An analog CMOS IC for template matching

Template matching is a fundamental task in most image understanding algorithms. It consists of preprocessing a large volume of input image data to extract useful features. While straightforward it is repetitive in nature and therefore often the primary computational bottleneck in the algorithm's software and hardware implementations.;I have designed an analog CMOS IC which correlates 9 x 9 pixel windows in an image from a CCD camera with 8 pre-stored templates and outputs the matching scores. An associated analog MAX finding circuit selects the best match. The core multiply-accumulate (MAC) block consumes less than 5pJ/MAC at 320 Mega MACs/s, a factor of 10 better than ASIC DSP solutions and about 10--100 times better than programmable DSPs. An analog IC carrying the system has been manufactured in a 3V 0.5 mum CMOS process via MOSIS. Simulation results and experimental measurements are presented.;To improve algorithm speed, dedicated DSPs have been used to perform template matching; however, they provide far more precision than is needed by the task and their power consumption and size may preclude low power or mobile applications. The relatively modest but adequate accuracy of analog circuits coupled with their lower power consumption and compactness make them an attractive alternative for the realization of the template matching function and its integration onto an IC with a larger image processing system.