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DESCRIPTION JPS5915394

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DESCRIPTION JPS5915394
[0001]
The present invention relates to a microphone device that uses laser light to digitally output
displacement of a diaphragm. In conventional microphones, for example, dynamic microphones,
voice coils are added to the diaphragm, inertia occurs due to the weight of the coils, and free
movement of the diaphragm is impeded, resulting in sacrifice of the transient characteristics as a
microphone. I have to. In addition, since the condenser microphone has a small internal capacity,
the impedance in the low band is high, and when the connection with the amplifier is lengthened,
there is a disadvantage that the feeling m is lowered due to the line capacitance. An object of the
present invention is to provide a microphone device capable of digital transmission with high
sensitivity and high sensitivity without any additional mass to the diaphragm except for the
above-mentioned disadvantages of the prior art. In order to achieve this object, the present
invention irradiates a laser beam to a diaphragm and utilizes the interference between the
reflected light and the 97 allens light to digitally read the displacement of the diaphragm. There
is a feature. Hereinafter, an embodiment of the present invention will be described with reference
to the drawings. FIG. 1 is a block diagram showing an optical system in an embodiment of the
microphone device according to the present invention, 1 is a laser source, 2 is a collimator lens, 3
is a The half mirror 14 is a fixed reflecting mirror, 5 is a diaphragm, 7 is an interference mark,
8?, Bb slit, 9?, 9b are light detectors. The diaphragm 5 is supported by a support means (not
shown) as with a normal microphone, but no accessory is provided except that the back surface
forms a reflection surface. Next, the operating pressure of this optical system will be described.
In FIG. 1, a laser source IJ: irradiated laser light is converted into parallel light by the collimator
lens 2 and reaches half mirror-3. Here, half of the laser beam passes through the half mirror 3 as
it is to the diaphragm 5. On the other hand, the other half of the laser light is reflected by the / S7 mirror 3 and directed to the fixed reflecting mirror 4, and thereby totally reflected back to the
half mirror 3 again. Another half of the return light passes through the half mirror 3 and travels
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to the slits 8? and Bb. On the other hand, the laser beam directed to the diaphragm 5 is totally
reflected by the diaphragm 5 and returns to the half mirror 3 again, and a further half of the
returned light is reflected by the half mirror 3 to the slits 8? and Bb. Here, laser 1 ? half
mirror-3 ? fixed reflecting mirror 4 ? half mirror 3 ? laser light passing through the optical
path length L1 of slit 8?, Bb and laser 1 ? half mirror-3 ? sliding plate 5 ? half mirror 3 ?
Slits) 8cL, 8b, and the laser beam having passed through the optical path is slit 8?, 8b, and 1111
with an optical path length of 11. , L, interfere with each other according to the difference
between them, resulting in interference 7.
That is, the interference fringe 7 is bright where the difference between the light path length L1
and the half wavelength (v2) of the wavelength ? of the laser 1 is ?1 and where the difference
is an odd multiple of the half wavelength, dark interference 7 occurs. 2, since the optical axis of
the reflected wave 11.12 is inclined because it is inclined within the range 1o indicated by the
broken line in FIG. 1, while the wave front of the fixed reflecting mirror 40 reflected wave is It is
inclined with respect to the wave front of the reflected wave 11 of the plate 5. In FIG. 2, the peak
of each wave of each reflected wave 11.12 is indicated by a solid line, and the valley is indicated
by a broken line. Therefore, at the point 7a where each wave mountain and the mountain
overlap, it is bright, and at the point 7b and 7c where the mountain and the valley overlap, dark
interference fringes 7 occur. The distance d between the interference fringes 7 (the distance
between the bright point and the dark point) is determined by the angle ? and the wavelength
? of the laser light, which is expressed by the following equation. On the other hand, the
interference fringes 7 have the optical path lengths Ll and L! of the respective laser beams.
