a focal plane array, focusing of a wave by a lens V (or a concave reflecting mirror C) and free propagation of a wave in a space between the lens V (or a concave reflecting mirror C) and the two-dimensional array A are performed. As a result, two-dimensional Fourier transform is performed optically, and an orthographic image is formed on the surface of the two-dimensional array A.

That is, both of the above two methods are:
Mathematically, there is no difference in generating an image by Fourier transform, but only the difference between performing Fourier transform by data processing or performing optically. "Optical"
Is not limited to light in a narrow sense, but refers to optics about waves in general.

[0007]

In the case where the Fourier transform is performed by data processing, a defect of each receiver in the two-dimensional array or a noise (nois) included in each received signal is considered.
e) There is an advantage that the influences such as are weakened in the process of data processing, and an orthographic image which is not directly influenced by them is obtained. Further, data defects and the like can be easily corrected in the course of data processing, and the influence on the image can be eliminated.

However, on the other hand, a huge load is imposed on the data processing section, and a powerful data processing means such as an ultra-high-speed computer is required for performing real-time orthographic imaging. Not realistic.

On the other hand, the above-mentioned problem does not occur because the Fourier transform by the optical means has no operation time, but the received signal of each of the two-dimensional array receivers is replaced by the pixel of the image. Since the values are determined, there is a problem that the characteristics of the individual receivers are not uniform, or the influence of defects or noise included in the individual received signals appears directly in the orthographic image. In addition, the two-dimensional array must be sufficiently fine, for example, several hundred thousand pixels, to satisfy the desired definition of the image.

In focal plane array imaging using a reflection focusing means such as a concave reflecting mirror, the two-dimensional array is located in front of the reflection focusing means and obstructs the field of view.

SUMMARY OF THE INVENTION The present invention has been made to solve the above problems, and has as its object to reduce the data processing load for performing orthographic imaging and to provide individual receivers forming a two-dimensional array. It is an object of the present invention to realize an image pickup method and apparatus by wave motion and an ultrasonic image pickup apparatus in which the influence of irregularity of the characteristics of an image is hardly produced on an image.

Another object of the present invention is to realize an ultrasonic imaging apparatus with high echo utilization efficiency for performing orthographic imaging using a focal plane array using reflection focusing means.

[0013]

SUMMARY OF THE INVENTION The present invention provides a Fractional Fourie transform (F
RFT) and a wave propagation medium having a distributed refractive index (quadratic graded index media)
(quadratic graded index media) (GRIN medium).

Therefore, first, FRFT and GRI
The N medium will be described. [FRFT] Regarding FRFT, for example, reference D. Mend
lovic and HM Ozaktas, "Fractionl Fourie transfo
rms and their optical implementation: Part I, "J.
Opt. Soc. Am. A, Vol. 10, pp. 1875-1881, 1993 (Reference 1).

According to this, the FRFT transforms the ordinary Fourier transform.

[0016]

(Equation 1)

When expressed as

[0018]

(Equation 2)

## EQU1 ## Here, the order a is a real number. That is, the order a can take fractional or decimal values. This is why it is called fractional.

The FRFT of order a and the FRFT of order b can be performed in series (cascade), in which case the following relationship is established.

[0021]

(Equation 3)

Here, when a + b = 1, it becomes the same as a normal Fourier transform. By utilizing this relationship,
A normal Fourier transform can be performed by serial operation of a plurality of FRFTs.

As a technique for executing the FRFT at high speed by a computer, discrete fractional technology is used.
Discrete Fractional Fourie transform
(DFRFT) is described, for example, in the literature HM Ozaktas et.al.,
"Digital Computation of the Fractional Fourie Tra
nsform, "IEEE, Transactions on Signal Processing,
Vol. 44, pp. 2141-2150, 1996 (Reference 2).

[GRIN Medium] The GRIN medium is known as a means for optically performing two-dimensional FRFT. This is also described in, for example, the above-mentioned document 1.

As shown in FIG. 10, the GRIN medium has two parallel surfaces PL1 and PL2 opposed to each other, and the space between them is filled with a predetermined wave propagation material. The wave signal is incident on, for example, one surface PL1,
The light propagates inside and is output from the other surface PL2.

The refractive index of this GRIN medium is

[0027]

(Equation 4)

Given by Here, n1 and n2 are medium constants, and r is a distance from the optical axis AX. R-direction distribution of refractive index given by the above equation (profile)
Is maximum at the position of the optical axis AX as shown in FIG. 11, for example, and decreases as the distance from the optical axis AX increases. Note that the refractive index does not fall below 1. That is, the refractive index has a predetermined distribution characteristic in a plane perpendicular to the optical axis AX.

By having such a distributed index of refraction, inside the GRIN medium, on the optical axis AX, from the entrance plane PL1.

