Contrast correction device for correcting video signal contrast

Details Contrast correction device for correcting video signal contrast Contrast correction device for correcting video signal contrast

1991-05-29

1993-03-23

Groody, James J.

Facsimile and static presentation processing

Facsimile

Specific signal processing circuitry

358168, 358164, 358 32, H04N 557

Patent

active

051969378

ABSTRACT:
A contrast correction device for correcting a contrast of an image formed by video signals includes a brightness/darkness detecting circuit for detecting a tone level of the image and for producing a bright signal when the tone level is greater than a predetermined brightness, and a dark signal when the tone level is less than a predetermined darkness. A correction circuit is provided for correcting a luminance signal by a negative gamma correction in response to the bright signal, and a positive gamma correction in response to the dark signal. Thus, the contrast of bright areas in the image are enhanced when the bright signal is produced, and the contrast of bright areas in the image are suppressed when the dark signal is produced.

REFERENCES:
patent: 4152720 (1979-05-01), Fenton
patent: 4489349 (1984-12-01), Okada
patent: 4686562 (1987-08-01), Yamanaka
patent: 4799106 (1989-01-01), Moore
patent: 4829381 (1989-05-01), Song
patent: 4980756 (1990-12-01), Lagoni
patent: 5003394 (1991-03-01), Lagoni

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