JPH03289562A - Method and apparatus for measuring velocity distribution of surface wave - Google Patents

Abstract

PURPOSE:To widen the range capable of measuring the speed of a surface wave of a sample by controlling the emitting angle of the bulk wave converted from a leakage Lumb wave by the control of the frequency of an applied AC signal. CONSTITUTION:One surface of a piezoelectric substrate 28 comes into contact with absorbing bodies 40, 42 and the other surface thereof has a transmitting screen electrode 30 and receiving screen electrodes 32, 34 formed thereto. A radio frequency pulse signal 108 for driving the electrode 30 is applied to the electrode 30 of a leakage Lamb wave element 26 from a radio frequency pulse generator 44. Those electrodes 30, 32, 34 are arranged to the substrate 28 along the longitudinal direction thereof and the bulk wave converted from the Lamb wave generated from the electrode 30 is emitted to a sample. At this time, the bulk waves emitted from the first and second regions of a transmission route are received by the electrodes 32, 34 and the change quantity of the second region to the velocity of the surface wave of the first region is calculated on the basis of the phase difference between both bulk waves. Whereupon, since the emitting angle of the bulk wave to the sample can be controlled on the basis of the signal 108, the corresponding surface wave is excited in the sample and the range capable of measuring the velocity of the surface wave can be widened.

Description

DETAILED DESCRIPTION OF THE INVENTION (Industrial Application Field) The present invention relates to a method and apparatus for measuring the surface wave velocity distribution of a sample, and in particular to a method and apparatus for measuring the surface wave velocity distribution of a sample from changes in the surface wave velocity propagating through the sample. The present invention relates to a method and apparatus for measuring velocity distribution.

(Prior Art) Several measurement methods are provided as methods for measuring the surface wave velocity of a sample. As a method for measuring the surface wave velocity of a sample such as a piezoelectric material, a wave transmitting interdigital electrode and a wave receiving interdigital electrode are respectively deposited on the sample, and the wave transmitting interdigital electrode excites surface waves in the sample. , the surface wave is received by the wave-receiving interdigital electrode, the surface wave propagation time is measured until the surface wave reaches the wave-receiving interdigital electrode from the wave-transmitting interdigital electrode; There is a method that measures the surface wave velocity from the surface wave propagation time.

Furthermore, there is a method in which the phase difference of the surface waves is measured instead of the surface wave propagation time, and the surface wave velocity is measured from the phase difference.

On the other hand, as a method for measuring the surface wave velocity of a sample such as a non-piezoelectric material, a wedge-shaped vibrator is brought into contact with the sample, a surface wave is excited in the sample by the wedge-shaped vibrator, and the propagation time of the surface wave is Alternatively, the surface wave velocity can be determined by measuring the phase difference.

(Problem to be Solved by the Invention) However, in the method for measuring the surface wave velocity of a piezoelectric material, a wave-transmitting interdigital electrode for exciting surface waves in a sample and a wave-receiving interdigital electrode for receiving the surface waves. Since the interdigital electrodes are vapor-deposited onto the sample, the process of vapor-depositing each interdigital electrode is labor-intensive and adds extra time to the measurement process.

In addition, in the surface wave velocity measurement method for non-piezoelectric materials, by using a wedge-shaped oscillator, the wedge angle of the wedge-shaped oscillator converts the waves from the wedge-shaped oscillator into surface waves of the non-piezoelectric material. To determine the efficiency, it is necessary to select the wedge angle of the wedge-shaped vibrator according to the material of the non-piezoelectric material, etc., and it takes extra time to select or prepare a wedge-shaped vibrator with a predetermined wedge angle. It takes.

In order to reduce the extra time required for measurement work, V(f
) curve method has been proposed. The V(f) curve method involves placing a sample in a liquid, and having a piezoelectric substrate whose one surface is in contact with the surface of the liquid, and a surface wave interdigital electrode that excites surface waves in the piezoelectric substrate. A leaky surface wave generator is driven while changing its driving frequency, and a bulk wave in the liquid converted from the leaky surface wave generated in the leaky surface wave generator is radiated toward the sample, thereby generating a surface wave on the sample. A wave is excited, and a first wave receiving means disposed at the interface with the liquid receives a first bulk wave emitted into the liquid from a first part located on a surface wave propagation path of the sample. a second bulk wave emitted into the liquid from a second portion located in the surface wave propagation path of the sample with a second wave receiving means disposed at the interface with the liquid; , the surface wave velocity is determined from the period of change in the phase difference between the bulk wave received by the first wave receiving means and the bulk wave received by the second wave receiving means.

