| 摘要 |
PURPOSE:To obtain an image capable of being highly resolved, by reducing a coefficient of shperical aberration of the objective lens. CONSTITUTION:Two auxiliary magnetic pole pieces 19, 20 are installed to an upper magnetic pole piece 3 by using spacers 13, 21 and binding members 15, 22. A single composite magnetic field can be obtained by three gaps among the magnetic poles. A total sum G2 of gaps among each neighboring magneitc pole pieces existing in an upper half region between upper and lower magnetic pole pieces 3, 4 is arranged less than 1.5 times the total sum G1 of gaps among each neighboring magnetic pole pieces existing in a lower half region between the upper and lower magnetic pole pieces 3, 4. |
