JPH06242090A - Electronic scanning ultrasonic inspection method and equipment therefor - Google Patents

Abstract

PURPOSE:To provide an electronic scanning ultrasonic inspection equipment in which a microdefect can be detected even when the number of driving elements is constant by reducing the diameter of ultrasonic beam at a focal point. CONSTITUTION:An ideal delay time generator 10 determines a delay time corresponding to the difference of propagation distance from each element to a focal point based on input values, e.g. frequency and a target focal point F, and sets the delay times for transmitting and receiving delay time circuits 11, 12. A calculator 8 determines a focal position F0 where the diameter of ultrasonic beam increases. A comparator 6 compares the focal point F0 with an input value F and transmits/receives ultrasonic wave with an ideal delay time set for the circuits 11, 12 if F>=F0. If F<F0, ultrasonic wave is tranmitted/ received with the ideal delay time added with a correction delay time. This constitution allows reduction of ultrasonic beam diameter at focal point even when the focal point of ultrasonic wave is altered in the inspection while fixing the number of driving elements in an array probe 1.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method and apparatus for controlling the transmission timing of ultrasonic waves transmitted from each element of an array probe to focus the ultrasonic waves on a target position and inspect the same, and more particularly to The present invention relates to an electronic scanning ultrasonic inspection method and apparatus suitable for forming a small ultrasonic beam diameter at a focus position (focus position).

[0002]

2. Description of the Related Art FIG. 9 is a block diagram of a conventional electronic scanning ultrasonic inspection apparatus. It is an array probe 1 composed of a plurality of small elements, and an element to be driven among the elements of the array probe 1. And a switching device 3 for selecting and an ultrasonic transmitter / receiver 4 for driving each element forming the array probe 1 to transmit / receive ultrasonic waves.
And a transmission delay time circuit 11 that gives each element a timing of transmitting ultrasonic waves from (each element of) the array probe 1 and the ultrasonic waves received by (each element of) the array probe 1 are combined and added. And a reception delay time circuit 12.

In this conventional device, the timing of transmitting ultrasonic waves from (each element of) the array probe 1 is controlled to focus the ultrasonic waves on a target position in the subject 2, and the array probe 1 is also used. The respective reception times of the ultrasonic waves received by (each element of) are adjusted and added. The transmission timing and the reception time are controlled by the delay times set in the transmission / reception delay time circuits 4 and 5.

In this conventional apparatus, in order to change the focus position of ultrasonic waves and reduce the ultrasonic beam diameter at the focus position, the number of elements to be driven is changed in accordance with the target focus position to drive. The delay time given to each element is changed. However, this method has a problem that the switch 3 becomes large in order to change the number of driving elements. Therefore, there is also a method of changing the focusing position by changing the delay time given to each element while keeping the number of driving elements constant.

As a device related to the electronic scanning type ultrasonic inspection apparatus, for example, a medical ultrasonic device handbook edited by Japan Electronic Machinery Manufacturers Association (published April 20, 1985)
There is.

[0006]

As described above, when the number of driving elements is fixed and only the delay time is changed, there is a problem that some elements do not contribute to the focusing of ultrasonic waves depending on the focusing position. However, conventionally, the influence of the existence of such an element has not been taken into consideration. The inventors calculated the interference of the ultrasonic waves transmitted from each element on the assumption that there is an element that does not contribute to the focusing of the ultrasonic waves, and found that the ultrasonic beam diameter may increase depending on the focusing position. did. If the diameter of the ultrasonic beam at the focus position becomes large, it becomes impossible to detect minute defects, which is a problem.

An object of the present invention is to detect minute defects by reducing the ultrasonic beam diameter at the focusing position even when the number of driving elements is fixed and only the delay time is changed to change the focus position. An object is to provide an electronic scanning ultrasonic inspection method and its apparatus.

