An electron beam current modulator is provided between a cathode and a laser screen of a cathode-ray tube and has at least three deflecting plates positioned around, and symmetrically with respect to an optical axis of the cathode-ray tube and a diaphragm having an aperture of a regular shape. An electromagnetic control system is provided between the cathode and deflecting plates. A pickup senses position of the electron beam and produces a signal in case of an offset of the electron beam with respect to the optical axis. A video signal source is connected to a carrier generator having an output connected to an input of a phase shifter. The phase shifter has its outputs connected to the deflecting plates to rotate the cross-section of the electron beam in a plane drawn perpendicularly with respect to the optical axis. The apparatus has a control unit having an input connected to the pickup and an output connected to the electromagnetic control system.