JP2007194677A - Optical microphone - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an optical microphone that can detect by itself arrival directions of sounds accurately and directly and can separately detect and record the sounds depending on their arrival directions. <P>SOLUTION: The optical microphone includes: a laser light source unit 1 for emitting a laser light beam with a prescribed wavelength; an emission system optical component 2 for shaping a laser beam to have a prescribed width; a light receiving system optical component 3 for receiving the laser beam emitted from the emission system optical component 2 and propagated through air in an aerial propagation path; and n (n is a natural number of 2 or over) photoelectric conversion elements that are arranged on a circumference around the optical axis of the laser beam emitted from the laser light source unit 1, detect diffracted waves or deflected waves generated when the laser beam emitted from the emission system optical component 2 is in contact with a sound wave or an ultrasonic wave during the propagation of the laser beam through air, and convert the detected waves into electric signals. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

The present invention relates to an optical microphone, and more particularly to an optical microphone using a diffracted wave or a deflected wave generated when a laser beam comes into contact with a sound wave.

For detection or measurement of sound waves and ultrasonic waves, those based on electromechanical principles such as electromagnetic microphones, electrostatic microphones, and piezoelectric elements are well known. These microphones have been difficult to apply to hazardous locations, high electromagnetic field environments, or explosion-proof areas. In addition, since this type of microphone has to install a fixed object at a sound collection place, the sound field is often disturbed and the installation conditions are often limited.

In addition, since this type of microphone has a mechanical vibration part, its characteristics change after repeated use many times, or when a very strong sound wave is input, the vibration part is destroyed. There was also a fear. Therefore, as a means for solving the disadvantages of such conventional electromechanical microphones, for example, a preliminary collection of lectures at the 1994 Kyushu Branch of the Japan Society of Applied Physics (issued in October 1993) (non-patent literature) 1) suggests the possibility of an “optical microphone” that attempts to detect a sound wave by using a diffracted wave or a deflected wave generated when a laser beam comes into contact with the sound wave.

However, in this method, a tracking scope or a lock-in amplifier is used for processing the detected signal. However, in order to use such a lock-in amplifier, it is necessary to input a reference wave from a sound wave generation source. However, there are cases where a reference wave cannot be taken like a naturally generated wave. It could not be used as an optical microphone. In addition, the diffracted wave or deflection wave generated by the contact of the laser beam with the sound wave has two components whose phases are reversed with each other. If these are received and detected as they are, the detection signal is very weak. Therefore, there was a technical problem in providing a practical optical microphone.

Accordingly, in order to solve the above-mentioned problems, the present inventor has developed a diaphragmless optical microphone using a photoelectric conversion element that detects a diffracted wave or a deflected wave and converts it into an electric signal (Japanese Patent Laid-Open No. Hei 8- No. 265262, Patent Document 1). As a result, a practical optical microphone could be provided.

Here, the operation and measurement principle of the conventional optical microphone disclosed in Patent Document 1 developed by the present inventor will be described. This optical microphone uses a laser beam as a measurement beam, receives extremely weak diffracted light generated by the phase modulation action of a sound wave propagating in the air with a light detector on the observation surface (rear focal plane of the light receiving lens), and outputs a sound signal. It converts to an electrical signal.

FIG. 15 shows the operation / measurement principle of the optical microphone. In the optical microphone, when a sound wave is incident on a sound beam for detecting a sound wave (laser beam (laser beam)), two mountain-shaped diffracted light distributions (diffraction images) are generated on an observation plane on an axis parallel to the sound wave propagation direction. Light detection is placed on one of these two chevron diffracted light distributions (diffracted images), or each detector is placed on the two chevron diffracted light distributions (diffracted images) to differentially amplify the output signals of both. Thus, the sound signal is converted into an electric signal.

Refer to FIG. FIG. 16 shows the configuration of a conventional optical microphone disclosed in Patent Document 1. As shown in FIG. 16, the conventional optical microphone includes a laser light source unit 101, lenses 121 and 122 constituting the emission system optical component 102, lenses 131, 132 and 133 constituting the light reception system optical component 103, and a detector. The laser beam 141 between the emission system optical component 102 and the light reception system optical component 103 is an air propagation path 105 of the laser beam L. In this propagation path 105, the laser beam L A sound wave or an ultrasonic wave is brought into contact with the outside.