[0008]

The above-mentioned object is to reduce the ultrasonic beam diameter when each element of the array probe is provided with an ideal delay time necessary for focusing the ultrasonic wave at a desired position. The focus position that becomes larger (hereinafter referred to as the determination focus position) is obtained and stored in advance, and the distance from the array probe to the target focus position and the distance to the determination focus position are compared to determine the target focus position. This is achieved by adding a delay time for correction to the ideal delay time when the distance to is smaller than the distance to the determination focus position.

[0009]

The target focus position and the determination focus position are compared based on the array probe. When the target focusing position is larger, the ultrasonic waves are transmitted and received by each element of the array probe based on the ideal delay time required for focusing the ultrasonic wave on the target position. If the target focus position is smaller, a delay time for correction is newly added to the ideal delay time, and ultrasonic waves are emitted from each element of the array probe based on the delay time after addition. Send and receive. For example, the delay time of the triangular distribution is used as the delay time for the correction to be added. As a result, the element on the right side of the array probe tries to focus on the left side of the focus position, and conversely, the element on the left side tries to focus on the right side of the focus position. Therefore, the element on the right has a small contribution to the ultrasonic intensity in the region on the right side of the focusing position, and similarly, the element on the left has a small contribution to the ultrasonic intensity in the region on the left side of the focusing position. Therefore, the ultrasonic intensity at the focusing position becomes relatively large, and the ultrasonic beam diameter becomes small at the focusing position even when the number of driving elements is constant.

[0010]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be described below with reference to the drawings. First, the focus position of the ultrasonic waves, that is, the focal position and the ultrasonic beam diameter will be described. FIG. 10 is an explanatory diagram of interference calculation for calculating the ultrasonic beam diameter at the focus position F. The ultrasonic wave transmitted from the element j has the waveform Wajk (t) shown in Expression 1 at the position Rk.

[0011]

[Equation 1]

Here, t: time Drj: directivity coefficient of a single element ω: angular frequency (= 2πf, where f: frequency) dtj: ideal delay time for focusing ultrasonic waves at a target position ΔT: Correction delay time Ljk: Propagation distance v: Sound velocity α: Coefficient for simulating ultrasonic pulse wave.

The ideal delay time dtj in the element j is calculated by the following equation (2), where the focal length is Fl and the distance from the element j to the focus F is L0.

[0014]

[Equation 2]

The ultrasonic waves transmitted from the n elements overlap each other at the position Rk and form a waveform Wak (t) shown in the following mathematical expression 3.

[0016]

[Equation 3]

Therefore, the intensity Pk when the reflected wave from the position Rk is received by the same n elements can be calculated by the following formula 4.

[0018]

[Equation 4]

For frequency f = 25 MHz and number of elements n = 24, correction delay time ΔT = 0, focus position F (focal length Fl =
The distribution of intensity Pk at 15 mm) is as shown in FIG.
In this intensity distribution, the width (half width) H at which the intensity Pk = 0.5 is defined as the ultrasonic beam diameter. With the frequency f and the number of elements n fixed, the ultrasonic beam diameter H at each focal position F (focal length Fl) was obtained, and the focal length Fl is shown on the horizontal axis and the ultrasonic beam diameter H is shown on the vertical axis. Figure 12 shows It can be seen from FIG. 12 that the ultrasonic beam diameter H is large when the focal position F (focal length Fl) is 8 mm or less.

The ultrasonic beam diameter H obtained by correcting the correction delay time ΔT as a triangular distribution as shown in the upper part of FIG. 10 is shown by a broken line in FIG. From FIG. 12, when the focal position F (focal length Fl) is 6 mm or less, the ultrasonic beam diameter H to which the correction delay time is added is smaller. Therefore, this focus position F (focal length F
l) = 6 mm, the ideal delay time (correction delay time ΔT = 0) is set for F (Fl) ≧ 6 mm, and the correction delay time is added to the ideal delay time for F (Fl) <6 mm. This allows
A small ultrasonic beam diameter H can be obtained even at a small focal position F (focal length Fl). Therefore, here, this 6 mm is referred to as the determination focus position F0. In this case, the determination focal position F0 = 6 mm, but since this value varies depending on the frequency and the number of driving elements, the determination focal length F0 is obtained in advance by interference calculation or experiment.

