| 摘要 |
PROBLEM TO BE SOLVED: To provide an aberration correcting device capable of correcting spherical aberration and axial chromatic aberration if necessary with a multipole for correction. SOLUTION: In a 2πtype Wien filter comprising 12 poles, a condition ¾b<SB>3</SB>-5m<SP>2</SP>/144¾<ε<SB>4</SB>, ¾e<SB>4</SB>-b<SB>4</SB>-29m<SP>2</SP>/1152¾<ε<SB>6</SB>which makes a sectional shape of a charged-particle current in an emission window nearly circular and a condition m< 6-2√6 which makes spherical aberration and chromatic aberration negative are applied under a condition ¾e<SB>2</SB>+(m+2)/8¾<ε<SB>1</SB>, ¾b<SB>2</SB>+m/8¾<ε<SB>2</SB>and ¾e<SB>3</SB>-b<SB>3</SB>-m/16¾<ε<SB>3</SB>which makes secondary geometric aberration small, it can be used for correcting spherical aberration and chromatic aberration while suppressing increment in off-axis aberration by a condition ¾m¾<ε<SB>7</SB>. COPYRIGHT: (C)2006,JPO&NCIPI
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