Abstract: A aperture compensation circuit which provides improvement in picture quality when a multi-media image is displayed and an RGB monitor employing the same includes a sharpness circuit provided between input terminals and a preamplifier. A lowest value detection circuit of the sharpness circuit detects a lowest value signal from among R, G and B signals supplied from the input terminals, and a differentiation circuit differentiates the lowest value signal to produce a differentiation signal. A slice circuit slices a component of the differentiation signal which corresponds to a portion at which a change from black to white occurs with an arbitrary amplitude to produce a second differentiation signal. The second differentiation signal from the slice circuit and the R, G and B signals supplied from the input terminals are added by addition circuits to effect contour correction of the R, B and G signals. A CRT is driven by the R, G and B signals for which contour correction has been performed.

Abstract: The present invention provides a contrast control circuit capable of controlling the contrast even if the back porch is comparatively short. The contrast control circuit comprises monostable multivibrators (24, 26) which provides a background pulse and a reference pulse alternately, respectively, a switch (SW1) which clamps a video signal while the background pulse is HIGH so that the potential of the pedestal level is zero on an (N+1)th horizontal scanning line, and a switch (SW2) samples the leading edge of a reference pulse inserted in the video signal while the reference pulse is HIGH on an nth horizontal scanning line.

Abstract: A color correction circuit is disclosed, which includes three video signal lines for supplying red, green and blue signals, respectively, a first circuit for detecting a white color component, a circuit for applying the red, green and blue signals to the first detecting circuit, a second circuit for detecting a predetermined color component, a circuit for applying at least two signals of the red, green and blue signals to the second detecting circuit, a circuit for producing a difference signal between output signals of the first and second detecting circuits and a circuit for controlling at least one of the red, green and blue signals according to the difference signal.