FIG. 1 is a block diagram of an electronic scanning ultrasonic inspection apparatus according to an embodiment of the present invention which is configured to realize the above. Comparing with the conventional apparatus shown in FIG. The adder 5, the comparator 6, the input device 7, the determination focus position calculator 8, the signal switching device 9, and the ideal delay time generator 10
Is provided.

FIG. 2 is a flow chart showing the procedure of the operation of the embodiment shown in FIG. With the input device 7 of FIG.
The frequency f of the ultrasonic wave, the target focus position F, etc. are input (step 51 in FIG. 2). The determination focus position calculator 8 performs interference calculation based on the frequency f, the number of driving elements n, etc., and calculates the determination focus position F0 (step 52). Next, the comparator 6 determines the determination focus position F0 from the determination focus position calculator 8.
And the focus position F input from the input device 7 are compared (step 55). When the focus position F is larger than the determination focus position F0 (F ≧ F0), a sufficiently small ultrasonic beam diameter H can be obtained with the ideal delay time.
The transmission and reception delay time circuits 11 and 12 are directly connected to the transceiver 4. Therefore, the delay time given to the driving element at this time is calculated by the ideal delay time generator 10 (step 5
3) The ideal delay time set by the transmission and reception delay time circuits 11 and 12 (step 54).

On the other hand, the focus position F is the determination focus position F
When it is smaller than 0 (F <F0), the signal switch 9 connects the correction delay time adder 5 between the transmission and reception delay time circuits 11 and 12 and the transceiver 4. Therefore, the delay time given to the driving element at this time is the ideal delay time plus the correction delay time (steps 56, 5).
7). In this state, each element of the array probe is driven to transmit ultrasonic waves into the subject 2. The reflected waves within the subject 2 are received by the respective elements, and in the reception delay time circuit 12, all the signals are added after the delay time is given to the received signals by the respective elements to form one received signal (step 60). This received signal is output to the display 13 (step 61).

FIG. 3 is a block diagram of an electronic scanning ultrasonic inspection apparatus according to the second embodiment of the present invention, and FIG.
It is a flow chart which shows the operation procedure of an example. In this embodiment, as compared with the first embodiment shown in FIG. 1, the determination focus position F
The determination focus position calculator 8 (FIG. 1) that calculates 0 based on the input value is deleted, and instead, a determination focus position storage 14 that stores the determination focus position previously obtained by interference calculation or experiment is provided. Is different. Therefore, in the flowchart of FIG. 4, the determination focus position F0 is obtained from the flowchart of FIG.
The calculation step of is deleted. In the comparator 6, the determination focus position F0 previously obtained by interference calculation or experiment and stored in the determination focus position storage 14
And the input focus position F are compared (step 74).
The subsequent processing procedure is the same as in the first embodiment (FIGS. 1 and 2). That is, the delay times set in the transmission and reception delay time circuits 11 and 12 are the ideal delay times when F ≧ F0, and the ideal delay times and the correction delay times when F <F0. In this state, ultrasonic waves are transmitted and received, and the received signal is output to the display 13 (step 80).

According to the second embodiment, there is no need to calculate the determination focal point position F0 in the apparatus, which has the advantage of simplifying the processing procedure.

FIG. 5 is a block diagram of an electronic scanning ultrasonic inspection apparatus according to the third embodiment of the present invention, and FIG. 6 is a flow chart showing the operation procedure of the third embodiment. This embodiment is different in that the signal switch 9 of the first embodiment shown in FIG. 1 is deleted.
The comparator 6 of this embodiment compares the judgment focus position F0 obtained by the judgment focus position calculator 8 with the input focus position F (step 105). When F ≧ F0, the correction delay time preset in the correction delay time adder 5 is set in the transmission and reception delay time circuits 11 and 12 (step 10).
4) Add to the ideal delay time (step 107). In this state, ultrasonic waves are transmitted and received and the received signal is output to the display 13 (step 110). When F <F0, the correction delay time set in the correction delay time adder 5 is changed to zero (step 106) and added to the ideal delay time to transmit ultrasonic waves.

