JP5195076B2 - Ultrasonic measuring device and ultrasonic measuring method - Google Patents

Description

  The present invention transmits an ultrasonic wave to an object to be inspected, and obtains a signal transmitted through the object to be inspected or reflected by the object to be inspected with a good S / N (signal-to-noise ratio) and ultrasonic measurement Regarding the method.

  Ultrasonic measurement is used to detect defects inside steel products (bars, plates, pipes, etc.) and to measure wall thickness. In these ultrasonic measurement methods, a drop in S / N due to flying electric noise, water adhering to a material when water is used for acoustic coupling, or echoes from bubbles in a local water immersion part becomes a bottleneck.

  Although measures such as strengthening the shield ground of the signal line and stabilizing the water coupling are indispensable, synchronous addition averaging is widely used to further reduce noise by signal processing.

The synchronous addition averaging process utilizes the fact that ultrasonic waves are repeatedly transmitted and received. In the signal that is repeatedly received, the phase of the signal is the same in the reflected echo signal from the same reflector or the transmitted signal of the subject with the same propagation path, but the phase of the noise component is not.
Therefore, when the acquired signals are averaged, the noise whose phase is not aligned is canceled, and only the reflected echo from the same reflector and the transmitted signal that has passed through the subject remain, and the S / N is improved. become. For noise mixed in pulses, the S / N is improved by 20 log (1 / N) dB with respect to the average number N of additions, and for log noise, 20 log (1 / √N) dB. It is known that the S / N improvement is expected (see, for example, Patent Document 1 and Patent Document 2).
JP-A-2-209136 JP 2000-153847 A

  However, if the synchronous signal used when acquiring the ultrasonic signal fluctuates due to jitter, or if the ultrasonic reflection source is moving, if the synchronous addition averaging process is performed, the reflected echo from the subject The transmitted wave signal of the subject is reduced and the S / N is reduced, or the reflected echo and the transmitted wave signal of the subject are canceled and disappear.

  For example, as shown in FIG. 7, a case in which a defect in a steel pipe base material is detected by a reflection method while rotating a steel pipe in the circumferential direction or scanning an ultrasonic probe in the circumferential direction is given as an example. . As the defect moves in the ultrasonic beam, the propagation path of each defect reflection echo changes. Each time a defect echo is acquired, the phase of the reflected signal from the heel shifts, and even if the synchronous addition averaging is performed as it is, the S / N improvement effect that is the effect of the original synchronous addition cannot be obtained. / N will decrease.

  If the depth from the defect can be known, it is possible to calculate the amount of phase shift geometrically, align the phase with the calculated amount of shift, and perform synchronous addition averaging processing, but in this case, Since there are a plurality of depth positions that can be estimated from the propagation time of the defect echo, it is difficult.

  The present invention solves the above-described problems. Even when a change in the beam path of the subject or a deviation in propagation time due to jitter when acquiring an ultrasonic signal occurs, the S / N It is an object of the present invention to provide an ultrasonic measurement apparatus and an ultrasonic measurement method that measure ultrasonic waves well.

The present invention for solving the above problems, receives a reception signal outputted from the ultrasonic transmitting and receiving unit for receiving ultrasonic waves transmitted through the reflective or the subject from the subject repeatedly transmits ultrasonic pulses to a subject In the ultrasonic measurement apparatus that processes each time, a time difference extraction unit that obtains a time difference of a propagation time of a reflected wave or a transmitted wave with respect to a reference signal of the received signal, and a phase of the reflected wave or the transmitted wave of the received signal based on the time difference A phase correction unit that corrects the phase of the received signal so as to match the phase of the reflected wave or transmitted wave of the reference signal, and an addition signal obtained by synchronously adding the received signal whose phase has been corrected in the past a predetermined number includes a sum signal generating unit that includes a memory unit for storing the generated the addition signal, wherein the reference signal is an ultrasonic measuring apparatus which is a sum signal stored in the memory unit

  In the ultrasonic measurement apparatus according to the invention described above, the time difference may be a time difference between a maximum value of the reception signal and a maximum value of the reference signal, or a minimum value of the reception signal and the reference signal. Is the time difference of the minimum value of.

  In the ultrasonic measuring apparatus according to the present invention as described above, the time difference is obtained from a cross-correlation calculation between the received signal and the reference signal.

