JPH08327613A - Method and system for electron scanning ultrasonic inspection - Google Patents

Abstract

PURPOSE: To discriminate between a real image formed by a main beam and a virtual image formed by grating globe easily with no error. CONSTITUTION: A receiving signal from an array type probe 1 is delayed and added and then split into two signals which are passed, respectively, through filters 31a, 31b having different frequency band. They are then fed, respectively, to signal processing circuits 26a, 26b where the peak value and propagation time are measured respectively. The measurements are held, along with the positional information of the probe 1, in a memory 28. After a specimen is scanned, the intensity of echo caused by the split signal and the position of echo source are determined based on each peak value, propagation time and the positional information of probe held on the memory 28. The positions of respective echo sources are presented individually on an image display 29.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an electronic scanning ultrasonic inspection method and apparatus using an array type probe, and more particularly to removing a grating lobe generated during phase control of the array type probe. The present invention relates to an electronic scanning ultrasonic inspection method and apparatus suitable for performing the above.

[0002]

2. Description of the Related Art A conventional electronic scanning ultrasonic inspection apparatus using an array type probe is constructed as shown in FIG.
In FIG. 5, reference numeral 1 denotes an array type probe, and as shown in FIG. 6, n ultrasonic transducers (also simply referred to as transducers) 1 ₁ ,
1 ₂ ... 1 _n are arranged in parallel at equal intervals d. In the ultrasonic wave transmission, the transmission delay control circuit 21 controls the timing of the transducer drive by the transmission drive circuit 24 connected to the transducers 1 ₁ , 1 _2, ... 1 _n constituting the array type probe 1. Then, it is electronically delayed so that the phases are aligned in a target inspection direction or a focusing position. Also in the ultrasonic wave reception, after the reception signals of the respective transducers 1 ₁ , 1 _2, ... 1 _n , which are analog signals, are amplified by the amplifier 23, they are desired by the reception delay circuit 22 controlled by the reception delay control circuit 27. Delay by the delay time. Then, the adder 25 adds them to obtain one signal. In this way, by individually delay-controlling each transducer 1 ₁ , 1 _2, ... 1 _n that configures the array type probe 1 during transmission and reception, it is possible to deflect the ultrasonic beam in a desired direction. It is possible to focus the ultrasonic beam and perform inspection with higher accuracy.

The crest value and propagation time of the output signal of the adder 25 are measured by the signal processing circuit 26, and the measured value is held in the memory 28. Further, a scanner 30 is attached to the array type probe 1 so that an object (not shown) can be scanned with an ultrasonic beam, and the array type probe 1 at the time of transmitting and receiving the ultrasonic beam is also provided. The position information of the (scanner 30) is held in the memory 28. Then, the echo intensity and the echo source position are obtained from the crest value and the propagation time held in the memory 28 and the position information of the array type probe 1, and the echo source position is displayed on the image display device 29. This makes it possible to visually recognize the echo source position. The echo intensity and the echo source position are obtained, for example, by an arithmetic circuit (not shown) provided between the memory 28 and the image display device 29.

[0004]

However, in the above-mentioned prior art, the array type probe 1 is deflected by deflecting the ultrasonic beam by controlling the phase of the individual transducers 1 ₁ , 1 ₂ ... 1 _n constituting the array type probe 1. When used in a focused manner, there were the following problems. That is, the distance d between the transducers 1 ₁ , 1 _2, ... 1 _n
When but longer than the wavelength λ of the ultrasonic wave, the wavefront 51 on the arc by ultrasound issued from the transducers ₁ 1, 1 ₂ ... 1 _n, as shown in FIG. 7, a main beam that can be a target direction besides wavefront 52 MB, known to each transducer 1 _1, 1 ₂ ... 1 ultrasonic phase issued from _n occurs in a direction aligned shifted by one wavelength sub beam wavefront 53 is formed (This is called the grating lobe GL).

At this time, the direction θM of the main beam MB and the direction θG of the grating lobe GL are expressed by the following equation (1).

