Image analysis – Histogram processing – For setting a threshold
Patent
1981-03-18
1984-06-05
Boudreau, Leo H.
Image analysis
Histogram processing
For setting a threshold
358282, 358285, 382 53, 382 67, G06K 938
Patent
active
044532687
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. Bits from succeeding particular photodiodes are successively applied to that state machine to affect its state. The operation of the state machine is so conditioned that if it reaches its final state, it has uniquely identified a particular character from the stored bits.
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Textbook, Applications of Pattern Recognition, Editor K. S. Fu, Prof. E. E. Purdue, CRC Press, Inc., 1982, pp. 197-236.
Boudreau Leo H.
Lundy Electronics & Systems, Inc.
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