Vibration analysis system

Abstract

To provide a vibration analysis system capable of performing measurement with high time resolution.SOLUTION: A vibration analysis system; irradiates a sample with pulsed light; using an interference microscope or a differential interference microscope capable of measuring a protrusion shape and a depression shape on a sample surface in a predetermined measurement range, applies a drive voltage for generating mechanical vibration to the sample in predetermined control; sets a frequency of the pulsed light to a drive frequency of the sample; sets an irradiation period so that time during which the sample is irradiated with the pulsed light becomes a predetermined length; irradiates the sample with the pulsed light during the irradiation period; and captures a microscope image of the sample surface irradiated with the pulsed light by a camera.SELECTED DRAWING: Figure 4

Description

[Technical field]

[0001] The present disclosure relates to a vibration analysis system. [Background technology]

[0002] There are technologies for analyzing vibrations of micro-vibration devices such as MEMS (Micro Electro Mechanical Systems) devices. The overall length of a MEMS device is measured in millimeters (mm), and its components are measured in micrometers (μm). Therefore, the scale of vibration analysis of such MEMS devices is on the nanometer (nm) level, or even smaller.

[0003] Two main methods have been used to analyze the vibration of MEMS devices. One is a method using a laser Doppler vibrometer based on the optical Doppler effect. This method can achieve highly sensitive vibration measurement, but it is limited to measuring one point at a time, making two-dimensional vibration analysis difficult.

[0004] The other method is to use a dual-beam interference microscope such as a Michelson interferometer. Several techniques for two-dimensional vibration analysis of MEMS devices using this method have been proposed and put to practical use (see Patent Document 1 and Non-Patent Documents 1-4). The following are common features of these methods. The first common feature is that an interference microscope is used to measure the surface shape of the MEMS device, and the two-dimensional height of the MEMS device surface is measured by the interference between a reference light and a measurement light. The second common feature is that a pulsed light source phase-locked with the vibration of the MEMS device is used to irradiate the elements of the MEMS device, and the vibration shape is analyzed by sampling the high-speed vibration. [Prior art documents] [Patent documents]

[0005] [Patent Document 1] Special Publication No. 2016-501373 [Non-patent literature]

[0006] [Non-Patent Document 1] A. Bosseboeuf, et al., presented at the Microsystems Metrology and Inspection, 1999. [Non-Patent Document 2] J. Reed, et al., Journal of Microelectromechanical Systems 16, 668 (2007). [Non-Patent Document 3] I. Shavrin, et al., Opt. Express 21, 16901 (2013). [Non-Patent Document 4] I. Mirai and Y. Zhang, Opt. Express 30, 26072-26081 (2022). Summary of the Invention [Problem to be solved by the invention]

[0007] However, previous technologies for two-dimensional vibration analysis of MEMS devices using conventional interference microscopes had the problem that they had low measurement time resolution and were usually only able to observe the steady state of vibration, making it impossible to observe high-speed vibration fluctuations.

[0008] An object of the present disclosure is to provide a vibration analysis system capable of performing measurements with high time resolution. [Means for solving the problem]

[0009] The vibration analysis system disclosed herein is configured to irradiate a sample with pulsed light, and use an interference microscope or a differential interference microscope capable of measuring the shapes of protrusions and depressions on the sample surface within a predetermined measurement range, apply a drive voltage that generates mechanical vibrations in the sample under predetermined control, set the frequency of the pulsed light to the drive frequency of the sample, set an irradiation period such that the time during which the pulsed light is irradiated onto the sample is a predetermined length, irradiate the sample with the pulsed light during the irradiation period, and capture a microscopic image of the sample surface irradiated with the pulsed light with a camera. Effect of the Invention

[0010] According to the present disclosure, measurements can be made with high time resolution. [Brief description of the drawings]

