Abstract

We have developed a novel optical method which uses a ring resonator with appropriate optics to perform scaling and rotation on an input image. It generates, either simultaneously or in sequence, the rotated/ scaled versions of the input picture. A dove prism is used for rotation by a given incremental angle while the scaling operation is achieved through a telescoping pair of lenses for a given magnification/demagnification ratio. A ring resonator is used to partially feed back each output for further iteration. A photorefractive crystal pumped with an external beam can also be inserted into the resonator to provide the optical gain needed to compensate for the cavity loss. This technique precludes the necessity of having to store a large library of rotated/scaled versions of a given spatial pattern for pattern recognition using Fourier transform correlators.

© 1989 Optical Society of America