The output signal converted into an electrical signal by the photodiode 141 is input to a signal processing unit (not shown), subjected to necessary signal processing, and then sent to an analysis device or a speaker.

The laser beam L emitted from the laser light source unit 101 is condensed and diffused by the lenses 121 and 122, shaped into a beam having a predetermined diameter, and enters the lens 131 of the light receiving system optical component 103. The light receiving system optical component 103 constitutes a Fourier optical system, and the laser beam L that has passed through the optical component 103 undergoes Fourier transform and enters the photodiode 141.

The laser beam L is Fourier-transformed by the first lens 131 of the light receiving system optical component 103, and the subsequent lens 132 and 133 adjust the beam size of the laser beam L to be sufficiently larger than the light receiving area of the photodiode 141. . A diffracted wave or a deflected wave has one red shift wave and one blue shift wave on the left and right sides with the central axis of the transmitted beam of the laser beam L as the axis of symmetry, and the phases of the two are inverted. When taking in with the diode 141, it cancels and only a very weak output is obtained.

Therefore, in the conventional optical microphone shown in FIG. 16, in order to capture only one of the components, the photodiode 141 is installed at a position offset from the central axis of the transmitted beam. In order to extract the component of the diffracted wave or the deflected wave, for example, when homodyne detection is performed using the transmitted laser beam as a local component by the photodiode 141, an electric signal oscillating at the frequency of the wave to be measured is obtained.

Another example of a conventional optical microphone disclosed in Patent Document 1 is shown in FIG. In the conventional optical microphone shown in FIG. 17, two photodiodes 141 and 142 are used as the detector 104. One photodiode 141 is installed at the same position as in the example shown in FIG. 16, and detects one of the two components of the diffracted wave or the deflected wave whose phases are inverted from each other.

Further, the other photodiode 142 is located at a position offset in the opposite direction from the central axis of the transmitted beam, and detects only the other component. A phase converter 143 that changes the phase by 180 ° is connected, and the phase-converted output signal is combined with the output signal of the photodiode 141.

According to the optical microphone configured as shown in FIG. 17, the detector 104 includes a pair of photodiodes 141 and 142 that individually receive two components of the diffracted wave or the deflected wave whose phases are inverted. Then, the phase of the output signal of one photodiode 142 is converted to the opposite phase by the phase converter 142 and synthesized with the output signal of the other photodiode 141, so that the output of the detection signal is increased.
Proceedings of the 1994 Kyushu Branch Lecture Meeting for Applied Physics (issued in October 1993) JP-A-8-265262

However, the conventional optical microphone disclosed in Patent Document 1 cannot directly detect the direction in which the sound arrives accurately, or can perform separation detection / separation recording based on the sound arrival direction.

In addition, in the conventional optical microphone disclosed in Patent Document 1, it was possible to give the optical microphone a wide variety of directivity, but the directivity of the optical microphone was changed by the photodetector part of the microphone. In addition, the directivity of the optical microphone cannot be controlled by the microphone body.

Therefore, the present invention has been made in view of the above-described problems with conventional optical microphones, and the optical microphone alone can accurately detect the direction in which sound arrives, and separate detection / separation recording according to the direction of sound arrival. It is an object of the present invention to provide an optical microphone that can be used.

Another object of the present invention is to provide an optical microphone that can change the directivity of the optical microphone at the photodetector portion of the microphone or control the directivity of the optical microphone with the microphone body. To do.

According to one embodiment of the invention,
A laser light source unit that emits a laser beam of a predetermined wavelength;
An output optical component that shapes the laser beam to a predetermined width; and
A light receiving system optical component that receives the laser beam emitted from the output system optical component and propagated through the air in the air propagation path;
From the laser beam emitted from the emission system optical component, when the laser beam propagates through the air, it detects a diffracted wave or a deflected wave generated by contact with a sound wave or an ultrasonic wave and converts it into an electrical signal, An optical microphone is provided that includes n (n is a natural number of 2 or more) photoelectric conversion elements arranged on a circumference centered on the optical axis of a laser beam emitted from a laser light source.

Of the n photoelectric conversion elements arranged on the circumference, one of the two photoelectric conversion elements arranged at a position rotated by 180 ° with respect to the central axis of the circumference. The phase of the output signal may be inverted and combined with the output of the other photoelectric conversion element.

