Real-time motion detection using an analog VLSI zero-crossing chip

The authors have designed and tested a one-dimensional 64 pixel, analog CMOS VLSI chip which localizes intensity edges in real-time. This device exploits on-chip photoreceptors and the natural filtering properties of resistive networks to implement a scheme similar to and motivated by the Difference of Gaussians (DOG) operator proposed by Marr and Hildreth (1980). The chip computes the zero-crossings associated with the difference of two exponential weighting functions and reports only those zero-crossings at which the derivative is above an adjustable threshold. A real-time motion detection system based on the zero- crossing chip and a conventional microprocessor provides linear velocity output over two orders of magnitude of light intensity and target velocity