Cathode ray tube with compensation for beam landing spot distortion due

Abstract

In a cathode ray tube in which an electron gun directs one or more electron beams against a phosphor screen through an electron focusing lens, preferably of the unipotential type, constituted by a plurality of tubular electrodes arranged coaxially in succession along the tube axis with a relatively low potential being applied to one of the electrodes and a relatively high potential being applied to the other electrodes, and in which each electron beam is deflected, after passing through the focusing lens, so as to scan the screen in line-scanning and vertical directions; distortion of the landing spot of each beam on the screen, particularly when deflected toward the peripheral portions of the screen, is removed or compensated by forming the tubular electrode which is maintained at the relatively low potential of two axially divided tubular electrode portions having respective end plates or walls extending across their adjacent ends and formed with aligned apertures for the passage through the latter of each beam, with a first pair of diametrically opposed flanges projecting from the periphery of one of the apertures in the axial direction toward the other aperture, and a second pair of diametrically opposed flanges projecting from the periphery of such other aperture in the axial direction toward said one 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 the two electrode portions of a correction voltage which varies with the angle of deflection of each said beam from the tube axis is effective to provide a varying electric field for obtaining a uniform shape of the landing spot of each beam on all portions of the screen.