[0011] [Figure 1] FIG. 1 is a diagram showing the basic configuration of a vibration analysis device using a differential interference microscope. [Diagram 2] FIG. 2 is a graph illustrating high-speed vibration caused by a pulsed light source in a conventional vibration analysis device. [Diagram 3] FIG. 3 shows a microscope image (differential interference contrast image) and a graph of light intensity. [Figure 4] FIG. 4 is a diagram showing the configuration of a vibration analysis system according to this embodiment. [Diagram 5] FIG. 5 is a diagram for explaining the principle of the discrete strobe method. [Figure 6] FIG. 6 is a diagram for explaining the principle of the discrete strobe method. [Figure 7] FIG. 7 is a block diagram showing a hardware configuration of the control unit. [Figure 8] FIG. 8 shows an example of the flow of processing of a measurement program executed in the control unit. [Figure 9] FIG. 9 shows an example of a moving image of the transient change information obtained as a measurement result in the first experiment. [Figure 10]FIG. 10 is a diagram showing vibration amplitude obtained by graphing information on vibration operation and light intensity change due to ON / OFF operation of a theoretical MEMS device. [Figure 11] FIG. 11 is a schematic diagram of the second experimental cycle. [Figure 12] FIG. 12 shows an example of a moving image of the transient change information obtained as a measurement result in the second experiment. [Figure 13] FIG. 13 is a diagram showing vibration amplitude obtained by graphing information on changes in light intensity. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0012] Hereinafter, embodiments of the present disclosure will be described in detail with reference to the drawings.

[0013] As mentioned above, the conventional strobe vibration analysis method can only observe the steady state of vibration, and therefore cannot observe fast fluctuations such as transient changes in the vibration state.

[0014] First, the basic configuration of an interference microscope will be described using a differential interference microscope as an example. The vibration analysis method of this embodiment can be used not only for differential interference microscopes but also for interference microscopes in general. FIG. 1 shows the basic configuration of a vibration analysis device using a differential interference microscope. The vibration analysis device includes a differential interference microscope (Ma2), a camera (Mb), a light source (Mc), and a MEMS device (Md). A pulsed light is split into two beams using a differential interference prism (ma5) and irradiated onto a sample. A small deviation in the lateral direction between the two beams is called a shear amount. The shear amount is determined by the differential interference prism and the objective lens. For example, when a differential interference prism U-DICR manufactured by Olympus and an objective lens LMPlanFL10x are combined, the shear amount is approximately 2.5 μm. When there is a difference in the optical path in this way, the intensity of the light is modulated and appears as an interference fringe. When an interference microscope is used without using a differential interference microscope, the pulsed light is irradiated onto the sample, assuming that there is no configuration related to the splitting portion.

[0015] FIG. 2 shows a graph for explaining high-speed vibration caused by a pulsed light source in a conventional vibration analysis device. In FIG. 2(a), θ indicates a phase difference. FIG. 2(b) shows a change in light intensity caused by vibration. When the vibration of the MEMS device 20 deviates from the equilibrium position, the shape of the surface of the MEMS device changes, and the light intensity obtained by the differential interference microscope is modulated. By irradiating such modulated pulsed light, a microscope image can be captured at a specific phase of the vibration of the MEMS device. In addition, by modulating the phase of the irradiated pulsed light, the entire vibration can be measured. In a conventional vibration analysis device, as shown in FIG. 2(a), a pulsed light synchronized with the vibration frequency of the MEMS device is irradiated. The vibration analysis device realizes vibration analysis and measurement of the MEMS device by modulating the phase of the irradiated pulsed light and taking an image with a camera at each phase. In addition, at least three phases (0°, 120°, 240°, etc.) must be used during one vibration cycle of the MEMS device to take an image.

[0016] In conventional strobe vibration analysis methods, the time resolution depends on the frame rate of the camera. If the number of phase points measured during one period is N, the time resolution is given by equation (1).

number

[0017] In the conventional device, a camera with a frame rate of 30 fps was used to measure the phase at three points, so the time resolution according to equation (1) is 0.1 seconds. However, in actual measurements, it is necessary to average multiple frames at each phase point to improve the signal-to-noise ratio. Therefore, the conventional strobe vibration analysis method requires a very long measurement time of about 30 seconds, so only the steady state of vibration can be observed. However, in the research and development of MEMS devices, it is important to observe dynamic fluctuations in the vibration state. For example, when a signal such as light is input to a MEMS sensor, a signal due to a sudden change in the vibration state is detected at high speed. Observing such changes in the vibration state is an essential process for confirming the principle of the element and for investigating the cause of abnormal operation.

