JPH02134146A - Ultrasonic non-linear parameter measuring device - Google Patents

Abstract

PURPOSE:To improve the measuring accuracy of an ultrasonic nonlinear parame ter by medium filter processing by cutting out portions corresponding to plural arbitrary parts of a measured medium from two kinds of measuring wave signals received in the cases where a pump wave exists and where no pump wave exists, detecting orthogonal waves, and obtaining a phase difference to calculate an ultrasonic non-linear parameter. CONSTITUTION:Measuring wave ultrasonic pulse and a pump wave are transmit ted top a measured medium 21 by ultrasonic vibrators 4, 5 and a time gate 8 cuts out portions corresponding to plural arbitrary parts of a measured medi um 21 from a measuring wave signal received by the ultrasonic vibrator 5 and inputs same to an orthogonal wave detection circuit 22 to detect the orthogo nal wave. According to the detected orthogonal real components and imaginary components, a phase difference is obtained to measure ultrasonic non-linear parameter.

Description

[Detailed Description of the Invention] (Summary) Regarding a measuring device that measures ultrasonic nonlinear parameters of a medium to be measured, orthogonal detection is performed only on a plurality of arbitrary parts from a received measurement wave signal, and orthogonality detection is performed on only a plurality of arbitrary parts of the measurement wave signal. The purpose of this method is to obtain ultrasonic nonlinear parameters from phase differences, etc., after avoiding any influence on the signal after detection, and to improve the measurement accuracy of ultrasonic nonlinear parameters through median filter processing. An ultrasonic transducer that transmits ultrasonic pulses for measurement waves of high frequency and low sound pressure and receives reflected measurement waves; and an ultrasonic transducer that transmits pump waves of low frequency and high sound pressure to the medium to be measured. , after cutting out parts corresponding to a plurality of arbitrary parts in the medium to be measured from the measurement wave signal received by the ultrasonic transducer, orthogonal detection is performed, or the measurement wave (for No. 3) orthogonal detection by supplying a reference signal for orthogonal detection and a signal with a 90° phase difference when the part corresponds to an arbitrary part,
Regarding the real component and imaginary component after this orthogonal detection, find both when the ultrasonic pulse for the measurement wave is superimposed on the pump wave and when only the ultrasonic pulse for the measurement wave is transmitted, or when the ultrasonic pulse for the measurement wave is transmitted. Superimpose the ultrasonic pulse for the measurement wave on the pump wave. Obtain both when changing the position on the pump wave and transmit. Based on either of these, ultrasonic nonlinearity of multiple arbitrary parts in the medium to be measured is calculated. Configure to measure parameters.

[Industrial application field]

The present invention relates to a measuring device for measuring ultrasonic nonlinear parameters of a medium to be measured. Taking advantage of the non-linear property that the sound velocity against biological tissue, etc., is a constant value in the first-order range relative to the sound pressure, but is proportional to the sound pressure in the second-order range and beyond, It is desired to accurately measure the nonlinearity parameters of a medium.

``Problems to be solved by conventional techniques and inventions'' Conventionally, as a method (for example, Japanese Patent Application Laid-Open No. 119926/1983) for determining the nonlinearity parameters of a medium to be measured such as a living body (111Th), as shown in Fig. 12 (al), At the same time, a pump wave of low frequency and high sound pressure is transmitted to the constant medium of I11, and (kl+
, as shown in (c), a high frequency and low sound pressure measurement wave ultrasonic pulse is transmitted to the measured medium at the positive and negative maximum value portions of this pump wave, and the phase difference between the two reflected measurement waves is determined. was measured, and the phase shift parameter N and B/A, which are ultrasonic nonlinear variables in the medium to be measured, were determined. Furthermore, the phase difference between the reflected measurement waves when the pump wave is transmitted to the medium to be measured and when the pump wave is not transmitted is measured to determine the ultrasound parameters.

