JPH0465668A - Ultrasonic microscope - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

DETAILED DESCRIPTION OF THE INVENTION A. Field of Industrial Application The present invention relates to an ultrasonic microscope, which has been improved to particularly improve the accuracy of measuring the V(z) period of a sample.

B. Prior Art FIG. 12 shows the configuration of a conventional ultrasound microscope capable of detecting the V (z) period.

1 is a transmitter that emits, for example, a burst wave, and 2 is a receiver that receives reflected waves from the sample 3. 4 is an ultrasonic probe consisting of a piezoelectric element that converts applied burst waves into ultrasonic waves and an acoustic lens that focuses the ultrasonic waves on sample 3; 5 is a circulator. 6 is a peak checker that detects the peak of the received signal, 7 is an A/D converter that converts the detected peak value into a digital value, and 8 is a device that performs various calculations on the peak detection signal to perform imaging processing, etc. CP to perform
A control circuit includes U, and 9 is a display device that visualizes the video signal from the control circuit 8. Reference numeral 10 denotes a sample stand that can be moved in the X and Y directions in the horizontal plane, ILX and IIY are driving devices that drive the sample stand 10 in the X and Y directions, and 11Z is the sonic probe 4 that is perpendicular to the horizontal quotient. 12 is a drive control circuit for each axis drive device [11X-Z].

Note that 13 is a medium 1, such as water, interposed between the sample 3 and the ultrasonic probe 4.

In such a conventional ultrasound microscope, V(
z) Data is measured.

The medium 13 is dropped onto the sample 3 placed on the XY stage 10 serving as a sample stand, and the ultrasonic probe 4 is brought into contact with it. Transmitter 1
A burst electrical signal is applied to the probe 4 via the circulator 5. The probe 4 converts the electric signal into an ultrasonic signal, focuses it with a lens, and irradiates the sample 3 through the medium 13 .

The ultrasonic signals reflected and scattered by the sample surface layer are detected by the same lens, converted into electrical signals by the piezoelectric element, and then sent to the receiver 2 via the circulator 5. Receiver 2
The electrical signal received is suitably amplified and then sent to the peak detector 6, where the peak value is detected.

As shown in FIG. 13, the ultrasonic signal obtained by the probe 4 is a direct reflected wave directly reflected from the sample 3 (see FIG. 14).
a)) and a surface acoustic wave (see Fig. 14(b)) that propagates on the surface of sample 3 and is reflected. This interference wave is converted into an electrical signal and sent to the circulator. 5 to the receiver 2.

Here, when the distance between the probe 4 and the sample 3 is changed in the Z-axis direction and the intensity of the ultrasonic signal is measured, the amplitude of the ultrasonic signal fluctuates due to the interference between the directly reflected wave and the surface acoustic wave. A V(z') curve as shown in FIG. 3 is obtained. That is,
When a directly reflected wave and a surface acoustic wave interfere in the same phase, the intensity of the interference wave increases (Fig. 14 (c)); when they interfere in opposite phase, the intensity decreases (Fig. 14 (d)), and the intensity of the interference wave increases (Fig. 14 (c)). Probe 4
By moving in the Z-axis direction, the in-phase and anti-phase signals mutually strengthen or weaken each other and interfere, resulting in the V(z) curve shown in FIG. 3. The sound speed and attenuation of the surface acoustic wave of sample 3 can be written from the changing periodic characteristics of this V (z) curve.

C0 Problem to be Solved by the Invention At this time, as the distance between the probe 4 and the sample surface becomes shorter (in the -Z direction in the figure), the intensity of the obtained ultrasonic signal gradually decreases, causing interference. The difference between the maximum and minimum waves becomes smaller. For this reason, the accuracy of calculating the sound speed determined from the period of maximum values (or the period of minimum values) deteriorates. In order to increase the accuracy of this calculation, even if the distance between the probe 4 and the sample surface is shortened, the S/N of the electrical signal converted from the ultrasonic signal must be
The ratio must be good.

The above-mentioned conventional technology does not take into account the detection ability based on the amplitude of a small signal with a V (z) period, and has a problem that the measurement accuracy of the sound velocity and attenuation obtained from the V (z) period measurement data is poor. It was.

An object of the present invention is to provide an ultrasonic microscope with improved measurement accuracy for V (z) periods.

01 Means for Solving the Problems 5 The present invention will be explained in terms of the first factor showing an embodiment. V (z
) used in ultrasound microscopes to measure data.

