A pair of dielectric plates have control electrodes formed on oppositely positioned broad surfaces thereof, there being an evacuated narrow space formed between such surfaces to provide paths for an electron beam between a cathode and a target. Such surfaces have conductive control electrodes formed thereon, the electrodes on one of the plates including paired electrodes arranged in a coded finger pattern defining electron beam channels between the cathode and target. The electrodes encompass substantially all of the plate surface area between which the channels are formed. Binary control signals are utilized to apply potentials to preselected ones of said electrodes to create transverse electric fields in the channels bounded thereby, thereby aborting the electron beam in such channels. The beam is in this manner permitted to pass through channels of the scanner in which there are no transverse fields so as to excite the target portions located by these channels.
