Patent ID: 7268477

Claim:
A cathode-ray tube having an electron gun having a main focusing lens, the electron gun comprising a focusing electrode and an acceleration electrode aligned along the mean axis of emission of the electron gun, each electrode comprising: a plate furnished with a central hole and two outer holes, the three holes of each plate being aligned along an axis parallel to the horizontal axis; and, a portion having an inner edge that defines a single aperture elongated along the horizontal axis through which all electron beam pass; wherein the three holes are diaposed in proximity to the single aperture and are parallel to the single aperture, and the single aperture comprises a rectangular central portion whose larger dimension is along the horizontal axis and end portions terminating in two identical semi-ellipses of order n that are symmetric with respect to the axis of the gun, and of formula: ( x a ) 2 n + ( y b ) 2 n = 1 in which x=a cos n θ; y=b sin n θ, the parameter n has a value different from 1, a is half the width of the ellipses of order n along the horizontal axis and b being half the height of the ellipses of order n along the vertical axis, x represents the abscissa of a point lying on the ellipse of order n and y is the ordinate of a point lying on the ellipses of order n, θ is an angle which varies in one quadrant between 0° and 90°.