JP2000078695A - Directional optical microphone - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide the microphone low in cost and high in directionality by providing plural transparent vibration films which transmit a light beam of a semiconductor laser in a straight advance direction of the light beam and providing a bi-sected light position sensor for detecting its reflected light beam. SOLUTION: At the time of sound wave made incident from a vertical direction into a longitudinal direction of a cylindrical object 12, a sound wave phase surface 16 becomes parallel to an arrangement direction of plural transparent vibration films 13, each of the transparent vibration films 13 starts vibrating at the same time, and a position of a laser beam 15 irradiated there changes. Thus, an irradiation position for a bi-secting sensor 14 composed of diodes 18 and 19 of a reflection laser beam 17 changes and a detection output dealing with vibration change is outputted from a differential amplifier 20. This output is added and a sound wave only from the vertical direction is selectively detected in the longitudinal direction of the cylindrical object 12. Also, since sound waves other than from this direction are made incident to each of the transparent vibration films 13 in a different timing, an S/N lowers by interference of the detection output and the output is not recognized as significant voice information when the detection output of the bi-secting sensor 14 is simultaneously added.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a directional optical microphone, and more particularly to a directional optical microphone using a laser beam for use as an interface means utilizing voice recognition between a computer and a human. It relates to an optical microphone.

[0002]

2. Description of the Related Art With the spread of personal computers in recent years, it has become increasingly important to provide a smooth interface between a computer and a human. As an interface means instead of a conventional keyboard, a voice capable of easily inputting information is used. Recognition is attracting attention as a powerful means in the future.

FIG. 7 is a diagram schematically illustrating the use of an interface using voice recognition. In this example, a human speaks words, and a computer detects the meaning of the words and asks the humans to ask them back. Operation.

At present, software that can be operated by a personal computer has been easily available. By using such voice recognition,
Control and typing of electronic devices can be performed more easily, and it becomes very easy for visually impaired persons to use electronic devices such as computers.

In such an interface using voice recognition, in order to input voice to a computer,
Usually, a microphone is used, and in particular, it is common to use a wearable microphone that supports the microphone using its head like a headphone.

In this system, the distance between the microphone and the mouth can be kept constant, so that a voice signal of a certain size can be input, but the head and the microphone support are in close contact during use. There are problems such as discomfort.

On the other hand, when the microphone is placed at a position about 30 cm away from the mouth, the voice signal intensity is inversely proportional to the square of the distance, so that the word signal output becomes weak, and as a result, noise from surroundings is reduced. The effect cannot be ignored, and the ability to recognize words will be significantly degraded.

In order to cope with such a problem of the attenuation of the audio signal strength, conventionally, a high-sensitivity directional microphone or an electrical signal processing is used to detect the audio signal at a place remote from the source. Such a conventional directional microphone will be described with reference to FIG.

FIG. 8A is a schematic configuration diagram of a normal directional microphone using a cylinder. The microphone main body 31 is placed at the end of a cylinder 32 provided with a hole 33. In a certain direction, ie
Only the sound wave 34 coming from the longitudinal direction of the cylinder 32 is selectively detected.

In this case, the sound wave 34 coming from the longitudinal direction of the cylinder 32 is taken in from the hole 33 and propagates in the cylinder 32 as a sound wave 35. In this case, the traveling direction of the sound wave 34 and the traveling of the taken sound wave 35 Since the directions are the same, the phase of the sound wave 35 traveling in the cylinder 32 and the newly introduced sound wave 35 in the traveling direction are substantially synchronized, and as a result, the sound wave 34 is a form in which the sound wave 35 is superimposed. To reach the microphone body 31.

On the other hand, a sound wave coming from a direction not parallel to the longitudinal direction of the cylinder 32, for example, the sound wave 36 is also introduced into the cylinder 32 through the hole 33. In this case, the traveling direction of the sound wave 36 and the introduced sound wave Since the traveling directions of the sound waves 35 are different, the phases of the sound waves 35 traveling in the cylinder 32 and the newly introduced sound waves 35 in the traveling direction are different. As a result, the sound waves 35 interfere with each other and are attenuated. Therefore, the microphone information is not detected by the microphone body 31 as audio information.