In addition, the above-mentioned objective 1 is to provide a removal means for removing characteristic data regarding the ultrasonic probe 4 from the V (z) curve of the object sample 3, and to determine the object sample from the signal obtained by this removal means. The periodic signal related to the surface acoustic wave of V (z
) Period calculation means for calculating the period of the curve.

The removal means of the ultrasonic microscope according to claim 2 includes a storage means 23 for storing V (z) data measured on a reference sample in which no surface acoustic waves are excited, and a storage means 23 for storing V (z) data of the detected object sample. and a means 21 for calculating a quantity correlated with the difference in V (z) data of the reference sample stored in the storage means 23. The one-cycle calculating means 8 calculates the V (z) of the subject sample based on the calculated correlation quantity. z) It calculates the period of data.

The removal means of the ultrasonic microscope according to claim 3 includes a coefficient calculation means 8 for calculating a coefficient inversely proportional to V(z) data measured for a reference sample in which no surface acoustic waves are excited, and (z) The one-period calculation means is composed of a multiplication means 31 that multiplies data by a coefficient, and an offset removal means 32 that removes an offset value included in the multiplication result.

Based on the output of the offset removing means 32, the period of V(z) data of the subject sample is calculated.

Characteristic data regarding the ultrasonic probe 4 is removed from the V (z) curve of the E0 effect specimen 3, and a periodic signal related to the surface acoustic waves of the specimen 3 is extracted.

Since the period of the V (z) curve is calculated from this extracted signal, the S/N ratio of the detection signal can be easily improved, and the measurement accuracy of sound speed and attenuation can be improved.

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

F. Embodiment 1 First Embodiment A first embodiment of the present invention will be described with reference to FIGS. 1 to 5. The same parts as in FIG. 12 are given the same reference numerals, and the explanation will focus on the differences.

FIG. 1 is a diagram showing the overall configuration of an ultrasonic microscope according to the present invention. In FIG. 0, a subtracter 21 and an amplifier 22 are connected between a peak detector 6 and an A/D converter 7, and The output of a storage device 23 that stores reference V(z) data in advance is input to a subtracter 21 via a D/A converter 24. The subtracter 21 is the peak detector 6
The difference between the V(z) data output from the V(z) data and the reference V(,z) data stored in the storage device 23 is calculated.

The operation of the first embodiment configured in this manner will be described next.

First, measure reference V (z) data for a sample that does not excite surface acoustic waves, such as gold or Teflon, and compare each measurement point and output voltage with measurement conditions such as sampling pitch, number of measurement points, and focal position. The corresponding measurement results are the standard V
, (z) is stored in the storage @23 as data. At this time, V when gold or Teflon is used as a reference sample.
(z) The data has a characteristic without periodicity as shown in FIG.

Next, a sample to be examined is set, and the probe 4 is set by adjusting the Z-axis so that the focal position of the lens is on the sample surface. Sampling pitch mi1 in conjunction with the standard V (z) data measurement conditions! Number of fixed points.

The measurement start point (defocus amount Zf from the focal position), etc. are set. Further, the gain of the receiver 2 is adjusted so that the output voltage Vmax at the focal position is equal to the output voltage VtaX at that position of the reference sample.

Next, V (z) data of the subject sample is measured while bringing the probe closer to the sample 3 in synchronization with the sampling pitch. At this time, at each sampling point, the output voltage Vt corresponding to the sampling pitch is read from the reference V (z) data measured in advance and stored in the storage device 23, and the value is converted into an analog signal by the D/A converter 24. It is converted into a value and sent to the subtracter 21. The subtracter 21 calculates the sampling pitch, the difference V-Vt between the base IV(z) data Vt and the output voltage V of the V(z) data of the sample currently being measured.
, is calculated. Next, the difference is input to the amplifier 22 and amplified with an appropriate amplification degree, and the value is A/D converted and processed by the control circuit 8.

The reference V (z) data has the characteristics shown in FIG. 2 as described above, and the V (z) data of the test sample has periodic characteristics as shown in FIG. 3. When the difference between the two signals is determined, the result is as shown in FIG. 4, and a signal whose period depends on the surface acoustic waves of the sample is obtained. As the probe 4 approaches the sample, the signal strength decreases and the sensitivity deteriorates, so the amplifier 22 amplifies the entire signal to some extent to increase the sensitivity of minute signals. Then, as shown in Figure 5, the S
The signal with a good /N ratio is A/D converted, and the control circuit 8 performs arithmetic processing.

