JPH04194706A - Ultrasonic inspecting instrument - Google Patents

Abstract

PURPOSE:To accurately measure a distance between the interface of a specimen and a prober and determine the position of the prober without visual observation by calculating the distance between the interface of the specimen and the prober on the basis of the results of sound velocity calculating means and measuring means. CONSTITUTION:The sound velocity C of a medium 5 intervening between an ultrasonic prober 4 and a specimen 6 is calculated by a microcomputer 9 from a difference between reflection times t1 and t2 obtained from a timer 20 and a distance between first and second positions in a Z direction. Therefore, the distance Z1 between the first position and the interface of the specimen 6 can be calculated on the basis of the sound velocity C of the medium 5 and the measuring results of the timer 20, for example, the reflection time t1. Thus, the position of a prober 4 with respect to the interface of the specimen can be obtained by accurately measuring the distance between the prober 4 and the interface of the specimen and contact between the prober 4 and the interface of the specimen can be prevented.

Description

DETAILED DESCRIPTION OF THE INVENTION A. Field of Industrial Application The present invention relates to an ultrasonic inspection device that inspects a sample using ultrasonic waves, such as ultrasonic waves** and ultrasonic flaw detection devices. The present invention relates to an ultrasonic inspection device that can accurately measure the distance between an ultrasonic probe and a sample interface.

B. Prior Art Ultrasonic microscopes, ultrasonic flaw detection devices, and the like are equipped with an ultrasonic probe that transmits and receives ultrasonic waves to and from a sample. When using these devices, a medium mainly consisting of a liquid such as water is filled between the probe and the sample in order to efficiently propagate ultrasonic waves to the sample. In these ultrasonic microscopes and ultrasonic flaw detection devices, probes are placed at the sample interface in order to receive reflected echoes from the sample interface and its interior, and to identify defects inside the sample from the time distribution and signal intensity. It is important to position accurately. Usually, the probe is first brought as close as possible to the sample interface, and then the probe is gradually moved away from the sample, and the probe is positioned at the point where the signal intensity of the reflected echo is highest.

For probes with a focal length of several microns to several tens of microns, the probe is brought close to the sample surface on the order of microns, so conventionally, the first-order method was used to prevent the probe from contacting the sample interface. There is.

Magnify the tip of the probe with the 1# optical microscope mirror and li! Without thinking, bring the probe closer to the sample, and when the tip of the probe approaches the point where it will not touch the sample interface, move the probe closer to the sample to prevent the probe from moving any further toward the sample. Software locks the scanner that controls child movement.

If we think about it simply, we can obtain the echo of the ultrasound at the sample interface, so we can also obtain the time between the ultrasonic transmission pulse and the reflected echo from the sample interface, as well as the speed of sound in the medium. For example, the distance between the ultrasound probe and the sample interface can be calculated. Here, the speed of sound in a medium is a function of temperature, making it difficult to accurately detect the temperature of the medium and requiring a large-scale device. Therefore, conventionally, the most reliable method of visual inspection as described above has been adopted.

Problems to be Solved by the C0 Invention However, in the conventional ultrasound microscope described above, the operator must control the movement of the probe while monitoring the tip of the probe using an optical microscope, which places a burden on the operator. is large. Furthermore, if the operator misses the timing to stop the movement of the probe, the tip of the probe and the sample interface will come into contact, causing damage to both.

An object of the present invention is to accurately measure the distance between a probe and a sample interface without being affected by the temperature of a medium such as water, and thereby determine the position of the probe without visual inspection. The purpose of the present invention is to provide an ultrasonic inspection device that can perform the following functions.

D.Means for solving 31 problems The present invention will be explained in conjunction with FIG. 1, which is an embodiment.

The ultrasonic inspection apparatus according to the present invention includes an ultrasonic probe 4 that emits ultrasonic waves to a sample and receives reflected waves from the sample.
, a moving mechanism 7 for moving the ultrasonic probe 4 back and forth in the Z direction perpendicular to the interface of the sample 6, a piezoelectric element 2 provided at the tip of the ultrasonic probe 4, and a first piezoelectric element in the Z direction. The first reflection time t1 from the interface of the sample 6 when the ultrasonic wave is transmitted from the piezoelectric element 2 at the position and from the interface of the sample 6 when the ultrasonic wave is transmitted from the piezoelectric element 2 at the second position in the Z direction. measuring means 20 for measuring the second reflection time t2 of the ultrasonic probe 4 from these first and second reflection times.
a sound speed calculation means 9 for calculating the sound speed C of the medium 5 interposed between the sample 6 and the sound speed calculation means 9, and the sound speed calculation means 9 and the measurement means 2.
The above object is achieved by providing distance calculation means 9 that calculates the distance between the ultrasonic probe 4 and the interface of the sample 6 based on the result of 0.

