An integrated cortical layer for orientation enhancement

This paper presents a set of two analog chips performing the following chain of operations: phototransduction of an image projected on the first chip, edge enhancement by high-pass filtering, current-to-pulse frequency conversion of the filtered image, and pulse coded transmission of the filtered image to the second chip which generates a “projective field” whose shape and size are widely programmable through few bias lines. The end result of the processing chain is an image with enhanced edges along a programmable orientation. The design of this system draws from the knowledge gathered by neurobiologists about the first steps of visual perception: retinal image processing and coding followed by “simple cells” processing in the visual cortex. The focus of the paper is on the cortical layer chip since information about the retina is available elsewhere. The system´s main advantages are real time operation and ease of module interconnection for true parallel processing