[0030]

(Equation 5)

A focal point F is formed at a position at the distance of. Therefore, an orthographic image of the subject at the point at infinity based on the wave incident from the incident surface PL1 is formed at the position of the focal point F. An object located at a position closer to the point at infinity forms an image behind the focal point F according to the distance. This is nothing but optical Fourier transform performed inside the GRIN medium.

However, unlike the lens optical system, the GRI
Inside the N medium, the focusing and propagation of the wave proceed simultaneously and in parallel due to the distribution characteristics of the refractive index as described above. Therefore, in the GRIN medium, the infinitely small order F
It can be said that an infinite number of RFTs are performed in series, and as a result, an FRFT of order 1 at the position of the focal point F, that is, a normal Fourier transform is completed.

In other words, the distance from the entrance plane PL1 is m
An FRFT of order m / L is performed up to the section PL3 of (<L), and an FRFT of order (L−m) / L is performed up to the focal point F as a result of the FRFT. But

[0034]

(Equation 6)

It can be said that the above FRFT is performed. Next, means for solving the problem will be described. [1] The invention according to claim 1, which solves the above problem, is an imaging method for generating an image by Fourier transformation of a wave signal incident on a two-dimensional aperture from an imaging target, wherein the Fourier transformation is performed by an optical fractional method. -It is characterized by performing by a combination of Fourier transform and fractional Fourier transform by data processing.

According to the first aspect of the present invention, the FRFT of the wave signal incident on the two-dimensional aperture is optically executed, and the resulting FRFT is executed by data processing to complete the first-order FRFT. Therefore, the burden on the FRFT due to the data processing is reduced by the amount of the optical FRFT.
Further, since an image is generated by the FRFT based on the data processing of the result of the optical FRFT,
Effects such as irregularities in the characteristics of the individual receivers forming a two-dimensional array that receives the result of T do not appear directly on the image. That is, it is possible to realize an imaging method using wave motion, in which the burden of data processing is small and the effects of irregularities in the characteristics of the individual receivers forming a two-dimensional array are unlikely to appear in an image when performing orthographic imaging. .

According to the first aspect of the present invention, the FRFT by the data processing is performed by the DFRFT.
This is preferable in that T is performed at high speed. The category of the wave in the first aspect of the invention includes at least an electromagnetic wave and a sound wave. Also, "optics" refers to optics related to waves, and does not mean only optics in a narrow sense of handling light.

[2] The invention according to claim 2, which solves the above problem, is an imaging apparatus which generates an image by Fourier transform of a wave signal incident on a two-dimensional aperture from an imaging object,
A wave propagating unit having a distributed refractive index having an input surface of a wave from an imaging object at one end and an output surface of the wave at the other end, and a two-dimensional array of a plurality of receivers, and an output from the wave propagating unit. Receiving means for receiving the generated wave, and an image generating means for generating an image by a fractional Fourier transform of the received signal of the receiving means.

According to the second aspect of the present invention, the wave propagation means optically performs the FRFT of the wave signal incident on the two-dimensional aperture, and the wave receiving means receives the result of the optical FRFT,
The received signal is subjected to FRFT by an image generating means to generate an image. For this reason, the burden of the FRFT on the image generating means is reduced by the amount of the optical FRFT. Further, since an image is formed by the FRFT by the image generation means,
It is not directly affected by irregularities in the characteristics of the individual receivers forming the dimensional array. In other words, it is possible to realize an imaging apparatus based on wave motion, in which the burden of data processing is small and the effects of irregularities in characteristics of individual receivers forming a two-dimensional array are unlikely to appear in an image when performing orthographic imaging. .

In the second aspect of the present invention, it is preferable that the FRFT by the image generating means be performed by the DFRFT in that the image generation is performed at a high speed. The category of the wave and the meaning of "optical" in the second aspect of the invention are as described above.

[3] According to a third aspect of the present invention, there is provided a transmitting means for transmitting an ultrasonic wave to a sound field to be detected, and a two-dimensional array of a plurality of receivers. Receiving means for receiving an echo from a field, an ultrasonic wave propagating medium interposed between the transmitting means and the receiving means and the sound field to be measured, based on a received signal of the receiving means An ultrasonic imaging apparatus comprising: an image generating unit configured to generate an image, wherein echoes from a boundary between the ultrasonic wave propagation medium and the outside thereof are individually received by a plurality of receivers of the wave receiving unit. Correction means for correcting the characteristics of the individual receivers of the wave receiving means based on the obtained signal.

According to the third aspect of the invention, the characteristics of the individual receivers of the wave receiving means are corrected by the correcting means. Therefore, it is possible to obtain a received signal that is not affected by irregularities in the characteristics of the individual receivers of the two-dimensional array. That is, it is possible to realize an ultrasonic imaging apparatus which is not affected by irregularities in characteristics of individual receivers forming a two-dimensional array when performing orthographic imaging.

According to the third aspect of the present invention, it is preferable to provide an acoustic lens at a boundary between the ultrasonic wave propagation medium and the sound field to be measured, in order to perform imaging by a focal plane array.

