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JP2002191095

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complete, reliable or fit for specific purposes. Critical decisions, such as commercially relevant or
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DESCRIPTION JP2002191095
[0001]
BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an
acoustoelectric conversion device such as a microphone device, and more particularly to
acoustoelectric conversion which converts vibration displacement of a diaphragm due to sound
into an electrical signal corresponding to a change in light reception amount. It relates to the
device.
[0002]
2. Description of the Related Art A microphone speech conversion system in the prior art is put
to practical use mainly with a condenser and a dynamic system. The capacitor system converts a
change in capacitance into an electrical signal and takes it out as sound. The vibration plate
(polymer film) vibrates in the vertical direction due to the strength of the sound wave, and the
electrostatic capacitance between the electrodes changes the capacitance when the vibration
plate vibrates, and an electric signal is output according to the amount of change. In the dynamic
method, a coil is provided perpendicularly to the diaphragm, and an induction coil is provided on
a magnetic circuit corresponding to this coil on one side, and the diaphragm coil vertically
vibrated by sound waves is generated between the induction coil and the coil. Power is generated
and output as an audio signal. The above two types of electrical conversion systems still play a
central role in the field of microphones as prior art, and electrical conversion systems using light
are also proposed and put to practical use research. In the electrical conversion method using
light, light is applied to a diaphragm, and light reflected from the diaphragm is received by a light
receiving element, converted electrically, and output.
05-05-2019
1
[0003]
FIG. 2 is a view for explaining the prior art of an electrical conversion system using light. In the
figure, a pair of a light emitting element 201 and a light receiving element 202 are provided to
face the diaphragm 203, and a light shielding plate 204 for shielding light is provided at the
center. The light emitted from the light emitting element 201 is irradiated to the diaphragm 203.
Then, the amount of reflected light corresponding to the amount of change in vertical vibration
of the diaphragm 203 is input to the light receiving element 202, converted as an electric signal,
and output (electric output 207) through the amplifier 205. Power to the light emitting element
201 is supplied by the power supply unit 206.
[0004]
As shown in FIG. 2, the shape of the diaphragm 203 in the prior art is a plane. In addition, since
the diaphragm 203 is formed in a circular shape, the vibration distribution shows a maximum
vibration at the central portion, and the vibration width decreases toward the outside. Therefore,
the light passing through the light transmitting slit 208 formed between the diaphragm 203 and
the light shielding plate 204 opposed thereto and transmitting light is light at the central portion
and the outside of the diaphragm 203. It was not uniformly distributed and was a cause of light
leakage. Then, due to the light leakage, there is a problem that the S / N ratio (Signal to Noise
Ratio) in a state in which the diaphragm 203 is completely closed is deteriorated and the sound
is deteriorated. The present invention has been made to solve the problems of the diaphragm
used in the above-described conventional acoustoelectric converter, and is an acoustoelectric
converter including a diaphragm having high performance and suitable for mass production, and
a light shielding housing structure. Intended to provide.
[0005]
SUMMARY OF THE INVENTION According to the present invention, a light emitting element and
a light receiving element are disposed opposite to a thin film diaphragm stretched on a support
member, and light emitted from the light emitting element to the diaphragm is An acoustoelectric
conversion device for detecting vibration displacement due to sound of a diaphragm by receiving
reflected light by a light receiving element and extracting it as an electric signal, comprising a
light shielding housing having a light emitting element internally provided at the center of the
05-05-2019
2
bottom surface; And the central portion of the diaphragm are formed in a dome shape, and a
clearance for uniformly transmitting light is provided between the diaphragm and the light
shielding housing. In the acoustoelectric conversion device, the light emitting window can be
provided in the upper portion of the cavity of the light shielding housing, and the light receiving
element can be circumferentially provided in the upper outer wall of the light shielding housing.
[0006]
BEST MODE FOR CARRYING OUT THE INVENTION Embodiments of the present invention will be
described in detail below. FIG. 1 is a cross-sectional view showing the shape and structure of a
diaphragm used in the acoustoelectric converter according to the present invention. The acoustoelectric conversion device shown in FIG. 1 has a thin thin film diaphragm 103 such as aluminum
foil stretched on a circular ring-shaped support member having an opening at the center, and a
light emitting element at a position facing this diaphragm 103. 104 is disposed, light is emitted
from the light emitting element 104 to the diaphragm 103, and the reflected light of this light is
received by the light receiving element 105 and taken out as an electric signal to detect vibration
displacement due to the sound of the diaphragm 103. It is configured.
[0007]
In the embodiment in FIG. 1, the light emitting element 104 is disposed at the center of the
bottom of the light shielding housing 106, and is surrounded by the inner wall of the light
shielding housing 106 so that the light from the light emitting element 104 does not leak to the
outside. A light emitting window 115 is provided above the cavity 107 of the light shielding
housing 106 in which the light emitting element 104 is provided. The light emitted from the light
emitting element 104 by the power supplied from the power supply unit 108 is irradiated to the
diaphragm 103 at an angle having a radiation angle 102 of light, and the diaphragm 103
vibrated by a sound wave or the like is vertically vibrated.
[0008]
A slight gap, that is, a clearance 110 is provided between the diaphragm 103 and the light
shielding housing 106, and the light emitted from the light emitting element 104 to the
diaphragm 103 is reflected to the clearance 110 to be received as a light receiving element. It is
irradiated to 105. Here, in order to cause the light reflected by the clearance 110 to be reliably
05-05-2019
3
irradiated to the light receiving element 105, the light receiving element 105 is provided
circumferentially on the outer wall upper portion (the clearance 110 side) of the light shielding
housing 106. The light receiving element 105 converts the irradiated light into an electrical
signal, which is amplified by the amplifier 109 and output as an audio signal. As one of the
features of the present invention, the central portion of the diaphragm 103 is formed in a dome
shape. The upper surface of the light shielding housing 106 at a position facing the central
portion of the dome-shaped diaphragm 103 is also molded into a dome shape.
[0009]
As shown in FIG. 1, by forming the diaphragm 103 and the upper surface of the light shielding
housing 106 in a dome shape, the gap between the diaphragm 103 and the light shielding
housing 106 corresponding to the vibration of the diaphragm 103, ie, It is possible to keep the
clearances 110 parallel. When the clearances 110 maintain the parallel state, the clearances 110
change according to the vibration width of the diaphragm 103. Thus, uniform light can be
transmitted to the light receiving element 105. As described above, according to the present
invention, it is possible to prevent light leakage from the light emitting element and efficiently
propagate light to the light receiving element. Furthermore, according to the present invention, it
is possible to propagate light uniformly, so that the S / N ratio is improved, and a good audio
signal can be output. Furthermore, the acoustoelectric conversion device according to the present
invention has an advantage of being excellent in productivity because its structure is simple.
[0010]
As described above in detail, according to the present invention, it is possible to provide an
acoustoelectric conversion device provided with a diaphragm and a light shielding housing
structure suitable for high performance and mass production.
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