Moreover, you may make it select the output from arbitrary number of photoelectric conversion elements among the said n photoelectric conversion elements.

Further, outputs from an arbitrary number of photoelectric conversion elements among the n photoelectric conversion elements may be selected and combined.

Also, according to one embodiment of the present invention,
A laser light source unit that emits a laser beam of a predetermined wavelength;
An output optical component that shapes the laser beam to a predetermined width; and
A light receiving system optical component that receives the laser beam emitted from the output system optical component and propagated through the air in the air propagation path;
From the laser beam emitted from the emission system optical component, when the laser beam propagates through the air, it detects a diffracted wave or a deflected wave generated by contact with a sound wave or an ultrasonic wave and converts it into an electrical signal, A plurality of optical microphones including n (n is a natural number of 2 or more) photoelectric conversion elements arranged on a circumference centered on the optical axis of a laser beam emitted from a laser light source;
There is provided an optical microphone in which laser beams emitted from laser light source portions of the plurality of optical microphones are arranged so as to be orthogonal to each other.

The plurality of optical microphones is two or three.

Of the n photoelectric conversion elements arranged on the circumference, one of the two photoelectric conversion elements arranged at a position rotated by 180 ° with respect to the central axis of the circumference. The phase of the output signal may be inverted and combined with the output of the other photoelectric conversion element.

Moreover, the incident direction of the sound wave or the ultrasonic wave can be measured by comparing the magnitudes of the outputs from the n photoelectric conversion elements of the plurality of optical microphones.

In addition, it is possible to differentially amplify outputs from any two photoelectric conversion elements among n photoelectric conversion elements of the plurality of optical microphones, and to measure the incident direction of the sound wave or the ultrasonic wave.

Moreover, the incident direction of the sound wave or the ultrasonic wave can be measured by obtaining a ratio of outputs from any two photoelectric conversion elements among n photoelectric conversion elements of the plurality of optical microphones.

The optical microphone of the present invention does not have a vibrating membrane like a conventional microphone, can directly detect the direction in which sound arrives accurately, and can perform separation detection and separation recording according to the direction of sound arrival.

Further, the optical microphone of the present invention can change the directivity of the optical microphone by the photodetector part of the microphone, or can control the directivity of the optical microphone by the microphone body.

The operation and detection principle of the optical microphone of the present invention will be described with reference to FIG. When the sound wave incidence direction is rotated by θ in the sound wave incidence plane perpendicular to the optical axis of the laser beam (laser beam), the inventor has a center connecting each central point of the two chevron diffracted light distributions (diffraction images). It has been found that the axis also changes rotationally by θ. Then, the present inventor has realized that if a number of detectors are arranged on the circumference on the observation surface, the sound can be detected separately for each incident direction of the sound wave, and the optical microphone of the present invention has been conceived. It came to do.

As described above, when the sound wave is incident on the sound beam detecting light beam part (laser beam) from a plurality of directions, the optical microphone of the present invention has two chevrons on the observation plane on the axis parallel to each sound wave propagation direction. It utilizes the fact that a diffracted light distribution (diffraction image) is generated. Light detection is placed on one of these two chevron diffracted light distributions (diffracted images), or each detector is placed on the two chevron diffracted light distributions (diffracted images) to differentially amplify the output signals of both. Thus, the sound signal is converted into an electric signal. By doing so, the direction in which sound arrives (incident direction) can be detected directly and accurately with the optical microphone alone, and separated detection and separated recording can be performed according to the incident direction of the sound.

Hereinafter, embodiments of the optical microphone of the present invention will be described in detail with reference to the drawings. The following embodiments show examples of the optical microphone of the present invention, and the optical microphone of the present invention is not limited to these embodiments.

(Embodiment 1)
FIG. 2 is a block diagram showing the configuration of the optical microphone of the present invention according to this embodiment. The optical microphone of the present invention according to the present embodiment shown in FIG. 2 has a laser light source unit 1, an output system optical component 2, a light receiving system optical component 3, and a detection unit 4, and the output system optical component. An aerial propagation path 5 of the laser beam L is between the light receiving system optical component 3 and 2. In this aerial propagation path 5, a sound wave or an ultrasonic wave incident on the laser beam L from the outside is brought into contact.

