Optical microphone

Abstract

To provide an optical microphone capable of controlling directivity toward a sound source.SOLUTION: An optical source 110, a first optical splitter 120 that splits light from the optical source into reference light and measuring light, a second optical splitter 130 that splits the measuring light into N pieces of measuring light, a first emitting unit 141 that emits the N pieces of measuring light to a S1 of a predetermined space, a first light receiving unit 145 that receives the N pieces of measuring light 144 propagated through the predetermined space, a third optical splitter 150 that splits the reference light into N pieces of measuring light, and N optical couplers 161 to 168 that couple the N pieces of measuring light and the N pieces of reference light on a one to-one basis; N photodetectors 171 to 178 that receive the N coupled light beams and detect interference between the measurement light beam and the reference light beam in each of the N coupled light beams, and a control unit 180 that controls directivity of sound collection by performing signal processing on N detection signals output from the N photodetectors are provided, the N measurement light beams are arranged in parallel at equal intervals in a predetermined space, and the control unit sequentially delays the N detection signals by a predetermined time interval and adds the detection signals.SELECTED DRAWING: Figure 2

Description

[Technical Field]

[0001] The present disclosure relates to an optical microphone capable of recording wide-band sounds. [Background technology]

[0002] Patent Document 1 discloses a laser microphone device that, unlike a normal microphone that electrically detects the vibration of a diaphragm caused by sound, does not use a diaphragm but instead uses laser light to detect changes in the refractive index of air caused by sound, thereby converting audio signals into electrical signals via laser light. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Japanese Patent Application Publication No. 59-174100 Summary of the Invention [Problem to be solved by the invention]

[0004] However, the laser microphone device described in Patent Document 1 has a problem in that it is difficult to identify the direction in which the sound source is located from the device.

[0005] The present disclosure provides an optical microphone that can control the directionality toward a sound source. [Means for solving the problem]

[0006] An optical microphone according to one aspect of the present disclosure includes a light source, a first optical splitter that splits light emitted from the light source into reference light and measurement light, a second optical splitter that splits the measurement light into N measurement light beams (N is an integer of 2 or more), a first emitting unit that emits the N measurement light beams from different positions toward a predetermined space, a first light receiving unit that receives the N measurement light beams after propagating through the predetermined space, a third optical splitter that splits the reference light into N reference light beams, and a second optical splitter that splits the N measurement light beams received by the first light receiving unit. and N optical couplers that couple the N reference beams one-to-one with the measurement beams, respectively; N photodetectors that receive the N combined beams combined by the N optical couplers and detect interference between the measurement beam and the reference beam in each beam; and a control unit that controls the directionality of sound collection by processing the N detection signals output from the N photodetectors, wherein the N measurement beams are arranged in parallel and at equal intervals in the specified space, and the control unit adds the N detection signals in order, delaying them by a specified time interval.

[0007] an optical microphone according to one embodiment of the present disclosure, comprising: a light source; a first optical splitter that splits light emitted from the light source into reference light and measurement light; a second optical splitter that splits the measurement light into N (N is an integer equal to or greater than 2) measurement light beams; a first emission unit that emits the N measurement light beams from different positions toward a predetermined space; a first light receiving unit that receives the N measurement light beams after propagating through the predetermined space; a third optical splitter that splits the reference light into N reference light beams; N optical couplers that combine the N measurement light beams received by the first light receiving unit with the N reference light beams in a one-to-one relationship; N photodetectors that receive the N combined light beams combined by the N optical couplers and detect interference between the measurement light and the reference light in each of the N combined light beams; and a control unit that controls sound collection directionality by processing the N detection signals output from the N photodetectors. [Effects of the Invention]

[0008] The optical microphone according to the present disclosure can control the directionality toward the sound source. [Brief explanation of the drawings]

[0009] [Figure 1] FIG. 1 is a perspective view for explaining an outline of the optical microphone according to the first embodiment. [Figure 2] FIG. 2 is a diagram illustrating a configuration of the optical microphone according to the first embodiment. [Figure 3] FIG. 3 is a diagram showing the relationship between the optical microphone according to the first embodiment and the direction from which a sound source comes. [Figure 4] FIG. 4 is a diagram for explaining signal processing of the optical microphone according to the first embodiment. [Figure 5] FIG. 5 is a diagram illustrating a configuration of an optical microphone according to a modification of the first embodiment. [Figure 6] FIG. 6 is a diagram for explaining an outline of the optical microphone according to the second embodiment. [Figure 7] FIG. 7 is a diagram illustrating a configuration of an optical microphone according to the second embodiment. [Figure 8] FIG. 8 is a diagram illustrating a configuration of the optical microphone according to the second embodiment. DETAILED DESCRIPTION OF THE INVENTION

[0010] (Findings that formed the basis of this disclosure) In the laser microphone device shown in Patent Document 1, when laser light emitted from a light source passes through sound waves emitted from a sound source, it is modulated in accordance with the density of the air caused by the sound waves.The modulated laser light is detected by a photodetector, thereby detecting sound even without a diaphragm.

[0011] However, this laser microphone device has the problem that it is difficult to control the directivity toward the sound source. Furthermore, because of this problem, when sound sources are located at two different positions, it is difficult to distinguish and detect these two sound sources.

[0012] Therefore, the inventors have come up with an optical microphone that can control the directionality toward the sound source.