[0018] FIG. 3 shows a microscope image (differential interference contrast image) and a graph of light intensity. The image (a) in FIG. 3 is a microscope image of the MEMS device and a measurement point (a1) of vibration, and the light intensity at (a1) is measured. The graph (b) in FIG. 3 is a graph showing the phase displacement at the measurement point (a1). In the graph (b) in FIG. 3, the phase changes from 0° to 1080°, which shows that the light intensity changes periodically due to the vibration of the MEMS device 20.

[0019] The principle of high-speed vibration measurement using a pulsed light source is shown in Figures 2 and 3. As shown in Figure 2(a), a pulse-modulated LED or LD light source irradiates pulsed light that is phase-locked with the excitation signal of the MEMS device. Since the vibration of the MEMS device 20 has the same frequency as the excitation signal (drive signal), the pulsed light is also synchronized with the vibration of the MEMS device, and the phase difference between them can be modulated. The phase difference is referred to as θ in Figure 2(a).

[0020] The above is the basic principle of the vibration analysis device. Based on the above vibration analysis device, in this embodiment, a "discrete strobe vibration analysis method" is used to visualize dynamic fluctuations in vibration caused by input signals and environmental disturbances. In order to improve time resolution, high-speed resolution can be achieved by further pulse-modulating the pulsed light incident during measurement to make it a discrete pulsed strobe light. Fast fluctuations such as transient changes in the vibration state of a MEMS device can be observed.

[0021] Next, the configuration of the vibration analysis system of this embodiment will be described.

[0022] The configuration of the vibration analysis system of this embodiment is shown in Fig. 4. As shown in Fig. 4, the vibration analysis system 1 is composed of a differential interference microscope 10, a digital camera 12, a light source 14 (a pulse-modulated LED or LD light source), a plurality of function generators 16 (16A, 16B), a circuit 17, and a control unit 18. In this configuration, the vibration analysis system 1 observes a MEMS device 20, which is a sample to be observed. The vibration analysis system 1 is configured to function as the vibration analysis device of the present disclosure by including each component.

[0023] In the conventional strobe method, a light source blinks at the same or a similar frequency as the periodic motion of the object being observed (basic strobe light), making it possible to observe objects that undergo periodic motion at high speed. However, this method can only observe stationary periodic motion, and cannot observe high-speed fluctuations in motion. In this embodiment, this problem is solved by using discrete pulse strobe light (hereinafter abbreviated as discrete strobe light), which is obtained by further pulse-modulating the basic strobe light.

[0024] Each functional unit of the vibration analysis system 1 functions as follows. (1) The differential interference microscope 10 visualizes information on the surface of the MEMS device at the nm scale. (2) The modulated light source 14 (pulsed LED / LD) illuminates with a period synchronized with the drive signal and disturbance signal of the MEMS device 20, samples the high-speed vibration, and visualizes the dynamic fluctuation of the vibration with high time resolution. (3) The function generator 16 supplies a phase-synchronized drive voltage to the light source 14 and the MEMS device 20, and phase-synchronizes the drive voltage of the light source 14 with the disturbance signal. (4) The control unit 18 is, for example, a computer, includes software and programs for analysis, and calculates the amplitude of the MEMS device 20 and the mode shape of the vibration with high time resolution by controlling the measurement process. Each functional unit will be described below.