FIG. 8 (b) is a conceptual configuration diagram of an array microphone. A plurality of microphones 41 are spatially separated from each other, and the signal waveform detected by each microphone has a phase difference. By adding an appropriate phase difference using the generation and addition circuit 32 or the like, only sound waves coming from a specific direction are added and detected. In the drawing, reference numeral 43 denotes a phase plane of the sound wave, and the entering direction of the sound wave is perpendicular to the phase plane 43 of the sound wave.

On the other hand, the detection outputs are added at random to the sound waves from the directions where the phase differences do not match, so that the sound waves are attenuated by mutual interference and are not detected as sound information as a whole. Become.

[0014]

However, in the case of a directional microphone as shown in FIG.
Is as large as 40 cm, which is too large for a microphone to be installed between a computer and a human.

Further, in the case of the array microphone shown in FIG. 8B, since a plurality of microphones are spatially arranged, there is an essential problem that the microphone cannot be spatially compact. Phase difference generation and addition circuit 4
There is also a problem that a second circuit and an integrating circuit are required.

Therefore, an object of the present invention is to provide a compact and inexpensive microphone with high directivity.

[0017]

FIG. 1 is an explanatory view of the principle configuration of the present invention. Referring to FIG. 1, means for solving the problems in the present invention will be described. See FIG. 1 (1) In the present invention, in a directional optical microphone, a plurality of transparent vibrating films 3 transmitting the light beam 5 are arranged in a direction in which the light beam 5 of the semiconductor laser 1 goes straight,
A plurality of light beam position sensors 4 for detecting a reflected light beam 7 from the transparent vibration film 3 are provided.

With such a configuration, sound waves are transmitted to the transparent vibrating membrane 3.
Is applied to the transparent vibrating film 3, the irradiation position of the reflected light beam 7 reflected from the transparent vibrating film 3 changes, and the position change is detected by the light beam position sensor 4, whereby the acoustic wave is detected. Can detect the amplitude change of
By arranging such detecting means in an array along the traveling direction of the light beam 5, sound waves coming from a specific direction can be obtained.
In the drawing, only the sound wave from the light beam 5 in the straight traveling direction and the perpendicular direction, that is, only the sound wave having a phase plane of 6
/ N ratio can be selectively increased. Reference numeral 2 denotes a cylindrical body that supports the transparent vibrating membrane 3.

(2) In the present invention, in the above (1), means for adding a phase difference to the detection output of each light beam position sensor 4 and means for adding the detection output for adding the phase difference are provided. It is characterized by.

As described above, by providing the means for adding a phase difference to the detection output and the means for adding the detection output for adding the phase difference, the phase difference can be set arbitrarily, and only the sound wave coming from any specific direction can be set. Can be selectively increased.

(3) Further, according to the present invention, in a directional optical microphone, a plurality of vibrating films are arranged in an array, and a light beam 5 reflected by each vibrating film is sequentially incident on the next-stage vibrating film. Means, and a light beam position sensor 4 for detecting a light beam 5 from the vibrating film or the reflecting means is provided.

With such a configuration, when a sound wave is applied to the vibrating membrane, the vibrating membrane vibrates, and the light beam 5 whose position has been changed by the vibration is sequentially incident on the next vibrating membrane and the vibration component is added. Therefore, by detecting the added output, it is possible to selectively increase the S / N ratio of only a sound wave coming from a specific direction.

(4) Further, according to the present invention, in the above (3), a light beam position sensor 4 for detecting a transmitted light beam 5 from the beam splitter corresponding to each beam splitter using a beam splitter as the reflection means. And a difference detection circuit for detecting a difference between the detection outputs of the adjacent light beam position sensors 4.

With such a configuration, only the sound waves coming from the direction perpendicular to the array direction of the array, that is, the sound waves coming from the direction in which the sound waves reach the respective vibrating membranes at the same time, are added. By arbitrarily selecting the direction, it is possible to selectively increase the S / N ratio of only sound waves coming from any specific direction.

(5) In the present invention, in the above (4), means for adding a phase difference to the difference detection output of the detection output of the adjacent light beam position sensor 4, and adding the detection output adding the phase difference Means for performing the operation.

As described above, even when the diaphragm is provided, the means for adding a phase difference to the detected output and the means for adding the detected output to which the phase difference has been added are provided, so that the phase difference can be arbitrarily set. , S / S of only sound waves coming from any specific direction
The N ratio can be selectively increased.