[0013] an optical microphone according to one embodiment of the present disclosure, comprising: a light source; a first optical splitter that splits light emitted from the light source into reference light and measurement light; a second optical splitter that splits the measurement light into N (N is an integer equal to or greater than 2) measurement light beams; a first emission unit that emits the N measurement light beams from different positions toward a predetermined space; a first light receiving unit that receives the N measurement light beams after propagating through the predetermined space; a third optical splitter that splits the reference light into N reference light beams; N optical couplers that combine the N measurement light beams received by the first light receiving unit with the N reference light beams in a one-to-one relationship; N photodetectors that receive the N combined light beams combined by the N optical couplers and detect interference between the measurement light and the reference light in each of the N combined light beams; and a control unit that controls sound collection directionality by processing the N detection signals output from the N photodetectors.

[0014] According to this method, N measurement beams are propagated within a predetermined space for detecting sound, and the N measurement beams modulated by the air density caused by the sound propagating through the air in the predetermined space are detected to interfere with the reference beam, and the N detection signals obtained are processed to detect sound at N different positions. Therefore, the directivity of sound collection can be controlled so that sound can be detected from an arrival direction at an angle inclined to the arrangement direction of the N measurement beams.

[0015] Furthermore, the first emitting unit may have N first collimating lenses arranged at different positions from each other and converting each of the N measurement light beams into parallel light beams, and the first light receiving unit may have N second collimating lenses arranged opposite the N first collimating lenses across the specified space, and the N second collimating lenses may each receive the N measurement light beams converted into parallel light beams by the N first collimating lenses.

[0016] According to this, each of the N measurement beams propagating in a predetermined space is converted into a parallel beam, so that the density of the air caused by the propagating sound can be detected effectively.

[0017] The N first collimating lenses and the N second collimating lenses may be arranged such that the N measurement beams converted into parallel beams are arranged parallel and at equal intervals in the predetermined space.

[0018] Therefore, it is possible to easily detect sounds entering a predetermined space from directions of arrival at angles inclined to the direction of arrangement of the N measurement beams, and also to reduce the processing load required for processing the N signals.

[0019] Furthermore, the optical modulator may further include an optical modulator that modulates the reference light and outputs the modulated reference light to the third optical splitter, and the control unit may have an FM (Frequency Modulation) demodulator that demodulates the N detection signals, an AD (Analog to Digital) converter that converts the N detection signals, and a signal processor that performs the signal processing on the AD-converted N detection signals.

[0020] Therefore, sound can be effectively detected from the interference between the measurement light and the reference light.

[0021] The optical coupler further includes an optical switch that selectively switches the destination of the measurement light emitted from the first optical coupler to one of a first outlet optically connected to the second optical coupler and a second outlet, a fourth optical coupler that splits the measurement light emitted from the second outlet into M measurement light beams (M is an integer of 2 or more and N or less), a second emitting unit that emits the N measurement light beams split by the fourth optical coupler from different positions toward the predetermined space, and a second light receiving unit that receives the M measurement light beams after propagating through the predetermined space, wherein a first emitting direction of the N measurement light beams emitted by the first emitting unit and a second emitting direction of the M measurement light beams emitted by the second emitting unit intersect with each other, and M optical couplers among the N optical couplers are received by the second light receiving unit. The M measurement light beams irradiated by the optical couplers are respectively combined with M reference light beams among the N reference light beams in a one-to-one relationship, and the M photodetectors among the N photodetectors receive the M combined light beams combined by the M optical couplers and detect interference between the measurement light and the reference light therein, and the control unit may (i) control the directivity of the sound collection along the arrangement direction of the N measurement light beams by signal processing the N detection signals output from the N photodetectors when the measurement light beams are emitted from the first exit by controlling the optical switch, and (ii) control the directivity of the sound collection along the arrangement direction of the M measurement light beams by signal processing the M detection signals output from the M photodetectors when the optical switch is controlled to emit the measurement light from the second exit.

[0022] This makes it possible to selectively control the directivity of sound collection so as to selectively detect a sound coming from a direction tilted toward the first direction in which N measurement beams are arranged and a sound coming from a direction tilted toward the second direction in which M measurement beams are arranged, thereby enabling the direction of the sound source to be identified more accurately.

[0023] Hereinafter, an optical microphone according to one aspect of the present disclosure will be specifically described with reference to the drawings.

[0024] It should be noted that the embodiments described below each illustrate a specific example of the present invention. The numerical values, shapes, materials, components, component placement and connection configurations, steps, and step order shown in the following embodiments are merely examples and are not intended to limit the present invention. Furthermore, among the components in the following embodiments, components that are not described in the independent claims that represent the highest concept are described as optional components.

[0025] (Embodiment 1) The configuration of the optical microphone according to the first embodiment will be described.

[0026] Fig. 1 is a perspective view for explaining an outline of the optical microphone according to the embodiment 1. In Fig. 1, only a frame member 140 of the optical microphone 100 is shown.

[0027] The optical microphone 100 is a device that detects sound propagating through a predetermined space S1 inside the square frame member 140 by emitting N (eight in this embodiment) measurement beams 144 from one side of the square frame member 140 to the other side opposite the first side. The N measurement beams 144 are arranged side by side at different positions in the X-axis direction, and sound is detected by each of the N measurement beams 144. In other words, the optical microphone 100 can detect sound at N different positions in the X-axis direction, and can detect sound propagating through the predetermined space S1 from an arrival direction having an X-axis component.

[0028] FIG. 2 is a diagram illustrating a configuration of the optical microphone according to the first embodiment.

