JP2001238293A - Acoustoelectric transducer - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an acoustoelectric transducer that can reproduce sound with high S/N. SOLUTION: The acoustoelectric transducer provided with a diaphragm vibrated by sound, a light emitting element that makes light incident onto the diaphragm, a photodetector that transducers a displacement of the diaphragm by sound into a change in an electric signal and provides an output, and a lens element that converges the incident light from the light emitting element and leads the converged light to the diaphragm, converges a divergent reflecting light from the diaphragm between a 1st focal position and a 2nd focal position on an optical axis and leads the converged light to the light receiving element, is provided with a shade means that shades part of the divergent reflecting light converged between the 1st focal position and the 2nd focal position.

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. 6 is a diagram showing a basic structure of the optical microphone device. FIG.
(A) shows a cross-sectional shape, in which an electronic circuit board 12 is installed on the bottom surface 8 of the housing 1 and a light emitting element L
The substrate 9 on which D and the light receiving element PD are arranged is attached. A surface emitting laser diode LD is used as a light emitting element, and a photodiode PD is used as a light receiving element. Substrate 9
A circular surface emitting laser diode LD is arranged at the center of the light emitting device, and the light receiving elements PD are arranged concentrically around the surface emitting laser diode LD.

FIG. 6B is an enlarged 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. 6A are mounted. As shown in the figure, a circular light emitting element LD 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. The light emitting element LD and the light receiving element PD can be simultaneously manufactured on a gallium arsenide wafer by a semiconductor manufacturing process. Therefore, since the alignment accuracy between 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 conventional light receiving and emitting element of the optical microphone element can be used. It can be realized with a high accuracy of 1/100 or less as compared with the positioning accuracy.

In general, a vertical cavity surface emitting laser light emitting device has a characteristic in which the light emission intensity distribution is substantially uniform concentrically. Therefore, the radiated light emitted from the light emitting element LD installed at the central portion toward the diaphragm 2 at a predetermined angle is reflected concentrically with the same intensity, and the diaphragm 2 is received by receiving the sound wave 7. By vibrating, the reflection angle changes and reaches the concentric shape of the light receiving element PD. Therefore, the change in the amount of received light of the light receiving elements PD1 to PDn arranged concentrically is detected, and the change in the amount of received light is converted into a change in the electric signal and output, whereby the vibration displacement of the diaphragm 2 can be detected.
Thereby, the strength of the incident sound wave 7 can be detected, and thus, it can be used as an optical microphone element. An electrode 11 is formed for driving the light emitting element LD and the light receiving element PD or detecting the amount of incident light.

The displacement of the diaphragm 2 is detected by amplifying a change in the electric signal detected from the light receiving element PD with an amplifier such as a differential amplifier or a divider. Here, if the output of the amplifier is to be increased to a practical level, it is necessary to increase the amplification factor of the amplifier, which complicates the design of the amplifier. In addition, when the amplification factor is increased, the noise generated on the electronic circuit is also increased accordingly, making it difficult to increase the signal / noise (S / N) ratio. Therefore, without increasing the amplification factor of the amplifier, S /
In order to obtain a signal with a high N ratio, it is necessary to increase the change in the movement width of the reflected light when the light receiving element receives the reflected light.

FIG. 7 shows a structure in which the lens element 3 is arranged on the optical path between the substrate 9 and the diaphragm 2 in order to increase the movement width of the reflected light. The distance (L0) between the light emitting element LD and the diaphragm 2 was 1.3 mm, and the lens diameter was 0.25 m.
m, a lens element 3 having a magnification of 6.5 is arranged on the optical path. The diaphragm 2 is arranged near the focal position of the lens element 3 and is set as a reference position. The point a in FIG. 7 indicates the imaging position. Point b indicates an image point at the position where the light is reflected by the diaphragm 2 and turned back. The state shown in FIG. 7 is a state in which diaphragm 2 is dented by high-pressure sound. The angle θ is determined by the convergence angle of the lens element 3, and θ = 12 ° in the state shown in FIG.
The diaphragm 2 is initially at the position 2c, and vibrates by a predetermined amount of strangeness δ due to the vibration, and moves to the position 2d. Further, the diameter of the reach distance of the reflected light when the diaphragm 2 is stationary is 2
A, assume that the diameter of the reaching distance of the reflected light when the diaphragm 2 moves by the strange amount δ is 2B. In the configuration as shown in FIG. 7, the movement width when the reflected light converged by the lens element 3 reaches the light receiving element PD increases, and the light receiving sensitivity increases.

