JP3136635B2 - Exploration method and device - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an exploration method and apparatus, and more particularly, to an exploration method based on the same principle as a pulse echo method, such as an acoustic exploration using ultrasonic waves, and an apparatus therefor.

[0002]

2. Description of the Related Art Conventionally, as shown in FIG.
, An ultrasonic pulse is periodically transmitted from the receiver, a pulse echo reflected and returned by the reflector 92 is captured at the receiving point 93, and the position of the boundary surface where the density of the medium changes is measured based on the intensity of the echo. The so-called pulse echo method is widely known.

[0003] In recent years, ultrasonic tomography apparatuses have become extremely popular among medical non-invasive measuring instruments, and have greatly contributed to improvement of diagnostic accuracy. The operating principle of an ultrasonic diagnostic apparatus represented by an ultrasonic tomography apparatus is the same as the pulse echo method widely known as the principle of active sonar. Here, the mode for observing the time waveform of the intensity of the reflected wave is the mode A (see FIG. 6). The mode for scanning the contact in a one-dimensional manner, setting a threshold value, and observing a two-dimensional image in the scanning direction and the depth direction. Is referred to as a B mode (see FIG. 7), and a mode in which scanning is performed two-dimensionally to observe a two-dimensional image at the same depth is referred to as a C mode (see FIG. 8).

Therefore, by using an ultrasonic diagnostic apparatus and selecting an A mode, a B mode, or a C mode according to the type of a target diagnosis, a diagnosis inside the human body can be performed without damaging the human body. Can be. Also, by using an ultrasonic flaw detector based on the same principle, it is possible to inspect the presence or absence of flaws inside various structures.

[0005]

The spatial resolution of the above-mentioned ultrasonic diagnostic apparatus is about 5 mm, which is too low compared to the spatial resolution (about 1 mm) required for applications such as early detection of cancer. Therefore, there is a disadvantage that the method cannot be applied to uses such as early detection of cancer. Further, in order to increase the spatial resolution (to increase the resolution), it is conceivable to shorten the length of the burst wave of the transmission ultrasonic wave. Specifically, since the burst waveform can be easily shortened by increasing the frequency of the ultrasonic wave, it is generally selected to shorten the burst wave by selecting a high frequency as the frequency of the transmission ultrasonic pulse. You. However, when the frequency is increased, the attenuation of the ultrasonic wave becomes remarkable, and a new inconvenience occurs that the ultrasonic wave cannot be applied to the diagnosis of the deep part of the human body. In addition, in order to shorten the burst waveform without increasing the frequency, it is conceivable to use a probe that can output a short burst waveform.However, to develop a new probe, research the material by trial and error. As a result, there is a disadvantage that the development is inevitably prolonged, and cannot be applied immediately at present.

Further, as a method for improving the spatial resolution without increasing the frequency of the ultrasonic pulse, a fast Fourier transform operation (hereinafter, referred to as a “transform”) based on a transmission waveform and a reception waveform is described.
A method of obtaining an impulse response by performing an FFT operation) is known. However, in addition to the restriction that the number of data samples must be 2 ⁿ , there is a disadvantage that the arithmetic unit becomes large and the real-time property is lost. Is not used much.

Although only the search method in the ultrasonic diagnostic apparatus has been described above, the ultrasonic flaw detector, radar and the like have the same disadvantages.

[0008]

SUMMARY OF THE INVENTION The present invention has been made in view of the above-mentioned problems, and a novel exploration method and apparatus capable of improving the spatial resolution without changing the transmission wave and realizing the real-time property. It is intended to provide.

[0009]

According to a first aspect of the present invention, there is provided a search method in which a transmission wave is recorded as a pulse train composed of a plurality of pulses, and a reception wave is recorded with a predetermined pulse width. And a deconvolution operation based on the peak value of each pulse of the pulse train is performed on the obtained data train to obtain an impulse response of the boundary surface.

According to a second aspect of the present invention, there is provided an exploration apparatus comprising: a pulse train recording means for recording a transmission wave as a plurality of pulse trains; a reception wave conversion means for converting a reception wave into a data train having a predetermined pulse width; Calculating means for performing a deconvolution operation on the obtained data train based on the peak value of each pulse of the pulse train recorded in the pulse train recording means to obtain an impulse response of the boundary surface. However, the calculating means may include a pulse train recording means.

