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JP2007036690

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DESCRIPTION JP2007036690
The present invention provides a microphone device capable of accurately acquiring an audio
signal using an electromagnetic wave of high frequency such as light while excluding influences
other than the shape of a microphone. A microphone device (1) includes a pair of
electromagnetic wave detectors (2a, 2b) provided opposite to a generator that generates an
electromagnetic wave of high frequency such as light, and conversion means. The conversion
means generates, in each of the electromagnetic wave detectors 2a and 2b, the density difference
(n-Δn and n, n and n + Δn, etc.) of the gas existing between the generation source and the pair
of electromagnetic wave detectors 2a and 2b. The difference between the detected amounts of
electromagnetic waves received via the gas is converted to a 1-bit digital audio signal and output.
[Selected figure] Figure 1
Microphone device, voice recording device, and voice recording and reproducing device
[0001]
The present invention relates to a microphone device, a voice recording device, and a voice
recording and reproducing device, and more particularly, a microphone device for obtaining a
voice signal using an electromagnetic wave of high frequency such as light, and a voice provided
with the microphone device. The present invention relates to a recording device and an audio
recording and reproducing device.
[0002]
When sound travels through the air, it becomes a wave according to the size and height of the
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sound.
This wave is referred to as a compressional wave because it travels as a dense and thin air. A
voice input device (acoustic machine) that converts this wave into an electrical signal is called
this microphone device.
[0003]
FIG. 6 is a schematic view for explaining the principle of a conventional diaphragm-type
microphone device. The microphone device 50 first receives the pressure wave of air by the
diaphragm 51. The diaphragm 51 is supported by the damper 52 to constitute an
electromechanical vibration system. There are a magnet-coil method, a method of detecting an
electric capacity between the diaphragms, and the like to detect the displacement amount of the
diaphragm. It is common to generate an electrical signal by amplifying the voltage by an
amplifier 53.
[0004]
As a microphone device, a super-directional microphone device that is compact and has a sharp
directivity over the entire band is also disclosed for picking up natural sound with emphasis on
sound quality (see, for example, Patent Document 1). . In the superdirective microphone device
described in Patent Document 1, three unidirectional microphone cells are disposed at
predetermined intervals in the front-rear direction, and differential signals extracted from output
signals of the two microphone cells, and the like. The differential signal extracted from the output
signals of the two microphone cells and the differential signal between the two differential
signals are calculated, and a frequency signal higher than a predetermined frequency is extracted
by a high pass filter. Also, from the difference signal extracted from the output signals of the
other two microphone cells, a frequency signal lower than the frequency is extracted by a low
pass filter. The phases near the band boundaries of the output signals of these two filters are
matched to obtain an output signal corrected by the equalizer circuit.
[0005]
However, in the conventional diaphragm method described in FIG. 6 including the microphone
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device of Patent Document 1, the diaphragm 51 / damper 52 becomes a resistance of the audio
signal, and the characteristics of the diaphragm 51 / damper 52 depend on the material etc.
There is a problem that the conversion characteristics vary. Furthermore, in this diaphragm
method, there is a limitation in appealing wide band / wide dynamic range also in characteristics.
[0006]
FIG. 7 is a diagram for explaining the current sound environment. The sound pressure around us
is shown in FIG. 7, but in the case of a sound environment like this, the reference sound pressure
P0 is defined by 2 × 10 <-5> N / m <2>, and is exemplified here. However, it is necessary to
measure a sound with a sound pressure level of 0 dB (sound pressure P0) to 140 dB (sound
pressure 20 N / m <2>). Furthermore, if it is intended to represent all sounds not included in FIG.
7, it is necessary to measure sounds with sound pressure levels of 0 dB or less and 140 dB or
more, and for this reason the conventional diaphragm method can not cope.
