JP4806739B2 - Correlation calculation optical microphone - Google Patents

Description

The present invention relates to an optical microphone using a diffracted wave or a deflected wave generated when a laser beam comes into contact with a sound wave or an ultrasonic 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 in hazardous locations, in high electromagnetic field environments, or in 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 or the vibration part is destroyed when a very strong sound wave is input after repeated use. There is a possibility.

Therefore, 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 generates a sound signal. Is converted into an electric signal.

FIG. 10 shows the operation and measurement principle of the optical microphone. In an optical microphone, when a sound wave is incident on a sound beam beam for detecting a sound wave {laser beam (laser beam)}, two chevron diffracted light distributions (diffraction images) are generated on an observation plane on an axis parallel to the sound wave propagation direction. Place a photodetector on one of these two chevron diffracted light distributions (diffracted images), or place each detector on the two chevron diffracted light distributions (diffracted images) to differentially amplify the output signals of both. By doing so, the sound signal is converted into an electric signal.

Please refer to FIG. FIG. 11 shows the configuration of a conventional optical microphone disclosed in Patent Document 1. As shown in FIG. 11, the conventional optical microphone includes a laser light source unit 1, lenses 21 and 22 constituting the output system optical component 2, lenses 31, 32 and 33 constituting the light receiving system optical component 3, and a detector. And an optical diode 41 constituting the. In the conventional optical microphone, a laser beam L in the air propagation path 5 is formed between the emission system optical component 2 and the light receiving system optical component 3, and a sound wave or an ultrasonic wave contacts the laser beam L from the outside in the propagation path 5. Be made.

The output signal converted into an electrical signal by the photodiode 41 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 1 is condensed and diffused by the lenses 21 and 22, shaped into a beam having a predetermined diameter, and incident on the lens 31 of the light receiving optical component 3. The light receiving system optical component 3 constitutes a Fourier optical system, and the laser beam L that has passed through the optical component 3 undergoes Fourier transform and enters the photodiode 41.

The laser beam L is Fourier-transformed by the first lens 31 of the light receiving system optical component 3, and the subsequent lens 32 and 33 adjust the beam size of the laser beam L to be sufficiently larger than the light receiving area of the photodiode 41. . 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. If taken in by the diode 41, it is canceled out and only a very weak output can be obtained.

Therefore, in the conventional optical microphone shown in FIG. 11, the photodiode 41 is installed at a position offset from the central axis of the transmitted beam in order to capture only one of the components. 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 41, an electric signal oscillating at the frequency of the wave to be measured is obtained.

FIG. 12 shows another example of a conventional optical microphone disclosed in Patent Document 1. In the conventional optical microphone shown in FIG. 12, the detector 4 is composed of two photodiodes 41 and 42. One photodiode 41 is installed at the same position as in the example shown in FIG. 12 and detects one of two components of the diffracted wave or the deflected wave whose phases are inverted from each other.

Further, the other photodiode 42 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 43 that changes the phase by 180 ° is connected, and the phase-converted output signal is combined with the output signal of the photodiode 41.

According to the optical microphone configured as shown in FIG. 12, the detector 4 includes a pair of photodiodes 41 and 42 that individually receive two components of the diffracted wave or the deflected wave whose phases are reversed. Then, the phase of the output signal of one photodiode 42 is converted to the opposite phase by the phase converter 42 and synthesized with the output signal of the other photodiode 41, so that the output of the detection signal is increased.
JP-A-8-265262

However, in the conventional optical microphone disclosed in Patent Document 1, all sounds received by the laser beam for detecting sound are detected (integrated), so that the spatial resolution of the sound in the optical axis direction of the laser beam (or the position of the sound) There is a problem that there is no resolution.

Further, in the conventional optical microphone disclosed in Patent Document 1, the signal intensity is obtained by detecting (integrating) all sounds received by the laser beam for detecting the sound, and the beam length of the laser beam is shortened. However, there is a problem that the signal strength to be detected is low and the SN ratio is low, which is not suitable for downsizing.

Therefore, the present invention has been made in view of the above-described problems in conventional optical microphones, and provides an optical microphone having spatial sound resolution (or sound position resolution) in the optical axis direction of a laser beam. Objective.

Another object of the present invention is to provide an optical microphone that can maintain the detected signal intensity and SN ratio even when the beam length of a laser beam is shortened, and is suitable for miniaturization. .

In one embodiment of the present invention, a pair of laser light sources that emit a pair of laser beams having a predetermined wavelength, and the pair of laser beams that are emitted from the pair of laser light sources and propagate in the air in an air propagation path are received. A pair of light receiving system optical components and a pair of laser beams emitted from the pair of laser light source units detect a diffracted wave or a deflected wave generated when the laser beam contacts with a sound wave or an ultrasonic wave when propagating through the air. A pair of photoelectric conversion elements for converting into an electrical signal, and a cross-correlation value calculation device that receives an output signal from the pair of photoelectric conversion elements and generates a cross-correlation value based on the output signal, The pair of laser light source units are arranged so that the pair of laser beams propagating through the air in the air propagation path substantially intersect, and the cross-correlation value calculation Location has a configuration to generate the cross-correlation value of the sound signal of the output signal from the pair of photoelectric conversion element exhibiting the diffraction waves or the deflection wave in the intersection of the pair of laser.

