Contrast enhancement apparatus of video signal

A contrast enhancement apparatus of a video signal comprises a coefficient generation unit for generating a low frequency mapping coefficient which increases or attenuates the low frequency component of the video signal, a minimum value processing unit for detecting the minimum value of the video signal, an edge detection unit for detecting rapid luminance change in the vertical and horizontal direction, a logarithmic conversion unit for converting logarithm by receiving the inputted video signal, a low-pass filter for passing a low frequency component of the logarithm-converted signal, a high-pass filter for passing a high frequency component of the logarithm-converted signal, a first multiplier for multiplying the low frequency mapping coefficient and a signal which passes low-pass filter, a second multiplier for multiplying the signal passes the high-pass filter by the signal outputted from the edge detection unit, a first adder for adding the signals outputted from the first multiplier and the second multiplier, an exponential conversion unit for converting exponent of the signal outputted from the first adder and a minimum value recovering unit for adding the minimum value of the video signal outputted from the minimum value processing unit thus to provide an improved contrast at real time by generating the low frequency and high frequency mapping coefficients in a proper form according to the intrinsic property, supplying the coefficient to the Homomorphic filter and controlling contrast of a video signal adaptively through first to fifth base signals by a user.