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JP2001169398

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DESCRIPTION JP2001169398
[0001]
BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an
acousto-electric conversion device for converting vibration displacement of a diaphragm into an
electrical signal using light.
[0002]
2. Description of the Related Art An optical microphone device is known as a representative of an
acoustoelectric converter. FIG. 3 is a cross-sectional view showing the configuration of the head
portion of the optical microphone device according to the separate application of the inventors of
the present invention. The light emitting element 3 and the light receiving element 4 are placed
on the substrate 5 so that the light emitting surface and the light receiving surface are parallel
and substantially flush with each other without giving an angle to the substrate 5. A light beam is
emitted from the light emitting element 3 to the diaphragm 2 substantially perpendicularly to the
light emitting surface. Here, the diaphragm 2 is stretched at a predetermined angle θ with
respect to the substrate 5 in the head 1 at fulcrums 7 and 8. Further, the light beam from the
light emitting element 3 is reflected by the diaphragm 2 so that the angle between the incident
light and the reflected light reaching the light receiving element 4 is set to be the same as the
inclination angle θ of the diaphragm 2.
[0003]
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1
By mounting the light emitting element 3 and the light receiving element 4 flatly on the substrate
5 as described above, mass productivity can be improved. Here, when a vertical surface emitting
type light emitting element (VCSEL) is used as the light emitting element 3 normally, emitted
light in a direction perpendicular to the light emitting surface can be obtained. The light
receiving element 4 is inclined at the reflected light incident thereon, but in general the light
receiving element does not deteriorate much in sensitivity to the incident angle of the received
light as compared with the light emitting element, and the incident angle is necessarily
perpendicular to the light receiving surface Even if it does not become, light reception efficiency
does not deteriorate remarkably.
[0004]
FIG. 4 is a view for explaining the operation of the head portion of the optical microphone device
shown in FIG. The luminous flux L1 of the light beam emitted from the light emitting element 3
strikes a predetermined area of the diaphragm 2 stretched at an angle inclined by θ with respect
to the substrate 5, and is reflected here to become a reflected luminous flux L2 to become the
light receiving element 4 Incident to At this time, as the diaphragm 2 vibrates by the sound wave
6, the reflected light beam L2 changes depending on the size of the vibration displacement as
shown by the solid line, the broken line and the chain line in the figure, and enters different light
receiving surfaces of the light receiving element 4. Therefore, the vibration displacement of the
diaphragm 2 can be detected by detecting the magnitude of the light signal at the light receiving
position. As described above, in the optical microphone device shown in FIG. 3 and FIG. 4, light
reception / emission is performed by one light emitting element 3 and one light receiving
element 4 mounted in a planar shape on the substrate 5.
[0005]
As described above, in the optical microphone device having the structure as shown in FIGS. 3
and 4, the luminous flux from the light emitting element 3 irradiated to the diaphragm 2 is
usually about 5 to 10 degrees. Since the light is spread and irradiated and reflected by the
diaphragm 2, the reflected light may be expanded and irradiated to places other than the light
receiving surface of the light receiving element 4. In addition, due to the vibration of the
diaphragm 2, the focal point of the reflected light may not necessarily be determined on the light
receiving surface of one light receiving element 4, and the light receiving efficiency may be
lowered. Also, in some cases, the optical axis of the light beam emitted from the light emitting
element 3 does not always rise perpendicularly to the radiation surface. Therefore, simply
05-05-2019
2
providing only one light receiving element 4 for receiving the reflected light at a fixed position
with respect to the substrate 5 has a problem that all the reflected light can not be efficiently
received. The present invention was made to solve the problems described above, and it is an
object of the present invention to provide an acoustoelectric conversion device capable of
efficiently receiving reflected light from a diaphragm and enhancing acoustoelectric conversion
efficiency. Do.
