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The optical design permits the use of much more flexible and smaller diaphragms, which can be made using silicon micro-fabrication techniques.
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This micro-machined differential microphone utilizes an optical means to convert the sound-induced motion of a diaphragm into an electronic signal. Because it can be manufactured with high sensitivity and low noise, this lightweight microphone design offers a means to improve hearing aids and cellular phone applications. This invention overcomes changes in capacitance performance limitations by using an optical detection scheme based on a low-power semiconductor laser and optical gratings incorporated into the microphone diaphragm. Because the overall compliance of the microphone diaphragm is adjustable over a very wide range, it is possible to achieve high sensitivity and very low noise performance. ADVANTAGES: The optical design permits the use of much more flexible and smaller diaphragms, which can be made using silicon micro-fabrication techniques. It achieves higher signal to noise ratios than are possible in capacitive sensing schemes. It has a much lower noise detection floor relatively low power consumption, and is lightweight. INTELLECUTAL PROPERTY: US 7,826,629, 8,503,701, & PCT/US2007/01406