ANALOG VLSI CIRCUITS FOR STIMULUS LOCALIZATION AND CENTROID COMPUTATION

An analog aggregation network that extracts the position of a stimulus in a sensory field is presented. This network is integrated with photodiodes in a VLSI circuit that performs stimulus localization through the computation of the centroid of a visual image. In this implementation, bipolar transistors and global subtraction are used to produce a high-precision centroid implementation. Theory for the localization of a bright visual stimulus is developed, and the theoretical predictions are compared to experimental data taken from the 160X160-pixel centroid circuit. Finally, the applications of these circuits to more complex feature extraction and to sensorimotor feedback systems are discussed.