[4] The invention according to a fourth aspect of the present invention, which solves the above-mentioned problem, comprises a transmitting means for transmitting an ultrasonic wave to a sound field to be detected, and a two-dimensional array of a plurality of receivers. Receiving means for receiving an echo from a field, an ultrasonic wave propagation medium interposed between the receiving means and the test sound field, and an image for generating an image based on a received signal of the receiving means An ultrasonic imaging device comprising: a generating unit, wherein a path of an echo from a test sound field in the ultrasonic wave propagation medium is substantially horizontally bent and focused, and is incident on the wave receiving unit. And a reflection focusing means.

According to the fourth aspect of the present invention, the path of the echo in the ultrasonic wave propagation medium is substantially laterally bent and focused by the reflection focusing means, and is incident on the wave receiving means. For this reason, by arranging the receiving unit at a position where the field of view of the reflection focusing unit is not obstructed, all of the arriving echoes can be made incident on the receiving unit. That is, it is possible to realize an ultrasonic imaging apparatus with high echo utilization efficiency for performing orthographic imaging using a focal plane array using the reflection focusing means.

In the invention of claim 4, it is preferable that the reflection focusing means is an offset parabola reflecting mirror in terms of simplifying the configuration.

[0047]

Embodiments of the present invention will be described below in detail with reference to the drawings. Note that the present invention is not limited to the embodiment.

[Embodiment 1] FIG. 1 is a block diagram of an ultrasonic imaging apparatus. This device is an example of an embodiment of the present invention. Note that an example of an embodiment relating to the device of the present invention is shown by the configuration of the present device. Also,
An example of an embodiment relating to the method of the present invention is shown by the operation of the present apparatus.

First, the configuration of the present apparatus will be described. As shown in FIG. 1, the present apparatus has a transmitting unit SND, which is driven by a driving unit DRV, so as to irradiate an ultrasonic wave to a test sound field FLD in which a subject exists. An echo (echo) for this ultrasonic wave returns from the test sound field FLD. An ultrasonic echo is an example of an embodiment of a wave according to the present invention. The echo enters the input surface IN of the ultrasonic wave propagation medium MDA, propagates inside, and is output from the output surface OUT. The ultrasonic wave propagation medium MDA is an example of an embodiment of the wave propagation means in the present invention. The input surface IN is an example of the embodiment of the two-dimensional aperture in the present invention.

The ultrasonic wave propagation medium MDA is a GRIN medium and has a distributed refractive index as shown in the above equation (4) and FIG. Such a GRIN medium can be made of, for example, a silicone rubber whose composition continuously changes from the center of the optical axis toward the periphery.

The ultrasonic propagation medium MDA is formed, for example, in a columnar shape as shown in FIG. 2, and has an input surface IN and an output surface OUT.
Are perpendicular to the optical axis AX. The distance K between the input surface IN and the output surface OUT, that is, the length of the optical axis AX is shorter than the focal length L given by the above equation (5).

The output part OUT of the ultrasonic wave propagation medium MDA is provided with a wave receiving part RCV. The receiving unit RCV is an example of an embodiment of the receiving unit in the present invention. The ultrasonic wave output from the output surface OUT is received by the receiving unit RCV. The receiving unit RCV is configured by a two-dimensional array of a plurality of receiving units ULT, for example, as shown in FIG. Thereby, the two-dimensional distribution of the ultrasonic waves output from the output surface OUT is received. The receiver ULT converts an ultrasonic wave into an electric signal, and is made of, for example, a piezoelectric material such as PZT (lead zirconate titanate) ceramics.

The receiving unit RCV is connected to the data collecting unit ACQ. The received signal of each receiver ULT of the receiving unit RCV is input to the data collection unit ACQ. The data collection unit ACQ collects the complex amplitude of the received signal of each receiver ULT as digital data.

The data collection unit ACQ is provided with a data processing unit PRC.
It is connected to the. The data processing unit PRC is an example of an embodiment of an image generating unit according to the present invention. The data processing unit PRC reads data from the data collection unit ACQ and processes the data to generate an image.
The data processing unit PRC is constituted by, for example, a computer. Data processing in the data processing unit PRC will be described later.

The display section DIS is connected to the data processing section PRC. The image generated by the data processing unit PRC is displayed as a visible image by the display unit DIS. The above-described drive unit DRV, data collection unit ACQ, data processing unit PRC
The display unit DIS is connected to the control unit CNT.
The control unit CNT gives a control signal to them to control the operation. An operation unit OPC is connected to the control unit CNT. The operation unit OPC is operated by an operator, and various commands and information desired by the operator are given to the control unit CNT.

Next, the operation of the present apparatus will be described. The operation is performed under the control of the control unit CNT. The transmitting unit SND is driven by the driving unit DRV, and the sound field FLD to be measured is irradiated with ultrasonic waves. The echo for this ultrasonic wave is the sound field FL to be measured.
Return from D. The echo enters the ultrasonic wave propagation medium MDA from the input surface IN, propagates inside, and is output from the output surface OUT.

