Abstract: An optical character reader (OCR) using parallel state machines is provided wherein each state machine identifies a different character. Program tables for each of the state machines compare received bit strings of scanned data and compare them to positive and negative reference patterns in the state machines, wherein the positive reference patterns are tested for in sequence with advancement of test the next positive reference pattern only if the present positive reference pattern being tested for is present, and if none of at least one negative reference pattern is present. The OCR also detects and corrects skew by mathematically projecting a shadow of each character on the right margin of the page for each of a plurality of small incremental rotation angles for the characters. The rotation angle producing the sharpest and narrowest shadow effect is determined to the angle at which the characters are skewed.

Abstract: An optical character reader (OCR) using parallel state machines is provided wherein each state machine identifies a different character. Program tables for each of the state machines compare received bit strings of scanned data and compare them to positive and negative reference patterns in the state machines, wherein the positive reference patterns are tested for in sequence with advancement to test the next positive reference pattern only if the present positive reference pattern being tested for is present, and if none of at least one negative reference pattern is present. The OCR also detects and corrects skew by mathematically projecting a shadow of each character on the right margin of the page for each of a plurality of small incremental rotation angles for the characters. The rotation angle producing the sharpest and narrowest shadow effect is determined to be the angle at which the characters are skewed.

Abstract: An optical character recognition page reader includes a stationary paper guide for positioning documents illuminated by a stationary light source. An image of the documents is focused onto a stationary photosensitive device, e.g. a line of photodiodes, by a movable lens. Signals from the photodiodes are serially fed to a bit comparator which compares the amplitude of these signals to a threshold level that varies in accordance with a fraction of the previous maximum white level signal for each such photodiode, and produces digital bit outputs in response thereto. The digital bit outputs of the comparator for each horizontal scan of the document, i.e. each readout of the photodiode array, are stored for successive positions of the lens during its vertical scan of the document. The stored digital bits from a number of previous lens scan positions for a particular photodiode of the array are then used in a state machine to determine its next state.