METHOD OF DETERMINING AN OPTIMUM THRESHOLD FOR OBTAINING BINARY IMAGE SIGNAL FOR USE IN A PATTERN RECONGITION SYSTEM

A method of determining an optimum threshold for obtaining a binary image signal for use in a pattern recognition system is disclosed in which a pattern of a predetermined shape which exists at one or a plurality of positions on a surface of an object to be imaged is previously stored as a reference pattern. A threshold for obtaining a binary signal is changed stepwise. A video signal is converted into the binary signal on the basis of each value of threshold to obtain a binary image. A plurality of partial patterns which are different in position on the binary image to each other, are successively cut out of the binary image to be compared with the reference pattern. The overall degree of coincidence between the plural partial patterns and the reference pattern is calculated, and a value of threshold at which the overall degree of coincidence is highest, is selected from various values of threshold.