According to a third aspect of the present invention, in the exploration apparatus, the calculating means includes a delay means having a number of stages determined based on the number of pulses recorded in the pulse train recording means, Multiplying means for multiplying a constant determined based on a value, and multiplying means for multiplying a data string by a constant determined based on a peak value of a predetermined pulse in the pulse train;
Adding means for performing addition based on the multiplication result output from each multiplication means to obtain an impulse response of the boundary surface and supplying the impulse response to the delay means.

According to a fourth aspect of the present invention, in the exploration apparatus, the arithmetic means is provided with delay means having a number of stages determined based on the number of pulses recorded in the pulse train recording means and weighting determined based on a peak value of a predetermined pulse in the pulse train. Accumulating means having a plurality of input terminals for supplying an output signal and a data string from each stage of the delay means to each input terminal of the accumulating means, and providing the accumulated addition output from the accumulating means. Feeding delay means.

[0013]

According to the first aspect of the present invention, when the transmitting wave is transmitted, the reflected wave is received, and the position of the boundary surface where the density of the medium changes based on the received wave is measured. While recording as a pulse train consisting of a plurality of pulses, the received wave is obtained as a data train of a predetermined pulse width, and the obtained data train is subjected to deconvolution based on the peak value of each pulse in the pulse train. Since the impulse response of the boundary surface is obtained, high spatial resolution can be achieved without using a special transmitter and receiver. Then, even in a medium having a large attenuation rate in a high frequency band, the exploration range can be expanded and the spatial resolution can be increased by lowering the pulse frequency of the transmission wave and increasing the sampling rate of the reception wave. Further, unlike the FFT processing, an impulse response can be obtained in real time.

According to the second aspect of the present invention, when the transmitting wave is transmitted, the reflected wave is received, and the position of the boundary surface where the density of the medium changes based on the received wave is measured, the received wave is converted. Means for converting the received wave into a data train having a predetermined pulse width,
The operation means performs a deconvolution operation based on the peak value of each pulse of the pulse train recorded in the pulse train recording means with respect to the data train obtained by the reception wave conversion means to obtain the impulse response of the boundary surface. High spatial resolution can be achieved without using special transmitters and receivers. Then, even in a medium having a large attenuation rate in a high frequency band, the exploration range can be expanded and the spatial resolution can be increased by lowering the pulse frequency of the transmission wave and increasing the sampling rate of the reception wave. Further, F
Unlike the FT processing, an impulse response can be obtained in real time.

According to the search device of the third aspect, the arithmetic means can be constituted only by the delay means, the multiplication means and the addition means, and no special electronic parts are required.
The exploration device can be simply configured, and the same operation as the exploration device of claim 2 can be achieved. According to the exploration apparatus of claim 4, since the operation means can be constituted only by the delay means and the accumulative addition means and does not require any special electronic parts, the exploration apparatus can be constituted simply and in addition, The same operation as that of the surveying device can be achieved.

[0016]

BRIEF DESCRIPTION OF THE DRAWINGS FIG. FIG. 1 is a flowchart showing an ultrasonic search method as an embodiment of the search method of the present invention. In step SP1, an ultrasonic wave having a predetermined pulse frequency is transmitted from a transmitter, and in step SP2, the transmitted ultrasonic wave is transmitted. Is obtained as a pulse train composed of a plurality of pulses, and step SP3
And obtains and holds the peak value of each pulse in the pulse train. Then, in step SP4, the reflected wave is received by the receiver, and in step SP5, the received waveform is sampled at a predetermined sampling rate to obtain a data train. In step SP6, each pulse of the pulse train is compared with the data train. The deconvolution operation based on the peak value is performed to obtain the impulse response of the boundary surface, and the process of step SP4 is repeated again.

More specifically, step SP3
Is the peak value x (τ) of each pulse obtained at x0,
x1,. . . xi, and the impulse response of the interface is g
0, g1,. . . gj, and the data sequence y (t) finally obtained in step SP5 is represented by y0, y1,. . .
Assuming that yk (where i, j, and k are natural numbers), y (t) is an integrated value of a multiplication result of the transmitted ultrasonic wave x (τ) and the impulse response g (t−τ). From y
(T) = x (τ) · g0 + x (τ) · g1 +. . . + X
(Τ) · gj. Then, the data string y (t)
Since the first data y0 is equal to x0 · g0, an impulse response g0 is obtained by performing a deconvolution operation of y0 / x0. Also, the second data y
Since 1 is equal to x1 · g0 + x0 · g1,
By performing a deconvolution operation of (y1-x1.g0) / x0, an impulse response g1 is obtained. In addition, 3
The second data y2 is x2 · g0 + x1 · g1 + x0 · g
2 so that (y1−x2 · g0−x1 ·
By performing a deconvolution operation of g1) / x0, an impulse response g2 is obtained. Hereinafter, similarly, every time data is obtained, an impulse response can be sequentially obtained based on a known peak value and an already obtained impulse response.