[0007]
FIG. 8 is a diagram for explaining an instrument or the like having a frequency band exceeding
the audible band. In the frequency component, as exemplified by the turkey bell in FIG. 8 (A), the
tambourine in FIG. 8 (B), the wind bell in FIG. 8 (C), and the bell in FIG. 8 (D) It can be seen that
there are instruments etc that exceed. Specifically, the acoustic signal component is very wide at
0 to 1 MHz. In the past, air was received by the diaphragm and its displacement was detected,
but it was sufficient to detect the audible band (~ 20 kHz), but to detect lower sound pressure and
broadband signal components The diaphragm method was the limit.
[0008]
On the other hand, in recent years, experimental studies of microphones and pressure sensors
utilizing light reflection have begun to be conducted (see, for example, Non-Patent Document 1).
FIG. 9 is a schematic view for explaining a conventional (non-patent document 1) microphone
device using light reflection. In the method adopted in this device, the sensor portion S is
provided on part of the side surface of a cylindrical glass with a radius of curvature R, and light
at the interface B between glass (refractive index n0) and air (refractive index nm) It uses total
reflection. In the sensor unit S, as shown in FIG. 9, when a collimated light beam of radius r is
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made incident on the boundary surface B such that the center thereof is on the total reflection
boundary line h, the light above h is reflected, The lower light is transmitted. Here, when the
refractive index of air changes due to pressure change, the position of the boundary changes, and
as a result, the amount of reflected light changes, the pressure change is detected by detecting
the change in the amount of reflected light as an analog value by the photodiode circuit. It is an
attempt to measure sound pressure.
[0009]
An apparatus for converting an input signal into a 1-bit digital signal according to a digital sigma
modulation 1-bit coding method applicable to an analog audio input signal has also been
proposed (for example, Patent Document 2-4) See). Japanese Patent Laid-Open No. 2004173053 Japanese Patent Laid-Open No. 10-178346 Japanese Patent Laid-open No. 2000332553 Japanese Patent Laid-Open No. 2004-363771 Atsushi Suzuki, Kenichi Kido,
"Experimental examination of microphone and pressure sensor using light reflection Proceedings
of the Acoustical Society of Japan, March 2005, p. 495
[0010]
As described above, in the conventional diaphragm-type microphone device, it is impossible not
only to vary the conversion characteristics but also to be configured to have a wide band / wide
dynamic range. In fact, the characteristics of the microphone device are determined by the
microphone shape, the frequency characteristics of the diaphragm and the damper, the
characteristics of the amplifier, and the characteristics of the AD converter. Here, the diaphragm
/ damper depends on the selection of weight / material, the amplifier depends on the
performance of the analog amplifier, and the type of AD converter depends on the type, but
aiming for wider band / wide dynamic range Become high.
[0011]
For example, even when a device as described in Patent Literature 2-4 is selected and an analog
voice input signal input by the above-described conventional microphone device is AD converted
into a 1-bit digital signal, it is natural that the microphone The device acquires an audio signal in
an analog manner by the diaphragm, which not only limits the quality of the input audio signal
but also increases the cost of the AD converter itself.
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[0012]
Also, the conventional microphone method using light including non-patent document 1 aims at
detection utilizing the linearity of an analog signal, and in the end, a sensor comprising a
photodiode circuit etc. has an extremely high sound pressure detection sensitivity. It can not be
accurately configured from various factors such as the need for amplification because of its small
size, the influence of vibration, and the problem of light scattering.
In fact, Non-Patent Document 1 has not reached the point of showing the result of signal
detection. As described above, in the light-based microphone system according to the prior art,
there is a problem in how to pick up physically.
[0013]
The present invention has been made in view of the above-described circumstances, and is a
microphone device capable of accurately acquiring an audio signal using an electromagnetic
wave of high frequency such as light while excluding influences other than the microphone
shape. An audio recording device comprising the microphone device capable of recording an
audio signal without deterioration; an audio recording / reproducing device equipped with the
audio recording device capable of acquiring and outputting an audio signal without deterioration
Its purpose is to provide.
[0014]
The present invention is configured by the following respective technical means in order to solve
the problems as described above.