In one embodiment of the present invention, a plurality of pairs of laser light source units that emit a plurality of pairs of laser beams having a predetermined wavelength, and the plurality of laser beams that are emitted from the plurality of pairs of laser light source units and propagate in the air in an air propagation path. A plurality of light receiving system optical components that receive a pair of laser beams, and a plurality of pairs of laser beams emitted from the plurality of pairs of laser light source units come into contact with sound waves or ultrasonic waves when the plurality of pairs of laser beams propagate in the air A plurality of photoelectric conversion elements for detecting a plurality of diffracted waves or a plurality of deflection waves generated by the conversion and converting them into electrical signals, and receiving a plurality of output signals from the plurality of photoelectric conversion elements, A cross-correlation value calculation device that generates a plurality of cross-correlation values based on each of the plurality of pairs of laser light source units that propagate in the air in the air propagation path The cross-correlation value calculation device is arranged so that a pair of laser beams substantially intersect, and the plurality of photoelectric conversions indicating the plurality of diffracted waves or the plurality of deflection waves at a plurality of intersections of the plurality of pairs of laser beams A configuration is adopted in which the plurality of cross-correlation values of the plurality of sound signals of the plurality of output signals from the element are generated.

Further, the plurality of pairs of laser light source units, the plurality of light receiving optical components, and the plurality of photoelectric conversion elements may be arranged in a two-dimensional manner.

The plurality of pairs of laser light source units, the plurality of light receiving optical components, and the plurality of photoelectric conversion elements may be arranged in a three-dimensional manner.

The apparatus further includes a selection device connected between the plurality of photoelectric conversion elements and the cross-correlation value calculation device, and the selection device includes at least the plurality of output signals from the plurality of photoelectric conversion elements. Two or more output signals may be selected and given to the cross-correlation value calculation apparatus.

The selection device may be constituted by a multiplexer.

According to the present invention, since sound can be detected with a point, there is spatial resolution of sound (or resolution of sound position) in the optical axis direction of the laser beam. In addition, according to the present invention, sound can be detected from a point, so that it is possible to maintain the detected signal intensity and SN ratio even when the beam length of the laser beam is shortened, and for this reason, miniaturization is achieved. Suitable for

Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings. Note that the present invention is not limited to the following embodiment.

(Embodiment 1)
FIG. 1 is a perspective view showing a configuration of an optical microphone according to Embodiment 1 of the present invention.

As shown in FIG. 1, the optical microphone 100 according to Embodiment 1 of the present invention includes a pair of laser light source units 101 and 102, a pair of light receiving optical components 103 and 104, and a pair of photoelectric conversion elements 105 and 106. And a cross-correlation value calculation device 107. The pair of photoelectric conversion elements 105 and 106 and the cross-correlation value calculation device 107 are connected by signal lines 108 and 109. In the present embodiment, the laser beams L1 and L2 emitted from the pair of laser light source units 101 and 102 are substantially orthogonal to each other.

FIG. 2 is a diagram showing one optical system of the optical microphone 100 according to Embodiment 1 of the present invention. FIG. 3 is a diagram showing another optical system of the optical microphone 100 according to Embodiment 1 of the present invention.

As shown in FIGS. 2 and 3, the attenuators 110 and 111 are disposed between the pair of laser light source units 101 and 102 and the pair of light receiving system optical components 103 and 104. In this optical microphone 100, the laser light beams L 1 and L 2 have air propagation paths 112-1 and 112-2 between the attenuators 110 and 111 and the light receiving optical components 103 and 104. In the air propagation paths 112-1 and 112-2, the laser beams L1 and L2 are brought into contact with externally incident sound waves or ultrasonic waves.

The light receiving optical component 103 includes three imaging lenses 1031, 1032, and 1033. The three imaging lenses 1031, 1032, 1033 are arranged so that their optical axes are aligned with the central axis of the laser beam L 1. The light receiving optical component 104 includes three imaging lenses 1041, 1042, and 1043. The three imaging lenses 1041, 1042, and 1043 are arranged so that their optical axes are aligned with the central axis of the laser beam L2.

The pair of laser light source units 101 and 102 emits a pair of laser beams L1 and L2 having a predetermined wavelength. The pair of laser light source units 101 and 102 are arranged so that the pair of laser beams L1 and L2 propagating through the air in the air propagation paths 112-1 and 112-2 are substantially orthogonal to each other. The attenuators 108 and 109 receive a pair of laser beams L1 and L2 from the pair of laser light source units 101 and 102, adjust the intensity, and send them to the in-air propagation paths 112-1 and 112-2.

