JPH0772005A - Measuring device for minute periodic vibration displacement - Google Patents

Abstract

(57) [Summary] [Object] To provide a displacement measuring device capable of easily measuring the surface displacement of an object to be measured in a wide range at the same time and detecting the phase in addition to the amplitude intensity. A periodic electric signal is applied to the piezoelectric body 12 by an oscillator 17, and the surface displacement of mechanical vibration excited by the signal is optically measured. The semiconductor laser light source 11 is momentarily caused to emit light by the pulse generator 18 in synchronization with the electric signal input to the piezoelectric body 12, and the surface displacement is captured in the image input means 14 as still image data.
Reference numeral 19 is a frame memory, and 20 is an image display means. Reference numeral 16 is a lens, 15 is a beam splitter, and 13 is a reference plane, which constitutes a Michelson interferometer. 1
Reference numeral 31 is a drive unit for moving the reference plane, which enables fringe scanning.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a device for measuring minute periodic vibration displacement, and more particularly to a device for measuring minute periodic vibration displacement on the surface of an elastic body by an image.

[0002]

2. Description of the Related Art In recent years, elements or devices using a piezoelectric material, such as ultrasonic motors, surface acoustic wave elements, and optical surface acoustic wave elements, have been increasing in importance in recent years and are being actively researched. . The behavior of elastic waves propagating in these is very complicated, and various means for measuring or observing them have been considered.

FIG. 10 and FIG. 11 each show a system for measuring an elastic wave propagating through an object to be measured at one point, which is a technique usually called an optical probe method.

The system shown in FIG. 10 is one of conventional examples in which a surface acoustic wave element is irradiated with a laser beam and the first-order diffracted light thereof is detected. In the figure, 101 is a surface acoustic wave element as an object to be measured, 102 is a laser light source, 103 is a photodetector, 104 is a slit for separating directly reflected light and first-order diffracted light, and 105 is a surface acoustic wave element. Mounted movable stage, 106 is a potentiometer for measuring the position of the stage, 107 is an oscillator for exciting the surface acoustic wave element 101 with surface acoustic wave, and 109 is the surface acoustic wave element 1.
A pulse generator for turning on / off the signal input to 01 at a certain cycle, a mixer 108, a lock-in amplifier 110 for detecting a signal synchronized with the pulse generator 109, and an XY recorder 111. Is. When the surface acoustic wave propagates to the portion irradiated with the laser light, diffracted light is generated in the traveling direction of the surface acoustic wave and the opposite direction due to the surface roughness of the element due to the surface acoustic wave. At this time,
The amplitude intensity of the surface acoustic wave is measured by measuring the first-order diffracted light and the directly reflected light.

The system of FIG. 11 is one of the conventional examples of observing elastic waves with an optical fiber ring interferometer. In the figure, 11 is a light source, 112 and 112 'are directional couplers,
Reference numeral 113 is a delay loop, 114 is a short optical path, 115 is a condenser lens, 116 is a light receiving element, and 12 is an object to be measured. Laser light emitted from the light source 11 is split into a delay loop 113 and a short optical path 114 by a directional coupler 112. After passing through the delay loop 113 and the directional coupler 112 ′,
The light is reflected by the measurement surface of the DUT 12, passes through the short loop 114, passes through the directional coupler 112 again, and receives the light receiving element 116.
The surface displacement of the elastic body, which is the object to be measured, is measured by the interference between the light that has reached the point and the light that has reached the light receiving element 116 by the opposite route.

FIG. 12 shows another example of a conventional elastic wave observation system. In the case of this system, after the light from the laser light source S is diffracted by the ultrasonic diffraction cell 121 and passed through the slit S1, the non-diffracted light is spread by the lens L1, and the object to be measured 12
Irradiate the entire range of 0 that you want to observe. In this method, a hologram is formed on the photosensitive plate hrg by the interference between the light diffracted by the ultrasonic diffraction cell 121 and the light diffracted by the surface acoustic wave propagating on the DUT 120. L2 and L3 are lenses, and S2 is a slit. L4 and L5 are lenses, S3 is a slit, and SCR is a reproduced image forming screen. Reference numeral 122 is an optical system for hologram production.
Reference numeral 3 is an optical system for reproducing an elastic wave propagation pattern. In this system, the hologram h is reproduced by the reproduction optical system 123.
By irradiating rg, not only the amplitude intensity of the surface acoustic wave but also phase information can be observed.

