CPC G02B 13/0045 (2013.01) [G02B 9/60 (2013.01)] | 18 Claims |
1. An imaging lens comprising in order from an object side to an image side,
a first lens having positive refractive power and a convex surface facing the object side near the optical axis,
a second lens having negative refractive power near the optical axis,
a third lens having the positive refractive power near the optical axis,
a fourth lens, and
a fifth lens having the negative refractive power and a concave surface facing the image side near the optical axis, wherein the image-side surface of said fifth lens is formed as an aspheric surface having at least one off-axial pole point, and below conditional expressions (1), (2), (3), and (4) are satisfied:
0.15<vd4/vd5<0.55 (1)
0.7<T1/T2<3.0 (2)
1.1<|r7|/r8 (3)
6<(T1/f)x100<18 (4)
where
vd4: abbe number at d-ray of the fourth lens,
vd5: abbe number at d-ray of the fifth lens,
T1: distance along the optical axis from the image-side surface of the first lens to the object-side surface of the second lens,
T2: distance along the optical axis from the image-side surface of the second lens to the object-side surface of the third lens,
r7: paraxial curvature radius of the object-side surface of the fourth lens,
r8: paraxial curvature radius of the image-side surface of the fourth lens,
f; focal length of the overall optical system of the imaging lens.
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