JP2005283160A - Vibration analysis device and method - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a vibration analysis device and a vibration analysis method with frequency analysis function capable of direct digitization and frequency analysis of a sound signal. <P>SOLUTION: The system comprises: a vibration plate 21 for mechanical vibration; a modulated light irradiation means 1 for irradiating the vibration plate 21 with the light, the intensity of which is modulated with sinusoidal waves; and a demodulation means 2 for frequency analysis of the vibration by detecting the light via the vibration plate 21, and demodulates the repetitive signal as the synchronous signal. The modulated light irradiation means 1 includes the light source 43 for light irradiation and the modulator 42 for modulating the output of the light source 43 for the vibration plate 21 so as to periodically vary the light intensity. The demodulation means 2 includes the light detector 31 for detecting the light via the vibration plate 21, and converting into an electric signal, the amplifier 32 for amplifying the electric signal, and the demodulator 33 for demodulating the amplified electric signal amplified by the amplifier 32 with the frequency of a sine wave, and for frequency analysis of the mechanical vibration by obtaining the amplitude and phase information of the vibration of the vibration plate 21. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to a high-performance and small-sized microphone used in speech recognition and the like, and more particularly to a vibration analysis apparatus and a vibration analysis method using a micro electro mechanical system (MEMS) technique.

 Feature extraction by speech analysis is an important technique for improving speech recognition rate. For example, in a microphone, a sound wave incident on a diaphragm is converted into an electric signal, and a sound frequency of 150 Hz to 8 kHz is filtered by a filter, and then digitized at a sampling rate of about 22 kHz by an A / D converter. Thereafter, spectrum analysis is performed using the power spectrum obtained by FFT (Fast Fourier Transform). Therefore, in order to perform accurate voice analysis, a high-resolution A / D converter and a high-performance FFT device are required, but at present, it is difficult to obtain a device that sufficiently satisfies these requirements.

 On the other hand, there are various types of microphones that convert acoustic signals into electrical signals. Optical microphones obtain vibration displacement by irradiating light waves on the microphone diaphragm and detecting the intensity of the reflected light. The sensitivity can be set independently from the diaphragm. Proposed an optical microphone device that simplifies the circuit configuration associated with time division multiplexing when using multiple microphones using an optical microphone, and simplifies and simplifies the modulation circuit when used as a wireless microphone. (See Patent Document 1).

In the optical microphone device described in Patent Document 1, a diaphragm that vibrates in response to a sound wave, a light emitting element that emits radiated light to the diaphragm, and a light receiving element that receives the radiated light reflected by the diaphragm And a driving circuit that applies a driving current for driving the light emitting element to the light emitting element. The driving circuit supplies a pulse current having a predetermined repetition frequency as the driving current. I have to.
JP 2000-287286 A

  However, in the optical microphone device described in Patent Document 1, a predetermined repetition frequency is set as the sampling frequency of the audio signal. That is, as described above, in order to digitally process an audio signal, the sound pressure and time must be digitized, which requires quantization and sampling. In addition, in order to perform frequency analysis, it is necessary to perform FFT, and this requires a calculation amount of N × log N, where N is sampling.

 The present invention has been made in view of the above circumstances, and its object is to provide a vibration analysis apparatus and a vibration analysis method having a frequency analysis function capable of directly digitizing an acoustic signal and analyzing the frequency. The purpose is to do.

  In order to achieve the above object, the first feature of the present invention is that (a) a diaphragm that vibrates due to mechanical vibration, and (b) the diaphragm is driven by a repetitive signal and the intensity is periodic. And (d) a demodulating means for detecting the light passing through the diaphragm and demodulating it using a repetitive signal, thereby analyzing the frequency of the mechanical vibration. The gist is that it is a vibration analyzer.

  The second feature of the present invention is that (a) a vibration plate that vibrates due to mechanical vibration is driven by a repetitive signal to irradiate light whose intensity changes periodically; And a step of analyzing the frequency of mechanical vibration by detecting light passing through and demodulating using a repetitive signal.

  According to the present invention, it is possible to provide a vibration analysis apparatus and a vibration analysis method that can be directly digitized and frequency-analyzed.

  First to third embodiments of the present invention will be described below with reference to the drawings. In the following description of the drawings, the same or similar parts are denoted by the same or similar reference numerals. However, it should be noted that the drawings are schematic, and the relationship between the thickness and the planar dimensions, the ratio of the thickness of each layer, and the like are different from the actual ones. Therefore, specific thicknesses and dimensions should be determined in consideration of the following description. Moreover, it is a matter of course that portions having different dimensional relationships and ratios are included between the drawings. Further, the following embodiments exemplify apparatuses and methods for embodying the technical idea of the present invention, and the technical idea of the present invention is the material, shape, structure, The layout is not specified as follows. The technical idea of the present invention can be variously modified within the scope of the claims.

(First embodiment)
As shown in FIG. 1, the vibration analyzing apparatus according to the first embodiment of the present invention has a vibration plate 21 that vibrates due to mechanical vibration, and the vibration plate 21 is driven by a repetitive signal and has a strength. The frequency of mechanical vibration is analyzed by detecting the modulated light irradiation means 1 that irradiates periodically changing light and the light that has passed through the diaphragm 21 and demodulating the periodic repetitive signal as a synchronization signal. Demodulation means 2. The “repetitive signal” is not limited to a triangular wave or a rectangular wave, but any waveform may be used to indicate a cyclic change periodically. Here, for simplicity, the intensity x _in (t) is expressed as follows ( The case of changing with a sine wave as shown in equation (1) will be described.