However, in this conventional method, when calculating the phase difference between the two reflected measurement waves, for example, as shown in FIG. Since the phase difference between the two measured waves was calculated continuously, as shown in the analysis values (a, 3) of Figure 13 (a), the phase of the measured wave was t.
, tl+q There is a problem where the analysis value (phase shift amount) changes significantly due to the influence of the part, and it is not possible to measure (estimate) with good accuracy. 1st
Fig. 3 (a) A conventional example will be briefly explained.

In FIG. 13(a), (a, l) show the positional relationship between the measurement wave I transducer and the scatterer (measurement medium). Point A and point B in the scatterer are the locations where the amount of phase shift is now to be determined. In addition to the measurement wave transducer, a transducer (not shown) is provided which transmits a low frequency, high sound pressure pump wave to the scatterer.

(a, 2) shows a measurement wave measured by a measurement wave transducer.

(a, 3) shows the phase shift i Y ML of the measurement wave shown in (a, 2) and the measurement wave when the measurement wave ultrasonic pulse is superimposed on the pump wave. The solid line is the calculated analytical value, and the dotted line is the theoretical value. As mentioned above, this analytical value has a problem in that it cannot be obtained with good accuracy because it is distorted by the influence of the part where the phase of the measurement wave (a, 2) is steep. After performing orthogonal detection on multiple arbitrary parts of the measured wave signal to avoid the influence of the steep phase part of the measured wave on the signal after orthogonal detection, ultrasonic nonlinear parameters are determined from the phase difference, etc., and the median filter is applied. The purpose is to improve the measurement accuracy of ultrasonic nonlinear parameters through processing.

[Means to solve problems]

Means for solving the problem will be explained with reference to FIGS. 1, 4, and 13 (b).

In FIG. 1, an ultrasonic transducer 4 transmits a pump wave of low frequency and high sound pressure to a medium 21 to be measured.

The ultrasonic transducer 5 transmits a measurement wave ultrasonic pulse of high frequency and low sound pressure to the medium 21 to be measured, and receives the reflected measurement wave.

The time gate 8 cuts out portions corresponding to a plurality of arbitrary locations in the medium 21 to be measured from the measurement wave signal received by the ultrasonic transducer 5 .

The time gate 9-1.9-2 includes a reference signal 90 for orthogonally detecting the measurement wave signal received by the ultrasonic transducer 5 at a portion corresponding to a plurality of arbitrary parts in the medium 21 to be measured. °The quadrature detection circuit 22 detects signals with different phases.
It is intended to supply

The calculation unit 19 calculates phase differences and the like based on the imaginary components and real components orthogonally detected by the orthogonal detection circuit 22, and measures ultrasonic nonlinear parameters.

[Effect]

As shown in FIG. 1, FIG. 4, and FIG. The gate 8 cuts out portions corresponding to a plurality of arbitrary locations in the medium to be measured 21 from the measurement wave signal received by the ultrasonic transducer 5 and inputs them to the orthogonal detection circuit 22, or time gate 9-1.9-2. is the measured medium 2 for the measurement wave signal.
A reference signal for orthogonal detection and a signal having a different 90' phase is input to the orthogonal detection circuit 22, and orthogonal detection is performed (Fig. 13 (b)).
(see (b, 2)). Based on these orthogonally detected real and imaginary components, phase differences and the like are determined to measure ultrasonic nonlinear parameters (see (b, 3) in FIG. 13(b)).

Therefore, for example, the received 2
By cutting out parts corresponding to a plurality of arbitrary parts in the medium 21 to be measured from the seed measurement wave signal and performing orthogonal detection to obtain the phase difference, the influence of the part where the phase of the measurement wave is steep is avoided, and median filter processing is also performed. By doing so, it becomes possible to obtain estimated values of nonlinear parameters with good accuracy.

〔Example〕

First, the configuration and operation of one embodiment of the present invention will be explained using FIGS. 1 and 2.

In FIG. 1, a timing generator 1 generates a timing signal etc. that controls the transmission timing of the pump wave emitted by the ultrasonic transducer 4 and the measurement wave ultrasonic pulse emitted by the ultrasonic transducer 5. It is something. For example, Figure 2 (
a) represents a timing signal for transmitting an ultrasonic pulse for a measurement wave, and FIG. 2 tb) represents a timing signal for transmitting a pump wave.