The light receiving system optical component 103 receives a pair of laser beams L1 emitted from the laser light source unit 101 and propagating through the air in the air propagation path 110. The imaging lenses 1031, 1032, and 1033 of the light receiving system optical component 103 shown in FIG. 2 condense and diffuse the laser beam L 1 from the laser light source unit 101, shape it into a laser beam of a predetermined diameter, and convert this laser beam to the photoelectric conversion element 105. To give. The imaging lenses 1031, 1032, and 1033 constitute a Fourier optical system that Fourier transforms the laser beam L 1 from the laser light source unit 101.

As shown in FIG. 3, the light receiving optical component 104 receives a pair of laser beams L2 that are emitted from the laser light source unit 102 and propagate through the air in the air propagation path 112-2. The imaging lenses 1041, 1042, and 1043 of the light receiving system optical component 104 shown in FIG. 3 condense and diffuse the laser beam L2 from the laser light source unit 102, shape the laser beam to a laser beam of a predetermined diameter, and convert the laser beam to the photoelectric conversion element 106. To give. The imaging lenses 1041, 1042, and 1043 constitute a Fourier optical system that Fourier transforms the laser beam L2 from the laser light source unit 102.

Laser beams L 1 and L 2 emitted from the laser light source units 101 and 102 are emitted to the in-air propagation path 112. The beam diameters of the laser beams L1 and L2 at this time vary depending on the lengths of the in-air propagation paths 112-1 and 112-2 in consideration of the conditions for propagating the space. For example, the diameter is several mm to several tens mm. A range of degree is desirable. When the laser beams L1 and L2 emitted from the laser light source units 101 and 102 come into contact with sound waves or ultrasonic waves in the air propagation paths 112-1 and 112-2, 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 diameters of the laser beams L1 and L2, the diffracted wave changes to a state called a deflection wave.

The pair of photoelectric conversion elements 105 and 106 come into contact with sound waves or ultrasonic waves when the laser beams L1 and L2 propagate from the pair of laser beams L1 and L2 emitted from the pair of laser light source units 101 and 102 in the air. The generated diffracted wave or deflected wave is received and detected via the light receiving optical parts 103 and 104 and converted into an electric signal.

The cross-correlation value calculation device 107 shown in FIG. 1 receives the output signals from the pair of photoelectric conversion elements 105 and 106 and generates a cross-correlation value based on the output signals. Specifically, the cross-correlation value calculation device 107 receives output signals from the pair of photoelectric conversion elements 105 and 106, and shows a pair of photoelectric conversion elements 105 that indicate a diffracted wave or a deflection wave at the intersection of the pair of laser beams L1 and L2. , 106 generates a cross-correlation value of the sound signal of the output signal.

Next, the generation of the cross-correlation value of the sound signal of the output signal from the pair of photoelectric conversion elements 105 and 106 by the cross-correlation value calculation device 107 will be described in detail.

In the measurement of the cross-correlation value of the sound signal, there is a strong correlation due to the sound located at the intersection of the pair of laser beams L1 and L2. When there is a sound source in the vicinity of the intersection of the pair of laser beams L1 and L2, the pair of laser beams L1 and L2 received by the pair of photoelectric conversion elements 105 and 106 includes a sound signal having a high correlation. In addition, when the sound source is located at a position away from the intersection of the pair of laser beams L1 and L2, the pair of laser beams L1 and L2 received by the pair of photoelectric conversion elements 105 and 106 includes a sound signal having a small correlation.

If the speed of light in air is compared with the speed of light, the speed of light is much faster, so it may be assumed that the sound pressure integration along the laser beam is instantaneous. Therefore, only the cross-correlation value where the time τ for calculating the cross-correlation value according to the definition of the cross-correlation function shown in the following (Equation 1) is τ = 0 may be examined.

When calculating the cross-correlation value, if there is a signal with a frequency lower than the target frequency band, this signal becomes a DC bias component, so an appropriate cross-correlation value cannot be calculated. The filtering process that calculates using the above may be performed as a pre-process of the cross-correlation value calculation process.

Next, the reproduction of the sound at the intersection of the pair of laser beams L will be described in detail.

The Fourier transform formula of r _xy (τ) is expressed by the following (Formula 2).

The Fourier transform formula of one output signal of the photoelectric conversion elements 105 and 106 is expressed by the following (Formula 3).

The approximate value S ₀₀ (t) of the sound pressure time signal at the intersection of the pair of laser beams L is expressed by the following (Equation 4).

Since r _xy (τ) and R _XY (ω) are quantities proportional to the energy of the signal, the calculation of √ {R _XY (ω)} is performed as described above to make the frequency dimension of the signal.

