Multi-mode, hybrid-type CRT and electron gun therefor with selectable different sized grid apertures

摘要

A color cathode ray tube (CRT) includes a multi-beam electron gun capable of operating in two or more modes for use as either a television receiver display or as a high resolution video monitor. The electron gun directs a plurality of electron beams onto the CRT's display screen, with the electron beams arranged in two or more groups. In one group of electron beams, the beam forming portion of the electron gun provides small diameter electron beams having reduced spot size on the CRT's display screen for high video image resolution when used as a monitor for graphics and/or character display. In another group of electron beams, the beam forming portion of the electron gun provides electron beams having a larger diameter and current for increased video image brightness when used as a television receiver. Each group of electron beams includes a plurality of horizontally aligned electron beams, with each beam providing one of the primary colors of red, green, or blue. The G2 control grid is divided into an upper G2 control grid for use in the television receiver mode of operation and a separate lower G2 control grid for use in the high resolution mode of operation, which grids may be independently positioned relative to the G1 screen grid and provided with selected, independent voltage values. By independently establishing the G1-G2 grid spacing and beam cutoff voltages for the two modes of operation, flexibility in electron gun performance and design is afforded.