The pump wave transmitting circuit 2 is a circuit that transmits a pump wave of low frequency and high sound pressure from the ultrasonic transducer 4 in response to the timing signal input from the timing generator 1 (FIG. 2(b)). .

The measurement wave transmission circuit 3 causes the ultrasonic transducer 5 to transmit ultrasonic pulses for measurement waves of high frequency and low sound pressure in response to the timing signal input from the timing generator 1 (FIG. 2(a)). It is a circuit.

The ultrasonic transducer 4 transmits a pump wave of low frequency and high sound pressure toward the medium 21 to be measured.

The ultrasonic transducer 5 transmits a measurement wave ultrasonic pulse of high frequency and low sound pressure toward the medium 21 to be measured, and receives the reflected measurement wave.

The preamplifier 6 amplifies the received measurement wave signal.

BPF (band pass filter) 7 is a filter that removes low frequency components and noise components of pump waves. This B
The waveform after being filtered by PF7 is shown in FIG. 2(C).

The time gate 8 is a circuit that cuts out signals corresponding to a plurality of arbitrary portions in the medium 21 to be measured from the measurement wave signal filtered by the BPF 7 . For example, by gate signals A and B shown in FIG. 2 (dl), the measured medium 2
The measurement wave signals reflected and received from parts A and B in 1 are cut out (Fig. 2(e)).

The reference signal 10 is SINω supplied to the quadrature detection circuit 22.
This is the signal of t.

The 90° phase shifter 11 generates a CO3ωt signal by shifting the phase of the reference signal StNωt by 90°.

The quadrature detection circuit 22 includes a multiplier 12.15, an LPF (low pass filter) 13.16, and a time gate 8.
Figure 2 (received waveform of el (measurement wave signal)
are multiplied by SINωt or CO8ωt by multiplier 12.15, and orthogonal detection is performed to obtain the result shown in Fig. 2ff.
) A sine component (imaginary component) and a cosine component (real component) are generated.
ASI and BSI in the middle indicate the sine components of the orthogonal detection signals in the media A and B under test when no pump wave is transmitted, respectively, The cosine components in media A and B are respectively shown. Also, AS2 and BS2 in FIG. Figure 2 +g
AC2 and BO2 in l indicate cosine components in the measurement medium A and B, respectively, when the ultrasonic pulse for measurement wave is superimposed on the pump wave.

LPF (low pass filter) 13.16 is a filter that removes high frequency components equal to or higher than the 2ω component.

ADC (analog-to-digital converter) 14.17 converts the sine component and cosine component after orthogonal detection into digital values, respectively.

The memory 18 stores the sine and cosine components converted into digital values by the ADCs 14 and 17.

The calculation unit 19 calculates a point A, a phase shift position type A at the point A,
V, which will be described later, is calculated using the formula α or formula (20+), and the phase shift parameter N between points A and B is calculated using the formula 051, which will be described later.This calculated phase shift The parameter N is stored in the display memory 20 and displayed on the display.The ultrasonic transducer 4.5 is scanned two-dimensionally with respect to the medium 21 to be measured to spatially display the phase shift parameter. The image is stored in the memory 20 and displayed as an image on the display.

FIG. 2 shows an explanatory diagram of the operation of the configuration shown in FIG.

In FIG. 2, fal indicates the transmission timing of the measurement wave. This is from the ultrasonic transducer 5 to the medium to be measured 2 in FIG.
1 represents the transmission timing of the measurement wave ultrasonic pulse transmitted at 1.

(bl indicates the transmission timing of the pump wave. This is
FIG. 1 represents the transmission timing of a pump wave transmitted from the ultrasonic transducer 4 to the medium 21 to be measured.

(C1 indicates the received waveform (waveform of the measurement wave).

(di indicates a gate signal. This is a gate signal used by the time gate 8 in FIG. 1 to extract signals corresponding to points A and B in the medium to be measured 21 from the received measurement wave signal. It is.

