Investigation on a microphone or a pressure sensor using optical reflection on edge surface

摘要

We propose a microphone or a pressure sensor which uses the optical reflection at the edge of a thin glass rod or a glass fiber. The optical reflection area changes as refractive index changes, which is caused by the change in the density of the outside medium due to the presence of sound. Therefore, sound pressure can be measured by measuring the change of the amount of reflection light. The efficiency of the change in the reflection area by the sound pressure depends on the shape of the edge. This paper investigates theoretically the effect of the edge shape for the spherical edge and the parabola type edge. This microphone has no mechanical vibration and its upper limit in the frequency range is high in principle.