JPS63134949A - Ultrasonic measuring instrument - Google Patents

Abstract

PURPOSE:To exactly measure an absorption characteristic of an ultrasonic wave by utilizing a non-linear phenomenon of a propagation generated when different pulses is superposed, and deriving an attenuation of the ultrasonic wave is different depth by using a difference amplitude variation quantity and a difference phase variation quantity. CONSTITUTION:By controlling a driving control part 16, two ultrasonic pulses of different frequencies are generated by an ultrasonic transducer, they are sent to a body to be inspected, and in a state that a harmonic component by non-linearity of a propagation of a first ultrasonic pulse can be eliminated by an adder 23, an amplitude variation quantity and a phase variation quantity by non-linearily of a propagation of a second ultrasonic pulse and the first ultrasonic pulse which are superposed in a different phase state can be derived by a variation quantity detecting part 26. Subsequently, based on above- mentioned operation, an attenuation of an ultrasonic wave or a scattering characteristic is derived from a difference amplitude variation quantity and a difference phase variation quantity being variations of these quantities between different depths by an arithmetic part 27, and displayed by a display part 29.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of Industrial Application The present invention transmits and receives ultrasonic waves within a subject, and utilizes the fact that the propagation characteristics within the subject change the characteristics of the received ultrasonic waves. The present invention relates to an ultrasonic measuring device that measures ultrasonic characteristics.

BACKGROUND OF THE INVENTION An example of a method for obtaining information inside a subject using ultrasound is a non-destructive ultrasound tomography apparatus. One method of non-destructive ultrasonic tomography equipment is the pulse reflection method, which transmits ultrasonic waves into a structure and obtains information inside the structure from the reflected waves from within the structure. The pulse reflection method uses the reflected echo intensity, that is, the amplitude value and the propagation time of ultrasonic waves, from various interfaces with acoustic impedance differences within the structure, such as non-uniform parts within the structure or imperfectly welded parts, etc. A tomographic image is obtained by collecting and displaying information inside an object two-dimensionally. However, in recent years, there has been an increasing demand for ultrasonic tomography devices, which mainly determine the shape of defects and the like within structures, to obtain information not only on the shape inside the structure but also on the quality of the materials that make up the structure.

Information regarding the quality of materials in such structures can be obtained, for example, by measuring the propagation characteristics or scattering characteristics of ultrasonic waves within the materials. When examining the ultrasonic propagation characteristics and ultrasonic scattering characteristics using the pulse reflection method, it is difficult to measure only one characteristic alone, as will be explained later. The relationship between ultrasonic propagation characteristics, especially ultrasonic attenuation characteristics and ultrasonic scattering characteristics, can be found in, for example, the Journal Opstatisti Lu Physics: Journal
of Statistical Physics, Vo
l, 36 Nos, 5/6. pages 779-786,
1984, they are closely related to each other. On the other hand, if the ultrasonic propagation characteristics and ultrasonic scattering characteristics can be obtained separately, it is possible to quantitatively understand the quality of the material, especially the quality of polycrystalline parts in metals, or defective parts in sintered bodies. become. Hereinafter, a conventional ultrasonic propagation characteristic measuring method will be explained with reference to FIG.

In FIG. 4, 1 is a subject, 2 is an ultrasonic transducer that transmits and receives ultrasonic waves to and from the subject 1, and 3 is a coupling medium that acoustically couples the subject 1 and the ultrasonic transducer 2; 4 is a container that stores the coupling medium 3; 5 is a pulse driver that drives the ultrasonic transducer 2; 6 is a preamplifier that amplifies the received signal of the ultrasonic converter 2; and 7 is a detector that detects the output of the preamplifier 6. , 8 is a scan conversion unit that stores the output of the detector 7 and forms a tomographic image; 9 is a display unit that displays the output of the scan conversion unit 8; 10
is a signal analysis section that performs analysis such as frequency analysis on the output of the preamplifier 6; the output of the signal analysis section 10 is input to the scan conversion section 8 and displayed on the display section 9.

The operation of the above configuration will be explained below.

First, a driving pulse is sent out by the pulse driver 5 and applied to the ultrasonic transducer 2, and the ultrasonic transducer 2 generates an ultrasonic pulse. The generated ultrasonic pulse propagates through the coupling medium 3 and reaches the subject l.