However, in the V(f) curve method described above, by exciting the surface wave in the sample by the bulk wave in the liquid converted from the leaky surface wave generated in the leaky surface wave generator, the bulk wave in the liquid is Since the angle of incidence on the sample corresponds to an angle near the Rayleigh critical angle determined by the ratio of the propagation velocity of the bulk wave in the liquid to the surface wave velocity of the sample, it is determined by the characteristics such as the material of the sample. The surface wave velocity imposes restrictions on the angle of incidence of the bulk wave in the liquid onto the sample, and the range of the sample in which the surface wave velocity can be measured is limited to an extremely narrow range.

An object of the present invention is to provide a surface wave velocity distribution measuring method and apparatus that can widen the range of samples whose surface wave velocities can be measured and that do not require extra time for measurement work.

(Means for Solving the Problems) The surface wave velocity distribution measuring method of the present invention forms a liquid layer on the surface of a sample, and applies pressure to a substrate and the piezoelectric substrate with one surface in contact with the liquid surface. A wave transmitting means having a wave transmitting interdigital electrode formed on the other surface of the piezoelectric substrate to excite the rum liquid, a first wave receiving means, and a second wave receiving means are sequentially connected to the wave transmitting means. The Lamb waves excited in the piezoelectric substrate are arranged along the traveling direction, and the bulk waves converted from the leaky Lamb waves generated therein by the wave transmitting means are radiated into the liquid toward the sample. Exciting a surface wave and receiving a first re-radiated bulk wave emitted into the liquid from a first part located on a surface wave propagation path of the sample with the first wave receiving means, A second re-radiated bulk wave radiated into the liquid from a second site located on a surface wave propagation path is received by the second wave receiving means, and is received by the first wave receiving means. The phase difference between the first re-radiated bulk wave received by the second wave receiving means and the second re-radiated bulk wave received by the second wave receiving means determines the surface wave velocity of the second portion relative to the surface wave velocity of the first portion. Find the amount of change in surface wave velocity.

The surface wave velocity distribution measuring device of the present invention includes a liquid layer formed on the surface of a sample, a piezoelectric substrate whose one surface is in contact with the surface of the liquid, and a layer formed on the other surface of the piezoelectric substrate. a wave transmitting means having a wave transmitting interdigital electrode that excites Lamb waves in the piezoelectric substrate; and an interval between the wave transmitting means and the wave transmitting means along the traveling direction of the Lamb waves excited in the piezoelectric substrate of the wave transmitting means. radiated into the liquid from a first portion of a surface wave propagation path of the sample when a surface wave is excited in the sample by a bulk wave converted from a leaky Lamb wave of the reverse wave means. a first wave receiving means for receiving a first re-radiated bulk wave and outputting a first received signal corresponding to the received first re-radiated bulk wave; and a traveling direction of the Lamb wave. are arranged at a position spaced apart from each of the wave transmitting means and the first wave receiving means and adjacent to the first wave receiving means along the surface wave, and when the surface wave is excited in the sample. receiving a second re-radiated bulk wave emitted into the liquid from a second portion of the surface wave propagation path of the sample, and a second receiving wave corresponding to the received second re-radiated bulk wave; a second receiving means for outputting a signal; a first receiving signal from the first receiving means and a second receiving signal from the second receiving means; a phase difference detection means for detecting a phase difference between the received signal and the second received signal and outputting a phase difference signal corresponding to the phase difference; and calculation means for calculating the amount of change in surface wave velocity based on the phase difference signal and outputting a speed signal corresponding to the amount of change in surface wave velocity.

The wave transmitting means includes a leaky Lamb wave element that integrally includes the first and second wave receiving means, and the leaky Lamb wave element includes:
the piezoelectric substrate, the wave transmitting interdigital pole, and a first wave receiving device formed on the other surface of the piezoelectric substrate and working together with the piezoelectric substrate to define the first wave receiving means. a second wave-receiving interdigital electrode formed on the other surface of the piezoelectric substrate and working together with the piezoelectric substrate to define the second wave-receiving means; and one of the piezoelectric substrates. a first absorber formed on a surface of the piezoelectric substrate and disposed between the wave transmitting interdigital electrode and the first wave receiving interdigital electrode, and a first absorber formed on one surface of the piezoelectric substrate; a second absorber disposed between the first wave-receiving interdigital electrode and the second wave-receiving interdigital electrode; and a second absorber formed on the other surface of the piezoelectric substrate;
It is preferable to have a third absorber facing the first absorber and a fourth absorber formed on the other surface of the piezoelectric substrate and facing the second absorber.

