Scanning heterodyne acousto-optical interferometers

Optics: measuring and testing – By particle light scattering – With photocell detection

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356345, 356351, G01B 902

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active

056942168

ABSTRACT:
Compact, high performance, scanning heterodyne optical interferometers for interferometric phase-based measurement and a host of other applications are introduced. An in-line, almost common-path optical interferometer design offers robustness to externally induced phase noise via mechanical vibrations, thermal effects, and other environmental effects. Several instrument designs are disclosed for both transmissive and reflective interferometry. These interferometers use acousto-optic devices or Bragg cells to implement rapid (e.g., <50 .mu.s/scan spot) optical scanning of a test medium. Although the read optical beam scans a given test region, the double Bragg diffraction optical design of the instrument makes the final interfering output beams stationary on the two high speed photo-detectors used for radio frequency signal generation via heterodyne detection. One photo detector acts as the fixed phase reference, while another fixed photo detector picks up the test medium phase information as the optical beam scans the test region. High speed two dimensional optical scanning of a test medium is possible by using a fixed one dimensional output high speed detector array, or via the use of high speed non-mechanical electro-optic deflectors. Also, the invention can be embodied in a coherent wide bandwidth optical transmitter using fast optical scanning of spatial codes for encrypted coherently coded coherent optical fiber transmission. This coherent system for complex optical code reading and transmission is reversible in nature, and can be used for both transmit-receive coded coherent optical communications.

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