[0015]
A first technical means is a microphone device for extracting an audio signal by using an
electromagnetic wave of high frequency, which comprises a pair of electromagnetic wave
detectors provided relative to the source of the electromagnetic wave, the source and the pair
The difference in density of the gas existing between the electromagnetic wave detector and each
electromagnetic wave detector is calculated as the difference of the detection amount of the
electromagnetic wave received from the generator via the gas to obtain a 1-bit digital audio
signal. And converting means for converting and outputting.
[0016]
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A second technical means is characterized in that, in the first technical means, an electromagnetic
wave generator for generating the electromagnetic wave is provided.
[0017]
A third technical means is characterized in that, in the first or second technical means, the pair of
electromagnetic wave detectors are arranged at positions where their respective detection
portions are continuously adjacent to each other.
[0018]
In a fourth technical means according to any one of the first to third technical means, the
conversion means is configured to calculate a difference in density of the gas existing between
the generator and the pair of electromagnetic wave detectors In the detector, the difference
means for obtaining the difference of the detection amount of the electromagnetic wave received
from the generation source through the gas, and the difference obtained by the difference means
is threshold-processed with a predetermined threshold to obtain a 1-bit digital signal sequence. It
has a threshold processing means for outputting, and is characterized in that the 1-bit digital
signal sequence is outputted as the digital audio signal.
[0019]
A fifth technical means is the fourth technical means, wherein the threshold processing means
reshapes the threshold-processed analog signal with a generation frequency of the
electromagnetic wave of the generation source or a frequency equivalent to the generation
frequency. A 1-bit digital signal sequence is output as the digital audio signal.
[0020]
A sixth technical means according to any one of the first to fifth technical means further
comprises a filter for converting the 1-bit digital audio signal outputted by the converting means
into a multi-bit digital signal. It is
[0021]
A seventh technical means is characterized in that, in any one of the first to sixth technical
means, the electromagnetic wave is light.
[0022]
An eighth technical means according to the seventh technical means, a signal generator for
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generating a pulse signal of the high frequency as a generation source of the electromagnetic
wave, and a laser based on the pulse signal generated by the signal generator. And an optical
pulse signal generator for generating light.
[0023]
A ninth technical means is the microphone device according to any one of the first to eighth
technical means, and the 1-bit digital audio signal outputted by the conversion means, the
generation frequency of the electromagnetic wave of the generation source or the generation
frequency And a 1-bit recording means for driving and recording the same frequency.
[0024]
A tenth technical means is the voice recording device according to the ninth technical means, and
a 1-bit digital voice signal recorded by the voice recording device, a generation frequency of the
electromagnetic wave of the generation source or a frequency equivalent to the generation
frequency. And an audio output means for driving and outputting a 1-bit digital audio signal.
[0025]
According to the microphone device according to the present invention, it is possible to
accurately obtain an audio signal using an electromagnetic wave having a high frequency such as
light while excluding influences other than the microphone shape.
Further, according to the audio recording apparatus of the present invention, it is possible to
provide the microphone device and to record an audio signal without deterioration.
Furthermore, according to the audio recording and reproducing apparatus according to the
present invention, it is possible to provide the audio recording apparatus and obtain and output
an audio signal without deterioration.
[0026]
FIG. 1 is a view showing an example of the configuration of a microphone device according to an
embodiment of the present invention, and FIG. 2 is a view for schematically explaining the
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change of the refractive index of gas as a medium which changes depending on the density of
voice. It is.
In FIG. 1, 1 is a microphone device, and 2a and 2b are a pair of photodetectors.
[0027]
Hereinafter, although the present invention will be described only with respect to an example in
which light is generated and light is received by the light detectors 2a and 2b, which is a more
preferable embodiment, the present invention generates an electromagnetic wave having a
higher frequency than a sound wave. It is applicable even if it is a form provided with a pair of
electromagnetic wave detectors which detect electromagnetic waves generated from it to an
origin (for example, electromagnetic wave generator).
Light is preferable as the electromagnetic wave used in the present invention because light is the
most easily bent with respect to the density change of air.
Among light, light of higher frequency is preferable in view of resolution, and in view of detection
accuracy, it is preferable to be monochromatic laser light.