That is, in the vibration analyzing apparatus according to the first embodiment, the light that has passed through the diaphragm 21 and the modulated light irradiating means 1 that irradiates light that changes in a sine wave as represented by the following equation (1): And a demodulating means 2 for performing frequency analysis of mechanical vibration by demodulating (synchronizing detection) using the same sine wave as that of the equation (1) as a synchronizing signal:
x _in (t) = sin (ω _0A t + φ) (1)
The modulated light irradiating means 1 modulates the output of the light source 43 so that the intensity of light x _in (t) varies with the sine wave of the equation (1), and the light source 43 that irradiates the diaphragm 21 with light. Instrument 42. If the light source 43 is a semiconductor light emitting element such as a semiconductor laser or a light emitting diode (LED), the modulator 42 may modulate the drive current of these semiconductor light emitting elements with a sine wave of the formula (1).

The demodulator 2 detects a light passing through the diaphragm 21 and converts it into an electric signal, an amplifier 32 that amplifies the electric signal, and an electric signal amplified by the amplifier 32 (1). And a demodulator 33 which obtains amplitude and phase information of the vibration of the diaphragm 21 and analyzes the frequency of mechanical vibration. The modulator 42 and the demodulator 33 are connected to a transmitter 41 that supplies a sine wave signal having a frequency ω _0A as a synchronization signal. The amplifier 32 and the demodulator 33 may be combined to form a lock-in amplifier to detect synchronization.

In the conventional optical microphone, in order to optically measure the vibration displacement, light having a certain intensity is incident on the diaphragm. However, in the vibration analysis apparatus according to the embodiment of the present invention, the expression (1) The light whose intensity of the sine wave having the frequency ω ₀ changes as shown in FIG. For this reason, since the reflected light from the diaphragm 21 does not include anything other than the fundamental frequency ω _0A = 2πf _0A and its harmonic components, it is possible to easily analyze the vibration frequency of the diaphragm 21. As shown in FIG. 1, the fundamental frequency ω _0A can be adjusted to the resonance frequency f ₀ of the diaphragm 21 by applying a part of the output to the input side. Furthermore, by applying a part of the output to the input side, sensitivity adjustment, dynamic range expansion, SN ratio improvement, and the like can be performed.

Furthermore, the frequency of the input sound wave can be detected by synchronizing detection using a plurality of sine waves having different frequencies ω _0A in a time-sharing manner or by sweeping the frequency ω _{0A of the} sine waves at a constant period. Can be identified. In order to generate a plurality of sine waves having different frequencies ω _0A in time division, a plurality of transmitters 41 are prepared in FIG. 1, and a control device that controls these plurality of transmitters 41 in time division is further provided. You should prepare. In the case of synchronous detection while sweeping the frequency ω _{0A of the} sine wave at a constant cycle, the transmitter 41 in FIG. 1 may be used as a sweep transmitter.

For example, it is assumed that the diaphragm 21 fluctuates due to the sound pressure of human voice. Assuming that the human vocal tract is a single acoustic tube, the resonance frequency of the acoustic tube is c and the length of the acoustic tube is l.
f _n = (2n−1) c / 4l (2)
Given in. Since the sound is considered to be composed of the fundamental frequency f ₀ and its harmonics f ₁ , f ₂ , f ₃ ,... F _n ,.

It can be expressed as. According to the sound source filter theory, the uttered output spectrum P (f) can be expressed by the product of the laryngeal sound source spectrum U (f), the vocal tract transfer function T (f), and the radiation characteristic R (f). And
P (f) = U (f) T (f) R (f) (4)
(See Ray D. Kent / Charles Reed, translated by Takayuki Arai / Takuo Sugawara, “Sound Analysis of Speech,” published by Kaibundo.) If the terms of U (f) and R (f) are constant, for example, T (f) is obtained by an analog filter or a digital filter such as a filter bank in which a plurality of filters having different characteristics are connected in parallel. Voice analysis is possible. In order to analyze the frequency of the waveform obtained in this way, conventionally, spectrum analysis is performed by performing Fourier expansion by FFT (Fast Fourier Transform). For example, it was Fourier transformed by the following formula:

This is analog processing, and in digital processing, DFT (Discrete Fourier Transform):

Or DCT (Discrete Cosine Transform):

Or, the modified MDCT (Modified Discrete Cosine Transform):

Was used for frequency analysis. In this case, if the high frequency component is not cut, an accurate spectrum cannot be obtained due to aliasing (high frequency noise accompanying discretization). In the vibration analysis apparatus according to the first embodiment of the present invention, the diaphragm 21 is irradiated with a sine wave having a frequency ω ₀ without performing complicated processing using such an FFT, and demodulated. By performing (synchronous detection), the amplitude and phase information of the diaphragm 21 for each frequency can be easily obtained with respect to the acoustic signal input.

