Abstract: The invention relates to a cathode-ray tube having an electron gun with a main focusing lens, in which the aperture of each electrode comprises a rectangular aperture whose large dimension is along the horizontal axis (Ox) and terminating at its two ends in two identical semi-ellipses of order n that are symmetric with respect to the axis of the gun (Z) and of formula: ( x a ) 2 n + ( y b ) 2 n = 1 in which x=a cosn ?; y=b sinn ?, the parameter n has a value different from 1, a is half the width of the ellipses of order n along the horizontal axis (Ox) and b being half the height of the ellipses of order n along the vertical axis (Oy), 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, ? is an angle which varies in one quadrant between 0° and 90°.