TV receiver triple-beam CRT - uses detector to measure light level and set inter-beam ratio to control luminance without loss in fidelity

摘要

The colour CRT has its electron beam currents controlled as a function of background light level in the room containing the receiver. The ratio of the three beam currents, one to another, is controlled so that the colour picture's colour fidelity is preserved in the presence of various light levels. A photodetector (5) detects the light level (3) in the room and its output controls the ratio of the three beam currents accordingly. The CRT controls the luminance without upsetting colour fidelity.