SMART-PIXEL SPATIAL LIGHT-MODULATOR FOR INCORPORATION IN AN OPTOELECTRONIC NEURAL-NETWORK

We present the design, fabrication, and testing of a novel liquid-crys tal-on-silicon optically addressed spatial light modulator for use as a weight matrix in an ART-1 optoelectronic neural processor. Each pixe l in the 50 x 83 element array occupies 75 mu m x 75 mu m and consists of a photodetector, a threshold circuit, a 1-bit (flip-flop) memory e lement, and a liquid-crystal modulating mirror. The array is designed to switch all the pixels initially to the ON state. Subsequently each pixel is independently switched to the OFF state if a superthreshold a mount of light falls upon the pixel's photodetector. The device has a contrast ratio of 20:1, a switch-on time (10-90% rise time) of 500 mu s, and a switch-off time of similar to 500 mu s (depending on the exte rnally set threshold). Measured device uniformities and interpixel cou pling are also described.