It is preferable to include a scanning means for moving the wave transmitting means relative to the sample together with the first and second wave receiving means.

It is preferable to include a tank containing the liquid and holding the sample in the liquid.

(Operation) When driving the wave transmitting means, an AC signal having a frequency F is applied to the wave transmitting interdigital electrode of the wave transmitting means, and a Lamb wave of a frequency F is applied to each surface of the piezoelectric substrate of the wave transmitting means. excite. Since one surface of the piezoelectric substrate is in contact with the liquid surface, the Lamb waves propagate through the piezoelectric substrate, and a portion of the Lamb waves are converted into bulk waves propagating in the liquid.

The Lamb wave that is converted into the bulk wave is called a leaky Lamb wave.

The radiation angle θ0 of the bulk wave, the velocity V of the bulk wave, and the velocity VL of the leaky Lamb wave satisfy the relationship shown by the following equation (1), and the velocity Θ of the leaky Lamb wave is expressed by the leakage Lamb wave. It is expressed by the product of the wave number of the Lamb wave and the pressure@substrate thickness d, and since the leaky Lamb wave has a plurality of modes, each having a different velocity dispersion characteristic, the alternating current signal By changing the frequency F of the bulk wave, the radiation angle θ
, can be controlled.

When the bulk wave is incident on the sample, a surface wave is excited in the sample by the bulk wave, so that the angle of incidence of the bulk wave on the sample is determined by the propagation velocity of the bulk wave in the liquid and the sample. Since the Rayleigh critical angle is determined by the ratio of the surface wave velocity to the surface wave velocity of This can be achieved by controlling the wave radiation angle θ.

The leaky Lamb wave element integrally includes the wave transmitting means and the first and second wave receiving means, so that the positional relationship between the wave transmitting means and the first and second wave receiving means is determined in advance. Since the wave length is determined, it is possible to easily position the wave transmitting means and the first and second wave receiving means with respect to the sample.

By providing the scanning means, the sample and the wave transmitting means 2. Since the scanning means moves relative to the first and second wave receiving means, the measurement site of the sample can be easily changed.

By holding the sample in the liquid in the tank, the layer of liquid formed between the sample and the piezoelectric substrate is hardly affected by disturbances, so that the liquid layer formed between the sample and the piezoelectric substrate is not easily affected by disturbances. Movement can be prevented.

(Example) Fig. 1 is a block diagram showing an embodiment of the surface wave velocity distribution measuring device of the present invention, and Fig. 2 shows the principle of measuring the surface wave velocity distribution of the surface wave velocity distribution measuring device of Fig. 1. Figure 3 is a plan view showing the leaky Lamb wave element used in the surface wave velocity distribution measuring device shown in Figure 1, and Figure 4 is a cross-sectional view taken along line A-A in Figure 3. It is.

The surface wave velocity distribution measuring device 10, as shown in FIG.
A tank 1 containing water 12 and holding a sample 14 in the water 12
6. The tank 16 consists of a square tank that opens upward. The tank 16 is placed on a movable table 22 that moves along a sliding surface 20 of a fixed table 18.

The moving table 22 includes a drive unit (not shown) for moving it.
is provided. The driving section moves the movable table 22 based on a control signal output from the scanning control section 24. The scanning control section 24 cooperates with the driving section and the moving table 22 to form scanning means.

When the first control signal 100 is given to the drive unit from the scanning control unit 24, the drive unit moves the movable table 22 to the sliding surface 2.
0 in the X-axis direction defined therein by a predetermined amount of movement. When the second control signal 102 is given to the drive section, the drive section moves the movable table 22 along the sliding surface 20 by a predetermined movement amount in the Y-axis direction perpendicular to the X-axis direction. When the control signal 104 is given to the drive unit, the drive unit rotates the movable table 22 by a predetermined angle around the vertical axis.

Furthermore, when the scan control unit 24 outputs any one of the first, second, and third control signals 100, 102, and 104, it corresponds to the movement direction and movement amount indicated by the output control signal. A scanning position signal 106 is output from the scanning control section 24.

A leaky Lamb wave element 26 is arranged within the treetop 16 .

The leaky Lamb wave element 26, as shown in FIGS. 3 and 4, has a piezoelectric substrate 28 with one surface in contact with the water port. The piezoelectric substrate 28 has a rectangular shape.
6 (product name, manufactured by Tohoku Metals).

On the other side of the piezoelectric substrate 28, a wave transmitting interdigital 1@pole 3 is provided.
o, a first wave-receiving interdigital electrode 32 and a second wave-receiving interdigital electrode 34 are formed.

