Contrast compression circuits

Details Contrast compression circuits Contrast compression circuits

1975-11-17

1977-11-08

Martin, John C.

Facsimile and static presentation processing

Static presentation processing

Attribute control

358164, 358169, H04N 953, H04N 520, H04N 5535

Patent

active

040578283

ABSTRACT:
An amplitude compression circuit for de-emphasizing variations in amplitude of a wide band electrical signal. A gamma circuit is used to compress amplitude variations in the wide band signal. A linear signal is subtracted from the compressed signal, producing a difference signal which represents the portion of the compressed signal resulting from the compression process. The difference signal is multiplied by a controlled factor and then added back to the unprocessed wide band signal to produce a second compressed signal. By varying the controlled multiplication factor, the amount of compression of the second compressed signal is linearly and controllably altered. To prevent emphasizing the noise portion of the signal, the wide band signal is cored before processing by the compression difference circuit. The coring circuit removes noise by subtracting the low amplitude, high frequency portion from the wide band signal. To reduce the high frequency loss inherent in coring, the wide band signal to which the multiplied difference signal is added is uncored.

REFERENCES:
patent: 3333055 (1967-07-01), Krause
patent: 3602737 (1971-08-01), Radecke
patent: 3604841 (1971-09-01), Ettlinger et al.
patent: 3684825 (1971-02-01), Dischert
patent: 3715477 (1973-02-01), Olson et al.

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