JPH0421148B2 - - Google Patents

Description

Detailed Description of the Invention (Industrial Application Field) The present invention irradiates a target object using an acoustic pulse signal, and images the reflection intensity on a cross section of the target object from the reflected signal from the target object. The present invention relates to an audiovisual device that obtains a frontal image (also referred to as a visual image or a C-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. 5 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 YA _- axis direction.

FIG. 6 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. 7 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 the orthogonal coordinate system with the origin O _B and the X and Y axes on the cross section 4, 5 _j,i are the subdivision planes on the cross section 4, and 6 is the above O _A and the subdivision plane 5
The straight lines θ _x,j and θ _y,i that connect the lines 6 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, a fan beam whose main axis direction is θ _y,i is transmitted, and a reflected signal of the transmitted signal from the cross section 4 of the target object is received as a fan beam whose main axis direction is θ _x,j. As a result, subdivisions 5 on the cross section 4 in the directions (θ _xj , θ _y,i ) are obtained as pixels.

FIG. 8 is a detailed explanatory diagram of the fan beam, where 7 is a horizontal beam pattern of a transmission beam;
Θ _x is the beam width of the beam pattern 7, 8 is the vertical beam pattern of the transmit beam, 9 is the main axis of the beam pattern, 10 is the horizontal beam pattern of the receive beam, 11 is the main axis of the beam pattern, 1
2 is the vertical beam pattern of the receiving 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. 7 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. If the beam width of the vertical beam pattern 8 is Δθ _y , approximately 2Θ _Y /Δθ _y transmissions are required.

FIG. 9 is a geometric explanatory diagram showing in more detail the method of visualizing the reflection intensity on the cross section 4, and 13
is the surface irradiated by the i-th transmitting fan beam whose principal axis direction is θ _y, i, 14 is the surface covered by the j-th receiving fan beam whose principal axis direction is θ _x,j , 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 ) η _B = R·sinΘ _Y R·Θ _Y (4) Δx _B = R·sinΔθ _x R·Δθ _x (5) Δy _B = R·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 the Z _A axis, and ξ _B /R≪1 and η _B /R≪1
Assume that

With one transmission in the θ _y,i direction, 5 _1,i , 5 _2,i ,
..., 5 _{KR pixels of KR,i} can be obtained, and in order to image the entire section 4, KT2η _B /Δy _B
2Θ _Y /Δθ _y transmissions are required.

Therefore, if the time interval of transmission is τ _d seconds, it will take at least T=KT·τ _d seconds (7) to image the entire cross section 4.

Next, FIG. 10 is a functional block diagram of the transmission circuit section shown in the above-mentioned document, in which 20 is an oscillator, 21 is a modulator, 22 is a transmission controller, 23 is a delay adder, 24 ₁ , 24 ₂ , ..., 24 _MT is a transmission amplifier, 25 ₁ , 25 ₂ , ..., 25 _MT is a transmission matching circuit, t _T,i is the transmission time of the i-th transmission signal, D _T is the time width of the transmission signal, P (t) is the time width D _T
transmission signal (pulse signal with time width _DT ), P ₁ (t),
P ₂ (t), . . . , P _MT (t) are output signals of the delay adder 23.

The oscillator 20 in FIG. 10 generates a carrier signal with a center frequency f _T , and the modulator 21 generates a pulse signal P(t) with a time width D _T at time t _T,i .
The modulator 21 is controlled by a transmission controller 22, and the time t _T,i and the time width _DT are given by the transmission controller 22 as a pulse signal _DT having a time width _DT . The transmission controller 22 also outputs the vertical principal axis direction θ _y,i of the transmission fan beam to the delay adding circuit 23 as a selection signal θ _y,i . Here, [x] represents a timing or pulse signal regarding x, and (x) represents a selection signal regarding x. The delay adder 23 applies a time delay or a phase delay necessary to form a transmission fan beam whose main axis direction is θ _y,i to each element 2 ₁ , 2 ₂ , ..., 2 _MT of the transmitter array 2. Then, the signal P
(t), P ₁ (t), P ₂ (t),..., P _MT (t)
occurs.

