Patent ID: 8110813

Claim:
A charged particle optical system comprising a beamlet generator for generating a plurality of beamlets of charged particles and an electrostatic deflector for deflecting the beamlets, wherein the electrostatic deflector comprises first and second electrodes adapted for connection to a voltage for generating an electric field between the electrodes for deflection of the beamlets, the electrodes being at least partially freestanding in an active area of the electrostatic deflector, wherein the electrodes define at least one passing window for passage of at least a portion of the beamlets between the electrodes, the passing window having a length in a first direction and a width in a transverse direction, wherein the system is adapted to arrange the beamlets in at least one row and to direct a single row of the beamlets through the passing window of the electrostatic deflector, the beamlets of the row extending in the first direction, and wherein a substantial part of the electrostatic deflector extends beyond the passing window in the first direction.