When a sound wave or an ultrasonic wave whose sound wave incident direction is rotationally changed by θ in the sound wave incident surface perpendicular to the optical axis of the laser beam L is incident, the detector 4 serving as an observation surface has two chevron diffracted light distributions (diffracted images). The central axis connecting the respective central points also changes rotationally by θ. Therefore, in the optical microphone of the present invention according to the present embodiment, the detection unit is composed of a plurality of elements in order to detect a mountain-shaped diffracted light distribution due to sound waves or ultrasonic waves incident from a plurality of incident directions. In the optical microphone of the present invention according to this embodiment shown in FIG. 2, a detection unit 4 in which eight elements for detecting a laser beam are arranged on the circumference is used. The detection unit 4 is not limited to this, and a detection unit in which n (n is a natural number of 2 or more) elements are arranged can be used as appropriate. The element used in the detection unit 4 may be any element as long as it is a photoelectric conversion element that can detect a laser beam and output an electrical signal.

Further, the output signal converted into an electric signal by the detection unit 4 is input to the signal processing unit 6, subjected to necessary signal processing, and then transmitted to an analysis device, a speaker, or the like. The laser beam L that can be used in the optical microphone of the present invention can be used in a wide range from the visible region to the infrared region, and the laser beam L having an arbitrary wavelength is selected according to the application.

The laser beam L emitted from the laser light source unit 1 is beam-shaped by the emission system optical component 2 and emitted to the air propagation path 5. The beam diameter of the laser beam L at this time varies depending on the length of the aerial propagation path 5 in consideration of the conditions for propagating the space, but is preferably in the range of several mm to several tens mm, for example. When the laser beam L emitted from the emission system optical component 2 comes into contact with a sound wave or an ultrasonic wave in the air propagation path 5, a diffracted wave is generated at that location. In this case, when the wavelength of the sound wave (ultrasonic wave) is very long with respect to the beam diameter of the laser beam L, the diffracted wave changes to a state called a deflection wave. The frequency of the diffracted wave or the deflected wave is Doppler shifted by the frequency of the wave to be measured as compared with the laser beam L.

In the optical microphone of the present invention, information of sound waves (ultrasound) can be obtained by detecting the diffracted wave or the deflected wave. The generated diffracted wave or deflected wave propagates together with the laser beam L, is received by the light receiving system optical component 3, and is then converted into an electrical signal by the detection unit 4.

FIG. 3 is a specific configuration example of the optical microphone of the present invention according to the present embodiment. In the optical microphone according to the present embodiment shown in FIG. 3, the emission system optical component 2 includes two lenses 2a and 2b. The light receiving optical component 3 includes three lenses 3a, 3b, and 3c. Furthermore, the detection unit 4 includes eight photodiodes 4a to 4h. These lenses are arranged on a straight line so that the laser beam L emitted from the laser light source unit 1 and the optical axis substantially coincide with each other. The eight photodiodes 4 a to 4 h are arranged at equal intervals on the circumference centered on the optical axis of the laser beam L emitted from the laser light source unit 1.

Reference is now made to FIG. FIG. 4 shows a circuit configuration of the detection unit 4 used in the optical microphone of the present invention according to this embodiment. As shown in FIG. 4A, in the present embodiment, the photodiodes 4a to 4h are arranged at equal intervals on the circumference. Further, as shown in FIG. 4B, the anodes of the photodiodes 4 a to 4 h are connected to the power source (Vdd), and each cathode outputs an electric signal to the signal processing unit 6. ing.

Here, FIG. 3 will be referred to again. The laser beam L emitted from the laser light source unit 1 is condensed and diffused by the lenses 2 a and 2 b, shaped into a beam with a predetermined diameter, and incident on the lens 3 a of the light receiving system optical component 3. The light receiving system optical component 3 of this embodiment constitutes a Fourier optical system, and the laser beam L that has passed through the optical component 3 is Fourier transformed and is incident on the photodiodes 4 a to 4 h of the detector 4.

The laser beam L is Fourier-transformed by the first lens 3a of the light receiving system optical component 3, and the subsequent lens 3b and 3c make the beam size sufficiently larger than the total light receiving area of the photodiodes 4a to 4h constituting the detector 4. It is adjusted to become.

