Sound Detection by Laser Microphone Using Self-coupling Effect of Semiconductor Laser

Abstract

Demand for inexpensive and wide band microphone for machine noise in factory and power station is increasing. However, frequency response is limited by diaphragm in conventional microphone. In this paper, a laser microphone based on self-coupling effect of the semiconductor laser is proposed. The laser microphone has a wide and flat frequency response. The features of the laser microphone do not need optical adjustment with simple optical system and not need post-processing by digital signal processing. The laser microphone can detect a sound wave and a human voice. This signal voltage is proportional to sound pressure and flat in frequency response in audible sound. This microphone has a omni-directivity in vertical direction.