The wave transmitting interdigital electrode 30 and the first and second wave receiving interdigital electrodes @32.34 are composed of regular interdigital electrodes with 5 electrode pairs, and the electrode period length is p, The distance between the electrodes is d. It is. The wave transmitting interdigital electrode 30 and the first and second wave receiving interdigital electrodes 32 and 34 are arranged at intervals along the longitudinal direction of the piezoelectric substrate 28.

On the other side of the piezoelectric substrate 28, first and second volume receiving bodies 36, 38 are formed. The first absorber 36 is disposed between the wave transmitting interdigital electrode 30 and the first wave receiving interdigital electrode 32, and the second absorber 38 is disposed between the first wave receiving interdigital electrode 32. and the second wave-receiving interdigital electrode 34. On the other hand, a third absorber 40 facing the first absorber 36 and a fourth absorber 42 facing the second absorber 38 are formed on one surface of the piezoelectric substrate 28. .

The transmission interdigital electrode 30 of the leaky Lamb wave element 26 receives a radio frequency pulse signal (rRF
It is called "signal". ) 108 is the radio frequency pulse generator 44
Applied from The radio frequency pulse generator 44 outputs an operation signal 110 instructing to start oscillation at the same time as starting the oscillation of the RF signal 108, and outputs an operation signal 110 instructing to stop the oscillation at the same time as stopping the oscillation of the RF signal 108.

When driving the leaky Lamb wave element 26, the RF signal 108 from the radio frequency pulse generator 44 is transmitted to the transducer interdigital electrode 3.
Applied to 0. Lamb waves are excited in the piezoelectric substrate 28, and the traveling direction of the Lamb waves coincides with the longitudinal direction of the piezoelectric substrate 28. The first wave-receiving interdigital wave of the Lamb waves! f
The Lamb wave toward 132 is absorbed by the first and third absorbers 36.4
0, the Lamb wave is absorbed into the first and second
Since the waves are not incident on the receiving interdigital electrodes 32 and 34,
The outputs of the first and second wave-receiving blinds &32, 34 are prevented from being interfered with by the Lamb wave.

As shown in FIG. 2, while the Lamb waves propagate through the piezoelectric substrate 28, a portion of the Lamb waves are converted into bulk waves 46 that propagate in the water 12. The Lamb waves that are converted into bulk waves 46 are called leaky Lamb waves.

Assuming that the velocity of the leaky Lamb wave is V + and the velocity of the bulk wave 46 is -, then the radiation angle θ of the bulk wave 46 with respect to the normal to one surface of the piezoelectric substrate 28 is. satisfies the following equation (1). In addition, the velocity (1) of the leaky Lamb wave is determined by a numerical analysis method that is an improved version of Farnel's method, and is expressed as a function of the product of the wave number of the leaky Lamb wave and the thickness d of the piezoelectric substrate 28. .

As shown in FIG. 5, the leaky Lamb wave has many modes. FIG. 5 is a diagram showing the velocity dispersion characteristics of leaky Lamb waves. As is clear from FIG. 5, the velocity of the leaky Lamb wave differs for each mode. In addition, A in the figure...
, 2. , denotes the antisymmetric mode, S o, 1. x, s indicate the symmetric mode, and each subscript indicates the mode order. On the other hand, the ○ marks in Figure 5 indicate the experimental values of the velocity in each mode of the leaky Lamb wave when the electrode period length β of the interdigital electrode is 380 μm, and the ・ mark indicates the @polar period length ρ of the interdigital electrode. As is clear from FIG. 5 and equation (1), which show the experimental values of the velocity in each mode of the leaky Lamb wave when It can be seen that a leaky Lamb wave of a predetermined mode can be obtained by changing . As a result, by controlling the frequency of the RF signal 108, the radiation angle θ of the bulk wave 46 can be controlled.

As shown in FIG. 6, the effective conversion efficiency, which indicates the rate at which the leaky Lamb wave is converted into the bulk wave, differs for each mode. FIG. 6 is a diagram showing the effective conversion efficiency, which is the rate at which the leaky Lamb waves excited by the leaky Lamb wave generator of FIG. 3 are converted into underwater bulk waves.

As shown in FIG. 2, the bulk wave 46 is radiated toward the sample 14 from the surface of the piezoelectric substrate 28 that is opposite to the surface on which the wave transmitting interdigital electrode 30 is formed. The radiation angle θ of the bulk wave 46 is the incident angle θ of the bulk wave 46 on the sample 14.
0 corresponds to the Rayleigh critical angle determined by the ratio of the velocity V of the bulk wave 46 and the surface wave velocity of the sample 14 by the frequency of the RF signal 108.

