Electron gun for colour CRT with dynamic focussing

摘要

The electron gun has a cathode (20), a control electrode (30) and an image screening electrode (40), together with static and dynamic focussing electrodes (50a, 50b) between the latter and on end acceleration, electrode (60), supplied with an accelerating anode voltage for acting as a main lens for accelerating and focussing the electron beam.The dynamic focussing voltage is varied in dependence on the point at which the electron beam hits the screen, its amplitude being greater when the electron beam scans the upper or lower part of the screen than when it scans the central part of the screen.