Since the ultrasonic wave propagation medium MDA is a GRIN medium, the echo incident on the input surface IN is FRFT as described above as it propagates inside. Therefore, on the output surface OUT, an FRFT of order K / L (<1) of the echo incident on the input surface IN is obtained.

The echo intensity at the input surface IN is represented by f (x,
y), where K / L = a, the ultrasonic output signal on the output surface OUT is expressed by the following equation.

[0059]

(Equation 7)

Here,

[0061]

(Equation 8)

[0062]

(Equation 9)

[0063]

(Equation 10)

[0064]

[Equation 11]

Note that Hl and Hm in equation (9) are Hermite polynomials of order 1 and m, respectively. Ultrasonic propagation medium MDA represented by equation (7)
Are received by the receiver RCV, and the individual receivers U
The complex amplitude of the received signal of the LT is collected as digital data by the data collection unit ACQ.

The data processing section PRC performs an (LK) / L-order FRFT on these data. This FRF
T is preferably performed by DFRFT in terms of speeding up the processing. When (LK) / L = b, the FRFT by the data processing unit PRC is expressed by the following equation.

[0067]

(Equation 12)

Here, since a + b = 1, (12)
The equation is a first-order FRFT. Therefore, the same result as the ordinary Fourier transform of the hologram of the echo is obtained, and an orthographic image of the subject in the sound field to be detected is generated.
This image is provided to the display unit DIS and displayed as a visible image.

The image generated at this time is focused on the point at infinity. The image of the subject at a position closer to that position is located at a position L ′ (> L) deeper than the focal length L.
Therefore, the order of FRFT in the ultrasonic wave propagation medium MDA is K / L '. Therefore, by setting the order of the FRFT by the data processing unit PRC to (L′−K) / L ′, an image focused on the subject can be obtained. The order (L'-K) / L 'is specified by the operator through the operation unit OPC. In this manner, variable focus imaging can be performed with the optical system fixed.

As described above, the Fourier transform for generating an image is performed by serial operation of the optical FRFT by the ultrasonic wave propagation medium MDA and the FRFT by data processing by the data processing unit PRC. In other words, the Fourier transform is shared and executed by the ultrasonic wave propagation medium MDA and the data processing unit PRC in the form of FRFT. For this reason, the burden of data processing on the data processing unit PRC is
It is reduced by the amount of the optical FRFT in the ultrasonic wave propagation medium MDA.

The received signal of the receiving unit RCV becomes an image through the FRFT by the data processing unit PRC. Therefore, as in the case of the focal plane array, the received signal of the receiving unit RCV is the same as the pixel of the image. There is no one-to-one correspondence.
For this reason, even if the individual receivers ULT have irregular characteristics or the like, the influence is reduced in the process of the FRFT and does not appear directly on the image. Further, by performing data correction in the process of data processing, almost no influence can be obtained.

Also, since the pixels of the image do not correspond one-to-one with the received signal of the receiving unit RCV, the receiving unit RCV
The definition of the two-dimensional array is allowed to be much coarser than that required for the image.

The above is an example in which the wave used for imaging is an ultrasonic wave, but the wave is not limited to the ultrasonic wave, but may be an electromagnetic wave such as light. The GRIN medium for light can be made of, for example, optical glass whose composition is continuously changed from the optical axis toward the periphery.

[Embodiment 2] FIG. 4 is a block diagram of an ultrasonic imaging apparatus. This device is an example of an embodiment of the present invention.

First, the configuration of the present apparatus will be described. This device has a transmitting unit SND and a receiving unit RCV. Transmitter SN
D is an example of an embodiment of the wave transmitting means in the present invention. The receiving unit RCV is an example of an embodiment of the receiving unit in the present invention. The receiving unit RCV is configured by a two-dimensional array of a plurality of receivers ULT, as shown in FIG.

A liquid chamber RMM is provided between the transmitting section SND and the receiving section RCV and the test sound field FLD. Liquid chamber RM
The inside of M is filled with, for example, water. Water and the like are examples of the embodiment of the ultrasonic wave propagation medium in the present invention.
The bottom surface BTM of the liquid chamber RMM is a thin film, and is in contact with the test sound field FLD through the thin film. The bottom surface BTM of the liquid chamber RMM is an example of an embodiment of the boundary portion between the ultrasonic wave propagation medium and the outside thereof in the present invention.

In the liquid chamber RMM, the distance from the wave receiving surface of the wave receiving part RCV to the bottom surface BTM is equal to the opening diameter of the wave receiving part RCV which is equal to 1.
It is configured to be about 4 to 2 times. Liquid chamber RMM
A sound absorbing material ABS is provided on the inner side of the side wall.

The transmitting unit SND is connected to the driving unit DRV. The transmitting unit SND is driven by the driving unit DRV to generate ultrasonic waves. The ultrasonic waves pass through the liquid chamber RMM and are applied to the sound field to be measured FLD. The ultrasonic echo returns from the test sound field FLD, passes through the liquid chamber RMM, and enters the wave receiving unit RCV. The echoes that have entered the receiving unit RCV are received by the individual receivers ULT.

