Patent ID: 7420179

Claim:
An electron microscope comprising: a spherical aberration corrector using a multipole element excited with a coil current I, the multipole element having a bore radius of b; an objective lens; and transfer optics mounted between the multipole element and the objective lens, wherein the transfer optics is so designed that ratio M(=r 1 /r 0 ) is set greater than 1, the distance r 1 being the distance of an incident point to the objective lens for electrons from an optical axis, the electrons passing across a point located at the distance r 0 from the optical axis within the multipole element, and wherein at least one of the current I and the bore radius b of the multipole element is so determined that spherical aberration coefficient C st of the objective lens including contribution X 0 from the spherical aberration corrector is set to less than a given value.