  The diaphragm 21 of the vibration analyzing apparatus according to the first embodiment of the present invention may include a reflective diffraction grating as shown in FIG. In the vibration analysis apparatus shown in FIG. 2, the vibration plate 21 that vibrates due to sound pressure, the light source 43 that irradiates light to the diffraction grating, and the light diffracted by the diffraction grating are detected and converted into electrical signals. The photodetector 31 is shown in detail. An image sensor such as a photodiode array is preferably used for the photodetector 31 shown in FIG. That is, the photodetector 31 is preferably a photodiode array that detects the displacement of the two-dimensional diaphragm 21 by detecting a two-dimensional image of the diffraction image, instead of detecting the difference in light intensity. Therefore, the photodetector (photodiode array) 31 has a sufficiently wide area for the diffracted light so that the diffraction image can be detected without omission.

  In the vibration analysis apparatus using the vibration plate 21 including the reflection type diffraction grating, when the light irradiated from the light source 43 is incident on the vibration plate 21, the light wave emitted from the light source 43 is reflected by the diffraction grating, and light A diffraction image is produced on the surface of the detector 31. That is, the displacement of the diaphragm 21 provided with the reflection type diffraction grating is optically detected by the photodetector 31 and further converted into an electric signal.

  For this reason, the diaphragm 21 is suspended from the fixing portions 4a and 4b by the elastic connection portions 5a and 5b. Specifically, as shown in FIG. 3, the diaphragm 21 is suspended on the fixing portions 4 a and 4 b provided on the support substrate 11 via the elastic connection portions 5 a and 5 b. When viewed as a planar pattern, the fixing portions 4 a and 4 b have a frame shape surrounding the hollow portion 9 </ b> R provided on the upper surface of the support substrate 11. And the diaphragm 21 is arrange | positioned as a diaphragm-shaped lid | cover in the upper part of the hollow part 9R whose cross section as shown in FIG. 3 is boat-shaped.

  Each of the fixing portions 4a and 4b includes a buried insulating film 12, an element isolation insulating film 13, an interlayer insulating film 14, and a passivation film 15, which are sequentially deposited on a support substrate 11 made of single crystal Si. The diaphragm 21 also has a laminated structure including the buried insulating film 12, the element isolation insulating film 13, the interlayer insulating film 14, and the passivation film 15. The elastic connection portions 5 a and 5 b are constituted by a buried insulating film 12, an element isolation insulating film 13, and an interlayer insulating film 14, and polysilicon connectors 21 a and 21 b are embedded in the element isolation insulating film 13 layer.

The reflection type diffraction grating provided on the diaphragm 21 may be a two-dimensional diffraction grating shown in FIG. 4A or a one-dimensional diffraction grating shown in FIG. In FIG. 4A, a plurality of holes (recesses) H _i−1,1 ,..., H _{i, 1} , H _1,2 , H _1,3 arranged in a matrix on the diaphragm 21. ,..., H _{i + 2,6} shows an example in which a two-dimensional diffraction grating is configured. FIG. 4B shows an example in which a one-dimensional diffraction grating is constituted by a plurality of grooves G ₁ , G ₂ , G ₃ ,..., G ₆ periodically arranged on the diaphragm 21. ing.

  In the state shown in FIG. 2, when sound pressure is input to the diaphragm 21 having the diffraction grating having the structure shown in FIG. 3, the diaphragm 21 is connected to the elastic connecting portions 5a and 5b and the fixing portions 4a and 4b. Vibrates using the boundary as a fulcrum. In FIG. 2, the diffraction image before the vibration plate 21 is displaced is indicated by a thick solid line and a thick broken line. When the diaphragm 21 is stationary, that is, when there is no input by sound, it is diffracted by the light emitted from the light source 43 onto the surface of the photodetector 31 at intervals as shown by a thick solid line and a thick broken line in FIG. An image appears.

  When there is an input by sound and the distance between the diaphragm 21 and the photodetector 31 changes, the interval between the diffraction images on the surface of the photodetector 31 changes two-dimensionally as shown by thin solid lines and thin broken lines. To do. A thin solid line and a thin broken line in FIG. 2 indicate that the interval between the diffraction images has changed with the vibration of the diaphragm 21.

  In this way, in the diffraction image obtained on the photodetector 31, a difference is obtained on the photodetector 31 before and after vibration when attention is paid to a diffraction image of the same order and the same orientation. By detecting the displacement of the diffraction image on the photodetector 31, the vibration displacement of the diaphragm 21 is output.

  According to the vibration analyzing apparatus according to the first embodiment of the present invention, the reflected light from the diaphragm 21 required for the conventional optical microphone is narrowed down by using the diffracted light that is self-formed by the diffraction grating. Therefore, it is not necessary to install a waveguide such as an optical fiber or a light guide for guiding a light wave in an arbitrary direction. Since the diffraction effect of the light wave is used and an image is formed without using a lens or the like, focusing can be performed on the surface of the photodetector 31 and detection can be performed with high resolution. Further, the restrictions on the optical path of incident light incident on the diaphragm 21 are greatly reduced.

