JPS63260396A - Microphone - Google Patents

Abstract

PURPOSE:To simplify circuit constitution by replacing a displacement in forward/ backward direction of a diaphragm vibrated by a sound wave into a change in the distance from a light source to the diaphragm, detecting the change of a photodetection area in the photodetection section by the number of photodetections of plural photodetectors and outputting the vibration of the diaphragm by the input sound wave as a digital electric signal. CONSTITUTION:The diaphragm 11c is vibrated by a sound wave S. The diameter of the radiation circle 11c shown in solid line concentric circles being the absorption and transmission part 11a of the diaphragm 11 is changed as shown in concentric circles in broken lines at the inside and outside of the radiation circle 11c. Since the distance between the diaphragm 11 and the photodetection section 13 is unchanged, the diameter of the reflected light photodetection circle 13a of the photodetection section 13 is changed by the same size as the change in the diameter of the circle 11c. When the diaphragm 11 approaches the light source 12, the reflected light photodetection circle 13a is smaller and when the diaphragm 11 is parted, the diameter is larger. Thus, displacement of the diaphragm 11 is replaced into the change in the photodetection area of the photodetection section 13, the result is converted into a digital electric signal by counting number of photodetections of the plural photodetectors such as CCD.

Description

DETAILED DESCRIPTION OF THE INVENTION (Field of Industrial Application) The present invention relates to a microphone used in audio equipment, and more specifically, to a microphone that directly converts sound waves such as music into digital electrical signals. be.

(Prior Art) A conventional method for inputting sound waves such as music as digital electrical signals to a digital audio device will be explained with reference to FIG.

FIG. 3 is a block diagram of a signal processing circuit that converts an analog electrical signal of a microphone into a digital electrical signal.

In the figure, a sound wave S is converted into a minute analog electrical signal by a microphone 1 into which it is input, and is amplified to a level that can be transmitted by a microphone amplifier 2, and then a transmission line 3.
The signal is then input to a digital audio device 4 indicated by a broken line frame in the figure.

The analog electrical signal input to the digital audio device 4 is amplified by an amplifier 5 to a level that can be sampled, and then a low-pass filter 6 removes unnecessary harmonic components to prevent aliasing distortion due to the alias effect during sampling. is removed. The analog electrical signal from which unnecessary harmonic components have been removed is sampled and held in the sample-and-hold amplifier 8 by the sample-and-hold control signal C output from the clock generator 7, and then output from the clock generator 7. The analog/digital converter 9 outputs a digital electrical signal E in response to the conversion start signal.

(Problems to be Solved by the Invention) However, the above configuration has the problem that the analog-to-digital converter 9 is expensive and it is difficult to obtain one with stable performance. Furthermore, since the output of the microphone passes through the transmission line 3 in the form of an analog signal, there are problems in that noise is likely to be mixed in, and distortion is likely to occur due to repeated amplification.

The present invention solves the above-mentioned problems and provides a microphone that can convert sound waves of music etc. into digital electrical signals and directly supply them to digital audio equipment without requiring a complicated signal processing circuit. It is.

(Means for Solving the Problems) In order to solve the above problems, one aspect of the present invention is to arrange a light source having an irradiation angle so as to be perpendicular to the optical axis. A diaphragm that has a part in the center that absorbs or transmits light and a part that reflects light around it, and a plurality of parts that are connected to the diaphragm and receive reflected light from the diaphragm and convert it into an electrical signal. The microphone is composed of a light-receiving section consisting of a light-receiving element,
The longitudinal displacement of the diaphragm caused by the sound wave is replaced by a change in the distance from the light source to the diaphragm, and the resulting change in the light-receiving area of the light-receiving section is detected by the number of light-receiving elements of the plurality of light-receiving elements.
The vibration plate is configured to output the vibration of the diaphragm caused by the input sound wave as a digital electrical signal.

(Function) With the above configuration, for example, by using a light source with an irradiation angle of 2α, the diaphragm is moved by ±ΔX in the front and rear directions by sound waves.
If the distance from the fixed light source to the vibration is changed by ±ΔX, the irradiation circle on the diaphragm changes by ±2Δx tanα. That is, if the diaphragm moves away from the light source by ΔX, the diameter of the irradiation circle increases by 2Δx tanα, and conversely, if it approaches by ΔX, it decreases by 2Δx tanα. Since the diaphragm and the light receiving section are connected, the distance between them does not change, so the diameter of the reflected light receiving section of the light receiving section is.

It will change by ±2Δx tanα.

Therefore, since the vibration of the diaphragm is expressed as a change in the diameter of the reflected light receiving circle of the light receiving section, it can be converted into a digital electrical signal by counting the number of lights received by the light receiving element.

(Example) An example of the present invention will be described with reference to FIGS. 1 and 2. Figures 1 (a), (b) and (C) are respectively.

A side sectional view of a microphone according to the present invention, and its A
They are a rear sectional view and a front sectional view taken along the A' plane and the BB' plane, respectively, and viewed from the direction of the arrow.