The transmission amplifiers 24 ₁ , 24 ₂ , ..., 24 _MT receive the output signals P ₁ (t), P ₂ (t), P _MT (t) of the delay adder 23
and transmission matching circuits 25 ₁ , 25 ₂ ,
..., 25 After performing tuning and impedance matching with _MT , each element 2 ₁ , 2 of the transmitter array 2
₂ ,...,2 Output the signal to _MT . Each element 2 ₁ , 2
₂ ,...,2 When a signal with an appropriate time delay or phase delay is transmitted from _{the MT} , a transmission fan beam 8 with the vertical principal axis direction θ _y,i as shown in FIG. 8 is formed. Become.

FIG. 11 is a functional block diagram showing details of the delay adder 23, in which 26 is the output terminal of the modulator 21, 27 is the output terminal of the transmission controller 22, 23 ₁ ,
23 ₂ ,..., 23 _MT are delay adding circuits, 28 ₁ ,
28 ₂ ,..., 28 _MT are transmission amplifiers 24 ₁ , 24 ₂ ,
..., 24 _MT input terminal.

The pulse signal P(t) of frequency f _T inputted from the input terminal 26 is sent to the delay adding circuits 23 ₁ , 23 ₂ ,
..., 23 By _MT , each element 2 of the transmitter array 2
₁ , 2 ₂ , ..., 2 The output terminals 28 1 , 2 receive a time delay or phase delay determined by the position coordinates of _{the MTs} and the orientation selection signal θ _y,i input from the input terminal ₂₇ .
8 ₂ ,...,28 _MT has signals P ₁ (t), P ₂ (t),..., P _MT
(t).

FIG. 12 is a functional block diagram of the receiving circuit shown _in the _above -mentioned document.
_MR is a preamplifier, 33 ₁ , 31 ₂ , ..., 31 _MR
is a gate circuit, 32 is a reception controller, 33 ₁ , 33
₂ ,...,33 _MR is an orthogonal demodulator, 34 is a reference signal generator, 35 is a receiving beamformer, 36 is an output terminal, tR _,i is the time when the gate circuit 31 ₁ , 31 ₂ ,..., 31 _MR is opened, D _R is the gate time width, S ^~ ₁ (t), S ^~ ₂
(t), ..., S ^~ _MT (t) are orthogonal demodulators 33 ₁ , 33 ₂ ,
..., 33 The output signal of _MR , Φ _i,j is the output of the beamformer 35.

Each output signal of each element 3 ₁ , 3 ₂ , ..., 3 _MR of the receiver array 3 is sent to a preamplifier 30 ₁ , 30 ₂ , ..., 3
After being amplified to an appropriate level by 0 _MR , the signal is input to orthogonal demodulators 33 ₁ , 33 ₂ , . . . , 33 _MR through gate circuits 31 ₁ , 31 ₂ , . . . , 31 _MR . Gate circuits 31 ₁ , 31 ₂ ,..., 31 _MR is reception controller 3
In the time information t _R,i output from 2, the time width D _R
The reception gate is opened only during the time width D _R according to the pulse signal D _R of the preamplifiers 30 ₁ , 30 ₂ , ..., 3
The output signal of 0 _MR is sent to orthogonal demodulators 33 ₁ , 33 ₂ ,...,
33 Output to _MR .

The reference signal generator 34 includes orthogonal demodulators 33 ₁ , 3
3 ₂ ,..., 33 Outputs a signal with frequency f _R , which serves as a reference signal for _MR . When the frequency displacement due to Doppler shift of the reflected signal from the target object is not so large, f _R =f _T is selected.

The orthogonal demodulators 33 ₁ , 33 ₂ , ..., 33 _MT generate orthogonal envelope signals of the output signals of the gate circuits 31 ₁ , 31 ₂ , ..., 31 _MT , that is, signal components corresponding to the real part and imaginary part of the complex envelope. is determined and output to the receiving beamformer 35. Real part S _I,n (t),
The pair of signals with imaginary part S _Q,n (t) is transformed into a complex signal S ^~ _n (t)
= S _I,n (t) + jS _Q,n (t), the orthogonal demodulators 33 ₁ , 33 ₂ , ..., 33 _MT receive the complex signals S ^~ ₁ (t), S ^~ ₂ (t), respectively. ), S ^~ _MT (t), and the reception beamformer 35 performs time delay or phase delay compensation on the complex signal to form a reception fan beam 10 with the principal axis direction θ _x,j , The output signal Φ _i,j of the beam is output to the output terminal 36 .