The diffracted wave or the deflected wave has one red shift wave and one blue shift wave on the left and right sides with the central axis of the transmitted beam of the laser beam L as the axis of symmetry, and the phases of the two are inverted. If both a red shift wave and a blue shift wave are captured by a single photodiode, they are canceled out and only a very weak output can be obtained. Therefore, in the present embodiment, the center point of the detector 4, that is, the center of the circumference where the photodiodes 4a to 4h are arranged on the central axis of the transmitted beam so that only one component is captured by one detection element. Match the points.

For example, when a sound wave enters the laser beam from below, a diffraction wave that swings up and down appears, and two diffraction images appear through the lens. Among these, the upper diffraction image distribution corresponds to a red shift wave (ωi−ω), and the lower diffraction image distribution corresponds to a bull-shift wave (ωi + ω). In the present embodiment, the center axis of the laser and the center point of the detector 4, that is, the center point where the photodiodes 4a to 4h are arranged are matched, and detection signals from two opposing photodiodes are used.

In order to extract the component of the diffracted wave or the deflected wave, for example, when homodyne detection is performed using the transmitted laser beam as a local component by the photodiodes 4a to 4h, an electric signal oscillating at the frequency of the wave to be measured is obtained. By processing the electrical signals from these photodiodes 4a to 4h by the signal processing unit 6, the rotational change θ of the central axis connecting the central points of the two chevron diffracted light distributions (diffracted images), that is, the sound wave incident direction θ can be calculated.

Further, another example of the detection unit 4 of the optical microphone according to the present embodiment is shown in FIGS. In the optical microphone of the present invention according to the present embodiment, two photodiodes arranged at positions rotated by 180 ° with respect to the central axis among the photodiodes 4a to 4h are respectively diffracted waves or deflection waves. Two components whose phases are inverted are detected. In the example of the detection unit 4 shown in FIG. 5A, since eight photodiodes 4a to 4h are used, the photodiodes 4a and 4e, the photodiodes 4b and 4f, the photodiodes 4c and 4g, and the photodiode 4d. And 4h are paired, and two components of the diffracted wave or the deflected wave whose phases are reversed from each other are detected. FIG. 5B is a circuit diagram of the detection unit 4 shown in FIG.

Further, as shown in FIG. 5A, a phase converter 7 for phase-shifting the detected signal by 180 ° is connected to the photodiodes 4e to 4h, and the phase-converted output signals are respectively connected to the photodiodes. The signals are combined with the output signals 4a to 4d. Therefore, the signal detected by the detection unit can be increased.

Reference is now made to FIGS. 6 and 7 show another circuit configuration of the detection unit 4 used in the optical microphone of the present invention according to this embodiment. In the example shown in FIG. 4A, four photodiodes 4a to 4d are arranged at equal intervals on the circumference. 4B, the anodes of the photodiodes 4a to 4d are connected to the power source (Vdd), and each cathode outputs an electrical signal to the signal processing unit 6. ing. In the example shown in FIG. 4A, twelve photodiodes 4a to 4l are arranged at equal intervals on the circumference. Further, as shown in FIG. 4B, the anodes of the photodiodes 4 a to 4 l are connected to the power supply (Vdd), and each cathode outputs an electric signal to the signal processing unit 6. ing.

In the example of the detection unit 4 shown in FIGS. 6 and 7, the two photodiodes arranged at positions rotated by 180 ° among the photodiodes are inverted in phase with respect to the diffracted wave or the deflected wave, respectively. Two components are detected. Therefore, a phase converter 7 for phase-shifting the signal detected by one of the paired photodiodes by 180 ° is connected, and the phase-converted output signals are respectively connected to the output signal of the other photodiode. The signals may be combined and the signal detected by the detection unit may be increased.

Further, in the optical microphone of the present invention according to the present embodiment, as shown in FIG. 8, the detector 4 having no tip and no center portion may be used as indicated by reference numeral 40.

Further, in the optical microphone of the present invention according to this embodiment, as shown in FIG. 9, the detection unit 4 provided on the observation surface is provided with optical fibers 4a1 to 4h1, and diffraction received by these optical fibers 4a1 to 4h1. Light may be guided to the photodiodes 4a to 4h and received by the photodiodes 4a to 4g. Although FIG. 9 shows an example using the optical diodes 4a to 4h corresponding to the optical fibers 4a1 to 4h1, respectively, the number of optical diodes is reduced, and the diffracted light taken from the optical fibers 4a1 to 4h1 is reduced. It may be time-divisionally received and detected by a photodiode. The number of optical fibers and the number of optical diodes are not limited to those shown in FIG.

