Optical character reader with skew recognition

Claim 1

An optical character recognition system comprising: optically sensitive means for scanning characters on a document, and for producing successively bit strings representing the black character bits or white background bits in slices of each character in sequence; a plurality of state machines connected to receive said bit strings, with each state machine being provided for each different associated character by programming each state machine with a different program table, and wherein each state machine changes state in accordance with its program table in response to receipt of said bit strings, each of said program tables providing, in sequence, a plurality of positive pattern tests, characteristic of its associated character, against which said received bit strings are compared, and wherein each program table compares a received bit string with the same positive reference pattern in a positive reference pattern test until a received bit string compares favorably with the positive reference pattern, whereupon said state machine changes state to advance to the next positive reference pattern test, and wherein the program tables for at least some of the state machines provide for comparing received bit strings with at least one selected negative reference pattern, and wherein each program table causes its respective state machine to reset to an initial machine state when the received bit string compares favorably with said at least one selected negative reference pattern for that state thereby protecting against a stalled state by establishing a maximum time within which a character will be identified, or upon failure of a predetermined number of sequentially received bit strings to compare favorably with the respective positive reference pattern, and wherein the character will be identified in response to one of said state machines reaching and comparing favorably with the last of its positive reference pattern tests in the sequence.