Automatic contrast controller of a video camera

Details Automatic contrast controller of a video camera Automatic contrast controller of a video camera

1989-07-24

1993-01-19

Groody, James J.

Facsimile and static presentation processing

Facsimile

Specific signal processing circuitry

358166, 358167, H04N 557

Patent

active

051811170

ABSTRACT:
The invention provides an automatic contrast controller of a video camera including: a pedestal level sample-and-hold circuit for the video signal clamped to the pedestal level by the clamping pulse, a signal below reference level detecting circuit to remove the unnecessary signal by blanking so as to detect the only signal below the reference level, a lowest value detecting circuit to detect the lowest value of the average image signal detecting circuit for signal detecting average image signal and the clamped video signal, a comparing circuit to compare the output of the lowest value detecting circuit with the average signal level for amplification, and an amplifying circuit of variable gain to vary the gain of the signal below reference level detecting circuit, thereby setting the lowest signal level up to the specified level by the pedestal level and average level. Obtaining both a clean screen by provided; the video signal with a large contrast ratio and the contrast ratio compared during the vertical period of the video signal may be possible, moreover, by removing the conventional problem of the degradation of S/N ratio and non-effect of the operation according to the present invention.

REFERENCES:
patent: 3914545 (1975-10-01), Engle
patent: 3970777 (1976-07-01), Bradford et al.
patent: 3976836 (1976-08-01), Wheeler
patent: 4369466 (1983-01-01), Matsuzaki et al.
patent: 4631589 (1986-12-01), Hongu et al.
patent: 4811101 (1989-03-01), Yagi

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