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BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a
digital microphone for extracting sound pressure as digital information.
2. Description of the Related Art Conventionally, as means for detecting sound pressure, a
moving coil method, a sound pressure-electrical resistance conversion method, etc. have been
generally employed. However, all of them are analog systems, and when a detected signal is to be
processed by a microprocessor, it has been necessary to convert by an A / D converter. In
particular, when a high speed response is required, the system becomes very complicated and
SUMMARY OF THE INVENTION The present invention overcomes the above-mentioned
drawbacks of the prior art and provides a digital microphone in which sound pressure is directly
taken out as digital information.
SUMMARY OF THE INVENTION In order to achieve the above object, light is irradiated to a film
which is distorted due to sound pressure, and the reflected light is digitally detected by a light
In this case, light receiving element groups are arranged in layers as a light detector, and the
light incident position is directly detected as a discrete value and extracted as an n-bit digital
According to the present invention, since the displacement of the film is detected using light,
contactless detection is performed, and thus the complete electrical insulation of the sound
pressure / displacement conversion unit and the inertia of the detection unit. It enables high
speed response by eliminating. In addition, since spot light can be used as light, the resolution is
Embodiments of the present invention will be described in detail with reference to the drawings.
First, the basic configuration of the present invention is shown in FIG. Reference numeral 1
denotes light emitting means, for example, a light source for emitting light with good parallelism
such as an LED or a laser diode. Reference numeral 2 denotes a film which is bent due to the
sound pressure 3 and which reflects the light emitted from the light emitting means 1. The
degree of deflection of this film 2 differs according to the strength of the sound pressure, so that
the light path after reflection of the light emitted to the film changes. A light detector is disposed
at a position where the reflected light is received. Reference numeral 4 denotes an encoder mask,
and a photodetector is disposed below the encoder mask. It is assumed that the reflected light
becomes a band-like light spreading along the slits of the encoder mask 4 and always enters one
of the slits. In the figure, the spread of the reflected light is shown extremely wide for easy
FIG. 2 shows an example of a light detector in which sensors are arranged in a plane. A plurality
of sensor groups D1, D2, D3 and D4 are arrayed in the optical sensor array 5, and each sensor
group is composed of sensors D11, D12,..., D21, D22,. And are connected to the data bus 6 in
groups. S0, S1, S2... In FIG. The encoder mask is used to shape the light beam waveform to
increase the resolution.
In the case of the configuration described above, the irradiation position of the reflected light is
determined by the deflection of the film 2 generated according to the sound pressure, and the
reflected light is received by one or more specific sensors The digital signal corresponding to the
sensor is taken out by this, and the deflection amount of the film 2 can be obtained as a
digitalized amount in real time.
FIG. 4 shows a light detector according to an embodiment of the present invention, in which the
sensor group in FIG. 2 is arranged in a plane, whereas in the present embodiment, the sensor
group is arranged in layers. It is.
Each sensor group D1 to D4 is formed separately for each layer and internally connected as
shown in FIG. 3, and the layers are separated. 0.About.9 indicate a light beam incident position,
and incident light is assumed to be transmitted through all the sensors immediately below it.
In the case of the present embodiment, the reflected light of the film 2 does not have to spread in
a band, but may be a spot. Then, the amount of deflection of the membrane 2 can be obtained as
a digital signal in real time, as in the configuration of FIG.
The sensor shown in FIGS. 2 and 4 can be easily formed using amorphous silicon or the like.
As described above, according to the present invention, since the sound pressure can be directly
taken out as digital information, the configuration as a system becomes very simple and the cost
becomes low.
In addition, since light is used for film deflection detection, the sound pressure / displacement
converter can be completely insulated electrically, which is extremely convenient when the
present invention is applied to medical devices and the like. . Furthermore, since non-contact
detection is performed, the inertia of the detection unit can be made extremely small, and as a
result, high-speed response can be achieved, and sensitivity can be enhanced. In particular, in the
case of the present invention in which the sensor groups are arranged in layers, very high
resolution can be obtained since light can be used as a spot.