[0029] The optical microphone 100 includes a light source 110, a first optical splitter 120, a second optical splitter 130, a frame-shaped member 140, a third optical splitter 150, N optical couplers 161 to 168, N photodetectors 171 to 178, and a control unit 180.

[0030] The light source 110 emits light. The light source 110 is, for example, a laser light source that emits laser light.

[0031] The first optical splitter 120 splits the light emitted from the light source 110 into two beams. The first optical splitter 120 emits one of the two split beams, a reference beam, from a first exit 121 and emits the other of the two beams, a measurement beam, from a second exit 122. The first optical splitter 120 is, for example, an optical coupler or an optical splitter. The light source 110 and the first optical splitter 120 are optically connected by, for example, an optical fiber, and the first optical splitter 120 receives the light emitted from the light source 110 via the optical fiber.

[0032] The second optical branching device 130 divides the measurement light, which is one of the two beams divided by the first optical branching device 120, into N (eight in this embodiment) measurement light beams. The second optical branching device 130 is, for example, an optical coupler or an optical splitter. The first optical branching device 120 and the second optical branching device 130 are optically connected by, for example, an optical fiber, and the second optical branching device 130 receives the measurement light emitted from the second exit port 122 of the first optical branching device 120 via the optical fiber.

[0033] The frame-shaped member 140 has, for example, a square shape. The frame-shaped member 140 has a first light-emitting portion 141 that forms one side on the positive side in the Y-axis direction and a first light-receiving portion 145 that forms one side on the negative side in the Y-axis direction. The frame-shaped member 140 further has two rod-shaped members 148 and 149 that connect one end and the other end of the rod-shaped first light-emitting portion 141 to one end and the other end of the rod-shaped first light-receiving portion 145, respectively. The first light-emitting portion 141, the first light-receiving portion 145, and the two members 148 and 149 surround a predetermined space S1. Note that the frame-shaped member 140 is a member for arranging the first light-emitting portion 141 and the first light-receiving portion 145 so that they face each other in the Y-axis direction with the width of the predetermined space S1 between them. However, the configuration is not limited to this as long as the first light-emitting portion 141 and the first light-receiving portion 145 are arranged facing each other in the Y-axis direction. In the frame-shaped member 140, the predetermined space S1 is in communication with the external space, so sound from a sound source in the external space propagates through the air and then propagates through the predetermined space S1.

[0034] The second optical splitter 130 and the first output unit 141 are optically connected by, for example, N optical fibers, and the first output unit 141 receives the N measurement beams output from the N output ports 131 of the second optical splitter 130 via the N optical fibers. The first output unit 141 receives the N measurement beams split by the second optical splitter 130 and outputs N measurement beams 144 from different positions toward a predetermined space S1. The first output unit 141 has N collimating lenses 143 arranged at different positions in the X-axis direction and converting the N measurement beams received from the N output ports 131 into parallel beams. The N collimating lenses 143 are arranged at equal intervals in the X-axis direction. The first output unit 141 outputs the N measurement beams 144 to the predetermined space S1 via the N collimating lenses 143. That is, the N measurement beams 144 propagating through the predetermined space S1 are each parallel beams. Note that the following description will be given with the reference numeral 144 assigned to only the N measurement beams propagating through the predetermined space S1.

[0035] The first light receiving unit 145 receives the N measurement beams 144 after propagating through the predetermined space S1. The first light receiving unit 145 has N collimating lenses 146 arranged opposite the N collimating lenses 143 with the predetermined space S1 in between. The N collimating lenses 146 are arranged at different positions in the X-axis direction, similar to the N collimating lenses 143. The N collimating lenses 146 are arranged at equal intervals in the X-axis direction, similar to the N collimating lenses 143. The N collimating lenses 146 are arranged opposite the N collimating lenses 143 in the Y-axis direction. Therefore, the N measurement beams 144 converted into parallel beams by the N collimating lenses 143 and emitted parallel to the Y-axis direction from the N collimating lenses 143 are received by the first light receiving unit 145 via the N collimating lenses 146. As a result, the N measuring beams 144 are emitted parallel to each other and aligned at equal intervals in the X-axis direction in the predetermined space S1.

[0036] The third optical splitter 150 splits the reference light, which is one of the two beams split by the first optical splitter 120, into N reference beams. The third optical splitter 150 is, for example, an optical coupler or an optical splitter. The first optical splitter 120 and the third optical splitter 150 are optically connected by, for example, an optical fiber, and the third optical splitter 150 receives the reference light emitted from the first emission port 121 of the first optical splitter 120 via the optical fiber.

[0037] The N optical couplers 161-168 each combine the N measurement beams 144 received by the first light-receiving unit 145 with the N reference beams in a one-to-one relationship. The N optical couplers 161-168 are, for example, optical couplers. The first light-receiving unit 145 and the N optical couplers 161-168 are optically connected by, for example, optical fibers, and the N optical couplers 161-168 each receive the N measurement beams 144 emitted from the first light-receiving unit 145 via the optical fibers. The N output ports 151 of the third optical branching unit 150 and the N optical couplers 161-168 are optically connected by, for example, optical fibers, and the N optical couplers 161-168 each receive the N reference beams emitted from the N output ports 151 of the third optical branching unit 150 via the optical fibers. For example, each of the N optical couplers 161 to 168 combines one of the N measurement beams 144 with one of the N reference beams. The N measurement beams 144 are likely to have different characteristics, and the N reference beams have the same characteristics.