The system of FIG. 10 and the system of FIG. 12 are described in “Surface Acoustic Wave Engineering; The Institute of Electronics, Communication and Communication, Chapter 6, Measurement Technology”, and the system of FIG.
50 Committee 25th Study Meeting Material "Measurement and evaluation of piezoelectric vibration by ring interference method; Oki, Shima, Shiozaki".

[0008]

Although the method of FIG. 10 is very simple, since the surface roughness of the surface acoustic wave propagates to the surface of the element is used as a diffraction grating, the wavelength of the surface acoustic wave is reduced. It must be sufficiently large with respect to the laser beam diameter. For this reason, if the surface acoustic waves do not propagate in phase within the range of the laser beam diameter, it is difficult to detect the diffracted light and the wavelength level of the surface acoustic waves cannot be observed. Further, the magnitude of the amplitude of the surface acoustic wave is obtained from the ratio between the 0th order light and the 1st order diffracted light of the laser, but phase information cannot be obtained.

In the system of FIG. 11, information on the magnitude and phase of the surface displacement of the elastic body can be obtained, and the measurement can be performed with high sensitivity even at a high frequency. However, in the case of the optical probe method, since only one point of data can be obtained, a highly accurate stage controller is required.

On the other hand, the method of FIG. 12 has a problem that it is troublesome that a hologram has to be created each time.

In view of the above-mentioned problems of the prior art, the present invention provides a displacement measuring device capable of easily measuring the surface displacement of an object to be measured simultaneously in a wide range and detecting the phase in addition to the amplitude intensity. The purpose is to do.

[0012]

According to the present invention, in order to achieve the above object, a periodic electric signal is applied to a piezoelectric body, and the surface displacement of mechanical vibration excited by the signal is optically transmitted. In the device for measuring the above, a measuring device for minute periodic vibration displacement, characterized in that surface displacement is captured as still image data by instantaneously emitting a light source in synchronization with an electric signal input to a piezoelectric body, Provided.

Here, image data when the periodic light emission of the light source has a certain phase difference θ with an electric signal input to the piezoelectric body, and the periodic light emission of the light source is input to the piezoelectric body. The displacement may be measured by subtracting the generated electric signal and the image data when the phase difference is θ + 180 °.

Further, according to the present invention, in order to achieve the above object, an apparatus for applying a periodic electric signal to a piezoelectric body and optically measuring a surface displacement of mechanical vibration excited by the signal. At, the period of the electric signal input to the piezoelectric body and the light emission period of the light source are slightly different,
There is provided a measuring device for minute cyclic vibration displacement, characterized in that the surface displacement of the piezoelectric body is measured as a beat signal based on a difference between a cycle of an electric signal input to the piezoelectric body and a light source emission cycle.

In the above-mentioned present invention, the optical system of the means for measuring the surface displacement of the mechanical vibration includes a Michelson interferometer or a Fizeau interferometer. , A Fabry-Perot interferometer can be used. Here, as the optical system, one having means for executing the fringe scanning method of the interference fringes can be used. Further, it is possible to use one in which the optical system has means for controlling the movement of the piezoelectric body, and has means for joining and synthesizing image data of a plurality of obtained interference fringes.

In one aspect of the present invention, the electric signal input to the piezoelectric body is a burst signal, and the light source is controlled so as not to emit light during a time period when the electric signal is not input to the piezoelectric body. Alternatively, the shutter of the image input means is controlled to be closed during the same time period. According to this, heat generation and fatigue deterioration of the device are prevented.

In another aspect of the present invention, the light source is a semiconductor laser. A multi-quantum well type semiconductor laser can be used as the semiconductor laser.

[0018]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Specific embodiments of the present invention will be described below with reference to the drawings.

(Embodiment 1) FIG. 1 shows a first embodiment of the present invention. The present embodiment is an example in which an optical system is configured using a Michelson interferometer. Reference numeral 11 is a light source, 12 is an object to be measured (piezoelectric body), 13 is a reference surface of an interferometer, 131 is a mechanism for moving the reference surface back and forth, 14 is an image input means such as CCD, and 15 is a beam splitter (half mirror). ), 16 is a lens, 17 is a generator (oscillator) of a signal input to the object to be measured (piezoelectric body), 18 is a pulse generator, 19 is a frame memory for accumulating image data, and 20 is an image display means such as a CRT. Is. The pulse generator 18 is synchronized with the generator 17 of the input signal to the DUT 12, and controls the light emission of the light source 11.

