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JPH11331989

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DESCRIPTION JPH11331989
[0001]
BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a
security intruder detection system for detecting an intruder by detecting changes in indoor gas
pressure caused by an intruder or a microphone used for a car phone, a cellular phone, an audio
microphone or the like. The microphones used in the
[0002]
2. Description of the Related Art An optical microphone for detecting membrane displacement
due to gas vibration as an electric signal is a condenser microphone including an electret
microphone, which has been overwhelmingly used in the conventional fields of automobile
phones, mobile phones and audio. On the other hand, it has advantages such as small size, low
power consumption, high sensitivity, high S / N ratio, selective frequency characteristics in the
audio sound wave band, no filter in the post circuit, and less noise to external electromagnetic
waves. Development is progressing as a new technology to be noted.
[0003]
A representative structure of this optical microphone is shown in FIG.
For the light emitting element 1, a red or infrared light LED manufactured by a semiconductor
process mainly using silicon, germanium and gallium arsenide is usually used, fixed to the
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substrate 3 with an adhesive or the like and opposite to the substrate 3. It is electrically
connected from the surface by the wire bonding technology using an extra-fine gold wire. As the
light receiving element 2, a phototransistor or a photo diode manufactured by a semiconductor
process having sensitivity to the electromagnetic wave emitted from the light emitting element 1
is used, and similarly, it is electrically connected to the substrate 3 by wire bonding. The light
emitting element 1, the light receiving element 2 and the wire are transparent to electromagnetic
waves emitted from the light emitting element 1 to prevent scientific deterioration due to
external gas and physical deterioration due to dust, dirt, foreign matter, etc. The periphery is
filled with a ceramic material such as a material. Further, in order to efficiently collect the
electromagnetic wave radiated from the light emitting element 1 in the exit window 8, this filling
material is coated on the outer surface with a material opaque to the electromagnetic wave, and
the light emitting element 1 and the light receiving element 2 Inside the filling material they are
separated by opaque separating walls 10 which form a light guide 9. A membrane 5 made of
metal or resin coated with the electromagnetic wave reflecting material is disposed on the top of
these.
[0004]
The electromagnetic wave emitted from the light emitting element 1 is reflected on the light
guide portion 9 formed of the resin, the coating 11 and the separating wall 10 directly or
internally, and the membrane is irradiated from the exit window 8. The electromagnetic wave
reflected by the membrane 5 reaches the light receiving element 2 again from the entrance
window 7 through the light guide 9 on the opposite side across the separation wall 10, and the
light receiving element 2 supplies the electromagnetic wave to the incident energy, or Convert to
electrical signal such as voltage and output. Here, it is known that there is a relationship shown
in FIG. 3 between the distance between the membrane 5, the exit window 8 and the entrance
window 7 and the electrical signal output. In order to read the displacement in the vertical
direction of the membrane 5 linearly by the electrical signal and read a slight displacement as a
change in the electrical signal, the slope of the curve of the function shown in FIG. desirable. In
FIG. 3, the region 13 is a portion corresponding to the inclination and is an expected operating
point.
[0005]
In order to obtain a more constant and larger inclination in FIG. 3, there is a form of a filler of
resin material such as resin under the membrane 5 or glass material as an element which can not
be ignored. When the membrane 5 vibrates by sound waves, it is desirable that the negative
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pressure from the lower part of the membrane 5 to the membrane 5 be as small as possible so as
not to prevent the vibration of the membrane 5. Is desirable. However, in the optical microphone,
since the light guide 9 is structurally located at the lower part of the membrane 5, this causes the
increase of the negative pressure, which hinders obtaining a more constant and larger inclination
in FIG. It had become. This effect is more remarkable as the distance between the outlet window
8 and the inlet window 7 and the membrane 5 is smaller and as the size of the filler is larger.