Further, the optical microphone of the present invention according to the present embodiment is separated for each incident direction of sound waves in a plane perpendicular to the optical axis of the laser beam (the number of detection elements existing within a semicircle 180 ° of the observation plane). Only), can record sound. For example, when the detection unit as shown in FIG. 4 is composed of eight photodiodes 4a to 4h, there are four photodiodes in a semicircle 180 ° of the observation surface, so four sound waves are incident on each incident direction. Can be separated and recorded.

In the present embodiment, an optical diode is used for the detection unit 4, but the optical microphone of the present invention is not limited to this, and a photoelectric conversion element that can detect a laser beam and output an electrical signal. Any element may be used as long as it is. For example, a phototransistor or the like may be used for the detection unit 4. Alternatively, a photoelectric conversion element in which n photoelectric conversion elements are integrally formed on one substrate may be used.

(Embodiment 2)
In this embodiment, two to three optical microphones of the present invention are used, and the three-dimensional laser beam arrangement is adopted by crossing the laser beams of the respective optical microphones at right angles. By doing so, it is possible to perform three-dimensional sound separation recording (three-dimensional microphone) of sound. The optical microphone of this embodiment can also be used as a sound wave propagation direction measuring instrument.

FIG. 10 shows an arrangement conceptual diagram of three laser beams (laser beams) in the optical microphone of the present invention according to this embodiment. Three orthogonal three-dimensional recording (xy plane, yz plane, zx plane) is possible with three orthogonal laser beams. In other words, the X-axis direction laser beam decomposes the sound wave propagation direction in the YZ plane, the Y-axis direction laser beam decomposes the sound wave propagation direction in the ZX plane, and the Z-axis direction laser beam decomposes the sound wave in the XY plane. Performs propagation direction decomposition.

In the present embodiment, three optical microphones according to the first embodiment are used,
By adopting the arrangement of laser beams as shown in FIG. 10, it is possible to perform three-dimensional decomposition recording (three-dimensional microphone) of sound.

Moreover, the optical microphone of the present invention according to the present embodiment can be used as means for measuring the propagation direction of sound waves, not acoustic recording. That is, the sound wave propagation direction can be determined by comparing the magnitude of the output signal waveform of each photodetecting element with the laser beam of one optical microphone. The three-dimensional direction is determined by comparing the output signal waveforms of the light detection elements of three orthogonal light beams.

It is also possible to subject the output signals of any two elements to differential amplification, and determine the direction of sound by the sign (±) of the output signal.

Further, the direction of the sound can be determined by obtaining the ratio (0 to 1) of the output signals of any two elements.

(Embodiment 3)
In this embodiment, the directivity of the optical microphone can be changed from time to time in accordance with the purpose, rather than changing the directivity of the optical microphone depending on the arrangement and combination of the detectors or performing this switching during measurement. An example will be described.

Please refer to FIG. FIGS. 11A and 11B show examples of detection units used in the optical microphone of the present invention according to this embodiment. FIG. 11A is a configuration diagram of the detection unit, and FIG. 11B is a circuit diagram of the detection unit. The detection unit 4 in the present embodiment has eight photodiodes 4a to 4h. In the optical microphone of the present invention according to the present embodiment, the directivity can be changed by selecting one or more of the photodiodes 4 a to 4 h by the switch unit 10. Yes. Note that other components of the optical microphone according to the present embodiment are the same as those of the first embodiment, and are omitted here.

Moreover, you may use what is shown to Fig.12 (a) and (b) as another example of the detection part 4. FIG. In the example of the detection unit 4 shown in FIG. 12A, an optical microphone having omnidirectionality can be realized by adding outputs from all the photodiodes 4a to 4h.

Further, as in the example of the detector 4 shown in FIG. 12B, an optical microphone having an arbitrary directivity can be realized by adding two outputs from the photodiodes 4a to 4h. In FIG. 12B, an example in which outputs from the photodiodes 4a to 4h are added two by two has been described. However, the present invention is not limited to this, and outputs from an arbitrary number of photodiodes are added. In addition, any directivity can be realized. In addition, when adding the outputs from the photodiodes 4a to 4h, the output may be selected by a switch, or the output from the photodiodes 4a to 4h may be selected by the signal processing unit 6. Moreover, it can also be changed to omnidirectionality by adding all the detector outputs within 180 ° of the detector 4.