[0006]

[Equation 1]

Therefore, the grating lobe direction θ
If there is an echo source in G, the grating lobe G
The echo due to L is recognized as due to the main beam MB, and when it is displayed as an image, it becomes a virtual image, which causes erroneous recognition. In order to prevent the generation of the grating lobe GL, it is necessary to make the distance d between the transducers 1 ₁ , 1 ₂ ... 1 _n smaller than the wavelength λ of the ultrasonic wave used. For that purpose, the transducers 1 ₁ , 1 precision machining of cutting the ₂ ... 1 _n is required. Further, when the distance d is reduced, if the number of transducers 1 ₁ , 1 _2, ... 1 _n used for transmission is maintained, the diameter of the probe 1 is reduced and the resolution is lowered.
Transducer 1 that is driven to maintain the diameter of probe 1
_{The number of 1} , 1, ₂ ... 1 _n has to be increased, which causes a problem that the circuit scale is increased.

An object of the present invention is to determine whether the echo is due to the main beam when an ultrasonic beam is emitted toward the inside of the subject or toward the subject surface under the condition that a grating lobe is generated by using the array type probe. It is possible to discriminate whether or not it is due to the grating lobe and prevent erroneous recognition. In addition, the electronic scanning type ultra-high resolution that does not require precision machining of the oscillator or increase the circuit scale by increasing the number of oscillators to drive. An object is to provide a sound wave inspection method and apparatus.

[0009]

The above object is to electronically control the transmission / reception timing of each transducer by using an array type probe in which a plurality of transducers for transmitting / receiving ultrasonic waves are arranged in parallel. In the electronic scanning type ultrasonic inspection method for inspecting the inside or the surface of the subject by focusing or deflecting the ultrasonic beam toward the intended inspection position, it was obtained by each transducer of the array type probe. The signal obtained by delaying the received signal by a desired delay time and then adding it is divided into two or more different frequency bands, and the ultrasonic echo intensity and the echo source are based on the signals in each frequency band. This is achieved by determining the position and determining whether or not there is a shift in the echo source position between frequency bands.

Further, an array probe in which a plurality of transducers for transmitting and receiving ultrasonic waves are arranged side by side is used to electronically control the timing of transmission and reception of each transducer, and an inspection for an ultrasonic beam is conducted. In the electronic scanning ultrasonic inspection apparatus that inspects the inside or the surface of the subject by focusing or deflecting toward the position, the received signal obtained by each transducer of the array type probe is delayed by a desired delay time. Means for dividing the signal obtained by adding after delaying, into two or more frequency bands, and a signal processing circuit for obtaining the crest value and propagation time of the signal in each frequency band sent from this means, The scanning means for scanning the ultrasonic beam by the array type probe on the subject, the crest value and propagation time of the signal in each frequency band from the signal processing circuit, and the array type probe from the scanning means. Location information and Luo and echo intensity for each signal of each frequency band and calculating means for calculating an echo source position is achieved by the calculation result of the calculating means is provided an image display device that displays by each frequency band.

Further, in the above-mentioned electronic scanning type ultrasonic inspection apparatus, the echo source positions for each signal of each frequency band from the calculating means are compared to determine whether or not the echo source position is deviated, and the echo source is not deviated. This is achieved by providing a comparison operation circuit for displaying only the position on the image display device.

[0012]

In the electronic scanning ultrasonic inspection method of the present invention,
Delay times t1 ₁ , t1 given to the individual transducers 1 ₁ , 1 _2, ... 1 _n forming the array type probe to form the main beam
2 ... t1 _n is the difference l1 ₁ in the propagation distance of the individual transducers 1 ₁ , 1 ₂ ... 1 _n with respect to the target deflection direction or focusing position.
It is determined by l1 ₂ ... l1 _n and the sound velocity c inside the subject, and is represented by the equation (2).

