Abstract: The electron beam emanated by a single electron gun falls, after traversing two successive quadrupolar electron lenses, on a beam separator electrode having a pair of vertically spaced apertures formed therethrough for permitting the passage of fractions of the incident beam as two separate beams for dual image display. Subsequently deflected vertically by respective pairs of vertical deflection plates, the two display beams follow their trajectories to a target screen through a focus corrector device, a third quadrupolar electron lens, a pair of horizontal deflection plates, and a dome-shaped scan expansion mesh. Were it not for the focus corrector device, the spots of the display beams on the screen would differ in size according to whether they were deflected upwardly or downwardly by the vertical deflection plate pairs disposed respectively above and below the tube axis.