FIG. 2 shows the operating principle of this embodiment. In the figure, w1 and w2 are two parallel light ray components output from the light source 11, and the beam splitter 15 is w1 and w2.
It is inserted at an angle of 45 ° with respect to 2. These light ray components w1 and w2 are split by the beam splitter 15, a part of which is reflected and perpendicularly enters the measurement surface of the DUT 12, and another part of which is transmitted and perpendicularly enters the reference surface 13. The electric field at the point where each beam is reflected by the measured surface or the reference surface and reaches the beam splitter 15 again is as follows: E _r1 = A _r1 Sin (ω ₁ t−2L _{r 1} / λ ₁ + φ _{1) ... (1) E r2} = A r2 Sin (ω 1 t-2L r2 / λ 1 + φ 2) ... (2) E s1 = A s1 Sin (ω 1 t-2L s1 / λ 1 + φ 1) ... ( _{3) E s2 = a s2 Sin} (ω 1 t-2L s2 / λ 1 + φ 2) ... (4) here, E _r1 beam w1 is transmitted through the beam splitter 15, is reflected by the reference surface 13, again the beam Splitter 1
5, E _r2 is the electric field when the beam w2 reaches the beam splitter 15 along a similar path, E _s1
Is the electric field when the beam w1 is reflected by the beam splitter 15, is reflected by the measurement surface of the DUT 12 and is transmitted through the beam splitter 15, and E _s2 is the electric field when the beam w2 is transmitted through the beam splitter 15 through a similar path. It is an electric field. Also, A _r1 , A _r2 , A _s1 , and A _s2 are the amplitudes of the respective electric fields,
ω ₁ and λ ₁ are the angular frequency and wavelength of the light from the light source, t is time, and L
_{In r1} , L _r2 , L _s1 , and L _s2, the beams w1 and w2 are the distances from the beam splitter 15 to the reference plane and the measurement plane, φ1, φ
2 is the initial phase of the beams w1 and w2.

The respective light intensities I _o1 and I _o2 detected by the image input means 14 are the interference between the beam of the formula (1) and the beam of the formula (3), and the beam of the formula (2) and the formula (4). since the it is the interference of the beam, represented by the following _{formula: I o1 = (E r1 +} E s1) 2 = a r1 2/2 + a s1 2/2 - (a r1 2/2) Cos2 (ω 1 t _{-2L r1 / λ 1 + φ 1} ) - (A s1 2/2) Cos2 (ω 1 t-2L s1 / λ 1 + φ 1) -A r1 A s1 Cos (2ω 1 t + 2φ 1 -2 (L r1 + L s1) _{/ λ 1) + A r1 A} s1 Cos (2 (L r1 -L s1) / λ 1) ... (5) I o2 = (E 2r + E 2s) 2 = A r2 2/2 + A s2 2/2 - (A ^{_{r2 2/2) Cos2 (ω}} 1 t-2L r2 / λ 1 + φ 2) - (A s2 2/2) Cos2 (ω 1 t-2L s2 / λ 1 + φ 2) -A r2 A s2 Cos (2ω 1 _{t + 2φ 2 -2 (L r2} + L s2) _{λ 1) + A r2 A s2} Cos (2 (L r2 -L s2) / λ 1) ... (6) (5) and equation (6) the first term and the reference plane or interference surface and the second term of the right side of DC component independent of distance to the third
The items 5 to 5 are components having a frequency twice that of light and are not detected by the image input unit 14. Only the sixth term is a component that depends on the difference in the distance between the reference surface and the interference surface. If there is no displacement due to elastic waves on the measurement surface and the two beams have the same intensity, equations (5) and ( The sixth term of the equation (6) becomes equal, and the image input means 14 detects uniform brightness. L _s1 and L
_s2 is the distance L when there is no displacement due to elastic waves on the measurement surface
_s10 , L _s20 and the point s where the two beams hit the measurement surface
The distance d between 1, s2 and the initial phase θ of the elastic wave at the point s2 can be written as equations (7) and (8): L _s1 = L _s10 + aSin (ω ₂ t + θ + d / λ ₂ ). (7) L _s2 = L _s20 + aSin (ω ₂ t + θ) (8) where a is the amplitude of the elastic wave, ω ₂ is the angular frequency of the elastic wave,
λ ₂ is the wavelength of the elastic wave.