For the coupling medium 3, a material with low ultrasonic absorption, such as water, is used. The container 4 prevents the binding medium 3, such as water, from running away.

The specimen 1 is a part of a structure made of a cast body, and includes a heterogeneous polycrystalline portion. A part of the ultrasonic pulse that reaches the object 1 is transmitted to the object 1, and as it propagates inside the object 1, it is scattered one after another in response to changes in its acoustic quality. It travels backward along the path, that is, the acoustic scanning line, and returns to the ultrasonic transducer 2, where it is converted into a received signal. During this propagation and scattering process, the ultrasonic pulse is influenced by the acoustic quality of the object I, that is, by the ultrasonic propagation characteristics and ultrasonic scattering characteristics. The received signal is amplified by a preamplifier 4, its output is detected by a detector 7, the output of the detector 7 is stored and scan-converted by a scan converter 8, and the output of the scan converter 8 is configured on a standard TV monitor or the like. is displayed on the display section 9. On the other hand, the output of the preamplifier 4 is sent to the signal analysis section 1.
At 0, signal analysis such as frequency analysis is performed, and propagation characteristics or scattering characteristics are calculated. The attenuation characteristic among the propagation characteristics is determined by the following calculation. First, the received signal h (
几l) and the received signal h (R2) corresponding to the depth R2 are extracted. For example, set the length of the signal to be extracted to 5 mm within the subject 1.
shall be. If the length of the signal to be extracted is Imm and the corresponding gate width is 18, then T=2・bnow −・・−・−
(+) However, ■; Speed of sound Km/see Therefore, in order to determine the gate width, the value of the speed of sound V must be known. It is necessary to prepare data for the value of the sound velocity V in advance for each material. Next, frequency analysis such as Fourier transform is performed on the received signals h(R1) and h(R2).

If the Fourier transform of h (几1) is) (1(ω) and the Fourier transform of h (几2) is I]2(ω), and ω is the angular frequency, then H1(ω) and R2(ω) are expressed as follows: It can be expressed as

1-11(ω)=T(Gl G 1(ω)・S 1 (
ω) --(2)112(ω)-T(ω)・
G2(ω)・82(ω)...1 direct 3) However, T(ω) is the frequency characteristic of the ultrasonic pulse transmitted and received by the ultrasonic transducer 2, and Gl(ω) is the frequency characteristic between the ultrasonic transducer 2 and the subject. The propagation characteristic that the ultrasonic wave undergoes when reciprocating between the depths ≧l and si(ω) is the most turbulent characteristic of the ultrasonic wave at the depth nl. As is clear from this equation, the received signal includes the ultrasonic propagation characteristic and the ultrasonic scattering characteristic in the form of a product, and it is difficult to obtain each in separate form. However, if the scattering characteristics S1(ω) and 82(ω) are equal, then (2)
, By determining the ratio of equation (3), the depth R of the object
A propagation characteristic G21(ω) between depth R1 and depth R2 is obtained.

G21(ω)=G2(ω)/Gl(ω)=H2(ωl/
H1(ω) (4) The absolute value of the propagation characteristic 021 corresponds to the ultrasonic attenuation characteristic. In this way, it is possible to obtain the propagation characteristics of ultrasonic waves in a region of arbitrary depth within the subject 1.

Therefore, it is also possible to obtain the propagation characteristic C)1(ω) between the surface of the object 1 and the depth R1, and by using equation (2), it is also possible to obtain the scattering characteristic 81(ω). .

However, if the object l is composed of inhomogeneous scatterers, the ultrasonic scattering characteristics will vary greatly depending on the part, and it is not possible to assume that 81(ω) and 82(ω) are equal as described above. Can not. For this reason, it has been conventional to take advantage of the fact that the ultrasonic scattering characteristics randomly change depending on the region to be examined.

That is, the position at which the ultrasonic transducer 2 transmits and receives ultrasonic waves to and from the subject 1 is moved within a predetermined range in a direction parallel to the surface of the subject 1, and the received signals obtained at many parts are By performing frequency analysis on each of these and averaging a large number of obtained frequency analysis results, only randomly changing scattering characteristics are canceled out. Thus the averaged Fourier transform! Equation (4) can be applied to 11(ω) and 02(ω), making it possible to obtain propagation characteristics.

Problems to be Solved by the Invention However, with the above configuration, when the measurement site is shifted, the scattering characteristics of the ultrasound waves within the object 1 change completely randomly, that is, between each measurement site. The assumption is that there is no correlation at all.