(e) shows the received waveform (measurement wave No. 13) after the gate. This represents the measurement wave signal extracted from the received measurement wave signal by the time gate 8 in FIG.

ffl indicates the sine component after orthogonal detection. This includes the multiplier 12 and the LPF that constitute the orthogonal detection circuit 22 in FIG.
represents the sine component (imaginary component) generated by l3.

fgl indicates a cosine component after orthogonal detection. this is,
Multiplier 15 and LPF constituting quadrature detection circuit 22 in FIG.
represents a cosine component (real number component) generated by 16.

FIG. 3 shows an example of a signal after orthogonal detection.

In FIG. 3, regarding "the amplitude of the signal after quadrature detection of the received signal when there is no pump wave" and "the amplitude of the signal after quadrature detection of the received signal when there is a pump wave", "SINω
The values obtained when multiplied by [1] and "multiplied by CO3ωt" are stored, and these are converted into γ, 1 as shown in the figure.
, γゎiTsz, γ. However, in the figure, ■ indicates the received signal strength, and 1 indicates the reference signal strength.

FIG. 4 shows another embodiment configuration in which time gates 9-1 and 9-2 are provided in place of the time gate 8 shown in FIG. FIG. 5 shows an explanatory diagram of the operation of the configuration shown in FIG.

This configuration in FIG.
The signal is supplied only when it corresponds to the part of the measurement wave signal reflected and received from point B. As a result, the SIN as shown in Fig. 5(e) and (fl)
ωt and CO8ωt are supplied to the quadrature detection circuit 22 to generate sine and cosine components after quadrature detection as shown in FIG.

FIG. 5 shows an explanatory diagram of the operation of the configuration shown in FIG.

In FIG. 5, (al) indicates the transmission timing of the measurement wave.
1 represents the transmission timing of the ultrasonic pulse for the measurement wave transmitted toward 1.

4) indicates the transmission timing of the pump wave. This represents the transmission timing of the pump wave transmitted from the ultrasonic transducer 4 in FIG. 4 toward the medium 21 to be measured.

(C1 indicates the received waveform (waveform of the measurement wave).

(d) shows the gate signal, which means that the time gates 9-1 and 9-2 in FIG. This is a gate signal to be supplied to the detection circuit 22.

Tel is the sign component of the gated reference signal.

This is the SINωt signal supplied from the time gate 9-1 in FIG. 4 to the multiplier 12.

ffl is the cosine component of the gated reference signal.

This is the signal of CO8ωt supplied from the time gate 9-2 in FIG. 4 to the multiplier 15.

fgl indicates a sine component after orthogonal detection. This is the multiplier 12 and LPF 1 that constitute the orthogonal detection circuit 22 in FIG.
represents the sine component (imaginary component) generated by 3.

(hl indicates the cosine component after orthogonal detection. This is
FIG. 4 Multiplier 15 and LPF constituting quadrature detection circuit 22
represents a cosine component (real number component) generated by 16.

FIG. 6 shows an example of a differential amplifier circuit according to the present invention. This is the same as the LPF13.16 in Figure 1 or Figure 4 and the ADC.
14, 17, and amplifies the difference (K times) and converts the analog signal into a digital signal with good accuracy (converts with less quantization error) by ADC 14, 17. It is. FIG. 7 shows an explanatory diagram of the operation.

In FIG. 6, LPF (low pass filter) 13.
The output of 16 is the sine component or cosine component of the orthogonal detection signal, and corresponds to FIGS. 7(a) and (bl).

The selection signal generation circuit 30 generates each component (AS
I, BSI, As2, BS2, ACI, BCI, A, C
2, BO2)) (Fig. 7(C), f
dl, Tel, if)) or to hold these components (see Figure 7 (gl, (hl, if)).
(1), (J)).

The signal selection circuit (1) 31 and the signal selection circuit +2132 are
The sine component of the quadrature detection signal (ASI, BSI, As2,
B52), cosine component (ACI, BCI, AC2, B
This is a circuit that selects O2) respectively.

The SH (sample and hold) circuits 33 to 40 detect orthogonal detection signals ASI, As2, BSI, BS2, ACI, and AC2 in response to the selection signal from the selection signal generation circuit 30.
, BCIXBC2 (see FIG. 7 (phantom, Thl, (1) TJ)).