(6) Further, according to the present invention, in the above (3), a plurality of fixed reflecting mirrors are used as the reflecting means, and one light beam position sensor 4 is provided at a position where the last reflected light beam 7 is detected. Is provided.

By adopting such a configuration, the configuration is equivalent to adding a phase difference so as to detect only the sound waves coming from the direction in which the sound waves reach each of the vibrating films at the same time. Is arbitrarily selected, the S / N ratio of only a sound wave coming from any specific direction can be selectively increased, and in this case, only one light beam position sensor 4 is required, and Since a difference detection circuit and the like are not required, the configuration is simplified.

(7) According to the present invention, in the above (6), the plurality of vibrating membranes and the plurality of fixed reflecting mirrors are moved along the wavefronts having different phases of the sound waves that have become spherical waves.
It is characterized by being arranged respectively.

As described above, by disposing the plurality of vibrating membranes and the plurality of fixed reflecting mirrors along the wavefronts having different phases of the sound waves that have become spherical waves, the microphone can be placed on a display surface such as behind a keyboard. , And the sound collecting ability is improved.

[0031]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Here, first to fourth embodiments of the present invention will be described with reference to FIGS.
First, a directional optical microphone according to a first embodiment of the present invention will be described with reference to FIG. FIG. 2A is a schematic configuration diagram of a directional optical microphone according to the first embodiment of the present invention.
A cylindrical body 12 whose longitudinal direction is the longitudinal direction is arranged in the straight traveling direction of the laser beam 15 emitted from the substrate, the plurality of transparent vibrating films 13 are supported by the cylindrical body 12, and The two-divided optical sensors 14 are respectively arranged at the irradiation positions of the reflected laser beam 17.

FIG. 2B is a diagram showing the detailed configuration of the directional optical microphone according to the first embodiment of the present invention, and shows the reflection reflected from the hard transparent vibrating film 13. The laser beam 17 is applied to a two-part optical sensor 14 composed of a pair of photodiodes 18 and 19 arranged close to each other, and a change in the output of the pair of photodiodes 18 and 19 caused by a change in the irradiation position is detected. The dynamic amplifier 20 detects the difference.

In this case, in a state where the transparent vibrating film 13 is not vibrating, the reflected laser beam 17 is arranged so as to be evenly applied to the pair of photodiodes 18 and 19 arranged close to each other. Therefore, the output of the differential amplifier 20 when there is no vibration is zero.

The transparent vibrating film 13 may be made of a hard transparent plastic having a thickness of about several tens of μm or a transparent hard glass.
By setting the light reflectance of the laser beam 3 to about 4%, the attenuation of the laser beam 15 passing through the transparent vibration film 13 does not become a problem effectively.

Referring again to FIG. 2A, when a sound wave enters from a direction perpendicular to the longitudinal direction of the cylindrical body 12 of the directional optical microphone, the phase plane 16 of the sound wave
Are substantially parallel to the arrangement direction of the transparent vibration films 13, so that each of the transparent vibration films 13 starts to vibrate almost simultaneously. Laser beam 15 irradiated on transparent vibrating film 13 at the start of vibration
And the irradiation position of the reflected laser beam 17 on the two-divided optical sensor 14 changes accordingly, a detection output corresponding to the vibration change is obtained from the differential amplifier 20, and this differential amplification output is By the addition, only the sound wave from a direction perpendicular to the longitudinal direction of the cylindrical body 12 can be selectively detected.

On the other hand, sound waves from directions other than the direction perpendicular to the longitudinal direction of the cylindrical body 12 enter the transparent vibrating films 13 at different timings. Are added at the same time, the respective differential detection outputs interfere with each other, and the S / N ratio is greatly reduced, so that it is not recognized as significant audio information.

When it is desired to selectively detect only a sound wave from a specific direction other than the direction perpendicular to the longitudinal direction of the cylindrical body 12, the case of the conventional array microphone described with reference to FIG. Similarly, by providing a phase difference generation and addition circuit and the like, and adding a predetermined phase difference corresponding to the direction selected as a specific direction to the differential detection output from each of the two split optical sensors 14, from any direction Can be selectively detected.

