Imaging lens
There is provided an imaging lens with excellent optical characteristics which satisfies demand of a low profile and a low F-number. An imaging lens comprises in order from an object side to an image side, a first lens with positive refractive power having a convex object-side surface in a paraxial region, a second lens with negative refractive power in a paraxial region, a third lens with negative refractive power in a paraxial region, a fourth lens with positive refractive power in a paraxial region, and a fifth lens with negative refractive power having a convex image-side surface in a paraxial region, and predetermined conditional expressions are satisfied.
1. An imaging lens comprising, in order from an object side to an image side:
a first lens with positive refractive power having a convex object-side surface in a paraxial region,
a second lens with negative refractive power in a paraxial region,
a third lens with negative refractive power in a paraxial region,
a fourth lens with positive refractive power in a paraxial region, and
a fifth lens with negative refractive power having a convex image-side surface in a paraxial region, wherein the following conditional expressions (1), (2), (3) and (8) are satisfied:
48.00<ν d 3<70.00 (1)
0.20<| r 2|/ f< 8.00 (2)
−2.30<| r 2|/ r 3/ r 10<−0.45 (3)
0.05< D 3/ T 3<0.25 (8)
where
νd3: an abbe number at d-ray of the third lens,
f: a focal length of an overall optical system of the imaging lens,
r2: a paraxial curvature radius of an image-side surface of the first lens,
r3: a paraxial curvature radius of an object-side surface of the second lens,
r10: a paraxial curvature radius of an image-side surface of the fifth lens,
D3: a thickness along the optical axis of the third lens, and
T3: a distance along the optical axis from an image-side surface of the third lens to an object-side surface of the fourth lens.
2. The imaging lens according to claim 1 , wherein the following conditional expression (4) is satisfied:
−30.00<| r 2|/ r 8<−3.00 (4)
r2: a paraxial curvature radius of an image-side surface of the first lens, and
r8: a paraxial curvature radius of an image-side surface of the fourth lens.
3. The imaging lens according to claim 1 , wherein the following conditional expression (5) is satisfied:
−4.00< r 10/ f<− 0.10 (5)
where
r10: a paraxial curvature radius of an image-side surface of the fifth lens, and
f: a focal length of an overall optical system of the imaging lens.
4. The imaging lens according to claim 1 , wherein the following conditional expression (6) is satisfied:
0.05< r 10/ r 5<0.75 (6)
where
r10: a paraxial curvature radius of an image-side surface of the fifth lens, and
r5: a paraxial curvature radius of an object-side surface of the third lens.
5. The imaging lens according to claim 1 , wherein the following conditional expression (7) is satisfied:
0.70< T 2/ T 1<20.00 (7)
where
T2: a distance along the optical axis from an image-side surface of the second lens to an object-side surface of the third lens, and
T1: a distance along the optical axis from an image-side surface of the first lens to an object-side surface of the second lens.
6. The imaging lens according to claim 1 , wherein the following conditional expression (9) is satisfied:
0.20< f 2/ f 5<1.00 (9)
where
f2: a focal length of the second lens, and
f5: a focal length of the fifth lens.