[0013]

[Equation 2]

Since the speed of sound c does not depend on the frequency f of the ultrasonic wave, the delay times t1 ₁ , t1 ₂ ... t1 _n do not depend on the frequency f, and the ultrasonic beam is formed in the same direction regardless of the frequency f. On the other hand, the direction in which the grating lobes are formed is determined by the equation (1), but the wavelength λ has a relationship with the frequency f as shown in the equation (3).

[0015]

(Equation 3)

Therefore, if the frequency f of ultrasonic waves is different,
The direction in which the grating lobes are formed also differs. Therefore, the signals obtained by delaying the received signals by the individual transducers 1 ₁ , 1 ₂ ... 1 _n after a desired delay time and adding them are divided into two or more frequency bands, and each frequency is divided into two or more frequency bands. If the echo intensity and the echo source position are obtained based on the crest value and propagation time of the band signal, the echo due to the main beam is at the same position, but the echo due to the grating lobe is misaligned, and it is easy to assume that it is a virtual image. It is possible to make a distinction and prevent erroneous recognition.

Further, in the electronic scanning ultrasonic inspection apparatus of the present invention, the signals obtained by delaying the reception signals obtained by the transducers of the array type probe by a desired delay time and then adding the signals are added. The signal processing circuit obtains the peak value and the propagation time of the signal of each frequency band sent from the means for dividing into two or more frequency bands. The scanning means scans the ultrasonic beam by the array type probe on the subject, and the calculating means calculates the peak value and propagation time of the signal of each frequency band from the signal processing circuit and the array type probe from the scanning means. The echo intensity and echo source position for each signal in each frequency band are calculated from the position information. The calculated echo source position is displayed on the image display device for each frequency band, so that they can be visually compared and compared, and whether the echo is due to the grating lobe or the main beam can be easily determined based on the presence or absence of the deviation of the echo source position. It is possible to discriminate and prevent erroneous recognition.
There is no need for precision machining of the oscillator or increase in the circuit scale due to increasing the number of oscillators to be driven.

Further, in the electronic scanning ultrasonic inspection apparatus, the comparison operation circuit compares the echo source positions for each signal of each frequency band from the operation means to determine whether or not the echo source position is displaced, and Only the echo source position that did not exist is displayed on the image display device. That is, instead of displaying the echo source position on the image display device for each frequency band, the echo source positions calculated in each frequency band are compared, and the echo source position without displacement of the echo source position, that is, the echo source by the main beam Only the image is displayed on the image display device, and the echo source due to the grating lobe is removed. Therefore, erroneous recognition is surely prevented, and moreover, there is no need for precision machining of the vibrator and an increase in the circuit scale due to the increase in the number of driven vibrators.

[0019]

Embodiments of the present invention will be described below with reference to the drawings. FIG. 1 is a diagram for explaining the principle of the electronic scanning ultrasonic inspection method according to the present invention, and shows an example of a simulation result of the method according to the present invention. FIG. 1A is a diagram simulating the vibration pulse waveform of each transducer driven in the array type probe, in which the horizontal axis represents time and the vertical axis represents amplitude. This pulse waveform is shifted by the delay time difference, the directivities of the transducers are multiplied, the contributions from the transducers are added, and the maximum amplitude is obtained. Then, the ultrasonic wave intensity as shown in FIG. The distribution is obtained. Here, the horizontal axis represents the position in the array direction of the transducers of the array type probe, and the vertical axis represents the ultrasonic wave intensity. The peak of the right side waveform which is the waveform of the main beam MB and the waveform of the grating lobe GL. It is possible to reproduce the peak of the left side waveform which is Figure 1 (c),
(D) shows the real part 41A and the imaginary part 41B of the waveform formed by adding the contributions from the respective oscillators and subjected to the Fourier transform. The horizontal axis represents frequency and the vertical axis represents amplitude, and f0 represents the center frequency of the pulse waveform of FIG. 1 (a). In this example, FIG. 1C shows the Fourier transform of the waveform of the main beam position, and FIG. 1D shows the Fourier transform of the position of the grating lobe GL. FIG.
(E) is a waveform obtained by filtering the waveforms shown in FIGS. 1 (c) and (d) in the frequency region shown by the A and B filters,
It is the intensity distribution of the ultrasonic wave obtained from the maximum amplitude of the waveform obtained by applying the inverse Fourier transform, and each axis is the same as in FIG. 1 (b). From FIG. 1E, the peak position does not change after passing through the A and B filters having different pass frequency bands in the main beam MB, whereas the grating lobe G
It can be seen that the peak position changes in L.