Since the optical restriction of incident / reflected light on the diaphragm 21 is reduced, the vibration analysis apparatus according to the first embodiment of the present invention can be configured with a simple system and can be downsized. Applications that can be used will expand. Furthermore, according to the vibration analysis apparatus according to the first embodiment of the present invention, by using a photodiode array for the photodetector 31, digital conversion is performed simultaneously with detection on the pixel. For this reason, an A / D converter becomes unnecessary, the response speed is improved, and the circuit scale can be reduced. In the reflection type diffraction grating as shown in FIG. 2, the light source 43, the power source of the photodetector 31, the drive circuit, and the processing circuit can be formed on the same substrate. Furthermore, like the photodetector 31 and its peripheral circuits, the diaphragm 21 formed with a diffraction grating can be manufactured by a semiconductor manufacturing process. As a result, it becomes possible to reduce the manufacturing cost of the vibration analyzing apparatus according to the first embodiment of the present invention.
As can be easily understood from FIG. 3, it is useful to use a semiconductor manufacturing process when forming the diffraction grating on the vibration plate 21, that is, when forming the groove / grating on the substrate. By using a semiconductor manufacturing process, a diffraction grating having an arbitrary grating period can be formed with good reproducibility, which is suitable for mass production. Further, since the semiconductor substrate used as the support substrate 11 has various physical properties, the mass and spring constant of the diaphragm 21 can be easily changed. For example, if silicon (Si) is used for the diaphragm 21, a laser having a wavelength λ = 1000 nm or less is used for the light source 43, and a highly reflective material is coated on the side wall of the grating, the light incident on the silicon portion is absorbed. Since only the diffracted light from the grating side wall is diffracted onto the photodetector 31, stray light to the photodetector 31 can be cut, and the S / N can be improved as a result.

  FIG. 6 shows an example of a mounting structure of the vibration analyzing apparatus according to the first embodiment of the present invention. As shown in FIG. 6B, a semiconductor substrate 51 having a diffraction grating and having a vibration plate 21 that vibrates by the sound pressure of a sound wave Φ incident from below, and a surface-emitting type semiconductor laser that irradiates light to the diffraction grating ( And a mounting substrate 55 having a photodiode (photodetector) 31 that detects light diffracted by the diffraction grating and converts it into an electrical signal. The semiconductor substrate 51 and the mounting substrate 55 are bonded together via a glass substrate (transparent substrate) 53. As a result, a three-layer structure comprising a mounting substrate 55, a glass substrate (transparent substrate) 53 under the mounting substrate 55, and a semiconductor substrate 51 disposed under the glass substrate (transparent substrate) 53, the present invention A part of the vibration analyzing apparatus according to the first embodiment is configured, and the displacement of the diaphragm 21 due to the sound pressure is converted into an electric signal. This three-layer structure may be integrated with, for example, a heat fusion technique or an adhesive.

  FIG. 6A is a plan view showing a pattern on the back surface of the mounting substrate 55. In the light source 43 mounted in the light source recess 155, as shown in FIG. 6A, bonding pads on the light source 43 and wirings 152c and 152d are connected by bonding wires 162c and 162d (note that the light source 43 For example, the wiring 152d may be led to the back surface of the light source 43, and the bonding pad on the light source 43 and the wiring 152c may be connected by the bonding wire 162c. The bonding pads on the light source 43 are electrically connected to pads (electrode pads) 151c and 151d through wirings 152c and 152d formed on the surface of the mounting substrate 55, respectively. The pads (electrode pads) 151c and 151d are connected to the modulator 42 (not shown in FIG. 6) (see FIG. 1).

  Similarly, the bonding pads on the photodetector 31 mounted in the photodetector recess 156 are connected to the wirings 152a and 152b and the bonding wires 162a and 162b (note that the back surface of the photodetector 31 is one electrode). In this case, for example, the wiring 152b may be led to the back surface of the photodetector 31, and the bonding pad on the photodetector 31 and the wiring 152a may be connected by the bonding wire 162a. Then, as shown in FIG. 6A, the bonding pads on the photodetector 31 are led to pads (electrode pads) 151a and 151b via wirings 152a and 152b formed on the surface of the mounting substrate 55, respectively. It is burned. The pads (electrode pads) 151a and 151b are connected to an amplifier 32 (not shown in FIG. 6) (see FIG. 1).

  As can be understood by referring to FIG. 6B, the portions of the pads 151 a to 151 d are exposed near both ends of the glass substrate (transparent substrate) 53. Electrical connection of the signal extraction wiring from the photodetector 31 becomes possible.

As the material of the mounting substrate 55, various organic materials such as synthetic resins, ceramics, glass, and semiconductors can be used. As the organic resin material, phenol resin, polyester resin, epoxy resin, polyimide resin, fluororesin, etc. can be used, and the base material used as a core when making a plate is paper, glass cloth, glass base Materials are used. A common inorganic substrate material is ceramic or semiconductor. In addition, glass is used when a metal substrate or a transparent substrate is required to enhance heat dissipation characteristics. As the material for the ceramic substrate, alumina (Al ₂ O ₃ ), mullite (3Al ₂ O ₃ .2SiO ₂ ), beryllia (BeO), aluminum nitride (AlN), silicon nitride (SiC), or the like can be used. Further, a metal base substrate (metal insulating substrate) in which a polyimide resin plate having high heat resistance is laminated on a metal such as iron or copper may be used. Of these materials, it is preferable to use a semiconductor substrate for the mounting substrate 55 because the light source recess 155 and the photodetector recess 156 can be easily formed by the photolithography technique and the etching technique similar to the manufacturing process of the semiconductor integrated circuit.

  The semiconductor substrate 51 is illustrated as if it is a single layer semiconductor substrate in FIG. 6, but may be a composite film such as an SOI substrate.