The active amplifiers 41 to 44 are for generating an illustrated signal which is twice the difference between the signals held in the SH circuit (see FIG. 7 (kl, (1)).

The signal selection circuits (3145 and 46 select the signals held or operationally amplified by the 88 circuits and operational amplifiers as shown in the figure) and sequentially input them to the ADCs 14 and 17.

With the above configuration, in order to calculate the ultrasonic nonlinear parameters in the arithmetic unit 18, it is necessary to amplify the signal, especially the difference, by a factor of two, and then convert the analog signal into a digital signal by the ADCs 14 and 17.
It becomes possible to reduce the quantization error caused by 17 and calculate the ultrasonic nonlinear parameters with good accuracy.

FIG. 7 shows an explanatory diagram of the operation of the circuit of FIG. 6.

In FIG. 7, (al, (bl) indicate the sine component and cosine component after LPF.
3.16 represents the sine component and cosine component of the quadrature detection signal after removing harmonic components. In the figure, ASI,
BSI, AS2, BS2, ACl, BCl, AC2, B
O2 is shown in Figure 2 ffl, tgl or Figure 5 (gl,
It corresponds to the symbol shown in Fhl.

(C1, (dl, (el, (fl) is a signal that selects the corresponding signal in (al, (bl. This is the selection signal to

tgl, (hl, (11, ('')) indicates the hold timing held by the 88 circuit.
Let the held value of Sl be 7ASl. Similarly,
Signal ACI, BSI, BCI, AS2, AC2, BS2
, the held values of BO2 are respectively γAC−γ11S1
%7ICI%T*5zsTAC21γBS2%γ寥c2
shall be.

+kl, (1) indicates the eight-fold transformation of point A and point B. This means that among the signals held by the 88 circuits, the signals indicated by arrows are subjected to AD conversion and converted into digital values. To be more specific, in a state without a pump wave, perform AD conversion on γ1, TAc3 of (g+), γ11S1 and γgel of (h).Furthermore, with a pump wave, multiply the difference by (kl). K(TAsz-γA5.), K(γscz
r sc+ ), (K (γmst Tms+ ), which is the signal obtained by multiplying the difference by II, K (1MC2Ts
AD conversion is performed for c,). These AD-converted values are stored in the memory 18. Then, the arithmetic unit 19 retrieves it from the memory 18 and calculates the phase shift parameter. According to Section 209, which will be described later, the phase shift position up to point A is calculated by the following equation (21).

A (K2(γ ac2- γAc+)”+ K”(T
Asz-γ ,,,)Z)l/Z 1(γ1.'+γ
As, 2) l/2 K・(21) Similarly, the phase shift up to point B is expressed by the following formula (2
2).

Chi(γsc+ ”+ r ms+ ”) ””・・
・ ・ ・ ・ ・ ・ ・ ・ ・ ・ ・ ・
・ ・ ・ ・ ・ (22) Using the above A6 and A, the phase shift parameter N between points A and B can be calculated using equation a9 described later.

FIG. 8 shows a configuration for measuring phase shift parameters at a plurality of arbitrary points in the depth direction of the medium 21 to be measured. This is achieved by providing two sets of orthogonal detection circuits 22-1 and 22-2, and synchronizing the timing signal from the timing generator 1 to the time gate 8- with the H level and L level changing alternately. When the left quadrature detection circuit 22-
1, the measurement wave signal received from the medium to be measured 21 is manually subjected to orthogonal detection, while at the L level, the measurement wave signal received from the medium to be measured 21 is input to the right quadrature detection circuit 22-2 to perform orthogonal detection. I am trying to detect the wave (Figure 9 (dl, (
0), (see fl) In this way, by providing two sets of orthogonal detection circuits 22-1 and 22-2 and alternately inputting the received measurement wave signals to these and performing orthogonal detection, the measurement wave With the signals separated, the sine and cosine signals after orthogonal detection are stopped as shown in Figure 9 (g) and (hl), and the influence of the phase of the measurement wave signal is minimized. At the same time, it is possible to reduce variations by using a median filter, which will be described later.