Therefore, the received signals of the transducers of the array type probe are delayed and added, and then separated into different frequency bands, the echo intensity and the echo source position are obtained for each frequency band, and the echo between each frequency band is obtained. By comparing the source positions and determining whether or not the echo source position is displaced, it is possible to easily recognize whether the echo is due to the main beam MB or the grating lobe GL, that is, the grating lobe GL.
The virtual image due to can be discriminated.

FIG. 2 is a block diagram showing an embodiment of an apparatus (electronic scanning ultrasonic inspection apparatus according to the present invention) to which the electronic scanning ultrasonic inspection method according to the present invention based on such a principle is applied. . In FIG. 2, reference numeral 1 is an array type probe, and as shown in FIG. 6, a large number (n) of strip-shaped ultrasonic transducers 1 ₁ , 1 ₂ ... 1 _n are arranged in an array at equal intervals d. It has a configuration arranged in. Then, the oscillators 1 ₁ , 1 ₂ ...
Each of the 1 _n electrodes is led out by a signal line and is divided into two parts, one for the ultrasonic wave transmitting side circuit and the other for the ultrasonic wave receiving side circuit. In the circuit on the ultrasonic wave transmission side, the signal lines from the transducers 1 ₁ , 1 _2, ... 1 _n are connected to a transmission drive circuit 24 having n transmission drive units corresponding to the signal lines. Then, in the desired inspection direction or focusing position, the transducers 1 ₁ , 1 _2, ... 1
_The transmission delay control circuit 21 controls the timing of the trigger signals for driving the individual transducers 1 ₁ , 1 _2, ... 1 _n so that the phases of the ultrasonic waves emitted from _n are aligned to obtain a desired delay time. Has been done. Further, in the circuit on the ultrasonic wave receiving side, the signal lines from the respective transducers 1 ₁ , 1 ₂ ... 1 _n are connected to an amplifier 23 having n corresponding amplifying sections, and each of which is an analog signal. Received signals from the oscillators 1 ₁ , 1 _2, ... 1 _n are amplified by an amplifier 23, respectively. After that, by the reception delay circuit 22 controlled by the reception delay control circuit 27, for example, a delay line with a tap, the analog delay is performed for a desired delay time to perform reception focus, and then the n reception signals subjected to the reception focus are added. The signal is added by the device 25 to obtain one signal.
Then, the one received signal is divided into a and b sides, and A and B filters 31a and 31 having different pass frequency bands are provided.
b through the signal processing circuits 26a and 26b.
It is configured such that the peak value and the propagation time are measured separately, and the result (measured value) is held in the memory 28. Further, a scanner 30 is attached to the array type probe 1 so that an object (not shown) can be scanned with an ultrasonic beam, and the array type probe 1 at the time of transmitting and receiving the ultrasonic beam is also provided. The position information of the (scanner 30) is held in the memory 28.

With such a configuration, after scanning the subject, the position information of the array type probe 1 held in the memory 28 and the peak value and propagation of each output signal of the A and B filters 31a and 31b are propagated. The echo intensity and the echo source position are obtained from the time, and the echo source position is determined by the image display device 2.
9 is displayed, and both of them can be visually compared. The echo intensity and the echo source position are, for example, an arithmetic circuit (not shown) provided between the memory 28 and the image display device 29.
Required by.