According to the third embodiment, since the signal switch 9 is eliminated, there is an advantage that the device structure is simplified.

FIG. 7 is a block diagram of an electronic scanning ultrasonic inspection apparatus according to the fourth embodiment of the present invention, and FIG. 8 is a flow chart showing the operation procedure of the fourth embodiment. In this embodiment, the correction delay time adder 5 and the signal switch 9 of the first embodiment shown in FIG.
And the ideal delay time generator 10 are deleted and a delay time generator 15 is provided instead. That is, in the fourth embodiment, instead of adding the correction delay time to the calculated ideal delay time later, the delay time including the correction delay time is calculated from the beginning. The comparator 6 compares the determined focus position F0 obtained by the determined focus position calculator 8 with the input focus position F (step 123). F <F0
At times, the correction delay time in the delay time generator 15 is set to zero (step 124). On the other hand, when F ≧ F0, the correction delay time preset in the delay time generator 15 is used. Next, the delay time generator 15 calculates the time obtained by adding the correction delay time to the ideal delay time (step 12
Five). The calculated delay time is set in the transmission and reception delay time circuits 11 and 12 (step 126). In this state, ultrasonic waves are transmitted and received, and the received signal is output to the display 13 (step 129).

According to the fourth embodiment, since the delay time including the correction delay time is calculated from the beginning, there is an advantage that the processing procedure and the device configuration are simplified.

In the above embodiment, it is necessary to calculate the delay time each time the target focus position is input. However, if the delay time pattern required for each focus position is obtained and stored in advance, the delay time is calculated in the transmission and reception delay time circuits 11 and 12 only by inputting the target focus position without calculating the delay time. It is also possible to set.

[0031]

According to the present invention, since the ultrasonic beam diameter at the focal position can be made small in the case of inspecting by changing the focal position of ultrasonic waves with the number of drive elements of the array probe fixed, Even small defects can be detected.

[Brief description of drawings]

FIG. 1 is a configuration diagram of an electronic scanning ultrasonic inspection apparatus according to a first embodiment of the present invention.

FIG. 2 is a flowchart showing an operation procedure of the first embodiment of the present invention.

FIG. 3 is a configuration diagram of an electronic scanning ultrasonic inspection apparatus according to a second embodiment of the present invention.

FIG. 4 is a flowchart showing an operation procedure of the second embodiment of the present invention.

FIG. 5 is a configuration diagram of an electronic scanning ultrasonic inspection apparatus according to a third embodiment of the present invention.

FIG. 6 is a flowchart showing an operation procedure of the third embodiment of the present invention.

FIG. 7 is a configuration diagram of an electronic scanning ultrasonic inspection apparatus according to a fourth embodiment of the present invention.

FIG. 8 is a flowchart showing an operation procedure of the fourth embodiment of the present invention.

FIG. 9 is a configuration diagram of a conventional electronic scanning ultrasonic inspection apparatus.

FIG. 10 is an explanatory diagram of ultrasonic interference calculation.

FIG. 11 is an explanatory diagram of an ultrasonic reception intensity distribution and an ultrasonic beam diameter.

FIG. 12 is a diagram showing a relationship between a focal position (focal length) and an ultrasonic beam diameter.

[Explanation of symbols]

1 ... Array probe, 2 ... Subject, 3 ... Drive element switching device,
4 transceivers, 5 ... correction delay time adder, 6 ... comparator, 7
... Input device, 8 ... Judgment focus position calculator, 9 ... Signal switching device,
10 ... Ideal delay time generator, 11 ... Transmission delay time circuit, 12 ...
Reception delay time circuit, 13 ... Display device, 14 ... Judgment delay time storage device, 15 ... Delay time generator.