The data receiving unit ACQ is connected to the receiving unit RCV. The data collection unit ACQ is similar to that in FIG. 1 and the individual receivers UL of the receiver RCV
The complex amplitude of the T received signal is collected as digital data.

The data collection unit ACQ is provided with a data processing unit PRC.
It is connected to the. The data processing unit PRC is an example of an embodiment of an image generating unit according to the present invention. It is also an example of the embodiment of the correction means in the present invention.

The data processing section PRC is constituted by, for example, a computer. The data processing unit PRC processes the data collected by the data collection unit ACQ to generate an image. The data processing will be described later. The display unit DIS is connected to the data processing unit PRC. The image generated by the data processing unit PRC is displayed by the display unit DIS.

The above-described drive unit DRV and data collection unit AC
Q, the data processing unit PRC and the display unit DIS
Connected to NT. The control unit CNT gives a control signal to them to control the operation. An operation unit OPC is connected to the control unit CNT. The operation unit OPC is operated by an operator, and various commands and information desired by the operator are given to the control unit CNT. A calibration operation of the receiving unit RCV described below is also instructed to the control unit CNT through the operation unit OPC.

Next, the operation of the present apparatus will be described. The operator causes the apparatus to calibrate the receiving unit RCV prior to imaging. In the calibration mode (mode), the following operation is performed under the control of the control unit CNT.

By driving the transmitting section SND with the driving section DRV, an ultrasonic pulse is transmitted. In response to this ultrasonic wave, an echo from the bottom surface BTM of the liquid chamber RMM returns to the wave receiving unit RCV. Since the distance from the bottom surface BTM to the receiving surface of the receiving unit RCV is sufficient, the receiving unit RCV
Can be regarded as uniform.

The received signal of such an echo is collected by the data collecting unit ACQ. As a result, echo data for each individual receiver ULT is collected. These echo data reflect the characteristics of the individual receivers ULT. Since the intensity distribution of the echo on the receiving surface is uniform, all the echo data should be the same, but the receiver ULT
For example, when there is a variation in sensitivity or the like, a difference occurs between the echo data.

The data processing unit PRC checks the difference between the echo data, and obtains a correction value for making all the echo data identical for each of the receivers ULT. These correction values are stored in a memory (not shown) in the data processing unit PRC, and the calibration mode ends.

When transmitting an ultrasonic pulse by focusing on a point on the bottom surface BTM of the liquid chamber, for example, the center of the bottom surface BTM, the echo is generated from that point and becomes a spherical wave to be received. Return to RCV. For this reason, on the receiving surface of the receiving unit RCV, the echo draws a circular ripple and spreads, and the ripple is reflected on the echo data collected by the data collecting unit ACQ.

When the individual receivers ULT of the receiver RCV have variations in phase characteristics or delay characteristics, the ripples reflected in the echo data do not have a correct circular shape. In such a case, the data processing unit PRC also obtains the phase or delay correction value of each echo data and stores it in the memory.

After completing such calibration, imaging is started. At the time of imaging, an ultrasonic wave is transmitted from the transmitting unit SND to the sound field FLD via the liquid chamber RMM, and the echo returns from the sound field FLD to the receiving unit RCV via the liquid chamber RMM.

The echoes are received by the individual receivers UL of the receiver RCV.
T, and the received signals are transmitted to the data collection unit A.
Collected as echo data of complex amplitude by CQ.
This echo data forms a hologram of the received echo. The data processing unit PRC individually corrects the echo data with the above-described correction value. As a result, echo data excluding the influence of variations in characteristics of individual receivers, that is, correct hologram data can be obtained.

The data processing unit PRC performs a two-dimensional Fourier transform on the hologram data to obtain a sound field FLD to be detected.
Generates an orthographic image of the subject at. This image is displayed on the display unit DIS.

Since the hologram data has been corrected for errors due to variations in the characteristics of the individual receivers ULT, images generated based on the hologram data are not affected by the variations in the characteristics of the individual receivers ULT. Become.

[Embodiment 3] The influence of variations in the characteristics of the receiver ULT becomes a particularly serious problem when imaging is performed using a focal plane array. The data correction as described above can also be applied to imaging by a focal plane array. Next, it will be described.

FIG. 5 is a block diagram of an ultrasonic imaging apparatus. This device is an example of an embodiment of the present invention. First,
The configuration of the present apparatus will be described. This device has a transmitting unit SND and a receiving unit RCV. The transmitting unit SND is an example of an embodiment of the transmitting unit in the present invention. The receiving unit RCV is an example of an embodiment of the receiving unit in the present invention. The receiving unit RCV is configured by a two-dimensional array of a plurality of receivers ULT, as shown in FIG.