[0025] The differential interference microscope 10 includes a beam splitter 10a, a polarizing plate 10b, a differential interference prism 10c, and an objective lens 10d. The beam splitter 10a is installed so as to direct the pulsed light (Pu) incident from a lens (not shown) toward the MEMS device 20. The polarizing plate 10b converts the pulsed light (Pu) into polarized light. The differential interference prism 10c splits the pulsed light (Pu1) incident through the polarizing plate 10b into two lights (Pu2). In the following description, when the light before and after splitting are to be distinguished, the pulsed light before splitting is referred to as (Pu1), and the two lights after splitting are referred to as (Pu2), and when no distinction is made, the light is simply referred to as (Pu). The objective lens 10d irradiates the two split lights (Pu2) onto the MEMS device. The configuration of the differential interference microscope 10 is not limited to this, and may be appropriately configured according to the design of the microscope. The differential interference microscope 10 may be configured to irradiate the MEMS device 20 with pulsed light (Pu2) branched through a differential interference prism (10c) and measure the unevenness (protrusion and depression shapes) on the surface of the MEMS device 20. The measurement range of the unevenness is usually from 1 nm to several thousand nm, preferably from 1 nm to 1000 nm. The parameter that determines the measurement range of the unevenness is the differential displacement caused by the unevenness, and the parameter of the differential displacement caused by the unevenness is approximately 0.05 nm to 60 nm.

[0026] The differential interference microscope 10 expresses minute displacements caused by vibration of the MEMS device as changes in light intensity by the interference of two light beams that are laterally misaligned. When there is displacement on the device surface due to vibration, an optical path difference occurs between the two light beams, and the light intensity is modulated, appearing as interference fringes. Figure 3(a) is a differential interference image of a MEMS device 20 when it is operating. The change in light intensity in the beam part in the center of the image indicates that the MEMS device 20 is deforming due to vibration. A differential interference microscope has the advantage that it allows observations without being affected by environmental noise or tilt when the measurement sample is installed.

[0027] The digital camera 12 is attached to the differential interference microscope 10 and captures a microscopic image of the MEMS device 20 through the differential interference microscope 10. Any camera may be used as the digital camera 12 as long as it is a color or monochrome CMOS or CCD camera. The digital camera 12 is an example of an optical system for capturing a microscopic image of a sample of the present disclosure. Here, in the conventional method of sampling high-speed vibration, the digital camera 12 used in the interference vibration analysis device has a frame rate of about several tens of Hz, which is much slower than the frequency band (several tens of kHz to several tens of MHz) in which the MEMS device 20 can vibrate.

[0028] The light source 14 uses a pulse-modulated LED or laser light source that (1) samples high-speed vibrations and (2) achieves high time resolution in vibration state measurement.

[0029] In order to realize the above-mentioned discrete strobe, the function generator 16 uses two function generators (FG), FG16A and FG16B. The FG16A outputs (applies) two synchronized voltage signals, one voltage signal (vs1) is used to drive the MEMS device, and the other voltage signal (vs2a) is used to modulate the pulsed light of the light source 14. The voltage signal (vs1) applies a drive voltage that generates mechanical vibration to the MEMS device. Therefore, the FG16A needs to be able to output voltage signals of at least two channels. In this embodiment, a device capable of outputting arbitrary signals of 25 MHz on two channels is used for the FG16A. If a higher-level device is used, a signal output of 240 MHz is also possible.

[0030] In FG16B, one channel is a strobe pulse window signal (vs2b). In addition, in the measurement of this embodiment, in order to measure the transient response of the MEMS device 20, another channel is a disturbance signal (vs2h) for varying the vibration state of the MEMS device. For example, when observing the transient response of the vibration state at the moment when heat is applied to the MEMS device, that signal is used as a heating signal. A voltage signal (vs2c) is input to the light source 14 by combining the voltage signal (vs2a) and the voltage signal (vs2b).

[0031] Figures 5 and 6 are diagrams for explaining the principle of the discrete strobe method. Figure 5 shows the measurement principle with high time resolution using a discrete strobe light source. A pulse light (basic strobe) synchronized with the vibration frequency of the MEMS is switched by multiplying it with a strobe pulse window synchronized with the transient response to be observed, to create a discrete strobe. In other words, a periodic vibration synchronized with the basic strobe pulse is generated, and high-speed changes in the vibration state (transient response, etc.) are observed by discrete strobe lighting. The time resolution of the discrete strobe vibration analysis method is determined by the formula: "Time resolution (seconds) = strobe pulse window width."

