Color picture tube having an inline electron gun with asymmetric focusing lens

Claim 1

In a color picture tube including a screen and an inline electron gun for generating and directing three inline electron beams along separate paths toward said screen, the improvement comprising said electron gun having an asymmetric beam-forming region including three inline cathodes and at least two electrodes, a first electrode and a second electrode respectively spaced from said cathodes, each electrode including three inline apertures therein which are substantially aligned with said cathodes, and wherein said first electrode includes a separate slot superposed on each of the apertures therein, each of said slots facing said second electrode and being elongated in a direction perpendicular to the inline direction of the apertures in said first electrode, said electron gun having an asymmetric main focus lens, the asymmetry of said main focus lens being matched with the asymmetry of said beam-forming region to focus substantially all portions of each of said beams at said screen, said main focus lens including two focus electrodes, the facing portions of which each including a peripheral rim and three separate inline apertures therein set back from the rim, and said peripheral rims being elongated in the inline direction of said inline apertures and forming an asymmetric focus field, and said electron gun including a prefocus lens between said beam-forming region and said main focus lens, said prefocus lens comprising three electrodes including two electrically connected side electrodes, one of which is common with one of said main focus lens electrodes, and a center electrode which is electrically connected to the other of said main focus lens electrodes that is not common to a prefocus lens electrode.