The transmitting part SND, the receiving part RCV and the sound field F to be detected
A liquid chamber RMM is provided between the LDs. The inside of the liquid chamber RMM is filled with, for example, water. Water and the like are examples of the embodiment of the ultrasonic wave propagation medium in the present invention. An acoustic lens LNS is provided on the bottom surface BTM of the liquid chamber RMM,
It is in contact with the sound field to be tested FLD through it. The acoustic lens LNS is an example of an embodiment of a boundary portion between the ultrasonic wave propagation medium and the outside thereof in the present invention.

The liquid chamber RMM is configured such that the distance from the acoustic lens LNS to the wave receiving surface of the wave receiving portion RCV is about 1.4 to 2 times the opening diameter of the wave receiving portion RCV. A sound absorbing material ABS is provided inside the side wall of the liquid chamber RMM.

The driving section DRV is connected to the transmitting section SND. The transmitting unit SND is driven by the driving unit DRV to generate ultrasonic waves. The ultrasonic wave passes through the liquid chamber RMM and the acoustic lens LNS, and is applied to the sound field to be measured FLD. The ultrasonic echo returns from the test sound field FLD, is focused by the acoustic lens LNS, and is received by the receiving unit RC through the liquid chamber RMM.
V.

Due to the convergence effect of the acoustic lens LNS, an orthographic image of the subject is formed on the surface of the receiving portion RCV as an intensity distribution of the echo. That is, the receiving unit RC
V is a focal plane array. The echoes that have entered the receiving unit RCV are received by the individual receivers ULT.

[0099] The data collection unit ACQ is connected to the reception unit RCV. The data collection unit ACQ is similar to that in FIG. 1 and the individual receivers UL of the receiver RCV
The received signal of T is collected as digital data. The digital data gives the pixel value of the orthographic image of the subject.

The data collection unit ACQ is provided with a data processing unit PRC.
It is connected to the. The data processing unit PRC is an example of an embodiment of an image generating unit according to the present invention. It is also an example of the embodiment of the correction means in the present invention. The data processing unit PRC is configured by, for example, a computer.

The data processing unit PRC includes a data collection unit AC
Q processes the collected data to generate an image. The generated image is displayed on the display unit DIS connected to the data processing unit PRC. The data processing will be described later.

The above-described drive section DRV and data collection section AC
Q, the data processing unit PRC and the display unit DIS
Connected to NT. The control unit CNT gives a control signal to them to control the operation. An operation unit OPC is connected to the control unit CNT. The operation unit OPC is operated by an operator, and various commands and information desired by the operator are given to the control unit CNT. A calibration operation of the receiving unit RCV described below is also instructed to the control unit CNT through the operation unit OPC.

Next, the operation of the present apparatus will be described. The operator causes the apparatus to calibrate the receiving unit RCV prior to imaging. In the calibration mode, the following operation is performed under the control of the control unit CNT.

The transmitting section SND is driven by the driving section DRV to transmit ultrasonic pulses. In response to this ultrasonic wave, an echo from the surface of the acoustic lens LNS returns to the receiving unit RCV. Since the distance from the acoustic lens LNS to the receiving surface of the receiving unit RCV is sufficient, the intensity distribution of the echo on the receiving surface of the receiving unit RCV can be regarded as uniform.

The received signal of such an echo is collected by the data collecting unit ACQ. As a result, echo data for each individual receiver ULT is collected. These echo data reflect the characteristics of the individual receivers ULT. Since the intensity distribution of the echo on the receiving surface is uniform, all the echo data should be the same, but the receiver ULT
For example, when there is a variation in sensitivity or the like, a difference occurs between the echo data.

The data processing unit PRC checks the difference between the echo data, and obtains a correction value for making all the echo data the same for each of the receivers ULT. These correction values are stored in a memory (not shown) in the data processing unit PRC, and the calibration mode ends.

After completing such calibration, imaging is started. At the time of imaging, an ultrasonic wave is transmitted from the transmitting unit SND to the test sound field FLD via the liquid chamber RMM and the acoustic lens LNS, and the echo returns from the test sound field FLD.
The echo is focused by the acoustic lens LNS and forms an orthographic image on the receiving unit RCV.

Such an orthographic signal is received by the receiving unit R
The signals are received by the individual receivers ULT of the CV, and the received signals are collected as data by the data collection unit ACQ. The data processing unit PRC individually corrects the data using the above correction values. As a result, data excluding the influence of variations in the characteristics of the individual receivers, that is, correct pixel values of the orthographic image can be obtained.

The data processing section PRC generates an image using the data as a pixel value. This image is displayed on the display unit DIS. Since the data collected by the data collection unit ACQ is corrected for errors due to variations in the characteristics of the individual receivers ULT, images formed based on the data are affected by variations in the characteristics of the individual receivers ULT. Will not be. [Embodiment 4] FIG. 6 is a block diagram of an ultrasonic imaging apparatus. This device is an example of an embodiment of the present invention. First, the configuration of the present apparatus will be described. This device is a transmitter S
Has ND. The transmitting unit SND is an example of an embodiment of the transmitting unit in the present invention. The transmitting unit SND is the driving unit DR
Connected to V. The transmitting unit SND is driven by the driving unit DRV to transmit ultrasonic waves to the sound field to be measured FLD.

