Common focusing electrode for plurality of beams and having same plurality of internal shields

Claim 1

An improvement in a cathode ray tube multibeam bipotential electron gun structure having a longitudinal axis therethrough and having electron generating means therein formed to emit a plurality of separately controlled electron beams whereof each beam emanates from a substantially longitudinal arrangement of several related apertured grid electrodes positioned in sequential orientation in front of a rear positioned cathode component, said improvement being in the forward region of said electrode arrangement and comprising: a common focusing electrode member having a forward oriented front aperture plane spaced longitudinally from a rearward oriented rear aperture plane, said planes having a similar plurality of substantially circular related apertures therein, each of said front apertures having a defined tube-like extensive encompassing member of substantially cylindrical shaping integral with said front aperture plane and fabricated to extend rearward therefron a related smaller-dimensioned rear aperture formed in said rear aperture plane To effect shielding for the respective electron beam passing therethrough; each of said tube-like shielding members being of substantially equal cross-sectional dimensioning and having a length at least equaling 50 percent of the radius of the associated front aperture; and a common accelerating electrode member positioned forward of said focusing electrode member and having an aperture plane proximal to the front aperture plane of said focusing electrode member, said accelerating electrode aperture plane having a plurality of apertures therein substantially mating in a spatial manner with the front oriented apertures of said focusing electrode member, at least two of said accelerating electrode apertures being eccentrically aligned relative to said related focusing electrode front apertures to form nonsymmetrical electrostatic lenses for focusing the respective individual electron beams traversing the particular region; each of said focusing electrode shielding members providing enhanced beam focusing by effecting improved symmetry of the equipotential lines of force in particularly the region of low beam velocity in the focusing electrode portion of said electrostatic lensing field.