| 摘要 |
PURPOSE:To drastically improve spherical aberration without deterioration of chromatic aberration by forming the side of lower magnetic pole piece or the periphery thereof of the upper magnetic pole piece as the magnetic saturating part where is saturated with a weak maganetization energy. CONSTITUTION:The side of lower magnetic pole piece 1'a of the upper magnetic pole piece 1' is formed thicker than the other part and thereby said edge 1'a is considered as the magnetic saturating part where is magnetically saturated with a weak magnetication energy. Moreover, the distance l from the edge of such magnetic saturating part 1'a to the upper surface of the lower magnetic pole piece 2 is set longer than the length of clearance of conventional objective. Thereby, the length between the principal plane of lens and a sample can be set as short as possible and as a result chromatic aberration coefficient can be kept good and moreover spherical aberration coefficient can be reduced. Accordingly, remarkably high performance lens characteristic can be obtained by improving the resolution. |
