JPH0421147B2 - - Google Patents

Description

Detailed Description of the Invention (Industrial Application Field) The present invention illuminates a target object using an acoustic pulse signal, and visualizes the reflection intensity on a cross section of the target object from the reflected signal from the target object. , relates to an audiovisual device that obtains a frontal image (also referred to as a visual image or a mode image).

(Prior art) Conventionally, this type of equipment has been used, for example, in "Oki R&D"
Vol. 50, No. 1, pp. 57 to 62, June 1981.

FIG. 6 is an external view of the transducer array of the cross-fan beam scanning audiovisual device shown in the document, where 1 is the housing of the transducer array, 2 is the transmitter array, and 3 is the receiver. The transducer array, X _A , Y _A , Z _A is a rectangular coordinate system with the origin O _A and the X, Y axes placed on the transducer array surface. The transmitter array shown in the literature is a linear array arranged linearly in the YA _- axis direction, and the receiver array is a linear array arranged linearly in the XA _- axis direction.

FIG. 7 is a diagram showing a more detailed arrangement of the transmitter array 2 and the receiver array 3, with 2 ₁ , 2 ₂ ,..., 2
_MT is a transmitter element, 3 ₁ , 3 ₂ , . . . , 3 _MT is a receiver element, MT is the number of transmitter elements, and MR is the number of receiver elements. The array spacing of the transmitter array 2 and receiver array 3 is determined by the viewing angle in the vertical (Y _A ) direction and the frequency of the transmitted signal, and the viewing angle in the horizontal (X _A ) direction and the frequency of the transmitted signal. It will be done.

FIG. 8 is a geometric explanatory diagram showing the image forming method of the cross fan beam scanning audio-visual apparatus shown in the above-mentioned document, and 4 shows the target object (X _A ,
Y _A ) A cross section cut parallel to the plane, X _B and Y _B are rectangular coordinate systems with the origin O _B and the X and Y axes on the cross section 4, 5 _j,i are subdivision planes on the cross section 4, and 6 is The straight lines θ _x,j and θ _y,i connecting the O _A and the subdivision plane 5 are the directional cosine angles of the straight line 6 with respect to the X _A axis and the Y _A axis, respectively. In the cross-fan beam scanning method, the main axis direction of the beam is θ _y,i
The direction (θ _{x ,j} ,
The subdivisions 5 on the cross section 4 located at θ _y,i ) are obtained as pixels.

FIG. 9 is a detailed explanatory diagram of the fan beam, where 7 is a horizontal beam pattern of a transmission beam;
_Θ The vertical beam pattern of the beam, Θ _Y is the beam width of the beam pattern.

The intensity distribution of the reflected signal from the cross section 4 shown in FIG. 8 is obtained as a set of pixels 5 that are the cross points of the transmit fan beam and the receive fan beam. In the cross-fan beam scanning method shown in the above-mentioned document, in order to image the entire reflection intensity distribution on the cross-section 4, it is necessary to irradiate the cross-section 4 with the transmitted fan beam, and the fan beam If the beam width of the vertical beam pattern 8 is Δθ _y , approximately 2Θ _Y /Δθ _y transmissions are required.

FIG. 10 is a geometric explanatory diagram showing in more detail the method of visualizing the reflection intensity on the cross section 4.
3 is the surface irradiated by the i-th transmitting fan beam whose principal axis direction is θ _y,i , and 14 is the j-th surface whose principal axis direction is θ _x,j .
This is the surface covered by the th reception fan beam, and y _B,i = R・sinθ _y,i R・θ _y,i (1) x _B,j = R・sinθ _x,j R・θ _{x,j ( 2 ) ξ B = R ・ sinΘ _} sinΔθ _y R·Δθ _y (6). However, R is the distance between O _A and O _B , and Δθ _x and Δθ _y are the beam widths of the receiving fan beam and the transmitting fan beam, respectively. Here, it is assumed that the origin O _B is on Z _A , and that ξ _B /R<<1 and η _B /R<<1. With one transmission in the θ _y,i direction,
In order to obtain KR pixels of 5 _j,i , 5 _j,z , ..., 5 _j,KR , and visualize the entire section 4,
KT2η _B /Δy _B 2Θ _Y /Δθ _y transmissions are required. Therefore, if the time interval of transmission is τ _P seconds, it will take at least T=KT·τ _P seconds (7) to image the entire cross section 4.

