Optical microphone

摘要

An optical microphone includes: a propagation medium portion; a light source to output a light wave passing through the propagation medium portion across the acoustic wave propagating through the propagation medium portion; a reflecting section to retroreflect the light wave having passed through the propagation medium portion; and a photoelectric conversion section to receive the light wave having been reflected by the reflecting section and passed through the propagation medium portion to output an electric signal. 0th-order, +1st-order and −1st-order diffracted light waves are respectively produced on outward and return paths, by virtue of a refractive index distribution across the propagation medium portion caused by the propagation of the acoustic wave therethrough. The photoelectric conversion section detects interference light between the +1st-order or −1st-order diffracted light wave of the outward path and the −1st-order or +1st-order diffracted light wave of the return path.

主权项

1. An optical microphone for detecting an acoustic wave propagating through an environment fluid by using a light wave, the optical microphone comprising:
a propagation medium portion through which the acoustic wave propagates; a light source configured to output a light wave passing through the propagation medium portion across the acoustic wave propagating through the propagation medium portion; a reflecting section configured to retroreflect the light wave having passed through the propagation medium portion; and a photoelectric conversion section configured to receive the light wave having been reflected by the reflecting section and passed through the propagation medium portion to output an electric signal, wherein: on an outward path along which the light wave output from the light source passes through the propagation medium portion, a 0th-order diffracted light wave, a +1st-order diffracted light wave and a −1st-order diffracted light wave are produced by virtue of a refractive index distribution across the propagation medium portion caused by the propagation of the acoustic wave therethrough; on a return path along which the 0th_order diffracted light wave having been produced on the outward path passes through the propagation medium portion after being reflected by the reflecting section, a 0th-order diffracted light wave, a +1st-order diffracted light wave and a −1st-order diffracted light wave are produced by virtue of a refractive index distribution across the propagation medium portion caused by the propagation of the acoustic wave therethrough; and the photoelectric conversion section detects at least one of interference light between the +1st-order diffracted light wave produced on the outward path and the −1st-order diffracted light wave produced on the return path, and interference light between the −1st-order diffracted light wave produced on the outward path and the +1st-order diffracted light wave produced on the return path.