Contour correcting circuit for sharpening rising and falling edges of video signals

Abstract

A contour correcting circuit sharpens only the rising and falling edges of a video signal, without increasing the shoot levels of the video signal, to improve image sharpness on picture. Second, third, fourth and fifth delayed signals are formed, respectively by delaying an inputted first signal by a first delay time, a second delay time longer than the first delay time, a third delay time longer than the second delay time, and a fourth delay time longer than the third delay time in sequence, respectively. A first contour signal G is formed on the basis of a sixth signal obtained by subtracting the second signal from the third signal and a seventh signal obtained by subtracting the fourth signal from the third signal. A second contour signal representative of contour components is formed on the basis of the first signal, the third signal and the fifth signal. An eighth signal representative of contour emphasizing components is formed on the basis of the first contour signal and the second contour signal. Finally, a contour corrected output signal is outputted by adding the third signal and the eighth signal.

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