Changes synchronously with each change of the wavelength ? of 17-the light, and therefore,
when the diaphragm 6 is displaced by ? / 2, it changes by one circle period. (Slit width <d) is
provided at the position shown in FIG. 2, and the number of bright portions of interference
stripes passing through the slit 8? is forced by 1 to minimize the displacement of the vibration
4N 5 by ?. It can be measured at an angle of 2/2 (step length). However, since it is not possible
to detect the moving direction of the diaphragm 5 with one it is provided with Surin 8a, in order
to be able to detect one moving direction also by work, an integral multiple of d / 2 from the slit
8? The slit Bb (slit width <d) is provided at the position where That is, Surin) Etc L, 8b is an
integer multiple of d / 2 on a straight line perpendicular to one of the optical axes of the
reflected waves 11.12 on the plane including the respective optical axes of the reflected waves
11 ░ 12. Provided at intervals of In FIG. 2, the straight line is shown as being perpendicular to
the reflected wave b). The signal passing through the slit 8? and the signal passing through the
slit 8b are 90 ░ out of phase 11 so that displacement of both diaphragms 50 in the diaphragm
50 can be detected by using these two ?) signals. . That is, when the diaphragm 5 is displaced to
the right with respect to the paper surface in FIG. 1, the interference fringe 7 moves to the right,
so the signal detected by the photodetector 9? is delayed by 90 ░ and the photodetector is 9b
is detected, but conversely ta! When the + I + plate 5 is displaced to the left, the moving power
direction of the interference fringes is reversed. As a result, the output phase relationship
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between the detectors 9a and 9b is also reversed.
FIGS. 3 (A), (B), (e) and (11) are explanatory views showing the relationship between the
displacement of the diaphragm in FIG. 1 and the pickling of the outputs of the respective
photodetectors. In FIG. 3A, the horizontal axis is time t, and the vertical axis is displacement IQ /
= in the direction of the optical axis X of the diaphragm 5 (FIG. 1), and a period from 1-0 to t-T2
&; The moving plate 5 is displaced from the first stage to the first to the right direction (ie, dt /
dt:> O) L from the first stage to the second stage, from the second stage to the second stage! On
the other hand, it indicates that displacement (toward dz / dt <0) I? is made in the left direction.
FIG. 3 (B) shows the output signal of the photodetector ga, 9b (FIG. 1) in the period of 0 ? t ? T,
and from the detector 9a, the output signal g CL ? shown by a solid line is Also, an output signal
9b 'indicated by a dotted line is obtained from the detector 9b. The phase of the output signal
9? 'is 90 ░ ahead of the output signal 9b in a period of 0 ? t $ T, and is 90 ░ out of phase in a
period of T, ? t ? T. At t-T, the phase relationships reverse each other. 3 (C) shows the digital
signal 9? obtained by waveform shaping the output signal 9? ░ of FIG. 3 (B), and FIG. 3 (D)
shows the waveform of the output signal 9b ░ similarly. The resulting digital signal 9 b ? ? is
shown. The digital signals 9a ? ? and 9b ? ? are pulses of one dark period by the
displacement of ? / 2 of the diaphragm 5, and the pulse cycle changes according to the
displacement velocity dt / dt of the diaphragm 5, and the diaphragm The phase relationship
between the digital signals 9? and 9b differs according to the direction of displacement force of
5. , 1 while digital signal 9a 7.9. . 1, the diaphragm 50 is in a temporally displaced state, so that
the audio information 6 (FIG. 1) is completely represented (1). Therefore, digital signals ga :, g;
including the audio information 6 are transmitted through the transmission system. Such digital
<N No. 9? ". Since 9b ? ? is less affected by noise in the transmission system and less in loss
etc., voice information can be transmitted faithfully. FIG. 4 is a block diagram showing a specific
example of the digital signal demodulation circuit shown in FIGS. 3 (C) and 3 (D), wherein 13.14
is an input terminal, 15 is a D7 rib 70-tub circuit, and 16 is a switch. A switch 17.18 is a voltage
source, 19 is an adder, 20 is a monostable multivibrator (i.e. 21 is a sample hold circuit, 22 is a
low pass filter, and 23 is an output terminal. 5 (A), (B), (C), (1), (B) and (F) are signal waveforms
showing the signals of the respective parts of FIG. 4 and are not shown in FIG. The same symbols
are attached to the corresponding signals.