However, there is a problem in that this assumption no longer holds true due to an interface with a clear acoustic boundary that exists within the subject.

The present invention solves the above-mentioned problems of the prior art, and aims to accurately measure the ultrasonic absorption characteristics of a subject having arbitrary ultrasonic scattering characteristics.

Means for Solving the Problem The present invention uses two ultrasonic pulses of different frequencies, namely a first ultrasonic pulse and a second ultrasonic pulse (having a higher center frequency than the first ultrasonic pulse). Four sets of ultrasonic pulses, namely, the second ultrasonic sphere pulse and the second ultrasonic pulse are superimposed on the part of the first ultrasonic pulse where the particle velocity is near zero and the particle acceleration direction is constant (phase state C and ), a second ultrasonic pulse is superimposed on the particle velocity peak portion of the first ultrasonic pulse (described as phase state), the first ultrasonic pulse is created, and these are transmitted to the subject. death,
Frequency analysis is performed on the difference data from which the harmonic components of the first ultrasonic pulse have also been removed, and the amount of amplitude change and phase change is determined. From these values, the attenuation or scattering characteristics of the ultrasonic wave between different depths are determined. The above objective is achieved by determining the following and displaying it on the display unit.

Effect of the Invention With the above configuration, the present invention allows the second ultrasonic pulse and the first ultrasonic pulse to be superimposed in different phase states in a state where harmonic components due to nonlinearity of propagation of the first ultrasonic pulse can be removed. Find the amplitude change and phase change due to the nonlinearity of propagation, and calculate the attenuation of the ultrasonic wave from the difference amplitude change and differential phase change, which are the changes in these amounts between different depths.
Alternatively, the scattering characteristics are determined and displayed.

Example Embodiments of the present invention will be described in detail below with reference to the drawings.

FIG. 1 is a functional block diagram showing an ultrasonic measuring device according to an embodiment of the present invention. In Figure 1(a), 12
13 is a first ultrasonic transducer that sends out a first ultrasonic pulse in a low frequency band, and 13 is a second ultrasonic converter that sends out a second ultrasonic pulse with a higher frequency than the first ultrasonic pulse. ,1
4 is a coupling medium that acoustically couples the subject 11 and the ultrasonic transducers 12 and 13; 15 is a container that stores the coupling medium 14; and 16 is a first ultrasonic transducer 12 and a second ultrasonic transducer. This is a control drive unit that drives the device 13 in a phase controlled manner. A more detailed functional block diagram of the inside of the control drive section 16 is shown in FIG.
) is shown.

FIG. 1 (in bl, 161 is the first ultrasonic transducer 12
162 is a pulse driver that drives the second ultrasonic transducer 13, 163 is a pulse driver 1
This is a phase control unit that controls the difference in pulse generation timing between phase signals 61 and 162. Pulse drivers 161 and 162
The control drive section 16 is composed of the phase control section 163 and the phase control section 163 .

Returning to FIG. 1(a), 17 is a signal source that generates a system clock, 18 is a preamplifier that amplifies the received signal from the second ultrasonic transducer 13, and 19 is a variable gain that amplifies the output signal of the preamplifier 18. amp, 20 is amp 19
an A/D converter that converts the output signal of the into digital data, 2
1 is a first buffer memory that stores output data of the A/D converter 20, 22 is a second buffer memory that stores output data of the A/D converter 20, and 23 is stored in buffer memories 22 and 21. 24 is a memory that stores the difference data that is the output of the adder 23; 25 is a transfer function calculation for the data string of the difference data stored in the memory 24; 26 is a change amount detection unit that detects the amount of amplitude change and the amount of phase change with respect to the amplitude data A, which is the first output, and the phase data P, which is the second output, of the transfer function calculation unit 25. It is.

A more detailed functional block diagram inside the change amount detection unit 26 is shown in FIG. 1 (C1).
．． 262 is a memory for storing amplitude data A of the transfer function calculation section 25; 263. 264 is a memory that stores the phase data P of the transfer function calculation unit 26; 265 is a memory 261;
, 262 is an amplitude change analysis unit that analyzes the amount of amplitude change on the data stored in the memory 263. 26
This is a phase change analysis unit that analyzes the amount of phase change with respect to the data stored in 4. The output data ΔA of the amplitude change analysis section 265 is stored in the memory 267, and the output data ΔA of the amplitude change analysis section 265 is stored in the memory 267.
66 output data ΔI) is stored in memory 268.

