Pattern rotation angle detecting system

Abstract

A pattern rotation angle detecting system in which the angle of rotation of a pattern is detected according to the image data obtained by binary-coding and spatially-dividing the image signal of the pattern. The system comprises an extracting circuit for extracting the area and the moment of inertia of the image of the pattern directly from the binary-coded image data; a memory for storing the image data; and a processing circuit for obtaining the center of gravity of the image of the pattern using the area and the moment of inertia, circularly scanning the memory in such a manner that a circle is described having a center at the center of gravity, extracting arcuate segments, selecting as a reference arcuate segment one of the arcuate segments which satisfies predetermined conditions, mating a sample under detection with a standard sample using the properties of the reference arcuate segment and at least one arcuate segment from each side of the reference segments, and detecting the angle of rotation from the angle defined by the angle formed by a rotation angle reference point of the reference arcuate segment with respect to a predetermined reference line.