Next, FIG. 11 is a functional block diagram showing the system of the transmission circuit section of the cross-fan beam scanning audio-visual apparatus disclosed in the above-mentioned document, in which 20 is an oscillator, 21 is a modulator, 22 is a transmission controller, 23 is an input terminal, 24 is an output terminal, 25 is a transmission delay adder, 26 ₁ , 26 ₂ , ..., 26 _MT are transmission amplifiers, and 27 ₁ , 27 ₂ , ..., 27 _MT are transmission matching circuits. .

Oscillator 20 generates a continuous wave of frequency f _T ,
The modulator 21 modulates the center frequency f T and the time width according to a modulation signal [D _T ] inputted from the transmission controller 22 and having a time width D _T starting at time t _T,i and ending at t _{T ,i} +D _T . A pulse signal P(t) of D _T is output. Transmission delay adder 25
gives a phase delay or a time delay to the pulse signal P(t), and generates the same number of signals P ₁ (t), P ₂ (t), ..., P _MT ( Output t). Signal P _n (t) corresponding to m-th element 2 _n
is determined from the position coordinates of the element 2 _n and a selection signal (θ _y,i ) output from the transmission controller 22 in the principal axis direction θ _y, i of the transmission beam 8. Each signal P ₁ (t),
P ₂ (t),..., P _MT (t) are transmission amplifiers 26 ₁ , 2
6 ₂ ,..., 26 _MT and amplified by the transmission matching circuit 27
₁ , 27 ₂ ,..., 27 _MT After impedance matching etc. are performed, each transmitter element 2 ₁ 2 ₂ ,..., 2 _MT
The signal is converted into an acoustic signal and radiated. The acoustic signals radiated from each of the elements 2 ₁ 2 ₂ , . . . , 2 _MT interfere with each other within the propagation medium, thereby forming a transmission beam pattern 8 as shown in FIG. 9 above. In addition, input terminal 2
3 is a terminal for inputting the estimated value τ^ _V of the reflection duration to the transmission controller 22 in order to determine the interval of time t _T,i at which the transmission timing signal D _T is output from the transmission controller 22. . In this case, the transmission time T _T,i-1
The minimum value of the interval between and t _T,i is determined from the reflection duration and the round trip propagation time to the target object cross section 4.
Further, the output terminal 24 is a terminal that outputs the same transmission timing signal _DT that is output to the modulator 21.

FIG. 12 is _a functional block diagram showing the receiving circuit section of the cross-fan beam scanning audio-visual apparatus _shown in the above-mentioned document.
_MT is a preamplifier, 31 ₁ , 31 ₂ , ..., 31 _MR is a reception gate circuit, 32 is a reception controller, 33 ₁ , 33
₂ ,...,33 _MR is a quadrature demodulator, 34 is a reference signal generator, 35 ₁ , 35 ₂ ,..., 35 _MR is a sampling circuit, 36 is a receiving beamformer, 37 is an input terminal, 8 is an input terminal, 39 is an output It is a terminal. The preamplifiers 30 ₁ , 30 ₂ , ..., 30 _MR amplify the output signals received by the respective receiver elements 3 ₁ , 3 ₂ , ..., 3 _MR of the receiver array 3 to an appropriate level, The reception gate circuits 31 ₁ , 31 ₂ , . . . , 31 _MR transmit the amplified signals in a time width _DT specified by the reception timing signal DR output from the reception controller 32 _.
over the orthogonal demodulators 33 ₁ , 33 ₂ ,..., 33
Output to _MR . The reception controller 32 is the transmission controller 2
From the transmission timing signal _DT outputted from the output terminal 24 of 2 and inputted to the input terminal 37, and the distance R and the sound speed C inputted from the input terminal 38 to the target object cross section, the reception gate circuit 31 ₁ ,
31 ₂ ,...,31 Determine the time t _R,i and time width D _R to open _{the MR} , and receive timing signal D _R ending at time t _R,i +D _R
Output. Orthogonal demodulator 33 ₁ , 33 ₂ ,..., 33
_{The MR} orthogonally demodulates each signal output from the reception gate circuits 31 ₁ , 31 ₂ , ..., 31 _MR using a reference signal of frequency f _R output from the reference signal generator 34 to generate a complex envelope signal S ~ ₁ (t), S~ ₂ (t)…
，
Output S ^~ _MR (t). The actual complex envelope signal S ^~ _n (t) is output as a set of two signals: an in-phase (real part) signal S _I,n (t) and a quadrature (imaginary part) signal S _Q,n (t). .

