a picture display device includes a display unit having a vacuum envelope which is provided with a transparent face plate , having a luminescent screen , and a rear plate . the display unit has a plurality of juxtaposed sources for emitting electrons , a plurality of electron transport ducts cooperating with the sources for transporting the electrons in the form of electron currents , and selection means for withdrawing each electron current at predetermined locations from its transport duct and for directing the withdrawn current toward desired pixels of the luminescent screen . in order to direct the correct quantity of electrons into the electron transport ducts for relevant video information , the voltages applied to the grids are modulated with a video signal and a uniformity correction signal . one of these signals controls a pulse - duration and the other signal controls a pulse - height of the drive signals .