Circuitry for preventing doming phenomenon in a television recei

Details Circuitry for preventing doming phenomenon in a television recei Circuitry for preventing doming phenomenon in a television recei

1989-08-07

1991-02-26

Britton, Howard W.

Facsimile and static presentation processing

Static presentation processing

Attribute control

358 39, 358243, H04N 916

Patent

active

049965905

ABSTRACT:
Circuitry for preventing a doming phenomenon in a color television receiver includes circuitry (5, 6, 7, 8, 9, 10) for detecting the presence or absence of a high luminance portion not less than a predetermined area on the television receiver screen, and circuitry (11, 60, 2, 3) for slowly and gradually reducing at least one of luminance and contrast of the screen when the high luminance portion not less than a predetermined area exists on the screen. The area detecting circuitry includes a circuit (5, 6; 5', 6') for detecting the presence of the high luminance portion on the screen, a first charge/discharge circuit 9 for generating a signal, the level of which shifts slowly in a first direction when this high luminance portion larger than a predetermined width exists, and shifts rapidly in a second direction when it is absent, a circuit (10) for comparing an output of the charge/discharge circuit with a second reference voltage and for deciding whether the area of the high lumiannce portion is not less than a predetermined area, a circuit (11) for generating a control signal for gradually reducing the luminance/contrast to the presence of the high luminance portion not less than a predetermined area in response to an output of the decision circuit and for rapidly recovering the luminance/contrast to the original state in response to the absence thereof.

REFERENCES:
patent: 3914545 (1975-10-01), Engel
patent: 4096518 (1978-01-01), Tuma et al.
patent: 4196446 (1980-04-01), Rowe et al.
patent: 4253110 (1981-02-01), Harwood
patent: 4253121 (1981-02-01), Avery
patent: 4587554 (1986-05-01), Tamura et al.
patent: 4689668 (1987-08-01), Sutherland II

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