Timothy P. Allen

Orientation-Selective VLSI Retina

In both biological and artificial pattern-recognition systems, the detection of oriented light-intensity edges is an important preprocessing step. We have constructed a silicon VLSI device containing an array of photoreceptors with additional hardware for computing center-surround (edge-enhanced) response as well as edge orientation at every point in the receptor lattice. Because computing the edge orientations in the array local to each photoreceptor would have made each pixel-computation unit too large (thereby reducing the resolution of the device), we devised a novel technique for computing the orientations outside of the array. All the transducers and computational elements are analog circuits made with a conventional CMOS process.

A silicon retina for computing local edge orientations

Carver Mead has demonstrated the suitability of VLSI arrays of photoreceptors and analog CMOS processing circuitry (so-called silicon retinas) for doing early vision processing. So far, chips have been built that perform center-surround (X-system) and motion detection (Y-system) operations. This Paper describes a chip which was designed to perform a low level of image feature extraction: orientation selectivity.