Gradation correction device and image sensing device therewith for supplying images with good gradation for both front-lit and back-lit objects
First Claim
1. A gradation correction device comprising:
- a feature quantity extractor, said feature quantity extractor extracting feature quantities from input digital picture signals of a picture, the feature quantities reflecting aluminance level distribution of the input digital picture signals;
a correction coefficient determinator, said correction coefficient determinator generating a correction coefficient which determines a gradation correction characteristic based on the feature quantities received from the feature quantity extractor, the gradation correction characteristic defining an output signal for an input signal;
a gain generator, said gain generator generating a correction gain which changes with a signal level of an input digital luminance signal according to the luminance signal and the correction coefficient received from said correction coefficient determinator; and
a corrector, said corrector correcting each of the input digital picture signals bymultiplying each of the input digital picture signals by the correction gain generated by said gain generator.
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Accused Products
Abstract
An average luminance Y is added to a correction coefficient by an adder. The correction coefficient characterizing the gradation correction characteristic of input picture signals of a picture is determined easily according to feature quantities extracted from input picture signals. A first gradation correction characteristic and a second gradation correction characteristic are added to a weight according to the correction coefficient and a correction gain of the gradation correction characteristic is determined. Thus, gradation can be corrected for all kinds of pictures including front-lit and back-lit objects. Further, by using the average luminance Ya, gradation is corrected in pixel units so as to keep contrast and to send an output signal with good gradation. A quantizer in the correction coefficient determination circuit quantizes the level distribution of the luminance signal and the correction coefficient determination circuit provides the correction coefficient according to the quantized value. Thus, the correction coefficient determination circuit can be constructed with a small scale circuit. A image sensing device including the gradation correction device can provide an output image wherein gradation is not deteriorated, noise is not obvious and gradation can be expressed well over an entire image plane.
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Citations
24 Claims
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1. A gradation correction device comprising:
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a feature quantity extractor, said feature quantity extractor extracting feature quantities from input digital picture signals of a picture, the feature quantities reflecting aluminance level distribution of the input digital picture signals; a correction coefficient determinator, said correction coefficient determinator generating a correction coefficient which determines a gradation correction characteristic based on the feature quantities received from the feature quantity extractor, the gradation correction characteristic defining an output signal for an input signal; a gain generator, said gain generator generating a correction gain which changes with a signal level of an input digital luminance signal according to the luminance signal and the correction coefficient received from said correction coefficient determinator; and a corrector, said corrector correcting each of the input digital picture signals by multiplying each of the input digital picture signals by the correction gain generated by said gain generator. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16)
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17. An image sensing device comprising:
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an image sensor, said image sensor detecting input picture signals of a picture and providing input digital picture signals; a feature quantity extractor, said feature quantity extractor for extracting feature quantities from the input digital picture signals of a picture, the feature quantities reflecting luminance level distribution of the input picture digital signals; a correction coefficient determinator, said correction coefficient determinator generating a correction coefficient which determines a gradation correction characteristic based on the feature quantities received from the feature quantity extractor, said gradation correction characteristic defining an output signal for an input signal; a gain generator, said gain generator generating a correction gain which changes with a signal level of an input digital luminance signal according to the luminance signal and the correction coefficient received from said correction coefficient determinator; and a corrector, said corrector correcting each of the input picture signals by multiplying each of the input digital picture signals by the correction gain generated by said gain generator. - View Dependent Claims (18)
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19. A gradation correction device comprising:
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a feature quantity extraction means for extracting feature quantities from input digital picture signals of a picture, said feature quantities reflecting luminance level distribution of the input digital picture signals; a gradation correction characteristic determination means for determining a gradation correction characteristic based on the feature quantities received from the feature quantity extraction means, said gradation correction characteristic defining an output signal for an input signal; and a correction means for correcting each of the input digital picture signals by using the gradation correction characteristic determined by the gradation correction characteristic determination means; whereby the gradation correction characteristic for the input picture digital signals is varied according to features thereof; said correction means comprising; a correction gain generation means for generating a correction gain for the input digital picture signals according to the input digital picture signals and the correction coefficient determined by said gradation correction characteristic determination means; and a multiplication means for multiplying the input digital picture signals with the correction gain received from the correction gain generation means. - View Dependent Claims (20, 21, 22, 23, 24)
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Specification