FIG. 13 is a detailed functional block diagram of the orthogonal demodulator 33 _n , in which 40 is an input terminal into which a received signal is input from the receiving gate circuit 31 _n , 41 ₁ , 41 ₂
are input terminals 42 ₁ , 42 ₂ to which the reference signals cos2πf _R t and sin2πf _R t are input from the reference signal generator 34;
is a multiplier, 43 ₁ and 43 ₂ are low-pass filters, 4
4 ₁ 44 ₂ are output terminals. Reception gate circuit 31
The signal output from _n is the two reference signals cos2πf _R t and
sin2πf _R t is multiplied by multipliers 42 ₁ and 42 ₂ , respectively, and the results are passed through low-pass filters 43 ₁ and 4, respectively.
3 ₂ and removing unnecessary high-frequency components, the two signal sets S _I,n (t) and S _Q,n (t) representing the complex envelope signal are respectively output to the output terminal 44 ₁ , 44 ₂ .

_The m-th sampling circuit _{35 n} of the sampling circuits 35 ₁ , 35 _{2 , .}
(t) at a constant time step ΔT, and outputs the sampled signal to the receiving beamformer.

The reception beamformer 36 receives complex envelopes S ^~ ₁ (t), S ^~ ₂ (t),..., _S ~ _MR ( _{t )} input from the sampling circuits 351, 352,..., ^35MR .
A beamforming operation is performed on the sampling signal of the receiving beam 10 in which the principal axis direction is θ _x,j according to the receiving beam direction selection signal θ _x,j output from the receiving control circuit 32. form a beam. The output φ _i,j of the beamformer is outputted to the output terminal 39 as the intensity of the subdivided pixels 5 in the directions (θ _x,j , θ _y,i ) on the cross section 4 of the target object. Let the φ _i,j be i=1,..., KR, j=1,...,
By obtaining for KT, the cross section of the target object 4
The above can be visualized.

FIG. 14 is a detailed functional block diagram of the beamformer 36, where 45 ₁ , 45 ₂ ,...45 _MR are input terminals into which signals output from the sampling circuits 35 ₁ , 35 ₂ ,...35 _MR are input; _1,4
6 ₂ ,...46 _MR is a delay compensator, 47 is an input terminal to which (θ _x,j ) outputted from the reception controller 32 is input, 48 is an adder, 49 is an absolute value calculator, 4
7 is an output terminal. The complex envelope signal S ^~ _n (t) input from the sampling circuit 35 _n is
Phase delay compensation or time delay compensation determined by the position coordinates of the m-th receiver element 3 _n and the reception beam direction selection signal θ _x,j input from the reception controller 32,
It is received by a delay compensator 46 _n , and the outputs of each delay compensator are added together by an adder 48 to obtain a complex beam output signal. The absolute value calculator 49 calculates the absolute value of the complex beam output signal and outputs the beam output intensity φ _i,j to the output terminal 47 .

As shown above, by using an image forming method using an aperture synthesis method such as a cross-fan beam scanning method, it is possible to obtain independent pixels with a total number of MT++MR or more of the number of transmitter elements and receiver elements. The advantage is that the hardware can be made smaller because MT+MR can be chosen smaller.

(Problems to be Solved by the Invention) However, the above methods disclosed in the literature have the following problems.

Since an image is formed using a reflected signal of a narrow band so-called coherent signal, speckle noise is likely to appear in the image.

When trying to widen the signal band, the sampling frequency of the sampling circuits 35 ₁ , 35 ₂ , ..., 35 _MR increases, and the transmitter array 2 increases.
Due to so-called cavitation, etc., occurring in the transmitter element, it is not possible to transmit an acoustic signal with a sufficiently high sound pressure level.

Let the repetition interval τ _P of the transmitted signal be τ _P τ _V −τ _R and τ _P
＞τ _R (where τ _V is the duration of the reflected signal, and τ _R is the round-trip propagation time of the sound wave to the cross section 4 of the target object
2R/C). Therefore, if the reflection duration time τ _V is longer than τ _R or if the round-trip propagation time τ _R is longer, the image forming time given by equation (7) increases, making it impossible to form a fast image.

When the repetition time τ _P becomes larger than the processing time τ _S for forming an image for a reflected signal of one transmission, the waiting time of the image forming section increases, and dead time occurs during the image forming process.

