PURPOSE: To integrate an element with high density on a two-dimensional plane by placing adjacently photoreceptive elements arrayed two-dimensionally and light intensity converting elements arrayed two-dimensionally so as to be opposed to each other, and allowing the photoreceptive element and the light intensity converting element to correspond to one-to-one.

CONSTITUTION: A uniform light beam from a plane light source 101 passes through a transmittivity converting element 102, converted to arbitrary intensity and reaches a photoreceptive element 103. This photoreceptive element gives a conductance corresponding to the light intensity. Also, the transmittivity converting element is addressable electrically, and can control independently the transmittivity in each synapse. Therefore, by only controlling the transmittivity converting element, an arbitrary conductance matrix Gij can be realized. Accordingly, a program is changed in a real time and at a high speed in accordance with a state variation from the external world, and the most suitable solution corresponding to a state of a system is derived quickly.