FIG. 9 shows an explanatory diagram of the operation of the configuration shown in FIG.

In FIG. 9, fat indicates the transmission timing of the measurement wave. This is from the ultrasonic transducer 5 to the medium 2 to be measured in FIG.
1 represents the transmission timing of the ultrasonic pulse for the measurement wave transmitted toward 1.

(bl indicates the transmission timing of the pump wave. This is
FIG. 8 represents the transmission timing of a pump wave transmitted from the ultrasonic transducer 4 toward the medium 21 to be measured.

(C1 shows the received waveform (waveform of the measurement wave) without a pump wave and with a pump wave.

+d+ indicates a gate signal. This shows the gating signal that timing generator 1 in FIG. 8 supplies to time gate 8-1.

(el indicates received signal 1 after gate. This is cut out from the measurement wave signal in (C) when an H level gate signal is supplied to time gate 8-1.

(fl indicates the received signal 2 after the gate. This is extracted from the measurement wave signal of (c+) when the L level gate signal is supplied to the time gate 8-1.

(gl, (hl are the sine and cosine signals after orthogonal detection of the received signal 1.

(i> indicates the position where the calculation result of the phase shift amount is calculated. In the figure, it is shown that the phase shift amount is calculated at the positions !1, H1, A, . . .

fj) and (kl are the sine and cosine signals of the received signal 2 after orthogonal detection.

(1) indicates the position where the calculation result of the phase shift amount is obtained. This indicates that the phase shift amount is calculated at the positions A7, A, , V, . . . in the figure.

As described above, it is possible to provide two sets of quadrature detection circuits 22-1 and 22-2, alternately input the received measurement wave signals, perform quadrature detection, and obtain the amount of phase shift while avoiding the influence of phase steepness. It becomes possible.

FIG. 10 shows an explanatory diagram of median filter/moving average.

FIG. 10 fat shows a received signal (measurement wave signal).

FIG. 1O (bl indicates phase shift value, 4L. Solid line is an analysis obtained by measuring the amount of phase shift +'9. of a plurality of parts in the cleanliness direction of the medium 21 to be measured using the above-mentioned configuration. The dotted line indicates the theoretical value.Among these analytical values, the phase shifts shown in figures a and b at the discontinuous points of the phase of the measured wave differ from the theoretical value. It deviates greatly.

FIG. 10(C) shows the phase after applying the median filter. This is shown in Fig. 10 (among the analytical values of bl, for a and b that deviate greatly from the theoretical value due to phase discontinuity, arrange the phase shift amounts of five adjacent points in descending order, and calculate from the center value, that is, from the smallest one. The third (directly placed (median fill) processing is performed. This allows values whose analytical values deviate greatly from the theoretical values to be excluded.

FIG. 10 (di is a moving average of the phase shift amount A) after performing the median filter processing of FIG. 10+c+ in order to obtain an even smoother phase shift amount.

FIG. 10(e) shows the final phase shift parameters from the phase shift amount vl shown in the upper row and from A to phase shift parameters N, , 'P, and from A to phase shift parameter N2... N is calculated using Equation 05), which will be described later.

In addition, in Fig. 10, median filtering/moving average is performed only in the depth direction, but scanning is performed two-dimensionally,
The obtained phase shift value, L, may be spatially median filtered/moving averaged.

Note that FIG. 11 shows an explanatory diagram of the amount of phase shift.

In the figure, instep shows the amount of phase shift without pump wave,
'P, IL is the phase shift t with and without pump wave.
shows the difference between The principle of calculating the phase shift parameter N will be explained below.

The speed of sound when the sound pressure in the medium 21 to be measured is zero is C0, and the density is ρ. Then, the sound speed C when a sound pressure P is applied is B C''' C.

+ ・(1) N= (B/A) ・ ・
・ ・ ・ ・(6)2 ρoco A aP A aP . Here, the subscript S indicates isentropy.

That is, due to the sound pressure P of the pump wave, the sound speed C is B ΔC= P (4) 2
It will change by ρocoA.

Here, the "phase shift parameter N", which is directly defined from the pressure dependence of the sound velocity, is defined as follows.

