JP2001292498A - Acoustoelectric transducer - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a small-sized directive acoustoelectric transducer at a low cost. SOLUTION: The acoustoelectric transducer is provided with diaphragms 2a, 2b and 2c that are fixed independently of each other in a case 1 and vibrated by a sound pressure, a light source 3 emitting a light beam to the diaphragms 2a, 2b and 2c, and light receiving elements 4a, 4b and 4c that receive a reflecting light from the diaphragms 2a, 2b and 2c, and output a signal corresponding to the vibration of the respective diaphragms 2a, 2b and 2c.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an acoustoelectric converter, and more particularly to an acoustoelectric converter using a vertical cavity surface emitting laser diode (VCSEL) as a light emitting element.

[0002]

2. Description of the Related Art An optical microphone device is known as a miniature acoustoelectric conversion device using a VCSEL.
345438. It has also been proposed to construct a directional microphone device having a wide frequency bandwidth by combining a plurality of such optical microphone elements. However, in a conventional optical microphone device, even when a device is configured by combining a plurality of elements, a light-emitting element and a diaphragm are used in a one-to-one relationship, and thus a plurality of optical microphone devices may be combined. A combination of a pair of diaphragms and a light emitting element was required.

[0003]

In such an apparatus in which the relationship between the diaphragm and the light emitting element is 1: 1 as described above,
There were drawbacks such as that the diaphragm could not be arranged close to or that the shape became large. Therefore, it has been difficult to realize a small directional optical microphone device having a wide frequency characteristic. Also VCS
Since the EL light emitting element is expensive, using the same number of light emitting elements as the number of diaphragms is not preferable since it leads to an increase in cost. SUMMARY An advantage of some aspects of the invention is to solve the above-described problem, and to reduce the number of light-emitting elements by using a configuration in which a plurality of diaphragms can correspond to one light-emitting element. An object is to provide an acoustoelectric conversion device having a wide directivity.

[0004]

An acoustoelectric transducer according to the present invention comprises a plurality of diaphragms fixed independently of each other in a housing and vibrating by sound pressure, and a light source for irradiating the diaphragm with a light beam. And a plurality of light receiving elements that receive reflected light from the respective diaphragms and output signals corresponding to the vibrations of the respective diaphragms. The shapes of the plurality of diaphragms can be defined so that acoustic resonance frequencies are different from each other. Further, the plurality of diaphragms can be arranged on different planes or on the same plane. Further, the light source and the plurality of light receiving elements can be arranged on the same plane.

In the acoustoelectric conversion device, some of the plurality of diaphragms exhibit a half mirror effect. Further, in the acoustoelectric conversion device, the light beam may be distributed via a half mirror element disposed in the housing, and may be applied to the respective diaphragms. Further, the light source is preferably a vertical cavity surface emitting laser device.

[0006]

FIG. 1 is a cross-sectional view of an acoustoelectric converter according to an embodiment of the present invention. A plurality of diaphragms 2a, 2b, 2c are arranged in the vertical direction in a stepwise manner in the housing 1. The light emitting element 3 is mounted below the vibration plates arranged in the vertical direction. The light receiving elements 4a, 4b, 4 are placed on the same plane on which the light emitting element 3 is mounted.
c are arranged and mounted respectively. An opening 5 through which sound waves from the outside are incident is provided on the outer wall surface of the housing 1, the mounting members of the vibration plates 2a, 2b, 2c and the mounting plates of the light emitting element 3 and the light receiving elements 4a to 4c.
By providing such an opening 5, each diaphragm 2a
2b are configured to receive sound waves from the front and back surfaces. As a result, the optical microphone device has bidirectionality on the front and back surfaces of the diaphragm.

It is desirable to use a VCSEL as the light emitting element 3. The laser light emitted from the light emitting element 3 enters the diaphragm 2a, and a part of the laser light is reflected and enters the light receiving element 4a. A part of the light passes through the diaphragm 2a and is incident on the diaphragm 2b. The light incident on the diaphragm 2b is
Here also, a part of the light is reflected and enters the light receiving element 4b. The light transmitted through the diaphragm 2b is incident on the diaphragm 2c, reflected there, and incident on the light receiving element 4c. Therefore, it is necessary to use a material exhibiting a half mirror effect for the diaphragms 2a and 2b. The shapes of the diaphragms 2a, 2b, 2c are defined so that the acoustic resonance frequencies are different from each other.