13 (a) and 13 (b) and FIGS. 14 (a) and 14 (b), the outputs from an arbitrary number of photodiodes used in the detection unit 4 are added, and the directivity when an arbitrary directivity is realized. The schematic of a sex pattern (20a, 20b, 21a, 21b, 22a, 22b, 23a, 23b) is shown. FIGS. 13 (a) and 13 (b) and FIGS. 14 (a) and 14 (b) each show directivity by output from two photodiodes when directivity is achieved by output from one photodiode. When the directivity is realized by the outputs from the three photodiodes, the directivity pattern when the directivity is realized by the outputs from the four photodiodes is shown.

In addition, when the outputs from the photodiodes 4a to 4h are added, the output may be selected by a switch, or the output from the photodiodes 4a to 4h is selected by the signal processing unit 6 and a digital signal signal (DSP) is selected. The signal may be processed by a processor) and the directivity may be controlled.

The optical microphone according to the present embodiment can realize desired directivity at any time by selecting / switching elements to be used (electrical output from the elements) as necessary or combining them.

The optical microphone of the present invention can not only measure and record sound but also measure noise generated in a jet stream having a high sound pressure.

Various forms can be considered as the optical microphone of the present invention. The optical microphone of the present invention has the following application examples and features. (1) Measurement without disturbing the sound field is possible. (2) It can also be used for remote sensing. (3) Effective for detecting sound waves in places where normal microphones cannot be installed, including special atmospheres such as explosion-proof areas, high voltage (electric field), high magnetic fields, and extremely low temperatures. (4) Sound in a sealed container or in a room can be detected from the outside if there is an optical window with a width of several millimeters. (5) Since there is no vibration film, it is not destroyed even if a shock wave or the like enters. Shock wave measurement is also possible. (6) It can be used from a visible range to a near infrared range laser, and a visible or invisible detection unit can be created depending on the application. (7) Broadband sound waves can be measured simultaneously, and can be measured with a single light beam from the audible band to the high frequency band (low frequency ultrasonic waves). (8) In principle, it is possible to set the sound wave receiving unit (light beam antenna) to an arbitrary shape and to have various reception characteristics. In addition, these optical systems can be combined in a compact manner, or a sound wave detecting optical antenna or a macrophone (wide-area sound monitoring system) can be configured with the indoors and outdoors. (9) If measurement conditions are selected in addition to gas or plasma, it is applicable to measurement in water (in liquid) or in a transparent solid. (10) Since the directivity can be controlled by the light beam configuration and the photodetector configuration, there is a possibility that it can be used for measurement of the sound wave propagation direction and three-dimensional recording. (11) By using a laser beam aerial propagation method or an optical fiber propagation method for transmission of a received signal, electromagnetic noise or the like can be reduced. (12) A low-power semiconductor laser can be used, and the apparatus including the detector can be simple and inexpensive. (13) Microscopic sound source / vibration source can be detected by laser beam spatial scanning. (14) Since the gradient (density gradient) of the sound pressure can be detected by one light beam, a sound intensity measurement method using light can be realized. (15) By combining with computer tomography (CT), a sound spatial distribution visualization method (laser beam microphone CT) can be realized. (16) The system can be optimized and enhanced using optical information processing. In addition to the above, the optical microphone of the present invention is expected to be able to produce various features in accordance with the application and intended use.