When electromagnetic waves other than light are used, electromagnetic wave detectors such as a
pair of electric converters may be employed instead of the pair of light detectors 2a and 2b.
[0028]
The microphone device 1 includes a pair of photodetectors 2a and 2b provided opposite to a
generator that generates light (hereinafter, described as laser light L), and the following
conversion means.
This conversion means generates the density difference (n-.DELTA.n and n, n and n + .DELTA.n,
etc.) of the gas existing between the source and the pair of photodetectors 2a and 2b in each of
the photodetectors 2a and 2b. By converting the detection amount of the light received from the
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original through the gas (gas having density by sound waves), it is converted into a 1-bit digital
audio signal and output.
[0029]
The principle that enables such digital audio signal acquisition will be described with reference to
FIG.
In FIG. 2, as the gas, in view of the usage form of the normal microphone device 1, normal air
corresponds, but it is not necessary to be air, and even if it is another gas, it is possible to cause
the density by voice Just do it.
[0030]
First, a pair of photodetectors (also referred to as two-divided photodetectors) 2a and 2b are
disposed in opposition to the laser light L generated from the generation source by pulse driving.
The voice to be measured A is allowed to pass through the gas in the meantime.
The measured voice A vibrates at a predetermined frequency, and a density difference occurs.
As a result, a difference in refractive index occurs, and the traveling direction of light is changed.
This is the basic principle.
[0031]
As shown in FIG. 2, air A as a medium changes its refractive index to n-.DELTA.n, n, n + .DELTA.n
with respect to time T-.DELTA.t, T, T + .DELTA.t by voice A propagating air as a compressional
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wave. . As shown in FIG. 1, the center of gravity of the laser light L shifts to the lower part (the
light receiving portion side of the light detector 2b) having a large refractive index, for example,
by the refractive index of the air to be irradiated, and it becomes refracted light L '. As a result,
the amount of light received by the light detector 2b (output is the A2 signal) is larger than the
amount of light received by the upper portion (on the light receiving portion side of the light
detector 2a) having a small refractive index (output is the A1 signal). The light has a Gaussian
distribution, and its center is shifted. For example, when a wave having a refractive index n
comes to the optical path of the laser light L, the wave bends downward in FIG. 1 when a wave
having a refractive index n + Δn comes to the optical path of the laser light L. As described
above, the laser light L is relatively upward or downward with respect to the average value due to
the density difference. Then, the difference between those signal components A1 and A2 is taken
out as a 1-bit digital signal.
[0032]
As described above, in the detection method according to the present invention, instead of the
idea of taking out with the linearity of analog as in the prior art, it is made to take out directly as
a digital signal. Therefore, according to the microphone device according to the present
invention, the influence of the diaphragm / damper is eliminated, the amplifier circuit may be
simple, influences other than the microphone shape are excluded, and light with high frequency
such as light is used with high accuracy. It is possible to obtain digital audio signals. For example,
according to the present invention, the influence of the diaphragm and the damper is eliminated,
and the measured sound A may have a wide sound pressure range (140 dB or more) and a wide
band (0 to 1 MHz, in principle 1 GHz or more). ) Can be measured, and furthermore, it becomes
possible to design a microphone device with less variation.
[0033]
Moreover, it is preferable that a pair of light detectors 2a and 2b are arrange | positioned in the
position where each detection part adjoins continuously. For example, if the photodetector 2a
and the photodetector 2b are detectors consisting of the same number of photosensors, the
distance between the photosensors at their boundaries is preferably the photodetector 2a (and
the photodetector 2b). It is good to arrange the same as the interval of the photo sensor in).
[0034]
FIG. 3 is a diagram showing an example of the circuit configuration of the microphone device of
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FIG. 1, in which 10 is a microphone device as an example of the microphone device 1, 11 is a
high-speed signal generator as an example of a signal generator, 12 is Laser diode as an example
of an optical pulse signal generator, 13 is a two-split light receiver as an example of light
detectors 2a and 2b, 14a and 14b are amplifiers (amplifiers), 15a and 15b are switches, 16a and
16b are capacitors, Reference numeral 17 is a difference calculation processing circuit, reference
numeral 18 is a reshape processing circuit, and reference numeral 19 is a decimation filter.
