| 摘要 |
PURPOSE:To simplify circuit constitution by replacing a displacement a diaphragm in forward/backward direction into a change in the distance till the photodetection section from a light source via the diaphragm, detecting the range of photodetection of photodetectors as a change in the photodetection width in the photodetection section and outputting the vibration of the diaphragm due to input sound wave as a digital electric signal. CONSTITUTION:The diaphragm 11 is vibrated by a sound wave S and displaced in the forward/backward direction. The change in the distance reflected in the diaphragm 11 from a light source 12 reaching the photodetection section 14 corresponds to twice the displacement distance. Since the diaphragm 11 is not deformed but moved in forward/backward direction only, supposing the irradiation angle is 2alpha, the maximum incident angle alpha to the diaphragm 11 and it reflected angle beta are unchanged and the photodetection width of the photodetection section 14 by the reflected light is changed in proportion to twice the displacement of the diaphragm 11. The range of photodetection of plural photodetectors 13 arranged in a line is detected and calculated, then the vibration of the diaphragm 11 is converted into a digital electric signal.
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