Video display monitor with signal amplitude and contrast controls - employs additional source of filtered white noise whose output is superimposed on brightness control for conventional video circuitry

摘要

The display monitor has a video control circuit (2) adjusting the brightness of the display on a CRT (6). The contrast is varied by another control (7) incorporating a white noise generator (71) and a filter (72) having an attenuation characteristic of minus 3 dB/octave, and feeding the brightness control (3) by capacitive coupling (9). The contrast control signal varies in the manner of a 1/f fluctuation so that the brightness varies with time while the scanning operation proceeds with constant period. ADVANTAGE - Screen flicker reduced to minimise operator eyestrain without significant increase in cost of the appts.