A system includes an electrostatic lens in a path between a charged particle source and a detector. The electrostatic lens includes: a first electrode having a first aperture in the path aligned with a first axis; a second electrode in the path between the first electrode and the detector, having a second aperture in the path and aligned with a second axis that is parallel to the first axis and displaced from the first axis along a first direction; a third electrode in the path between the first electrode and the second electrode; and a potential generator coupled to the electrodes. During operation, the potential generator applies potentials to the first, second and third electrodes so that the electrostatic lens directs a beam of charged particles from the source propagating along the first axis to propagate along the second axis.