The area of optical neural networks has evolved by adopting the techniques proposed by various "connectionist" models. The optical implementation was first demonstrated by Psaltis and Farhat in 1985 Opt. Lett. 10, 98 (1985) and was followed by a direct optical associative memory demonstration by Anderson in 1986 Opt. Lett. 11, 59 (1986) and by Soffer, Dunning, Owechko and Marom Opt. Lett. 11, 118 (1986) as well as Yariv and Kwong Opt. Lett. 11, 186 (1986). Since this time the field has evolved rapidly and many insights, problems, and approaches have been considered. Most interesting has been Chinese to English three character recognition and translation demonstrated by Psaltis and co-workers, an optical novelty tracking filter by Anderson and co-workers, and recent work by Lischer and Lee at N. R. L. Some of the problems to be addressed include multiple image holographic storage, implementation of learning, and faster nonlinear crystals exhibiting large effects.
