Patent ID: 7034896

Claim:
A gradation correction device for correcting an input luminance signal of an image according to an output luminance signal so that an output having a predetermined characteristic in relation to the input luminance signal can be obtained, said device comprising: a maximum output luminance level detection means for detecting a maximum output luminance level of the output luminance signal which has already been gradation-corrected; a first subtraction means for calculating a difference value between the maximum output luminance level which is outputted from the maximum output luminance level detection means, and a first reference luminance level which is supplied from the outside; a correction gain adjustable amount generation means for outputting a predetermined adjustable amount according to the difference value, on the basis of a characteristic curve such that a change in the adjustable amount to be outputted is increased as the absolute value of the difference value outputted from the first subtraction means becomes larger; a correction gain generation means for adding or subtracting the adjustable amount outputted from the correction gain adjustable amount generation means to/from the current correction gain, and outputting the result as a correction gain; a gamma correction signal generation means for generating a gamma correction signal for the input luminance signal, on the basis of a second reference luminance level which is supplied from the outside; a multiplication means for multiplying the gamma correction signal outputted from the gamma correction signal generation means by the correction gain outputted from the correction gain generation means, and outputting the result as a gamma correction amount; and a second subtraction means for subtracting the gamma correction amount outputted from the multiplication means, from the input luminance signal, thereby performing gamma correction on the input luminance signal.