Gamma compensation apparatus

Details Gamma compensation apparatus Gamma compensation apparatus

1998-03-05

2001-04-10

Eisenzopf, Reinhard (Department: 2614)

Television

Image signal processing circuitry specific to television

Gray scale transformation

C348S254000, C348S255000, C348S256000, C348S674000, C348S675000, C348S676000, C348S677000, C358S451000, C358S500000

Reexamination Certificate

active

06215529

ABSTRACT:

FIELD OF THE INVENTION
The present invention relates to a gamma compensation apparatus used in a color television receiver.
BACKGROUND OF THE INVENTION
Television receivers having a high additional value have been developed and color television receivers having image quality correction circuit such as gamma compensation is desired.
In usual color television receivers, only a luminance signal Y is gamma compensated and chrominance signals are not gamma compensated. Accordingly, usual color television receivers have a problem that a red color with high saturation is not correctly reproduced in its tone, so-called “tone crush of a red color” occurs and color reproducibility is not good.
SUMMARY OF THE INVENTION
To solve the above problem, a gamma compensation apparatus of the present invention used in a color television receiver includes:
a high APL detection circuit, being supplied with an average picture level (APL) of a luminance signal and for taking out a signal component higher than a designated level;
a first gain controller for controlling a level of the signal taken out at the high APL detection circuit;
an adder for adding a designated offset to the output of the first gain controller and setting a compensation starting point of gamma characteristic;
a slice circuit, being supplied with a color difference signal (R-Y) and the output signal of the adder and for slicing the color difference signal (R-Y) according to the output signal of the adder;
a second gain controller for reducing the output level of the slice circuit by a predetermined rate; and
a subtracter for subtracting the output signal of the second gain controller from the color difference signal (R-Y);
and is characterized by improving color reproducibility of a red part of a color difference signal (R-Y) with high color saturation.


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