JP2001231100A - Acoustic-electric transducer - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a directive acoustic-electric transducer in a small size that has a broadband characteristic. SOLUTION: In the acoustic-electric transducer provided with a diaphragm 2 vibrated by sound, a light emitting element LD that emits a light to the diaphragm 2, and a photodetector PD that converts a displacement of the diaphragm 2 by sound into a change in an electric signal and outputs the electric signal in a housing 1, N (N is an integer of >=2) pieces of the diaphragms 2 are arranged in parallel on different planes at a prescribed interval and the light emitting elements LD and the photodiodes PD are provided corresponding to the respective diaphragms 2.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

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 very small acoustoelectric conversion device using a VCSEL. FIG. 7 is a diagram showing a basic structure of the optical microphone device, and FIG. 7 (a) shows a cross-sectional shape. An electronic circuit board 12 is installed on the bottom surface 8 of the housing 1, and a board 9 on which a light emitting element and a light receiving element are arranged is mounted on the board 12. A surface emitting laser diode LD is used as a light emitting element, and a photodiode PD is used as a light receiving element. A circular surface emitting laser diode LD is arranged at the center of the substrate 9 and the light receiving element PD is arranged concentrically so as to surround the surface emitting diode LD.
Place. FIG. 7B is a plan view showing a light emitting / receiving section of the substrate 9 on which the light emitting / receiving elements shown by dotted lines in FIG. 7A are mounted. As shown in the figure, a light emitting element LD having a circular shape is arranged at the center, and light receiving elements PD1, PD2,..., PDn are arranged concentrically so as to surround the light emitting element LD. Note that a vertical cavity surface emitting laser can be used as the light emitting element LD used here. This light emitting element LD
And the light receiving element PD can be simultaneously manufactured on a gallium arsenide wafer by a semiconductor manufacturing process.

[0003] Therefore, since the positioning accuracy of the light emitting element LD and the light receiving element PD is determined by the accuracy of the mask used in the semiconductor manufacturing process, the alignment accuracy can be made 1 μm or less, and the receiving accuracy of the conventional optical microphone element can be reduced. It can be realized with a high accuracy of one hundredth or less as compared with the alignment accuracy of the light emitting element. In general, a vertical cavity surface emitting type light emitting device has a characteristic in which a light emission intensity distribution is substantially uniform concentrically. Therefore, radiation emitted from the light emitting element LD installed at the center toward the diaphragm 2 at a predetermined angle is:
The light is reflected concentrically with the same intensity, and the diaphragm 2 vibrates due to the reception of the sound wave 7 to change the reflection angle and concentrically reach the light receiving element PD.

Therefore, the vibration displacement of the diaphragm 2 can be detected by detecting a change in the amount of received light of the light receiving elements PD1 to PDn arranged concentrically. As a result, the intensity of the incident sound wave 7 can be converted into a change in the electric signal and detected, so that it can be used as an optical microphone element. Driving the light emitting element LD and the light receiving element PD,
Alternatively, the electrode 11 is formed for detecting the amount of incident light.

When a plurality of such optical microphone elements are combined to form a wide-band composite microphone device, conventionally, a plurality of completed devices as shown in FIG. Could not be narrowed. In addition, even when a plurality of elements are mounted in the same housing, the light emitting elements are installed behind the respective diaphragms, so that the size is large. In addition, the same size diaphragm was used for a plurality of microphone elements.

[0006]

In order to construct a wide-band microphone device by arranging a plurality of conventional optical microphone elements as described above, there has been a disadvantage that the diaphragm cannot be approached or the shape thereof becomes large. Therefore, it has been difficult to realize a small, wideband directional microphone device. Further, since the size of the diaphragm of the microphone device was constant, it was difficult to set a characteristic having a characteristic in the frequency characteristic, and it was difficult to realize an optical microphone device with high efficiency over a wide band. The present invention has been made to solve the above-described problems, and has as its object to provide an acoustoelectric conversion device having a small size and directivity having a wide-band frequency characteristic.

