| CPC G02B 13/0045 (2013.01) [G02B 9/60 (2013.01)] | 6 Claims |
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1. An imaging lens for forming an image of an object on an image sensor comprising, in order from an object side to an image side,
a first lens with positive refractive power,
a second lens with negative refractive power,
a third lens,
a fourth lens with positive refractive power, and
a fifth lens with negative refractive power,
wherein an image-side surface of said fourth lens is convex in a paraxial region, an object-side surface of said fifth lens is an aspheric surface having at least one inflection point, and the following conditional expressions (1) to (4) and (10′) are satisfied:
f/Dep<2.0 (1)
1.2<T3/T2<1.8 (2)
15<vd3<35 (3)
−1.0<R5f/R5r<−0.3 (4)
0.318<=D12/D23<0.6 (10′)
where
f: a focal length of an overall optical system of the imaging lens,
Dep: an entrance pupil diameter of the imaging lens,
T2: a thickness along an optical axis X of the second lens L2,
T3: a thickness along an optical axis X of the third lens L3,
vd3: an abbe number at d-ray of the third lens L3,
R5f: a curvature radius of an object-side surface of the fifth lens L5,
R5r: a curvature radius of an image-side surface of the fifth lens L5,
D12: a distance along the optical axis between the first lens and the second lens, and
D23: a distance along the optical axis between the second lens and the third lens.
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