In this paper, optical neural networks under development in our laboratory
are reported, together with several novel devices for building advanced systems.
This paper is divided into three parts. At first, neural network models which
permit us to use commercially-available binary-operating devices are described,
including both the feedback model and the feedforward model. Secondly, a
GaAs/A1GaAs optical associative neuro-chip based on the feedback model, in
which 32 neurons are implemented in an optical integrated structure, is
introduced. Next a three-layered dynamic optical network which can recognize 26
characters of alphabet is described, using a spatial light modulator as the
synaptic interconnection device. The emphasis is placed on the unique learning
rule using the feed forward model. In the third part, fututre trend of optical
neurochips is discussed.