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JPS63260398

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DESCRIPTION JPS63260398
[0001]
BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to
microphones used in audio equipment, and more particularly, to microphones that directly
convert sound waves such as music into digital electrical signals. (Prior Art) A conventional
system for inputting a sound wave such as music as a digital electric signal to a digital audio
device will be described with reference to FIG. FIG. 3 is a block diagram of a signal processing
circuit for converting an analog electrical signal of a microphone into a digital electrical signal. In
the figure, the sound wave S is converted into a minute analog electrical signal by the
microphone 1 to which it is inputted, amplified to a level that can be transmitted by the
microphone amplifier 2, and passes through the transmission path 3 and indicated by a dashed
frame in the figure. Are input to the digital audio device 4. The analog electrical signal input to
the digital audio device 4 is amplified to a level capable of being sampled by the amplifier 5 and
then unnecessary harmonic components are reduced by the low pass filter 6 in order to prevent
occurrence of aliasing distortion due to alias effect at the time of sampling. Is removed. The
analog electrical signal from which the unnecessary harmonic components have been removed is
sampled and held by the sample and hold amplifier 8 by the sample and hold control signal C
output from the clock generator 7 and then output from the clock generator 7 described above.
The conversion start signal is output as the digital electric signal E by the analog-to-digital
converter 9. (Problems to be Solved by the Invention) However, in the above configuration, there
is a problem that it is difficult to obtain the analog to digital converter 9 which is expensive and
has stable performance. Furthermore, since the output of the microphone passes through the
transmission path 3 in the form of an analog signal, noise is likely to be mixed in. There is also a
problem that distortion is likely to occur because the amplification is repeated. The present
invention solves the above problems, and provides a microphone that can convert sound waves
such as music into digital electrical signals and directly supply them to digital audio equipment
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without the need for complicated signal processing circuits. It is. (Means for Solving the
Problems) In order to solve the above problems, the present invention comprises a light source
having an irradiation angle, and a portion which is disposed orthogonal to the optical axis and
which absorbs or transmits light at the center. ,Also. A microphone from a diaphragm in which
light reflecting portions are respectively formed on the upper and lower sides, and a light
receiving portion including a plurality of light receiving elements arranged in a line in the vertical
direction for receiving the reflected light from the diaphragm and converting it into an electric
signal And replace the displacement in the front-rear direction of the diaphragm vibrated by the
sound wave with the change in the distance from the light source to the light receiving unit
through the diaphragm and as the change in the light receiving width of the reflected light in the
light receiving unit The light receiving range of the light receiving elements arranged in a row is
detected, and the vibration of the diaphragm by the input sound wave is output as a digital
electric signal.
(Operation) With such a configuration, for example, using a light source having an irradiation
angle of angle 2α, if the diaphragm causes a positional change of ΔX in the front and back
direction by sound waves, vibration from the fixed light source and light receiving portion The
distances to the plates change by ± ΔX respectively. Assuming that the maximum incident angle
of light irradiated to the diaphragm is α and its reflection angle is β, the above incident angle α
and reflection angle β are always constant if the diaphragm is displaced forward by ΔX without
deformation. Therefore, the irradiation circle diameter on the diaphragm is expanded by 2Δx tan
α, and the reflection light irradiation circle diameter on the light receiving portion is increased
by 2Δx (tan α + tan β). Conversely, if the light is displaced backward by ΔX, the reflected light
irradiation circle of the light receiving portion becomes smaller by 2Δ) c (tan α + tan β).