FIG. 13 shows orthogonal demodulators 33 ₁ , 33 ₂ , ..., 3
3 is a functional block diagram showing details of the m-th orthogonal demodulator of _MT , 37 is an output terminal of the m-th gate circuit 31 _n , 38 ₁ and 38 ₂ are multipliers, and 3
9 ₁ and 39 ₂ are output terminals of the reference signal generator 34, 4
0 ₁ and 40 ₂ are low-pass filters, and 41 ₁ and 41 ₂ are output terminals of the orthogonal demodulator 33 _n . Input terminal 3
The signal input from 7 is the orthogonal signal cos2πf _R t of frequency f _R output from the reference signal generator 34.
sin2πf _R t and input to low-pass filters 40 ₁ and 40 ₂ , respectively. The low-pass filter divides the real part S _I,n (t) and imaginary part S _Q,n of the envelope.
(t), it is a filter that passes only appropriate low-frequency signals, and the signals S _I,n (t) and S _Q,n (t) are output to the output terminal of the orthogonal demodulator 33 _n . Ru.

FIG. 14 is a functional block diagram showing details of the receiving beamformer 35, 42 ₁ , 42 ₂ ,...,
42 _MR is the output terminal of the orthogonal demodulator 33 ₁ , 33 ₂ ,..., 33 _MR , 43 ₁ , 43 ₂ ,..., 43 _MR is the delay compensation circuit, 45 is the adder, 46 is the absolute value calculator, 47
is an output terminal of the reception beamformer, and 44 is an output terminal of the reception controller 32. Orthogonal demodulator 33 ₁ ,
33 ₂ ,...,33 _MR output signal S ^~ ₁ (t), S ^~ ₂ (t)
，
..., S ^~ _MT (t) is the principal axis direction information θ _x,j of the reception fan beam 10 output from the reception controller 32 and the position of each element ₁ , 3 ₂ , ..., 3 _MR of the receiver array 3 After receiving time delay compensation or phase compensation determined by the coordinates, the signals are added by an adder 45, and the absolute value of the complex signal which is the output of the adder is determined by an absolute value calculator 46. The absolute value Φ _i,j becomes the pixel 5 _j,i of the cross section 4 of the target object.

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

(1) Since signals with the same frequency f _T are used for the transmission signals, it is not possible to shorten the transmission repetition period, and therefore it takes time to form an image of one cross section of the target object. Pass.

(2) The purpose of the cross-fan beam scanning method is to miniaturize the hardware, and if the transmission signal is made to have multiple frequencies, the hardware will increase and the original objective of miniaturization cannot be achieved.

FIG. 15 is an explanatory diagram showing the above-mentioned problem (1) of the conventional method in detail, where 50 is a timing diagram representing the transmission time of the transmission signal, 50 ₁ is the i-th transmission signal, and 50 ₂ is the i-th transmission signal. The i+1th first transmission signal, 50 ₃ is the i+1th second transmission signal,
51 is a time vs. amplitude diagram representing the reflected signal of the i-th transmission signal; 52 is _{a timing diagram representing the timing of the reception gate circuit for the i+1-th first transmission signal 50 2 ;} 53 is a timing diagram showing the timing of the reception gate circuit for the i+1-th second transmission signal 50 ₃ , 53 ₁
is the timing at which the gate circuit opens. Further, in the reflected signal 51, 51 ₁ is a reflected signal portion from a specific cross section 4 of the target object, 51 ₂ is a reflected signal portion received at the time 51 ₂ when the gate is opened, and 51 ₃ is the time when the gate is opened. This is the reflected signal portion received by ₅₁₃ .

For one transmitted signal 50 ₁ , a reflected signal of duration τ _s is generally obtained. As shown in FIG. 15, the transmission time of the i-th transmission signal 50 ₁
From t _T,i , the time required to obtain a reflected signal from a specific cross section 4 of the target object is τ _R , from t _T,i to the transmission time t _T,i+1 of the i+1th transmitted signal. Letting the time τ be the time t _{R,i+1 at which the} reception gate circuit opens in response to the t _i+ 1th transmission signal is approximately t _R,i+1 = t _T,i+1 + τ _R =t _T,i +τ+τ _R (8), which is τ+τ _R after the first transmission time. Therefore, if the time τ is not long enough and τ ₁ is set to 50 ₂ , as shown in the timing diagram ₅₂ of FIG. The reflected signal portion 51 ₂ of the previous i-th transmitted signal is received, and this becomes noise in the reflected signal of the i+1-th transmitted signal, deteriorating the quality of the generated video.