In order to return to the time signal, phase information in the frequency domain is required, but if the signal enhancement signal is extracted by the simple spectral subtraction method as described above, the approximate value S ₀₀ (t) of the sound pressure time signal can be obtained. . That is, as the simple phase information, the phase information of S _X (ω) is used as it is as phase information of √ {R _XY (ω)}, and an approximate value S ₀₀ (t of the sound pressure time signal is obtained by performing inverse Fourier transform. ) Is obtained.

Next, the cross-correlation value calculation device 107 of the optical microphone 100 according to Embodiment 1 of the present invention will be described in detail. FIG. 4 is a block diagram showing the configuration of the cross-correlation value calculation device 107 of the correlation calculation method optical mylophone 100 according to Embodiment 1 of the present invention.

4 includes two amplifiers 1071 and 1072, two filters 1073 and 1074, two AD converters 1075 and 1076, and a cross-correlation value calculation processing unit 1077.

The amplifier 1071 receives an analog output signal from the photoelectric conversion element 105, amplifies the signal, and supplies the amplified signal to the filter 1073. The filter 1073 removes a signal having a frequency lower than the target frequency band from the analog output signal from the amplifier 1071 and supplies the signal to the AD converter 1075. The AD converter 1075 converts the analog output signal from the filter 1073 into a digital signal, and gives this digital signal to the cross-correlation value calculation processing unit 1077.

The amplifier 1072 receives and amplifies the analog output signal from the photoelectric conversion element 106 and supplies the amplified signal to the filter 1074. The filter 1074 removes a signal having a frequency lower than the target frequency band from the analog output signal from the amplifier 1072 and supplies the signal to the AD converter 1076. The AD converter 1076 converts the analog output signal from the filter 1074 into a digital signal, and provides this digital signal to the cross-correlation value calculation processing unit 77. The cross-correlation value calculation processing unit 1077 executes the arithmetic processing of (Equation 1) to (Equation 4) based on the digital signal from the AD converters 1075 and 1076, and approximates the sound pressure time signal approximate value S. ₀₀ (t) is generated. The cross correlation value calculation processing unit 1077 is configured by a computer, for example.

Next, the cross-correlation value calculation processing unit 1077 of the cross-correlation value calculation device 107 of the optical microphone 100 according to Embodiment 1 of the present invention will be described in detail. FIG. 5 is a block diagram showing the cross-correlation value calculation processing unit 1077 of the cross-correlation value calculation device 107 of the correlation calculation method optical myophone 100 according to Embodiment 1 of the present invention.

As shown in FIG. 5, the cross-correlation value calculation processing unit 1077 includes a phase information generation unit 10771, a cross-correlation value generation unit 10772, a Fourier transform unit 10773, an amplitude information generation unit 10774, a synthesis unit 10775, an inverse Fourier transform unit 10777, and A reproduction signal output unit 10777 is provided.

The phase information generation unit 10771 receives the digital signal from the AD transformer 1075, generates the phase information of S _X (ω) shown in (Formula 3), and gives it to the synthesis unit 10775. The cross-correlation value generation unit 10772 receives the digital signal from the AD converter 1076, generates the cross-correlation value r _XY (τ) expressed by the above (Formula 1), and gives it to the Fourier transform unit 10773.

The Fourier transform unit 10773 performs the Fourier transform represented by (Formula 2) on the cross-correlation value r _XY (τ) from the cross-correlation value generation unit 10772 and supplies the result to the amplitude information generation unit 10774. The amplitude information generation unit 10774 receives the signal from the Fourier transform unit 10773, generates amplitude information of this signal in a predetermined frequency region, and supplies the amplitude information to the synthesis unit 10775.

The synthesizing unit 10775 synthesizes the phase information from the phase information generating unit 10771 and the amplitude information from the amplitude information generating unit 10774 and supplies the synthesized information to the inverse Fourier transform unit 10976. The inverse Fourier transform unit 10976 receives the signal from the synthesizing unit 10775 and performs inverse Fourier transform to generate a reproduction signal that is an approximate value S ₀₀ (t) of the sound pressure time signal represented by (Equation 4) above. This is given to the output unit 10777. The reproduction signal output unit 10777 outputs the reproduction signal to an audio signal processing device, an audio signal 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.

Further, the first embodiment of the present invention may be configured to include an output optical component having a plurality of lenses instead of the attenuators 110 and 111. These emission system optical components collect and diffuse the laser beam L from the laser light source units 101 and 102, shape the laser beam L to a predetermined diameter, and send the laser beam to the air propagation path 112. In the first embodiment of the present invention, the attenuators 110 and 111 may be deleted.

In addition, the photoelectric conversion element according to the first embodiment of the present invention may be composed of any element as long as it can detect a laser beam and output an electrical signal, such as a photodiode or a phototransistor. It may be configured.

According to the first embodiment of the present invention, since sound can be detected with a point, there is spatial resolution of sound (or resolution of sound position) in the optical axis direction of the laser beam. Further, according to the first embodiment of the present invention, since sound can be detected with a point, the detected signal intensity and SN ratio can be maintained even when the beam length of the laser beam is shortened, and Therefore, it is suitable for downsizing.