Further, the present invention provides an ultrasonic wave for processing a reception signal output from an ultrasonic transmission / reception unit that repeatedly transmits an ultrasonic pulse to a subject and receives an ultrasonic wave reflected from the subject or transmitted through the subject for each reception. In the measurement method, a time difference extraction step for obtaining a time difference in propagation time of the reflected wave or transmitted wave with respect to the reference signal of the received signal, and a phase of the reflected wave or transmitted wave of the received signal based on the time difference reflects the reference signal. A phase correction step for correcting the phase of the reception signal so as to match the phase of the wave or transmitted wave, and an addition signal generation step for generating an addition signal obtained by synchronously adding the reception signal whose phase is corrected in the past a predetermined number of times , comprising a memory storing the generated the sum signal, wherein the reference signal is an ultrasonic measurement is stored addition signal in said memory step It is the law.

  According to the present invention, even when there is a change in the beam path of a subject or a deviation in propagation time due to jitter when acquiring an ultrasonic signal, ultrasonic measurement that measures ultrasonic waves with good S / N. An apparatus and an ultrasonic measurement method can be provided.

[First embodiment]
FIG. 1 is a diagram showing a configuration of an ultrasonic measurement apparatus according to the first embodiment of the present invention.
The ultrasonic measurement device includes a phase time correction unit 1, an adder 2, a memory Ma 3, a subtracter 4, a memory Mb 5, a divider 6, an information processing device 7, an output device 8, and a recording device 9.

  The phase time correction unit 1 extracts the time difference of the propagation time of the reflected echo between the input ultrasonic signal (for example, the digital signal after A / D conversion processing) and the reference signal, and the time difference The time (phase) of the input ultrasonic signal is corrected so that the phase timing of the reflected echo of the input signal matches the phase timing of the reflected echo of the reference signal. The adder 2 adds the corrected ultrasonic signal to the signal in the memory Mb5, and generates a synchronous addition ultrasonic signal obtained by synchronous addition. The memory Ma3 stores the corrected ultrasonic signal individually. The subtracter 4 subtracts the earliest ultrasonic signal among the ultrasonic signals input to add in the past from the synchronous addition ultrasonic signal generated by the adder 2.

  The memory Mb5 stores the synchronous addition ultrasonic signal generated by the adder 2. The divider 6 divides and averages the synchronously added ultrasonic signals by the number k (cumulative number) of the synchronously added ultrasonic signals. The information processing device 7 performs material property evaluation (e.g., presence / absence of defect, shape, state of internal tissue) using the averaged synchronous addition ultrasonic signal, and outputs it to the output device 8. The recording device 9 records the information processing result.

  In the present specification, a reflected wave will be described as an example, but it goes without saying that a transmitted wave can be similarly processed.

Subsequently, the operation of the ultrasonic measurement apparatus will be described.
An ultrasonic signal that is repeatedly transmitted and received by an ultrasonic transmission / reception means (not shown) is converted into a digital value by an A / D converter (not shown). In the following description, the ultrasonic signal is treated as a digital signal. Note that the ultrasonic transmission / reception means may be a method using a piezoelectric vibrator, an electromagnetic ultrasonic method, a laser ultrasonic method, or a method combining the electromagnetic ultrasonic method and the laser ultrasonic method. Any method that transmits and receives sound waves may be used.

  In the initial state (or reset state) of the ultrasonic measurement apparatus, no data is stored in the memory Ma3 and the memory Mb5. Alternatively, the data in the memory is erased immediately before the measurement is started. Therefore, the ultrasonic signal b1 transmitted first is not processed by the phase time correction unit 1 but is stored in the memory Ma3 as it is.

The memory Ma3 is a storage unit that can store a plurality (d) of ultrasonic signals. Here, if the number of ultrasonic signals to be synchronously added is k (preset), the memory Ma3 has a storage area that can store at least k + 1 signals. That is, the signal storage number d ≧ k + 1. The memory Ma3 can record an ultrasonic signal by designating an address or read it out. Hereinafter, the addresses are expressed as W (1), W (2)... W (k + 1)... W (d).
In the memory Ma3, the storage area is used cyclically. For example, when an ultrasonic signal is stored at the final address W (d), the next ultrasonic signal is stored at the address W (1).