As is apparent from the above description, an impulse response can be obtained immediately every time data is obtained,
Real-time processing can be achieved. Further, the resolution can be easily increased by lowering the frequency of the transmission pulse to reduce the attenuation and increasing the sampling rate for obtaining the data string.

[0019]

Embodiment 2 FIG. 2 is a block diagram showing a main part of an acoustic sounding device as one embodiment of the sounding device of the present invention. The transmitted pulse x (τ) is composed of (i + 1) pulse trains. The peak value of each constituent pulse is x0, x
1,. . . xi. Note that these peak values are obtained, for example, by sampling the transmission pulse x (τ) at a predetermined sampling rate, but the peak values obtained in advance may be held.

A subtractor 1 having as one input a received data sequence obtained by sampling a received ultrasonic wave at a predetermined sampling rate by a sampling circuit 6.
, A multiplier 2 that performs 1 / x0 multiplication using the output of the subtracter 1 as an input, and i-stage delay units 31, 32,. . . 3i and the peak values x1 and x of the corresponding pulses with the output from each stage of the delay device as an input
2,. . . xi multipliers 21, 22,. . . 2
i and multipliers 21, 22,. . . An adder 4 receives the output of 2i as an input, and uses the output as the subtraction input of the subtractor 1. The output of the multiplier 2 is output to the outside as an obtained impulse response.

The operation of the acoustic sounding device having the above configuration is as follows. When the received data sequence y (t) is y0, y1,. . .
yk, the unknown impulse responses are g0, g1,. . . gj
Then, y (t) = x (τ) · g0 + x (τ) · g1
+. . . + X (τ) · gj, and the data string y (t) is sequentially supplied to the multiplier 2 through the subtractor 1 and output to the outside as an impulse response.
1, 32,. . . 3i. The outputs from each stage of the delay unit are respectively output to multipliers 21, 22,. . . 2i, the multiplication result is supplied to the adder 4, and the addition result is obtained.
The result of the addition is supplied to the subtractor 1 as a subtraction value.

Therefore, at the time when the first data y0 is obtained, since the output from each stage of the delay unit is 0, the addition result output from the adder 4 is 0. By performing the operation of / x0, an impulse response g0 can be obtained. Next data y1
Is obtained, the impulse response g0 is output from the delay unit 31, and the peak value x1
Is multiplied and added to the subtracter 1 in a state of being added in the adder 4, so that (y1-x1 · g0) / x0
By performing the above calculation, an impulse response g1 can be obtained.

In the same manner, a corresponding impulse response can be obtained each time new data is obtained.

[0024]

[Specific example] The transmission pulse x (τ) is 1, 3, 5, −1, −
4, if the impulse response measured by another method is 2, 4, -2, 1, the received data train y
(T) is 2,10,20,13, -19, -9,7,-
It becomes 4. When the first data 2 is obtained, the operation of 2/1 is performed, so that the impulse response becomes 2
become. When the next data 10 is obtained, (10−
Since the calculation of (2 × 3) / 1 is performed, the impulse response becomes 4. When the third data 20 is obtained,
Since the calculation of (20−2 × 5−4 × 3) / 1 is performed, the impulse response becomes −2. When the fourth data 13 is obtained, {13-2 × (-1) -4 × 5-(−
2) Since an operation of × 3｝ / 1 is performed, the impulse response becomes 1. When the fifth data -19 is obtained, ｛−19−2 × (−4) −4 × (−1) − (− 2)
Since the calculation of × 5-1 × 3｝ / 1 is performed, the impulse response becomes zero. When the sixth data -9 is obtained, ｛−9−4 × (−4) − (− 2) × (−1) −1 ×
Since the calculation of 5-0 × 3｝ / 1 is performed, the impulse response becomes 0. When the seventh data 7 is obtained,
｛7-(-2) × (-4) -1 × (-1) -0 × 5-0
× 3｝ / 1, the impulse response is 0
become. When the eighth data -4 is obtained, ｛−
4-1 × (−4) −0 × (−1) −0 × 5-0 × 3} /
Since the operation of 1 is performed, the impulse response becomes 0.