[0035]
The conversion means described above preferably includes a light generator, difference means,
and threshold processing means, and preferably outputs a 1-bit digital signal sequence as a
digital audio signal.
The light generator includes a high-speed signal generator 11 that generates high-speed pulses
such as 10 MHz, and a laser diode 12 that is driven by the pulses generated by the high-speed
signal generator 11 and generates laser light L according to the pulses. Etc.
[0036]
The frequency of the high speed signal generator 11 corresponds to the signal density of the
audio signal. Therefore, in order to realize the microphone device 10 (provided with a 1-bit AD
converter as described later) according to the present invention, it is preferable that the sampling
be as high as possible. Here, since the reproduction medium SACD is realized at 2.8 MHz and at
10 MHz for the 1-bit digital amplifier, it is preferable that the sampling frequency be, for
example, at least 10 MHz in the coding system.
[0037]
The difference means determines the difference in the detection amount of light received from
the light generator at each light receiving portion, with the difference in density of the gas
existing between the two split light receivers (a pair of light detectors 2a and 2b) This is a means,
and is exemplified by the sample hold unit exemplified by the switches 15a and 15b and the
capacitors 16a and 16b and the difference calculation processing circuit 17.
[0038]
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The difference calculation processing circuit 17 causes a delay in time by this sample and hold
unit, and takes a difference with respect to the input of the A1 signal and the A2 signal.
This delay is generated by alternately switching the switches 15a and 15b by the signal
generated by the high-speed signal generator 11. Further, the charge stored in each of the
capacitors 16a and 16b during the on period is input to the difference calculation processing
circuit 17 by this switching, and the difference between them is output from the difference
calculation processing circuit 17 as an analog signal. It can be said that sampling is performed by
the capacitors 16a and 16b. With respect to the signals A1 and A2, charges corresponding to the
total amount of light received during the generation cycle of the high-speed signal generator 11
are stored in the capacitors 16a and 16b, respectively, and are output to the difference
calculation processing circuit 17. . Further, in the example of FIG. 3, the signals are amplified
through the amplifiers 14a and 14b, respectively, so as to be able to cope with cases where the
signals A1 and A2 of the light reception amounts received by the respective light receiving
portions are weak.
[0039]
The threshold processing means is a means for performing threshold processing on the
difference obtained by the difference means with a predetermined threshold and outputting a 1bit digital signal sequence, and the analog signal output from the difference calculation
processing circuit 17 is The reshaping processing circuit 18 exemplifies a 1-bit digital signal
train as a digital audio signal by performing resizing at the generation frequency of the highspeed signal generator 11 or a frequency equivalent to that (which needs to be synchronized).
The threshold processing means is considered to include not only the reshape processing circuit
18 but also one function of the above-mentioned sample hold unit.
[0040]
With the above-described configuration, in the microphone device 10, the sound pressure is
directly measured by the compression wave without using the diaphragm. The microphone
device 10 pulse-drives the laser by a signal generated by the high-speed pulse signal generator
11 (10 MHz), and a portion between the two-divided light receiver 13 disposed relative to it and
the generation source of the laser light L is The measurement air passes, the refractive index
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12
changes due to the density difference, the traveling direction of light is bent, and according to it,
the two split light reception of the light receiving unit 13 generates an optical signal (A1 signal
and A2 signal) obtained by the bending direction. . Further, the microphone device 10 amplifies
the generated optical signals by the amplifiers 14a and 14b, and the sample and hold circuit
samples and holds those sample and hold signals at the frequency generated by the high-speed
signal generator 11 as a difference operation processing circuit The difference calculation
process is performed at 17.