[0007]

However, even with the structure of the improved optical microphone device shown in FIG. 7, the sensitivity was not always sufficiently high. Therefore, an object of the present invention is to provide an acoustoelectric conversion device using a lens element as shown in FIG.

[0008]

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. A light receiving element that converts the displacement into a change in an electric signal and outputs the converted light, and converges incident light from the light emitting element and guides the light to the diaphragm, and diverges and reflects light from the vibrating body on a first optical axis.
An acousto-electric conversion device comprising a lens element that converges between the first focus position and the second focus position and guides the lens to the light receiving element. A shielding means for shielding a part of the converged divergent reflected light is provided.

In the acoustoelectric conversion device, the light emitting element may be provided on the optical axis at substantially the same position as the shielding means. Further, in the acoustoelectric conversion device,
The light receiving element can be configured to be divided into two with respect to the optical axis. Further, in the acoustoelectric conversion device,
The light emitting device may be a vertical cavity surface emitting laser device. In the acoustoelectric conversion device, the shielding means may be a knife edge provided substantially at right angles to the optical axis.

Further, the present invention provides a vibration plate vibrating by sound, a light emitting element for making light incident on the vibration plate, a light reflected from the vibration plate, and a displacement of the vibration plate due to sound being an electric signal. And a light-receiving element that converts the light into a change and outputs the light, and converges the incident light from the light-emitting element to guide the light to the diaphragm. An acousto-electric conversion device comprising a lens element converging between the first focus position and the second focus position, wherein the divergent reflected light converges at the first focus position and the second focus position, respectively. Mirror means for further reflecting and guiding the light to the light receiving element is provided. In the acoustoelectric conversion device, the light emitting element may be provided on the optical axis at substantially the same position as the mirror unit.

The present invention further provides a trapezoidal vertical cavity surface emitting laser light emitting device having a light emitting surface having a substantially uniform concentric emission distribution and a mirror surface falling at a predetermined angle from the light emitting surface. It is arranged at the center, and d = h · tan (180−2 · α) where α is located on both sides of the light emitting element from the optical axis 4.
A substrate on which a light receiving element divided by two at a distance of> 45 ° is disposed, a diaphragm that is installed substantially parallel to and close to a position facing the substrate, vibrates by acoustics, and an incident light from the light emitting element A lens element that converges light and guides the light to the diaphragm, and converges divergent reflected light from the diaphragm between a first focus position and a second focus position on an optical axis and guides the light to the light receiving element; And disposing the light emitting surface of the light emitting element between the first focal position and the second focal position on the optical axis, and reflecting the divergent reflected light on the mirror surface. The light is guided to the light receiving element. In the acoustoelectric conversion device, the light emitting element and the light receiving element can be manufactured over the same substrate in the same step.
Further, in the acoustoelectric conversion device, the light emitting element and the light receiving element can be manufactured on different substrates in different steps.