As is apparent from the above example, an impulse response can be obtained in real time and accurately based only on the pulse train of the transmission pulse and the received data train. In addition, since the attenuation can be reduced by lowering the pulse frequency of the transmission pulse, and the resolution can be increased by increasing the sampling rate and increasing the number of pulses constituting the transmission pulse train, high resolution can be achieved over a wide range. Acoustic exploration can be achieved. further,
Since no special electronic components are required, the acoustic search device can be easily configured.

However, in this embodiment, the output of the subtracter 1 is directly supplied to the delay unit, and the respective multipliers perform multiplication in consideration of 1 / x0. It is possible to provide a multiplier for multiplying x0.

[0027]

[Embodiment 3] FIG. 3 is a block diagram showing a main part of an acoustic sounding device as another embodiment of the sounding device of the present invention.
The stage delay units 31, 32,. . . 3i are connected in series with the subtractors 11, 12,. . . 1i, and a multiplier 2 for multiplying the output from the delay unit 3i at the last stage by 1 / x0. The peak values x1, x2,. . . xi and the corresponding subtracters 1i, 1 (i-1),. . . 11 are supplied as subtraction values to multipliers 21, 22,. . . 2i are arranged. Note that the output from the multiplier 2 is directly output as an impulse response.

Therefore, in this embodiment, the first data y0 is output from the delay unit 3i at the last stage, and the multiplier 2 multiplies 1 / x0 to obtain the first impulse response g0. . Then, this impulse response g0 is supplied to each multiplier to obtain a subtraction value to be supplied to the corresponding subtractor, so that a value obtained by subtracting the value corresponding to the impulse response g0 is output from each subtractor, It is supplied to the next stage delay unit. Then, the value g0 · x1 corresponding to the impulse response g0 from the second data y0
Is output from the delay unit 3i in the final stage, the multiplier 2 performs 1 / x0 multiplication to obtain a second impulse response g1. Hereinafter, similarly, by simply multiplying the value sequentially output from the delay unit 3i at the last stage by 1 / x0 by the multiplier 2, a corresponding impulse response can be obtained.

Further, in this embodiment, even if the number of pulses constituting the pulse train of the transmission pulse is increased, it is only necessary to increase the number of delay units and subtracters connected in the pipeline. Can easily cope with the increase.

[0030]

[Embodiment 4] FIG. 4 is a block diagram showing a main part of an acoustic search device as still another embodiment of the search device of the present invention, and i-stage delay units 31, 32,. . . 3i and a cumulative adder 5, wherein the cumulative adder 5 is 1 / x0, x1 / x0, x
2 / x0,. . . xi / x0 multiplication input units 50, 51, 52,. . . 5i, and the output from the accumulator 5 is supplied to the delay unit 31. The data sequence y (t) is supplied to the multiplication input unit 50, and the output from each delay unit is supplied to the corresponding multiplication input unit. The output from the accumulator 5 or the output from any one of the delay units is directly output as an impulse response.

Therefore, in this embodiment, the impulse response g0 obtained by multiplying the first data y0 by 1 / x0 by the multiplier 50 is output from the accumulator 5 as it is. . Then, the multiplier 51 multiplies the value obtained by multiplying the second data y0 by 1 / x0 by 1 / x0 and multiplies the impulse response g0 by −x1 / x0 by the multiplier 51. Since the obtained values are cumulatively added, the second impulse response g
1 is output. Hereinafter, a corresponding impulse response is similarly output from the accumulator 5. You.

The present invention is not limited to the above-described embodiment, and can be applied to various fields such as an ultrasonic diagnostic apparatus, a sonar, a radar, and the scope of the present invention without changing the gist of the present invention. It is possible to make various design changes within.

[0033]

As described above, according to the first aspect of the present invention, not only a high spatial resolution can be achieved without using a special transmitter and a receiver, but also a medium having a large attenuation rate in a high frequency band. Even so, by lowering the pulse frequency of the transmitted wave and increasing the sampling rate of the received wave, it is possible to achieve an expanded search range and higher spatial resolution, and furthermore, F
Unlike the FT processing, there is a specific effect that an impulse response can be obtained in real time.

According to the second aspect of the present invention, not only a high spatial resolution can be achieved without using a special transmitter and receiver, but also a transmission wave can be obtained even if the medium has a large attenuation rate in a high frequency band. By increasing the sampling frequency of the received wave and lowering the pulse frequency, it is possible to achieve a wider search range and higher spatial resolution, and, unlike FFT processing, obtain a real-time impulse response. Has the effect of

The invention of claim 3 has a specific effect that the exploration apparatus can be simply constructed in addition to the effect of claim 2. The invention of claim 4 also has a unique effect that the exploration device can be simply configured in addition to the effect of claim 2.