However, if the distance between the electromagnetic wave exit window 8 and the entrance
window 7 formed on the filler head and the entrance window 7 is increased, the operating area
of the microphone moves to the area 14 of FIG. Microphone performance becomes impossible. In
the structure of FIG. 2, the total area of the outlet window 8 and the inlet window 7 is set to 5%
or less of the membrane 5.
[0006]
The light guide structure shown in FIG. 4 is proposed as this solution. However, a relatively thin
cylindrical or rectangular column smaller than the light emitting element 1 and the light
receiving element 2 must be relatively molded, and there is a concern that the yield may be
deteriorated due to insufficient strength at the time of molding. In addition, the angle from the
light emitting element 1 to the exit window 8 and the angle from the light receiving element 2 to
the entrance window become smaller, resulting in a decrease in the electrical signal obtained
from the light receiving element 2, that is, a decrease in sensitivity.
[0007]
SUMMARY OF THE INVENTION The problem to be solved by the present invention is that in the
conventional optical microphone, structurally large elements that inhibit the vibration of the
membrane are obtained, and a constant and large signal output is obtained in the displacement
amount of the membrane It is.
[0008]
The total area of the exit window for irradiation and the entrance window for light reception is
5% or less of the area of the membrane, and the vertical cross-sectional shape of the
electromagnetic wave light guide portion of the optical microphone is concave 1.2. It is
characterized in that it includes multidimensional function curves of the following order or more.
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In addition, the sum of the critical angle of the light guide member material and the value of
twice the angle between the substrate and the tangent of the concave multi-dimensional function
curve of 1.2 or more of the light emitting element and light receiving element above is larger
than 180 degrees It is characterized by becoming.
[0009]
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS If the light guiding portion 9 has a
concave curve of 1.2 or higher as shown in FIG. 1, a wide space can be secured in the vicinity of
the membrane 5, the exit window 8 and the entrance window 7. The adverse effect of negative
pressure on the vibration of 5 can be reduced. Further, since the outer side of the light guide 9 is
formed of a continuous curve, the gas in the vicinity is moved smoothly, and the linearity of the
signal output is improved. Assuming that the angle between the tangent of the curve and the
substrate is α, light emitted in the vertical direction from the light emitting element is reflected
by the curve, and the incident angle when reaching the exit window 8 is 180−2α. If this angle is
smaller than the critical angle of the light guide member material, it is emitted to the outside
from the exit window 8. That is, when the sum of 2α and the critical angle is larger than 180
degrees, light emitted in the vertical direction from the light emitting element is emitted to the
outside from the exit window 8. When an LED is used as a light emitting element, the LED has the
largest amount of light in the vertical direction. The same applies to the light receiving element
according to the Ferma principle, and the light emitted from the exit window is incident from the
entrance window and effectively reaches the light receiving element.
[0010]
The present invention will be described in detail with reference to the following examples.
[0011]
If a curve portion forming the vertical cross section of the light guide 9 shown in FIG. 1 is
extracted and an arbitrary point is taken as a two-dimensional origin as shown in FIG. 5 and X
and Y axes are determined, the curve -B) It can be seen that a curve that can be represented by 2
= (y-c) (a, b and c are arbitrary real numbers) is included.
As described above, when the curve including the concave quadratic function is present in the
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cross section of the membrane light guide 9, the vibration of the membrane is not inhibited.
[0012]
Although a quadratic function is used to form the curve in FIG. 1, if the curve portion is not a
linear function or more, that is, n in the equation a (x-b) 2 = (y-c). If> 1, some effect can be
expected and if n is 1.2 or more, it is more effective.
[0013]
The refractive index of the light guide member takes a value near 1.5.
When the refractive index is 1.5, the critical angle is 42 °. From this, if the angle between the
tangent of the curve and the substrate is larger than 69 °, the light emitted from the light
emitting device in the vertical direction is emitted from the exit window to the outside and
effectively used.
[0014]
According to the method described in the present invention, more linear output and higher
sensitivity can be obtained with respect to the conventional optical microphone, and industrial
value in the field is recognized.
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