[0012]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS FIG. 1 is a principle diagram for explaining the configuration of the present invention. In the present invention, a shielding means for shielding a part of the divergent reflected light converged between the lens element 3 and the light receiving element PD is provided. In the example shown in FIG. 1, a knife edge 10 is provided as shielding means. Reflected light reflected and diverged by the diaphragm 2 is converged by the lens element 3 and
Light is condensed so as to converge at two focal positions f1 and f2.
Therefore, in the present invention, the knife edge 10 is provided between the short focal position f1 and the long focal position f2. As a result, the return light from the diaphragm 3 blocks the light flux on one side, and the light flux before and after the focus is divided into two parts with respect to the optical axis of the light receiving element PD.
And the area B is reached. Therefore, by taking the difference signal between the optical signal detected from the area A and the optical signal detected from the area B, the received light quantity modulation can be performed with higher sensitivity as compared with the structure shown in FIG. Can be. By changing the distance Δ between the knife edge 10 and the light receiving element PD, an optimum light receiving element size and sensitivity can be obtained.

FIG. 2 is a diagram for explaining the operation principle of the configuration shown in FIG. In the example shown in FIG. 2A, the return light from the lens 3 is shifted to the short focal position f1 with respect to the knife edge 10.
This is an example that converged to the side. In this case, the return light from above the lens 3 is blocked by the knife edge 10 and the light receiving element P
The return light from the lens element 3 is irradiated only to the region A without reaching the region B of D. In the case of FIG. 2B, the return light from the lens 3 converges on the position of the knife edge 10 between the short focal position f1 and the long focal position f2.
In this example, the amount of light received in the region A of the light receiving element PD is equal to the amount of light received in the region B. FIG. 2 (c)
In this example, the return light is converged on the long focal position f2 side with respect to the knife edge 10. In this case, only the return light from above the lens 3 is received in the region B of the light receiving element PD. By extracting, as a difference signal, the magnitude of the optical signal received in the A region and the B region of the light receiving element PD, a large difference signal can be obtained as compared with the case shown in FIG.

FIGS. 1 (a) to 1 (c) show the state of receiving the return light at the light receiving element PD, and FIGS.
(C) respectively. In the embodiment shown in FIG. 1, the distance between the knife edge 10 and the light receiving element PD is Δ, the vibration displacement of the diaphragm 2 is ± δ, and the distance between the light emitting element LD and the diaphragm is 1 Assuming that .39 mm, the lens diameter is 0.25 mm, and the magnification is 6.5, the distance L between the light emitting element LD and the lens is 1.2 mm, and the distance F between the lens 3 and the diaphragm 2 is 0.19 mm. Become. FIG. 1
In the example shown in (1), the light emitting element LD is on the optical axis 4 and is at the same position as the installation position of the knife edge 10. Further, the displacement d of the diaphragm 2 is an offset amount from the reference position. If Hap is the luminous flux height of the return light on the lens,
The luminous flux heights A and B on the light receiving element PD according to the displacement ± δ of the diaphragm 2 are shown, and the results shown in Table 1 are obtained.

[0015]

[Table 1]

FIG. 3 is a view showing another embodiment of the present invention. In this embodiment, one return light is not blocked by using a blocking means as shown in FIG. Mirror means 20a, 2 so that the light is reflected and guided to the light receiving element.
0b is provided. The return light converged to the short focal point position f1 by the mirror means 20a, 20b is received by the light receiving elements A1, A
2, the return light converging to the long focal position f2 is guided to the light receiving elements B1 and B2. The light beam of the return light is separated into two light receiving elements and received by such a mirror means. Therefore, the sum of the difference signals of the light receiving elements on both sides can be amplified to output the light amount modulation. That is, in the example shown in FIG. 3, the light receiving output signal can be extracted as a sum signal of the difference between the light receiving elements A1 and B1 and the difference between A2 and B2. Mirror means 2
0a and 20b are arranged symmetrically with respect to the optical axis 4 and inclined at a predetermined angle. The light emitting element is provided by the mirror means 20.
a, 20b can be installed on the optical axis 4 at the tip end. In the example shown in FIG. 3, the light emitting element LD is installed on the optical axis 4 so as to be located between the short focal position f1 and the long focal position f2. It is located at the apex of the mirror means 20a, 20b, thereby forming a substantially trapezoidal shape.