By adopting such a configuration, the directional optical microphone having high directivity can be reduced in size. In particular, in a simple configuration in which a phase difference generating and adding circuit or the like is not provided, selective detection is performed. Since the direction of the sound wave is perpendicular to the longitudinal direction of the cylindrical body 12, by installing such a directional optical microphone at the back of the keyboard along the longitudinal direction of the keyboard, it is possible to reduce the height without requiring extra space. It can be a sensitive voice recognition interface. In this case, the cylindrical body 12 does not necessarily have to be cylindrical, and is not an essential component if there is a suitable support for the transparent vibrating membrane 13.

Next, a directional optical microphone according to a second embodiment of the present invention will be described with reference to FIGS. 3 and 4. In this case, instead of a transparent vibrating film, a vibrating film is used. In this case, a vibrating reflection mirror is used. FIG. 3 is a schematic configuration diagram of a directional optical microphone according to a second embodiment of the present invention. A laser beam 15 emitted from a semiconductor laser 11 is reflected by a first-stage vibrating reflection mirror 21. At the same time, a part of the reflected laser beam 17 is incident as a reflected laser beam 23 on the vibrating reflection mirror 21 at the next stage, and the remaining part of the reflected laser beam 17 is incident on the two-part optical sensor 14 as a transmitted laser beam 24. A beam splitter 22 is provided, and the detection output from the two-split optical sensor 14 is differentially amplified by a differential amplifier 20, and the outputs of adjacent differential amplifiers 20 are further processed by a differential amplifier 25 at a subsequent stage. Perform differential amplification.

FIG. 4 is a diagram showing a detailed configuration of a directional optical microphone according to a second embodiment of the present invention.
The reflected laser beam 17 reflected at 1 is incident on the beam splitter 22 and a part thereof is reflected by the reflected laser beam 23.
Is sent to the next stage vibration type reflection mirror (not shown),
The remainder is radiated as a transmitted laser beam 24 to a two-division optical sensor 14 composed of a pair of photodiodes 18 and 19 arranged in close proximity, and the output of the pair of photodiodes 18 and 19 caused by a change in the irradiation position is detected. The change is detected as a difference by the differential amplifier 20, and the detection principle of the two-segment optical sensor 14 is exactly the same as that of the first embodiment.

In this case, as the vibration-type reflection mirror 21, a hard metal thin film such as Ti or W is preferable in order to enhance the vibration efficiency. A metal thin film may be used.

Referring again to FIG. 3, sound waves are applied to the directional optical microphone in a direction perpendicular to the arrangement direction of the vibrating reflecting mirror 21, that is, in the drawing, a direction perpendicular to the main surface of the vibrating reflecting mirror 21. When the light enters, the arrival times of the sound waves on the same phase plane become the same at each of the vibrating reflecting mirrors 21. Therefore, the reflected laser beam from each of the vibrating reflecting mirrors 21 has the vibration component of the preceding stage on it. In the split optical sensor 14,
Each vibration component is superimposed according to the number of stages.

Accordingly, the differential amplifier 25 at the subsequent stage obtains the differential output of the output of the differential amplifier 20 at the adjacent stage, thereby extracting only the vibration component received from the sound wave by each of the vibration type reflection mirrors 21. By adding the differential amplified outputs, only the sound waves from the direction perpendicular to the arrangement direction of the vibrating reflection mirror 21 can be selectively detected.

On the other hand, sound waves from other directions enter the vibrating reflection mirror 21 at different timings. Therefore, when the differential outputs of the differential amplifier 25 at the subsequent stage are added, each differential output becomes Interference causes a significant reduction in the S / N ratio, and is not recognized as significant audio information.

In this case as well, the vibration type reflection mirror 2
When it is desired to selectively detect only a sound wave from a specific direction other than the arrangement direction 1, a phase difference generating and adding circuit and the like are provided as in the case of the conventional array microphone described with reference to FIG. By adding a predetermined phase difference corresponding to the selected direction to the differential output of the differential amplifier 25 at the subsequent stage, it is possible to selectively detect sound from an arbitrary direction.

By adopting such a configuration, the directional optical microphone having high directivity can be reduced in size as compared with the conventional array microphone. In particular, a hard metal thin film such as Ti is used as the vibration film. Therefore, the vibration efficiency is higher than that of the transparent vibration film 13 of the first embodiment, and the manufacturing is easy.