In order to avoid such a phenomenon, the time τ between the i-th transmission time t _T,i and the i+1-th transmission time t _T,i+1 must be set to a sufficiently long time τ ₂ such as 50 ₃ .
It is necessary to choose the value so that it is approximately τ ₂ +τ _R τ _s .

Furthermore, although not shown in FIG. 15, in order to avoid receiving the reflected signal of the i+1th transmitted signal while opening the gate to receive the reflected signal of the i-th transmitted signal, , generally it is necessary to choose such that ττ _R.

Therefore, in general, the repetition time interval τ _P of the transmitted signal needs to be approximately τ _P τ _S −τ _R and τ _P τ _R (9), for example, τ _s = 100 msec,
If τ _R = 10 msec (distance R to object cross section 4 is approximately 7.5 m), τ _P becomes 90 msec, which means that even if the distance to the target cross section is short, the repetition time interval τ _P cannot be shortened. There's a problem.

The present invention has the following advantages: (1) Since the transmission repetition time interval cannot be shortened, it takes time to form an image; (2)
This solves the problem of increasing hardware when trying to increase the number of circuits, allows the transmission repetition time interval to be selected regardless of the reflected signal duration or the distance to the cross section of the target object, and does not involve an increase in hardware. Our aim is to provide superior equipment.

(Means for solving the problem) 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 a beamforming operation. In this case, the present invention relates to an audio-visual apparatus that irradiates the entire cross section of the target object by changing the direction of the transmission beam each time the pulse signal is transmitted, thereby obtaining a front image of the cross section of the target object.

The present invention provides such an audio-visual device,
It is configured with 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
It is determined from the time required for image formation, the frequency type N, and the reflection duration of the reflected signal.

Thirdly, the frequency of the reference signal of the orthogonal demodulator that demodulates the reflected signal is multi-frequencyized into N types, and
Select according to the frequency of the transmitted pulse signal.

(Function) The first transmission pulse signal has N types of frequencies.
It has one frequency f _T,i 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 of a predetermined time width by a gate circuit). The orthogonal demodulator selects a frequency f _{R , i} (for example, f _{T ,i =} f _R,i ) and demodulate the received pulse signal. The demodulated signal is output as a received beam output by beamforming operation.

Next, the i+1-th transmission pulse signal has one frequency f _T,i+1 selected from N types of frequencies. The transmission time interval τ _P of the i+1th transmission pulse signal is the time required for image formation by the reflected signal related to the first transmission pulse signal, the frequency type N, and the reflected signal related to the first transmission pulse. It is determined from the reflection duration of . Thereafter, the target object is converted into an audiovisual image by the same operation.

(Example) An example of the present invention will be described below with reference to the drawings.

1 and 2 are functional block diagrams showing one embodiment of the present invention. In Figure 1, 20 ₁ ,
20 ₂ , . . . , 20 _N are oscillators, 60 is a multiplexer, 61 is a transmission controller, 62 is an input terminal, and 63 is an output terminal. In Figure 2, 3
4 ₁ , 34 ₂ ,..., 34 _N are reference signal generators, respectively;
64 is a multiplexer, 65 is a reception controller, 66
and 67 are input terminals of the reception controller 65. It should be noted that the same functional blocks as in FIGS. 10 and 12 are given the same numbers.

In FIG. 1, N oscillators 20 ₁ , 2
0 ₂ ,...,20 _N are mutually different frequencies f _T,1 , f _T,2 ,
..., f _T,N signals, and the multiplexer 60 is
Frequency command signal output from transmission controller 61
According to f _T,i , a signal of one frequency is selected from among the f _T,1 , f _T,2 , . . . , f _T,N and output to the modulator 21 .

After receiving the reflected signal of the i-1th transmitted signal, the transmission controller 61 calculates a predicted value T^ _{S,i-1 of the time T S ,i-1} required for image formation using the reflected received signal. , applicable
T^ _S,i-1 and the number N of different frequencies and input terminal 6
2, the transmission time of the i-th transmission signal is determined from the predicted value τ^s of the duration τs of the reflected signal.
t _T,i is determined, and a pulse signal [D _T ] with a time width D _T is output to the converter 21. Further, the transmission time t _T,i is outputted to the output terminal 62 as a timing signal [t _T,i ]. The transmission controller 61 also outputs the selection signal f T,i of the center frequency f _{T,1 of the i-th transmission signal to the multiplexer 60 and the output terminal 63, and also outputs the selection signal f T,i} of the center frequency f T,1 of the i-th transmission signal, and A selection signal θ _y,i in the principal axis direction θ _y,i of No. 8 is output to the delay adder 23 .

