High-speed pattern recognition system based on a template matching

This paper introduces a pattern recognition system based on a template matching method in industrial applications. The system can inspect various objects, after correcting the orientation. The processing time is less than 80 ms, which includes determining of the orientation of those objects, correcting of the orientation, and the template matching. It is almost the same as or less than that of the other systems which allow no rotation. In order to correct the orientation at high speed, following three techniques have been developed. Firstly, a high speed affine transformation circuit executes rotation operation in less than 8 ms for a 256 x 256 image. Secondly, other special circuits extract some features of a binary image to determine the orientation of object. Thirdly, the local-scan hardware applied to the first and second circuits scan the effective area at the scanning rate of 8 MHz. The system has three algorithms of determining the orientation. It is determined by means of the direction of the principal axis of inertia, the binary image along a circumference, and a pair of straight lines. These algorithms are selectable according to the objects. The orientation is determined with the accuracy better than +0.5 degree.