The present invention addresses the above-mentioned problems in which speckle noise tends to appear in images, the sampling frequency increases when the band is widened and it is difficult to transmit signals with high sound pressure levels, and the transmission repetition time interval cannot be shortened, so it takes time to form images. The purpose of the present invention is to solve the problem that waiting time tends to increase and increase in image forming processing, and to provide an audio-visual device that can form images with less speckle noise and can form images at high speed. do.

(Means for Solving the Problems) The present invention transmits an acoustic pulse signal, receives a reflected signal of the pulse signal from a target object, and obtains an intensity distribution on a cross section of the target object by beamforming operation. The present invention relates to an audio-visual apparatus that irradiates the entire cross section of a target object and obtains a frontal image of the cross section of the target object by changing the direction of the transmission beam each time the pulse signal is transmitted.

The present invention provides the audio-visual apparatus described above, which includes the following components.

First, the frequency of the transmission pulse signal is multiplied into N types. Second, the transmission time interval τ _P of the transmission pulse signal is set to a value close to the time τ _S required for image formation. Thirdly, the frequency of the reference signal of the orthogonal demodulator that demodulates the reflected signal is multi-frequencyized into N types, and selected in accordance with the frequency of the transmission pulse signal. Fourth, on the cross section of the target object, the same surface is irradiated N _P times with signals of N _P different frequencies. Fifth
Next, the N _P received beam outputs of the reflected signals corresponding to the N _P irradiations are averaged.

(Function) The first transmission pulse signal has N types of frequencies.
It has one frequency f T, ₁ selected from f _T,1 , f _T,2 , ..., f _T,N . This transmitted pulse signal is reflected by the target object and received as a reflected signal. This reflected signal is supplied to the orthogonal demodulator (at this time, the reflected signal is supplied to the orthogonal demodulator as a received pulse signal at a predetermined time interval by a gate circuit). The orthogonal demodulator selects a frequency f R, _{1 corresponding to the frequency f T,1 of} the transmitted pulse signal from among N types of frequencies f _R,1 , f _R,2 , ..., f _RN .
(for example, f _R,1 = f _T,1 ) and demodulate the received pulse signal. The demodulated signal is output as a received beam output by beamforming operation.

Next, the second transmission pulse signal has one frequency f _T,2 selected from N types of frequencies. The transmission time interval τ _P of this second pulse signal
is set to a value close to the time τ _S required to form an image of the first transmission pulse signal. The direction of this second transmission pulse signal is the same as the direction of the first transmission pulse signal. The second sent in this way
The th transmission pulse signal is processed in the same way as the first transmission pulse signal. The third transmission pulse signal sent out next has a frequency of f _T,3 , and its direction is determined according to the value of N _P. For example, N _P =
2, the third transmission pulse signal is the first and second transmission pulse signal.
It is transmitted in a different direction from the first transmission pulse signal, but when N _P ≧3, it is transmitted in the same direction as the first and second transmission pulse signals. Hereafter, repeat the above action to move the same plane on the cross section of the target object in different directions.
Irradiate N _P times with signals of N _P frequencies. The N _P received beam outputs obtained correspondingly are averaged. This forms an audiovisual image.

(Example) Hereinafter, an example of the present invention will be described with reference to the drawings.

FIG. 1 is a functional block diagram showing a first embodiment of the present invention, in which 20 ₁ , 20 ₂ , ..., 20 _N are oscillators, 50 is a multiplexer, 51 is a transmission controller, and 52 is an input terminal. , 53 is an input terminal,
34 ₁ , 34 ₂ ,..., 34 _N are reference signal generators,
54 is a reception controller, 55 is a multiplexer, 56
is a smoother, and 57 is an output terminal. In the embodiment shown in FIG. 1, the frequency domain average number N _P is input manually from the input terminal 52, and the transmission repetition time interval τ _P is determined by the image forming processing time τ^ for each transmission. This is an example.

The multiplexer 50 has N oscillators 20
₁ , 20 ₂ , ..., 20 _N as a transmission frequency selection signal input from the transmission controller 51
Select one according to f _T,1 . The N oscillators 20 ₁ , 20 ₂ , . . . , 20 _N output signals of frequencies f ₁ , f ₂ , . . . , f _N , respectively. The output signal of the multiplexer 50 is modulated by the transmission timing signal D _T input from the transmission controller in the modulator 21, as shown in FIG. 11, and has a center frequency f _T,i ,
A pulse signal P(t) with a time width D _T is generated.