[0041]
The reshape processing circuit 18 performs waveform shaping processing with the first highspeed pulse signal, and outputs a 1-bit digital signal sequence. The reshape processing circuit 18
uses the high-speed pulse signal (10 MHz in this case) of the high-speed signal generator 11 to
convert the analog signal output from the difference calculation processing circuit 17 to “1”
when A1> A2, and A1 <A2. The waveform shaping process is performed to "0" and so on. In the
example of FIG. 1, the A2 signal is the moment when the signal component is larger, and "0" is
output. The digital signal sequence generated and output here is a high-speed 1-bit stream signal,
and has a speed based on the frequency generated by the high-speed signal generator 11.
[0042]
As described above, according to the method of the present invention, the above-mentioned
streaming stream is 1 bit at high speed by the light receiver 13, the amplifiers 14a and 14b, the
switches 15a and 15b, the capacitors 16a and 16b, the difference calculation processing circuit
17, and the reshape processing circuit 18. It can also be said that it constitutes a 1-bit AD
converter serving as an AD converter signal. Therefore, the microphone device 10 according to
the present invention has two features of light detection and conversion with an AD converter,
and the AD converter is a 1-bit AD converter. Thus, the present invention incorporates 1-bit
technology into the system, resulting in higher performance. The microphone device 10
according to the present invention can be said to be a microphone device incorporating a 1-bit
AD converter driven by a high-speed light pulse signal without using a diaphragm, or a 1-bit AD
digital microphone.
[0043]
Further, in the microphone device 10, since the delay only has a period of the high-speed signal
generator 11, for example, only 10 M bits when sampled at 10 MHz, it is not only a signal close
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to analog in quality but also a digital signal. Therefore, when passing through a line, even when
recording or reproducing, no deterioration occurs as with an analog signal.
[0044]
In addition, it is necessary to be able to cope with the case of a device which can not be
processed by the signal as it is until a recording device or a reproducing device of a 1-bit digital
signal as described later is generally used.
Therefore, the microphone device 10 preferably includes a decimation filter 19. The decimation
filter 19 is a filter (also referred to as a coding filter) for converting the 1-bit digital audio signal
(the signal output from the reshape processing circuit 18 in FIG. 3) output from the abovementioned conversion means into a multibit digital signal. The filter may be a filter that performs
thinning processing or a filter that performs smoothing, and the form thereof is not limited.
[0045]
Further, as described above, the light generator is not essential as the microphone device 1 and
may be connected to an external light generator, but at least it needs to be fixed to the light
detectors 2a and 2b. . In the present specification, the shape of the microphone (the shape of the
portion receiving the sound) is not limited, but the shape of the microphone covers the portion to
be irradiated with the laser light L so that no sound enters and the sound passing portion It is
good to separate from other parts well.
[0046]
FIG. 4 is a diagram showing an example of a circuit configuration of an audio recording
apparatus according to another embodiment of the present invention. In the figure, 20 is a
recording medium drive as an example of 1 bit recording means, and 30 is a recording disk.
Here, the same code | symbol is attached | subjected to the same component as FIG. 3, and the
description including the application is abbreviate | omitted.
[0047]
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The audio recording apparatus according to the present invention comprises the microphone
device 10 as described above, wherein the 1-bit digital audio signal output by the conversion
means is the light generation frequency (or frequency equivalent to the generation frequency in
the light generator; And 1 bit recording means for driving and recording according to the
necessity of synchronization).
[0048]
FIG. 4 shows an example in which the recording medium drive device 20 (and the recording disc
30 to be recorded thereon) is provided as an example of the 1-bit recording means.
The recording medium drive device 20 uses the generation frequency of the high-speed signal
generator 11 as a drive clock, or uses a similar frequency although synchronization is necessary.
As the recording disc 30, various disc media such as a DVD, a CD, a Blu-ray disc, etc. may be
mentioned, but media of other shapes may be used. The present invention is also applicable to
the case where the recording medium drive device 20 is a hard disk drive (HDD) and its
controller instead of the recording disk 30, and the recording medium is HD.
