Picture quality improving circuit

Abstract

Abstract PURPOSE:To prevent the S/N deterioration of a contour corrected picture signal by lowering a noise level more than the gain of a signal gain being lowered by controlling the gain of an input level change means. CONSTITUTION:The level of the picture signal through an input variable gain amplifier 22 is detected in a maximum level output circuit 25, when the noise is added to the picture signal and above a prescribed level, the noise level is lowered more than the gain of the signal gain being lowered through a variable resistor 35 and the gain of an output variable amplifier 33 is enhanced. When an output level through a minimum level output circuit 26 does not include the noise but is below a prescribed level, the respective gains of the amplifiers 22, 33 are controlled to be high and low. A preshoot and an overshoot are applied to the respective rise and the fall parts of the picture signal through a delay circuit 23 by a contour correction circuit 27 to have the contour corrected picture signal and outputted through a shoot waveform removing circuit 28, the amplifier 33. Accordingly, the noise is not corrected but the S/N of the contour corrected picture signal is prevented.

Inventors

• 👤 Kenichi Nagai
• 👤 賢一 永井

Bibliographic Details