As shown in FIG. 4, the semiconductor vibration film (diaphragm) 21, in a matrix, a plurality of holes of a predetermined depth _{(recess) H i-1,1, ·····,} H i, 1 , H _{i, 2} , H _{i, 3} ,..., H _{i + 2,6} are arranged to form a two-dimensional diffraction grating. The semiconductor diaphragm (diaphragm) 21 formed with such a periodic pattern (two-dimensional diffraction grating) is fixed to the side wall of the bottom cavity 57 provided in the semiconductor substrate 51 by elastic beams 115a and 115b. ing. As shown by a two-dot chain line in FIG. 6A, when viewed as a planar pattern, the bottom cavity 57 is provided in the shape of a rectangular frame on the semiconductor substrate. As shown in FIG. 6, the diaphragm 21 is arranged in a rectangular diaphragm shape inside the bottom cavity 57. In FIG. 6A, the elastic beams 115a and 115b are also indicated by two-dot chain lines.

  As shown in FIG. 6, the beam of the semiconductor laser (light source) 43 passes through the glass substrate (transparent substrate) 53 and is diffracted by the diffraction grating of the semiconductor vibration film (vibration plate) 21, and again, the glass substrate (transparent substrate) 53. And is detected by a photodiode (photodetector) 31.

  In the vibration analysis apparatus according to the first embodiment of the present invention, all of the mounting substrate 55, the glass substrate (transparent substrate) 53, and the semiconductor substrate 51 are thin films of about 60 μm to 600 μm, preferably about 100 μm to 300 μm. A structure in which layers are bonded to each other can be used, which is suitable for downsizing and thinning. Furthermore, according to the first embodiment of the present invention, there is provided a vibration analysis apparatus that can observe a minute vibration displacement of a diaphragm as a large difference in reflected light intensity, is low in cost, and has a limited use range. realizable. Therefore, it is possible to provide a vibration analysis apparatus having high directivity, excellent stability, small and thin, environmental resistance, and a high manufacturing yield.

In particular, a surface-emitting type semiconductor laser (light source) that prepares a semiconductor substrate 51 in which a plurality of diaphragms 21 having different resonance frequencies f ₀ are arranged in a matrix or array, and irradiates light to each of the plurality of diaphragms 21. 43. A plurality of light sources 43 and light detectors 31 are used to detect light diffracted by the plurality of diaphragms 21 and convert it into an electrical signal. By irradiating the frequency ω _0A from each light source 43 and demodulating (lock-in amplification) using the corresponding sine wave frequency ω _0A as a synchronization signal, it becomes possible to analyze different frequencies at the same time.

Further, in certain cases, the transparent substrate 53 can be omitted in the vibration analysis apparatus according to the first embodiment of the present invention. For example, as shown in FIG. 7A, a transmitter 41, a modulator 42, a surface emitting semiconductor laser (light source) 43, a photodiode (light detector) 31, an amplifier 32, and a demodulator 33 are integrated. 2 A two-layer structure in which the semiconductor substrate 18 is a mounting substrate and the first semiconductor substrate 51 on which the semiconductor vibration film (vibration plate) 21 is formed may be bonded by a direct bonding method. In FIG. 7A, a light source 43 and a photodetector 31 are formed by using an epitaxial growth layer 19 formed on the second semiconductor substrate 18 made of a compound semiconductor, and between the light source 43 and the photodetector 31. Are electrically isolated by an element isolation region 181 consisting of a high resistance region by irradiation with an insulating film or proton (H ⁺ ). The first semiconductor substrate 51 is preferably silicon (Si) considering the mechanical strength of the thin semiconductor vibration film (vibration plate) 21, but may be a compound semiconductor substrate. Since the distance between the surface-emitting type semiconductor laser (light source) 43 and the photodiode (photodetector) 31 can be designed by a photolithography technique, it can be easily miniaturized and has a structure excellent in miniaturization and thinning. The light source 43 includes an n-side Bragg reflection film 191, an n-side cladding layer 192, an active layer 193, a p-side cladding layer, a p-side Bragg reflection film 195, a p-side electrode 182 and the like as shown in FIG. What is necessary is just to comprise with a surface emitting semiconductor laser. If the surface-emitting semiconductor laser shown in FIG. 7B is used as the photodetector 31 as the photodiode, a photodiode having the same forbidden bandwidth as that of the surface-emitting semiconductor laser is used. Therefore, it is possible to realize an extremely favorable vibration analysis device that is not affected by noise and stray light.

Even in the structure shown in FIG. 7, a semiconductor substrate 51 in which a plurality of diaphragms 21 having different resonance frequencies f ₀ are arranged in a matrix or array is prepared, and light is emitted so that each of the plurality of diaphragms 21 is irradiated with light. A light detector 31, an amplifier 32, and a demodulator 33 so as to demodulate (synchronize and detect) light diffracted by the plurality of diaphragms 21. If different sine wave frequencies ω _0A are irradiated from the respective light sources 43 and synchronous detection (lock-in detection) is performed with the corresponding sine wave frequency ω _0A , analysis of different frequencies can be performed simultaneously.

  According to the vibration analysis apparatus and the vibration analysis method according to the first embodiment of the present invention, digitalization and frequency analysis can be directly performed without using a complicated technique such as FFT.