Since the image input means 14 normally has a time integration function, when the period of the elastic wave is sufficiently shorter than the integration time of the image input means 14, that is, the image input means 14
2 is lower than the frequency of the elastic wave, the second terms of the equations (7) and (8) are averaged and no displacement is observed. Therefore, in the present invention, the light source emits pulses in synchronization with the angular frequency ω ₂ of the elastic wave. In FIG. 2, after emitting light at time t ₀ when the phase of the elastic wave is represented by the solid line, it does not emit light at time t ₁ when the phase of the elastic wave is reversed, and the elastic wave progresses and returns to the phase of the solid line again. When the light source emits light, the light is emitted again at time t ₂ (7).
Since the distances L _s1 and L _s2 expressed by the equations and the equation (8) are fixed, the light quantity of each point integrated by the image input means 14 is also fixed, and the interference fringes can be observed.

By the way, when observing a displacement of the light source or less with a single frequency optical interferometer, a method of moving the reference surface at the wavelength level and scanning the interference fringes (so-called fringe scanning method) is often used. The mechanism 131 for moving the reference plane back and forth is a mechanism for this purpose, and its principle will be described below.

The sixth terms of equations (5) and (6) are
I_1ac , I_2ac And the equations (7) and (8)
Substituting for: I_1ac = A_r1A_s1Cos (2 (L_r1-L_s10 -ASin (ω₂ t + θ + d / λ ₂ )) / Λ₁ ) = A₀₁Cos (A₂ Sin (ω₂ t + θ + d / λ₂ ) + Ψ₁ )… (9) I_2ac = A_r2A_s2Cos (2 (L_r2-L_s20 -ASin (ω₂ t + θ)) / λ ₁ ) = A₀₂Cos (A₂ Sin (ω₂ t + θ) + ψ₂ )… (10) (where A₀₁= A_r1A_s1, A₀₂= A_r2A_s2, A₂ =-
2a / λ₁ , Ψ₁ = 2 (L_r1-L_s10 ) / Λ₁ , Ψ₂ =
2 (L_r2-L_s20 ) / Λ₁ = Ψ₁ ) Where ψ₁ (Also
Is ψ₂ ) About λ₁ Integrate over the range of. That is,
L by moving the illumination surface_r1, L_r2Λ₁ In the range of
Change the image data captured at each reference plane position.
Data on the frame memory. By this
The expressions (9) and (10) are the expressions (11) and (12).
And the phase change of the interference fringes due to the elastic wave becomes a sine wave.
The change is around 0 degree, which is the most sensitive function.
Ru: S_1ac = ∫I_1ac dψ₁ = A₀₁Sin (A₂ Sin (ω₂ t + θ + d / λ₂ )) (11) S_2ac = ∫I_2ac dψ₁ = A₀₂Sin (A₂ Sin (ω₂ t + θ)) (12) Furthermore, twice the displacement of the measurement surface due to the elastic wave is the wavelength of the light source.
λ₁ Value A standardized by₂ Is small enough, S_1ac , S
_2ac Becomes equations (13) and (14), and
The phase change of the interference fringes is given by a sinusoidal function: S_1ac = A₀₁A₂ Sin (ω₂ t + θ + d / λ₂ )… (13) S_2ac = A₀₂A₂ Sin (ω₂ t + θ) (14) In the actual fringe scan method, the reference plane is moved back and forth.
The position of the reference plane can be
Control at the wavelength level, for example by shifting the phase by 90 °
The four image data are fetched and these are integrated. Book
Such a method can also be used in the invention.

