| 摘要 |
PROBLEM TO BE SOLVED: To materialize a lens system having excellent manufacturing optimization while reduction in the full length is attained and a high imaging performance is maintained using an aspherical surface. SOLUTION: The imaging lens includes a positive first lens L1 in which an object side face is a convex near the optical axis, a negative second lens L2 in which an image side face is a concave near the optical axis, a third lens L3 having negative power near the optical axis, and a fourth lens L4 in which the two faces are aspherical and in which the image side face is a concave near the optical axis and a convex in the periphery. The imaging lens also satisfies the following conditional expressions, where f is the whole focal distance, f3 is the focal distance of the third lens L3, D4 is a distance between the second lens L2 and the third lens L3 on the optical axis, DM3 is the maximum lens thickness of the third lens L3, and D5 is the center thickness of the third lens L3. (1) is expressed as -1.5≤f/f3≤-0.005, (2) as 0.07≤D4/f≤0.3, and (3) as 1.0≤DM3/D5≤1.5. COPYRIGHT: (C)2009,JPO&INPIT
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