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The present invention relates to a laser microphone that converts a change in the output of laser
light that is transmitted into an audio signal into an electrical signal to reproduce audio. The
conventional microphone vibrates the diaphragm with voice and converts this vibration into an
electrical signal, but in this system, microphone noise is likely to occur even when there is no
input voice, and a sound source It had many problems such as having to be installed in the
immediate vicinity of The present invention has been made in view of such circumstances, and it
is intended to convert sound into an electrical signal through the relay light without using the
diaphragm at all, and since the diaphragm is not used, noise is hardly generated. It is an object of
the present invention to provide a microphone that can obtain an electrical signal with high
fidelity. According to the present invention, a collection gain is added to a lade oscillator, and a
single frequency or single mode lade light is transmitted through the sound collector to air
having its density generated based on the sound propagating through the sound collector. It is
intended to convert the change of the laser output based on V into an electrical signal. In general,
it is said that laser oscillation light is excellent in monochromaticity, but since light emitted from
a normal laser oscillator oscillates in many longitudinal modes, several lines with different
frequencies are provided. However, the longitudinal mode interval [C / 2L (C is the speed of light,
L is the interval between the opposing mirrors) in terms of frequency] by shortening the laser
discharge tube and reducing the distance between the mirrors. It is possible to insert only one
longitudinal mode in the gain curve GC as shown in FIG. 3 given by the contour of the dogler by
increasing the value of D. That is, it is possible to oscillate a single frequency laser beam. Is also
referred to as single mode. Thus, in this state, if the distance between the mirrors is changed by
ΔL due to the cause of vibration of the mirror now, the emission line is nc / 2 (L ± ΔL from nC
/ 2L to the left and right This result very sensitively affects the laser output, and the laser output
can be captured as an electrical signal by the laser optical projector, which means that the
vibration of the mirror is an electric signal. It means being detected. The above principle is
applied when air density is generated in part of the optical path of the resonator. That is, the
density of air is replaced with the change of the refractive index for the laser beam passing
therethrough. Now, the change of the refractive index n by Δn is the same as the change of the
distance between the mirrors and the change of the optical path length by ΔL, and this is
because L is L ± (Δn−1) t (where t is Has the same meaning as that of the refractive index
varying by .DELTA.n (the length of the nine regions), and therefore it affects the swimming power
as in the case of the above-mentioned mirror deflection.
The present invention is made by utilizing the fact that the refractive index for laser light
changes according to the degree of air density in the sound collector based on voice, and if the
air is relatively dense, Δn becomes large. Also, if the air is relatively sparse, the refractive index
will be small. As a result, a variation in the laser output projected to the air is generated in
proportion to the density of air in the sound collector caused by the voice, and a variation in the
output corresponding to the detected electrical signal also occurs. It is intended to pick up this
and play a microphone effect. Hereinafter, the present invention will be described based on
examples with reference to the drawings. FIG. 1 is an explanatory view showing a relay
microphone according to the present invention. The laser resonator to which the present
invention is applied is formed by interposing a laser discharge tube 3 in which a lade-active
material such as He, Ne mixed gas is enclosed between opposing reflectors 1.29. The length of
the optical path between them is regulated so as to emit substantially single frequency lade light.
The laser light oscillates only at a frequency that is included in the dozer's width, so in the case of
He-Ne lade light, the dozer's width 1) W is about 1500 MHz, C / 2L (where C is the speed of light,
L is As described above, it is possible to oscillate laser light of a single frequency within the
above-mentioned donor width by increasing the energy to about "t-", that is, Li 10 cm. According
to the present invention, in the laser resonator configured as described above, a special sound
collector 4 is disposed between the reflecting mirror 1 ° 2 and the discharge tube 3 in an i4
series so as to be orthogonal to the laser optical axis A. The point being made is the time part.
The sound collector 4 is formed in a cylindrical body in which sound is propagated from the one
end 4a having a bulging portion to the other end 4b in the arrow direction, and an opposite hole
through which the laser light traveling all the way through the optical path is emitted. The parts
4e and 4d are drilled. FIG. 2 is a perspective view showing an example of another sound collector
4 formed by providing a lens in which the facing holes 4c and 4d are cut at the ends thereof at
the bree-ster angle. If this is the case, the density V of the air generated by the sound
propagating through the sound collector 4 occurs, which causes a change in the refractive index
of the air, and causes a change in the output of the laser light transmitted through the air. Is
detected by the light receiver 5 and output as an electric signal. The present invention is based
on the above configuration, attaches a sound collector that propagates voice to a lade oscillator,
picks up air density caused by voice with a change in refractive index for single mode laser light,
From the change of the output of the laser light which transmits the air, it is output as an electric
signal through the light receiver to perform the microphone function, and unlike the
conventional microphone, it is not used on the diaphragm so there is no noise. This is an
invention that is reproduced as high-fidelity voice and is extremely useful.
Brief description of the drawings
FIG. 1 is an explanatory view showing a laser microphone according to the present invention,
FIG. 2 is a perspective view showing an embodiment of a sound collector, and FIG. 3 is an
explanatory view showing a laser oscillation gain curve.
1.2 Reflector, 3 Reed-discharge tube, 4 Sound collector, 5 Light receiver. Patent applicant
Mochida Pharmaceutical Co., Ltd. Attorney Attorney Kai Masanori Kai Figure 2