The E0 acting sound velocity calculating means 9 calculates the difference between the reflection times t1 and t2 obtained from the measuring means 20, the first position in two directions and the second position.
The sound speed C of the medium 5 interposed between the ultrasonic probe 4 and the sample 6 is calculated from the distance between the positions of . Therefore, the distance calculation means 9 calculates the first
The distance Z1 from the position to the interface of the sample 6 can be calculated.

In the above and E sections that describe the present invention in detail, figures of embodiments are used to make the present invention easier to understand, but the present invention is not limited to the embodiments.

F. Example Hereinafter, an example of an ultrasonic microscope to which the present invention is applied will be described in detail with reference to FIGS. 1 to 3.

Figure 1 is a functional block diagram of the ultrasound microscope, and Figure 2 (a
) and (b) are a sectional view and a bottom view showing an example of a probe of an ultrasound microscope.

In FIG. 2, 1 is an acoustic lens, and the upper surface 1a of this acoustic lens 1 is formed into a flat surface, and a piezoelectric element 3 for flaw detection is provided at the center thereof.

A recess 1c is formed on the lower surface 1b of the acoustic lens 1, facing the piezoelectric element 3 for flaw detection, and ultrasonic waves propagating within the acoustic lens 1 are radiated from the recess 1c. Further, 2 is a distance measuring piezoelectric element provided on the lower surface 1b of the acoustic lens 1 so as to surround the recess IC of the acoustic lens 1, and the piezoelectric element 2 is formed in a ring shape.

Next, in FIG. 1, 4 is the probe shown in FIG. 1, and is arranged so as to face the sample 6 with water (medium) 5 in between. The probe 4 is three-dimensionally movably supported by an XY2 scanner 7, and the XYZ scanner 7 is controlled by a microcomputer 9 via a scanner controller 8. Here, the X direction and the Y direction refer to two directions defined along the interface of the sample 6, and the two directions refer to a direction perpendicular to the interface of the sample 6.

10 is a burst wave oscillator, 11 is a receiver, and the output from the burst wave oscillator 10 is input to the flaw detection piezoelectric element 3 of the probe 4 and the receiver 11, and the output from the piezoelectric element 3 is also input to the receiver 11. be done. 12 is a peak detector, and this peak detector 12 is connected to the receiver 11.
The peak value of the reflected echo is detected, and the detection output is input to the microcomputer 9. 13 is a keyboard, and 14 is an image memory, both of which are connected to the microcomputer 9. 15 is a monitor;
It is connected to the image memory 14.

16 is a pulse wave oscillator, 17 is a receiver, and the output from the pulse wave oscillator 16 is transmitted to the distance piezoelectric element 2 of the probe 4.
and is input to the receiver 17, and the output from the piezoelectric element 2 is also input to the receiver 17 manually. Comparators 18 and 19 are both connected in parallel to the receiver 17, and the output from one comparator 18 is used as a control signal for the other comparator 19.
9 and comparator 19 is input to comparator 18
It is enabled only when receiving a control signal from. Reference numeral 20 denotes a timer to which the outputs of these comparators 18 and 19 are respectively input, and which measures the time difference between the two outputs.The output from this timer 20 is also input to the microcomputer 9.

Next, the operation of this embodiment will be explained with reference to FIGS. 2 and 3.

(a) Flaw detection operation A normal flaw detection operation for the sample 6 will be explained.

When the burst wave output from the burst wave oscillator 10 is input to the flaw detection piezoelectric element 3 of the probe 4, this piezoelectric element 3 generates an ultrasonic wave. This ultrasonic wave is transmitted through the acoustic lens 1
The light is focused by the water 5 and is incident on the sample 6 through the water 5. The ultrasonic waves reflected at the interface or inside the sample 6 return to the probe 4 via the water 5, are converted into electrical signals by the piezoelectric element 3, are amplified by the receiver 11, and sent to the peak detector 12. is input. The peak detector 12 extracts a necessary signal from the input electrical signal and outputs a DC voltage proportional to the peak value of the signal. The DC voltage is input manually to the microcomputer 9, where it is A/D converted and then
It is transferred to the image memory 14 as a digital value.

