Gradation correction apparatus
AssigneeMatsushita Electric Industrial Co., Ltd.
InventorsKeiichi Ito, Atsuhisa Kageyama
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Abstract
An object of the present invention is to provide a gradation correction device which can perform gradation correction using digital feedback processing, and furthermore, can control the digital feedback processing with high accuracy. The gradation correction device is provided with a correction gain adjustable amount generation circuit (103) and a correction gain generation circuit (104), and the correction gain adjustable amount generation circuit (103) obtains a correction gain adjustable amount which is non-linear in relation to a difference S between a reference luminance level Yb1 and a maximum luminance level, and greater gamma correction is carried out as the value of the difference is larger.
Claims6
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.
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 minimum output luminance level detection means for detecting a minimum 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 minimum output luminance level which is outputted from the minimum 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 black level correction signal generation means for generating a black level 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 black level correction signal outputted from the black level correction signal generation means, by the correction gain outputted from the correction gain generation means, and outputting the result as a black level correction amount;
- and
- a second subtraction means for subtracting the black level correction amount outputted from the multiplication means, from the input luminance signal, thereby performing black level correction on the input luminance signal.
Dependencies are inferred from the claim text.