Abstract

Recently, much attention has been focused on the optical novelty filter¹ because of its parallel processing nature. An optical novelty filter is capable of extracting the nonstationary parts of an optical image, i.e., it can simulate the motion-detecting function found in the vision systems of some animals, e.g., frogs, and is potentially useful in the target-tracking system. The optical novelty filter has been implemented using two-beam coupling or four-wave mixing in photorefractive crystals, e.g., BaTiO₃. We report the basic properties of a singlepixel GaAs optical novelty filter inplemented using phase conjugate interferometry (four-wave mixing). The relations between the response times of the phase conjugate mirror and the optical novelty filter and between those of the phase modulator (piezomirror) and the optical novelty filter were experimentally investigated. The resolution of an optical novelty filter is discussed and derived. From the derived expression, a photorefractive medium can be selected to yield the maximum output resolution possible. Based on this and the short response time of GaAs, a GaAs optical novelty filter has the potential of being a high resolution device of its kind.

© 1989 Optical Society of America