| 摘要 |
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.
|
