Adjustable video gamma circuit

Details Adjustable video gamma circuit Adjustable video gamma circuit

1997-07-30

1999-05-04

Kostak, Victor R.

Television

Image signal processing circuitry specific to television

Gray scale transformation

348744, H04N 5202

Patent

active

059009187

ABSTRACT:
An adjustable gamma correction circuit that is operative to adjust grey scale distortion in a projected video signal by dynamically changing the gamma transfer function without the need to reset projector high and low amplification thresholds. The circuit includes both a linear amplification stage and a non-linear amplification stage that function to reshape the projector transfer function. At the non-linear stage consists of two pairs of emitter coupled amplifiers set at different voltage thresholds. The two pairs of emitter coupled transistors allow adjustment of the grey level of the circuit transfer function to thereby compensate for mid-level variations in the projector transfer function, thereby resulting in improved projected image quality.

REFERENCES:
patent: 3708693 (1973-01-01), Ferrier et al.
patent: 4489349 (1984-12-01), Okada
patent: 4738514 (1988-04-01), Stewart
patent: 4847524 (1989-07-01), Van Rooy et al.
patent: 4868668 (1989-09-01), Tavernetti
patent: 5251017 (1993-10-01), Riviere
patent: 5461430 (1995-10-01), Hagerman
patent: 5610666 (1997-03-01), Ueda et al.
"Analog Gamma Compensation Circuit For Liquid Crystal Display," Dec. 1, 1994, IBM Technical Disclosure Bulletin, vol. 37, NR 12, pp. 87/88.

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