Inline electron gun for high resolution display tube having improved screen grid plate portion

An inline electron gun for use in a high resolution color display tube, comprising

• three inline cathode assemblies for producing three inline electron beams, at least two of said electron beams operating at different electron beam currents,
• a control grid adjacent to said cathode assemblies, said control grid having three inline apertures aligned with said cathode assemblies,
• a main electron lens spaced from said control grid, said main electron lens including a first focusing electrode having three inline apertures directed towards said control grid and three inline apertures directed away from said control grid, and a second focusing electrode adjacent to and spaced from said first focusing electrode, said second focusing electrode including three inline apertures facing said first focusing electrode,
• a screen grid disposed between said control grid and said first focusing electrode, said screen grid having three inline apertures, lying in a first plane, aligned with said control grid apertures, and
• a screen grid plate portion disposed on the side of said screen grid facing said first focusing electrode, said screen grid plate portion having three inline openings therethrough, said openings comprising a center opening and two outer openings, lying in a second plane parallel to said first plane, each of said openings being associated with a different one of said apertures in said screen grid and longitudinally spaced therefrom, and each of said openings having an inline dimension and a transverse dimension, said dimensions being adjusted to control the horizontal and vertical sizes of the spot produced by each of said electron beams at a distance remote from said electron gun, so as to maximize resolution and to minimize moire and character graininess.

An inline electron gun for use in a high resolution color display tube, comprising

• three inline cathode assemblies for producing three inline electron beams which converge to a spot at a distance from said electron gun, two of said electron beams having a peak electron beam current of approximately 200 microamperes, and the third electron beam having a peak electron beam current of approximately 380 microamperes,
• a control grid, a screen grid and a main electron lens arranged successively in the order named for focusing said electron beams, said control grid being adjacent to said cathode assemblies and having three inline apertures aligned with said cathode assemblies, said screen grid being disposed between said control grid and said main electron lens, said screen grid having three levels with three inline apertures formed in the lowest of the three levels, said apertures being aligned with said control grid apertures, and
• a screen grid plate portion attached to the intermediate level of said screen grid on the side thereof facing said main electron lens, said screen grid plate portion having three inline substantially rectangular slots therethrough, each of said slots being associated with a different one of said screen grid apertures and longitudinally spaced therefrom, the two slots associated with the screen grid apertures through which the electron beams having an electron beam current of approximately 200 microamperes pass having an inline dimension and a transverse dimension smaller than those of said slot associated with the screen grid aperture through which the electron beam having an electron beam current of approximately 380 microamperes passes, and each of said slots acting on the electron beam passing therethrough to independently control the horizontal and vertical sizes of the spot produced by each of said electron beams at a distance from said electron gun, so as to maximize resolution and to minimize moire and character graininess.

An inline electron gun for use in a high resolution color display tube, comprising

• three inline cathode assemblies for producing three inline electron beams which converge to a spot at a distance from said electron gun, each of said electron beams having an electron beam current associated therewith,
• a control grid, a screen grid and a main electron lens arranged in the order named for focusing said electron beams, said control grid being adjacent to said cathode assemblies and having three inline apertures aligned with said cathode assemblies, said screen grid being disposed between said control grid and said main electron lens, said screen grid having three longitudinally spaced parallel planes with three inline apertures formed in the first plane, said apertures being aligned with said control grid apertures, and
• a screen grid plate portion attached to the second plane of said screen grid on the side thereof facing said main electron lens, said screen grid plate portion having three inline substantially rectangular slots therethrough, said slots comprising a center slot and two outer slots, the center slot being associated with the screen grid aperture through which the electron beam having the lowest peak electron beam current passes, said center slot having an inline dimension and a transverse dimension smaller than the dimensions of the outer slots, each of said slots acting on the electron beam passing therethrough to independently control the horizontal and vertical sizes of the spot produced by each of said electron beams at a distance from said electron gun, so as to maximize resolution and to minimize moire and character graininess.