FIG. 3 is a functional block diagram showing a more detailed configuration example of the transmission controller 61, in which 71 is a video formation time predictor, 72 is a video formation time accumulator, 73 and 74 are registers, and 75 is a register. 74 input terminal, 76 a time interval calculator, 77 a comparator, 78
is a down counter, 79 is a clock generator, 80
is a pulse generator, 81 is an N-ary counter, and 82 is a
The KT base counter 83, 84, 85, and 86 are output terminals.

_The image forming time predictor 71 in FIG _. The formation time accumulator 72 calculates the cumulative time required for image formation for the reflected signals ^of N consecutive transmitted signals according to the number _N of different frequencies _. calculate. However, it is assumed that the transmission signal is given by repeating a pulse signal train having N different center frequencies. That is, it is assumed that there are no pulse signals having the same center frequency in the N consecutive pulse signal trains.

Registers 73 and 74 record the τ^ and τ^s, respectively,
The comparator 77 compares the recorded τ^ and τ^s and outputs the result to the time interval calculator 76. The time interval calculator 76 calculates the time interval τ P,i from t _T,i-1 to t _{T, i} as follows, according to the output result of the comparator 77.

When τ^≧τ^s, τ _P,i = T^ _S,i-1 When τ^<τ^s, τ _P,i = T^ _S,i-1 + (τ^s−τ^ ) The time interval information τ _P,i calculated above is set as the initial value of the down counter 78, and the down counter 78 starts counting at the i-1th transmission time t _Ti-1 , and when the count value reaches zero. When the value is reached, a timing signal [t _T,i ] indicating the i-th transmission time is output to the output terminal 83.

The pulse generator 80 receives the time of the down counter 78.
The time width of rising timing output at t _T,i
It generates a pulse signal [D _T ] of D _T and outputs it to the output terminal 84.
Output to.

The N-ary counter 81 and the KT-ary counter 82 are
This counter uses the timing output of the down counter 78 as a clock input, and the output of the N-ary counter 81 is outputted to the output terminal 85 as the selection signal f _{T, i} of the i-th transmission frequency f T,i, 8
The output of No. 2 is outputted to the output terminal 86 as a selection signal θ _y,i in the principal axis direction θ _y,i of the i-th transmission fan beam 8 .

The transmission timing signal [t _Ti ] of the output terminal 83 is
The pulse signal [D _T ] at the output terminal 84 is output to the output terminal 63 in FIG _.
is output to the multiplexer 60 and to the output terminal 63. Output terminal 8
The direction selection signal θ _y,i of No. 6 is output to the delay adder 23 .

Next, the output terminal 63 in FIG. 1 is connected to the input terminal 66 in FIG.
5, the i-th transmission timing t _T,i and the frequency selection signal f _T,i of the i-th transmission signal are input.

The reception controller 65 uses the information t _T,i and f _T,i and the distance information R to the target object cross section 4 input from the input terminal 67 to determine the reception gate circuits 31 ₁ , 31
₂ ,...,31 Find the time t _R,i at which the gate of _MR is opened, and output a pulse signal D _R with a time width D _R.

In addition, N reference signal generators 34 ₁ , 34 ₂ ,
…, 34 _MR has different frequencies f _R,1 , f _R,2 , …,
Generate a signal f _R,,N . Usually f _R,i = f _T,1 , f _R,2 =
f _T,2 ,..., f _R,N = f _T,R .

The multiplexer 64 selects the f _{R,1 ,}
A signal with one corresponding frequency is selected from f _R,2 ,..., f _R,N and the orthogonal demodulators 33 ₁ , 33 ₂ , 33 _MR
Output to.