[0032] Each graph in Fig. 5 shows the amplitude intensity, where (a1) is the driving voltage of the MEMS device, (b1) is the basic pulse light, (b2) is the pulse modulation function, and (b3) is the pulse-modulated discrete strobe. (sw) is the pulse window set by the pulse modulation function. The pulse window (sw) is a window with a time resolution level of milliseconds to microseconds. The phase θ 1 (Modulation phase θ 1 ) is set, and the phase θ 2 (Modulation phase θ 2) is set. The high-speed modulation of the basic pulse is synchronized with or approximates the frequency of the vibration of the sample. The "medium-speed" modulation of the pulse modulation is synchronized with or approximates the frequency of the expected fluctuation of the vibration state of the sample. For the basic pulse light and pulse modulation function, the voltage signal (vs2a) and the voltage signal (vs2b) are input to the circuit 17, and the voltage signal (vs2c) that is the result of the integration is input to the light source 14, so that the pulse-modulated discrete strobe light is irradiated. The irradiation of the light source 14 and the period of the driving voltage of the MEMS device 20 are synchronized by the setting of the control unit 18. The discrete strobe is irradiated periodically from the light source 14 to the differential interference microscope 10. In FIG. 6, the upper graph shows the illumination intensity of the discrete strobe in milliseconds, and the lower graph shows the illumination intensity expanded to a part of the pulse window of the discrete strobe. When one pulse window is expanded, multiple pulse lights exist in one pulse window.

[0033] The control unit 18 is a computer that executes various controls related to the vibration analysis system 1. The control unit 18 executes controls related to the imaging and capture of microscopic images by the digital camera 12, the output of voltage signals by the function generator 16, the calculation of resonance amplitude from the captured images, and the calculation related to high time resolution of vibration shapes.

[0034] The control unit 18 executes various controls related to the measurement by executing the measurement program. The operations executed by the control unit 18 will be described in the flowchart below. The control unit 18 first sets the drive voltage, drive frequency, and drive frequency of the pulsed light of the MEMS device 20 output by the FG 16A to the resonance frequency of the MEMS device 20. The control unit 18 also sets the pulses for producing the discrete strobe output by the FG 16B. The control unit 18 sets the phase of the discrete strobe light, modulates the phase of the pulsed light therein, and captures a resonance image with a camera. The control unit 18 then calculates the vibration amplitude with high time resolution using the image. The drive frequency is not necessarily limited to the resonance frequency, and may be different depending on the object of measurement.

[0035] Fig. 7 is a block diagram showing a hardware configuration of the control unit 18. As shown in Fig. 7, the control unit 18 has a CPU (Central Processing Unit) 111, a ROM (Read Only Memory) 112, a RAM (Random Access Memory) 13, a storage 114, an input unit 115, a display interface (I / F) 116, and a communication interface (I / F) 117. Each component is connected to each other via a bus 119 so as to be able to communicate with each other.

[0036] The CPU 111 is a central processing unit, and executes various programs and controls each part. That is, the CPU 11 reads out a program from the ROM 112 or 1114, and executes the program using the RAM 13 as a working area. The CPU 111 performs various arithmetic processing related to the above control according to the program stored in the ROM 12 or the storage 114. In this embodiment, the program is stored in the ROM 112 or the storage 114.

[0037] The ROM 112 stores various programs and various data. The RAM 113 temporarily stores programs or data as a working area. The storage 114 is configured with a storage device such as a hard disk drive (HDD) or a solid state drive (SSD), and stores various programs including an operating system, and various data.