[0038] The N photodetectors 171-178 receive the N combined light beams combined by the N optical couplers 161-168, respectively, and detect interference between the measurement light and the reference light. That is, the photodetector 171 detects interference between the measurement light and the reference light combined by the optical coupler 161. The photodetector 172 detects interference between the measurement light and the reference light combined by the optical coupler 162. The photodetector 173 detects interference between the measurement light and the reference light combined by the optical coupler 163. The photodetector 174 detects interference between the measurement light and the reference light combined by the optical coupler 164. The photodetector 175 detects interference between the measurement light and the reference light combined by the optical coupler 165. The photodetector 176 detects interference between the measurement light and the reference light combined by the optical coupler 166. The photodetector 177 detects interference between the measurement light and the reference light combined by the optical coupler 167. The photodetector 178 detects interference between the measurement light and the reference light combined by the optical coupler 168. Each of the N photodetectors 171 to 178 is a photoelectric conversion element, such as a photodiode or an image sensor. That is, each of the N photodetectors 171 to 178 outputs a detection signal obtained by converting the optical interference into an electrical signal.

[0039] The control unit 180 controls the directivity of sound collection based on the N detection signals output from the N photodetectors 171 to 178. The control unit 180 has an AD (Analog to Digital) converter 181 and a signal processor 182.

[0040] The AD converter 181 converts the N detection signals output by the N photodetectors 171-178 into analog to digital (AD) signals.

[0041] The signal processor 182 processes the N detection signals to control the directivity of collecting sound propagating in the predetermined space S1. The signal processor 182 processes the N detection signals output from the N photodetectors 171 to 178 to control the directivity of collecting sound along the arrangement direction of the N measurement beams 144, that is, the X-axis direction. For example, the signal processor 182 controls the directivity of collecting sound so as to acquire sound from one arrival direction within an angle range D1 extending in the X-axis direction with respect to a reference point in the predetermined space S1 in FIG. 1. This arrival direction is a direction having components in the X-axis direction in which the N measurement beams 144 are arranged in the predetermined space S1, and the Z-axis direction.

[0042] FIG. 3 is a diagram showing the relationship between the optical microphone according to the first embodiment and the direction from which a sound source comes.

[0043] 3 correspond to the positions from which the eight measurement beams 144 are emitted. When sound is detected using N measurement beams 144 arranged at equal intervals in the X-axis direction, as in the optical microphone 100, sound from an arrival direction tilted at an angle θ with respect to the X-axis direction is first detected by the measurement beam 144 at position P8, and then detected sequentially at each time Δt by the measurement beam 144 at positions P7, P6, P5, P4, P3, P2, and P1. This is because the eight positions P1 to P8 of the N measurement beams 144 are arranged at equal intervals d. From these facts, the following equation 1 holds when the speed of sound is V.

[0044] Δt=d·cosθ / V (Equation 1)

[0045] FIG. 4 is a diagram for explaining signal processing of the optical microphone according to the first embodiment.

[0046] As shown in Fig. 3, sound from an arrival direction tilted at an angle θ with respect to the X-axis direction is first detected by measurement light 144 at position P8, and is then detected in sequence at other positions P7 to P1 with delays of time Δt each. Therefore, the control unit 180 can detect sound from an arrival direction tilted at an angle θ with respect to the X-axis direction by adding data 1 to 8 as the obtained eight detection signals, with the other data 7 to 1 each delayed at time intervals Δt from data 8. For example, the signal processor 182 can detect sound from an arrival direction tilted at an angle θ with respect to the X-axis direction by adding data 1 to 8 indicated by the dashed line in Fig. 4.

[0047] The optical microphone 100 according to this embodiment includes a light source 110, a first optical splitter 120, a second optical splitter 130, a first emitting unit 141, a first light receiving unit 145, a third optical splitter 150, N optical couplers 161-168, N photodetectors 171-178, and a control unit 180. The first optical splitter 120 splits the light emitted from the light source 110 into reference light and measurement light. The second optical splitter 130 splits the measurement light into N measurement light beams (N is an integer equal to or greater than 2). The first emitting unit 141 emits the N measurement light beams from different positions toward a predetermined space S1. The first light receiving unit 145 receives the N measurement light beams 144 after propagating through the predetermined space S1. The third optical splitter 150 splits the reference light into N reference light beams. The N optical couplers 161-168 each combine the N measurement light beams and the N reference light beams received by the first light receiving unit 145 in a one-to-one relationship. The N photodetectors 171-178 each receive the N combined light beams combined by the N optical couplers 161-168 and detect interference between the measurement light beams and the reference light beams. The control unit 180 processes the N detection signals output from the N photodetectors 171-178 to control the directionality of sound collection.

[0048] According to this, N measurement beams are passed through a predetermined space S1 for detecting sound, and the N measurement beams 144 modulated by the air density caused by the sound propagating through the air in the predetermined space S1 are detected to detect interference with the reference beam, and the N detection signals obtained thereby are processed to detect sound at N different positions P1 to P8. Therefore, the directivity of sound collection can be controlled so that sound can be detected from an arrival direction tilted at an angle to the arrangement direction of the N measurement beams 144 with the predetermined space S1 as the reference.