When the bulk wave 46 reaches the portion 48 of the sample 14, a leaky surface wave 50 is excited in the sample 14 because the incident angle θ0 of the bulk wave 46 on the sample 14 approximately matches the Rayleigh critical angle. A part of the bulk wave 46 that is specularly reflected by the sample 14 is absorbed by the absorber 40, and the absorber 40 absorbs the bulk wave 46.
A part of 6 is the first and second wave receiving interdigital wire 'jf1
32.34 to prevent reception.

While the leaky surface wave 50 of the sample 14 propagates through the sample 14,
A portion of the leaky surface waves 50 is converted into a re-radiated bulk wave that is radiated into the water 12 from a portion of the sample work 4 located on the surface wave propagation path. The emitted re-radiated bulk wave 54 is received by the first receiving interdigital electrode 32, and the re-radiated bulk wave 58 emitted from the second portion 56 is received by the second receiving interdigital electrode 34. waves are received. The second and fourth absorbers 38 and 42 are disposed between the first wave-receiving wave-shaped electrode 32 and the second wave-receiving wave-shaped electrode 34, so that the first The wave receiving interdigital electrode 32 is not affected by the re-radiated bulk wave 58, and the second wave receiving interdigital electrode 34 is not affected by the re-radiated bulk wave 54.
Therefore, each of the first and second wave-receiving interdigital electrodes 32, 34 can reliably receive the corresponding re-radiated bulk wave.

When the first wave-receiving interdigital electrode 32 receives the re-radiated bulk wave 54, the first wave-receiving signal 112 corresponding to the re-radiated bulk wave 54 is output from the first wave-receiving interdigital electrode 32. be done. When the second wave-receiving interdigital electrode 34 receives the re-radiated bulk wave 58, the second wave-receiving signal 114 corresponding to the re-radiated bulk wave 58 is transmitted to the second wave-receiving interdigital electrode 34.
is output from.

The first received signal 112 and the second received signal 114 are provided to the phase difference detection means 60. First received signal 112
After it is shaped by the waveform shaping circuit 62, it is passed through the phase shifter 64.
given to. The phase shifter 64 converts the first received signal 112 into a reference signal 11 with a phase difference of 90'' from the first received signal 112.
6 and output.

The second received signal 114 is applied to a phase comparator 68 after being shaped by a waveform shaping circuit 66 .

The phase comparator 68 receives the reference signal 1 output from the phase shifter 64.
16 and the second received signal 114.
Detects the reference phase difference between the phase of It outputs a phase difference signal 118 having the following characteristics. The reference signal 116 is the first
By having a phase that is 90° different from the phase of the received signal 112, the value of the reference phase difference increases.
The phase comparator 68 can accurately compare the reference phase difference. As a result, the phase difference signal 118 accurately corresponds to the difference between the phase of the first received signal 112 and the phase of the second received signal 114.

For example, as shown in FIG. 7, the voltage value of the phase difference signal 118 is equal to
It changes linearly with respect to the difference from the phase of 14. FIG. 7 is a diagram showing the relationship between the voltage of the phase difference signal and the difference between the phase of the first received signal and the phase of the second received signal.

The phase difference signal 118 output from the phase comparator 68 of the phase difference detection means 60 is given to the calculation means 70. When the calculation means 70 receives the operation signal 110 instructing the start of oscillation from the radio frequency pulse generator 44, the calculation means 70 takes in the phase difference signal 118, and calculates the amount of change in surface wave velocity ΔV based on the voltage value of the phase difference signal 118. Calculate.

The phase difference indicated by the voltage value of the phase difference signal 118 is Δφ, the distance from the first part 52 to the second part 56 along the surface wave propagation direction is Δρ, and the constant determined from the physical property values of the sample 14 is When k, the phase difference Δφ satisfies the following equation (2): Δφ= ΔρΔV (2) The speed change amount ΔV can be determined. The constant and the distance Δρ are set in advance in the calculation means 70.

When the calculation means 70 receives the signal 110 instructing to stop oscillation from the radio frequency pulse generator 44, the calculation means 70 stops taking in the phase difference signal 118, and also outputs the speed signal 120 corresponding to the speed change amount Δ■. Output.

The speed signal 120 output from the calculation means 70 is displayed on the display means 72 together with the scanning position signal 106 from the scan control section 24.
The 0 display means 72 given to the scanning position signal 106 calculates the position of the measurement part of the sample 14 with respect to a preset reference position from the movement direction and movement amount indicated by the scanning position signal 106, and calculates the position of the measurement part and the speed signal 120. Displays the speed change amount ΔV.

