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JPS5850900

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DESCRIPTION JPS5850900
[0001]
The present invention relates to a microphone in which a vibrating film and a light detector are
disposed on both force surfaces of a semiconductor laser, respectively, and the displacement of
the vibrating film is optically detected by the light detector. It is an object of the present
invention to provide a microphone capable of preventing the deterioration of F3 / H due to the
scattered light on the light receiving surface of the light detector and the unstable field of the
oscillation of the semiconductor laser. In general, a microphone using a semiconductor laser is
held in a holder 4 (earth electrode) having a sound hole 3 in a state where the semiconductor ?ther 1 is mounted in a heat sink 2 as shown in FIG. An oscillating film 6 having a reflecting film
surface 6a is disposed in parallel with an appropriate gap of about several tens of ?s in front of
the output surface of the semiconductor laser 1 and flat at an appropriate distance in front of the
other output surface of the semiconductor laser 1 The photodetector 6 such as a photodiode
having a large light receiving surface 61 L is disposed, and the light output from one output
surface of the semiconductor laser 1 is reflected by the reflecting film surface 6 a of the vibrating
film 60. It is configured to detect light output from the other output surface of the semiconductor
laser 1 by the light detector 6 by changing the light output from the semiconductor laser 1 by
returning to the cavity and causing interference. It was In FIG. 1, 7 is a holder of the
photodetector 6, 8 is a cathode terminal of the semiconductor laser 1, 9 is an output terminal of
the photodetector 6, and 10 is a micro. ???????????? However, in the abovedescribed conventional microphone, the optical axis of the semiconductor laser 1 and the central
axis B of the light detector 6 are disposed so as to coincide with each other. The light output is
not parallel rays, but usually has a spread of 20 ░ to 40 ░. Therefore, the light output from the
other output surface of the semiconductor laser 1 input to the flat i light surface 6 & of the light
detector 6 is scattered by the flat light receiving surface 61 L, and the scattered light is
transmitted to the semiconductor laser There is a problem that the S / N is deteriorated by being
05-05-2019
1
fed back to the cavity 1 and that the stable oscillation of the semiconductor laser 1 is hindered.
The present invention solves the above-mentioned conventional defects, in which the
photodetector is slightly offset from the optical axis of the semiconductor laser and a lens having
a wedge on the front surface is disposed on the light receiving surface. is there. As a result, the
amount of feedback of the scattered light reflected by the light detector to the semiconductor
laser is reduced to stabilize the oscillation of the semiconductor laser and to improve the S / N.
Hereinafter, the microphone of the present invention will be described with reference to the
seven drawings of the embodiment.
FIG. 2 shows an embodiment of the microphone according to the present invention, in which 11
is a semiconductor laser having a strong self-coupling effect, 12 is a heat sink to which the
semiconductor laser 11 is attached, and 13 is the semiconductor laser 11 attached. The holder is
also used as a ground electrode for holding the heat sink 12 and has a sound hole 14. A vibrating
film 15 is disposed on the front surface of one output surface of the semiconductor laser 11 with
an appropriate gap of about several tens of microns, and has a reflecting film surface 16a on the
back surface. 16 is a photodetector such as a photodiode disposed at an appropriate distance in
front of the other output surface of the semiconductor laser 11; 17 is a front surface provided on
the flat light receiving surface 16 & of the photodetector 16; It is a lens having a curved surface
171L and is formed by molding glass. The light detector 16 is disposed such that its central axis
B is slightly offset from the optical axis of the semiconductor laser 11. Reference numeral 18
denotes the semiconductor laser 111711 y cathode terminal, 19 denotes an output terminal of
the light detector 16, 20 denotes a holder of the light detector 16, and 21 denotes a microphone
cavity. The holder 13 is plated with black zinc, and the holder 20 is made of a black resin
material and absorbs infrared scattered light. In the microphone of such a configuration, the
vibrating film 15. Is mechanically displaced by the sound pressure, the light output from one
output surface of the semiconductor laser 11 is reflected by the reflection film surface 151L of
the vibrating film 16 and returned to the cavity of the semiconductor laser 11 It causes
interference. Then, a change in light output from the other output surface of the semiconductor
laser 11 due to the interference is detected by the light detector 16 to convert mechanical
displacement of the vibrating film 16 into an electrical signal. To detect. At this time, the central
axis B of the light detector 16 is slightly offset from the optical axis of the semiconductor laser
11, and the lens 17 is provided on the flat light receiving surface 16 & of the light detector 16.
The light from the other light output surface of the semiconductor laser 11 is refracted by the
lens 17 and is incident on the flat light receiving surface 162 L of the light detector 16. Then, the
scattered light reflected by the light detector 16, the lens 17 and the like decreases the amount
of feedback to the semiconductor laser 11 because of the lens 17, and therefore the oscillation of
the semiconductor laser 11 is stabilized to reduce S / N can be improved. Further, since the
holder 14 and the holder 20 are black, they can absorb the scattered light, and the oscillation
stability and the S / N of the semiconductor laser 11 can be further improved.
05-05-2019
2
As described above, according to the present invention, the photodetector is disposed on the
monitor output side of the semiconductor laser so that the central axis of the photodetector is
slightly offset from the optical axis of the semiconductor laser and the light receiving surface of
the photodetector is Since the lens is provided on the front of the semiconductor laser, the
amount of feedback of the scattered light on the monitor output side of the semiconductor laser
to the cavity of the semiconductor laser can be reduced, and the instability of the oscillation of
the semiconductor laser can be prevented. It has the advantage that N can be significantly
improved.
[0002]
Brief description of the drawings
[0003]
FIG. 1 is a block diagram of a conventional microphone, and FIG. 2 is a cross-sectional view of
one embodiment of a non-bright microphone.
11 ииииии Semiconductor laser, 12 ииииииииииииииииииииииииииииииииииииииииииииииииииииии Sound hole, 16 иииииии Vibrating film, 5
toe: Reflective film surface, 16 ...: Photodetector, 161 L ..: Light receiving surface, 17. River. Lens,
18 ... Cathode terminal, 19? ? ? River ? Output terminal, 20 ? ? ? ? ? ? ? ? ? ? ?
??????????????????????????????????
1
05-05-2019
3
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