Chunghwa Picture Tubes, Ltd.

Hsiang-Lin Chang

Hsing-Yao Chen

Chun-Hsien Yeh

Yu-Kun Ma

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.

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

An inline electron gun for use in a multi-beam electron gun as in a color cathode ray tube (CRT) includes a main focus lens for focusing the electron beams on the CRT's display screen for providing a video image. The main focus lens includes plural charged grids aligned in a spaced manner along the electron gun's longitudinal axis through which plural (typically three) electron beams are directed. One or more of these charged grids includes at least two aligned common apertures for passing the three electron beams. The layered common aperture arrangement allows for increasing the length of the electron gun as well as the effective diameter of the electron gun's main focus lens for improved video image resolution without introducing electron beam astigmatism.

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Taoyuan, Taiwan

Hsiang-Lin Chang