Cathode ray tube with compensation for beam landing spot distortion due to wide-angle beam deflection

In a cathode ray tube comprising a tube envelope having a phosphor screen;

• an electron gun in said tube envelope including beam producing means directing at least one electron beam along the axis of said tube envelope toward said screen for impingement on the latter, and main electron lens means disposed between said beam producing means and said screen for focusing each said beam at said screen, said main electron lens means having at least two tubular electrodes arranged coaxially is succession along said axis of the tube envelope for the passage of each said beam through said electrodes with a relatively low potential being applied to one of said electrodes and a relatively high potential being applied to the other of said electrodes for producing an electrical field which effects said focusing of each said beam;
• and deflection yoke means on said tube envelope between said main electron lens means and said screen for angularly deflecting each said beam from said axis so as to scan said screen in line-scanning and vertical directions, respectively:
• the improvement of said one tubular electrode which is maintained at said relatively low potential consisting of first and second axially divided tubular electrode portions having respective end plates extending across their adjacent ends, said end plates of said first and second electrode portions having first and second apertures, respectively, which are aligned with each other for the passage therethrough of each said beam during the focusing of the latter, a first pair of diametrically opposed flanges projecting from the periphery of said first aperture in the axial direction toward said second aperture, and a second pair of diametrically opposed flanges projecting from the periphery of said second aperture in the axial direction toward said first aperture and being orthogonally disposed in relation to said first pair of flanges so as to be interfitted between the latter, so that the application across said first and second electrode portions of a correction voltage which varies with the angle of deflection of each said beam from said axis is effective to provide a varying electric field for obtaining a uniform shape of the landing spot of each said beam on said screen.