Color CRT electron gun with progressively reduced electron beam passing aperture size

摘要

An electron gun includes plural aligned charged grids each having an aperture (in a monochrome CRT) or plural apertures (in a color CRT) through which an electron beam (or beams) is directed. The beams emitted by a cathode sequentially transit a beam forming region (BFR), a dynamic focus lens and a main focus lens prior to being incident on the CRT's display screen. The electron beam tends to expand in diameter in the direction of the CRT's display screen. This results in an increase in the focusing effect on the electron beam of the electron gun's grids in proceeding from the BFR toward the display screen where the beam passing apertures in the various grids are of the same size. To increase electron beam focusing sensitivity while reducing the beam's dynamic focus voltage, the beam passing apertures in the gun's dynamic focus lens are provided with progressively reduced size in proceeding toward the electron gun's cathode.