[Brief description of the drawings]

FIG. 1 is a flowchart showing an ultrasonic search method as one embodiment of a search method of the present invention.

FIG. 2 is a block diagram showing a main part of an acoustic search device as one embodiment of the search device of the present invention.

FIG. 3 is a block diagram showing a main part of an acoustic search device as another embodiment of the search device of the present invention.

FIG. 4 is a block diagram showing a main part of an acoustic search device as still another embodiment of the search device of the present invention.

FIG. 5 is a schematic diagram illustrating the principle of the pulse echo method.

FIG. 6 is a schematic diagram illustrating a mode for observing a temporal waveform of the intensity of a reflected wave.

FIG. 7 is a schematic diagram illustrating a mode in which a contact is scanned one-dimensionally, a threshold is provided, and a two-dimensional image in a scanning direction and a depth direction is observed.

FIG. 8 is a schematic diagram illustrating a mode in which scanning is performed two-dimensionally and a two-dimensional image at the same depth is observed.

[Explanation of symbols]

 1, 11, 12,. . . 1i Subtractors 2, 21, 22,. . . 2i multipliers 31, 32,. . . 3i delay unit 4 adder 5 cumulative adder 51, 52,. . . 5i Multiplication input unit 6 Sampling circuit

──────────────────────────────────────────────────続 き Continuation of front page (56) References JP-A-60-31738 (JP, A) JP-A-1-212543 (JP, A) JP-A-4-125484 (JP, A) JP-A-61- 95265 (JP, A) JP-A-60-113177 (JP, A) Patent 2718222 (JP, B2) (58) Fields investigated (Int. Cl. ⁷ , DB name) G01S 7/00 G01S 13/00 G01S 15 / 00 G01N 29/00

Claims (4)

(57) [Claims] 1. An exploration method for transmitting a transmission wave, receiving a reflected wave, and measuring a position of a boundary surface on which a density of a medium changes based on the received wave. And the received wave is obtained as a data train having a predetermined pulse width, and the obtained data train is subjected to deconvolution based on the peak value of each pulse in the pulse train to obtain an impulse response of the boundary surface. An exploration method characterized in that: 2. An exploration apparatus that transmits a transmission wave, receives a reflected wave, and measures the position of a boundary surface where the density of a medium changes based on the received wave, and records the transmission wave as a plurality of pulse trains. Pulse train recording means, received wave converting means (6) for converting a received wave into a data stream having a predetermined pulse width, and pulse train recording means (2, 21) for the data train obtained by the received wave converting means (6). , 22, ... 2i, 50,5
1,52,. . . Operation means (1, 11, 1) for performing a deconvolution operation based on the peak value of each pulse of the pulse train recorded in 5i) to obtain an impulse response of the boundary surface
2,. . . 1i, 2, 21, 22,. . . 2i, 31,
32,. . . 3i, 4, 5, 50, 51, 52,. . .
5i). 3. An arithmetic unit comprising: a pulse train recording unit (2, 2);
1, 22,. . . 2i) the number of stages of delay means (31, 32,... 3i) determined based on the number of pulses recorded
Multiplication means (2) for multiplying the delay output from each stage of the delay means (31, 32, ... 3i) by a constant determined based on the peak value of each pulse in the pulse train; Multiplication means (21, 22, ... 2i) for multiplying the data sequence by a constant determined based on the peak value, and multiplication results output from the respective multiplication means (2, 21, 22, ... 2i) 3. The exploration apparatus according to claim 2, further comprising adding means (4) for performing addition to obtain an impulse response of the boundary surface and supplying the impulse response to the delay means. 4. The arithmetic means comprises pulse train recording means (50,
51, 52,. . . 5i) delay means (31, 32,... 3i) of the number of stages determined based on the number of pulses recorded
And cumulative addition means (5, 50, 51, 52,... 5i) having a plurality of input terminals to which a weight determined based on the peak value of a predetermined pulse in the pulse train is set. 5) input terminals (50, 51, 5)
2,. . . 5i) includes delay means (31, 32,... 3).
The exploration apparatus according to claim 2, wherein the output signal and the data string from each stage of i) are supplied, and the cumulative addition output from the cumulative addition means (5) is supplied to the delay means (31).