PURPOSE: To decrease spherical aberration by extending the effective electrode diameter of a UPF type electron gun near to the inner diameter of the neck portion of a cathode-ray tube.
CONSTITUTION: In extending the electrode diameter of an electron gun, an electrode supporting rod is an obstacle matter in the direction where the electrode supporting rod is present 'vertical direction', however, in the direction at a right angle to the above direction 'horizontal direction', the electrode diameter can be extended near to the inner diameter of the neck portion of a glass surrounding case 1. In the vertical direction where electrode diameter is small, the distance between acceleration electrodes 7, 9 is shortened, and in the horizontal direction, the distance is extended. Then, astigmatism of a lens can be removed and a larger aperture can be obtained, and resolution is improved. In this type of electron gun, as acceleration electrodes 7, 9 are put in a focusing electrode 8, lens intensity can be controlled by the distance between acceleration electrodes, and even if focusing voltage is extremely low, proper value can be kept in the lens.
YAMAUCHI MASAAKI
KATOU KAZUHIRO
TAKANO KOU
