An electrostatic lens assembly for a charged particle beam tube and a method of operating the same.

摘要

A unipotential electrostatic lens assembly for an electron or other charged particle beam tube comprises: a lens assembly (21) of axially aligned electrostatic lens elements (21A-21C) each lens element having an array of micro lenslet apertures formed therein and with each set of axially aligned micro lenslet apertures in the lens assembly forming a micro lenslet a high voltage power supply (18) for applying an excitation potential to one of the lens elements (21B) and a source (22) for applying a dynamic focus correction potential derived from deflection potentials applied to the charged particle beam tube to another lens element (21 A) different to that to which the excitation potential is applied.