In FIG. 1(a), the microphone according to the present invention is
A circular part 11a is provided inside the cylindrical case 10 so as to be perpendicular to its center line, and as shown in FIG. A diaphragm 11 consisting of a portion 11b, a light source 12 whose optical axis coincides with the center line and has an irradiation angle of 2α, and a light source 12 connected to the diaphragm 11 and placed behind the light source 12. . It is composed of a light receiving section 13 formed by a plurality of light receiving elements such as a CCD.

Note that the absorbing or transmitting portion 1 formed at the center of the diaphragm 11
1a is set so that reflected light does not return to the light source 12.

The operation of the microphone configured in this way will be explained. When the diaphragm 11 vibrates due to the sound wave S and is displaced back and forth, the diaphragm 11 vibrates as shown by the broken line in FIG. 1(a).
1 and the light receiving section 13 connected thereto are simultaneously displaced back and forth. Since the distance from the diaphragm 11 to the light receiving section 13 does not change, the change in the distance from the light source 12 to the diaphragm 11 caused by the displacement of the diaphragm 11 changes the distance from the light source 12 to the light receiving section 13 via the diaphragm 11. This will result in a change in

That is, in FIG. 1(b), the irradiation circle 11 shown by the solid line concentric circle with the absorption or transmission portion 11a of the diaphragm 11
c is the above irradiation circle lie due to the displacement of the diaphragm 11.
The diameter of the irradiation circle changes as shown by concentric circles inside and outside the dotted lines. Since the distance between the diaphragm 11 and the light receiving section 13 does not change, the diameter of the reflected light receiving opening 13a of the light receiving section 13 is the same as that of the diaphragm 1.
The dimension changes by the same amount as the amount of change in the diameter of the irradiation circle 11c of No. 1. When the diaphragm 11 approaches the light source 12, the reflected light receiving port 1
3a becomes smaller and becomes larger as you move away from it. Therefore, the displacement of the diaphragm 11 can be replaced by a change in the light-receiving area of the light-receiving section 13 by counting the number of light-receiving elements such as CODs.

It can be converted into a digital electrical signal.

FIG. 2 is a block diagram for inputting music signals from the microphone of the present invention to digital audio equipment.

In the figure, a sound wave S is converted into a digital electrical signal by a microphone 14 according to the present invention, which is inputted to the sound wave S, and is inputted via a transmission line 15 to a digital audio device 16 shown in a broken line frame in the figure. In the digital audio device 16, the latch clock signal A based on the sampling frequency output from the clock generator 17 causes
The latch circuit 18 temporarily holds the input digital electric signal at regular intervals, and then outputs it as a digital music signal B. This digital music signal B is equivalent to the digital music signal E shown in FIG.

Note that if the diaphragm 11 of the microphone has the characteristics of a low-pass filter with a cutoff frequency that is 1/2 or less of the sampling frequency when the microphone output signal is processed by the digital audio equipment, sampling will be easier. No aliasing distortion occurs due to the accompanying Elias effect.

(Effects of the Invention) As explained above, according to the present invention, digital electrical signals required for digital audio equipment can be obtained with a much simpler circuit configuration than the conventional method of processing using an analog-to-digital converter. be able to. Furthermore, since the output of the microphone is a digital electrical signal, there is no noise mixed in during transmission to other equipment, and since no amplifier is required, no distortion occurs other than that generated by the microphone itself.

[Brief explanation of the drawing]

FIGS. 1(a), 1(b) and 1(C) are a side sectional view, a rear sectional view taken along the AA' plane, and a front sectional view taken along the BB' plane, respectively, of a microphone according to the present invention. FIGS. 2 and 3 are block diagrams illustrating a system for supplying music signals from a microphone according to the present invention and a conventional microphone, respectively, to digital audio equipment. 1.14...Microphone, 2...Microphone amplifier, 3,15...Transmission line, 4,16...Digital audio equipment, 5...Amplifier, 6.
...Low pass filter, 7,17...Clock generator, 8...Sample and hold amplifier, 9...
Analog-digital converter, 10... housing, 1
1... Vibration plate. 11a...Absorption or transmission part, llb...Reflection part, 11c...Irradiation circle, 12...Light source, 13...Light receiving part, 13a...Reflected light receiving port, 18...Latch circuit. Figure 1(a) 10-Housing +1-J member 117A +1a-[1
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Claims (1)

[Claims] a light source having an irradiation angle; a diaphragm comprising a part that reflects the irradiated light and a part that absorbs or transmits the irradiated light, which is orthogonal to the optical axis;
It consists of a plurality of light receiving elements that receive reflected light from this diaphragm and converts it into an electrical signal, and also includes a light receiving section connected to the diaphragm, and the displacement of the diaphragm vibrated by sound waves is detected from the light source to the diaphragm. , a change in the reflected light receiving area of the light receiving section is detected by a change in the number of light received by a plurality of light receiving elements, and this is output as a digital electrical signal.