| 摘要 |
PROBLEM TO BE SOLVED: To provide an optical system having a compact size and a small F-number, securing a back focus having an appropriate length, and having high optical performance capable of coping with an increase in the number of pixels in recent years, and an optical apparatus including the optical system.SOLUTION: An optical system substantially comprises, in order from an enlargement side: a first lens L1 having a convex enlargement-side surface and having positive refractive power; a second lens L2 having negative refractive power; a third lens L3 having negative refractive power; a fourth lens L4 having positive refractive power; a fifth lens L5 having positive power; and a sixth lens L6 having positive refractive power. The optical system satisfies the following conditional expressions (1), (2): 0.17<D2/f<0.80...(1), -60<νd1-νd2<-15...(2), where D2 represents a distance on an optical axis between the first lens and the second lens, f represents a focal length of an entire system, νd1 represents an Abbe number of a d-line reference of the first lens, and νd2 represents an Abbe number of a d-line reference of the second lens.SELECTED DRAWING: Figure 1 |