FIG. 2 shows the time waveform of P(t), where f _T,1 =
This is an example in which the transmission frequency selection signal f _T,i is selected such that f ₁ , f _T,2 = f ₂ , . . . , f _T,N = f _N and this is repeated thereafter. The transmission controller 51 receives the transmission frequency selection signal f _T,1 and the transmission timing signal D _T
In addition to outputting the frequency domain average number N _P input from the input terminal 52, the transmission beam direction selection signal θ′ _y,i is transmitted with a delay so that the transmission beam 8 is formed in a desired direction. Output to adder 25.
The principal axis direction θ′ _y,i of the i-th transmission beam is selected so as to irradiate the same plane on the cross section 4 of the target object N _P times with different transmission frequencies.

FIG. 3 is a diagram showing the relationship between the principal axis θ' _y,i of the i-th transmission beam, the transmission frequency f _T,i , and the above N _P by dividing the cross section 4 of the target object by angle. . FIG. 3a shows an example in which N is an even number, N≧2, and KT is a multiple of N, and N _P =2. in this case,
For example, θ′ _y,1 = θ′ _y,2 = θ _y,1 , f _T,1 = f ₁ , f _T,2 = f ₂
The surface corresponding to the θ _y,1 direction of the cross section 4 of the target object is irradiated twice at frequencies f ₁ and f ₂ . FIG. 3b shows an example in which N _P =N. In this case, for example, θ′ _y,1 = θ′ _y,2 =…=θ′ _y,N
=
θ _y,1 , f _T,1 = f ₁ , f _T,2 = f ₂ , ..., r _T,N = f _N , which corresponds to the θ _y,1 direction of cross section 4 of the target object. The surface will be irradiated N times with frequencies f ₁ , f ₂ , . . . , f _N .

Next, FIG. 4 shows an example in which N _P =1, which is a special case of FIG. 33.

In this case, the cross-sectional surface of the target object is irradiated only once with one frequency.

In FIG. 1, the reception controller 54 receives a transmission timing signal [D _T ] input from the transmission controller 51, a transmission beam direction selection signal (θ' _y,i ),
From the transmission frequency selection signal (f _T,i ), the frequency domain average number N _P , the distance R to the cross section 4 of the target object inputted from the input terminal 38, and the sound speed C, the reception gate circuits 31 ₁ , 31 ₂ ,...,31 Outputs a reception timing signal [D _T ] that gives the start time T _R,i and the end time T _R,i +D _R of opening _{the MR} ,
A reference frequency selection signal f _R,i is output. Further, it outputs a reception beam direction selection signal θ′ _x,j that specifies the main axis direction of the reception beam formed by the reception beam former 36, and also outputs the transmission beam direction selection signal θ′ _y,i input from the transmission controller 51. and the frequency domain average number N _P are output at appropriate timing. The multiplexer 55 selects the N reference signal _generators 34 ₁ , 34 ₂ ,
..., 34 _N , and outputs the selected signal to the orthogonal demodulators 33 ₁ , 33 ₂ , ..., 33 _MR .

The frequency of the reference signal generators 34 ₁ , 34 ₂ , ..., 34 _N is usually the same as that of the oscillators 20 ₁ , 20 ₂ , ..., 20
_N frequencies are taken as f ₁ , f ₂ , . . . , _N.
If the transmission frequency t _T,i at transmission time t _T,i is f _n , then
The reference signal frequency t _R,i used for orthogonal demodulation of the reflected signal of the transmitted signal at the reception time t _R,i is also selected as f _n .

Next, the smoother 56 converts the receive beam output φ _i,j output from the receive beam former 36 into the transmit beam direction selection signal θ′ _y,i input from the receive controller 54 and the frequency domain average number N _P . Based on the information i
It is averaged over the area and outputs Φ _k,j to the output terminal 57. For example, θ _y,i = θ′ _y,i+1 =…=θ′ _y,i+Np-1 = θ
If _y,k , then Φ _k,j is obtained as follows.

Φ _k,j = 1/N _Pi+Np-1 〓 ⁿ⁼ⁱ φ _i,j (8) The above equation (8) is the beam of the reflected signal of the transmitted signal N _P times that irradiates in the θ _y,k direction. This indicates that the output φ _i,j is averaged over N _P times. The above Φ _k,j is k=
1, 2,..., KT, j=1, 2,..., KR, the reflection intensity distribution on the cross section 4 of the target object can be visualized.