 ─────────────────────────────────────────────────── ─── Continued Front Page (72) Inventor Fuminobu Takahashi 7-2-1, Omika-cho, Hitachi-shi, Ibaraki Hitachi Energy Research Laboratory, Ltd.

Claims (13)

[Claims] 1. In a method of inspecting by changing the focal position of ultrasonic waves by changing the delay time given to each element of an array probe composed of a plurality of elements, the ultrasonic waves are focused at a target focal position. A delay time necessary for the transmission and reception delay time circuit, a step of comparing a target focus position with a determination focus position, and a correction delay time is added to the delay time related to the setting based on the comparison result. An electronic scanning ultrasonic inspection method comprising steps and a step of transmitting and receiving ultrasonic waves with each element of the array probe. 2. An array probe comprising a plurality of elements,
To add and synthesize ultrasonic waves received by each element, an ultrasonic wave transceiver that drives each element to transmit and receive ultrasonic waves, a transmission delay time circuit that gives a timing to transmit ultrasonic waves from each element In the ultrasonic inspection apparatus including the reception delay time circuit, a comparator for comparing the determined focus position and the target focus position obtained in advance, the transmission delay time circuit based on the comparison result, and An electronic scanning ultrasonic inspection apparatus comprising an adder for adding a correction delay time to an ideal delay time in a reception delay time circuit. 3. An array probe comprising a plurality of elements,
To add and synthesize ultrasonic waves received by each element, an ultrasonic wave transceiver that drives each element to transmit and receive ultrasonic waves, a transmission delay time circuit that gives a timing to transmit ultrasonic waves from each element In the ultrasonic inspection apparatus including the reception delay time circuit, a calculator that calculates the determination focus position based on at least the input values of the frequency and the number of drive elements,
A generator that determines an ideal delay time required for each element based on at least a frequency and an input value of a target focal position,
Electronic scanning, comprising: a comparator for comparing the determination focus position and the target focus position; and an adder for adding a correction delay time to an ideal delay time based on the comparison result. Type ultrasonic inspection equipment. 4. An array probe comprising a plurality of elements,
To add and synthesize ultrasonic waves received by each element, an ultrasonic wave transceiver that drives each element to transmit and receive ultrasonic waves, a transmission delay time circuit that gives a timing to transmit ultrasonic waves from each element In the ultrasonic inspection apparatus including the reception delay time circuit, a storage device that stores a determination focus position obtained in advance, and an ideal required for each element based on at least the input value of the frequency and the target focus position. A generator for obtaining a delay time, a comparator for comparing the determination focus position and the target focus position, and an adder for adding a correction delay time to an ideal delay time based on the comparison result are provided. An electronic scanning ultrasonic inspection apparatus characterized in that 5. An array probe comprising a plurality of elements,
To add and synthesize ultrasonic waves received by each element, an ultrasonic wave transceiver that drives each element to transmit and receive ultrasonic waves, a transmission delay time circuit that gives a timing to transmit ultrasonic waves from each element In the ultrasonic inspection apparatus including the reception delay time circuit, a calculator that calculates the determination focus position based on at least the input values of the frequency and the number of drive elements,
A comparator for comparing the determination focus position and the target focus position, and a generator for determining a delay time given to each element based on at least the input value of the frequency and the target focus position and the result of the comparison are provided. An electronic scanning ultrasonic inspection apparatus characterized in that 6. The correction delay time added to the ideal delay time according to claim 2,
An electronic scanning ultrasonic inspection apparatus characterized by using a delay time of a triangular distribution. 7. A method of inspecting by changing a focal position of an ultrasonic wave by changing a delay time given to each element of an array probe composed of a plurality of elements, in which a target focal position and a judgment focal position are compared. And a step of setting a new delay time for correction to zero according to the comparison result, and a step of setting a delay time necessary for focusing the ultrasonic wave at a target focal position in the transmission and reception delay time circuit. And a step of transmitting and receiving ultrasonic waves with each element of the array probe, the electronic scanning ultrasonic inspection method. 8. An electronic scanning ultrasonic inspection method in which an ultrasonic focusing position is changed by changing a delay time distribution of a drive signal given to each of a fixed number of elements forming an array probe,