(Embodiment 2)
Next, a second embodiment of the present invention will be described in detail with reference to the drawings. FIG. 6 is a block diagram showing a configuration of the optical microphone according to Embodiment 2 of the present invention. In the second embodiment of the present invention, the same components as those in the first embodiment of the present invention are denoted by the same reference numerals, and the description thereof is omitted.

6, the optical microphone 200 according to the second embodiment of the present invention includes a plurality of pairs of laser light source units X1,..., XN, Y1,..., YN, a plurality of light receiving optical components RX1,. , RY1, ..., RYN, a plurality of photoelectric conversion elements PX1, ..., PXN, PY1, ..., PYN and a cross-correlation value calculation device 201. In the second embodiment, the number of the laser light source units in the X direction and the number of the laser light source units in the Y direction are both N. However, the number of laser light sources is not limited to this. The number of parts is arbitrary, and the number of laser light source parts in the X direction may be different from the number of laser light source parts in the Y direction.

The optical microphone 200 according to the second embodiment of the present invention includes a plurality of pairs of laser light source units X1,..., XN, Y1,..., YN, a plurality of light receiving optical components RX1, ..., RXN, RY1,. A plurality of photoelectric conversion elements PX1, ..., PXN, PY1, ..., PYN are two-dimensionally arranged.

The laser light source parts X1,..., XN and the laser light source parts Y1,..., YN are the same as the laser light source parts 101, 102. Each pair of the laser light source parts X1,..., XN and the laser light source parts Y1,..., YN is arranged such that each pair of laser beams L propagating in the air in the air propagation path 110 is substantially orthogonal. Yes.

The plurality of light receiving optical components RX1,..., RXN, RY1,..., RYN are the same as the light receiving optical components 103, 104. A plurality of light receiving system optical components RX1,..., RXN, RY1,..., RYN are emitted from the laser light source units X1,..., XN, Y1,. The laser beam L is received.

The plurality of photoelectric conversion elements PX1,..., PXN, PY1,..., PYN are a plurality of pairs of laser light beams from a plurality of pairs of laser light beams L emitted from a plurality of pairs of laser light source units X1,. A plurality of diffracted waves or a plurality of deflected waves generated by contact with sound waves or ultrasonic waves when L propagates in the air are detected and converted into electrical signals.

The cross-correlation value calculation apparatus 201 receives a plurality of output signals from the plurality of photoelectric conversion elements PX1,..., PXN, PY1,..., PYN and generates a plurality of cross-correlation values based on the plurality of output signals. Specifically, the cross-correlation value calculation apparatus 201 outputs a plurality of diffracted waves or a plurality of deflected waves at a plurality of intersections of a plurality of pairs of laser light beams from a plurality of pairs of laser light source units X1, ..., XN, Y1, ..., YN. A plurality of cross-correlation values of a plurality of sound signals of a plurality of output signals from the plurality of photoelectric conversion elements PX1,..., PXN, PY1,. The calculation process in which the cross-correlation value calculation apparatus 201 generates one of a plurality of cross-correlation values is the same as the calculation process in the first embodiment of the present invention.

The optical microphone 200 according to Embodiment 2 of the present invention includes a plurality of diffracted waves or a plurality of deflections at a plurality of intersections of a plurality of pairs of laser light beams from a plurality of pairs of laser light source units X1,..., XN, Y1,. A plurality of photoelectric conversion elements PX1,..., PXN, PY1,..., PYN exhibiting waves generate a plurality of cross-correlation values of a plurality of sound signals. It is possible to accurately detect the position of the intersection.

For example, the optical microphone 200 according to Embodiment 2 of the present invention three-dimensionally displays the magnitude of the sound signal as shown in FIG. 7 based on the detected value of the sound signal at a plurality of intersections of a plurality of pairs of laser beams. Then, it can be easily determined at which position the sound source exists. The example shown in FIG. 7 is an example in which N = 5 in a plurality of pairs of laser light source units X1,..., XN, Y1,. In the example shown in FIG. 7, it can be easily seen that the sound source exists at the intersection of the laser light source portions X2 and Y3.

According to the second embodiment of the present invention, since sound can be detected with a point, there is spatial resolution of sound (or resolution of sound position) in the optical axis direction of the laser beam. Further, according to the second embodiment of the present invention, since sound can be detected with a point, the signal intensity and SN ratio to be detected can be maintained even when the beam length of the laser beam is shortened, and Therefore, it is suitable for downsizing. Further, according to Embodiment 2 of the present invention, sound can be detected in real time in a predetermined two-dimensional area.

In addition, in a microphone using a conventional diaphragm, when performing measurement with a large number of microphones arranged and a high measurement density (a narrow measurement interval), the influence of sound wave diffraction and scattering cannot be ignored because the object of the microphone itself is large. High-precision measurements could not be performed at high frequencies. On the other hand, according to the second embodiment of the present invention, since sound can be detected with points, the measurement points on the measurement surface (measurement field) can be densely taken.

