| 摘要 |
PROBLEM TO BE SOLVED: To provide a rear attachment lens that has small various aberration change when attached to the image side of a main lens system and shifting the focal length of the entire system to a longer one, that is, has especially small color aberration, and maintains high optical performance as the entire system. SOLUTION: The rear attachment lens is attachable to or detachable from the image side of the main lens system and changes its focal length longer than the focal length of the main lens system itself. The rear attachment lens has a refractive optical element GNL formed from resin, and has the Abbe's numberν<SB>G</SB>of the material of the refractive optical element GNL, a partial dispersion ratioθgF<SB>G</SB>, an abnormal partial dispersion ratioΔθgF<SB>G</SB>, a refractive powerϕ<SB>G</SB>relative to a line d obtained when the two refractive faces of the refractive optical element GNL face air, and the enlarging magnificationβ<SB>G</SB>of the rear attachment lens, all of which are appropriately set. COPYRIGHT: (C)2010,JPO&INPIT
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