Abstract

We use an optical rectangular-to-polar coordinate transformation system to accomplish rotation-invariant pattern recognition. The coordinate transforming device is a special computer-generated hologram. The output of the device is optically Fourier transformed, yielding a rotation-invariant output. However, the performance of the system is degraded by a wraparound effect due to the coordinate transformation. We show how the performance may be significantly improved by superimposing two coordinate transforms. The all-optical system includes the coordinate transforming device and a liquid-crystal light valve. At this time the final recognition is done by computer, but we will show how to incorporate this system into an all-optical invariant pattern recognition system.

© 1992 Optical Society of America