| 摘要 |
PURPOSE:To omit a converting process to an electric signal, to apply it to optical transmission as it is,to minimize an influence of an external noise,and also to take out fine vibration by taking out the vibrating information of a diaphragm as interference light. CONSTITUTION:On the first layer 11 having prescribed thickness, the second layer 12 whose refractive index is different from that of the first layer 11 is provided closely. On the surface of the opposite side of a boundary surface 16 to the first layer 11 of the second layer 12, a diaphragm 13 is provided, so that the thickness of the second layer 12 is varied by vibration of the diaphragm 13. Also, a light reflecting plate 14 is provided on the inside of the diaphragm 13. In this state, reference wavelength light 3 is emitted from a light emitting device 1, the first reflected light 9 which has been reflected by the boundary surface 16, and the second reflected lights 10, 10A which have been reflected by the light reflecting plate 14 and have been emitted through the second layer 12 and the first layer 11 are photodetected by a photodetector 2, and vibrating information of the diaphragm 13 is taken out from the interference light of both beams of the reflected light.
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