FIG. 4 is a diagram for explaining the detailed operation principle of the second embodiment shown in FIG. A predetermined angle α from the light emitting surface
A trapezoidal vertical cavity surface emitting laser light emitting element LD having mirror surfaces 20a and 20b falling at
D = h · tan from the optical axis 4 on both sides of the light emitting element LD.
A substrate on which light receiving elements A1 and B1 divided into two by a distance of (180-2 · α) (where α> 45 °) is used. Here, h is the height of the trapezoid, and the mirror surfaces 20a, 20b
Is extended with the inclination α, and is the height from the intersection with the optical axis 4 to the substrate. Also, d is the distance from the optical axis 4 to the division point of the light receiving element divided into two. The return light from the lens 3 along the optical axis 4 has an incident angle and a reflection angle of α, and d = h
A relationship of tan (180-2 · α) is established. FIG.
(D) is a diagram showing a reflection state of return light when such mirror means 20a and 20b are used.

FIG. 5 is a view for explaining a method of manufacturing the light emitting element and the mirror means in the embodiment shown in FIG.
Shows a method of manufacturing a light receiving and emitting element and a mirror means on a gallium arsenide substrate in the same process, and FIG. 2 (b) shows a method of manufacturing a light receiving element on a silicon substrate and then forming a composite of a light emitting element and a mirror means separately formed. The method of combining with a light receiving element is shown.

The method of manufacturing in the same step shown in FIG. 5A can reduce the number of steps, but has a disadvantage that the gallium arsenide substrate is expensive. In this method, a gallium arsenide substrate is prepared (step 40), and its peripheral portion is removed by etching (step 41) while leaving a portion where a light emitting element is formed at the center. Next, crystal growth is performed on the entire surface (step 42). Next, the side wall of the light emitting element LD formed at the center is etched at a predetermined angle to form a slope (step 43). Next, a mirror coating is performed on the slope to form mirror means so that light is reflected.

In the manufacturing method according to FIG.
Since the light receiving element and the mirror means are integrally formed on the same substrate, a highly accurate ultra-compact acoustoelectric converter can be realized. However, since the gallium arsenide substrate is expensive as described above, there is a disadvantage that the cost increases. In the method shown in FIG. 5 (b), only the light receiving element is formed using a low-priced silicon substrate, and the light emitting element and the mirror means are formed on an expensive gallium arsenide substrate, which is integrally formed by die bonding. Things.

As shown in Step 50, a silicon substrate is prepared, and the substrate is etched and crystal grown (Steps 51 and 52) to form a light receiving element portion.
On the other hand, a gallium arsenide substrate is prepared, and a crystal is grown thereon (steps 60 and 61) to form a light emitting element. Then, a slope is formed at a predetermined angle on the crystal surface formed in step 61, and the slope is mirror-coated (step 62), thereby forming a light emitting element and mirror means integrated with the light emitting element. . Next, this is separated by dicing (step 63), and the separated chip composed of the light emitting element and the mirror means is bonded to the light receiving element made of a silicon substrate by die bonding (step 53), whereby the light receiving / emitting element and the mirror means are connected. To form Although this manufacturing method requires more steps, the cost of the apparatus can be reduced because the silicon substrate is cheaper than the gallium arsenide substrate.

[0022]

As has been described in detail based on the above embodiments, the present invention has a shielding means for shielding a part of the return light or a mirror means for further reflecting the return light, thereby providing a return light. Since the difference between the detection signals becomes large or the moving width of the return light can be greatly increased, a high S / N reproduction sound can be realized. In addition,
It goes without saying that the present invention can be used not only for optical microphone devices but also for acoustic sensors and the like.

[Brief description of the drawings]

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

FIG. 2 is a diagram for explaining the operation principle of the configuration shown in FIGS. 1 and 3;

FIG. 3 is a diagram for explaining the operation principle of the second embodiment of the present invention.

FIG. 4 is a view for explaining the detailed operation principle of the second embodiment shown in FIG. 3;

FIG. 5 is a process chart showing a method for manufacturing a light receiving and emitting element.