Memo IJ 261, 262゜263, 264.
267, 268. The amplitude change analysis section 265 and the phase change analysis section 266 constitute the change amount detection section 26.

Returning to Fig. 1 (ta), 27 is a characteristic calculation unit that receives the output data ΔA and ΔP of the change amount detection unit and calculates the ultrasonic characteristics, and 28 stores and scan-converts the output of the characteristic calculation unit 27. A scan converter, 29 is a display unit that displays the output of the scan converter 28, 30 is a signal processor that processes the output signal of the preamplifier 18, and the output of the signal processor 30 is the scan converter 2.
8, the data is stored and converted to form a tomographic image. 31 is a main control unit that controls the entire system.

The operation of the above configuration will be explained below.

First, an example of the second ultrasonic pulse outputted by the second ultrasonic transducer 13 is shown in FIG.
Figure 2(b) shows an example of the first ultrasonic pulse output output by
FIG. 2(C) shows an example of the ultrasonic pulse outputs of the ultrasonic transducers 12 and 13 superimposed in phase state C.
An example of the ultrasonic pulse outputs of the ultrasonic transducer 12 and the ultrasonic transducer 13 superimposed in phase states is shown in FIG. 2(d). The center frequency of the first ultrasonic pulse is, for example, 0
．． The center frequency of the 5 MHz1 second ultrasonic pulse is, for example, 7.5 MHz, and values that are significantly different from each other are selected for the center frequencies. In phase state C, the center of gravity of the waveform of the second ultrasonic pulse is such that the particle velocity of the first ultrasonic pulse is near zero;
And the value changes from negative to positive, that is, the particle acceleration is superimposed at a positive timing. In the phase state, the waveform center of gravity of the second ultrasonic pulse is superimposed at the timing when the particle velocity of the first ultrasonic pulse reaches its peak value.

Regarding the waveforms of the first ultrasonic pulse and the second ultrasonic pulse, when the wavelength of the first ultrasonic pulse is A and the pulse length of the second ultrasonic pulse is t, 2・[< Δ and It is desirable to do so. This relationship facilitates analysis of the amount of change in amplitude and the amount of phase change in the transfer function of the second ultrasonic pulse.

Next, how the second ultrasonic pulse and the ultrasonic pulses superimposed in phase states C and D propagate within the subject 11 will be described in detail. It is known that even at peak ultrasonic output levels used in ordinary ultrasonic testing equipment, ultrasonic waves are distorted due to nonlinear propagation phenomena. Although the mechanism of the occurrence of this nonlinear propagation phenomenon differs between fluids and solids, it is possible to treat it in the same way by focusing only on the result that distortion occurs, so here we will focus on the mechanism in fluids that is easy to explain. The propagation of ultrasonic waves will be explained below.

The nonlinear phenomenon of ultrasonic propagation in a fluid can be explained by the fact that the propagation speed of ultrasonic waves differs between the peaks and valleys of the waveform. This relationship is expressed by the following equation.

B C=C, ±(10-(-)) -u =Om±Δo
--(5) 2 people Here, B/A is a nonlinear parameter of the propagation medium, and varies depending on the type of fluid, but for example, for water, it has a value of about 6. C0 is the phase velocity of infinite-small amplitude ultrasound, and U is the particle velocity. In the case of ultrasonic wave P+7-IWz-, the particle velocity U is 12 an/sec in water, and ΔC is 50/see. FIG. 3 shows the influence of this nonlinear propagation phenomenon on the waveform of the ultrasonic wave. Figure 3(a) shows how the first ultrasonic pulse is distorted due to the nonlinear phenomenon of propagation, and Figure 3(b) and (C1) show how the first ultrasonic pulse is distorted due to the nonlinear phenomenon of propagation. This shows how the frequency characteristics of the ultrasonic pulse change. In Fig. 3(b), the center frequency of the second ultrasonic pulse superimposed in phase state C shifts to the high frequency side as it propagates, and Fig. 3(b) shows how the frequency characteristics of the ultrasonic pulse change. ) shows how the phase of the second ultrasonic pulse superimposed in a phase state shifts with propagation. The phase difference between the second ultrasonic pulse when the first ultrasonic pulse is superimposed and when it is not superimposed, that is, the amount of phase change ΔP, is expressed by the following formula: Can be expressed.