The ultrasonic signal b1 that has passed through the phase time correction unit 1 is input to the adder 2 in parallel with the write operation to the memory Ma3 described above. Here, since no ultrasonic signal is stored in the memory Mb5, the ultrasonic signal b1 is sent to the subtracter 4 without being processed in the adder 2. However, since no data is stored in the memory Ma3 and the memory Mb5, the ultrasonic signal b1 is not processed by the subtractor 4 and is input to the memory Mb5.
The memory Mb5 stores the inputted ultrasonic signal b1. In the present embodiment, an example in which the ultrasonic signal stored in the memory Mb5 is used as a reference signal in the subsequent signal processing will be described below.

Next, the operation of the ultrasonic signal b2 sent second will be described.
The second signal b2 is sent to the accumulated signal (= signal b1) which is the reference signal stored in the memory Mb5 to obtain the difference in propagation time of the reflected echo, and the reflected echo of the signal b2 and the reference signal A correction amount θ for calculating the timing of the reflected echo of the signal b1 is calculated. Then, a new signal obtained by shifting the time axis of the signal b2 by the correction amount θ is obtained.

FIG. 2 is a flowchart showing a procedure for correcting a signal in the phase time correction unit 1.
In step S01, an accumulated signal that is a reference signal stored in the memory Mb5 is read. In step S02, a propagation time t1 when the accumulated signal becomes maximum is obtained. In step S03, the input ultrasonic signal is read, and it is checked whether the maximum value of the signal is equal to or greater than a predetermined value.

  In the case of No in step S03, that is, when the maximum value of the input ultrasonic signal is smaller than the predetermined value, the correction amount θ is not calculated. This is because when the maximum value is less than or equal to the predetermined value, no reflection echo (scratch signal) is included, so that it is determined that the synchronous addition processing is unnecessary. In step S04, the input ultrasonic signal is directly used as a new ultrasonic signal, and the new ultrasonic signal is output from the phase time correction unit 1 in step S07.

If Yes in step S03, that is, if the maximum value of the ultrasonic signal is greater than or equal to a predetermined value, the correction amount θ is calculated. Therefore, in step S05, the propagation time t2 when the ultrasonic signal is maximized is obtained.
FIG. 3 is a diagram showing the propagation time for giving the maximum value of the accumulated signal and the ultrasonic signal. Since the time difference is t2−t1, it can be obtained as a correction amount θ = t1−t2.
In step S06, a new ultrasonic signal is generated by shifting the time axis by the correction amount θ minutes so that the propagation time giving the maximum value of the ultrasonic signal becomes t1, and in step S07, the new ultrasonic signal is phase-converted. Output from the time correction unit 1. Note that data whose propagation time is negative due to the shift is deleted and is not used in the subsequent processing.

  The new ultrasonic signal whose phase has been corrected in this way is stored at address W (2) (second address) of the memory Ma3. In parallel with this operation, a new ultrasonic signal is sent to the adder 2 and synchronously added to the accumulated signal (= b1) stored in the memory Mb5. At this time, since both signals are maximum at the same time, the maximum value is further emphasized by this synchronous addition.

  In the subtracter 4, the ultrasonic signal stored at the address W (2-k) of the memory Ma3 is subtracted from the synchronously added signal. However, when k is 2 or more, the past ultrasonic signal is not recorded in the memory Ma3. Therefore, no subtraction is performed, and the synchronously added signal passes through the subtracter 4 and is stored in the memory Mb5. The synchronously added ultrasonic signal stored in the memory Mb5 becomes a reference signal in the subsequent signal processing.

Thereafter, this operation is continuously repeated until the operation is reset.
Next, the operation for processing the nth ultrasonic signal bn will be described.
The correction amount θ of the reflection echo propagation time is calculated between the n-th signal bn and the accumulated signal of the past k ultrasonic signals stored in the memory Mb. Then, a new ultrasonic signal obtained by shifting the time axis of the signal bn by the correction amount θ is obtained.

  The new ultrasonic signal is stored at an address W (n) (nth address) of the memory Ma3. When the ultrasonic signal is stored in all the addresses of the memory Ma3, it returns to the top address of the memory Ma again and is sequentially written.