[0007]

According to the present invention, there is provided a vibration plate vibrating by sound, a light emitting element for irradiating light to the vibration plate, and light reflected from the vibration plate to be received by the sound of the vibration plate. In an acoustoelectric conversion device having a light receiving element for converting a displacement into a change in an electric signal and outputting the converted signal in a housing,
A plurality (N is an integer of 2 or more) of diaphragms are arranged in parallel on different planes at a predetermined interval, and the light-emitting element and the light-receiving element are provided corresponding to each of the diaphragms. . Further, the present invention provides a vibration plate vibrating by sound, a light emitting element for emitting light to the vibration plate, and receiving light reflected from the vibration plate, and converting displacement of the vibration plate by sound into a change in an electric signal. In an acoustoelectric conversion device having a light receiving element for converting and outputting in a housing, N (N is an integer of 2 or more) diaphragms are spaced apart from each other and are arranged on the same plane;
The light emitting element and the light receiving element are provided so as to correspond to the respective vibration plates.

[0008] In the acoustoelectric conversion device, the N diaphragms may be a combination of diaphragms having the same thickness and different sizes. Further, in the acoustoelectric conversion device, the N diaphragms may be a combination of diaphragms having different fundamental resonance frequencies. Further, in the acoustoelectric conversion device, a large number of openings may be provided in the housing, and the sound may reach the diaphragm via the openings. In the acoustoelectric conversion device, the set of the light emitting element and the light receiving element provided corresponding to each diaphragm may be arranged on the same plane. Further, the light emitting device is a vertical cavity surface emitting laser device in which the emission intensity distribution is substantially uniform concentrically,
The acoustoelectric conversion device may be configured such that the light receiving elements are arranged concentrically so as to surround the laser element. In the acoustoelectric conversion device, the light emitting element may be a vertical cavity surface emitting laser element.

[0009]

FIG. 1 is a view showing a first embodiment of an acoustoelectric converter according to the present invention. FIG. 1 (a) is a cross-sectional view, and FIG. 1 (b) is an external view. is there. FIG.
In the embodiment shown in FIG. 1, the vibration plates 2-1 to 2-5 are arranged in parallel on different planes at a predetermined interval, and the light emitting elements LD1 to LD5 are respectively associated with the respective vibration plates 2-1 to 2-5. LD
5 and light receiving elements PD1 to PD5. Each of the diaphragms 2-1 to 2-5 has a disk structure having the same thickness and different sizes. These diaphragms 2-1 to 2-5 are respectively provided with diaphragm mounting members 4-1 to 4 formed in the housing 1.
It is attached to -5. The light emitting elements LD1 to LD5 and the light receiving elements PD1 to PD5 are also attached to the light receiving and emitting element attachment members 5-1 to 5-5, respectively. Light emitting element LD
Supply of drive current to 1 to LD5 and light receiving elements PD1 to PD
Extraction of the light receiving current from D5 is performed via the electronic circuit board 12. In addition, the housing 1 and the mounting member 4 are provided to ensure the arrival of sound waves to each of the diaphragms 2-1 to 2-5 and to provide directivity in front and behind the diaphragms 2-1 to 2-5.
A large number of openings 3 are provided in 1 to 4-5 and 5-1 to 5-5. If the light emitted from the light emitting elements LD1 to LD4 is focused on the center of each of the diaphragms 2-1 to 2-4, the diaphragms 2-2 to 2-5 existing in front of the diaphragms become obstructive. Therefore, as shown in FIG. 1C, a small hole 6 is provided in the diaphragm in front of the diaphragm so that incident light and reflected light pass therethrough. Here, the basic resonance frequencies of the diaphragms 2-1 to 2-5 shown in FIG.