(Embodiment 2) FIG. 3 is a view for explaining a second embodiment of the present invention, and shows how elastic waves propagate when the measurement surface 31 of the object to be measured is not flat. in this case,
When the light source emits light only at the same phase as the times t ₀ and t ₂ as in the first embodiment, the surface displacement due to the elastic wave and the deviation from the plane of the measurement surface in this phase state are overlapped with each other to cause the displacement 32 of the solid line. To be observed. Here, when the measurement surface of the DUT is observed in the same manner so that the light source emits light only when the phase is the same as the time t ₁ which is the phase opposite to t ₀ and t ₂ , the displacement of the dotted line in FIG. 33 are observed. Taking the difference between the time t ₀ in the frame memory 19 of FIG. 1, t ₂ and the image data and the time t ₁ when the in-phase and image data when the same phase, cancel the deviation from the plane of the measuring surface 31 Therefore, only changes in surface displacement due to elastic waves can be observed.

(Embodiment 3) FIG. 4 is a diagram for explaining a third embodiment of the present invention, which has the same configuration as that of FIG. 1 and has a pulse emission period 2π / ω _{o of the} light source and an elastic wave period 2π / ω _s. The phase of the elastic wave observed when and are slightly shifted is shown. In the figure, the vertical axis represents the displacement of a point on the measurement surface and the horizontal axis represents time. Here, if an elastic wave with a period of 2π / ω _s is irradiated by a pulse light source with a period of 2π / ω _o and its displacement is detected, the beat of the pulse light emission frequency of the light source and the frequency of the elastic wave is detected as a wavy line. It becomes as if the elastic wave is displaced at a period of 2π / | ω _o −ω _s |. Beat cycle 2
If π / | ω _o −ω _s | is sufficiently longer than the integration time of the image input means 14, displacement of the measurement surface due to elastic waves is observed.

(Embodiment 4) FIG. 5 is a diagram showing a fourth embodiment of the present invention. The present embodiment is an example in which an optical system is configured using a Fizeau interferometer. Reference numeral 11 is a light source, 12 is an object to be measured (piezoelectric body), 13 is a reference surface of an interferometer, 131 is a mechanism for moving the reference surface back and forth, 14 is an image input means such as CCD, and 15 and 15 'are beam splitters ( Half mirror), 16 is a lens, 17 is a signal generator (oscillator) for inputting to the object to be measured (piezoelectric body), 18 is a pulse generator, 1
9 is a frame memory for accumulating image data, 20 is a CR
Image display means such as T, 21 is a lens for forming an image on the measurement surface. The light emitted from the light source 11 is directed downward by the beam splitter 15 ′ and is directed to the beam splitter 15 via the lens 21. The beams split by the beam splitter 15 are reflected by the measurement surface and the reference surface 13, respectively, combined by the beam splitter 15, and observed by the image input means 14 such as a CCD.

In the case of the Fizeau interferometer, since interference fringes can be obtained by the same principle as that of the Michelson interferometer, the first embodiment
The displacement of the measurement surface can be measured by the same method as described above. Also,
In the case of a Fizeau interferometer, it is easy to make the optical path length difference between the reference light and the measurement light almost zero.
A multimode laser can be used as a light source. In the case of the present invention, it is necessary to make the light source emit light in pulses, and when the semiconductor laser is made to emit light in pulse mode, a multimode is normally produced, but this structure can be used.

(Embodiment 5) FIG. 6 shows a fifth embodiment of the present invention. The present invention is an example in which an optical system is configured using a Fabry-Perot interferometer. Reference numeral 11 is a light source, 12 is an object to be measured (piezoelectric body), 14 is an image input means such as a CCD, 1
5 and 15 'are beam splitters (half mirrors), 15
1, 151 'is a mechanism for moving the half mirror 15 back and forth, 16 is a lens, 17 is a generator (oscillator) of a signal to be input to an object to be measured (piezoelectric body), 18 is a pulse generator, 19
Is a frame memory for storing image data, 20 is a CRT
Image display means 61, 61 'are lenses for vertically injecting light rays onto the measurement surface and the half mirror. The light emitted from the light source 11 is directed downward by the beam splitter 15 ′ and passes through the lenses 61 and 61 ′ to the beam splitter 1.
Go to 5. The interference light intensity of the beam that is multiply reflected by the beam splitter 15 and the measurement surface is determined by the image input means 1 such as CCD.
Observed at 4.