  The new ultrasonic signal is sent to the adder 2 and is synchronously added to the accumulated signal stored in the memory Mb5. At this time, since both signals are maximum at the same time, the maximum value is further emphasized by this addition.

  Subsequently, the synchronously added signal is input to the subtractor 3. The subtractor 3 passes the n-th signal sent as it is without processing while satisfying n ≦ k. When n> k, the signal stored in the memory Mb is subtracted from the synchronously added signal. The signal used for the subtraction is a signal recorded at the address W (n−k) of the memory Ma. In other words, the signal that has passed through the subtracter 4 is a signal obtained by synchronously adding k latest ultrasonic signals in the past.

Note that when n> d, that is, the signal storage to each address of the memory Ma3 is completed, and after the second order, the subtracter reads and subtracts the address W (d−k + c) of the memory Ma3 from the signal bn. Perform processing. c is calculated by c = n mod d (remainder of n by d).
The signal that has passed through the subtracter 4 is sent to the memory Mb5 and the divider 6. The divider 6 divides and averages the signal by the number of averaging times k. Based on the averaged signal, it is converted into a chart image, a C scope image, a B scope image, etc. by the information processing device 7, and the material evaluation characteristics (defect existence / shape determination, internal structure evaluation, etc.) of the object to be inspected are obtained. The result is stored in the recording device 9 together with the result and output to the output device 8 such as a printer or a display.

  Although the correction amount θ is obtained from the time (= t1−t2) for giving the maximum value in the signal, it may be obtained from the time (= z1−z2) for giving the minimum value in the signal shown in FIG.

[Second Embodiment]
In the second embodiment, the method for obtaining the correction amount θ is different from that in the first embodiment. Accordingly, the same parts as those in the first embodiment are denoted by the same reference numerals, and detailed description thereof is omitted.

FIG. 4 is a flowchart showing a procedure for correcting a signal in the phase time correction unit 1.
In step S11, the accumulated signal stored in the memory Mb5 and the addition average number k are read. In step S12, a new accumulated signal is generated by dividing the accumulated signal by the addition average number k.

Next, in step S13, the inputted ultrasonic signal is read, and it is checked whether or not the maximum value of the signal is equal to or greater than a predetermined value.
If No in step S13, that is, if the maximum value of the input ultrasonic signal is smaller than the predetermined value, the correction amount θ is not calculated. In step S14, the input ultrasonic signal is directly used as a new ultrasonic signal, and in step S18, the new ultrasonic signal is output from the phase time correction unit 1.

  If Yes in step S13, that is, if the maximum value of the ultrasonic signal is greater than or equal to a predetermined value, a process for calculating the correction amount θ is executed. Therefore, in step S15, a cross-correlation function between the new accumulated signal and the input ultrasonic signal is calculated.

In step S16, a time τ that gives the maximum value of the cross-correlation function is obtained.
FIG. 5 is a diagram illustrating time τ for giving the maximum value of the cross-correlation function.
The correction amount θ can be obtained as τ.
When obtaining the time τ, the shape near the maximum value may be applied to a known curve, and the time τ giving the maximum value may be analytically obtained based on the curve.

  In step S17, a new ultrasonic signal is generated by shifting the time axis by the correction amount θ = −τ so that the timing for giving the maximum value of the ultrasonic signal coincides with the accumulated signal. In step S18, this new ultrasonic signal is generated. A sound wave signal is output from the phase time correction unit 1.

[effect]
FIG. 6 is a diagram illustrating an example of measurement performed by applying the ultrasonic measurement apparatus. The waveform (left side) measured while moving the ultrasonic probe with respect to the eyelid sample and the waveform (right side) subjected to synchronous addition averaging processing are shown. Note that the ultrasonic measurement device is reset at appropriate time intervals. As a result of the measurement by this apparatus, it can be seen that noise with out-of-phase is canceled and S / N is improved.

From the above results, this ultrasonic measuring device is applied to the case where flaws in the steel pipe base material are detected while rotating the steel pipe in the circumferential direction as shown in FIG. 7 or scanning the ultrasonic probe in the circumferential direction. It is possible to do.
As the eyelid moves in the ultrasonic beam, the propagation path of each defect echo changes. As a result, the phase of the reflected signal from the heel shifts for each defect echo income, and the S / N decreases if the synchronous addition averaging is performed as it is in the past.
However, according to the ultrasonic measurement apparatus according to the embodiment of the present invention, the resetting is performed at an appropriate time interval, and in one measurement period, the phase is synchronized and the addition process is performed, thereby moving the object to be inspected. On the other hand, synchronous addition can be executed without causing a decrease in S / N.

