Integrated Optical Displacement Detection and Electrostatic Actuation for Directional Optical Microphones With Micromachined Biomimetic Diaphragms

In this paper, integration and packaging of directional biomimetic microphones using a diffraction-based optical displacement detection method is described. The optical detection method senses the displacement of the microphone diaphragm by monitoring the change in the intensity of a diffracted laser beam. A detailed optical model of the integrated optical detection scheme is developed and used to guide the package design. Measurement results with microphone packages suitable for hearing aid and acoustic measurement systems show that the noise and sensitivity performances of these small-sized microphones are comparable with commercial miniature directional microphones. These microphones incorporate integrated electrostatic actuators which can be used for active feedback control. This capability is also demonstrated to improve the frequency response of the microphone without degrading its noise performance.