(Embodiment 3)
Next, Embodiment 3 of the present invention will be described in detail with reference to the drawings. FIG. 8 is a diagram for explaining the configuration of the optical microphone according to Embodiment 3 of the present invention. In the third embodiment of the present invention, the same components as those in the second embodiment of the present invention are denoted by the same reference numerals, and description thereof is omitted.

As shown in FIG. 8, the optical microphone 300 according to the third embodiment of the present invention is the same as the optical microphone 200 according to the second embodiment of the present invention, in which a plurality of photoelectric conversion elements PX1, ..., PXN, PY1,. Further, selection devices 301 and 302 connected between the PYN and the cross-correlation value calculation device 201 are further provided. The selection devices 301 and 302 select at least two output signals of the plurality of output signals from the plurality of photoelectric conversion elements PX1,..., PXN, PY1,. The selection device is composed of, for example, a multiplexer. In the third embodiment, the number of the laser light source units in the X direction and the number of the laser light source units in the Y direction are both N. However, the number of laser light sources is not limited to this. The number of parts is arbitrary, and the number of laser light source parts in the X direction may be different from the number of laser light source parts in the Y direction.

The optical microphone 300 according to the third embodiment of the present invention has the same effect as the optical microphone 200 according to the second embodiment of the present invention, and detects sound in a desired two-dimensional region in real time. Can be done.

(Embodiment 4)
Next, a fourth embodiment of the present invention will be described in detail with reference to the drawings. FIG. 9 is a diagram for explaining a configuration of an optical microphone according to Embodiment 4 of the present invention. In the fourth embodiment of the present invention, the same components as those in the second embodiment of the present invention are denoted by the same reference numerals, and the description thereof is omitted.

As shown in FIG. 9, the optical microphone 300 according to the fourth embodiment of the present invention is configured by arranging the optical microphones 200 according to the second embodiment of the present invention in a three-dimensional shape (a plurality of stages). . In FIG. 9, only a part of one optical microphone 200 is shown.

According to the fourth embodiment of the present invention, since sound can be detected with a point, there is spatial resolution of sound (or resolution of sound position) in the optical axis direction of the laser beam. Further, according to the third embodiment of the present invention, since sound can be detected with a point, the detected signal intensity and SN ratio can be maintained even when the beam length of the laser beam is shortened, and Therefore, it is suitable for downsizing. Further, according to Embodiment 4 of the present invention, sound can be detected in real time in a predetermined three-dimensional space.

The fourth embodiment of the present invention further includes a selection device connected between the plurality of photoelectric conversion elements and the cross-correlation value calculation device in the optical microphone 300, and the selection device includes a plurality of photoelectric conversion devices. It may be configured to select and provide at least one of a plurality of output signals from the element to the cross-correlation value calculation apparatus. In this case, sound can be detected in real time in a desired three-dimensional space.

The first to fourth embodiments of the present invention are not limited to a configuration in which a pair of laser beams are substantially orthogonal to each other, and may have a configuration in which a pair of laser beams substantially intersect.

The cross-correlation value includes a normalized cross-correlation value based on the maximum value of each signal, a normalized cross-correlation value based on a mean square value, an approximate sound signal reproduction value, and the like.

The optical microphone according to the first aspect of the present invention includes a pair of laser light source units that emit a pair of laser beams having a predetermined wavelength, and the pair that is emitted from the pair of laser light source units and propagates through the air in an air propagation path. A pair of light receiving system optical components that receive the laser beam and a diffracted wave generated when the laser beam contacts the sound wave or the ultrasonic wave when propagating through the air from the pair of laser beam emitted from the pair of laser light source units Alternatively, a pair of photoelectric conversion elements that detect deflection waves and convert them into electrical signals, and a cross-correlation value calculation device that receives an output signal from the pair of photoelectric conversion elements and generates a cross-correlation value based on the output signal; The pair of laser light source units are arranged so that the pair of laser beams propagating in the air in the air propagation path are orthogonal to each other, and the phase Correlation value calculation device has a configuration for generating the cross-correlation value of the sound signal of the output signal from the pair of photoelectric conversion element exhibiting the diffraction waves or the deflection wave in the intersection of the pair of laser.

According to the first aspect of the present invention, since sound can be detected with a point, there is spatial sound resolution (or sound position resolution) in the optical axis direction of the laser beam. In addition, according to the first aspect of the present invention, since sound can be detected with a point, the detected signal intensity and SN ratio can be maintained even when the beam length of the laser beam is shortened, and Therefore, it is suitable for downsizing.