In this way, with the original signal shown in Figure 3, there is a limit to amplifying the entire V(z) data, so the sensitivity of minute signals is low, and the accuracy of calculating the speed of sound obtained from that value is likely to be poor. In this case, each V (
z) By taking the data difference and amplifying it to increase the sensitivity of the signal, the accuracy of calculating the sound speed of the sample is improved.

Note that the control circuit 8 performs FFT on the signal shown in FIG.
Perform calculations (fast Fourier transform) to obtain a spectrum curve. Then, read the frequency on the horizontal axis with the highest intensity. Since this frequency is the reciprocal of the period ΔZ of the V (z) data to be detected, the period ΔZ can be easily determined.

Once Δ2 is determined, the speed of sound can be determined using a well-known arithmetic expression.

Note that the attenuation characteristics of the test sample can also be determined by detecting the envelope EV of the signal shown in FIG.

-Second Embodiment- A second embodiment of the present invention will be described with reference to FIGS. 6 to 11.

FIG. 6 is an overall configuration diagram showing a second embodiment of the ultrasonic 1# mirror according to the present invention. Components that are the same as those in the first embodiment are given the same reference numerals, and the explanation will focus on the differences.

31 is a variable amplifier whose amplification degree is controlled by the control circuit 8; 32 is an offset converter that removes the offset of the amplified signal; and 33 is an amplifier that amplifies the signal after offset removal with a predetermined amplification degree. It is.

The operation of the second embodiment configured in this way will be explained with reference to the flowchart in Fig. 7.9 First, for a sample such as gold or Teflon in which surface acoustic waves are not excited, Measure standard V (Z) data using water, measure pitch, and number of measurement points.

Measurement conditions for boiled fish position "i", fixed point Z2 and measurement voltage V
The measurement results of tp are stored in the storage device 23 (step 5l-85). At this time, the standard V(z) data obtained from samples such as gold and Teflon have the period shown in FIG. 2 as described above. It becomes a characteristic without gender.

Next, set the sample to be inspected, and move the probe 4 close to the sample 3 in synchronization with the sampling pitch.
(z) data is measured □. First, from the reference V (z) data measured in advance and stored in the storage device 23, the amplification degree K (z) data shown in FIG. In step S6), a value Kp corresponding to the sampling pitch is read from the K (z) data, converted to an analog voltage value by the D/A converter 24, and amplified by the voltage-controlled variable amplifier 31. Send as a control signal.

The variable amplifier 31 sets the amplification degree according to the amplification control signal xp sent for each sampling pitch (steps S7', 'S8). Then, step 89~Sl
1 and detect the V (z) data of the subject sample.

□Step □By repeating steps 87 to 813,
The signal shown in FIG. 9 is obtained.

The above relationship can be expressed as follows.

If the standard "V(z) data as in Part 2 is VO(Z), and the amplification obtained in Figure 8 which is □proportional to its reciprocal □ is 0←2), then (z)= A/V, (z) ・='(1
) However, A is a constant. If V (z') data of the test sample obtained by the conventional method is V, (z), then V, (z) = V, (z) + v (z) ... (
2) However, v(z) is the V(z) characteristic regarding the surface acoustic wave shown in FIG.

becomes. On the other hand, V(z) of the test sample obtained by the one-piece method
If the data is V2 (z), Vz (z)=Ka (z) ・Vz (z)=A+
v (z) V, (z) ... (3). Therefore, as shown in FIG. 9, the offset value A of the first term is added to the second term of equation (3) regarding surface acoustic waves.

Therefore, the output of the variable amplifier 31 is transferred to the offset converter 32.
After offsetting by A, the fixed amplifier 33 performs constant amplification by a factor of B to obtain data 3(z) in equation (4).

As a result, as shown in FIG.
The resulting signal has a strength suitable for /D conversion.

The V 3 (z) data taken in by the A/D converter 7 is calculated by equation (5) in the control circuit 8, and information as shown in FIG. 11 regarding the desired surface acoustic wave is obtained (step 514).

(5) Then, in step S15, FFT calculation is performed, and in step S16, the speed of sound Cr is calculated.

