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, a second lens with negative refractive power, a third lens with positive or negative refractive power, a fourth lens with negative refractive power, a fifth lens with positive refractive power, and a sixth lens with negative refractive power, wherein said first lens is formed in a meniscus shape having an object-side surface being convex in a paraxial region, said second lens has an object-side surface being convex in a paraxial region, said sixth lens has an image-side surface being concave in a paraxial region, and the 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,
a second lens with negative refractive power,
a third lens with positive or negative refractive power,
a fourth lens with negative refractive power,
a fifth lens with positive refractive power, and
a sixth lens with negative refractive power,
wherein said first lens is formed in a meniscus shape having an object-side surface being convex in a paraxial region, said second lens has an object-side surface being convex in a paraxial region, said sixth lens has an image-side surface being concave in a paraxial region, and the following conditional expressions (1), (2), (3), and (7) are satisfied:
f 4/ f← 13.00 (1)
0.10<( r 6/| f 3|)×100<55.00 (2)
7.50< r 7/ T 3<20.00 (3)
| r 9|/ r 10←8.40 (7)
where
f4: a focal length of the fourth lens,
f: a focal length of the overall optical system of the imaging lens,
r6: a paraxial curvature radius of an image-side surface of the third lens,
f3: a focal length of the third lens,
r7: a paraxial curvature radius of an object-side surface of the fourth lens, and
T3: a distance along an optical axis from an image-side surface of the third lens to an object-side surface of the fourth lens,
r9: a paraxial curvature radius of an object-side surface of the fifth lens, and
r10: a paraxial curvature radius of an image-side surface of the fifth lens.
2. The imaging lens according to claim 1 , wherein an object-side surface of said sixth lens is concave in a paraxial region.
3. The imaging lens according to claim 1 , wherein the following conditional expression (4) is satisfied:
33.00< vd 3<79.00 (4)
where
vd3: an abbe number at d-ray of the third lens.
4. The imaging lens according to claim 1 , wherein the following conditional expression (5) is satisfied:
0.50< r 2/ f 1<1.50 (5)
where
r2: a paraxial curvature radius of an image-side surface of the first lens, and
f1: a focal length of the first lens.
5. The imaging lens according to claim 1 , wherein the following conditional expression (6) is satisfied:
0.20< r 3/ r 4<2.00 (6)
where
r3: a paraxial curvature radius of an object-side surface of the second lens, and
r4: a paraxial curvature radius of an image-side surface of the second lens.
6. The imaging lens according to claim 1 , wherein the following conditional expression (8) is satisfied:
0.20< r 8/ f< 1.20 (8)
where
r8: a paraxial curvature radius of an image-side surface of the fourth lens, and
f: a focal length of the overall optical system of the imaging lens.