[0049] Furthermore, in the optical microphone 100 according to this embodiment, the first emission unit 141 has N collimating lenses 143 arranged at different positions from one another and converting each of the N measurement beams into parallel beams. The first light receiving unit 145 has N collimating lenses 146 arranged opposite the N collimating lenses 143 across a predetermined space S1. The N collimating lenses 146 each receive the N measurement beams 144 converted into parallel beams by the N collimating lenses 143. This allows the N measurement beams 144 propagating within the predetermined space S1 to be converted into parallel beams, thereby effectively detecting the density of air caused by the propagating sound.

[0050] Furthermore, in the optical microphone 100 according to this embodiment, the N collimating lenses 143 and the N collimating lenses 146 may be arranged so that the N measurement beams 144 converted into parallel beams are aligned parallel and at equal intervals in the predetermined space S1. In this case, it is possible to easily detect sounds entering the predetermined space from directions tilted relative to the alignment direction of the N measurement beams. Furthermore, it is possible to reduce the processing load required for processing the N signals. Note that the surfaces of the collimating lenses 143 and 146 may be coated with an anti-reflection coating corresponding to the frequency of the light source 110.

[0051] (Modification of the first embodiment) The configuration of an optical microphone according to a modification of the first embodiment will be described.

[0052] FIG. 5 is a diagram illustrating a configuration of an optical microphone according to a modification of the first embodiment.

[0053] The optical microphone 200 according to the variation of the first embodiment differs from the optical microphone 100 according to the first embodiment in that it further includes an optical modulator 190 and in the configuration of the control unit 280. Therefore, the optical modulator 190 and the control unit 280 will be described below. Note that the same components as those in the optical microphone 100 according to the first embodiment are denoted by the same reference numerals, and description thereof will be omitted.

[0054] The optical modulator 190 modulates the reference light of the two lights split by the first optical splitter 120, and outputs the modulated reference light to the third optical splitter 150. The optical modulator 190 performs, for example, FM (Frequency Modulation) on the reference light.

[0055] Control unit 280 differs from control unit 180 according to the first embodiment in that it further includes FM (Frequency Modulation) demodulator 281.

[0056] The FM demodulator 281 demodulates the N detection signals output by the N photodetectors 171 to 178. The FM demodulator 281 outputs the N detection signals after demodulation to the AD converter 181.

[0057] According to this, the reference light is modulated by the optical modulator 190, a detection signal obtained by detecting the interference between the modulated reference light and the measurement light is demodulated, and signal processing is performed using the demodulated detection signal, thereby enabling effective sound detection. For example, an acousto-optic element (AOM), an electro-optic modulator (EOM), or the like can be used as the optical modulator 190. Furthermore, instead of using the optical modulator 190, a direct modulation method in which modulation is applied directly to a light source may be used as a method for modulating light.

[0058] (Embodiment 2) The configuration of the optical microphone according to the second embodiment will be described.

[0059] Fig. 6 is a perspective view for explaining an outline of the optical microphone according to the embodiment 2. In Fig. 6, only the frame member 340 of the optical microphone 300 is shown.

[0060] The optical microphone 300 differs from the optical microphone 100 according to the first embodiment in that it detects sound by selectively switching between N measurement beams 344 aligned in the X-axis direction and parallel to the Y-axis direction and M measurement beams 354 aligned in the Y-axis direction and parallel to the X-axis direction. That is, the optical microphone 300 can selectively detect sound at N different positions in the X-axis direction or M different positions in the Y-axis direction. This allows the optical microphone 300 to selectively detect, from among sounds propagating through a predetermined space S1, a sound from an arrival direction having an X-axis component or a sound from an arrival direction having a Y-axis component of the sound.

[0061] 7 and 8 are diagrams showing the configuration of an optical microphone according to the second embodiment. FIG. 7 is a diagram showing a case where the optical switch 310 is in a first state. (a) of FIG. 7 is a diagram showing the configuration of the optical microphone 300 when the optical switch 310 is in the first state, and (b) of FIG. 7 is a diagram showing the optical switch 310 in the first state. (a) of FIG. 8 is a diagram showing the configuration of the optical microphone 300 when the optical switch 310 is in a second state, and (b) of FIG. 8 is a diagram showing the optical switch 310 in the second state.

[0062] The optical microphone 300 includes a light source 110, a first optical splitter 120, an optical switch 310, a second optical splitter 130, a fourth optical splitter 320, a frame-shaped member 340, a third optical splitter 150, N optical couplers 361 to 368, N photodetectors 171 to 178, and a control unit 180.

[0063] The following describes the configurations that are different from the optical microphone 100 according to the first embodiment, and the same reference numerals are used for the common configurations, and the description thereof will be omitted.

[0064] The optical switch 310 selectively switches the destination of the measurement light emitted from the first optical splitter 120 to one of the first and second destinations. As shown in Fig. 7(b) and Fig. 8(b), the optical switch 310 has an optical path switching unit 311, an input port 312, a first output port 313, and a second output port 314.

[0065] The optical path switching unit 311 is a mirror that reflects the measurement light. When the optical switch 310 is in the first state, the optical path switching unit 311 is maintained in an orientation substantially parallel to the optical path from the input port 312 to the first output port 313 of the optical switch 310 so as not to block the optical path. As a result, the optical switch 310 emits the measurement light from the first output port 313 in the first state. When the optical switch 310 is in the second state, the optical path switching unit 311 is maintained in an orientation that intersects the optical path from the input port 312 to the first output port 313 of the optical switch 310. As a result, the measurement light incident from the input port 312 is reflected by the optical path switching unit 311 toward the second output port 314. As a result, the optical switch 310 emits the measurement light from the second output port 314 in the second state.

