Imaging lens
There is provided an imaging lens with excellent optical characteristics which satisfies demand of wide field of view and low F-number. An imaging lens comprising in order from an object side to an image side, a first lens with negative refractive power in a paraxial region, a second lens with positive refractive power having a convex object-side surface in a paraxial region, a third lens with positive refractive power in a paraxial region, a fourth lens, a fifth lens having a concave object-side surface in a paraxial region, and a sixth lens having a concave 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 negative refractive power in a paraxial region,
a second lens with positive refractive power having a convex object-side surface in a paraxial region,
a third lens with positive refractive power in a paraxial region, a fourth lens,
a fifth lens having a concave object-side surface in a paraxial region, and
a sixth lens having a concave image-side surface in a paraxial region, wherein the following conditional expressions (1), (2) and (3) are satisfied:
0.20< vd 2/ vd 6<0.60 (1)
12.50 |f 6 |/D 6<90.00 (2)
2.50<( r 12 /r 2)/ D 6<7.00 (3)
where
vd2: an abbe number at d-ray of the second lens,
vd6: an abbe number at d-ray of the sixth lens,
f6: a focal length of the sixth lens,
D 6 : a thickness along the optical axis of the sixth lens,
r12: a paraxial curvature radius of an image-side surface of the sixth lens,
r2: a paraxial curvature radius of an image-side surface of the first lens, and
D 6 : a thickness along the optical axis of the sixth lens.
2. The imaging lens according to claim 1 , wherein an image-side surface of said third lens is convex in the paraxial region.
3. The imaging lens according to claim 1 , wherein the following conditional expression (4) is satisfied:
5.25| f 6|/ f< 50.00 (4)
where
f6: a focal length of the sixth 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 (5) is satisfied:
−45.00<| f 6|/ f 1<−5.00 (5)
where
f6: a focal length of the sixth 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:
−0.95 <r 2 /r 6<−0.40 (6)
where
r2: a paraxial curvature radius of an image-side surface of the first lens, and
r6: a paraxial curvature radius of an image-side surface of the third lens.
6. The imaging lens according to claim 1 , wherein the following conditional expression (7) is satisfied:
−1.00 <r 6 /r 12 <−0.25 (7)
where
r6: a paraxial curvature radius of an image-side surface of the third lens, and
r12: a paraxial curvature radius of an image-side surface of the sixth lens.
7. The imaging lens according to claim 1 , wherein the following conditional expression (8) is satisfied:
0.75 <r 12 /f< 2.00 (8)
where
r12: a paraxial curvature radius of an image-side surface of the sixth lens, and
f: a focal length of the overall optical system of the imaging lens.