Abstract: A pair of ring-shaped magnets, or magnetic pole pieces, having the same magnetic field strength, or magnetic flux density, are disposed about the neck portion of a cathode ray tube (CRT) for statically converging a plurality of inline electron beams on the CRT's faceplate. The magnetic ring pair includes an inlet ring magnet facing the CRT's base and an outlet ring magnet facing the CRT's faceplate, with the inlet ring magnet having a thickness greater than that of the outlet ring magnet along the CRT's longitudinal axis. The inlet ring magnet thus exerts a larger off-axis force on the electron beam than the outlet ring magnet because of the longer beam path in the inlet ring magnet to permit the magnetic ring pair to apply a maximum convergence correction for substantially misconverged electron beams and a minimum convergence correction when the beams are in convergence.

Abstract: An electron gun such as used in a cathode ray tube (CRT) includes an Einzel lens having charged G3, G4 and G5 grids for focusing an electron beam on the CRT's display screen. The G3, G4 and G5 grids are cylindrical and have the same inner diameter, with their respective longitudinal axes colinear and aligned with the electron beam axis. Where T is the thickness of a grid and L is the G3-G4 or G4-G5 spacing, or gap, shielding against stray electrostatic fields within the grids arising from stray electrons on either a grid-supporting glass bead or on the inner surface of the CRT's neck portion is provided by maintaining the relationship 3.0.gtoreq.T/L.gtoreq.0.75. Another embodiment employs thinner grids having a thickness t with outward turned end flanges, or folded edges, disposed about facing edges of adjacent grids having a thickness T, where T>t and the above-stated relationship of T/L is maintained.

Abstract: An inline electron gun for use in a multi-beam color cathode ray tube (CRT) has a main focus lens for focusing the electron beams on a display screen of the CRT. The main focus lens includes adjacent charged electrodes each having chain link-type common lens apertures through which the electron beams are directed and which are in facing relation for reducing horizontal spherical aberration of the electron beams on the CRT display screen, where each common lens aperture has a longitudinal axis aligned with the inline electron beams. Each common lens aperture includes spaced, vertically enlarged portions, each aligned with a respective electron beam, for correcting for vertical spherical aberration of the electron beams. Increasing the vertical dimension of that portion of each of the common lens apertures aligned with a respective electron beam reduces the vertical spot size of the electron beam without degrading other electron gun operating characteristics.

Abstract: A limiting aperture disposed in a low voltage, beam forming region (BFR) of an electron gun in a cathode ray tube (CRT) provides reduced electron beam spot size with low power dissipation. The limiting aperture is located in a low voltage, electrostatic field-free region, preferably in the screen grid electrode G.sub.2, where the field-free region is formed by increasing the thickness of the screen grid electrode G.sub.2 to 1.8 times the diameter of a pair of circular recessed portions in opposing surfaces of the screen grid electrode G.sub.2 which are separated by the small diameter limiting aperture on the electron gun's axis through which the beam is directed. A narrow, relatively electrostatic field-free zone is thus formed in the center of the screen grid electrode G.sub.2 which is maintained at a relatively low voltage, i.e., ranging from approximately 300 V to less than 12% of the anode voltage.