Aberration corrector for instrument utilizing charged-particle beam

An aberration corrector for use in an instrument utilizing a charged-particle beam, said aberration corrector being incorporated in optics of said instrument, said aberration corrector comprising:

• four stages of electrostatic quadrupole elements including two central stages of quadrupole elements;
• two stages of magnetic quadrupole elements for superimposing a magnetic potential distribution analogous to an electric potential distribution created by said two central stages of quadrupole elements on said electric potential distribution;
• an objective lens for focusing the charged-particle beam onto a specimen;
• an objective aperture placed in a part of an optical path for the charged-particle beam;
• an additional lens mounted between a quadrupole element assembly formed by said four stages of electrostatic quadrupole elements and said objective lens;
• a manual operation portion permitting one to modify an accelerating voltage for the charged-particle beam or a working distance between the objective lens and the specimen;
• and
• a control portion for controlling said four stages of electrostatic quadrupole elements, said two stages of magnetic quadrupole elements, said objective lens, and said additional lens according to a manual operation or setting performed on said manual operation portion.