2 ρ. C0 Therefore, ρ. , co are known, by estimating one of N and B/A, the other can be calculated from equation (6).

Waves propagating in a medium can be expressed as follows, ignoring attenuation.

P (t ; x) −A−3in (ω(t
-1))・(71 Niko, P is sound pressure, L is time, X is spatial coordinate, A is amplitude,
ω is the angular frequency and C is the speed of sound. In (7), when the sound speed C changes by a minute amount ΔC from the sound speed C0 at static pressure, the phase term type becomes as follows.

A=ω・(−) C0+ΔC aP Furthermore, the nonlinear parameter B/A and the phase shift parameter N have the following relationship.

Co C.

Co C.

ΔC C0 As a result, the change in phase due to the change in sound speed, ΔA, is ΔA=
Instep-instep.

ΔC = C・X ・ ・ ・ ・ ・ ・
・ ・ ・ ・(9) Therefore, assuming that the small change ΔC in the sound speed C is due to nonlinearity, the pressure dependence of the phase term type can be expressed as shown in the following equation using the phase shift parameter N in equation (5).

If ΔK 1 ΔC is true, then the sound pressure P in equation (2) can be considered to be the sound pressure of the pump wave. Therefore, from the sound pressure of this pump wave, the sound velocity distribution C(x; t) on the X-axis can be expressed as follows using the phase shift parameter N in (5).

C C (x; t) = C, += P (x)
aP ΔP Co ΔP ΔP = C・x−N ・ ・ ・ ・ ・ ・ ・ ・ ・
・ ・ ・For GO1 and below, a basic formula will be derived for the method of measuring the phase shift parameter N.

The sound pressure when the measurement wave is superimposed on the pump wave is the sum of the sound pressure of the pump wave and the sound pressure of the measurement wave. Large P = Co ”Co ・N (x) ・P
(x)...011 Here, N (x) represents the spatial distribution of the phase shift parameter N. Now, assuming that the time at which the pump wave was sent out is t = 0, the amount of phase shift Δ'P (L) of the measurement wave observed when it has traveled the distance is +C0 1+C0 C(x; t) ・ N (x ) ・ N (x) (X) (X) It can be derived as follows.

It becomes C0・dx. In 2@, the first term represents the linear phase rotation term caused by the measurement wave propagating along the length, and the second term represents the phase shift amount ΔKNL(L) due to the nonlinear effect.

ΔKML (L) = -ωJ N (x) ・P
(x) dx・ ・ ・ ・ ・ ・ ・ ・The round equation 0 race is the basic equation for measurement. If N (x) is constant in the interval considered as the target, the formula α■ can be written as the following formula.

ΔAML(L)--ω-Nf P(x)dx・-04
1 Therefore, if we consider two arbitrary points A and B (the distances to points A and B are , and L), and let the amount of phase shift due to the nonlinear effect up to those points be A1 and A, respectively, then A
The phase shift parameters between -B are
Nf P (x) By dx, A, - A.

N= ・・・・・・09−ωf
P(x)dx Next, set the phase shift between the two points A and B! , can be calculated by orthogonally detecting the received signal as follows.

The received signal (measurement wave signal) when there is no pump wave is I+S
in (ωt+'P) Let the received signal when there is a pump wave be +1 Sin (ω is the raw type +'PNL). Also,
The reference signal for quadrature detection is ■, Sinωt, Ir C
Let it be osωt. However, A is a linear phase rotation term, 'PNL is a phase difference due to a nonlinear effect, ■8 is a received signal strength, and ■7 is a reference signal strength.

If the received signal when there is no pump wave and the received signal when there is a pump wave are multiplied by a reference signal, and then passed through a reduction filter that cuts components over 2ω, the result shown in Figure 3 is obtained. obtain. If the result of FIG. 3 is expressed as a vector, it will be as shown in FIG. 11. Since the phase shift amount 'PNL due to the nonlinear effect is minute, the following equation holds true. Calculate 2〇gl for points A and B, and set the phase shift amount at that time as '1'1, A. Then, calculate the phase shift parameter N between points A and B from the relationship of formula α9. can do. Also, even if you do not use NiG9+,
It can also be calculated from the relationship of the following formula.