Next, a measurement operation when measuring the surface wave velocity distribution of a sample using the surface wave velocity distribution measuring device 10 will be described.

Figure 8 is a perspective view showing an example of the sample to be measured, Figure 9 is a diagram showing the measurement results of the surface wave velocity distribution in the X-axis direction of the sample in Figure 8, and Figure 10 is a diagram showing the measurement results of the surface wave velocity distribution of the sample in Figure 8. A diagram showing the measurement results of the surface wave velocity distribution in the Y-axis direction, Figure 11 is a perspective view showing another example of the sample to be measured, and Figure 12 shows the measurement results of the surface wave velocity distribution of the sample in Figure 11. The figure shown in FIG. 13 is a diagram showing the results of numerical calculation of the surface wave velocity distribution of the sample in FIG. 11.

When measuring the surface wave velocity distribution of the disk-shaped piezoelectric ceramic 74, as shown in FIG. They are arranged at the bottom of the tank 16 so as to coincide with the intersection origin 0.

The piezoelectric ceramic 74 has a polarization axis extending in its thickness direction (the direction indicated by mark 9 in FIG. 8). piezoelectric ceramic 7
The diameter dimension of No. 4 is 50 cnm.

The leaky Lamb wave element 26 uses interdigital electrodes with an electrode period length ρ of 210 μm.

First, the radio frequency pulse generator 44 is driven.

The radio frequency pulse generator 44 includes a wave transmitting interdigital electrode 30.
is S. It oscillates an RF signal 108 having a frequency capable of generating a mode leaky Lamb wave, and at the same time outputs an operation signal 110 instructing to start oscillation.

The RF signal 108 is applied to the transmitting interdigital electrode 30,
A leaky Lamb wave is excited in the piezoelectric substrate 28.

The velocity ■o of the leaky Lamb wave in the S0 mode is approximately 2.5+on/s, as shown in FIG. The leaky Lamb wave of the So mode is converted into a bulk wave 46, and the bulk wave 46 has an angle θ equal to 1/Illy critical angle. is incident on the piezoelectric ceramic 74. A leaky surface wave 50 is excited in the piezoelectric ceramic 74 by the bulk wave 46, and a portion of the leaky surface wave 50 is converted into a re-radiated bulk wave 54,58.

The re-radiated bulk wave 54 is received by the first wave-receiving interdigital electrode 32, and the re-radiated bulk wave 58 is received by the second wave-receiving interdigital electrode 34. First wave receiving interdigital electrode 32
The first received signal 112 output from the second receiving interdigital electrode 34 and the second received signal 11 outputted from the second interdigital receiving interdigital electrode 34.
4 is given to the phase difference detection means 60, and the phase difference detection means 6
0 is the phase of the first received signal 112 and the second received signal 11
A phase difference signal 118 corresponding to the difference from the phase of 4 is output.

The calculation means 70 receives an operation signal 110 that instructs to start oscillation.
Since the phase difference signal 118 is taken into the calculation means 70 each time the phase difference signal 118 is given, the calculation means 70 calculates a preset standard as the amount of change in surface wave velocity at the portion 76 based on the voltage value of the phase difference signal 118. Calculate the speed change amount Δ■ from the value.

Next, the radio frequency pulse generator 44 stops oscillating the RF signal 108 and provides an operation signal 110 to the calculation means 70 instructing to stop the oscillation. The calculation means 70 calculates the phase difference signal 11
The display means 72 stops the capture of 8 V and gives the speed signal 120 corresponding to the speed change of 18 V to the display means 72.
The amount of speed change ΔV that the speed signal 120 does not indicate is displayed at the coordinates of the position of the part 76 and 6.

Front frequency pulse generator 44 stops oscillating RF signal 108! - After that, the driving part of the moving table 22 receives the first control signal 10.
2, by moving the moving table 22 by 0.5 degrees in the
78.

After the scanning operation is completed, the leaky Lamb wave element 26 is driven, and the amount of velocity change Δ■ is measured at a portion 78 of the piezoelectric ceramic 74. As a result, the surface wave velocity distribution along the X-axis direction of the piezoelectric ceramic 74 can be measured by repeating the measurement operation and the scanning operation alternately. The measurement results of the surface wave velocity distribution along the X-axis direction of the piezoelectric ceramic 74 are shown in FIG.

The surface wave velocity distribution along the Y-axis direction of the piezoelectric ceramic 74 is obtained by scanning the piezoelectric ceramic 74 in the )'-axis direction, as shown in FIG. Note that the deviation values indicated by the vertical axes in FIGS. 9 and 10 are values based on the measured value at the origin (part 76).