In this way, in cases where the original signal shown in Figure 3 has low sensitivity to minute signals and the accuracy of calculating the sound speed and attenuation obtained from these values becomes poor, it is possible to amplify the signal in synchronization with the movement in the Z direction. By increasing the sensitivity of the signal by making the degree variable, the accuracy of calculating the sound velocity and attenuation of the sample will be improved.

In each of the above embodiments, the subtracter 21 and the storage device jii2
3. Alternatively, the variable amplifier 31 and the offset converter 32 constitute a removing means, and the control circuit 8 constitutes a period calculating means. Further, the subtracter 21 has means for calculating a quantity correlated to the difference between the detected V (z) data and the reference V (z) data.
The control circuit 8 constitutes a coefficient calculation means, the variable amplifier 31 constitutes a multiplication means, and the offset converter 32 constitutes an offset removal means.

G1 Effects of the Invention As described above, according to the present invention, the characteristic data regarding the ultrasound probe is removed from the V(z) curve of the test object sample, and the periodic signal related to the surface acoustic waves of the test object is extracted. teV (z
) Since only the period of the curve is calculated, the S/N ratio of the detection signal can be easily improved, and the measurement accuracy of sound speed and attenuation can be improved.

[Brief explanation of drawings]

FIG. 1 is an overall configuration diagram showing a first embodiment of an ultrasound microscope according to the present invention. FIG. 2 is a diagram showing the V (z) curve of the reference sample. FIG. 3 is a diagram showing the V (z) curve of the test sample. FIG. 4 is a signal waveform diagram obtained by removing characteristic data of the ultrasonic probe from the V(z) curve of the subject sample. FIG. 5 is a waveform diagram in which the signal in FIG. 4 is amplified. FIG. 6 is an overall configuration diagram showing a second embodiment of the ultrasonic microscope according to the present invention. FIG. 7 is a flowchart showing an example of the processing procedure of the second embodiment. FIG. 8 is a graph showing the reciprocal of the V (z) curve of the reference sample shown in FIG. FIG. 9 is a signal waveform diagram obtained when the V(z) curve of the subject sample is amplified with the variable amplification degree shown in FIG.
□FIG. 10 is a signal waveform diagram from which the offset of the signal in FIG. 9 has been removed. FIG. 11 is a signal waveform diagram showing periodic signals related to surface acoustic waves of a subject sample. The 12th article is an overall configuration diagram of a conventional ultrasonic microscope. FIG. 13 is an enlarged view of the acoustic lens and the sample. Figure 14 explains the principle of generating the V (z) curve of the test sample, in which (a) is a waveform diagram showing directly reflected waves, (b) is a waveform diagram showing surface acoustic waves, and (c) is a waveform diagram showing directly reflected waves. ) is a waveform diagram showing a case where two waves interfere in the same phase, and (d) is a waveform diagram when two waves interfere in an opposite phase. 1: Transmitter 2: Receiver 3: Sample 4: Ultrasonic probe 6: Peak detector 8: Control circuit 10: Sample stage 112: Z-axis drive device 21: Subtractor 22: Amplifier

Claims (1)

[Claims] 1) In an ultrasonic microscope that measures V(z) data of a sample based on a detection signal detected while moving an ultrasonic probe toward and away from the sample: A removal means for removing characteristic data regarding the ultrasonic probe from the curve, and a periodic signal related to the surface acoustic waves of the subject sample extracted from the signal obtained by the removal means to determine the period of the V(z) curve. An ultrasonic microscope characterized by comprising period calculation means for calculating. 2) In the ultrasonic microscope according to claim 1, the removing means includes a storage means for storing V(z) data measured on a reference sample in which no surface acoustic waves are excited; ) data and means for calculating a quantity correlated with the difference between the V(z) data of the reference sample stored in the storage means, and the period calculation means calculates the amount of correlation between the V(z) data of the subject sample and the reference sample stored in the storage means, An ultrasound microscope characterized by calculating the period of V(z) data. 3) In the ultrasonic microscope according to claim 1, the removing means includes: a coefficient calculation means for calculating a coefficient inversely proportional to V(z) data measured on a reference sample in which no surface acoustic waves are excited; and a detected object. It consists of a multiplication means that multiplies the V(z) data of the sample by the coefficient, and an offset removal means that removes the offset value included in the multiplication result, and the period calculation means calculates the period based on the output of the offset removal means. An ultrasonic microscope characterized by calculating the period of V(z) data of a subject sample.