| 摘要 |
The chromatic aberration corrector (100) has a first multipole element (110) for producing a first electromagnetic field and a second multipole element (120) for producing a second electromagnetic field. The first multipole element (110) first, second, and third portions (110a, 110b, 110c) arranged along an optical axis (OA) having a thickness and producing a quadrupole field in which an electric quadrupole field and a magnetic quadrupole field are superimposed. In the first and third portions (110a, 110c), the electric quadrupole field is set stronger than the magnetic quadrupole field. In the second portion (110b), the magnetic quadrupole field is set stronger than the electric quadrupole field. The second portion (110b) produces a two-fold astigmatism component that is opposite in sign to two-fold astigmatism components produced by the first portion (110a) and third portion (110c). |