FIG. 3 is a diagram showing a display example of the echo source position by the image display device 29. In this example, the A scope is used for display, but as shown in the figure, the echo source positions due to the output signals of the A and B filters 31a and 31b having different frequency bands are displayed in the upper and lower parts of the screen for each filter (frequency band). As a result, the real image 61A due to the main beam MB has no deviation in the echo source position, and the virtual image 61B due to the grating lobe GL has the position deviation.
It can be easily determined that Further, even under the condition that the grating lobe GL is generated, that is, even when the distance d between the transducers 1 ₁ , 1 _2, ... 1 _n forming the array type probe 1 is longer than the wavelength λ of the ultrasonic wave, the grating lobe. Since the virtual image 61B by GL can be recognized,
Vibrator 1 _1, 1 ₂ ... without requiring precision machining of 1 _n, also the transducer 1 ₁ is driven, 1 ₂ ... 1 _n increase in circuit scale because there is no need to increase the number of even be minimized It will be possible.

FIG. 4 is a block diagram showing a main part of another embodiment of the electronic scanning ultrasonic inspection apparatus according to the present invention. As can be seen from the figure, the signals divided into different frequency bands by the A and B filters 31a and 31b are processed by the signal processing circuits 26a and 26a.
The peak value and the propagation time are measured and held in the memory 28, and the position information of the array type probe 1 (scanner 30) is held in the memory 28 for each frequency band. The process until the calculation of the echo intensity and the echo source position is the same as that of the embodiment shown in FIG. In this example, after that, the comparison arithmetic circuit 32 determines whether or not the echo source position is deviated, and only the echo source position deviated is displayed on the image display device 29. Only the real image 61A (see FIG. 3) by the MB is displayed on the image display device 29.

In the above embodiment, the scanning of the subject is mechanically performed by the scanner 30, but a large number of transducers n or more to be actually driven are arranged in parallel to drive one transducer group. It may be performed by electronic scanning in which the elements are shifted.
In the above-described embodiment, the received signals obtained by the transducers 1 ₁ , 1 _2, ... 1 _n which are the constituent elements of the array type probe 1 are delayed by a desired delay time and then added. Signal 2
Or more means to be divided into frequency bands, the amplifier 23, reception delay circuits 22, an adder 25, and A, B filters 31a, was constructed in 31b, each transducer ₁ 1, 1 ₂
The received signal waveform obtained at 1 _n is subjected to A / D conversion for each transducer before and after the amplifier 23, or an adder 25
After the A / D conversion is performed on the waveform of the signal added in, the digital value is held in the memory 28, and the received signal is changed by performing the arithmetic processing described in the simulation of the electronic scanning ultrasonic inspection method of the present invention. The frequency band may be divided into different frequency bands.

[0026]

As described above, according to the electronic scanning ultrasonic inspection method of the present invention, the received signals of the array type probe are delayed and added, and then divided into two or more different frequency bands. Then, the echo intensity and echo source position of the ultrasonic wave are obtained based on the signals in each frequency band, and it is determined whether or not there is a shift in the echo source position between each frequency band, making it easy to create a virtual image due to the grating lobe and a real image due to the main beam. There is an effect that it can be distinguished.

Further, according to the electronic scanning ultrasonic inspection apparatus of the present invention, the received signals obtained by the transducers of the array type probe are delayed by a desired delay time and then added. A means for dividing the signal into two or more frequency bands, a signal processing circuit for obtaining the peak value and the propagation time of the signal in each frequency band sent from this means, and an ultrasonic beam by an array type probe Echo intensity for each signal in each frequency band based on the scanning means for scanning on the subject, the crest value and propagation time of the signal in each frequency band from the signal processing circuit, and the position information of the arrayed probe from the scanning means. And an image display device for displaying the calculation result of this calculation means for each frequency band, or further, comparing the echo source position for each signal of each frequency band from the calculation means. Shi Since a comparison operation circuit that determines whether or not the echo source position is displaced and displays only the echo source position that has not been displaced on the image display device is provided, the virtual image due to the grating lobe and the real image due to the main beam can be easily discriminated. , Even if the distance between the transducers that make up the array-type probe is longer than the wavelength of ultrasonic waves, virtual images due to the grating lobes can be recognized, false recognition is reliably prevented, and precise processing of the transducers is not required There is an effect that the increase of the can be minimized.