△E=2・ΔX・ω・(−−−) ・・・・・・
・(6) C0C・+ΔC Phase velocity C・in water is 1500 m/sec, propagation distance △x is 5 mm, angular frequency ω is 2 tt x 7.5
If the formula is X 10'rad/', △P is 0.10rad
(= 6.Odeg), and it is possible to detect with sufficient accuracy. Such waveform distortion of ultrasonic waves can be caused even in solids.

Each ultrasonic pulse waveform shown in FIG. 2 is (b) first ultrasonic pulse, (C1 phase state C1 (d) phase state D,
) The process in which the second ultrasonic pulses are transmitted to the subject 40 in one cycle and the received signals are processed will be described below. First, when the transmission of the ultrasonic transducer 13 is stopped, the first ultrasonic pulse generated from the ultrasonic transducer 12 passes through the coupling medium 14 and reaches and enters the subject 11 .

The first ultrasonic pulse accumulates distortion due to nonlinear effects while propagating through the coupling medium 14 and the subject 11, increasing harmonic components. At the same time, the waves are scattered one after another in response to changes in the acoustic quality of the object 11, and some of them reach the ultrasonic transducer 13, and some of the band components among the harmonic components are converted into received signals. Ru. This received signal PS will be used later when obtaining difference data. The received signal is amplified by 8/N by a preamplifier 18, and then amplified to a predetermined amplitude by a variable gain amplifier 19. The output of the amplifier 19 is converted into digital data by an A/D converter 20, and data corresponding to the received signal ES is stored in a first buffer memory 21. The sampling timing of the A/D converter 20 must be precisely synchronized with the control driver 16, the sampling rate must be several tens of MHz, the resolution must be approximately 10 bits or more, and the phase of the input signal must be accurately preserved.

Next, the first ultrasonic pulse and the second ultrasonic pulse are sent to the subject 11 in phase state C. The state of propagation while being superimposed in phase state C can be approximated as follows. The propagation path can be regarded as a collection of minute sections, and in each minute section, the superimposed ultrasonic pulse causes propagation distortion based on a nonlinear phenomenon, and the center frequency of the second ultrasonic pulse changes to the high frequency side. This amount of change depends on both the particle velocity U in the section of interest and the nonlinear parameter B/A of the propagation medium. In this way, the second ultrasonic pulse is subject to excessive attenuation due to its center frequency changing to the higher frequency side. This excessive attenuation is a value that also depends on the attenuation constant of the propagation medium. As described above, the ultrasonic pulse propagates while being successively scattered while maintaining the phase state C while repeating nonlinear propagation distortion and distortion due to attenuation in each minute section. While being scattered and traveling backwards along the propagation path, the amplitude of the ultrasound pulse is so small that nonlinear effects can be ignored. The received signal in phase state C is assumed to be O8.

Next, the first ultrasonic pulse and the second ultrasonic pulse are transmitted to the subject 11 in a phased manner. When the second ultrasonic pulse propagates in a phase state, it can be approximated that the second ultrasonic pulse undergoes only a phase change as a propagation distortion based on a nonlinear effect.

The amplitude of the scattered ultrasound pulse traveling backwards along the propagation path is so small that nonlinear effects can be ignored. Let the received signal in the phase state be DS.

Then, at the end of one cycle, the ultrasound transducer 12 is stopped and only the second ultrasound pulse is sent to the subject 11. Let SS be the received signal obtained by the second ultrasonic pulse. The above are the ultrasonic pulses sent to the subject 11 during one cycle. Data corresponding to the received signals aS%DS and SS are stored in the second backup memory 22. The first 3 of the data stored in memory 21.22
Regarding the received signals PS, O8, and DS, difference data CD and DD are calculated by the adder 23 as shown in the following equations and stored in the memory 24.

The difference data CD and DD can be considered as a portion related to the probe wave in the nonlinear propagation distortion of the superimposed ultrasonic pulse.

