CRT and TV tube focussing - has three disc focussing anode structure with apertures and separating distances related

摘要

The construction relates to an electron gun for a cathode ray tube (CRT) in which the anodes have rotational symmetrical openings and are used in conjunction with the focussing anode to optimise the focus. The distance between electrodes can be altered and the gun is a two part unit of, Wehnelt cylinder and electron accelerator electrode, and anodes as the focussing lens system. The object is to provide critical focus for black/white TV tubes and CRTs in test equipment. The gun comprises a Wehnelt cylinder (2) and accelerator electrode (3) and then the anode (4) and focussing electrodes (5, 6). The focussing anode assembly (4, 5, 6) has three disc electrodes with similar sized apertures (13, 5, 6) and the distance between the neighbouring electrodes is between 0.55 and 0.8 of the diameter of the aperture in the focusing electrode (5).