[0006]
In order to achieve the above object, an acoustoelectric converter according to the present
invention comprises: a diaphragm that vibrates by sound pressure; a light emitting element that
emits a light beam to the diaphragm; and the vibration. Acoustoelectricity comprising a light
receiving element which receives the reflected light of the light beam irradiated to the plate and
outputs a signal corresponding to the vibration displacement of the diaphragm, and a substrate
on which the light emitting element and the light receiving element are installed. In the
conversion device, the light emitting element and the plurality of light receiving elements are
disposed on the substrate such that the light emitting surface of the light emitting element and
the light receiving surface of the light receiving element are parallel and substantially flush with
each other. The plate is inclined at a predetermined angle with respect to the substrate, the light
beam emitted substantially perpendicularly from the light emitting element to the light emitting
surface is irradiated to the diaphragm, and the reflected light from the diaphragm is reflected by
the diaphragm. Received by multiple light receiving elements Characterized in that it.
[0007]
In the acoustoelectric conversion device, the plurality of light receiving elements can be linearly
arranged with respect to the light emitting element.
Further, in the acoustoelectric conversion device, the plurality of light receiving elements can be
arranged in a circular shape or a rectangular shape. Furthermore, in the acoustoelectric
conversion device, a plurality of the light emitting elements can be arranged. Further, in the
acoustoelectric conversion device, a region of the diaphragm to be irradiated with the incident
light can be a mirror surface.
[0008]
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3
BEST MODE FOR CARRYING OUT THE INVENTION Embodiments of the present invention will be
described in detail below. Although the acoustoelectric conversion device of the present
invention is applicable to an optical microphone device, it is not necessarily limited to this, and
can also be used as an acoustic sensor or the like. However, the embodiment described below
describes the case where the present invention is applied to an optical microphone device. FIG. 1
is a view showing the configuration of a head portion of an optical microphone device which is
an example of the embodiment of the present invention. The same reference numerals are given
to the same parts as shown in FIG. 3 and FIG. 4, and the detailed configuration will not be
described. In the present invention, the light receiving element 4 shown in FIG. 3 or 4 is divided
into a plurality of pieces, and the divided light receiving elements 41, 42, 43,... 4n are arranged in
a predetermined shape. As described above, by using the plurality of light receiving elements 41,
42, 43,... 4n, the spread of the light flux of the reflected light L2 reflected by the diaphragm 2 can
be entirely absorbed and received.
[0009]
In the embodiment shown in FIG. 1, since only one light emitting element 3 is provided and a
plurality of light receiving elements 4 are provided, it is possible to absorb and receive all the
reflected light L2 of the radiation beam from this light emitting element 3 Become. The
arrangement of the light receiving elements 4 may be linear with respect to the light emitting
elements 3 as shown in FIG. 2 (A). For example, as shown in FIG. 2 (B), a plurality of light
receiving elements 41. It is also possible to arrange 4n in a circular shape, and also to arrange in
a rectangular shape as shown in FIG. 2 (C). Not only the light receiving element 4 but also the
light emitting element 3 can be divided and arranged.
[0010]
FIG. 2D shows a case where the light emitting elements 3 are divided and linearly arranged in the
same manner as the light receiving elements 4. Further, FIG. 2E is a circular shape, and FIG. 2F is
a rectangular shape, and the light emitting elements 3 are divided and disposed. The luminous
efficiency can be further increased by providing the plurality of light emitting elements 3 in a
divided manner as described above.
[0011]
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4
FIG. 5 is a view showing the surface shape of the diaphragm 2. When a vertical surface light
emitting element (VCSEL) is used as the light emitting element 3, the light from the light emitting
surface is concentrically emitted with uniform light emission intensity, so the light receiving
surface of the diaphragm 2 is mirror-finished in an annular shape. This will improve the
reflection efficiency there. The hatched area 2a in FIG. 5 indicates the area thus mirror-finished.
Further, as shown in FIG. 5B, it is also possible to mirror-finish only the spot-like area 2b on
which the light beam strikes. The area 2 c represents a positioning point when the diaphragm 2
is stretched on the supporting points 7 and 8.
[0012]
As described above, in the acoustoelectric converter according to the present invention, at least a
plurality of light receiving elements are provided flatly on the substrate, and reflected light from
the light emitting elements can be received without excess or deficiency. Therefore, an
acoustoelectric conversion device with high light receiving efficiency can be realized. Further, the
thermal noise of each element can be suppressed by dividing the light receiving element into a
plurality and providing a plurality of elements, so that the SN ratio can be comprehensively
improved.
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