Patent US 4,402,006

An image enhancer apparatus includes an aperture correction circuit for receiving an input video signal and producing emphasized edge sharpness information for addition to the input video signal as delayed in a signal delay line. The edge sharpness information is generated employing a pair of further delay lines which provide the second derivative of the input signal. A detail enhancing circuit detects large transitions in the video signal and clamps a differentiated delayed version of the video signal at the output of the signal delay line to suppress large transitions while retaining detail information. Outputs of the aperture correction circuit and the detail enhancing circuit are adjustably combined at the input of a coring circuit which selectively removes undesired noise in order to isolate the desired information. The cored sum is added to the delayed video signal.