Multiple charged-particle beam apparatus and methods of operating the same using movable lenses

A charged particle beam apparatus to inspect a sample, the apparatus comprising:

• a charged particle source configured to emit a charged particle beam along a primary optical axis;
• a source conversion unit configured to convert the charged particle beam into a plurality of sub-beams to form a plurality of images of the charged particle source, the source conversion unit comprising:
• an aperture-lens forming electrode plate configured to be at a first voltage;
• an aperture lens plate configured to be at a second voltage that is different from the first voltage for generating a first electric field, which enables the aperture-lens forming electrode plate and the aperture lens plate to form a plurality of aperture lenses of an aperture lens array to respectively focus a plurality of beamlets of the charged particle beam;
• a beam-limit aperture array positioned downstream of the aperture lens plate with respect to a path of the charged-particle beam and configured to limit beam currents of the plurality of beamlets exiting the aperture lens plate;
• and
• an imaging lens configured to focus the plurality of beamlets on an image plane;
• and
• an objective lens configured to focus the plurality of beamlets onto a surface of the sample and form a plurality of probe spots thereon.