Apparatus of plural charged-particle beams

A source-conversion unit to convert an electron source to multiple images of the electron source, the source-conversion unit comprising:

• a micro-deflector array configured to convert an electron beam from the electron source into a plurality of electron beamlets, and
• a micro-compensator array configured to compensate aberrations of a first beamlet and a second beamlet of the plurality of electron beamlets, the micro-compensator array comprising:
• a first micro-compensator layer comprising a first lens and a second lens, each of the first and second lenses comprising an electrode;
• and
• a second micro-compensator layer comprising a third lens and a fourth lens, each of the third and fourth lenses comprising an electrode,
• wherein the first and the third lenses are aligned each other with respect to a first local optical axis and configured to compensate the aberration of the first beamlet, and
• the second and the fourth lenses are aligned each other with respect to a second local optical axis and configured to compensate the aberration of the second beamlet.