An analog implementation of early visual processing in insects

An analog VLSI implementation which mimics the early visual processing stages in insects is described. The system is composed of sixty parallel channels of integrated photodetectors and processing elements. It serves as the front end processor for a motion detection chip. The photodetection circuitry includes p-well junction diodes on a 2 mu m CMOS process and a logarithmic compression to increase the dynamic range of the system. The processing elements consist of an analog differentiator behind each photodetector. The differentiators are low frequency and have been designed using subthreshold design methods.<>