Amplifier back-ground control apparatus for use in a document sc

Details Amplifier back-ground control apparatus for use in a document sc Amplifier back-ground control apparatus for use in a document sc

1974-11-21

1976-08-24

Griffin, Robert L.

Telegraphy

Systems

Simplex-reversing periodic

178 6, H04N 132

Patent

active

039768333

ABSTRACT:
An arrangement for use in a document scanning system to provide background control of signals representative of the information content of a scanned document. An amplifier includes an automatic background control portion and an automatic black level adjustment portion to maintain the integrity of the output voltage range independent of the background of the scanned document and throughout the period of time required to scan the entire document. In addition, circuitry is provided for varying the time constant of the automatic background control circuitry to make that circuitry respond quickly to changes of the background toward the "white" direction. Further, the normally white platen back at the scanning station is provided with a gray leading edge to prevent the automatic background control circuitry from being upset by initial runs of white in the event of an imperfectly registered non-white document.

REFERENCES:
patent: 3339018 (1967-08-01), Brown
patent: 3375447 (1968-03-01), Van Der Beek
patent: 3379826 (1968-04-01), Gray
patent: 3531590 (1970-09-01), Jachim
patent: 3557309 (1971-01-01), Graham
patent: 3600506 (1971-08-01), Richeson
patent: 3609234 (1971-09-01), Hirata
patent: 3619493 (1971-11-01), Krallinger
patent: 3670100 (1972-01-01), Briggs
patent: 3678393 (1972-07-01), Newell
patent: 3700794 (1972-10-01), Loose

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