DEVICE FOR CORRECTING LEVELS OF GRADATION

摘要

PROBLEM TO BE SOLVED: To solve a problem such that delicate fluctuations of analog signals are quantized by A/D conversion and are put out to a screen as noise of an amplitude of one-level gradation under use of such display systems as perform A/D conversion of analog image signals and reduce levels of gradation to put out the image signals to a display device with reduced levels of gradation. SOLUTION: Aiming at that the noise has an amplitude of one-level gradation and exists together image data in a brightness distribution of it, a brightness distribution of digital signals after A/D conversion is detected and threshold levels for reducing levels of gradation are set at brightness areas of a small amount of image data (therefore, of small noise) or troughs of the brightness distribution. This reduces the noise put out to the screen.