[Brief description of drawings]

FIG. 1 is a diagram illustrating the principle of the method of the present invention.

FIG. 2 is a block diagram showing an embodiment of an apparatus (invention apparatus) to which the method of the present invention is applied.

FIG. 3 is a diagram showing a display example of an echo source position by the image display device of the device of the present invention shown in FIG.

FIG. 4 is a block diagram showing a main part of another embodiment of the device of the present invention.

FIG. 5 is a block diagram of a conventional device.

FIG. 6 is an explanatory diagram of an array type probe.

FIG. 7 is an explanatory diagram of grating lobe generation.

[Explanation of symbols]

1 ... Array type probe, 1 ₁ , 1 ₂ ... 1 _n ... Ultrasonic transducer,
21 ... Transmission delay control circuit, 22 ... Reception delay circuit, 23 ... Amplifier, 24 ... Transmission drive circuit, 25 ... Adder, 26, 26a, 26b ... Signal processing circuit, 28 ... Memory, 29 ... Image display device, 30 ... Scanner, 31a ... A
Filter, 31b ... B filter, 32 comparison operation circuit, 4
1a ... Real part, 41b ... Imaginary part, 61a ... Real image, 61b ... Virtual image, MB ... Main beam, GL ... Grating lobe.

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Yoshinori Takesume, inventor Yoshinori Takesumi 7-1, 1-1 Omika-cho, Hitachi-shi, Ibaraki Hitachi Research Laboratory, Hitachi Ltd. (72) Inventor Yoshihiro Michiguchi 7-chome, Omika-cho, Hitachi, Ibaraki No. 1 stock company Hitachi Ltd. Hitachi Research Laboratory

Claims (3)

[Claims] 1. An inspection targeting an ultrasonic beam by electronically controlling the transmission / reception timing of each transducer using an array type probe in which a plurality of transducers for transmitting / receiving ultrasonic waves are arranged in parallel. In the electronic scanning ultrasonic inspection method for inspecting the inside or the surface of the subject by focusing or deflecting toward the position, the received signal obtained by each transducer of the array type probe is delayed by a desired delay time. The signal obtained by adding after delaying is divided into two or more different frequency bands, the echo intensity of the ultrasonic wave and the echo source position are obtained based on the signal of each frequency band, An electronic scanning ultrasonic inspection method, characterized in that the presence or absence of deviation of the echo source position is determined. 2. An inspection targeting an ultrasonic beam by electronically controlling the transmission / reception timing of each transducer using an array type probe in which a plurality of transducers for transmitting / receiving ultrasonic waves are arranged in parallel. In the electronic scanning ultrasonic inspection apparatus that inspects the inside or the surface of the subject by focusing or deflecting toward the position, the received signal obtained by each transducer of the array type probe is delayed by a desired delay time. Means for dividing the signal obtained by adding after delaying into two or more frequency bands;
A signal processing circuit for obtaining a peak value and a propagation time of a signal in each frequency band sent from this means, a scanning means for scanning an ultrasonic beam by the array type probe on a subject, and the signal processing circuit. Calculating means for calculating the echo intensity and the echo source position for each signal of each frequency band from the crest value and propagation time of the signal of each frequency band from and the position information of the array type probe from the scanning means, An electronic scanning ultrasonic inspection apparatus comprising: an image display device for displaying the calculation result of the calculation means for each frequency band. 3. An echo source position for each signal of each frequency band from the arithmetic means is compared to determine whether or not the echo source position is displaced, and only the echo source position which is not displaced is displayed on the image display device. The electronic scanning ultrasonic inspection apparatus according to claim 2, further comprising a comparison operation circuit for performing the operation.