As shown in FIG. 11, the piezoelectric ceramic 82 is made of a plate having a polarization axis (marked in the figure) perpendicular to the thickness direction. When measuring the velocity distribution of a surface wave propagating along a plane parallel to the polarization axis of the piezoelectric ceramic 82, the piezoelectric ceramic 82 is arranged so that its central region 84 coincides with the origin 0 defined at the bottom of the horizontal plane 16. , located at the bottom of the tank 16.

The leaky Lamb wave element 26 has an electrode period length p of 380 J1 m.
An interdigital electrode is used. The mode of the leaky Lamb wave generated by the transmitting wave electrode 30 is A0.
mode. The velocity of the leaky Lamb wave in Ao mode is,
As shown in FIG. 5, scanning at a speed of approximately 1.8 km/s is performed by rotating the moving stage 22 around the Z-axis at an angular pitch θ of 2 degrees, thereby detecting the measurement portion of the piezoelectric ceramic 82. is the circumference of a circle whose radius is the center region 84 and the distance Δρ from it.

Since the region is located at As is clear from FIGS. 12 and 13, it can be seen that the measurement results almost match those of the numerical needle 9. As a result, the surface wave velocity distribution measuring device 10
can be applied to the anisotropic piezoelectric ceramic 82.

(Effects of the Invention) According to the method of the present invention, the radiation angle of the bulk wave converted from the leaky Lamb wave is controlled by controlling the frequency of the applied AC signal, and by controlling the radiation angle of the bulk wave. Said bulk wave.

Since the angle of incidence on the sample matches the Rayleigh critical angle, which varies according to the surface wave velocity determined by the characteristics of the sample, such as the material, surface waves corresponding to the characteristics of the sample are excited in the sample. This greatly expands the range of samples whose surface wave velocities can be measured.

According to the apparatus of the present invention, the angle of incidence of the bulk wave on the sample is made to match the Rayleigh critical angle by controlling the radiation angle of the bulk wave, so that surface waves corresponding to the characteristics of the sample are excited in the sample. This makes it possible to widen the range of samples whose surface wave velocities can be measured.

The leaky Lamb wave element integrally includes the wave transmitting means and the first and second wave receiving means, so that the positional relationship between the wave transmitting means and the first and second wave receiving means is determined in advance. Since the wave transmitting means and the first and second wave receiving means can be easily positioned with respect to the sample.

By providing the scanning means, the relative movement of the sample, the wave transmitting means, and the first and second wave receiving means is performed by the scanning means, so that the measurement site of the sample can be easily changed. be able to.

[Brief explanation of drawings]

FIG. 1 is a block diagram showing an embodiment of the surface wave velocity distribution measuring device of the present invention, FIG. 2 is a diagram showing the principle of measuring surface wave velocity distribution of the surface wave velocity distribution measuring device of FIG. 1, and FIG. The figure is a plan view showing the leaky Lamb wave element used in the surface wave velocity distribution measuring device shown in Fig. 1, Fig. 4 is a cross-sectional view taken along line A-A in Fig. 3, and Fig. 5 is a diagram showing the velocity dispersion characteristics of leaky Lamb waves, Figure 6 is a diagram showing the effective conversion efficiency, which is the ratio of leaky Lamb wave to liquid bulk wave conversion in the leaky Lamb wave element of Figure 3, and Figure 7 is a diagram showing the velocity dispersion characteristics of leaky Lamb waves. A diagram showing the relationship between the voltage of the phase difference signal and the difference between the phase of the first received signal and the phase of the second received signal, FIG. 8 is a perspective view showing an example of a measurement sample, and FIG. Figure 10 shows the measurement results of the surface wave velocity distribution in the Y-axis direction of the sample in Figure 8. Figure 11 shows the measured sample. Fig. 12 is a diagram showing the measurement results of the surface wave velocity distribution of the sample in Fig. 11, and Fig. 13 shows the results of numerical calculation of the surface wave velocity distribution of the sample in Fig. 11. FIG. 10...Surface wave velocity distribution measuring device, 12...Water, 1
4... Document, 16... Tank, 22... Moving table (scanning means), 24... Scanning control unit (scanning means), 26.
...Leaky Lamb wave element, 28...Piezoelectric substrate, 30...
Wave-transmitting interdigital electrode, 32... First wave-receiving interdigital electrode, 34... Second wave-receiving interdigital electrode, 36.3
840.42... Absorber, 44... Radio frequency pulse generator, 52... First part, 56... Second part, 60... Phase difference detection means, 70... calculation means, 7
4.82...Piezoelectric ceramic. A 0 0.2 0.4 0.6 0.8 1.0 1.2 4 60 =40 -20 0 +20 Phase difference angle (degrees) +40 +60 Figure 8○ 0.2 0.4 0 .6 0.8 0 1.2 4 3 2 -1 0 1 Position in the X-axis direction (mm) Fig. 9 +2 Mo3 3 2 -1 0 -1-I Position in the Y-axis direction Nakam) +2 +3 10th yI 30 0 Rotation angle θ (degrees) 0 Figure 12 Rotation angle θ (degrees)