FIG. 4 is a functional block diagram showing a more detailed configuration example of the reception controller 65, and 90 is an input terminal 6.
Input terminal connected to 7, 91 is a reception time calculator,
92 is an input terminal, 93 is a counter, 94 is an encoder, 95 ₁ , 95 ₂ , . . . , 95 _L is each down counter, 96 is a clock generator, 97 ₁ , 97 ₂ ,
..., 97 _L is a pulse generator, 98 is an OR circuit, 99
is the output terminal, 100 is the input terminal, 101 ₁ , 10
1 ₂ ,...,101 _L is a register, 102 is an OR circuit,
103 is an output terminal.

The reception time calculator 91 calculates the i-th
From the th transmission time t _T,i , the reception gate circuit 31 ₁ , 31
₂ ,...,31 The time τ _R until opening _{the MR} is defined as τ _R = R/
C (where C is the speed of sound), and outputs the τ _R value to the initial value input terminals of the down counters 95 ₁ , 95 ₂ , . . . , 95 _L.

The counter 93 is a cyclic counter that is updated by the i-th transmission timing signal t _T,i input from the input terminal 92, and the encoder 94
encodes the state of the counter 93, and the output of the encoder 94 is the down counter 95 ₁ , 95 ₂ ,
..., 95 _L as well as the initial value load signal and count start signal, and the registers 101 ₁ , 1
01 ₂ , . . . , 101 _L input data load signals.

Every time the timing signal t _T,i is input,
One of the down counters 95 ₁ , _{95 2} , . Start counting. If the down counter selected when inputting t _T,i is 95l, then 95l
is the time when the receiving gate is opened after τ _R after the input of t _T,i
A timing signal [t _i,R ] that provides t i, _R is output to the pulse generator 97l, which generates a pulse signal D R with a time width D _R , and outputs the pulse signal D _R through the R circuit 98 to the output terminal. 99. Output terminal 99
gives a timing signal to open the gates of the receiving gate circuits 31 ₁ , 31 ₂ , . . . , 31 _MR .

Next, the transmission signal frequency selection signal f _T,i input from the input terminal 100 is sent to the register 101 _L according to the output of the encoder 94 as a timing signal.
It is loaded and stored when t _T,i is input. The stored selection signal f _T,i corresponds to the pulse duration of the pulse signal generator 97l, i.e. the receiving gate path 31 ₁ ,
31 ₂ , ..., 31 are outputted to the output terminal 103 through the OR circuit 102 while _{the MR} is open.
The signal output from the output terminal 103 becomes the selection signal f _R,i of the reference signal frequency of the multiplexer 60 .

Note that the down counters 95 ₁ , 95 ₂ ,..., 95
_L and the number _L of registers 101 ₁ , 101 ₂ , _. . .
It depends on the number of timing signals t _T,i and frequency selection signals f _T,i input from 0, and if the time interval of timing signals t _T,i is τ _P , then L≧II _o [τ _R /τ _P ].
However, Io _· [x] represents an integer larger than x and closest to x.

Further, in the fourth configuration example, the pulse generator 9
There are no two or more pulse signals output from 7 ₁ , 97 _{2 . .} . , 91 _L at the same time. In other words, it is assumed that the pulse signals do not overlap.

The embodiments shown in FIGS. 1 to 4 above are based on the assumption that a crossing linear array as shown in FIGS. 5 and 6 is used as the transducer array.
Although it is assumed that the transmit beam and the receive beam are also fan beams as shown in FIG. 8, the present invention irradiates the entire cross section of the target object by changing the direction of the transmit beam each time a transmit signal is transmitted. Thus, 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 in a cross section of a target object.

(Effects of the Invention) As described above in detail, according to the present invention, the frequency of the transmission signal is multi-frequencyized into N types, and the transmission interval is set according to the time required for image formation and the frequency type N. The reference signal for the reception quadrature demodulator is multi-frequency in N types, determined rationally from the relationship with the reflection duration, and selected according to the frequency of the transmission signal, so the distance to the target object and the reflection duration can be adjusted. Transmission signals can be transmitted at short intervals without being limited by time, and all reflected waves can be orthogonally demodulated using the same orthogonal demodulator regardless of frequency, resulting in less hardware. It becomes possible to obtain an acoustic frontal image at high speed without significantly increasing the size.