Note that the minimum value of the time interval τ _P of the transmission timing signal [ _D If it is a repetition of the signal train and we can assume that Nτ _P τ _V and Nτ _P τ _R , then
The processing time required to form an image for each transmission, that is, the time required to obtain KR beam outputs φ _i,1 , φ _i,2 , ..., φ _i,KR corresponding to the i-th transmission signal τ _S It will be decided. In this embodiment, by inputting the predicted value τ^ _S of τ _S from the input terminal 53, the transmission time interval τ _P
This is an example where τ _P τ^ _S is selected.

FIG. 5 is a functional block diagram showing the main parts of the second embodiment of the present invention, in which 60 is an average number determiner, 61
is an input terminal, 62 is an output terminal that outputs the transmission frequency selection signal f _T,i to the multiplexer 50, and 63 is a transmission timing signal, that is, a modulation signal, to the modulator 21.
An _output terminal 64 outputs the transmission beam direction selection signal θ' _y,i to the transmission delay adder 25. An output terminal 65 outputs the transmission beam direction selection signal θ' _y,i to the reception controller ₅₄ .
This is an output terminal that outputs f _T,i and N _P.

In the embodiment shown in FIG. 5, the frequency domain average number
This is an embodiment in which N _P is automatically determined, and the average number determiner 60 determines the average number according to the relative velocity V between the transducer array of the audio-visual device and the target object and the signal-to-noise ratio SNR of the reflected signal. Appropriate number of frequency domain averages
_NP is determined _and outputted to the transmission controller 51.
The following operations are similar to those of the first embodiment.

N _P determined by the average number determiner 60 is
Generally, as V increases, it is taken smaller,
The value is increased as the SNR becomes smaller.

The embodiments shown in FIGS. 1 to 5 above describe the case where a crossing linear array as shown in FIGS. 6 and 7 is used as the transducer array, and the transmission beam pattern and reception beam pattern are However, in the present invention, the direction of the transmitted beam is changed each time a transmission signal is transmitted, so that the entire cross section of the target object is irradiated, and the cross section of the target object is The present invention can be applied to all audiovisual devices that form images by the so-called aperture synthesis method, which obtains a frontal image.

(Effects of the Invention) As described in detail above, according to the present invention, the frequency of the transmission signal is multi-frequencyized into N types, the transmission time interval τ _P is set to a value close to τ _S required for image formation, The frequency of the reference signal of the orthogonal demodulator is multi-frequency into N types, and the frequency is selected according to the frequency of the transmission signal, so that the cross section of the target object is covered with signals of N _P different frequencies on the same surface _. By irradiating the beam twice and averaging the N _P received beam outputs of the reflected signals corresponding to the N _P irradiations, the following effects can be obtained.

The time required to form an image is not controlled by the round trip propagation time τ _R or the reflection duration τ _V , but is determined by the processing capacity of the image forming unit, and the capacity of the image forming unit can be used most effectively.

Even if the number N of transmission frequencies is increased, the bandwidth of the output signal of the orthogonal demodulator can be made the same as when there is only one transmission frequency, and therefore the sampling frequency of the output signal of the orthogonal demodulator is also independent of N. This allows multiple frequencies to be used without increasing the load on receive beamforming.

By selecting N _P ≧2, it becomes possible to perform averaging in the video frequency domain, and speckle noise can be reduced.

Since an equivalently wideband signal is divided and transmitted for each frequency, the transmission power may be low, and the load on the transmission amplifier can be reduced, and cavitation of the handset/receiver element is less likely to occur.

By selecting N _P ≧2, it is possible to reduce image quality deterioration due to ambient noise, etc.

Since N _P can be selected according to the relative velocity between the objects in the transducer array, the signal-to-noise ratio of the received reflected signal, etc., it is possible to always obtain an optimal image.