[0049]
Further, according to the audio recording apparatus of the present invention, the abovedescribed microphone device is provided, and the 1-bit digital signal is recorded as it is, so that
the audio signal can be recorded without deterioration. Further, this voice recording apparatus is
applicable even in the form provided with the decimation filter 19, but the signal after passing
the filter becomes a multi-bit signal.
[0050]
FIG. 5 is a diagram showing an example of a circuit configuration of an audio recording and
reproducing apparatus according to another embodiment of the present invention, in which 21 is
a recording medium drive apparatus as an example of 1 bit recording means and audio output
means An amplifier, 23 is a low pass filter (LPF), and 24 is a speaker. Here, the same code |
symbol is attached | subjected to the same component as FIG.3 and FIG.4, and the description
including the application is abbreviate | omitted.
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[0051]
The audio recording / reproducing apparatus according to the present invention comprises the
audio recording apparatus as described in FIG. 4, and generates the 1 bit digital audio signal
recorded by the audio recording apparatus as the light generation frequency (or generation
frequency) in the light generator. It comprises an audio output means which is driven and read
out with an equivalent frequency (but needs synchronization) to output a 1-bit digital audio
signal.
[0052]
FIG. 5 shows an example provided with a recording medium drive device 21 (and a recording
disk 30 to be recorded / read out thereof) as an example of the 1-bit recording means / audio
output means.
In the recording medium drive device 21, a recording unit is illustrated as a 1-bit recording unit,
and a reproduction unit is illustrated as an audio output unit. The recording medium drive device
21 uses the generated frequency of the high-speed signal generator 11 as a drive clock, or uses a
similar frequency although synchronization is necessary. The recording disk 30 is also the same
as that described with reference to FIG. 4 and is also applicable to the case where the recording
medium is HD.
[0053]
Furthermore, in the example of FIG. 5, the 1-bit digital signal output from the reproduction unit
in the recording medium drive device 21 is amplified by the amplifier 22, passes through the LPF
23, is converted to an analog signal, and is reproduced as sound by the speaker 24. .
[0054]
As described above, according to the audio recording and reproducing apparatus according to
the present invention, the above-described audio recording apparatus can be provided, and an
audio signal can be obtained and recorded without deterioration, and the audio signal can be
output.
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Further, this audio recording and reproducing apparatus is applicable even in the form provided
with the decimation filter 19, but the signal after passing through the filter becomes a multi-bit
signal. As described above, by constructing an integrated system that performs sampling of
recordings from the microphone device and reproduction at the same sampling frequency, digital
storage can be performed in the best condition from input to output. Here, for example, if the
reproduction system is 20 MHz, it is preferable to make the generators equivalent as well, such
as 20 MHz.
[0055]
It is a figure which shows one structural example of the microphone apparatus which concerns
on one Embodiment of this invention. It is a figure for demonstrating roughly the change of the
refractive index of the gas as a medium which changes with the density of audio | voice. It is a
figure which shows an example of a circuit structure of the microphone apparatus of FIG. It is a
figure which shows the example of a circuit structure of the audio recording device which
concerns on other embodiment of this invention. It is a figure which shows the example of a
circuit structure of the audio recording and reproducing apparatus based on other embodiment
of this invention. It is the schematic for demonstrating the principle of the microphone apparatus
of the conventional diaphragm system. It is a figure for demonstrating the present sound
environment. It is a figure for demonstrating the musical instrument etc. which have a frequency
band exceeding an audible zone. It is a schematic diagram for demonstrating the microphone
apparatus using light reflection of the past (nonpatent literature 1).
Explanation of sign
[0056]
DESCRIPTION OF SYMBOLS 1, 10 ... Microphone apparatus, 2a, 2b ... Photodetector, 11 ... Highspeed signal generator, 12 ... Laser diode, 13 ... 2 division | segmentation light receiver, 14a, 14b,
22 ... Amplifier (amplifier), 15a, 15b ... Switch , 16a, 16b: capacitor, 17: difference operation
processing circuit, 18: reshape processing circuit, 19: decimation filter, 20, 21: recording
medium drive, 23: low pass filter (LPF), 24: speaker, 30: recording disk .
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