[Brief explanation of drawings]

FIG. 1 is a functional block diagram showing an embodiment of a transmitting circuit section of an audio-visual apparatus according to the present invention, FIG. 2 is a functional block diagram showing an embodiment of a receiving circuit section of an audio-visual apparatus according to the present invention, and FIG. 1 is a functional block diagram showing a detailed embodiment of the transmission controller in the functional block diagram of FIG. 1; FIG. 4 is a functional block diagram showing a detailed embodiment of the receiving controller in the functional block diagram of FIG. 2; Figure 5 is an external view of the transducer array for the cross-fan beam scanning method, Figure 6 is an arrangement diagram showing the configuration of the transmitter array and receiver array in Figure 5, and Figure 7 is the cross-fan beam scanning method. Figure 8 is a geometric diagram showing the principle of the scanning method. Figure 8 is a diagram showing the transmitting beam pattern and receiving beam pattern in the cross-fan beam scanning method. Figure 9 is a geometric diagram showing the method of image formation in the cross-fan beam scanning method. 10 is a functional block diagram of a transmitting circuit of the conventional cross-fan beam scanning method, FIG. 11 is a detailed functional block diagram of a delay adder in the functional block diagram of FIG. 10, and FIG. 12 is a conventional 13 is a detailed functional block diagram of the orthogonal demodulator in the functional block diagram of FIG. 12, and FIG. 14 is a functional block diagram of the receiving circuit of the crossfan beam scanning method in FIG. FIG. 15 is a detailed functional block diagram of the receive beamformer and a timing diagram showing problems with the conventional method. 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 the target object cross section, 7...Transmission horizontal beam pattern, 8
... Transmission vertical beam pattern, 9 ... Main axis direction of transmission vertical beam, 10 ... Reception horizontal beam pattern, 11 ... Principal axis direction of reception horizontal beam, 12 ... Reception vertical beam pattern, 20 ... ...Oscillator, 21 ...Modulator, 20
₁ , 20 ₂ ,..., 20 _N ...Oscillator, 22...
Transmission controller, 23... Delay adder, 24 ₁ , 24
₂ ,...,24 _MT ...transmission amplifier, 25 ₁ , 25 ₂ ,
..., 25 _MT ... Transmission matching circuit, 23 ₁ , 2
3 ₂ ,..., 23 _MT ...delay addition circuit, 30 ₁ , 30
₂ ,...,30 _MR ...preamplifier, 31 ₁ , 31 ₂ ,
..., 31 _MR ... gate circuit, 32 ... reception controller, 33 ₁ , 33 ₂ , ..., 33 _MR ... orthogonal demodulator,
34... Reference signal generator, 34 ₁ , 34 ₂ ,..., 3
4 _N ... Reference signal generator, 35... Reception beam former, 38 ₁ , 38 ₂ ... Multiplier, 40 ₁ , 40 ₂ ...
...Low pass filter, 43 ₁ , 43 ₂ ,..., 43 _MR
... Delay compensation circuit, 45 ... Adder, 46 ... Absolute value calculator, 60 ... Multiplexer, 61 ...
Transmission controller, 64... Multiplexer, 65...
Reception controller, 71... Image formation time predictor, 72
...Video formation time accumulator, 73, 74...Register, 76...Time interval calculator, 77...Comparator, 78...Down counter, 81...N-ary counter, 82...KT-ary counter, 80... Pulse generator, 91... Reception time calculator, 93... Counter, 94... Encoder, 95 ₁ , 95 ₂ ,...,
95 _L ... Down counter, 96... Clock generator, 97 ₁ , 97 ₂ ,..., 97 _L ... Pulse generator, 98... OR circuit, 101 ₁ , 101 ₂ ,...,
101 _L ...Register, 102...OR circuit.

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 device 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 N transmission pulses are transmitted in time series corresponding to the N types of frequencies. , the transmission time interval τp between the i-1st transmission pulse and the i-th transmission pulse,
i is the predicted value Ts^ of the time required for image formation using the reflected signal of the i-1th transmission pulse, i-1
From the cumulative predicted value of the time required to form an image for N reflected signals calculated from τ^ = _N 〓 ⁱ⁼¹ Ts^, i-1 and the predicted value of the reflection duration of each reflected signal τs^, τ^ When ≧τs^, τ^p, i = Ts^, i-1 When τ^<τs^, τp, i = Ts^, i-1 + τs^-τ^), and orthogonal to demodulate the reflected signal. An audio-visualization method characterized in that the frequency of a reference signal of a demodulator is multi-frequencyized into N types, and the frequency is selected in accordance with the frequency of a transmission pulse signal.