  In the first and second embodiments, the reference signal is the accumulated signal, but it may be a preset waveform instead of the accumulated signal, and a reflected echo or transmitted wave is first detected. The signal waveform may be a waveform obtained in the middle.

  Each function described in the above embodiment may be configured using hardware, or may be realized by reading a program describing each function into a computer using software. Each function may be configured by appropriately selecting either software or hardware.

  Furthermore, each function can be realized by causing a computer to read a program stored in a recording medium (not shown). Here, as long as the recording medium in the present embodiment can record a program and can be read by a computer, the recording format may be any form.

  Note that the present invention is not limited to the above-described embodiment as it is, and can be embodied by modifying the constituent elements without departing from the scope of the invention in the implementation stage. Further, various inventions can be formed by appropriately combining a plurality of constituent elements disclosed in the embodiment. For example, some components may be deleted from all the components shown in the embodiment. Furthermore, you may combine suitably the component covering different embodiment.

The figure which shows the structure of the ultrasonic measuring device which concerns on the 1st Embodiment of this invention. The flowchart which shows the procedure which correct | amends a signal in a phase time correction | amendment part. The figure which shows the time which gives the maximum value of a cumulative signal and an ultrasonic signal. The flowchart which shows the procedure which correct | amends a signal in a phase time correction | amendment part. The figure which illustrates the time which gives the maximum value of a cross correlation function. The figure which shows the example measured by applying this ultrasonic measuring device. The figure which shows the case which flaws the flaw in a steel pipe base material, rotating a steel pipe in the circumferential direction or scanning an ultrasonic probe in the circumferential direction.

Explanation of symbols

    DESCRIPTION OF SYMBOLS 1 ... Phase time correction part, 2 ... Adder, 3 ... Memory Ma, 4 ... Subtractor, 5 ... Memory Mb, 6 ... Divider, 7 ... Information processing device, 8 ... Output device, 9 ... Recording device, t1 ... Time, t2 ... time, τ ... time.

Claims (4)

In an ultrasonic measurement device that processes a reception signal output from an ultrasonic transmission / reception unit that repeatedly transmits ultrasonic pulses to a subject and receives ultrasonic waves reflected from the subject or transmitted through the subject, for each reception ,
A time difference extraction unit for obtaining a time difference of a propagation time of a reflected wave or a transmitted wave with respect to a reference signal of the received signal;
A phase correction unit that corrects the phase of the received signal so that the phase of the reflected wave or transmitted wave of the received signal matches the phase of the reflected wave or transmitted wave of the reference signal based on the time difference ;
A sum signal generator for generating a sum signal whose phase is obtained by adding a predetermined past number synchronize a corrected received signal,
A memory unit for storing the generated addition signal,
The ultrasonic measurement apparatus , wherein the reference signal is an addition signal stored in the memory unit .   The time difference is a time difference between a maximum value of the received signal and a maximum value of the reference signal, or a time difference between a minimum value of the received signal and a minimum value of the reference signal. 1. The ultrasonic measurement apparatus according to 1.   The ultrasonic measurement apparatus according to claim 1, wherein the time difference is obtained from a cross-correlation calculation between the received signal and the reference signal. In an ultrasonic measurement method for processing a reception signal output from an ultrasonic transmission / reception unit that repeatedly transmits ultrasonic pulses to a subject and receives ultrasonic waves reflected from the subject or transmitted through the subject, for each reception ,
A time difference extraction step for obtaining a time difference of a propagation time of a reflected wave or a transmitted wave with respect to a reference signal of the received signal;
A phase correction step for correcting the phase of the received signal so that the phase of the reflected wave or transmitted wave of the received signal matches the phase of the reflected wave or transmitted wave of the reference signal based on the time difference;
An addition signal generation step of generating an addition signal obtained by synchronously adding a predetermined number of past received signals whose phases have been corrected; and
A memory step for storing the generated sum signal,
The ultrasonic measurement method , wherein the reference signal is an addition signal stored in the memory step .

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