Patent US 4,155,072

A character is scanned in a plurality of parallel scan lines and the starting and ending positions of the character in the respective scan lines are detected. The portions of the character between the starting and ending positions of the respective scan lines are quantized and classified into a code. The starting and ending positions and classification codes are compared with those of standard character patterns and the character is recognized as the standard character with the closest correlation. This operation corresponds to tracing the right and left outlines of the character, and further classifying the interior of the character. Means are provided for normalizing the horizontal size, position and slant of the character prior to correlation. An improved quadratic correlation function is disclosed which selectively utilizes root mean square values of positive and negative projection components of a characteristic vector of a covariance matrix of a standard character pattern.