A silicon retina system that calculates direction of motion

A silicon retina was fabricated to emulate two fundamental types of response in the vertebrate retinal circuit, namely the sustained and transient responses. The sustained response exhibits a Laplacian-Gaussian-like receptive field. The transient response is obtained by subtracting consecutive image frames. The outputs of the chip are offset-suppressed analog voltages since uncontrollable mismatches of transistor characteristics are compensated for with the aid of sample/hold circuits embedded in each pixel circuit. The chip was applied to extract direction of motion using FPGA in real-time under an indoor illumination.