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JPS6039614

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DESCRIPTION JPS6039614
[0001]
BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a
microphone using a semiconductor laser as a light source and a vibrating film, and having a
mechanism for detecting a change in the intensity of laser light that is irradiated to and reflected
on the vibrating film. Prior Art Configuration and Problems Thereof FIG. 1 is a partial crosssectional view of an essential part of the above-mentioned conventional microphone. In FIG. 1, 1
is a semiconductor laser having a strong self-coupling effect, 2 is a holder for supporting the
semiconductor laser 1 and also serves as a heat sink. A vibrating film 3 reflects the laser light
emitted from the semiconductor laser 1, a shield case 4, a light receiving element 5, and a
microphone unit 6. As described above, in the microphone, at the same time as the sound wave
emitted from the sound source vibrates the vibrating film 3, the vibrating film 3 is irradiated with
the laser light from the semiconductor laser 1, and the reflected light is a resonator (not shown)
of the semiconductor laser 1. To cause interference, and the light receiving element 6 detects a
change in intensity of the laser light caused by the interference. However, since the conventional
microphone described above accommodates the holder 2 of the semiconductor laser 1 and the
semiconductor laser 1 and the light receiving element 6 which also serve as a heat sink in the
microphone unit 6, a considerable space is required. In the case of adding directivity, acoustically
sufficient design is difficult, and in the case of using a thermomodule for temperature control of
the semiconductor laser 1, the microphone unit 6 has been enlarged. Furthermore, the
irradiation of the laser beam of the semiconductor laser 1 has the disadvantage that the vibrating
film 3 is locally thermally deformed. SUMMARY OF THE INVENTION The present invention has
been made in view of the above-mentioned drawbacks, and it is an object of the present invention
to provide a microphone which does not cause local thermal deformation of a vibrating film
while converting the microphone itself into an fJ's type. The microphone of the present invention
has a drive unit provided with a semiconductor laser with a strong self-coupling effect that emits
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laser light, a light detector for detecting the light intensity of the laser light, the drive unit, and
one end Are connected to form an optical path of the laser beam, an optical fiber, a microlens
provided at the other end of the optical fiber for preventing dispersion of the laser beam, and a
laser beam from the microlens that vibrates with respect to sound waves. It is configured to
include a vibrating membrane that reflects light. With this configuration, the vibration of the
vibrating film due to the sound wave is converted to the light intensity of the laser light to be
detected. DESCRIPTION OF THE PREFERRED EMBODIMENT An embodiment of the present
invention will be described below with reference to the drawings. FIG. 2 is an external view of a
microphone according to an embodiment of the present invention. The reference numeral 7
denotes a microphone unit, 8 denotes a semiconductor laser 8a for emitting laser light, a
photodetector 8b for detecting laser light and a drive circuit thereof, and 9 denotes an optical
fiber cable connected to the microphone unit 7 and the drive circuit 8 or the like.
FIG. 3 is a partial cross-sectional view of the main part of the same microphone. 010 is a
vibrating film that vibrates by sound waves and reflects laser light, 11 is an acoustic back
chamber, and 12 is a vibrating parallel beam of incident light from an optical fiber. A microlens
(for example, SELFOC microlens manufactured by Nippon Sheet Glass Co., Ltd.) to be irradiated to
the film 10, a lens holder for supporting the 13jd microlens 12, 14 is an optical fiber having an
optical fiber core 14 ', 16 is a light A holder for supporting the fiber 14 is a microphone unit case
16. The operation of the embodiment configured as described above will be described below. In
FIG. 2 and FIG. 3, first, the laser beam of the semiconductor laser 8a in the drive circuit 8 passes
through the optical fiber 14 and reaches the micro lens 13 to be collimated by the micro lens 13
and irradiated to the vibrating film 10 . The vibrating film 10 reflects the irradiated laser light,
and the reflected light phase-modulated by the displacement of the vibrating film 10 is returned
again to the resonator (not shown) of the semiconductor laser 8 a through the microlens 12 and
the optical fiber 14. Interfere. A change in the intensity of the laser beam caused by this
interference is detected as a microphone output by the photodetector 8 b disposed on the
monitor side of the semiconductor laser 8111. Since the change in intensity of the laser beam is
generated by the change in the distance between the semiconductor laser 8a and the vibrating
film 1o and is proportional to the displacement of the vibrating film 10, the mechanical change
of the vibrating film 1o by the sound wave is converted to the intensity change of the laser beam.
It will be detected by the detector 8b. As described above, according to the present embodiment,
the microphone unit 7 and the drive circuit 8 can be downsized by separating them through the
optical fiber cable 9 which passes light without dispersing light and can be used as a glove
microphone At the same time, the structure is simplified and the assembly is easy. Further, since
the micro lens 12 is provided in the microphone unit T, the spot diameter of the laser beam to
the vibrating film 10 can be made sharp and local thermal deformation of the vibrating film 10
can be alleviated. Furthermore, the dispersion of the laser light is irradiated to the vibrating film
10 as much as possible by the micro lens 12, and the reflected light is returned to the
semiconductor laser 8a side. Therefore, the degree of optical coupling between the
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semiconductor laser 8 & The sensitivity can be increased. As described above, according to the
present invention, the following effects can be obtained. (1) It can be miniaturized and can be
used as a glove microphone, and at the same time, the structure can be simplified and the
assembly can be easily pressed.
(2) Since the spot diameter of the laser beam to the vibrating film is increased, local thermal
deformation of the vibrating film can be alleviated. (3) Since the dispersion of laser light is
suppressed as much as possible to the vibrating film and the reflected light is returned to the
semiconductor laser side, the degree of optical coupling between the semiconductor laser and the
vibration can be increased to increase the sensitivity as a microphone Can.
[0002]
Brief description of the drawings
[0003]
FIG. 1 is a partial cross-sectional view of a main part of a conventional microphone, FIG. 2 is an
external view of a microphone according to an embodiment of the present invention, and FIG. 3
is a partial cross-sectional view of the main part of the same microphone.
8 иииииии Drive part, 8a иииииии Semiconductor laser, 8b ииииииии Photo detector, 10 ииииии Vibrating film, 12
иииииии Microlens , 14 ...... Optical fiber. Name of Agent Attorney Nakao Toshio Other 1 person Figure
1 M2 Figure 3
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