[0066] The second optical splitter 130 splits the measurement light emitted from the first output port 313 of the optical switch 310 in the first state into N (eight in this embodiment) measurement light beams. The configuration of the second optical splitter 130 is the same as that of the first embodiment. The first output port 313 of the optical switch 310 and the second optical splitter 130 are optically connected by, for example, an optical fiber, and the second optical splitter 130 receives the light emitted from the first output port 313 of the optical switch 310 via the optical fiber.

[0067] The fourth optical splitter 320 splits the measurement light emitted from the second output port 314 of the optical switch 310 in the second state into M (eight in this embodiment) measurement light beams. Note that N and M may be the same as long as they are integers equal to or greater than 2. Also, M may be a number smaller than N. The fourth optical splitter 320 is, for example, an optical coupler or an optical splitter. The configuration of the fourth optical splitter 320 is the same as that of the second optical splitter 130. Note that the second output port 314 of the optical switch 310 and the fourth optical splitter 320 are optically connected by, for example, an optical fiber, and the fourth optical splitter 320 receives the light emitted from the second output port 314 of the optical switch 310 via the optical fiber.

[0068] The frame-shaped member 340 has, for example, a square shape. The frame-shaped member 340 has a first emission section 341 that forms one side on the positive side in the Y axis direction, a first light receiving section 345 that forms one side on the negative side in the Y axis direction, a second emission section 351 that forms one side on the negative side in the X axis direction, and a second light receiving section 355 that forms one side on the positive side in the X axis direction. The first emission section 341, the first light receiving section 345, the second emission section 351, and the second light receiving section 355 surround a predetermined space S1. Note that frame-shaped member 340 is a member for arranging first emission section 341 and first light receiving section 345 so that they face each other in the Y-axis direction with a predetermined space S1 between them, and second emission section 351 and second light receiving section 355 so that they face each other in the X-axis direction with a predetermined space S1 between them, but is not limited to this configuration as long as first emission section 341 and first light receiving section 345 are arranged to face each other in the Y-axis direction, and second emission section 351 and second light receiving section 355 are arranged to face each other in the X-axis direction. In frame-shaped member 340, predetermined space S1 and an external space are in communication with each other, so that sound from a sound source in the external space propagates through the air and then propagates through predetermined space S1.

[0069] The second optical splitter 130 and the first output unit 341 are optically connected by, for example, N optical fibers, and the first output unit 341 receives the N measurement beams output from the N output ports 131 of the second optical splitter 130 via the N optical fibers. The first output unit 341 receives the N measurement beams split by the second optical splitter 130 and outputs N measurement beams 344 from different positions toward a predetermined space S1, as shown in FIG. 7A. The first output unit 341 is arranged at different positions in the X-axis direction and includes N collimating lenses 343 that convert the N measurement beams received from the N output ports 131 into parallel beams. The N collimating lenses 343 are arranged at equal intervals in the X-axis direction. The first output unit 341 outputs the N measurement beams 344 to the predetermined space S1 via the N collimating lenses 343. That is, the N measurement beams 344 propagating through the predetermined space S1 are each parallel beams. Note that the following description will be given with reference numeral 344 assigned to only the N measurement beams propagating through the predetermined space S1.

[0070] The fourth optical splitter 320 and the second output unit 351 are optically connected by, for example, M optical fibers, and the second output unit 351 receives the M measurement beams output from the M output ports 321 of the fourth optical splitter 320 via the M optical fibers. The second output unit 351 receives the M measurement beams split by the fourth optical splitter 320 and outputs M measurement beams 354 from different positions toward a predetermined space S1, as shown in FIG. 8(a). The second output unit 351 has M collimating lenses 353 arranged at different positions in the Y-axis direction and converting the M measurement beams received from the M output ports 321 into parallel beams. The M collimating lenses 353 are arranged at equal intervals in the Y-axis direction. The second output unit 351 outputs the M measurement beams 354 to the predetermined space S1 via the M collimating lenses 353. That is, each of the M measurement beams 354 propagating through the predetermined space S1 is a parallel beam. Note that the following description will be given with the reference numeral 354 assigned to only the M measurement beams propagating through the predetermined space S1.

[0071] The first light receiving unit 345 receives the N measurement beams 344 after propagating through the predetermined space S1. The first light receiving unit 345 has N collimating lenses 346 arranged opposite the N collimating lenses 343 with the predetermined space S1 in between. The N collimating lenses 346 are arranged at different positions in the X-axis direction, similar to the N collimating lenses 343. The N collimating lenses 346 are arranged at equal intervals in the X-axis direction, similar to the N collimating lenses 343. The N collimating lenses 346 are arranged opposite the N collimating lenses 343 in the Y-axis direction. Therefore, the N measurement beams 344 converted into parallel beams by the N collimating lenses 343 and emitted parallel in the Y-axis direction from the N collimating lenses 343 are received by the first light receiving unit 345 via the N collimating lenses 346. As a result, the N measurement beams 344 are emitted parallel to each other and aligned at equal intervals in the X-axis direction in the predetermined space S1.

