Abstract: Electron gun for colour cathode ray tube comprising two successive electrodes to form a focusing lens, both electrodes each comprising three in-line apertures. The extremity of the electrode brought to the focusing voltage comprises a plate, drilled with in-line apertures. This plate is folded in such a manner that the lateral apertures are arranged in a plane different from the plane of the central aperture. The extremity edge of the electrode comprises an internal peripheral lip that extends according to a longitudinal direction Z, following a width at the level of the central aperture different from its width at the level of the lateral apertures. This structure enables the two main functions of a focusing lens to be controlled independently: the difference in focusing between the lateral beams and the central beam the difference in astigmatism of the central beam with respect to the lateral beams.

Abstract: A method for operating a cathode-ray tube electron gun, suitable for multimode operation, for example, in order to display television images and multimedia images of the SVGA, XGA type, in which the zone for forming the electron beam generated by the cathode has at least two control electrodes. The two control electrodes are connected to voltage sources in such a way that the potential difference between the two control electrodes increases when the beam current decreases.