Abstract

Self-luminous patterns and patterns on diffusing backgrounds can be recognized in real time by means of multiple holographic filters in an approach that requires no imaging lenses. Use of filters matched to features rather than to entire characters has allowed reading of alphabetic characters printed on white paper at contrast ratios down to 1.7:1. The experimental geometry eliminates aberrations as a problem.

© 1971 Optical Society of America

Character Recognition by Incoherent Spatial Filtering

J. D. Armitage and A. W. Lohmann
Appl. Opt. 4(4) 461-467 (1965)

Hybrid incoherent optical pattern recognition system

Rand C. Sherman, Daniel Grieser, F. Trevor Gamble, Carl M. Verber, and Thomas Dolash
Appl. Opt. 22(22) 3579-3582 (1983)

Large-memory real-time multichannel multiplexed pattern recognition

Don A. Gregory and H. K. Liu
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Holographic Subtraction

K. Bromley, M. A. Monahan, J. F. Bryant, and B. J. Thompson
Appl. Opt. 10(1) 174-181 (1971)

Real-time deformation invariant optical pattern recognition using coordinate transformations

David Casasent, Shao-Feng Xia, Andrew J. Lee, and Jian-Zhong Song
Appl. Opt. 26(5) 938-942 (1987)