Next, the transfer function calculation unit 25 extracts the data from the buffer memory 22 and memory 24 and performs calculations such as frequency analysis. Specifically, the calculations are spectral amplitude calculations and phase angle calculations, which are obtained by executing calculation algorithms such as 7-tier integration and DFT (discrete Fourier transform). The amplitude spectrum and phase angle are calculated as follows. First, regarding the data DS obtained when only the second ultrasonic wave is transmitted,
A data string corresponding to a specific depth R1 within the subject 11 is extracted from the buffer memory 22, frequency analysis is performed, and a Fourier transform H1(ω) is obtained. Similarly, the data string corresponding to the depth 2 is extracted from the buffer memory 22 to obtain the Fourier transform 1(2(ω). The length of the extracted data is, for example, 5 mm within the subject 11, which is converted into time. It is about 65μ type.

The amplitude spectrum Al(ω) is the absolute value of the Fourier transform H1(ω), and the phase angle PI(ω) is the Fourier transform H1(ω).
The phase angle of ω) can be obtained from the following equation.

Al(ω)=lH1(ω)1...
...(8) P l (ωl=arg, (141(
ω)) --(9) Amplitude spectrum Al(ω) and phase angle PI(ω) obtained in this way
is affected by the frequency characteristics of the scattering of the scatterer in the object 11, and if these data are used as they are, the
It is difficult to accurately obtain the ultrasonic attenuation characteristics and the like that No. 1 has. For the next processing, the amplitude spectrum Al(ω) corresponding to depth R1 and the amplitude spectrum A corresponding to depth R2
2(ω) is the memory 261, and the phase angle corresponding to the depth R1 and the phase angle P2(ω) corresponding to the depth R2 are the memory 263.
is memorized.

Depth R of difference data CD of received signals obtained in phase state C
Amplitude spectrum AOI (ω) corresponding to 1 and depth R・2
The amplitude spectrum AO2(ω) corresponding to is stored in the memory 262
The phase angle PDI (ω) corresponding to the depth 1 of the received signal difference data DD stored in the phase state and obtained in the phase state and the depth R
The phase angle PD2(ω) corresponding to 2 is stored in the memory 264.

Next, the difference between the phase angle obtained when the ultrasonic transducer 12 is stopped and the phase angle obtained in the phase state, that is, the amount of phase change ΔP.

△P 1 (ωl= P D 1 (ω) −P 1
(ω) −−QOΔP 2(ω)= P D
2(ω) −P 2(ω) −−(11)
and the difference in phase change between depth R2 and depth rtl, that is, the differential phase change amount △φ, Δφ=△P2(ω)−ΔPl(ω) ・Old・
- (2) is the memory 263. 264. 268 and the phase change analysis section 266. Differential phase change amount Δ
φ is stored in memory 268.

Next, the change in the amplitude spectrum obtained when the ultrasonic transducer 12 is stopped and the amplitude spectrum obtained in phase state C, that is, the amplitude change amount ΔA, ΔAl(ω)=AO1(
ω)/Al(ω) ・・River・(To)ΔA2(ω
)=AC2(ω)/A2(ω) ・Old・・CI
4 and the change in amplitude change ΔA at depth R1 and depth 2, that is, the difference amplitude change Δα, Δα=ΔA2(ω)
/ΔAl(ω)...(g) is the memory 261. 262. 267 and amplitude change analysis section 265
Calculated using The differential amplitude change amount is stored in memory 267. This amplitude change amount ΔAl(ω) is determined by using the propagation characteristic G′1(ω) in phase state C.
)=lG'l(ω)/Gl(ω)1 ・・・・・・
・It can be expressed as QtI. In the G1 equation, the ultrasonic scattering characteristic 81(ω) in the equation (2) is eliminated.

On the other hand, the difference amplitude change amount Δα is α5. Using the an equation, we calculate the attenuation G21(ω) that the ultrasonic wave receives between depth R1 and depth 1%2, and the attenuation G'21(ω) in phase state C.
) can be expressed as the following formula.

G'2(ω)/(12(ω) G'21(ω)
,,, ,,,αηGl(ωl/Gl(ω)
G21fω) This differential amplitude change amount Δα is determined by the attenuation of the ultrasonic wave between depth R1 and depth 2, the particle velocity U of the first ultrasonic pulse, and the nonlinear parameter B/ of the propagation medium.
This is the amount determined by A. The product of the particle velocity U and the nonlinear parameter I3/A can be expressed by the differential phase change amount Δφ.