[0072] The second light receiving unit 355 receives the M measurement beams 354 after propagating through the predetermined space S1. The second light receiving unit 355 has M collimating lenses 356 arranged opposite the M collimating lenses 353 with the predetermined space S1 in between. The M collimating lenses 356 are arranged at different positions in the Y-axis direction, similar to the M collimating lenses 353. The M collimating lenses 356 are arranged at equal intervals in the Y-axis direction, similar to the M collimating lenses 353. The M collimating lenses 356 are arranged opposite the M collimating lenses 353 in the X-axis direction. Therefore, the M measurement beams 354 converted into parallel beams by the M collimating lenses 353 and emitted parallel to the Y-axis direction from the M collimating lenses 353 are received by the second light receiving unit 355 via the M collimating lenses 356. As a result, the M measuring beams 354 are emitted parallel to each other and aligned at equal intervals in the Y-axis direction in the predetermined space S1.

[0073] The first emission direction of the N measurement beams 344 emitted by the first emission unit 341 is the Y-axis direction, and the second emission direction of the M measurement beams 354 emitted by the second emission unit 351 is the X-axis direction. That is, the first emission direction and the second emission direction intersect (for example, are perpendicular to) each other.

[0074] When the optical switch 310 is in the first state, the N optical couplers 361 to 368 each couple the N measurement beams 344 received by the first light-receiving unit 345 with the N reference beams in a one-to-one relationship. When the optical switch 310 is in the second state, the N optical couplers 361 to 368 each couple the M measurement beams 354 received by the second light-receiving unit 355 with the N reference beams in a one-to-one relationship. In this embodiment, when the optical switch 310 is in the second state, N and M are both 8, so that eight measurement beams 354 and eight reference beams are coupled in a one-to-one relationship. If N and M are different numbers, the smaller number of measurement beams and the larger number of reference beams are coupled in a one-to-one relationship. That is, each of the smaller number of measurement beams is coupled with a reference beam in a one-to-one relationship without omission. The N optical couplers 361 to 368 are, for example, optical couplers.

[0075] The first light receiving unit 345 and the N optical couplers 361 to 368 are optically connected by, for example, optical fibers, and the N optical couplers 361 to 368 each receive the N measurement beams 344 emitted from the first light receiving unit 345 via the optical fibers. The second light receiving unit 355 and the N optical couplers 361 to 368 are optically connected by, for example, optical fibers, and the N optical couplers 361 to 368 each receive the M measurement beams 354 emitted from the second light receiving unit 355 via the optical fibers. The N output ports 151 of the third optical branching unit 150 and the N optical couplers 361 to 368 are optically connected by, for example, optical fibers, and the N optical couplers 361 to 368 each receive the N reference beams emitted from the N output ports 151 of the third optical branching unit 150 via the optical fibers. For example, each of the N optical couplers 361 to 368 combines one of the N measurement beams 344 or one of the M measurement beams with one of the N reference beams. The N measurement beams 344 are likely to have different characteristics, the M measurement beams 354 are likely to have different characteristics, and the N reference beams have the same characteristics.

[0076] The N photodetectors 171-178 receive the N combined light beams combined by the N optical couplers 361-368, respectively, and detect interference between the measurement light and the reference light. That is, the photodetector 171 detects interference between the measurement light and the reference light combined by the optical coupler 361. The photodetector 172 detects interference between the measurement light and the reference light combined by the optical coupler 362. The photodetector 173 detects interference between the measurement light and the reference light combined by the optical coupler 363. The photodetector 174 detects interference between the measurement light and the reference light combined by the optical coupler 364. The photodetector 175 detects interference between the measurement light and the reference light combined by the optical coupler 365. The photodetector 176 detects interference between the measurement light and the reference light combined by the optical coupler 366. The photodetector 177 detects interference between the measurement light and the reference light combined by the optical coupler 367. The photodetector 178 detects interference between the measurement light and reference light combined by the optical coupler 368. Each of the N photodetectors 171 to 178 is a photoelectric conversion element, such as a photodiode or an image sensor. That is, each of the N photodetectors 171 to 178 outputs a detection signal obtained by converting the optical interference into an electrical signal.

[0077] The signal processor 382 of the control unit 180 processes the N detection signals to control the directivity of collecting sound propagating in the predetermined space S1. The signal processor 382 controls the optical switch 310 to the first state and processes the N detection signals output from the N photodetectors 171 to 178 when the measurement light is emitted from the first exit 313, thereby controlling the directivity of collecting sound along the arrangement direction of the N measurement light, i.e., the X-axis direction. For example, the signal processor 382 controls the directivity of collecting sound so as to acquire sound from one first arrival direction within an angle range D1 extending in the X-axis direction with respect to a reference point in the predetermined space S1 in FIG. 6 . This first arrival direction is a direction having components in the X-axis direction and the Z-axis direction in which the N measurement light beams 344 are arranged in the predetermined space S1.

[0078] Furthermore, the signal processor 382 controls the optical switch 310 to the second state and processes the M detection signals output from the M photodetectors 171-178 when the measurement light is emitted from the second exit 314, thereby controlling the directivity of the sound collection along the arrangement direction of the M measurement light, i.e., the Y-axis direction. The signal processor 382 controls the directivity of the sound collection so as to acquire sound from one second arrival direction within an angle range D2 extending in the Y-axis direction with respect to a reference point in the predetermined space S1 in FIG. 6 . This second arrival direction is a direction having components in the Y-axis direction and the Z-axis direction in which the M measurement light beams 354 are arranged in the predetermined space S1.

[0079] The optical microphone 300 according to the present embodiment can selectively control the directivity of sound collection so as to selectively detect a sound from a first arrival direction tilted in the X-axis direction where the N measurement beams 344 are arranged, and a sound from a second arrival direction tilted in the Y-axis direction where the M measurement beams 354 are arranged. This makes it possible to more accurately identify the direction of the sound source.