An optical microphone according to a second aspect of the present invention includes a plurality of pairs of laser light source units that emit a plurality of pairs of laser beams having a predetermined wavelength, and is emitted from the plurality of pairs of laser light source units and propagates through the air in an air propagation path. A plurality of light receiving system optical components for receiving the plurality of pairs of laser beams, and sound waves or ultrasonic waves when the plurality of pairs of laser beams propagate from the plurality of pairs of laser beams emitted from the plurality of pairs of laser light source units. A plurality of photoelectric conversion elements that detect a plurality of diffracted waves or a plurality of deflection waves generated by contact with the plurality of photoelectric conversion elements and convert them into electrical signals; and a plurality of output signals from the plurality of photoelectric conversion elements A cross-correlation value calculation device that generates a plurality of cross-correlation values based on an output signal, and each pair of the plurality of pairs of laser light sources is in the air of the in-air propagation path The pairs of propagating laser beams are arranged so as to be orthogonal to each other, and the cross-correlation value calculation device includes the plurality of photoelectric waves indicating the plurality of diffracted waves or the plurality of deflected waves at a plurality of intersections of the plurality of pairs of laser beams. A configuration is adopted in which the plurality of cross-correlation values of the plurality of sound signals of the plurality of output signals from the conversion element are generated.

According to the second aspect of the present invention, since sound can be detected with a point, there is spatial resolution of sound (or resolution of sound position) in the optical axis direction of the laser beam. Further, according to the second aspect of the present invention, since sound can be detected with a point, the detected signal intensity and SN ratio can be maintained even when the beam length of the laser beam is shortened, and Therefore, it is suitable for downsizing. According to the second aspect of the present invention, sound can be detected in real time in a predetermined area.

An optical microphone according to a third aspect of the present invention is the optical microphone according to the second aspect of the present invention, wherein the plurality of pairs of laser light source units, the plurality of light receiving optical components, and the plurality of photoelectric conversion elements are two-dimensionally arranged. The arrangement is taken.

According to the third aspect of the present invention, since sound can be detected with a point, there is spatial sound resolution (or sound position resolution) in the optical axis direction of the laser beam. In addition, according to the third aspect of the present invention, since sound can be detected with a point, the signal intensity and SN ratio to be detected can be maintained even when the beam length of the laser beam is shortened, and Therefore, it is suitable for downsizing. According to the third aspect of the present invention, sound can be detected in real time in a predetermined two-dimensional area.

The optical microphone according to a fourth aspect of the present invention is the optical microphone according to the second aspect of the present invention, wherein the plurality of pairs of laser light source units, the plurality of light receiving optical components, and the plurality of photoelectric conversion elements are three-dimensionally arranged. The arrangement is taken.

According to the fourth aspect of the present invention, since sound can be detected with a point, there is spatial sound resolution (or sound position resolution) in the optical axis direction of the laser beam. In addition, according to the fourth aspect of the present invention, since sound can be detected with a point, the signal intensity and SN ratio to be detected can be maintained even when the beam length of the laser beam is shortened, and Therefore, it is suitable for downsizing. Further, according to the fourth aspect of the present invention, sound can be detected in real time in a predetermined three-dimensional area.

An optical microphone according to a fifth aspect of the present invention is connected between the plurality of photoelectric conversion elements and the cross-correlation value calculation device according to any one of the second to fifth aspects of the present invention. The selection device further includes a selection device that selects at least two or more output signals of the plurality of output signals from the plurality of photoelectric conversion elements and supplies them to the cross-correlation value calculation device.

According to the fifth aspect of the present invention, since sound can be detected with a point, there is spatial resolution of sound (or resolution of sound position) in the optical axis direction of the laser beam. In addition, according to the fifth aspect of the present invention, since sound can be detected with a point, the signal intensity and SN ratio to be detected can be maintained even when the beam length of the laser beam is shortened, and Therefore, it is suitable for downsizing. According to the fifth aspect of the present invention, sound can be detected in real time in a desired region.

The optical microphone according to a sixth aspect of the present invention employs a configuration in which, in the fifth aspect of the present invention, the selection device is configured by a multiplexer.

According to the sixth aspect of the present invention, since sound can be detected with a point, there is spatial sound resolution (or sound position resolution) in the optical axis direction of the laser beam. In addition, according to the sixth aspect of the present invention, since sound can be detected with a point, the signal intensity and SN ratio to be detected can be maintained even when the beam length of the laser beam is shortened, and Therefore, it is suitable for downsizing. According to the sixth aspect of the present invention, sound can be detected in real time in a desired region.

The present invention provides non-disturbance measurement of radiated sound in the vicinity of a solid surface, non-contact measurement of the vibration state of a solid material plate, measurement of a sound field in a fluid, measurement of non-disturbance generated in a jet flow, and elucidation of the mechanism of noise generation. Application, general sound wave and ultrasonic distribution remote sensing, sound intensity, detection of sound in public spaces (public spaces such as various halls, classrooms, shopping centers, etc.) It can be used for detection.

