| 摘要 |
PROBLEM TO BE SOLVED: To extremely inexpensively provide an image pickup lens having a viewing angle of >=65 deg., an F-number of about 2.8 and excellently corrected aberration. SOLUTION: A front lens group FG is constituted of a first lens L1 being a concave lens whose strongly concave surface faces an image side and a second lens L2 being a convex lens in this order from an object side. A rear lens group RG is constituted of a cemented lens consisting of the third lens L3 being a convex lens, a fourth lens L4 being a concave lens and a fifth lens L5 being a convex lens with a diaphragm IR interposed between the front lens group and itself. At least one surface of the fifth lens L5 is constituted of an aspherical surface. When (f) represents the focal distance of an entire lens system, f2 represents the focal distance of the second lens, n1, n3 and n4 respectively represent the refractive indexes of the first, third and fourth lenses and r6, r7 and r8 represent the radiuses of curvature of surfaces, conditions of 2.2<f2/f<3, 1.58<n1<1.73, 0.04<n3-n4<0.15, 0.8<|r6/r7|<1.25 and 0.7<r8/f<0.9 are satisfied.
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