[0038] The input unit 115 includes a pointing device such as a mouse, and a keyboard, and is used for performing various inputs. The display interface 116 is, for example, a liquid crystal display, and displays various information. The display interface 116 may employ a touch panel system and function as the input unit 115. The communication interface 117 is an interface for communicating with other devices such as terminals, and uses standards such as Ethernet (registered trademark), FDDI, and Wi-Fi (registered trademark).

[0039] FIG. 8 shows an example of the flow of processing of a measurement program executed in the control unit 18.

[0040] In step S100, the CPU 111 sets the frequency and voltage of an AC signal (hereinafter, referred to as a drive signal) for driving the MEMS device 20. The voltage of the drive signal is set according to the amplitude required by the MEMS device 20.

[0041] In step S102, the CPU 111 sets the frequency of a signal (hereinafter, referred to as the modulation signal) for exciting a variation in the vibration state of the MEMS device 20, and sets the voltage of the signal. Here, a fixed time for which the modulation signal of the present disclosure is applied is set. Also, the modulation signal is set to be applied periodically for a fixed time to periodically repeat the variation in the vibration state. For example, when investigating the transient response of the vibration state due to the variation of the input signal of the MEMS device 20, the modulation signal is used as a modulation function of the vibration drive signal set in the above-mentioned step S100. When investigating the transient response of the vibration state due to heating, the modulation signal is used to heat the MEMS device 20.

[0042] In step S104, the CPU 111 sets the frequency and pulse width of the fundamental pulse light. Note that the frequency of the fundamental pulse light is set to correspond to the drive frequency of the MEMS device 20, and the pulse width is set to, for example, Δt=30 ns corresponding to a measurable frequency band.

[0043] In step S106, the CPU 111 sets a pulse modulation frequency and a pulse width according to a pulse modulation function. This pulse width corresponds to a pulse window (sw) and is set to, for example, 2 ms.

[0044] In step S108, the CPU 111 calculates the modulation phase θ of the pulsed light modulated in step S106. 2 (Hereafter, we will abbreviate the phase θ 2 (also written as modulation phase) 2By setting the above, the irradiation period is set so that the time during which the pulsed light is irradiated to the MEMS device 20 is a predetermined length. In addition, the irradiation period is set to the time difference between the modulation signal set in step S102 and the periodic fluctuation of the vibration state excited by the modulation signal.

[0045] In step S110, the CPU 111 calculates the modulation phase θ 1 (Hereafter, we will abbreviate the phase θ 1 By setting the modulation phase θ1, the irradiation period during which the basic strobe light is irradiated onto the MEMS device 20 is set to be the time difference between the drive signal set in step S102 and the periodic vibration excited by the drive signal.

[0046] In step S112, the CPU 111 controls the light source 14 to irradiate pulsed light at the set phase for a predetermined irradiation period.

[0047] In step S114, the CPU 111 obtains an image (microscope image) of the surface of the MEMS device 20.

[0048] In step S116, the CPU 111 calculates the modulation phase θ 1 If the phases in a predetermined range have been processed, the process proceeds to step S114, and if not, the process returns to step S110 to set the next phase.

[0049] In step S118, the CPU 111 calculates the vibration displacement distribution from the surface image (microscope image).

[0050] In step S120, the CPU 111 calculates the modulation phase θ 2 If the phase has been processed, the process proceeds to step S122. If the phase has not been processed, the process returns to step S108 and the next phase is set. By repeating the above, the period of the pulse window (sw) during a certain time period changes with each repetition. Also, by repeating the above, the phase θ 2By setting the period of the pulse window (sw) to move, the period of the pulse window (sw) changes with each repetition. Note that the period of the pulse window (sw) may be set to change continuously with each repetition.

[0051] In step S122, the CPU 111 acquires transient change information on the vibration state fluctuation of the MEMS device 20. An example of the transient change information will be described later.

[0052] As described above, the vibration analysis system 1 of this embodiment can perform measurements with high time resolution.

[0053] Next, two experimental examples of this embodiment will be described.

[0054] In the first experiment, a time-resolved measurement was performed on the start and stop process of the MEMS device. The drive of the MEMS device 20 was periodically turned on and off by the function generator 16, and the time-resolved vibration shape at that time was measured.