In the example shown in FIG. 1, the size of the diaphragm is changed. Therefore, the diaphragm 2 having a small size
c has a higher resonance frequency, and the large-sized diaphragm 2a has a lower resonance frequency. As described above, the frequency characteristics obtained by integrating outputs from the three diaphragms using the diaphragms having different shapes are broadband frequency characteristics.
That is, since the sound receiving characteristic has a form in which the peak characteristics of the three diaphragms 2a, 2b, and 2c are combined, the gain can be increased in a desired frequency range.

The output characteristics obtained by integrating the outputs of the three light receiving elements 4a to 4b are affected by other diaphragms, the light emitting element 3, and the light receiving elements 4a to 4c behind the diaphragm. Although the gain is impaired, the diaphragm can freely vibrate through the opening 5, so that it can have sharp directivity in the front-rear direction. Although the light emitting element 3 and the light receiving element 4 are arranged on the same plane in FIG. 1, they need not always be arranged on the same plane. Further, the shapes of the plurality of diaphragms 2a to 2c may be defined so that the acoustic resonance frequencies are different from each other, and it is not always necessary to form the plurality of vibration plates only in different sizes. It can also be formed differently.

FIG. 2 is a sectional view of an acoustoelectric conversion device according to another embodiment of the present invention. In the present embodiment, diaphragms 2a and 2b are arranged on the same plane. Further, the light emitting element 3 and the light receiving elements 4a and 4b are arranged on the same plane. Further, a half mirror 6 is arranged at a predetermined position in the housing 1. The light emitted from the light emitting element 3 is a half mirror 6
A part of the light is reflected, hits the diaphragm 2a, reflects there, and enters the light receiving element 4a. On the other hand, part of the light transmitted through the half mirror 6 enters the diaphragm 2b, is reflected there, and enters the light receiving element 4b. The light emitted from the light emitting element 3 is distributed by the half mirror 6 and reflected by the diaphragms 2a and 2b, respectively, and is reflected by the light receiving elements 4a and 4b.
Incident on.

In the configuration shown in FIG. 2, the length in the vertical direction can be reduced as compared with the configuration shown in FIG. 1, so that a more compact acoustoelectric converter can be realized. In the embodiment shown in FIG. 2, the acoustic resonance frequencies of the diaphragms 2a and 2b can be made different by making the shapes of the diaphragms 2a and 2b different. As a result, the combined acoustic characteristics can make the gain uniform in a wide frequency band. When a VCSEL is used as the light emitting element 3, the diameter of the light emitting beam can be made extremely small, and the focal length can be set quite freely, so that the degree of freedom between the diaphragm and the light emitting element can be increased. it can.

As described above, according to the present invention, the diaphragms can be arranged close to each other, and furthermore, the diaphragm can be configured so that there is no obstacle between the diaphragms. By integrating the bidirectional characteristics, it is possible to realize a directional microphone device in which the directivity is extremely sharp and the frequency characteristic extends to a high frequency range.

[0013]

As described above, in the present invention, a plurality of diaphragms are arranged for one light emitting element separately from the light emitting element. A conversion device can be realized. In addition, by changing the size of each diaphragm, it is possible to realize a very small and efficient acoustoelectric transducer with sharp directivity.

[Brief description of the drawings]

FIG. 1 is a sectional view showing a structure of an acoustoelectric conversion device according to an embodiment of the present invention.

FIG. 2 is a cross-sectional view of an acoustoelectric conversion device according to another embodiment of the present invention.

[Explanation of symbols]

 Reference Signs List 1 housing 2 diaphragm 3 light emitting element 4 light receiving element 5 opening

Claims (8)

[Claims] 1. A plurality of diaphragms independently fixed in a housing and vibrating by sound pressure, a light source for irradiating the diaphragm with a light beam, and receiving reflected light from each of the diaphragms. And a plurality of light receiving elements for outputting signals corresponding to the vibrations of the respective diaphragms. 2. The acoustoelectric transducer according to claim 1, wherein the plurality of diaphragms are defined in a shape such that acoustic resonance frequencies are different from each other. 3. The acoustoelectric transducer according to claim 1, wherein the plurality of diaphragms are arranged on different planes. 4. The acoustoelectric transducer according to claim 1, wherein the plurality of diaphragms are arranged on the same plane. 5. The acoustoelectric conversion device according to claim 1, wherein the light source and the plurality of light receiving elements are arranged on the same plane. apparatus. 6. The acousto-electric transducer according to claim 1, wherein some of the plurality of diaphragms exhibit a half-mirror effect. 7. The acousto-electric conversion device according to claim 1, wherein the light beam is distributed via a half mirror element disposed in the housing, and is irradiated on the respective diaphragms. Acoustoelectric conversion device. 8. The acoustoelectric converter according to claim 1, wherein the light source is a vertical cavity surface emitting laser device.