The above operations are carried out using the XYZ scanner 7, which moves the probe 4 in the
By repeating the scanning while scanning two-dimensionally on the -Y plane, two-dimensional data of the sample 6 is accumulated in the image memory 14. The accumulated data is transferred to the monitor 15 after D/A conversion, and a two-dimensional image is displayed.

Note that the probe 4 can also be moved to an arbitrary position by inputting from the keyboard 13.

(b) Distance measurement Prior to the flaw detection operation described above, it is necessary to position the probe at the correct position according to its focal length. then,
The distance between the probe 4 and the interface of the sample 6 is accurately measured to bring the probe 4 as close to the interface of the sample 6 as possible. Distance measurement is performed by the following operations.

First, as shown in FIG. 3(a), at a first position where the distance between the lower surface of the probe 4, that is, the interface between the piezoelectric element 2 and the sample 6 is Zl, a pulse wave is emitted from the pulse wave oscillator 16. When input to the distance piezoelectric element 2 of the probe 4, an ultrasonic wave is generated from the piezoelectric element 2. This ultrasonic wave
The light propagates through the water as a medium, is reflected at the interface of the sample 6, and returns to the bottom surface of the probe 4. A part of the ultrasonic waves that have returned to the probe 4 enters the piezoelectric element 2 as is, while the rest is reflected and heads again towards the sample 6. After reaching the interface of the sample 6, it is reflected and returns to the probe. Return to the bottom of 4.

By repeating the above steps, a large number of waves reflected from the sample surface are obtained. Among these sample surface reflected waves, as shown in FIG. 3, the time difference t1 between the first reflected wave S1 and the second reflected wave S2 will be measured.

The sample surface reflected wave is converted into an electrical signal by the piezoelectric element 2, amplified by the receiver 17, and then input to the comparator 18. Note that at this stage, the comparator 19 is in a state of waiting for a control signal from the comparator 18, that is, in a state of not accepting a signal from the receiver 17.

The comparator 18 outputs a pulse to the timer 20 and the comparator 19 when a signal exceeding a preset threshold voltage Δv1 is input. As a result, the timer 20 starts a timing operation, and the comparator 19 becomes enabled to receive a signal from the receiver 17. In this state, if a signal exceeding the threshold voltage Δv1 is input to the comparator 19 again, the comparator 19 outputs a pulse to the timer 20. As a result, the timer 20 stops its timekeeping operation and outputs the time difference t1 between the two pulses input from the comparators 18 and 19 to the microcomputer 9. The microcomputer 9 temporarily stores the value of this time difference t1 in its built-in memory. Through the above operations, the time difference t1 between the first reflected wave S1 and the second reflected wave S2 at the first position could be measured.

Next, by commands from the microcomputer 9 or manual input from the keyboard 13, the probe 4 is moved by Δ2 in two directions via the XYZ scanner 7, as shown in FIG. 3(b), and the piezoelectric element When the distance between the interface between the piezoelectric element 2 and the sample 6 is set to Z2, the piezoelectric element 2 emits ultrasonic waves again, and the same operation as described above produces the first reflected wave S1 and the second reflected wave S2. Measure the time difference t2.

At this time, since the peak voltage of the reflected wave changes depending on the movement of the probe 4, the threshold voltage Δ■2 for identifying one reflected wave must also be changed in accordance with the movement of the probe 4. Of course, Zl
>22, ΔVl<8■2, and conversely, Zl<Z
2, ΔVl>ΔV2.

Thereafter, the microcomputer-9 calculates the sound speed of the water (medium) 6 from the time 2itl at the distance z1 and the time difference t2 at the distance Z2.

That is, if the sound speed of water is C, then Z1= (cxtl)/2 (1) Z2= (
CXt2)/2 (2), so these 2
From the formula, C=2ΔZ/(tl-t2) (3)Δz:xy
This is the difference between the distance 21 detected by the encoder attached to the two axes of the Z scanner and the distance Z2. Therefore, the sound speed C of water is determined by substituting Δ2, tl, and 2 into equation (3).

First, once the sound speed C of water has been accurately determined, the microcomputer 9 substitutes each value into the above-mentioned formula to determine the distance z2. Finally, the microcomputer 9 subtracts from 22 a margin ΔM (for example, 0.05 mm) that is enough to prevent the probe 4 and the sample 6 from coming into contact, and changes the current two-axis position W (that is, Z2) by Z2-6M. The coordinate value of the probe 4 in the Z-axis direction when the probe 4 is moved toward the sample 6 is stored. Thereafter, if the microcomputer 9 controls the probe 4 so as not to move it toward the sample 6 beyond the memorized coordinate value of the probe 4 in the Z-axis direction, the probe 4 and the sample 6 will be aligned. contact can be prevented.