It is a figure explaining the operation | movement and detection principle of the optical microphone of this invention. It is a block diagram which shows the structure of the optical microphone of this invention which concerns on one Embodiment. It is a figure which shows the specific structural example of the optical microphone of this invention which concerns on one Embodiment. It is a figure which shows the circuit structure of the detection part 4 used for the optical microphone of this invention which concerns on one Embodiment. It is a figure which shows the circuit structure of the detection part 4 used for the optical microphone of this invention which concerns on one Embodiment. It is a figure which shows the circuit structure of the detection part 4 used for the optical microphone of this invention which concerns on one Embodiment. It is a figure which shows the circuit structure of the detection part 4 used for the optical microphone of this invention which concerns on one Embodiment. It is a figure which shows the circuit structure of the detection part 4 used for the optical microphone of this invention which concerns on one Embodiment. It is a figure which shows the circuit structure of the detection part 4 used for the optical microphone of this invention which concerns on one Embodiment. It is an arrangement conceptual diagram of three laser beams (laser beams) in the optical microphone of the present invention concerning one embodiment. It is a figure which shows the circuit structure of the detection part 4 used for the optical microphone of this invention which concerns on one Embodiment. It is a figure which shows the circuit structure of the detection part 4 used for the optical microphone of this invention which concerns on one Embodiment. It is a figure which shows the directivity pattern of the detection part 4 used for the optical microphone of this invention which concerns on one Embodiment. It is a figure which shows the directivity pattern of the detection part 4 used for the optical microphone of this invention which concerns on one Embodiment. It is a figure explaining the operation | movement and measurement principle of an optical microphone. It is a figure which shows the structure of the conventional optical microphone. It is a figure which shows the structure of the conventional optical microphone.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Laser light source part 2 Output system optical component 3 Light reception system optical component 4 Detection part 4a-4h Photodiode 4a1-4h1 Optical fiber 5 Air propagation path 6 Signal processing part 7 Phase converter 10 Switch part L Laser beam

Claims (10)

A laser light source unit that emits a laser beam of a predetermined wavelength;
An output optical component that shapes the laser beam to a predetermined width; and
A light receiving system optical component that receives the laser beam emitted from the output system optical component and propagated through the air in the air propagation path;
From the laser beam emitted from the emission system optical component, when the laser beam propagates through the air, it detects a diffracted wave or a deflected wave generated by contact with a sound wave or an ultrasonic wave and converts it into an electrical signal, An optical microphone comprising n photoelectric conversion elements (n is a natural number of 2 or more) arranged on a circumference centering on an optical axis of a laser beam emitted from a laser light source. Of the n photoelectric conversion elements arranged on the circumference, the output of one of the two photoelectric conversion elements arranged at a position rotated by 180 ° with respect to the central axis of the circumference The optical microphone according to claim 1, wherein the phase of the signal is inverted and synthesized with the output of the other photoelectric conversion element. The optical microphone according to claim 1 or 2, wherein an output from an arbitrary number of photoelectric conversion elements among the n photoelectric conversion elements is selected. The optical microphone according to claim 1 or 2, wherein outputs from any number of photoelectric conversion elements among the n photoelectric conversion elements are selected and combined. A laser light source unit that emits a laser beam of a predetermined wavelength;
An output optical component that shapes the laser beam to a predetermined width; and
A light receiving system optical component that receives the laser beam emitted from the output system optical component and propagated through the air in the air propagation path;
From the laser beam emitted from the emission system optical component, when the laser beam propagates in the air, it detects a diffracted wave or a deflected wave generated by contact with a sound wave or an ultrasonic wave and converts it into an electrical signal, A plurality of optical microphones including n photoelectric conversion elements (n is a natural number of 2 or more) arranged on a circumference centered on the optical axis of a laser beam emitted from a laser light source;
An optical microphone in which laser beams emitted from laser light source units of the plurality of optical microphones are arranged so as to be orthogonal to each other. The optical microphone according to claim 5, wherein the plurality of optical microphones is two or three. Of the n photoelectric conversion elements arranged on the circumference, the output of one of the two photoelectric conversion elements arranged at a position rotated by 180 ° with respect to the central axis of the circumference The optical microphone according to claim 5 or 6, wherein the phase of the signal is inverted and synthesized with the output of the other photoelectric conversion element. The optical microphone according to claim 5, wherein an incident direction of the sound wave or the ultrasonic wave is measured by comparing magnitudes of outputs from n photoelectric conversion elements of the plurality of optical microphones. . 8. The output from any two photoelectric conversion elements among the n photoelectric conversion elements of the plurality of optical microphones is differentially amplified, and the incident direction of the sound wave or the ultrasonic wave is measured. The optical microphone as described in 1. The incident direction of the sound wave or the ultrasonic wave is measured by calculating a ratio of outputs from arbitrary two photoelectric conversion elements among n photoelectric conversion elements of the plurality of optical microphones. An optical microphone according to claim 1.