[0055] Figure 9 shows an example of a moving image of the transient change information obtained as a measurement result in the first experiment. The image is extracted to visualize the change in the transient state with a time resolution of 2 ms. The size in the image is also shown on a scale of 30 μm. The time changes are shown for t=00 ms, t=06 ms, t=10 ms, and t=16 ms, respectively. Figure 10(a) shows the vibration operation due to the theoretical ON / OFF operation of a MEMS device. Figure 10(b) shows the vibration amplitude, which is a graph of the information on the change in light intensity. In this measurement, the width of the strobe pulse window shown in Figure 5 is 2 ms, so a time resolution of 2 ms is achieved. This is an improvement of nearly 50 times over the resolution of at least 0.1 seconds in the conventional method. It is shown that not only the conventional steady-state measurement, but also transient measurement is possible. It can be seen that the high time resolution makes it possible to measure high-speed vibrations that match the vibration of the MEMS device. Theoretically, the frequency of the discrete strobe light can be measured even if it is the same as the driving frequency of the MEMS device. In addition, by adjusting the optical system (improving the brightness of the irradiated light and ensuring the exposure time), it is possible to improve the resolution to the microsecond level.

[0056] In the second experiment, we performed time-resolved observation of the change in the MEMS vibration state due to heating. Since the observed MEMS device is a high-sensitivity, high-speed thermal sensor, observation of the transient response to the thermal signal is important for confirming the principle of the device and for failure analysis. Figure 11 is a schematic diagram of the period of the second experiment. With the MEMS device continuously driven, a periodic heating signal (a2) as shown in Figure 11 was input to the MEMS device. Figure 12 is an example of an image of the transient change information obtained as a measurement result in the second experiment as a moving image. The time changes at t=00.0 ms, t=03.3 ms, t=04.4 ms, and t=06.7 ms are shown, respectively. The change in light intensity indicates the increase or decrease in the vibration amplitude due to heating. The vibration amplitude, which is a graph of the information on the change in light intensity from Figure 12, is shown in Figure 13. It is known that the resonance frequency of a MEMS device shifts when heated, causing the vibration amplitude to fluctuate. In this measurement, it can be confirmed that the change in the MEMS vibration state due to heating can be calculated with high time resolution.

[0057] The present disclosure is not limited to the above-described embodiment, and various modifications and applications are possible without departing from the spirit and scope of the present invention. [Explanation of symbols]

[0058] 1. Vibration analysis system 10 Differential interference contrast microscope 12. Digital Camera 14 Light source 16(16A, 16B) Function Generator 18 Control Unit 20 MEMS Devices

Claims

1. Using an interference microscope or a differential interference microscope that can irradiate a sample with pulsed light and measure the protrusion and depression shapes of the sample surface within a predetermined measurement range, In the predetermined control, applying a driving voltage to the sample to generate mechanical vibration; setting the frequency of the pulsed light to a driving frequency of the sample; setting an irradiation period so that the time during which the pulsed light is irradiated onto the sample is a predetermined length; irradiating the sample with the pulsed light for the irradiation period; taking a microscopic image of the sample surface irradiated with the pulsed light with a camera; Vibration analysis system.

2. The driving voltage is periodically applied to the sample for a certain period of time to periodically repeat mechanical vibration; The vibration analysis system according to claim 1 , wherein the irradiation period is set to a predetermined period during the fixed time during which the drive voltage is applied.

3. The vibration analysis system of claim 2 , wherein the predetermined period of time varies with each repetition.

4. The vibration analysis system according to claim 2 , wherein the predetermined period of time changes continuously for each repetition.

5. 3. The vibration analysis system according to claim 2, wherein a first modulation phase of the fundamental pulsed light corresponding to a drive signal for the sample and a second modulation phase corresponding to a modulation signal for exciting fluctuations in the vibration state of the sample are set so that a predetermined fundamental pulsed light is pulse-modulated for the pulsed light irradiated during the fixed time period.

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