(Second Embodiment)
As shown in FIG. 8, the vibration analyzing apparatus according to the second embodiment of the present invention includes a transmission type diffraction grating and includes a vibration plate 21 that vibrates due to mechanical vibration. This is different from the vibration analysis apparatus according to the embodiment. That is, the diaphragm 21 having a transmission type diffraction grating, the modulated light irradiation means 1 for irradiating the diaphragm 21 with light whose intensity x _in (t) changes in a sine wave, and the diaphragm 21 are transmitted. And demodulating means 2 for analyzing the frequency of the mechanical vibration by detecting the diffracted light and demodulating (synchronizing detection) with the frequency ω _0A of the sine wave. In addition, as described in the vibration analysis apparatus according to the first embodiment, more generally, the modulated light irradiation means 1 emits light whose intensity periodically changes using a repetitive signal, and demodulates the light. The means 2 may be demodulated using the repetitive signal as a synchronization signal. That is, the “repetitive signal” is not limited to a triangular wave or a rectangular wave, and any waveform may be used to indicate a cyclic change periodically. However, in the second embodiment, the intensity x _in ( The case where t) changes with a sine wave as shown by the following equation (1) will be described.

The point that the diaphragm 21 is suspended from the fixed portions 4a and 4b by the elastic connection portions 5a and 5b is the same as that of the vibration analyzing apparatus shown in FIG. Similarly to the vibration analysis apparatus according to the first embodiment, the modulated light irradiation unit 1 has a light source 43 for irradiating light to the diaphragm 21 and the light intensity x _in (t) changes in a sine wave. And a modulator 42 for modulating the output of the light source 43. If the light source 43 is a semiconductor light emitting element such as a semiconductor laser or a light emitting diode (LED), the modulator 42 may modulate the drive current of these semiconductor light emitting elements with a sine wave of the formula (1). The demodulating means 2 detects the diffracted light transmitted through the diaphragm 21 and converts it into an electrical signal (photodiode array) 31, an amplifier 32 that amplifies the electrical signal, and is amplified by the amplifier 32. A demodulator 33 that demodulates (synchronizes and detects) the electrical signal using the sine wave of equation (1) as a synchronization signal, obtains vibration amplitude and phase information of the diaphragm 21, and analyzes the frequency of mechanical vibration; Prepare. The modulator 42 and the demodulator 33 are connected to a transmitter 41 that supplies a sine wave signal having a frequency ω _0A .

  For the photodetector 31 shown in FIG. 8, it is preferable to use an image sensor such as a photodiode array, as in the vibration analysis apparatus shown in FIG. That is, the photodetector 31 does not detect the difference in light intensity, but detects the displacement of the two-dimensional diaphragm 21 by detecting a two-dimensional image of the diffraction image. For this reason, the photodetector 31 has a sufficiently wide area for the diffracted light so that the diffraction image can be detected without omission.

  In the vibration analysis apparatus according to the second embodiment shown in FIG. 8, light emitted from the light source 43 is incident on the vibration plate 21, and a transmission type diffraction grating is formed on the vibration plate 21. Therefore, the light wave emitted from the light source 43 is transmitted through the diaphragm 21 and produces a diffraction image on the surface of the photodetector 31. FIG. 8 shows a state in which the vibration plate 21 on which the diffraction grating is formed vibrates by the input of sound and the displacement of the diffraction image on the photodetector 31 changes. When the diaphragm 21 is stationary, that is, when there is no input by sound, a diffracted image is formed on the surface of the photodetector 31 by light emitted from the light source 43 at intervals as shown by a thick solid line and a thick broken line in FIG. Appears. Next, when sound pressure is input in this state, the diaphragm 21 vibrates using the boundary between the elastic connecting portions 5a and 5b and the substrate as a fulcrum. Therefore, the distance between the diaphragm 21 and the photodetector 31 changes, and the interval between the diffraction images on the surface of the photodetector 31 changes two-dimensionally with a thin solid line and a thin broken line. A thin solid line and a thin broken line in FIG. 8 indicate that the interval of the diffraction images has changed with the vibration of the diaphragm 21.

  Here, with respect to the diffraction image obtained on the photodetector 31, if attention is paid to a diffraction image having the same order and orientation, a difference is obtained on the photodetector 31 before and after vibration. By detecting the displacement of the diffraction image on the photodetector 31, the vibration displacement of the diaphragm 21 is output. At this time, the vibration of the continuous diaphragm 21 is detected and output not only when the diaphragm 21 is stationary or when vibrating. The diaphragm 21 on which the diffraction grating is formed is designed so as to exhibit a flat characteristic with respect to all frequencies of the input sound. However, the elastic connection portion that connects the mass of the diaphragm 21 or the fixed surface and the diaphragm 21. A plurality of diaphragms 21 having different spring constants 5a and 5b may be provided so as to have a higher sensitivity in a wide band with respect to the frequency of the input sound.

  Similarly to the photodetector 31 and its peripheral circuit, the diaphragm 21 formed with a diffraction grating can also be manufactured by a semiconductor manufacturing process. In particular, when forming a diffraction grating on the diaphragm 21, that is, when forming a groove / grating on the substrate, it is useful to use a semiconductor manufacturing process, and a diffraction grating having an arbitrary grating period can be formed with good reproducibility. Suitable for mass production. Moreover, since it has various physical properties, the mass and spring constant of the diaphragm 21 can be easily changed. For example, if silicon (Si) is used for the diaphragm 21, a laser having a wavelength λ = 1000 nm or less is used for the light source 43, and a highly reflective material is coated on the side wall of the grating, the light incident on the silicon portion is absorbed. Since only the diffracted light from the grating side wall is diffracted onto the photodetector 31, stray light to the photodetector 31 can be cut, and the S / N can be improved as a result.