Therefore, the differential amplitude change amount Δα can be determined from the ultrasonic attenuation G and the differential phase change amount Δda. Using this relationship, it is possible to conversely determine the attenuation G of the ultrasonic wave from the differential amplitude change amount Δα and the differential phase change amount Δφ. The characteristic calculation unit 27 calculates the differential amplitude change amount Δα stored in the memory 267 and the differential phase change amount Δ stored in the memory 268.
The ultrasonic attenuation value G is determined from the value of φ. Once the value of the ultrasonic attenuation G is determined, the scattering characteristic S of the ultrasonic wave can be calculated using equation (2).
It becomes possible to find. The attenuation or scattering characteristics obtained by the characteristic calculation section 27 are stored in the scan conversion section 28 and displayed on the display section 29. The output of a signal processing section 30 that performs logarithmic amplification, envelope detection, etc. on the output of the preamplifier 18 is connected to the scan conversion section 28, and a tomographic image can also be formed. Control of the state of the control drive unit 16 as described above,
The main control unit 31 controls instructions for writing or reading from the memory, execution of various calculations, and the like.

As is clear from the above description, according to this embodiment, after changing the state of the output of the drive control 16 and removing harmonic components generated by the first ultrasonic wave itself from the received signal from the subject, the differential phase is changed. By determining the amount and the amount of difference amplitude change, it is possible to determine the attenuation or scattering characteristics of the ultrasonic wave.

In addition, in the above embodiment, the ultrasonic transducer 12. Although i3 has been described as a stop for explanation, it may be arranged on a concentric axis. These ultrasonic transducers 12 and 13 may be scanned linearly or mechanically in sectors or the like. Further, the ultrasonic transducers 12 and 13 may be constructed of arrayed transducers.

Furthermore, it is also possible to automatically set the position from which the data of the received signal is extracted in the depth direction of the object or in a direction perpendicular to the depth direction to obtain a tomographic image of the attenuation characteristic distribution.

The objects to be examined include not only structures made of various solids and fluids that are subject to non-destructive testing, but also various biological tissues, such as the condition of livestock meat, and in the medical field, especially liver diseases, etc., which are subject to ultrasonic attenuation, scattering, etc. It can also be applied to quantify the degree of progression of closely related diseases.

This measurement method can also be applied to obtain other acoustic parameters, such as nonlinear parameters.

Effects of the Invention As described above, the present invention has the following advantages:
Utilizing the nonlinear propagation phenomenon that occurs when the first ultrasonic pulse is superimposed, harmonic components generated by the first ultrasonic wave itself are removed from the received signal, and then the amount of amplitude change and the amount of phase change are The depth detection is calculated, and the difference amplitude change amount and the difference phase change amount, which are changes in these values between different depths, are used to obtain the attenuation of ultrasonic waves between different depths, etc., and the received signal is Even when the method is influenced by the frequency characteristics of scatterers in the object, accurate information regarding the attenuation of ultrasound can be obtained, and the effect is significant.

[Brief explanation of the drawing]

FIGS. 1(a) to (C) are functional block diagrams of an ultrasonic measuring device in an embodiment of the present description, and FIGS. 2(a) to (d+ are outputs of an ultrasonic transducer in an embodiment of the present invention) waveform diagram,
FIGS. 3(a) to 3(C) are diagrams of ultrasonic pulse waveforms distorted by nonlinear propagation phenomena, and FIG. 4 is a functional block diagram showing conventional ultrasonic attenuation characteristic measurement. 12, 13... Ultrasonic conversion unit, 16... Control drive unit, 23... Adder, 25... Transfer function calculation unit, 26
... Change amount analysis section, 27... Characteristic calculation section. Name of agent Patent attorney Satoshi Nakao and 1 other person 1
1ヱ4 L -, -1111-JFigure 2 74 3 m □ii2SmotodaN Figure 4

Claims (1)

[Claims] a first ultrasonic transducer that transmits a first ultrasonic pulse;
a second ultrasonic transducer that sends out a second ultrasonic pulse having a higher frequency than the first ultrasonic pulse; a control drive unit that drives the first and second ultrasonic transducers in phase control;
a calculation means for obtaining difference data of ultrasonic reception signals corresponding to on and off states of the second ultrasonic transducer when the first ultrasonic transducer is in the on state, and calculating a transfer function using the difference data. a transfer function calculation unit that performs calculations, a change amount analysis unit that detects an amplitude change amount and a phase change amount based on the results of the transfer function calculation unit, and an ultrasonic characteristic that is determined from the amplitude change amount and phase change amount. An ultrasonic measuring device comprising: a display section for displaying information.