This device has a liquid chamber RMM. Liquid chamber R
The MM is filled with, for example, water or the like. Water and the like are examples of the embodiment of the ultrasonic wave propagation medium in the present invention. The bottom surface BTM of the liquid chamber is a thin film, and is in contact with the test sound field FLD through the thin film. The echo returning from the test sound field is
It passes through the bottom surface BTM and enters the liquid chamber RMM. A sound absorbing material ABS is provided inside the side wall of the liquid chamber RMM.

A wave receiving part RCV is provided on the side of the liquid chamber RMM. The receiving unit RCV is an example of an embodiment of the receiving unit in the present invention. The receiving unit RCV is configured by a two-dimensional array of a plurality of receivers ULT, as shown in FIG. The receiving part RCV is the bottom BTM of the liquid chamber RMM.
At a position deviating from the path of the echo that has passed through the receiving surface, the receiving surface is arranged substantially in the horizontal direction.

An acoustic reflector MRR is provided above the liquid chamber RMM so as to face the bottom surface BTM. Acoustic reflector M
RR is an example of an embodiment of the reflection focusing means in the present invention. The acoustic reflecting mirror MRR is an offset parabolic reflecting mirror, and is configured to substantially reflect and converge the echo coming from the bottom surface BTM in the horizontal direction and to make it incident on the receiving unit RCV. In addition, the lateral direction is the bottom surface BTM.
Means the horizontal direction as viewed from the path of the echo passing through.

Due to the focusing effect of the acoustic reflector MRR, an orthographic image of the object is formed on the surface of the wave receiving portion RCV as an intensity distribution of the echo. That is, the receiving unit RC
V is a focal plane array. The echoes that have entered the receiving unit RCV are received by the individual receivers ULT.

A data collection unit ACQ is connected to the reception unit RCV. The data collection unit ACQ is similar to that in FIG. 1 and the individual receivers UL of the receiver RCV
The received signal of T is collected as digital data. The digital data gives the pixel value of the orthographic image of the subject.

The data collection unit ACQ is provided with a data processing unit PRC.
It is connected to the. The data processing unit PRC is an example of an embodiment of an image generating unit according to the present invention. The data processing unit PRC is configured by, for example, a computer. The data processing unit PRC generates an image using the data collected by the data collection unit ACQ as pixel values.
The generated image is displayed on the display unit DIS connected to the data processing unit PRC.

The above-described drive unit DRV and data collection unit AC
Q, the data processing unit PRC and the display unit DIS
Connected to NT. The control unit CNT gives a control signal to them to control the operation. An operation unit OPC is connected to the control unit CNT. The operation unit OPC is operated by an operator, and various commands and information desired by the operator are given to the control unit CNT.

Next, the operation of the present apparatus will be described. Transmitter S
Ultrasonic waves are transmitted from the ND to the test sound field FLD, and the echo returns from the test sound field FLD. The echo is the liquid chamber RMM
From the bottom surface BTM, is reflected and focused by the acoustic reflecting mirror MRR, and forms an orthographic image on the receiving unit RCV.

When such an orthographic signal is received by the receiving unit R
The signals are received by the individual receivers ULT of the CV, and the received signals are collected as data by the data collection unit ACQ. The data processing unit PRC generates an image using the data as a pixel value. This image is displayed on the display unit DIS.

In this apparatus, the wave receiving part RCV is connected to the liquid chamber R
The echo returning from the test sound field FLD is placed on the receiving surface of the echo reflector MR offset from the path of the echo passing through the bottom surface BTM of the MM.
Since the path is bent and focused by R to irradiate, the echo returned from the test sound field FLD is received by the receiving unit RC.
All are incident on the wave receiving unit RCV without being hindered by V.
For this reason, an ultrasonic imaging apparatus which performs orthography using a concave reflecting mirror and has a high use efficiency of echo is provided.

[0120]

As described above in detail, according to the first aspect of the present invention, the FRF of the wave signal incident on the two-dimensional aperture
Since T is executed optically and the resulting FRFT is executed by data processing to complete the first-order FRFT, the burden on the FRFT due to data processing is reduced by the amount of optical FRFT. Also, the optical F
Since the image of the result of the RFT is generated by the FRFT based on the data processing, the image is not directly affected by irregularities in characteristics of individual receivers forming a two-dimensional array for receiving the result of the optical FRFT. . In other words, it is possible to realize an imaging method using a wave, in which the burden on the data processing unit is small and the influence of irregularities in characteristics of the individual receivers forming a two-dimensional array is unlikely to appear in an image when performing orthographic imaging. it can.