Claims (5)

[Claims] (1) A layer of liquid is formed on the surface of the sample, and a piezoelectric substrate is formed on the other surface of the piezoelectric substrate and one surface is in contact with the liquid surface, and a layer of liquid is formed on the piezoelectric substrate to excite the ram liquid. A wave transmitting means having a wave interdigital electrode, a first wave receiving means, and a second wave receiving means.
and a wave receiving means of the wave transmitting means are sequentially arranged along the traveling direction of the Lamb wave excited in the piezoelectric substrate of the wave transmitting means, and a bulk wave converted from a leaky Lamb wave generated therein by the wave transmitting means is transmitted into the liquid. A surface wave is excited in the sample by radiating toward the sample, and a first re-radiated bulk wave is radiated into the liquid from a first portion located on a surface wave propagation path of the sample. The second wave receiving means receives a second re-radiated bulk wave that is received by the first wave receiving means and radiated into the liquid from a second portion located on the surface wave propagation path of the sample. From the phase difference between the first re-radiated bulk wave received by the first wave receiving means and the second re-radiated bulk wave received by the second wave receiving means, A surface wave velocity distribution measuring method for determining the amount of change in the surface wave velocity of the second part with respect to the surface wave velocity of the first part. (2) A layer of liquid formed on the surface of the sample, a piezoelectric substrate whose one surface is in contact with the surface of the liquid, and a Lamb wave formed on the other surface of the piezoelectric substrate. a wave transmitting means having interdigitated electrodes for transmitting waves that excite the wave transmitting means; a first re-radiated bulk wave radiated into the liquid from a first portion of a surface wave propagation path of the sample when a surface wave is excited in the sample by a bulk wave converted from a leaky Lamb wave of the means; a first wave receiving means for receiving a first re-radiated bulk wave and outputting a first received signal corresponding to the received first re-radiated bulk wave; Said first
a second portion of the surface wave propagation path of the sample when the surface wave is excited in the sample; a second re-radiated bulk wave that corresponds to the received second re-radiated bulk wave;
a second receiving means for outputting a received signal; a first receiving signal from the first receiving means and a second receiving signal from the second receiving means; a phase difference detection means for detecting a phase difference between the first received signal and the second received signal and outputting a phase difference signal corresponding to the phase difference; and a phase difference from the phase difference detection means. A surface wave velocity distribution measuring device comprising: a calculation means to which a signal is applied, calculates an amount of change in surface wave velocity based on the phase difference signal, and outputs a moderate signal corresponding to the amount of change in surface wave velocity. (3) The wave transmitting means includes a leaky Lamb wave element that integrally includes the first and second wave receiving means, and the leaky Lamb wave element includes the piezoelectric substrate and the wave transmitting interdigital electrode. , a first wave receiving interdigital electrode formed on the other surface of the piezoelectric substrate and working together with the piezoelectric substrate to define the first wave receiving means; and a first wave receiving interdigital electrode formed on the other surface of the piezoelectric substrate. a second wave-receiving interdigital electrode that cooperates with the piezoelectric substrate to define the second wave-receiving means; and a second wave-receiving interdigital electrode formed on one surface of the piezoelectric substrate and defining the wave-transmitting interdigital electrode. a first absorber disposed between the first wave-receiving interdigital electrode; and a first absorber disposed on one surface of the piezoelectric substrate, the first wave-receiving interdigital electrode and the second a second absorber disposed between the wave receiving interdigital electrode; a third absorber formed on the other surface of the piezoelectric substrate and facing the first absorber; The surface wave velocity distribution measuring device according to claim 2, further comprising a fourth absorber formed on the other surface of the piezoelectric substrate and facing the second absorber. (4) The surface wave velocity distribution measuring device according to claim 2 or 3, further comprising scanning means for moving the wave transmitting means relative to the sample together with the first and second wave receiving means. (5) The surface wave velocity distribution measuring device according to claim 2, further comprising a tank containing the liquid and holding the sample in the liquid.