Therefore, the vibration of the diaphragm due to the sound wave is a change in the light
receiving width of the light receiving unit, and the change in the light receiving width is detected
as a light receiving range of a plurality of light receiving elements arranged in a row, and the
number of elements received is counted. To convert into digital electrical signals. An embodiment
according to the present invention will be described with reference to FIGS. 1 and 2. FIG. 1 (a), (b)
and (c) respectively show a side sectional view of the microphone according to the present
invention, and a rear sectional view cut along the AA 'plane and the BB' plane and seen from the
direction of the arrow and It is a front sectional view. In FIG. 1 (a), the microphone according to
the present invention is provided inside the cylindrical casing lO so as to be orthogonal to its
center line, and as shown in FIG. 1 (b), along the horizontal center line. A diaphragm 11 having a
belt-like portion 11a for absorbing or transmitting light and a half moon-shaped portion 11b for
reflecting light on both upper and lower sides thereof, and a predetermined irradiation angle 2α
toward the diaphragm 11; The light sources 12 whose optical axis coincides with the center line
of the housing 10 and the light receiving elements 13 arranged in a line in the vertical direction
as shown in FIG. 1 (C) disposed behind the light sources 12. A light receiving unit 14 such as a
line image sensor or the like is disposed in order. In addition, the absorption or transmission part
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formed in the diaphragm 11 is. , And the reflected light is set so as not to return to the light
source 12. Further, the relative positions of the diaphragm 11, the light source 12 and the light
receiving unit 14 are set so that the reflected light from the light source 12 having the irradiation
angle 2α covers the array range of the light receiving elements 13 of the light receiving unit 14
at the maximum amplitude position. ing. The operation of the thus configured microphone will be
described. The diaphragm 11 is vibrated by the sound wave S. As indicated by a broken line in
FIG.
The change in the distance from the light source 12 to the light receiving portion 14 after being
reflected by the diaphragm 11 corresponds to twice the displacement distance. Since the
diaphragm 11 only moves back and forth without deformation, assuming that the irradiation
angle is 2α, the maximum incident angle α to the diaphragm 11 and its reflection angle β do
not change. The light receiving width changes in proportion to twice the displacement distance of
the diaphragm 11. By detecting and calculating the light receiving range of the light receiving
element 13 generated by this, it is possible to convert the vibration of the diaphragm 11 into a
digital electric signal. FIG. 2 is a block diagram for inputting a music signal from the microphone
of the present invention to a digital audio device. In the figure, the sound wave S is converted
into a digital electric signal by the microphone 15 according to the present invention to which it
is inputted, and is inputted to the digital audio equipment 17 shown by a dashed frame in the
drawing through the transmission line 16. In the digital audio device 17, the latch circuit 19
temporarily holds the input digital electric signal at a constant interval by the latch clock signal A
based on the sampling frequency output from the clock generator 18, and then the digital music
signal B is generated. Output as This digital music signal B is equivalent to the digital music
signal E shown in FIG. In addition, if the diaphragm 11 of the microphone has the characteristics
of a low-pass filter having a cutoff frequency equal to or less than 1/2 of the sampling frequency
when the output signal of the microphone is processed by the digital audio device, sampling can
be performed. No aliasing distortion occurs due to the accompanying alias effect. (Effects of the
Invention) As described above, according to the present invention, a digital electrical signal
necessary for digital audio equipment can be obtained with a circuit configuration much simpler
than that of processing by a conventional analog-to-digital converter. be able to. Also, since the
output of the microphone is a digital electrical signal, there is no mixing of noise during
transmission to other devices, and no amplifier is required, so no distortion occurs other than the
distortion generated by the microphone itself.
[0002]
Brief description of the drawings
[0003]
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1 (a), (b) and (C) are side cross-sectional views of the microphone according to the present
invention, a back cross-sectional view cut along AA 'and a front cross-sectional view cut along
BB', FIGS. FIG. 3 is a block diagram showing a method of supplying music signals from the
microphone according to the present invention and the conventional microphone to the digital
audio equipment.
1.15: microphone 2 .: microphone amplifier 3.16: transmission line 4.17: digital audio device 5:
amplifier 6: low pass filter 7, 18 ... clock generator, 8 ... sample and hold amplifier, 9; ... analog to
digital converter, IO ... housing, 11 ... diaphragm, 11a ... absorption or transmission part, llb ...
Reflective part, 12 ... light source, 13 ... light receiving element, 14 ... light receiving part, 19 ...
latch circuit. Fig. 1 (a) I) 1 f rest 11 Jil '7 & 11a-CILH or 1 com ms + 1 1 b-J radiation 12; = light
source 13. ------------------------------------------------------------------------------. 3 Fig. 1-Fig. 2-2, Microholer 5
system No. 3-1-1 = Folk 4,, Digital 4-digital instrument 5-0 amplifier 6,-Low noise filter 7-Black・
・ ・ 光 生生 益 8-9. サンプル
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