When the distance to the target position for focusing the ultrasonic waves is longer than the required distance, each element of the array probe is driven by the delay time distribution for focusing the ultrasonic waves on the target position, and the distance to the target position is the required value. When the distance is shorter than the distance, the delay time distribution for focusing the ultrasonic wave on the target position is corrected, and each element is driven by the delay time distribution where the focus position is far from the target position, and the ultrasonic beam diameter at the target position is reduced. An electronic scanning ultrasonic inspection method characterized by the above. 9. An electronic scanning ultrasonic inspection method in which an ultrasonic focusing position is changed by changing a delay time distribution of a drive signal given to a fixed number of elements forming an array probe,
When the distance to the target position for focusing the ultrasonic waves is longer than the required distance, each element of the array probe is driven by the delay time distribution for focusing the ultrasonic waves on the target position, and the distance to the target position is the required value. When the distance is shorter than the distance, the triangular correction time distribution in which the delay time given to the central element is the longest and the delay time given to the elements at both ends is zero is added to the delay time distribution focusing the ultrasonic wave on the target position. An electronic scanning ultrasonic inspection method characterized in that each element is driven according to a value to reduce the ultrasonic beam diameter at the target position. 10. An object of focusing an ultrasonic wave in an electronic scanning ultrasonic inspection method in which an ultrasonic focusing position is changed by changing a delay time distribution of a drive signal given to each of a fixed number of elements forming an array probe. When the ultrasonic beam diameter at the target position becomes larger than the required diameter due to an element that has a short distance to the position and does not contribute to the focusing of ultrasonic waves, the ultrasonic beam at the target position is corrected by correcting the delay time distribution. An electronic scanning ultrasonic inspection method, wherein the diameter is set to the required diameter. 11. A purpose of focusing an ultrasonic wave in an electronic scanning ultrasonic inspection apparatus which changes an ultrasonic focusing position by changing a delay time distribution of a drive signal given to each of a fixed number of elements forming an array probe. When the distance to the position is longer than the required distance, means for driving each element of the array probe by the delay time distribution that focuses the ultrasonic waves to the target position, and when the distance to the target position is shorter than the required distance Is a means for correcting each delay time distribution for focusing an ultrasonic wave at the target position and driving each element with a delay time distribution for which the focus position is farther than the target position. 12. An object of focusing an ultrasonic wave in an electronic scanning ultrasonic inspection apparatus which changes an ultrasonic focusing position by changing a delay time distribution of a drive signal given to each of a fixed number of elements forming an array probe. When the distance to the position is longer than the required distance, means for driving each element of the array probe by the delay time distribution that focuses the ultrasonic waves to the target position, and when the distance to the target position is shorter than the required distance Is obtained by adding a triangular correction time distribution in which the delay time given to the central element is the longest and the delay time given to the elements at both ends is zero to the delay time distribution for focusing the ultrasonic wave at the target position. An electronic scanning ultrasonic inspection apparatus comprising: a driving unit. 13. An object of focusing an ultrasonic wave in an electronic scanning ultrasonic inspection apparatus which changes an ultrasonic wave focusing position by changing a delay time distribution of a drive signal given to each of a fixed number of elements forming an array probe. When the ultrasonic beam diameter at the target position becomes larger than the required diameter due to a short distance to the position that does not contribute to ultrasonic focusing, the delay time distribution is corrected to change the ultrasonic beam diameter at the target position. An electronic scanning ultrasonic inspection apparatus comprising means for making the required diameter.