LARGE APERTURE RATIO INNER FOCUS ULTRA-TELEPHOTOGRAPHIC LENS

摘要

PROBLEM TO BE SOLVED: To provide a large aperture ratio inner focus ultra-telephotographic lens which has excellent optical performance and in which the diameter of a focusing lens group is small by satisfying a specified condition concerning the focal distance of each lens group. ;SOLUTION: A 1st lens group G1 is composed of a front group G11 having positive refractive power and a rear group G12 having positive refractive power of nearly the same degree as the front group G11 in order from an object side. Then, it satisfies conditional expressions; 0.7|f1.f3/(f2.F)|1.3, 0.4|f2.F|/(f1.Φ1)1.0 and 0.7f1F/f1R1.4. In the expressions, f1 shows the focal distance of the 1st lens group G1, f2 shows the focal distance of a 2nd lens group G2 and f3 shows the focal distance of a 3rd lens group G3. Then, f1F shows the focal distance of the front group G11 in the 1st lens group G1, f1R shows the focal distance of the rear group G12 in the 1st lens group G1, F shows the focal distance of an entire lens system and Φ1 shows the effective diameter of a lens surface closest to the object side among the 1st lens group G1.;COPYRIGHT: (C)1999,JPO