Next, a directional optical microphone according to a third embodiment of the present invention will be described with reference to FIG. FIG. 5 is a schematic configuration diagram of a directional optical microphone according to a third embodiment of the present invention. A laser beam 15 emitted from a semiconductor laser 11 is reflected by a first-stage vibrating reflection mirror 21. At the same time, the reflected laser beam 17 is reflected by the fixed-type reflecting mirror 26 as a reflected laser beam 23 and is incident on the vibrating reflecting mirror 21 at the next stage. This process is repeated for a plurality of stages. 14, and differentially amplifies the detection output from the split optical sensor 14 by the differential amplifier 20.

The configuration and detection principle of the two-part light sensor 14 in this case are exactly the same as those of the first embodiment, and the vibration type reflection mirror 21 is the same as that of the second embodiment. Similarly, to increase the vibration efficiency, Ti or W
Although a hard metal thin film such as Al is preferable, a metal thin film such as Al or Au may be used in consideration of the reflectivity or the ease of manufacturing. The fixed reflecting mirror 26 may be any one that can reflect the laser beam from the semiconductor laser 11 with high efficiency, and in some cases, the plurality of fixed reflecting mirrors 26 may be configured as an integrated reflecting mirror. It is a good thing.

When a sound wave enters the directional optical microphone in a direction perpendicular to the arrangement direction of the vibrating reflection mirror 21, that is, the phase plane 16 of the sound wave parallel to the main surface of the vibrating reflection mirror 21 in the figure. , The arrival time of the same sound wave on the phase surface 16 becomes simultaneous in each of the vibrating reflection mirrors 21, and each of the vibrating reflection mirrors 2
Since the reflected laser beam from 1 has a vibration component at the previous stage, it is possible to obtain one finally obtained two-split optical sensor 14.
Is the vibration component of each vibration-type reflecting mirror 21;
That is, since the synchronized vibration components are superimposed, only the sound waves coming from this direction can be selectively detected.

On the other hand, sound waves from other directions are incident on the vibrating reflection mirror 21 at different timings, so that the output of the two-split optical sensor 14 causes the vibration components of the respective vibration type reflection mirrors 21 to interfere with each other. As a result, the signal is superimposed and the S / N ratio is greatly reduced, so that it is not recognized as significant voice information.

In this case, a means for providing a phase difference cannot be provided, and the direction which can be selectively detected is limited to a direction perpendicular to the arrangement direction of the vibrating reflection mirror 21. Since only one is required and the phase difference generating and adding circuit is not required, the configuration is simplified, and thereby a spatially compact and inexpensive directional optical microphone can be realized. .

Next, a directional optical microphone according to a fourth embodiment of the present invention will be described with reference to FIG. 6. The principle of detection in this case is the same as that of the third embodiment. . FIG. 6 is a schematic configuration diagram of a directional optical microphone according to a fourth embodiment of the present invention.
7, that is, in consideration of the fact that the phase plane 16 of the sound wave normally emitted from a human mouth becomes a spherical wave, each of the vibrating reflection mirrors 21 and each of the fixed type reflection mirrors 26 are respectively converted to the spherical wave phase plane. It is arranged along.

In this case, it is necessary to adjust the intervals and the like so that a continuous series of reflections is performed between each of the vibrating reflecting mirrors 21 and each of the fixed reflecting mirrors 26. After repeating reflection with the reflection mirror 26, the final reflected laser beam 23 is incident on the two-piece optical sensor 14, and the detection output from the two-piece optical sensor 14 is differentially amplified by a differential amplifier (not shown). Things.

The configuration and detection principle of the two-part light sensor 14 in this case are exactly the same as those of the first embodiment, and the vibrating reflection mirror 21 and the fixed reflection mirror 26 are the same as those of the first embodiment. What is exactly the same as that of the third embodiment may be used.

In the fourth embodiment, since each of the vibrating reflection mirrors 21 is arranged along the same phase plane of the sound wave, the same sound wave of the same sound wave is formed as in the third embodiment. The arrival time of the phase plane 16 is determined by each of the vibrating reflecting mirrors
At the same time, the reflected laser beam 23 from each of the vibrating reflection mirrors 21 has a vibration component at the previous stage, so that the output of one finally obtained two-split optical sensor 14 is The vibration component at, that is,
Since the synchronized vibration components are superimposed, the sound from the sound source 27 can be efficiently collected.

