Microphone, Fiber Optic, Refraction
Monday, September 11, 2006
A Fiber Optic Microphone has been designed and developed based on refraction, rather than reflection, for signal detection. The microphone has the following design features: 1) immune to electromagnetic interference, 2) reduced sensitivity to ambient acoustic noise, 3) made without magnetic materials, and 4) dimensions are 26 mm x 20 mm.
One fiber optic is connected to an LED (850 nm) with a laser light beam transmitted through the lens. The other Fiber Optic receives the laser light beam and is connected to a photodetector. The two Fiber Optic are aligned along the optical axis of the lens. The lens moves with a diaphragm as the pressure changes, causing the lens to refocus the laser light beam. This modulates the laser light beam, creating a pressure-dependent electrical signal.
The two multimode 200 μm core Fiber Optics have cleaved ends faces and are coaxial to each other. The coaxial lens is a spherical sapphire microlens, 1 mm in diameter. The lens is epoxy mounted to the center of a flexible polyester diaphragm, which is 25.4μm thick x 2.2 cm diameter.
Source: NASA Tech Briefs, April 1997
Reference: Micro-Optics Technologies, Inc.
Industrial Products
posted by JD52 @ 7:38 PM,