  According to the vibration analysis apparatus and the vibration analysis method according to the second embodiment of the present invention, as in the first embodiment, digitization and frequency can be directly performed without using a complicated method such as FFT. Analysis is possible.

As in the first embodiment, the vibration analysis apparatus and the vibration analysis method according to the second embodiment detect time synchronously using a plurality of sine waves having different frequencies ω _0A , The frequency of the input sound wave can be identified by performing synchronous detection while sweeping the frequency ω _{0A of the} sine wave at a constant period.

(Third embodiment)
In the vibration analysis apparatus according to the first and second embodiments, synchronous detection is performed using a plurality of sine waves having different frequencies ω _0A in a time division manner, or the frequency ω _{0A of the} sine waves is swept at a constant period. While it has been described that it is possible to identify the frequency of the input sound wave by performing synchronous detection while sweeping the frequency ω _0A , frequency modulation is performed.

That is, in the vibration analyzers according to the first and second embodiments of the present invention, light is modulated by a sine wave having a constant frequency ω _0A as shown by the equation (1), and this is detected synchronously (demodulated). ) Explained the case. The vibration analyzer according to a third embodiment of the present invention, as the modulation index [delta], (1) rather than the formula, as shown in the following equation (9), the angular frequency omega _S in modulated signal sin .omega _S t A case of frequency modulation will be described.

x _in (t) = sin (ω _0A t + δ sin ω _S t + φ) (9)
FIG. 5B shows a state in which the incident light having the angular frequency ω _0A of the carrier wave is modulated with the angular frequency ω _S of the signal wave. FIG. 5A shows the vibration of the incident sound wave. By frequency modulation at the angular frequency omega _S of the modulated signal sin .omega _S t, narrowing combined with the vibration of the incident sound wave shows also possible to frequency analysis.

For this reason, in the vibration analyzing apparatus according to the third embodiment, as shown in FIG. 9, the vibration plate 21 vibrates due to mechanical vibration and the strength x _in (t) is ( a modulated light irradiation means 1 for irradiating a light varies with frequency modulated sine wave as shown by 9), to detect the light passing through the diaphragm 21, and (9) of the modulated signal sin .omega _S t And a demodulating means 2 for analyzing the frequency of mechanical vibrations. The modulated light irradiation means 1 and the demodulation means 2, local oscillator 47 supplies a modulation signal sin .omega _S t is connected. Further, a carrier wave transmitter 46 having an angular frequency ω _0A is connected to the modulated light irradiation means 1.

The modulated light irradiation means 1 modulates the output of the light source 43 so that the light source 43 irradiates the diaphragm 21 with light and the intensity x _in (t) of the light changes with a sine wave of the formula (9). Instrument 42. As shown in FIG. 10, the modulator 42 includes a mixer 421 and an operational amplifier 422. The light source 43 is connected between the output terminal of the operational amplifier 422 and the inverting terminal (− terminal), and the output of the mixer 421 is connected to the non-inverting terminal (+ terminal) of the operational amplifier 422. A mixer 421, a carrier wave from the transmitter 46, modulated signal sin .omega _S t from the local oscillator 47 are mixed, (9) a frequency modulated sine wave as represented by the formula is produced. If the light source 43 is a semiconductor light emitting element such as a semiconductor laser or a light emitting diode (LED), the modulator 42 modulates the drive current of these semiconductor light emitting elements with a frequency-modulated sine wave of equation (9). Just do it.

The demodulator 2 detects a light passing through the diaphragm 21 and converts it into an electric signal, an amplifier 32 for amplifying the electric signal, and an electric signal amplified by the amplifier (9). ) demodulated by the formula of the modulated signal sin .omega _S t, to obtain the amplitude and phase information of the vibration of the vibration plate 21, and a demodulator 33 for frequency analysis of the mechanical vibrations. The amplifier 32 includes an operational amplifier 321, and the output of the photodetector 31 is input to the inverting terminal (− terminal) of the operational amplifier 321 via the input resistor R <b> 1. A feedback resistor R2 is connected between the output terminal of the operational amplifier 321 and the inverting terminal (− terminal). As shown in FIG. 10, the demodulator 33 includes a mixer 331, a band pass filter (BPF) 332, and an amplifier 333. A mixer 331, a sine wave modulated from the output terminal of the operational amplifier 321, the modulation signal sin .omega _S t from the local oscillator 47 is inputted and mixed in a mixer 331. Thus, the mixer 331, the frequency signal of the difference between the modulated signal sin .omega _S t to the output of the sine wave and the local oscillator 47 of the carrier is extracted. The signal of the difference frequency is amplified by the amplifier 333 after passing through the band pass filter (BPF) 332.

  According to the vibration analysis apparatus and the vibration analysis method according to the third embodiment of the present invention, as in the first and second embodiments, the digital data can be directly digitalized without using a complicated method such as FFT. And frequency analysis are possible.