FIG. 7 shows the principle of the Fabry-Perot interferometer. For the sake of explanation, the state in which the beam is obliquely incident is shown in the figure, but the beam is actually the half mirror 1.
5 or perpendicularly to the measurement surface 71. In the figure, B0 is a beam reflected by the half mirror 15, B1 is a beam which is transmitted through the half mirror 15 and is reflected by the measurement surface 71, is again transmitted by the half mirror 15, and B2 is transmitted by the half mirror 15 and is measured on the measurement surface. Reflected at 71, half mirror 1
The beams B3, B4, ..., Which are reflected by the beam No. 5, again reflected by the measurement surface 71, and transmitted through the half mirror 15 again, are beams which have been repeatedly reflected in the same manner and then transmitted through the half mirror 15.

The electric fields of the respective beams are represented by E _b0 , E _b1 , E
_b2, ... interference light intensity I _fp and a is given by _{(15): I fp = (E b0 +} E b1 + E b2 + ...) 2 = {A fp r h Cosω 1 t + A fp t h 2 r s Cos (Ω ₁ t + 2ψ) + A _fp t _h ² r _h r _s ² Cos (ω ₁ t + 4 ψ) + A _fp t _h ² r _h ² r _s ³ Cos (ω ₁ t + 6 ψ) ····} ² (15) Where, A _fp is the amplitude of the electric field of the light incident on the half mirror 15, r _h and t _h are the reflection coefficient and the transmission coefficient of the half mirror 15, and r _s is the reflection coefficient of the object to be measured. ψ is a value obtained by dividing the distance between the half mirror 15 and the measurement surface 71 by the wavelength of light.

FIG. 8 shows the equation (15) in which r _h = t _h =
The relationship between the interference light intensity when 0.5 and r _s = 1 and the distance between the measurement surface and the half mirror is shown. If the distance between the half mirror 15 and the measurement surface 71 is controlled so as to reach the point P, even if the displacement due to the elastic wave on the measurement surface is small, there is a large change in intensity and the sensitivity can be improved.

(Embodiment 6) FIG. 9 shows a conceptual diagram in the case where a plurality of images 94, 95, 96 captured according to the present invention are combined and synthesized to measure a displacement due to a large range of elastic waves. The figure shows the displacement of the measurement surface due to the surface acoustic wave excited by the comb-shaped electrode 93.
Usually, the displacement due to elastic waves is very small compared to the range to be measured, so if the object to be measured is controlled and moved on the movable stage and multiple images are captured, the pitching of the stage, the plane accuracy, the object to be measured, and so on. Due to the plane accuracy and the like, the phase of the interference fringes may shift in different images even at the same measurement point. However, in the case of the present invention, when a frame memory is provided in the measuring device to capture a plurality of images and measure a large range, the portions 91 and 9 for inputting the images in an overlapping manner.
2 is provided, and the phase of the interference fringes can be corrected in this portion.

In the present invention, the light source 11 is a light source capable of pulsed light emission. Further, in order to capture as an image and to have a degree of freedom in designing the distance between the reference surface and the measurement surface, it is desirable that the light source is a laser having high coherence. When measuring the surface acoustic wave device with the device of the present invention, the desired pulse width is several nanoseconds or less because the frequency of the surface acoustic wave is high. In this case, a solid-state laser or a gas laser requires a large light source, and thus a semiconductor laser is suitable. In particular, a multi-quantum well semiconductor laser is suitable for this application because it does not easily become a multimode even if it emits pulses.

[0035]

As described above, according to the present invention, in a device for applying a periodic electric signal to a piezoelectric body and optically measuring the surface displacement of mechanical vibration excited by the signal, the object to be measured is The displacement due to the elastic wave can be instantly detected in a wide range, and the amplitude intensity and phase of the elastic wave propagating through the measured object can be easily detected.

[Brief description of drawings]

FIG. 1 is a schematic configuration diagram showing a first embodiment of the present invention.

FIG. 2 is a diagram showing the principle of a Michelson interferometer.

FIG. 3 is a diagram showing how an elastic wave propagates when a measurement surface of an object to be measured is not flat.

FIG. 4 is a schematic configuration diagram showing a third embodiment of the present invention.

FIG. 5 is a schematic configuration diagram showing a fourth embodiment of the present invention.

FIG. 6 is a schematic configuration diagram showing a fifth embodiment of the present invention.

FIG. 7 is a principle diagram of a Fabry-Perot interferometer.