[0010]

(Equation 1)

That is, since the fundamental resonance frequency is inversely proportional to the square of the radius of the diaphragm, four times the frequency can be obtained if the radius is reduced to half. Further, at the fundamental frequency or a resonance frequency that is an even multiple thereof, the division mode is such that the amplitude becomes maximum near the center. Therefore, if the light is focused there, the sensitivity becomes extremely high near the resonance frequency. Therefore, in the present embodiment, the radius of the five diaphragms 2-1 to 2-5 is set to 1: {3:}.
5: √9: √20, and the resonance frequencies are superposed to cover a wide frequency band. Here, in order to emphasize the voice band, the fundamental resonance frequency of the largest diaphragm 2-5 is set to 100 Hz. As a result, as shown in FIG.
Very high sensitivity was obtained over the range of 0 Hz. In addition, if the distance between the respective diaphragms is large, the directivity at a lower frequency is deteriorated due to a phase shift. Therefore, it is desirable that the diaphragms be arranged at intervals as narrow as possible. Here, the frequency characteristic is set to about 2 mm so that sensitivity can be stably obtained up to about 20 kHz.

FIG. 2 shows a cross-sectional structure of an acoustoelectric conversion device according to a second embodiment of the present invention. In the present embodiment, unlike the first embodiment, the light emitting element LD and the light receiving element PD are installed on the same mounting member 10. By adopting such a configuration, it is possible to reduce the size of the device as compared with the first embodiment. FIG. 3 shows a sectional structure of an acoustoelectric conversion device according to a third embodiment of the present invention.

In the present invention, a light emitting / receiving element is mounted on the same mounting member 10 as in the embodiment shown in FIG. In the case of the embodiment shown in FIGS. 1 and 2, it was necessary to provide a small hole 6 in the front diaphragm that allows incident light and reflected light to pass. 2
In order to prevent the change of the shape and the frequency characteristic, the diaphragms 2 are arranged to be shifted in the lateral direction, and small holes for passing light through the mounting members 4-2 and 4-3 are made. Make up. This eliminates the need to make a small hole in diaphragm 2. In the acoustoelectric conversion device as shown in FIG. 3, a light emitting element is a vertical cavity surface emitting laser element, and light receiving and emitting elements having a shape as shown in FIG. 7 are arranged concentrically so as to take in the light emitting element. be able to.

FIGS. 4A and 4B are diagrams showing a configuration of an acoustoelectric conversion device according to a fourth embodiment of the present invention, wherein FIG. 4A is a cross-sectional view, and FIG. I have.
In the present embodiment, the diaphragms 2 are all disposed on the mounting member 4 on the same plane. Similarly, the light receiving and emitting elements are arranged on the same mounting member 10 corresponding to the respective diaphragms. By adopting such a configuration, the size in the horizontal direction is increased, but the thickness in the vertical direction can be reduced. In this embodiment mode, a light emitting / receiving element having a structure as shown in FIG. 7 can be used.

By using the configuration described above, the directivity finally obtained by combining the sensitivity characteristics from the plurality of diaphragms has a shape as shown in FIG. Since other diaphragms, light emitting and receiving elements, and other components are present behind, an electroacoustic transducer having sharp directivity in the front-rear direction can be realized, although the gain is somewhat impaired. When the diaphragm is arranged in a plane as shown in FIG. 4, the characteristics in the high frequency range are deteriorated as compared with the case where the diaphragm is arranged vertically, but the directivity characteristics in the front-rear direction are shown in FIG. It has almost the same shape as the vertical type.

[0016]

As described above, the present invention employs a configuration in which a plurality of diaphragms are installed on the same plane or on different planes, and a light-receiving / emitting element is provided correspondingly. Thus, it is possible to realize an acoustoelectric conversion device having good directivity having the following characteristics. In addition, it is possible to realize a device that changes the frequency characteristics by changing the size of the diaphragm and that efficiently collects sound over a wide band. Further, when a VCSEL is used as a light emitting element, the diameter of a light emitting beam can be made extremely small, so that the setting of the focal length can be made quite freely. Accordingly, the degree of freedom between the diaphragm and the light emitting element can be increased.

