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 an object-side surface being convex in a paraxial region, a second lens with negative refractive power having an object-side surface being convex in a paraxial region, a third lens with negative refractive power having an image-side surface being concave in a paraxial region, a fourth lens with positive refractive power in a paraxial region, and a fifth lens with negative refractive power having an object-side surface being concave 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 an object-side surface being convex in a paraxial region,
a second lens with negative refractive power having an object-side surface being convex in a paraxial region,
a third lens with negative refractive power having an image-side surface being concave in a paraxial region,
a fourth lens with positive refractive power in a paraxial region, and
a fifth lens with negative refractive power having an object-side surface being concave in a paraxial region,
wherein the imaging lens has only five lenses with refractive power, and
the following conditional expressions (1), (2), (3), and (7) are satisfied:
9.00<ν d 4<29.00 (1)
3.70< r 1×| r 2|/ f< 8.75 (2)
−1.00< r 3/ r 7<−0.25 (3)
1.30<| r 5|/ r 6<3.00 (7)
where
νd4: an abbe number at d-ray of the fourth lens,
r1: a paraxial curvature radius of an object-side surface of the first lens,
r2: a paraxial curvature radius of an image-side surface of the first lens,
f: a focal length of the overall optical system of the imaging lens,
r3: a paraxial curvature radius of an object-side surface of the second lens,
r7: a paraxial curvature radius of an object-side surface of the fourth lens,
r5: a paraxial curvature radius of an object-side surface of the third lens, and
r6: a paraxial curvature radius of an image-side surface of the third lens.
2. The imaging lens according to claim 1 , wherein the following conditional expression (4) is satisfied:
3.25<( D 4/ f 4)×100<9.50 (4)
where
D4: a thickness along the optical axis of the fourth lens, and
f4: a focal length of the fourth lens.
3. The imaging lens according to claim 1 , wherein the following conditional expression (5) is satisfied:
2.30<| r 2|/ f< 7.00 (5)
where
r2: a paraxial curvature radius of an image-side surface of the first lens, and
f: a focal length of the overall optical system of the imaging lens.
4. The imaging lens according to claim 1 , wherein the following conditional expression (6) is satisfied:
−17.00| r 2|/ r 8<−3.50 (6)
where
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.
5. The imaging lens according to claim 1 , wherein the following conditional expression (8) is satisfied:
0.80<| r 5|/ r 6/ r 1<2.20 (8)
where
r5: a paraxial curvature radius of an object-side surface of the third lens,
r6: a paraxial curvature radius of an image-side surface of the third lens, and
r1: a paraxial curvature radius of an object-side surface of the first lens.
6. The imaging lens according to claim 1 , wherein the following conditional expression (9) is satisfied:
1.20< f 4/ f< 30.00 (9)
where
f4: a focal length of the fourth lens, and
f: a focal length of the overall optical system of the imaging lens.