| 摘要 |
PROBLEM TO BE SOLVED: To satisfactorily correct spherical aberration of a luminous flux of which numerical aperture exceeds 1 by providing an immersion system objective lens with a front group of an approximately afocal system and a rear group having a positive refraction power and satisfying specific conditions. SOLUTION: This immersion system objective lens has a front group GF of an approximately afocal system and a rear group GR having a positive refraction power, and satisfy three conditions by the condition formulae, 1.5ϕ18<R18/ϕ18<10ϕ18, d4>d2, and|R11|<R10. In the formulae,ϕ18 expresses an effective diameter of the lens surface on a specimen surface side of a positive lens component L9 in the rear group GR, R18 expresses a radius of curvature of the lens surface of the specimen surface side of the positive lens component L9 in the rear group GR, and d2 expresses the length between a positive lens component L1 in the front group GF and a negative lens component L2. The d4 expresses the length between a negative lens component L2 in the front group GF and a positive lens component L3, and R10 expresses a radius of curvature of the specimen surface side of a positive lens component L5 in the rear Group GR, and R11 expresses a radius of curvature of the lens surface on the side of the positive lens component L5 of a negative component L6 in the rear grope GP.
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