As described above, a plurality of diaphragms can be arranged very close to each other, and since there is no obstacle between the respective diaphragms, the directivity is obtained by integrating the bidirectionality of each diaphragm. However, it is possible to realize an acoustoelectric conversion device that is extremely sharp and has extended characteristics over a wide area. Further, when diaphragms having different diameters are used, the frequency characteristics can be arbitrarily changed by a difference in resonance frequency determined by the diameter of the diaphragm. Therefore, a directional acoustoelectric converter with extremely high sensitivity can be realized by using the most efficient band. Needless to say, the present invention can be used not only for an optical microphone device but also for an acoustic sensor or the like.

[Brief description of the drawings]

FIG. 1 is a diagram showing a configuration of an acoustoelectric conversion device according to a first embodiment of the present invention.

FIG. 2 is a diagram showing a second embodiment of the present invention.

FIG. 3 is a diagram showing a third embodiment of the present invention.

FIG. 4 is a diagram showing a fourth embodiment of the present invention.

FIG. 5 is a diagram showing the directivity of the acoustoelectric conversion device of the present invention.

FIG. 6 is a diagram showing frequency / sensitivity characteristics of the acoustoelectric conversion device of the present invention.

FIG. 7 is a diagram for explaining a basic principle of an optical microphone element.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Housing 2 Diaphragm 3 Opening 4,5,10 Mounting member 9 Substrate 12 Electronic circuit board

 ──────────────────────────────────────────────────続 き Continuing on the front page (72) Inventor Hirohiro Kobayashi 1-14-6 Dogenzaka, Shibuya-ku, Tokyo Stock Company Kenwood Corporation (72) Inventor Hiroshi Miyazawa 1-16-16 Dogenzaka, Shibuya-ku, Tokyo Stock Company Kenwood F term (reference) 5D018 BB03 5D021 DD04 5F089 AA10 AB01 AC10 CA21 DA05

Claims (8)

[Claims] 1. A vibrating plate that vibrates by sound, a light emitting element that irradiates light to the vibrating plate, and a light reflected from the vibrating plate is received, and a displacement of the vibrating plate due to sound is converted into a change in an electric signal. An acousto-electric conversion device provided with a light receiving element for outputting the same in a housing, wherein N (N is an integer of 2 or more) diaphragms are arranged in parallel on different planes at a predetermined interval. An acoustoelectric conversion device comprising the light emitting element and the light receiving element provided corresponding to a diaphragm. 2. A vibrating plate vibrating by sound, a light emitting element for emitting light to the vibrating plate, and receiving reflected light from the vibrating plate, and converting a displacement of the vibrating plate by sound into a change in an electric signal. In an acousto-electric conversion device having a light-receiving element for outputting in a housing, N (N is an integer of 2 or more) diaphragms are arranged on the same plane while being separated from each other, and each of the diaphragms is An acoustoelectric conversion device comprising the light emitting element and the light receiving element. 3. The acoustoelectric transducer according to claim 1, wherein the N diaphragms are a combination of diaphragms having the same thickness and different sizes. 4. The acoustoelectric transducer according to claim 1, wherein the N diaphragms are a combination of diaphragms having different fundamental resonance frequencies. 5. The acoustic-electric conversion device according to claim 1, wherein a number of openings are provided in the housing, and the sound reaches the diaphragm via the openings. Acoustoelectric conversion device. 6. The acoustoelectric transducer according to claim 1, wherein a set of the light emitting element and the light receiving element provided corresponding to each diaphragm is arranged on the same plane. An acoustoelectric conversion device characterized in that: 7. The acoustoelectric transducer according to claim 6, wherein the light emitting element is a vertical cavity surface emitting laser element having a light emission intensity distribution substantially uniform concentrically, and the light receiving element includes the laser element. An acoustoelectric conversion device characterized by being arranged concentrically so as to surround it. 8. The acoustic transducer according to claim 1, wherein the light emitting device is a vertical cavity surface emitting laser device.