Patent ID: 8519353

Claim:
A method of controlling deflection of a charged particle beam in an electrostatic lens, comprising: establishing a symmetrical electrostatic lens configuration comprising a plurality of electrodes disposed at unadjusted positions that are symmetric with respect to a central ray trajectory of the charged particle beam with applied unadjusted voltages that create fields symmetric with respect to the central ray trajectory; calculating a symmetrical electric field corresponding to the set of unadjusted voltages; arranging the plurality of electrodes at adjusted positions that are asymmetric with respect to the central ray trajectory, wherein the plurality of electrodes includes a plurality of upper electrodes and plurality of lower electrodes, wherein the plurality of lower electrodes diverge from the central ray trajectory; obtaining a set of adjusted voltages for the plurality of electrodes, wherein the set of adjusted voltages corresponds to a set of respective potentials of the symmetric electric field at respective adjusted asymmetric positions; and applying the set of adjusted voltages to the plurality of electrodes arranged at the adjusted positions that are asymmetric with respect to the central ray trajectory when the charged particle beam passes therethrough.