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 perspective view which shows the outline of the optical microphone which concerns on Embodiment 1 of this invention. It is a figure which shows one optical system of the optical microphone which concerns on Embodiment 1 of this invention. FIG. 3 is a diagram showing another optical system of the optical microphone according to Embodiment 1 of the present invention. It is a block diagram which shows the structure of the cross correlation value calculation apparatus of the optical mylophone which concerns on Embodiment 1 of this invention. It is a block diagram which shows the cross correlation value calculation process part of the cross correlation value calculation apparatus of the optical mylophone which concerns on Embodiment 1 of this invention. It is a block diagram which shows the structure of the optical mylophone which concerns on Embodiment 2 of this invention. It is the figure which displayed the magnitude | size of the sound signal three-dimensionally and schematically based on the detected value of the sound signal of the several intersection of the several pairs laser beam by the optical microphone which concerns on Embodiment 2 of this invention. It is a block diagram which shows the structure of the optical mylophone which concerns on Embodiment 3 of this invention. It is a figure which shows typically the structure of the optical mylophone which concerns on Embodiment 4 of this invention. It is a figure for demonstrating 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

100, 200, 300, 400 Optical microphones 101, 102, X1,..., XN, Y1,..., YN laser light source sections 103, 104, RX1,..., RXN, RY1,. PX1,..., PXN, PY1,..., PYN photoelectric conversion element 107, 201 cross-correlation value calculation device 301, 302 selection device

Claims (6)

A pair of laser light source units that emit a pair of laser beams of a predetermined wavelength; and
A pair of light receiving system optical components that receive the pair of laser beams that are emitted from the pair of laser light source units and propagate through the air in the air propagation path;
A pair that detects a diffracted wave or a deflected wave generated by contacting a sound wave or an ultrasonic wave when the laser beam propagates through the air from the pair of laser beams emitted from the pair of laser light source units, and converts them into an electrical signal. A photoelectric conversion element of
Anda correlation value calculation unit that processes the output signals from the pair of photoelectric conversion elements,
The pair of laser light source units are arranged so that the pair of laser beams propagating through the air in the air propagation path substantially intersect,
The cross-correlation value calculation device
A cross-correlation value generation unit that generates the cross-correlation value of the sound signal by receiving the output signals from the pair of photoelectric conversion elements indicating the diffracted wave or the deflection wave at the intersection of the pair of laser beams ;
A Fourier transform unit for calculating a result of applying a Fourier transform to the cross-correlation value;
An amplitude information generation unit for generating amplitude information by applying square root to the result calculated by the Fourier transform unit;
An output unit that generates an output signal by applying an inverse Fourier transform to a result of combining the phase information of the output signal of one of the pair of photoelectric conversion elements and the generated amplitude information ; An optical microphone. A plurality of pairs of laser light sources that emit a plurality of pairs of laser beams of a predetermined wavelength; and
A plurality of light receiving system optical components that receive the plurality of pairs of laser beams that are emitted from the plurality of pairs of laser light source units and propagate through the air in the air propagation path;
A plurality of diffracted waves or a plurality of deflected waves generated when the plurality of pairs of laser beams emitted from the plurality of pairs of laser light source units come into contact with sound waves or ultrasonic waves when propagating through the air. A plurality of photoelectric conversion elements that detect and convert into electrical signals;
Anda correlation value calculation unit that processes a plurality of output signals from said plurality of photoelectric conversion elements,
Each pair of the plurality of pairs of laser light source units is arranged so that the laser beams of each pair propagating through the air in the air propagation path substantially intersect,
The cross-correlation value calculation device
The plurality of cross-correlation values of a plurality of sound signals upon receiving the plurality of output signals from the plurality of photoelectric conversion elements indicating the plurality of diffracted waves or the plurality of deflection waves at a plurality of intersections of the plurality of pairs of laser beams. A cross-correlation value generation unit for generating
A Fourier transform unit for calculating a plurality of results obtained by applying a Fourier transform to each of the plurality of cross-correlation values;
An amplitude information generation unit that generates a plurality of amplitude information by applying square root to each result calculated by the Fourier transform unit;
An output unit that generates an output signal by applying an inverse Fourier transform to a result of combining the phase information of each of the output signals of each of the plurality of photoelectric conversion elements and each of the generated plurality of amplitude information. Features an optical microphone. The optical microphone according to claim 2, wherein the plurality of pairs of laser light source units, the plurality of light receiving optical components, and the plurality of photoelectric conversion elements are arranged in a two-dimensional manner. The optical microphone according to claim 2, wherein the plurality of pairs of laser light source units, the plurality of light receiving optical components, and the plurality of photoelectric conversion elements are arranged in a three-dimensional shape. The apparatus further includes a selection device connected between the plurality of photoelectric conversion elements and the cross-correlation value calculation device, and the selection device includes at least two or more of the plurality of output signals from the plurality of photoelectric conversion elements. 5. The optical microphone according to claim 2, wherein the output signal is selected and supplied to the cross-correlation value calculation apparatus. The optical microphone according to claim 5, wherein the selection device includes a multiplexer.

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