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JPS63302328

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DESCRIPTION JPS63302328
[0001]
TECHNICAL FIELD The present invention relates to an acoustic sensor that detects an acoustic
signal by replacing it with a change in light intensity using an optical phenomenon. 2. Related Art
In recent years, with the onset of practical use of semiconductor lasers and optical fibers, various
acoustic cells utilizing optical phenomena are being developed. Hereinafter, an example of the
above-mentioned conventional acoustic sensor will be described with reference to the drawings.
FIG. 2 is a block diagram showing the configuration of a conventional acoustic sensor. In FIG. 2, 1
is a controller, 2 is an optical fiber, 3 is a sensor head, FIG. 2B is an enlarged view of the sensor
head 3, 4 is a partially reflective coated film coated on the end face of the optical fiber 2, 6 is A
sound receiving and moving plate made of a silicon single crystal plate, 6 is a partially reflective
coating film coated on the sound receiving diaphragm 6, 7 is a support, and 8 is an organic
adhesive. The operation of the conventional acoustic sensor configured as described above will
be described below. In FIG. 2, a monochromatic light power emitted from a light source such as a
semiconductor laser included in the controller 1 passes through the optical fiber 2 and enters the
sensor head 3 utilizing the Fabry-Perot interference, and FIG. The light partially transmitted
through the end surface of the optical fiber 2 and the coated partial reflection coating film 4 is
coated on the inside of the receiving diaphragm 5 made of a silicon single crystal plate disposed
parallel to the end surface of the optical fiber 2 Repeated reflection interference occurs between
the partial reflection coating film 4 opposed to the film 6 with a constant gap, and interference
light modulated in intensity by the vibration of the sound receiving diaphragm 6 returns to the
optical fiber 2 again. , Controller 1 where it is converted to electrical signals by an opto-electric
converter such as a photodiode. The sound receiving diaphragm 6 is adhesively bonded to the
support 7 of the optical fiber 2 and the periphery thereof with an organic adhesive 8. Problems
to be Solved by the Invention However, in the configuration as described above, since the support
7 of the optical fiber 2 and the periphery of the sound receiving diaphragm 5 are bonded by the
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organic adhesive 8, the end face of the optical fiber 2 The gap of the receiving diaphragm 5
fluctuates with temperature and humidity, and an unstable 7-application / Perot interference
system is to be formed, which is not preferable in practical use. SUMMARY OF THE INVENTION
In view of the above problems, the present invention provides an acoustic senna that is resistant
to environmental changes such as temperature and humidity fluctuations. In order to solve the
above problems, in order to solve the above problems, the acoustic sensor according to the
present invention bonds the support for holding the optical fiber and the periphery of the
receiving diaphragm with a low melting point metal, and temperature and humidity To construct
a stable sensor head.
In the present invention, in the above-described structure, the optical fiber support and the
receiving diaphragm consisting of a silicon single crystal plate are bonded with a low melting
point metal, so that the two opposing surfaces necessary to construct an interference system The
distance between the acoustic sensor and the sensor is extremely stable with respect to
temperature and humidity, so that the operating point of the acoustic sensor is stable with
respect to temperature and humidity. Embodiment An embodiment of the present invention will
be described with reference to the drawings. FIG. 1 is a block diagram showing the structure of
an acoustic sensor in an embodiment of the present invention. In FIG. 1, the controller 1 and the
optical fiber 2 are the same as in the prior art, and 3 'indicates a sensor head. In FIG. 1B, 6 'is a
receiving diaphragm made of a silicon single crystal plate, and 9 is pb. It is a low melting point
metal binder made of a composition alloy of Sn and B. The same parts as those in the
conventional example shown in FIG. 1 and FIG. The operation of the acoustic sensor configured
as described above will be described below. First, monochromatic light power emitted from a
light source such as a semiconductor laser contained in the controller 1 passes through the
optical fiber 2 and enters the sensor head 3 'using the Fabry-Perot interference, and the end face
of the optical fiber 2 is The light partially transmitted through the coated partially reflective
coating film 4 is partially reflected by the partially reflective coating film 6 coated on the inner
side of a sound receiving diaphragm 5 ′ made of a silicon single crystal plate disposed parallel
to the end face of the optical fiber 2. The periphery of the silicon single crystal plate 6 ′ and the
support 7 of the optical fiber 2 are firmly bonded by the low melting point metal bonding
material 9. The light incident from the optical fiber 2 repeatedly causes reflection interference
between the partial reflection coating film 4 of the optical fiber 2 and the partial reflection
coating film 6 of the sound receiving diaphragm 5 ′, and returns to the optical fiber 2 again.
The light is converted to electricity. As described above, according to the present embodiment,
since the optical fiber support and the periphery of the sound receiving diaphragm S ′ are
joined by the low melting point metal bonding material 9, the Fabry-Perot interference
constituting the sensor head is made The system is extremely hot. It becomes a parallel plate
repetitive interference system stable against humidity, and provides a sensor with stable
performance, and its practical effect is large. In this embodiment, the sound receiving diaphragm
6 'is disposed as an acoustic sensor, but in principle, the same configuration can be used to
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measure the pressure, and the sound receiving diaphragm 6' may be used. It may be a silicon
diaphragm. Further, it is desirable that the low melting point metal bonding material 9 be a
material having a small thermal expansion coefficient and a small thermal strain. Further, as the
low melting point metal material, in addition to an alloy of Pb, Sn, and Bi, an alloy containing a
metal component such as C (1, In, Zn, Mb, etc.) may be used.
Effect of the Invention As described above, according to the present invention, an acoustic sensor
having extremely stable performance against temperature and humidity by bonding the support
of an optical fiber to the periphery of a silicon single crystal plate with a low melting point metal
material. The practical effects are great.
[0002]
Brief description of the drawings
[0003]
FIG. 1 is a block diagram showing the structure of an acoustic sensor according to an
embodiment of the present invention, and FIG. 2B is a block diagram showing the structure of a
conventional acoustic sensor.
3 '· · · · · · · sensor head, 5' · · · · · · · · Sound receiving diaphragm consisting of silicon single crystal
plate, 9 · · · · · · · · low melting point metal bonding material Name of agent Attorney Nakao Toshio
and other 1 person 3 ', Goppu 1 L' Figure 1 '-v 93 y single B ゞ JJ: y 5 A
1 99 99 渭 乞 侘 渭 乞
侘 $ 渭 乞 侘 ■ Fig. 2
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