Luminance gradation correcting apparatus for a video signal

摘要

A luminance gradation correcting apparatus which can properly correct the gradation of a luminance level even if a size of actual image portion of an image differs from a size of image. The apparatus has: a masking part for allowing only a luminance signal of a pixel in a predetermined detecting range in the vertical direction in an image shown by an input luminance signal to pass; a histogram memory for forming frequency data at each luminance level of the luminance signal outputted from the masking part at every predetermined period and storing it; a correcting part for correcting the luminance level of the input luminance signal based on the frequency data in the histogram memory; and a detecting range setting part for obtaining an accumulation value of the frequency data with respect to the luminance signal in a portion of the luminance level in a range from the zero level to the non-image display color level in the input luminance signal and setting the predetermined detecting range based on the accumulation value.