Telescopic mode of a cathode lens

Means of modeling a cathode lens with an almost arbitrary configuration of electrodes in the paraxial approximation have been developed, and conditions for the implementation of the telescopic mode have been determined. The interrelation of the parameters providing this mode of operation of the lens has been studied. An electron-optical scheme has been developed that guarantees the telescopic mode of a cathode lens of a real (non-idealized) design.