Investigations of analog VLSI visual transduction and motion processing

Citation

Delbruck, Tobias (1993) Investigations of analog VLSI visual transduction and motion processing. Dissertation (Ph.D.), California Institute of Technology. doi:10.7907/N5TD-G224. https://resolver.caltech.edu/CaltechETD:etd-07022004-144710

Abstract

This thesis is a detailed description of a neuromorphic visual-motion processing chip and its component parts. The chip is the first two-dimensional silicon retina with a full set of direction-selective, velocity-tuned pixels. The architecture for the chip is based on the biological correlation-type motion detector, with the addition of a novel spatiotemporal aggregation. All the processing on the chip is analog and occurs in parallel. Novel, on-chip, continuous-time, adaptive, logarithmic photoreceptor circuits are used to couple temporal image signals into the motion processing network. These continuous-time photoreceptor circuits have also been used in a wide variety of other vision chips. The photoreceptor circuits center their operating point around the history of the illumination, simultaneously achieving high sensitivity and wide dynamic range. The receptor circuits are characterized and analyzed carefully for their temporal bandwidth and detection performance. Noise properties are analyzed, resulting in a simple and intuitive understanding of the limiting parameters. Novel adaptive elements are described that are insensitive to light-generated minority carriers. Novel measurements are presented of the spectral response properties of phototransducers that can be built in ordinary CMOS or BiCMOS processes. A novel nonlinear circuit that measures similarity and dissimilarity of signals is described and characterized. These bump circuits are used on the motion chip to extract the motion energy signal, and have also been used in other chips in numerous ways.

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