Therefore, according to this embodiment, it is possible to measure the distance between the probe 4 and the interface of the sample 6, and therefore the position of the probe 4 with respect to the interface of the sample 6 can be set, and the distance between the probe 4 and the interface of the sample 6 can be set. It is possible to prevent a situation in which the interface between the sample 4 and the sample 6 comes into contact with each other. In particular, since the distance between the probe 4 and the interface between the sample 6 and the sample 6 can be measured without visual inspection as in the past, the distance between the probe 4 and the interface between the sample 6 and the sample 6 can be significantly reduced. This has the excellent advantage that the position of the probe 4 relative to the interface can be set accurately and reliably.

Note that the details of the ultrasonic inspection apparatus according to the present invention are not limited to the embodiments described above, and various modifications are possible.

- As an example, in the embodiment described above, a comparator was used to specify the position of the reflected wave, but it goes without saying that other peak detection means may be used. That is, as shown in FIG. 2, a peak detector 21 similar to the peak detector 12 for sample flaw detection is connected to the receiver 17, and the output of this peak detector 21 is inputted to the microcomputer 9 to be read by the microcomputer 9. The time difference may be measured using software using the computer 9. At this time, if the peak voltage of the reflected wave S1 at the distance z1 is PVI, and the peak voltage of the reflected wave S1 at the distance Z2 is PV2, then the threshold voltage Δ at the position NZ2 is
(2) 2 may be set as ΔV2=ΔVIX (PV2/PVI). In addition, in the above-mentioned embodiment, the distance to the probe 4 was determined from the time difference t1-t,2 between the reflected waves S1 and S2, but the The distance of the probe 4 may be determined from the time difference with the wave S1. Similarly, the distance of the probe 4 may be determined by averaging a plurality of time differences obtained from a combination of a plurality of reflected waves and using this as the time difference between the reflected waves.

In the configuration of the above embodiment, the XYZ scanner constitutes a moving mechanism, the timer 20 constitutes a measuring means, and the microcomputer 9 constitutes a sound velocity calculating means and a distance calculating means, respectively.

G0 Effects of the Invention As described in detail above, according to the present invention, the distance between the probe and the sample interface can be accurately measured to determine the position of the probe with respect to the sample interface, and the probe It is possible to prevent the situation of contact between the sample and the sample interface. In particular, according to one aspect of the present invention, the distance between the probe and the sample interface can be measured in the same way as normal flaw detection without visual inspection as in the past, which greatly reduces the burden on the operator. This method has the excellent advantage that the position of the probe relative to the sample interface can be set accurately and reliably.

[Brief explanation of the drawing]

1 to 3 show an embodiment of an ultrasonic microscope to which an ultrasonic inspection device according to the present invention is applied, FIG. 1 is a block diagram showing the overall configuration of the ultrasonic microscope, and FIG. 2 is a probe (a) is a front sectional view, (b) is a bottom view, and FIG. 3 is a diagram for explaining the operation of the ultrasonic microscope. 1: Acoustic lens 2: Piezoelectric element for distance 3: Piezoelectric element for flaw detection 4: Probe 5: Water 6: Sample 7: XYZ scanner 9: Microcomputer 1
8: Comparator 19: Comparator 20: Timer 21: Peak detector.

Claims (1)

[Scope of Claims] An ultrasonic probe that emits ultrasonic waves to a sample and receives reflected waves from the sample, and a moving mechanism that moves the ultrasonic probe forward and backward in the Z direction perpendicular to the interface of the sample. a piezoelectric element provided at the tip of the ultrasonic probe; a first reflection time from the interface of the sample when the ultrasonic wave is transmitted from the piezoelectric element at the first position in the Z direction; When the ultrasonic wave is transmitted from the piezoelectric element at the second position in the Z direction, the second
a measuring means for measuring the reflection time of; a sound velocity calculating means for calculating the sound speed of a medium interposed between the ultrasonic probe and the sample from the measured first and second reflection times; Based on the results of the calculation means and the measurement means,
An ultrasonic inspection apparatus comprising distance calculation means for calculating a distance between the probe and the interface of the sample.