WHITE/BLACK LEVEL COMPENSATION CIRCUIT OF BRIGHTNESS SIGNAL

摘要

PURPOSE: A circuit for compensating black/white level of a luminance signal is provided to magnify a variation near from black or while levels with a predetermined degree so as to clarify the envelope of an object in very dark or bright portion. CONSTITUTION: The circuit for compensating black/white level of the luminance signal includes a level determiner(101), a validity determiner(102) and a compensator(109). The level determiner compares the luminance signal with an upperlimit lower than a black level by a predetermined degree or with a lowerlimit higher than the white level by a predetermined degree and an output of the first state is output when the luminance signal is greater than the upperlimit value and lower than the lowerlimit value. The validity determiner counts the interval while the output is of the first state, regards the level determination as valid when the counted interval exceeds the first predetermined clock and the output of the first state is generated. The compensator delays the luminance signal until the validity determination, compensates the luminance signal to fall into the black and white level including the upper and lower limits, and outputs one of the compensated luminance signal or the non-compensated luminance signal selectively according to the validity determination result.