According to the second aspect of the present invention, the wave propagation means optically performs the FRFT of the wave signal incident on the two-dimensional aperture, and the wave receiving means receives the result of the optical FRFT. Since the received signal is subjected to the FRFT by the image generating means to generate an image, the load on the FRFT by the image generating means is reduced by the amount of the optical FRFT.
Further, since the image is formed by the FRFT by the image generating means, there is no direct influence of irregularities in the characteristics of the individual receivers forming the two-dimensional array. In other words, it is possible to realize an imaging apparatus based on wave motion, in which the burden of data processing is small and the effects of irregularities in characteristics of individual receivers forming a two-dimensional array are unlikely to appear in an image when performing orthographic imaging. .

According to the third aspect of the present invention, the characteristics of the individual receivers of the receiving means are corrected by the correcting means, so that the characteristics of the individual receivers of the two-dimensional array are not uniform. A received signal which is not affected by the above can be obtained. That is, it is possible to realize an ultrasonic imaging apparatus which is not affected by irregularities in characteristics of individual receivers forming a two-dimensional array when performing orthographic imaging.

According to the fourth aspect of the present invention, the path of the echo in the ultrasonic wave propagation medium is substantially horizontally bent and focused by the reflection focusing means so as to be incident on the wave receiving means. By arranging the receiving means at a position where the field of view of the reflecting and focusing means is not obstructed, all of the arriving echoes can be made incident on the receiving means. That is,
In order to perform orthographic imaging using a focal plane array using the reflection focusing means, it is possible to realize an ultrasonic imaging apparatus with good use efficiency of echo.

[Brief description of the drawings]

FIG. 1 is a block diagram of a device according to an example of an embodiment of the present invention.

FIG. 2 is a schematic diagram of an ultrasonic wave propagation medium in an apparatus according to an example of an embodiment of the present invention.

FIG. 3 is a schematic diagram of a wave receiving unit in the device according to an embodiment of the present invention.

FIG. 4 is a block diagram of an apparatus according to an embodiment of the present invention.

FIG. 5 is a block diagram of an apparatus according to an embodiment of the present invention.

FIG. 6 is a block diagram of an apparatus according to an embodiment of the present invention.

FIG. 7 is a block diagram of a conventional example.

FIG. 8 is a block diagram of a conventional example.

FIG. 9 is a block diagram of a conventional example.

FIG. 10 is a schematic diagram of a GRIN medium.

FIG. 11 is a diagram showing characteristics of a GRIN medium.

[Explanation of symbols]

 FLD Sound field to be measured SND Transmitting unit DRV driving unit MDA Ultrasonic propagation medium AX Optical axis IN Input surface OUT Output surface RCV Receiving unit ULT Receiving unit ACQ Data collecting unit PRC Data processing unit DIS Display unit CNT Control unit OPC operation Part RMM liquid chamber BTM bottom ABS sound absorbing material LNS acoustic lens MRR acoustic reflector A two-dimensional array R receiver M memory I image generator D display V lens C concave reflector

Claims (4)

[Claims] 1. An imaging method for generating an image by a Fourier transform of a wave signal incident on a two-dimensional aperture from an imaging target, wherein the Fourier transform is performed by an optical fractional Fourier transform and a data processing. An imaging method using a wave, which is performed by a combination of 2. An imaging apparatus for generating an image by Fourier transform of a wave signal incident on a two-dimensional aperture from an imaging object, wherein the input surface of the wave from the imaging object has one end and the output surface of the wave has the other end. A wave propagating unit having a distributed refractive index, a wave receiving unit having a two-dimensional array of a plurality of receivers, receiving a wave output from the wave propagating unit, and a received signal of the wave receiving unit And an image generating means for generating an image by a fractional Fourier transform. 3. A wave transmitting means for transmitting an ultrasonic wave to a sound field to be measured, a wave receiving means having a two-dimensional array of a plurality of receivers and receiving an echo from the sound field to be measured, Ultrasound imaging comprising: a wave transmitting unit, an ultrasonic wave propagation medium interposed between the wave receiving unit and the test sound field, and an image generating unit for generating an image based on a received signal of the wave receiving unit An apparatus, wherein each of the plurality of receivers of the ultrasonic wave propagation medium individually receives echoes from a boundary portion between the ultrasonic wave propagation medium and the outside thereof based on signals received by the plurality of receivers of the wave receiving means. An ultrasonic imaging apparatus, comprising: a correction unit configured to correct characteristics of the detector. 4. A transmitting means for transmitting ultrasonic waves to a sound field to be measured, a receiving means having a two-dimensional array of a plurality of receivers and receiving echoes from the sound field to be tested, An ultrasonic imaging apparatus comprising: an ultrasonic wave propagation medium interposed between a wave receiving unit and a test sound field; and an image generating unit that generates an image based on a received signal of the wave receiving unit. A reflection focusing means for substantially bending the path of the echo from the test sound field in the ultrasonic wave propagation medium in the horizontal direction and converging the light to be incident on the wave receiving means. Sound wave imaging device.