(Other embodiments)
Although the present invention has been described with reference to the first to third embodiments, it should not be understood that the descriptions and drawings constituting a part of this disclosure limit the present invention. From this disclosure, various alternative embodiments, examples and operational techniques will be apparent to those skilled in the art.

For example, in the description of the first to third embodiments, the case where the diaphragm 21 fluctuates due to the sound pressure has been illustrated and described, but the same applies to the case where the diaphragm 21 vibrates due to other mechanical vibrations such as a seismometer. The frequency analysis of the vibration is possible.
As described above, the present invention naturally includes various embodiments not described herein. Therefore, the technical scope of the present invention is defined only by the invention specifying matters according to the scope of claims reasonable from the above description.

It is a block diagram which shows the structure of the vibration analyzer which concerns on the 1st Embodiment of this invention. It is a schematic diagram which shows the vicinity of the diaphragm of the vibration analyzer which concerns on the 1st Embodiment of this invention in detail. It is sectional drawing which shows the specific structural example of the diaphragm of the vibration analyzer which concerns on the 1st Embodiment of this invention. FIG. 4A is a bird's-eye view showing a reflective two-dimensional diffraction grating used for the diaphragm of the vibration analysis apparatus according to the first embodiment of the present invention, and FIG. 4B is a reflection type used for the diaphragm. It is a bird's-eye view which shows a one-dimensional diffraction grating. FIG. 5A is a schematic diagram showing the vibration of the incident sound wave, and FIG. 5B is a schematic diagram showing a state in which the sine wave is further modulated by the angular frequency of the signal wave. FIG. 6A is a plan view showing a pattern viewed from the back surface of the mounting board for showing the mounting structure of the vibration analyzing apparatus according to the first embodiment of the present invention, and FIG. It is typical sectional drawing explaining the 3 layer structure which consists of a mounting substrate, a glass substrate (transparent substrate), and a semiconductor substrate. It is typical sectional drawing explaining the other mounting structure of the vibration analyzer which concerns on the 1st Embodiment of this invention. It is a schematic diagram which shows the structure of the vibration analyzer which concerns on the 2nd Embodiment of this invention. It is a block diagram which shows the structure of the vibration analyzer which concerns on the 3rd Embodiment of this invention. It is a schematic diagram which shows the vicinity of the diaphragm of the vibration analyzer which concerns on the 3rd Embodiment of this invention in detail.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 ... Modulated light irradiation means 2 ... Demodulation means 4a, 4b ... Fixed part 5a, 5b ... Elastic connection part 9R ... Cavity part 11 ... Diaphragm 11 ... Support substrate 12 ... Insulating film 13 ... Element isolation insulating film 13 ... Element isolation insulation Film 14 ... Interlayer insulating film 15 ... Passivation film 18 ... Second semiconductor substrate 19 ... Epitaxial growth layer 21 ... Diaphragm 21a, 21b ... Polysilicon connector 31 ... Photodetector (photodiode array)
32 ... Amplifier 33 ... Demodulator 41, 46 ... Transmitter 42 ... Modulator 43 ... Light source 47 ... Local transmitter 51 ... Semiconductor substrate (first semiconductor substrate)
53 ... Transparent substrate 55 ... Mounting substrate 57 ... Bottom cavity 115a, 115b ... Elastic beam 151a-151d ... Pad 152a, 152b, 152c, 152d ... Wiring 155 ... Light source recess 156 ... Photodetector recess 162a, 162b, 162c, 162d ... bonding wire 181 ... element isolation region 182 ... p-side electrode 191 ... n-side Bragg reflection film 192 ... n-side cladding layer 193 ... active layer 195 ... side Bragg reflection film 321 ... operational amplifier 331,421 ... mixer 333 ... amplifier 422 ... Operational amplifier

Claims (5)

A diaphragm that vibrates due to mechanical vibration;
A modulated light irradiation means that is driven by a repetitive signal and irradiates the diaphragm with light whose intensity changes periodically;
And a demodulating means for analyzing the frequency of the mechanical vibration by detecting the light passing through the diaphragm and demodulating the light using the repetitive signal.   The vibration analysis apparatus according to claim 1, wherein the vibration plate includes a diffraction grating. The demodulating means includes
A photodetector that detects the light passing through the diaphragm and converts it into an electrical signal;
An amplifier for amplifying the electrical signal;
And a demodulator for synchronously detecting the electrical signal amplified by the amplifier using the repetitive signal as a synchronization signal, and obtaining amplitude and phase information of vibration of the diaphragm from the demodulation means. Item 3. The vibration analysis device according to Item 1 or 2. A local oscillator connected to the modulated light irradiating means and the demodulating means for outputting a modulated signal;
The modulated signal is used to frequency modulate the periodically changing light,
The demodulating means includes
A photodetector that detects the light passing through the diaphragm and converts it into an electrical signal;
An amplifier for amplifying the electrical signal;
3. A mixer for frequency-mixing the electric signal amplified by the amplifier and the modulation signal, and obtaining amplitude and phase information of vibration of the diaphragm from the demodulating means. Vibration analysis equipment. A stage that is driven by a repetitive signal and irradiates light whose intensity changes periodically with respect to a diaphragm that is vibrating due to mechanical vibration;
And a frequency analysis of the mechanical vibration by detecting the light passing through the diaphragm and demodulating using the repetitive signal.

Images