In this case, similarly to the first embodiment, the phase plane of the sound wave that can be selectively detected coincides with the longitudinal direction of the directional optical microphone. By placing it on the display, an audio signal can be accurately input to a computer without requiring any special space.

In the fourth embodiment,
The final reflected laser beam 23 is transmitted to a fixed reflection mirror 26.
On the other hand, in the third embodiment described above, the final reflected laser beam 23 is obtained from the vibrating reflecting mirror 21. In either case, the reflected laser beam 23 may be obtained from any of the reflecting mirrors. Good thing.

Although the embodiments of the present invention have been described above, the present invention is not limited to the directional optical microphone for the voice recognition interface, but may be used as various microphones requiring high directivity. Is what is done.

[0059]

According to the present invention, since an array is formed by arranging a plurality of minute transparent vibrating films or vibrating reflecting mirrors, a directional optical microphone can be formed in a small size and at low cost. This greatly contributes to the spread of interfaces using voice recognition.

[Brief description of the drawings]

FIG. 1 is an explanatory diagram of a basic configuration of the present invention.

FIG. 2 is an explanatory diagram of a schematic configuration of a directional optical microphone according to the first embodiment of the present invention.

FIG. 3 is an explanatory diagram of a schematic configuration of a directional optical microphone according to a second embodiment of the present invention.

FIG. 4 is an explanatory diagram of a detailed configuration of a directional optical microphone according to a second embodiment of the present invention.

FIG. 5 is an explanatory diagram of a schematic configuration of a directional optical microphone according to a third embodiment of the present invention.

FIG. 6 is an explanatory diagram of a schematic configuration of a directional optical microphone according to a fourth embodiment of the present invention.

FIG. 7 is an explanatory diagram of a use state of an interface using voice recognition.

FIG. 8 is an explanatory diagram of a conventional directional microphone.

[Explanation of symbols]

 Reference Signs List 1 semiconductor laser 2 cylindrical body 3 transparent vibration film 4 light beam position sensor 5 light beam 6 sound wave phase plane 7 reflected light beam 11 semiconductor laser 12 cylindrical body 13 transparent vibration film 14 two-part light sensor 15 laser beam 16 sound wave Phase plane 17 Reflected laser beam 18 Photodiode 19 Photodiode 20 Differential amplifier 21 Vibrating reflective mirror 22 Beam splitter 23 Reflected laser beam 24 Transmitted laser beam 25 Differential amplifier 26 Fixed reflective mirror 27 Sound source 31 Microphone body 32 Cylindrical 33 Hole 34 sound wave 35 sound wave 36 sound wave 41 microphone 42 phase difference generating and adding circuit 43 phase plane of sound wave

Claims (7)

[Claims] 1. A plurality of light beam position sensors for arranging a plurality of transparent vibrating films transmitting the light beam in a direction in which the light beam of the semiconductor laser travels straight, and detecting a reflected light beam from the transparent vibrating film. A directional optical microphone comprising: 2. The directional light according to claim 1, further comprising means for adding a phase difference to the detection output of each of the light beam position sensors, and means for adding the detection output to which the phase difference has been added. microphone. 3. A plurality of vibrating films are arranged in an array, and a reflecting means for sequentially inputting light beams reflected by the vibrating films to a next vibrating film is provided, and light from the vibrating film or the reflecting means is provided. A directional optical microphone comprising a light beam position sensor for detecting a beam. 4. A beam splitter is used as said reflecting means, and a light beam position sensor is provided so as to detect a transmitted light beam from the beam splitter corresponding to each of said beam splitters. 4. The directional optical microphone according to claim 3, further comprising a difference detection circuit for detecting a difference between the detection outputs. 5. The apparatus according to claim 4, further comprising means for adding a phase difference to a difference detection output between the detection outputs of the adjacent light beam position sensors, and means for adding the detection output obtained by adding the phase difference. The directional optical microphone as described. 6. The pointing device according to claim 4, wherein a plurality of fixed-type reflecting mirrors are used as said reflecting means, and one light beam position sensor is provided at a position where a reflected light beam reflected last is detected. Sex microphone. 7. The method according to claim 6, wherein the plurality of vibrating films and the plurality of fixed reflecting mirrors are respectively arranged along wavefronts having different phases of sound waves that have become spherical waves. Directional optical microphone.