Optical EngineeringMultiplexed interferometer for ultrasonic imaging applications
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A multiplexed laser interferometer is presented that allows for the simultaneous detection of acoustic waves from a number of points on the surface of a specimen. Phase gratings are used to create an array of laser beams that are directed to the specimen. The beams are collected using a lens system, combined with a single reference beam in a photorefractive crystal, and imaged on separate photodetector elements. Detection of surface acoustic waves scattered from a defect in an aluminum specimen is demonstrated using a nine-element receiver. Focusing of the array interferometer, by applying appropriate phase shifts between the detected signals, is also shown. The wide bandwidth and noncontact nature of this receiver make it well suited for phased array detection and ultrasonic imaging applications.