Telegraphy – Systems – Simplex-reversing periodic
Patent
1974-10-02
1976-04-20
Britton, Howard W.
Telegraphy
Systems
Simplex-reversing periodic
178 66R, 178DIG16, H04N 140
Patent
active
039521443
ABSTRACT:
An automatic background and contrast control unit is used in a facsimile transmitter or receiver unit and operates on the uncorrected video signal representing the shade of source document areas being scanned to produce a corrected output signal which accurately and uniformly represents the full range of black and white and intermediate grey areas of the document. The facsimile transmitter makes a preliminary calibrating scan in which it sequentially scans a known black area and a known white area, and the automatic background and contrast control unit fully automatically stores a first sample of the uncorrected video signal when the known black area is being scanned and stores a second sample of the uncorrected video signal when the known white area is being scanned. During subsequent scanning and transmission of the document, the automatic background and contrast control unit continually produces voltages representing the stored black and white samples and uses these voltages to continuously correct the video signal received during the scanning of the document.
REFERENCES:
patent: 2909597 (1959-10-01), Johnson
patent: 3761610 (1973-09-01), Krallinger
Britton Howard W.
Faxon Communications Corporation
Morganstern Richard
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