FIG. 8 is a diagram showing a signal intensity obtained by a Fabry-Perot interferometer.

FIG. 9 is a diagram showing a conceptual diagram in the case where displacements due to elastic waves in a large range are measured by connecting a plurality of captured images.

FIG. 10 is a diagram showing a conventional example of observing a displacement due to an elastic wave by detecting diffracted light due to the elastic wave.

FIG. 11 is a diagram showing a conventional example of observing elastic waves with an optical fiber ring interferometer.

FIG. 12 is a diagram showing another example of a conventional system for observing elastic waves.

[Explanation of symbols]

11 Light Source for Emitting Pulses 12 Object to be Measured (Piezoelectric Body) 13 Reference Surface of Interferometer 131 Driving Device for Moving Reference Surface 14 Image Input Means (CCD) 15, 15 'Beam Splitter (Half Mirror) 151, 151' Beam Splitter ( Half mirror) Moving driving means 16 Collimator lens 17 Oscillator for exciting piezoelectric body 18 Pulse generator 19 Frame memory 20 Image display means (CRT) 21 Imaging lens 61, 61 'Light rays are incident vertically on the measurement surface or half mirror. Lens 93 for combing electrode 94,95,96 image data 91,92 overlapping portion of image data 101 object to be measured 102 light source (laser) 103 photodetector 104 slit 105 movable stage 107 oscillator 108 mixer 109 pulse generator 110 lock In Amp 111 X Y recorder 112, 112 'Directional coupler 113 Delay loop 114 Optical path 115 Condenser lens 116 Light receiving element 120 Object to be measured 121 Ultrasonic diffraction cell 122 Hologram creating optical system 123 Elastic wave propagation pattern reproducing optical system L1 to L5 Lens S1 to S3 Slit hrg Photosensitive plate or hologram

Claims (11)

[Claims] 1. In a device for applying a periodic electric signal to a piezoelectric body and optically measuring the surface displacement of mechanical vibration excited by the signal, a light source is synchronized with the electric signal input to the piezoelectric body. A device for measuring minute periodic vibration displacement, characterized in that surface displacement is captured as still image data by instantaneously emitting light. 2. Image data when the periodic light emission of the light source has a certain phase difference θ with an electric signal input to the piezoelectric body, and the periodic light emission of the light source is input to the piezoelectric body. The minute periodic vibration displacement measuring device according to claim 1, wherein the electric signal and the image data having a phase difference θ + 180 ° are subtracted from each other. 3. In a device for applying a periodic electric signal to a piezoelectric body and optically measuring the surface displacement of mechanical vibration excited by the signal, the period of the electric signal inputted to the piezoelectric body and the light emission of a light source. The period is slightly different, and the surface displacement of the piezoelectric body is measured as a beat signal based on the difference between the period of the electric signal input to the piezoelectric body and the light source emission period. measuring device. 4. The minute periodic vibration displacement according to claim 1, wherein the optical system of the means for measuring the surface displacement of the mechanical vibration comprises a Michelson interferometer. Measuring device. 5. The minute periodic vibration displacement according to claim 1, wherein the optical system of the means for measuring the surface displacement of the mechanical vibration comprises a Fizeau interferometer. measuring device. 6. The micro periodic vibration displacement according to claim 1, wherein the optical system of the means for measuring the surface displacement of the mechanical vibration comprises a Fabry-Perot interferometer. Measuring device. 7. The measuring device for minute periodic vibration displacement according to claim 4, wherein the optical system has means for executing a fringe scanning method for interference fringes. 8. The optical system has means for controlling movement of the piezoelectric body, and means for joining and synthesizing image data of a plurality of obtained interference fringes. 5. A measuring device for minute periodic vibration displacement according to any one of 1. 9. The electric signal input to the piezoelectric body is a burst signal, and is controlled so that the light source does not emit light in a time period when the electric signal is not input to the piezoelectric body, or in the same time zone. 9. The shutter of the image input means is controlled so as to be closed.
5. A measuring device for minute periodic vibration displacement according to any one of 1. 10. The measuring device for minute periodic vibration displacement according to claim 1, wherein the light source is a semiconductor laser. 11. The measuring device for minute periodic vibration displacement according to claim 10, wherein the semiconductor laser is a multi-quantum well semiconductor laser.