Electron gun for colour cathode ray tube - compensates change in strength of main focussing lens with dynamic quadripole focussing lens.

摘要

A vertically and a horizontally extending electron beam apertures are formed in the output plane of the third focussing electrode (16) and the input plane of the fourth focussing electrode (17). A static focussing voltage is applied to first and third electrodes. An anode voltage, which is higher than the highest dynamic focussing voltage, is applied to the end acceleration electrode (18). An axially symmetrical unipotential electron lens is formed, which is synchronised with the deflection signal and has high focusing strength, by the first, second and third focusing electrodes (14,15,16). A four pole lens, which is synchronised with the deflection signal and compensates a de-focusing in consequence of the astigmatism of a deflection yoke and the difference between the deflection distances, is formed by the third and fourth focusing electrodes. ADVANTAGE - Effectively compensates distortion of electron beam spots on edge area of screen and forms beam spots with regular size over whole screen.