FIG. 6 is a diagram showing an example of a conventional electroacoustic transducer.

FIG. 7 is a diagram for explaining the operation principle of an acoustoelectric conversion device using a conventional lens element.

[Explanation of symbols]

 2 diaphragm 3 lens element LD light emitting element PD light receiving element 10 knife edge 20a, 20b mirror means

 ──────────────────────────────────────────────────続 き Continued on the front page (72) Inventor Toru Shinzo 1-14-6 Dogenzaka, Shibuya-ku, Tokyo Inside Kenwood Co., Ltd. (72) Inventor Hirohiro Kobayashi 1-14-6 Dogenzaka, Shibuya-ku, Tokyo Stock Company Kenwood Inside (72) Inventor Nobuhiro Miyahara 1-14-6 Dogenzaka, Shibuya-ku, Tokyo Co., Ltd. Kenwood Inside (72) Inventor Hiroshi Hattori 1-14-6 Dogenzaka, Shibuya-ku, Tokyo Kenwood Co., Ltd. (72) Invention Jim Hang Woburn Suites, Massachusetts, USA 3000 West Cummings Park 400 New Dimension Technology, Inc. (72) Inventor Victor Lazarev, Woburnsuite, Mass., USA 3,000 West Cummings Park 400 New Dimension Technology, Inc. F-term (reference) 5D021 DD04 5F089 BB01 BB08 CA06 GA01

Claims (10)

[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. And a light receiving element that outputs the light, and converges incident light from the light emitting element and guides the light to the diaphragm, and diverges and reflects light from the diaphragm to a first focal position and a second focal position on the optical axis. An acousto-electric conversion device comprising a lens element converged between the first focal position and the second focal position, and a part of the divergent reflected light converged between the first focal position and the second focal position. An acousto-electric conversion device comprising a shielding means for shielding the sound. 2. The acoustoelectric conversion device according to claim 1, wherein the light emitting element is provided on the optical axis at substantially the same position as the shielding means. 3. The acoustoelectric conversion device according to claim 1, wherein the light receiving element is divided into two with respect to the optical axis. 4. The acoustoelectric conversion device according to claim 1, wherein the light emitting element is a vertical cavity surface emitting laser element. 5. The acoustic-electric conversion device according to claim 1, wherein said shielding means comprises a knife edge provided substantially at right angles to said optical axis. Electric conversion device. 6. 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. And a light receiving element that outputs the light, and converges incident light from the light emitting element and guides the light to the diaphragm, and diverges and reflects light from the vibrating body to a first focal position and a second focal position on the optical axis. Wherein the divergent reflected light converging to the first focal position and the second focal position is further reflected. An acoustoelectric conversion device comprising a mirror means for guiding to the light receiving element. 7. The acoustoelectric transducer according to claim 6, wherein the light emitting element is provided on the optical axis at substantially the same position as the mirror means. 8. A trapezoidal vertical cavity surface emitting laser light emitting device having a light emitting surface having a substantially uniform concentric emission distribution and a mirror surface falling at a predetermined angle from the light emitting surface. A substrate on which a light receiving element is disposed so as to surround the light emitting element; a diaphragm that is installed substantially parallel to and close to a position facing the substrate and vibrates by sound; and A lens element that converges incident light and guides it to the diaphragm, and converges divergent reflected light from the diaphragm between a first focal position and a second focal position on an optical axis and guides the divergent reflected light to the light receiving element And disposing the light emitting surface of the light emitting element between the first focal position and the second focal position on the optical axis, and reflecting the converged divergent reflected light on the mirror surface Acousto-electric conversion device, Place. 9. The acoustoelectric conversion device according to claim 8, wherein the light emitting element and the light receiving element are manufactured on the same substrate in the same process. 10. The acoustoelectric conversion device according to claim 8, wherein the light emitting element and the light receiving element are manufactured on different substrates in different steps.