γ @2 γ, 1A), L=ta
n-'-jan-' ...(2IIl
γcl Te1 However, X- 1, -[, ・ ・ ・ ・ ・ ・ ・ ・ αη. Here, from the geometrical relationship shown in FIG.
sz rs+) ” ) ””=(rc+”
+γ, Z) l/2 ・ ・ ・ ・ ・
・ ・ ・ ・Since α is, the amount of phase shift due to the nonlinear effect is 8L (7c+2 +711”)”” [Effects of the Invention] As explained above, according to the present invention, for example, with and without pump waves, This is because a configuration is adopted in which parts corresponding to a plurality of arbitrary parts in the medium to be measured 21 are cut out from the two types of measurement wave signals received at , it is possible to avoid the influence of the phase steepness of the measurement wave, and to perform median filter processing or the like to measure nonlinear parameter estimates with good accuracy and no variation.

・　・　・　・・(191

[Brief explanation of drawings]

FIG. 1 is a configuration diagram of one embodiment of the present invention, FIG. 2 is an explanatory diagram of the operation of the configuration shown in FIG. 1, FIG. 3 is an example of a signal after orthogonal detection, and FIG. 4 is a configuration diagram of another embodiment of the present invention. , FIG. 5 is an explanatory diagram of the operation of the configuration shown in FIG. 4, FIG. 6 is an example of a differential amplifier circuit according to the present invention, and FIG.
6 is an explanatory diagram of the operation of the circuit shown in FIG.
11 is an explanatory diagram of the amount of phase shift, FIG. 12 is an example of ultrasonic pulses for pump waves and measurement waves, and FIG. 13 is an explanatory diagram of the concept. In the figure, ■ is a timing generator, 4.5 is an ultrasonic probe,
8.8-1.9-1.9-2 is a time gate, 10 is a reference signal, 11 is a 90° phase shift, 12.15 is a multiplier,
Reference numeral 14.17 represents an ADC, 19 represents an arithmetic unit, 21 represents a medium to be measured, and 22.22-1.22-2 represents an orthogonal detection circuit.

Claims (3)

[Claims] (1) In a measurement device that measures ultrasonic nonlinear parameters of a medium to be measured, an ultrasonic device that transmits a high frequency and low sound pressure ultrasonic pulse for measurement waves to the medium to be measured (21) and receives reflected measurement waves. A sonic transducer (5), an ultrasonic transducer (4) that transmits a pump wave of low frequency and high sound pressure to the medium to be measured (21), and a measurement wave received by the ultrasonic transducer (5). Orthogonal detection is performed after cutting out parts corresponding to a plurality of arbitrary parts in the medium to be measured (21) from the signal, or by performing orthogonal detection on the measurement wave signal. Reference signal and 90° for orthogonal detection
Quadrature detection is performed by supplying signals with different phases, and for the real component and imaginary component after this quadrature detection, when the ultrasonic pulse for the measurement wave is superimposed on the pump wave and transmitted, and the ultrasonic pulse for the measurement wave Calculate both when only the ultrasonic pulse for the measurement wave is transmitted, or calculate both when the ultrasonic pulse for the measurement wave is superimposed on the pump wave and transmit it by changing the position on the pump wave, and calculate the amount of damage based on either of these two. An ultrasonic nonlinear parameter measuring device characterized in that it is configured to measure ultrasonic nonlinear parameters at a plurality of arbitrary locations in a measurement medium. (2) The ultrasonic transducers (4) and (5) are connected to the medium to be measured (
21) The ultrasonic nonlinear parameter measuring device according to item (1), wherein the ultrasonic nonlinear parameter measuring device is configured to two-dimensionally scan the object and measure the spatial distribution of nonlinear parameters. (3) Paragraph (1) characterized in that the above-mentioned measured phase shift amount is configured to perform a median filter and/or a moving average to reduce variations in the calculated phase shift amount. (2) The ultrasonic nonlinear parameter measuring device described in section (2).