| 摘要 |
PROBLEM TO BE SOLVED: To improve chromatic difference of magnification and other aberration even in the case of applying a lens to a CCD image pickup element whose number of pixels is large while securing compact constitution such as five lenses by setting space between a 1st lens and a 2nd lens constituting a front group to a specified long distance and making the surface of the 2nd lens on an object side a surface having large curvature. SOLUTION: This lens is constituted of the front group consisting of the 1st lens L1 being a negative meniscus whose convex surface faces to the object side and whose surface on the object side is made aspherical and the 2nd lens L2 consisting of a biconvex lens whose surface having the large curvature faces to the object side, and a rear group consisting of a 3rd lens L3 consisting of a biconcave lens and two biconvex lenses L4 and L5. When it is assumed that a distance from the surface of the lens L1 on the object side to the surface of the lens L2 on an image side is (d), the focal distance of an entire lens system is (f), the mean values of the refractive index and the Abbe number of two biconvex lenses L4 and L5 are nA andνA, 1.0<d/f<2.0 (1), nA>1.76 (2) andνA>45.0 (3) are satisfied.
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