Video processing system for television receiver

Abstract

Abstract PURPOSE:To reproduce an optimum black level in the amplitude range of all video signals by varying the DC level of a video signal in interlocking with the amplitude control voltage of the video signal. CONSTITUTION:In increasing the level of a contrast control signal Cc, the emitter potential V2 of a transistor(TR) Q2 is increased and a current flowing to a resistor R1 via a resistor R2 is increased. On the other hand, in considering the R video output signal VR supplied to the base of a TR Q1 constant, since the current i1 flowing to the resistor R1 is considered to be constant, when the current i2 is increased, the current i1 is decreased, the potential of the load resistor R3 is increased and the DC level fed to the R cathode is increased. As a result, the DC level is changed as shown in the video signal 13 and even when the video image amplitude is increased/decreased in response to the 10IRE of the original video signal 11 in the contrast adjustment, it is possible to locate the cut-off voltage to the location of 10IRE in response to the increasing/ decreasing rate.

Inventors

• 👤 Toshiya Nakamura

Bibliographic Details