JPS6132699A - Digital microphone - Google Patents

Abstract

PURPOSE:To achieve the high speed response obtained by attaining the complete electrical insulation of a sound pressure/displacement conversion part and eliminating the inertia at a detecting part, by irradiating light to a film which develops flexibility due to sound pressure and detecting digitally the reflected light by means of an optical detector. CONSTITUTION:A film 2 develops flexibility by a sound pressure 3, and reflects the light projected from a light projecting means 1. An optical detector is arranged at the bottom of an encoder mask 4, and the reflected light is assumed to be a band-like light for expanding along slits of the encoder mask 4, and to be made incident on any one of the slits. Plural sensor groups D1, D2, D3 and D4 are arrayed on an optical sensor array 5, and each sensor group consists of sensors D11, D12...D21, D22...D31... and D41 being connected internally, and further said groups are connected to a data bus 6 in the unit of the group. The irradiation position of the reflected light is decided by the flexibility of the film 2 developed in accordance with the sound pressure, and as single or plural specific sensors receive the reflected light, a digital signal can be taken out in correspondence to respective sensors.

Description

DETAILED DESCRIPTION OF THE INVENTION (Technical Field) The present invention relates to a digital microphone that extracts sound pressure as digital information.

(Prior Art) Conventionally, as means for detecting sound pressure, a moving coil method, a sound pressure-to-electrical resistance conversion method, or the like has generally been adopted. However, these are all analog systems, and if the detected signal is to be processed by a microprocessor, it must be converted by an A/D converter, and especially if high-speed response is required, the system However, it has the drawbacks of being extremely complex and expensive.

(Object of the Invention) The present invention eliminates the drawbacks of the prior art described above, and provides a digital microphone that directly extracts sound pressure as digital information.

(Structure of the Invention) In order to achieve the above object, light is irradiated onto a film that is deflected by sound pressure, and the reflected light is digitally detected by a photodetector. According to the present invention, since the displacement of the membrane is detected using light, the detection is non-contact, and therefore, the sound pressure/displacement conversion part is completely electrically isolated and the inertia of the detection part is eliminated, resulting in high-speed response. It is what makes it possible. Embodiments will be described in detail below with reference to the drawings.

(Embodiment) Fig. 1 is a diagram showing the basic configuration of an embodiment of the present invention, and 1 is a light emitting means, for example, an LED or a laser diode that emits light with good parallelism. It's so bright. Reference numeral 2 denotes a sheath film which is deflected by the sound pressure 3 and reflects the light emitted from the light emitting means 1. The degree of deflection of this membrane 2 depends on the strength of sound pressure.

are different, and therefore the optical path after reflection of the light irradiated onto the film changes. A photodetector is placed at a position to receive this reflected light. 4 is an encoder mask, under which a photodetector is arranged. The reflected light becomes a band-shaped light that spreads along the slits of the encoder mask 4, and is always incident on one of the slits (in the figure,
(The spread of reflected light is shown extremely wide for ease of understanding.)

FIG. 2 shows an embodiment of a photodetector, in which the photosensor array 5 includes a plurality of sensor groups Di 902 tD3.
．． D, are arranged, and each of the seven sensor groups has a sensor D.
□□, D12..., D21tD22..., D3□・
. In FIG. 2, S, , S□tSZ, . . . indicate slits of the encoder mask 4. In FIG. Note that the encoder mask is used to shape the beam waveform in order to increase the resolution.

Since the present embodiment is configured as described above, the irradiation position of the reflected light is determined by the deflection of the membrane 2 that occurs in response to the sound pressure, and the reflected light is received by one or more specific sensors. By doing so, a digital signal corresponding to that sensor is extracted, and the amount of deflection of the membrane 2 can be obtained as a digitized amount in real time.

FIG. 4 shows another embodiment of the photodetector.
In contrast to the sensor group shown in the figure, which is arranged in a planar manner, in this embodiment, the sensor group is arranged in layers. Each of the sensor groups D□ to D4 is formed in layers and interconnected as shown in FIG. 3, and the layers are separated. O-9 indicates the light beam incident position, and it is assumed that the incident light passes through all the sensors directly below it.

In the case of this embodiment, the reflected light from the film 2 does not need to spread out in a band shape, but may be a spot. Similarly to the embodiment shown in FIG. 2, the amount of deflection of the membrane 2 can be obtained as a real-time digital signal.

Note that the sensors shown in FIGS. 2 and 4 can be easily formed using amorphous silicon or the like.

(Effects of the Invention) As described above, according to the present invention, sound pressure can be directly extracted as digital information, so the system configuration is extremely simple and the cost is low. Furthermore, since light is used to detect membrane deflection, the sound pressure/displacement converter can be completely electrically isolated, which is extremely convenient when applying the present invention to medical equipment, etc. . Furthermore, since it is non-contact detection, the inertia of the detection section can be made very small, and as a result, high-speed response is possible and sensitivity can be increased.

[Brief explanation of the drawing]

FIG. 1 is a basic configuration diagram of an embodiment of the present invention, FIG. 2 is a perspective view of an embodiment of a photodetector, and FIG. 3 is a diagram showing internal connections of the photodetector. FIG. 4 is a sectional view showing another embodiment of the photodetector. DESCRIPTION OF SYMBOLS 1...Light emission means, 2...Membrane, 3...Sound pressure,
4... Encoder mask, 5... Optical sensor array, 6... Data bus, D-D4...
Sensor group. Patent applicant: Tohoku Ricoh Co., Ltd. Figure 1 Figure 2 Figure 3 Figure 4

Claims (3)

[Claims] (1) Consisting of a light emitting means, a film that is deflected by sound pressure and reflects the light emitted from the light emitting means, and a photodetector that digitally detects the light reflected by the film. A digital microphone characterized by: (2) The photodetector has a group of light receiving elements arranged in a plane,
The digital microphone according to claim 1, wherein the light incident position is directly detected as a discrete value and extracted as an n-bit digital signal. (3) The photodetector has a group of light-receiving elements arranged in layers, and the light incident position is directly detected as a discrete value and extracted as an n-bit digital signal. Digital microphone as described.