Next, the operation of this specific example will be described. In FIG. 4 and FIG. 5 (A) or FIG. 5 (F),
the digital signal 91 shown in FIG. 3 (C) is supplied to D as a clock signal at the clock terminal
CKK of the 7-rip 7 quad circuit 15. The digital signal 9b "shown in FIG. 3 (D) is supplied as a data
signal to the data terminal of the D% 7 ring 70 circuit 15. The D7 lead prop circuit 15 holds the
level of the digital signal 9b 'at the leading edge of the digital signal 91. Therefore, as the Q
output C of the D7 pull 70 circuit 15, the digital signal 91 is the digital signal 9b ',! Also, when
the phase is 90 ', that is, when dt / dt) o, it goes low, and when dt / dt 0, it goes high. Note that
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the Q output C represents the direction of displacement of the diaphragm 5 (FIG. 1). The output C
controls the changeover switch 16. The fixed contact of the changeover switch 16 is connected
to the voltage source 17 of positive DC voltage and the voltage source 18 of negative DC voltage
respectively, and when Q output C is at low level, the changeover switch 16 is on the voltage
source 17 side. And close to the voltage source 18 side when Q output C is high level. The
voltage from the changeover switch 16 is supplied to the t11 zambre hold circuit 21 by the
addition of the output of the sample and hold circuit 21 in the adder 19 and is supplied first. This
N5 Hz value IJ1 peristaltic plate 5 (FIG. 1) corresponds to one displaced by two. On the other
hand, the digital signal 9a of the input terminal 13 is also supplied to the monostable
multivibrator 2o to obtain a pulse width d of a partial pulse width from the leading edge of the
digital signal 9? ? ?. The pulse signal d is supplied to the sample and hold circuit 21 to sample
and hold the output voltage of the adder 19. However, when the Q output C of the sample-andhold circuit 21 (K, D7 rib 70 circuit 15 is at low level, the voltage value of the voltage source 17
is stepped stepwise for each pulse of the pulse signal d of the monostable multivibrator 2o. The
hold voltage value is increased, and when the Q output C is at a high level, the hold voltage value
is decreased stepwise by the voltage value of the voltage source 18 for each pulse of pulse f4 ?
d, and the amplitude changes stepwise Generates a signal e. The absolute values of the voltages
of the voltage sources 17.18 are equal. The stepped signal e is supplied to the low pass filter 22
and the desired audio signal f is obtained from the output terminal 23. As described above, an
audio signal can be obtained, but in this embodiment, the response characteristic of the
diaphragm is extremely good, and the displacement of the diaphragm can be accurately detected.
The impression is significantly improved, and a speech signal with a wide same frequency band
without waveform distortion can be obtained.
Moreover, digital transmission is possible without the need for an additional circuit, and the
influence of the transmission system can be suppressed. As described above, according to the
present invention, since the displacement of the diaphragm can be detected with high accuracy
without providing any additional means in the diaphragm, the transient characteristic of the
diaphragm is improved and the acoustic wave is improved. And the sensitivity is significantly
improved to obtain an audio signal in a wide frequency band without waveform distortion, and
the signal generated by the detection of the displacement of the diaphragm is a digital signal, so
transmission of such a signal It is possible to suppress the influence of noise, loss and the like on
the occasion of the above, and to provide a microphone device with an excellent function which
the above prior art does not have.
[0002]
Brief description of the drawings
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[0003]
FIG. 3 (A) is a block diagram showing a concrete example of an optical system in a microphone
mounted Ti'ic ++ embodiment according to the present invention, and FIG. 3 (A) is an enlarged
view showing a part of FIG.
(H), (C), (+) fj The displacement of the diaphragm in FIG. 1 7) is an explanatory view showing the
mutual relation of the output 11 of each light detector, FIG. 1), (1)) a block diagram showing one
specific example of the tq control sub circuit of the digital signal shown in FIG. 5, (A), (B), (C), (+)),
l), (F) 4) is a signal waveform diagram showing a part of ?) bursting. ? и и и и и и и и и и и и и и и и и и и и и и и
и и и и и и и и и и и и и и и и и и и и и и и и и и и laser source, 3 и и и Half mirror 14 и и и и и 5 solid reflector, 5 и и и IN IN
movement, 7 и и и и Interference и 8a, и 8b и и и и и и Slit, 9 a, 9 b и и и и и и и и и и и и и и и и и и и и и и и и и и и и и и и и и и и
и и и и и и и и и и и и и и и и и и и и и и и и и и и и и и и и и и и и и и и и и и и и и и и и и и и и и и input terminal, 15 и и и J) Furinbu 70
Zuph "circuit, 16 ииииии changeover switch, 17 ░ 18 ...... voltage source, 19 ...... pressurized W unit,
20 ...... monostable multivibrator , 2 ..... Sample-hold circuit, 22 ..... Low-pass filter.
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