Plural beam electron gun for a color picture tube with different-sized control grid apertures

Claim 1

In a color picture tube having a screen with different color phosphors thereon in a repetitious pattern to be made luminescent by the impingement thereagainst of respective intensity moldulated electron beams, and in which the phosphors of one color need to be excited by a beam current substantially larger than the beam currents for the other phosphors in order to obtain a good white balance; the combination of means for generating said electron beams including cathode means having emitting surfaces for the respective beams, and control grid means having portions thereof that are substantially equidistant from said emitting surfaces and apertures in said portions aligned with said emitting surfaces for the passage of the respective beams, the one of said apertures for the passage of the beam corresponding to the phosphors of said one color being of substantially larger open area than the other apertures to provide said substantially larger beam current when a corresponding larger video signal voltage is applied between the respective cathode and control grid means, and said one aperture being divided into parts by said grid means so that said larger open area is constituted by the aggregate area of said parts, whereby to provide said larger beam current without a corresponding difference between the respective cutoff voltages for said beams.