| 摘要 |
An imaging lens comprises, in order from an object side: a first lens having a positive refractive power; a second lens having a negative refractive power whose concave surface faces to the object; and a third lens having a positive refractive power and having a meniscus form that has a convex surface, facing to the object, in a portion at and around an optical axis of the imaging lens; wherein the first, second and third lenses have at least one aspheric surface, and wherein the imaging lens satisfies conditional expressions given below: <?in-line-formulae description="In-line Formulae" end="lead"?>0.7<f1/f<1.3 (1)<?in-line-formulae description="In-line Formulae" end="tail"?> <?in-line-formulae description="In-line Formulae" end="lead"?>0.2<D2/f<0.6 (2)<?in-line-formulae description="In-line Formulae" end="tail"?> <?in-line-formulae description="In-line Formulae" end="lead"?>0.3<|f2/f|<0.8 (3)<?in-line-formulae description="In-line Formulae" end="tail"?> <?in-line-formulae description="In-line Formulae" end="lead"?>0.5<f3/f<0.8 (4)<?in-line-formulae description="In-line Formulae" end="tail"?> where f: a focal length of an overall system, f 1 : a focal length of the first lens, f 2 : a focal length of the second lens, f 3 : a focal length of the third lens, and D 2 : a spacing, on the optical axis, between the first lens and the second lens.
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