[0080] Although the above example is designed to detect the direction of sound arrival along two axes, the X and Y axes, it is also possible to add the Z axis to detect the direction of sound arrival along three or more axes.The microphone array itself may also be moved by an actuator to enable scanning of the direction of sound arrival.

[0081] While the optical microphone according to one or more aspects of the present disclosure has been described above based on the embodiments, the present disclosure is not limited to these embodiments. As long as they do not deviate from the spirit of the present disclosure, various modifications conceivable by those skilled in the art to the present embodiments and configurations constructed by combining components of different embodiments may also be included within the scope of one or more aspects of the present disclosure. [Industrial Applicability]

[0082] The present disclosure is useful as an optical microphone or the like that can identify the direction to a sound source. [Explanation of symbols]

[0083] 100, 200, 300 Optical Microphones 110 Light source 120 First optical splitter 130 Second optical splitter 131 N exit ports 140, 340 Frame-shaped member 141, 341 First exit 143, 146, 343, 346 N collimating lenses 144, 344 N measurement beams 145, 345 1st light receiving section 148, 149 Two pieces 150 Third Optical Splitter 151 N exit ports 161~168 N optical couplers 171~178 N photodetectors 180, 280, 380 control section 181 AD converter 182, 382 signal processor 190 Optical Modulator 281 FM Demodulator 310 Optical Switch 311 Optical path switching unit 312 Inlet 313 First Exit 314 Second Exit 320 Fourth Optical Splitter 321 M exit ports 351 Second exit section 353, 356 M collimating lenses 354 M measurement beams 355 2nd light receiving section D1, D2 angle range S1 Prescribed space

Claims

1. A light source and a first optical splitter that splits the light emitted from the light source into reference light and measurement light; a second optical splitter that splits the measurement light into N measurement light beams (N is an integer of 2 or more); a first emitting unit that emits the N measurement beams from different positions toward a predetermined space; a first light receiving unit that receives the N measurement light beams after propagating through the predetermined space; a third optical splitter that splits the reference light into N reference light beams; N optical couplers that respectively couple the N measurement light beams received by the first light receiving unit with the N reference light beams in a one-to-one relationship; N photodetectors that receive the N combined light beams combined by the N optical couplers, respectively, and detect interference between the measurement light beam and the reference light beam; and a control unit that controls the directionality of sound collection by processing the N detection signals output from the N photodetectors. the N measurement beams are arranged parallel to each other and at equal intervals in the predetermined space; the control unit adds the N detection signals in order with delays at predetermined time intervals. Optical microphone.

2. Detecting a sound coming from an arrival direction tilted at an angle θ with respect to the arrangement direction of the N measurement beams; When the interval between the N measurement beams is d, the predetermined time interval is Δt, and the sound speed is V, Δt=d・cosθ / V Satisfy the relationship of 2. The optical microphone according to claim 1.

3. the first exit unit includes N first collimator lenses arranged at different positions from each other and converting the N measurement beams into parallel beams, respectively; the first light receiving unit has N second collimating lenses arranged opposite the N first collimating lenses with the predetermined space therebetween, The N second collimating lenses respectively receive the N measurement beams converted into parallel beams by the N first collimating lenses.

3. The optical microphone according to claim 1 or 2.

4. The N first collimating lenses and the N second collimating lenses are arranged so that the N measurement beams converted into parallel beams are arranged parallel and at equal intervals in the predetermined space.

4. The optical microphone according to claim 3.

5. moreover, an optical modulator that modulates the reference light and outputs the modulated reference light to the third optical branching device; The control unit an FM (Frequency Modulation) demodulator that demodulates the N detection signals; an AD converter that performs AD (Analog to Digital) conversion on the N detection signals; a signal processor that performs the signal processing on the N AD converted detection signals; 5. The optical microphone according to claim 1.

6. moreover, an optical switch that selectively switches the destination of the measurement light emitted from the first optical branching device to one of a first exit optically connected to the second optical branching device and a second exit; a fourth optical splitter that splits the measurement light emitted from the second exit port into M measurement light beams (M is an integer of 2 or more and N or less); a second output unit that outputs the N measurement beams split by the fourth optical splitter from different positions toward the predetermined space; a second light receiving unit that receives the M measurement light beams after propagating through the predetermined space, a first emission direction of the N measurement beams emitted by the first emission unit and a second emission direction of the M measurement beams emitted by the second emission unit intersect with each other; M optical couplers among the N optical couplers respectively couple the M measurement light beams received by the second light receiving unit with M reference light beams among the N reference light beams in a one-to-one relationship; M photodetectors among the N photodetectors receive the M combined light beams combined by the M optical couplers, respectively, and detect interference between the measurement light beam and the reference light beam, respectively; The control unit (i) controlling the optical switch to emit the measurement light to the first exit, and processing the N detection signals output from the N photodetectors to control the directivity of the sound collection along the arrangement direction of the N measurement light; (ii) controlling the optical switch to emit the measurement light from the second exit port, and processing M detection signals output from the M photodetectors to control the directivity of the sound collection along the arrangement direction of the M measurement light; 6. An optical microphone according to claim 1.

7. the M measurement beams are arranged parallel to each other and at equal intervals in the predetermined space; the control unit adds the M detection signals in order with delays at predetermined time intervals.

7. The optical microphone according to claim 6.

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