OPTICAL MICROPHONE

摘要

An optical microphone is provided with a propagation medium unit through which an acoustic wave propagates, a light source which emits a light wave that crosses the acoustic wave propagating through the propagation medium unit and is transmitted through the propagation medium unit, a reflection unit which retroreflects the light wave transmitted through the propagation medium unit, and a photoelectric conversion unit which receives the light wave reflected by the reflection unit and transmitted through the propagation medium unit and outputs an electric signal. In an outward route in which the light wave emitted from the light source is transmitted through the propagation medium unit, a zero-order diffracted light wave, a positive first-order diffracted light wave, and a negative first-order diffracted light wave are each generated according to the refractive-index distribution of the propagation medium unit caused by the propagation of the acoustic wave, and in a return route in which the zero-order diffracted light wave generated in the outward route is transmitted through the propagation medium unit by being reflected by the reflection unit, a zero-order diffracted light wave, a positive first-order diffracted light wave, and a negative first-order diffracted light wave are generated according to the refractive-index distribution of the propagation medium unit caused by the propagation of the acoustic wave. The photoelectric conversion unit detects interference light between the positive first-order diffracted light wave generated in the outward route and the negative first-order diffracted light wave generated in the return route and/or interference light between the negative first-order diffracted light wave generated in the outward route and the positive first-order diffracted light wave generated in the return route.