Importance

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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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First Claim