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JP2002191096

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DESCRIPTION JP2002191096
[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.
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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 light emitting elements 201 and light receiving elements 202 are provided in
contrast to 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, there is a problem that the signal to noise ratio (S / N) ratio in the state where the
diaphragm 203 is completely closed is deteriorated due to the light leakage 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 In an
acoustoelectric conversion device for detecting a vibration displacement due to a sound of a
diaphragm by receiving reflected light by a light receiving element and extracting it as an electric
signal, an upper surface of a light shielding housing and a diaphragm in which a light emitting
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2
element and a light receiving element are provided And a center portion of the light emitting
diode is formed into 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,
a light shielding plate for dividing the light shielding housing into a light emitting cavity on the
light emitting element side and a light receiving cavity on the light receiving element side is
installed, a light emitting window is provided above the light emitting cavity, and a light receiving
window Can be provided.
[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 and the light receiving
element 105 are 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, whereby vibration displacement of the diaphragm 103 due to sound is
generated. It is configured to detect
[0007]
In the embodiment in FIG. 1, the light emitting element 104 and the light receiving element 105
are disposed on the bottom surface of the light shielding housing 106 so that the light from the
light emitting element 104 and the light to the light receiving element 105 do not leak to the
outside. It is surrounded by the inner wall. Further, the light shielding housing 106 is divided by
the light shielding plate 112 into a light emitting cavity 107 with the light emitting element 104
and a light receiving cavity 116 with the light receiving element 105. The light blocking plate
112 blocks both cavities and plays a role of preventing light leakage between the light emitting
cavity 107 and the light receiving cavity 116. Furthermore, in order to irradiate light to a limited
portion of the diaphragm 103, a light emission window 115 is provided above the light emission
cavity 107.
[0008]
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The light emitted from the light emitting element 104 by the power supplied from the power
supply unit 108 passes through the slit of the light emitting window 115 provided above the
light emitting cavity 107 and is irradiated to the diaphragm 103. A slight gap, that is, a clearance
110 is provided between the diaphragm 103 and the light shielding housing 106, and light
emitted from the light emitting element 104 to the diaphragm 103 through the light emission
window 115 is the clearance 110. It is reflected and emitted. The reflected light 111 reflected by
the diaphragm 103 passes through the slit of the light receiving window 114 provided above the
light receiving cavity 116 and is irradiated to the light receiving element 105. 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.
[0010]
As described above, according to the present invention, it is possible to prevent light leakage
from the light emitting element and light leakage 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.
[0011]
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
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structure suitable for high performance and mass production.
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