System for detecting rotational angle of objective pattern

Abstract

A system and method for determining a rotational angle of an objective pattern which involves calculating the area A and linear moments M.sub.x and M.sub.y of the pattern from binary picture elements formed after optically sensing the pattern. The picture elements are stored in the memory in binary form. The center of gravity of the objective pattern is calculated on the basis of the area A and the linear moments M.sub.x and M.sub.y, and a circular or ring-like search region (a window) is formed about that center of gravity. Thereafter, significant picture information in the search region is extracted from the picture information stored in the memory (in either an inverted or non-inverted state). The rotational angle of the objective pattern is then determined either by using a moment of inertia method or a inter two-gravity centers method calculation. The selection between the moment of inertia method and the inter two-gravity centers method can be performed by means of pre-set switch state information.