[Brief explanation of drawings]

FIG. 1 is a functional block diagram of a transmitting circuit section and a receiving circuit section showing a first embodiment of the present invention, FIG. 2 is an explanatory diagram showing the waveform and frequency of the transmitting signal in FIG. 1,
Figure 3 is an explanatory diagram showing the concept of the frequency domain average number in Figure 1, and Figure 4 shows the frequency domain average number in Figure 1 as 1.
5 is a functional block diagram showing the second embodiment of the present invention, FIG. 6 is an external view of the transducer array of the cross-fan beam scanning method, and FIG. 7 is an explanatory diagram showing the concept when the method is selected. is an arrangement diagram showing the configuration of the transmitter array and receiver array in Fig. 6, Fig. 8 is a geometric explanatory diagram showing the principle of the cross-fan beam scanning method, and Fig. 9 is a transmission diagram in the cross-fan beam scanning method. A diagram showing a beam pattern and a receiving beam pattern, FIG. 10 is a geometric explanatory diagram showing an image forming method in the cross-fan beam scanning method, and FIG. 11 shows the system of the transmitting circuit section in the conventional cross-fan beam scanning method. FIG. 12 is a functional block diagram showing the method of the receiving circuit section of the conventional cross-fan beam scanning method, FIG. 13 is a functional block diagram showing details of the orthogonal demodulator in FIG. 12, and FIG.
This figure is a functional block diagram showing details of the receive beamformer in FIG. 12. 1... Transmitter array housing, 2... Transmitter array, 2 ₁ , 2 ₂ ,..., 2 _MT ... Transmitter element, 3...
Receiver array, 3 ₁ , 3 ₂ ,..., 3 _MR ...Receiver element, 4...Target object cross section, 5...Subdivision plane on target object cross section, 7...Transmission horizontal beam pattern, 8... Transmission vertical beam pattern, 9...
Principal axis direction of transmitting vertical beam pattern, 10...
... Reception horizontal beam pattern, 11 ... Main axis direction of reception horizontal beam, 12 ... Reception vertical beam pattern, 20 ... Oscillator, 20 ₁ ,
20 ₂ ,..., 20 _N ... oscillator, 21 ... modulator, 22 ... transmission controller, 25 ... transmission delay adder, 26 ₁ , 26 ₂ , ..., 26 _MT ... transmission amplifier,
27 ₁ , 27 ₂ ,..., 27 _MT ... Transmission matching circuit, 3
0 ₁ , 30 ₂ , ..., 30 _MR ... preamplifier, 31 ₁ ,
31 ₂ ,...,31 _MR ...reception gate circuit, 32...
...Reception controller, 33 ₁ , 33 ₂ , ..., 33 _MR ... Orthogonal demodulator, 34 ... Reference signal generator, 34 ₁ , 3
4 ₂ ,...,34 _N ...Reference signal generator, 35 ₁ ,3
5 ₂ ,...,35 _MR ...sampling circuit, 36...
... Receive beamformer, 42 ₁ , 42 ₂ ... Multiplier, 43 ₁ , 43 ₂ ... Low pass filter, 46 ₁ ,
46 ₂ ,...,46 _MR ...delay compensator, 48...adder, 49...absolute value calculator, 50...multiplexer, 51...transmission controller, 54...reception controller, 55...multiplexer , 56... smoother,
60...Average number determiner.

Claims (1)

[Claims] 1. Transmit an acoustic pulse signal, irradiate a target object with the pulse signal, receive a reflected signal from the target object at a preset time, and perform a beamforming operation to transform the pulse signal. r=Cτ/2 due to time τ from transmission to reception and sound wave propagation speed C
Obtaining the intensity distribution of the reflected signal on the cross section of the target object at a distance r determined by , and at this time changing the direction of the transmitted beam every time the pulse signal is transmitted, irradiating the entire cross section of the target object, In an audio-visual apparatus that obtains a frontal image of the target object in a cross section at a distance r, the frequency of the transmission pulse signal is multi-frequencyized into N types, and the transmission time interval τp of the transmission pulse signal is set to a value close to the time τs used for image formation. , The frequency of the reference signal of the orthogonal demodulator that demodulates the reflected signal is multi-frequencyized into N types, and the frequency is selected corresponding to the frequency of the transmitted pulse signal, and the cross section of the target object is divided into Np different frequencies on the same surface. 1. An audio-visualization method characterized by emitting Np times with a signal of a certain frequency and averaging the received beam outputs of Np reflected signals corresponding to the Np times of irradiation. 2. The audiovisualization method according to claim 1, wherein the Np is set in a range of 1≦Np≦N. 3. The audio-visualization method according to claim 2, wherein the Np is selected based on relative velocity information between the transducer array and the target object or signal-to-noise ratio information of the reflected signal. .