Screen brightness control stabiliser for photographic print prodn from CRT source - uses video input signal selector switch, when video source is not in blanking-out mode

摘要

A video source (10) generates an image representing video input signal and is coupled to the stabilising system by a DC voltage. A switch (12) selects the video input signal, when the video source is in non-blanking-out mode. It selects a reference voltage, when the source is in a blanking-out mode. To the switch and CRT (20) is coupled an amplifier (13) for the video input signal. Shutter control (8) and switch signal gate (9), coupled to the switch, receive the blanking-out signal for CRT screen image erasing. Switches (24) are coupled to the amplifier output, a voltage storage capacitor (25), and eraser (9), and are made on application of the blanking out signal. USE/ADVANTAGE - For image brightness control of CRT screen photocopier, with uniform brightness independent of temp. variation, and component ageing.