Imaging lens
There is provided an imaging lens with excellent optical characteristics which satisfies demand of low profile and low F-number. 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 in a paraxial region, a third lens with negative refractive power having an object-side surface being convex in a paraxial region, a fourth lens having an object-side surface being convex in a paraxial region, a fifth lens with negative refractive power in a paraxial region, and a sixth lens with positive refractive power having an image-side surface being convex 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 in a paraxial region;
a third lens with negative refractive power having an object-side surface being convex in a paraxial region;
a fourth lens having an object-side surface being convex in a paraxial region;
a fifth lens with negative refractive power in a paraxial region; and
a sixth lens with positive refractive power having an image-side surface being convex in a paraxial region, wherein the following conditional expressions (1), (2), (3) and (17) are satisfied:
11.00< νd 2<27.00 (1)
−1.55< f 3/ f<− 0.20 (2)
0.25< r 3/ f< 5.00 (3)
−8.50< r 12/ D 6<−1.50 (17)
where
νd2: an abbe number at d-ray of the second lens, f3: a focal length of the third 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;
r12: a paraxial curvature radius of an image-side surface of the sixth lens, and
D6: 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 first lens is convex in a paraxial region.
3. The imaging lens according to claim 1 , wherein an object-side surface of said fifth lens is concave in a paraxial region.
4. The imaging lens according to claim 1 , wherein the following conditional expression (4) is satisfied:
9.00<( D 6 /f 6)×100 (4)
where
D6: a thickness along the optical axis of the sixth lens, and f6: a focal length of the sixth lens.
5. The imaging lens according to claim 1 , wherein the following conditional expression (5) is satisfied:
0.50 <f 6 /f 1<2.60 (5)
where
f6: a focal length of the sixth lens, and f1: a focal length of the first lens.
6. The imaging lens according to claim 1 , wherein the following conditional expression (6) is satisfied:
1.00 <r 2 /r 12<7.50 (6)
where
r2: a paraxial curvature radius of an image-side surface of the first 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 (7) is satisfied:
0.10 <r 8 /f< 0.55 (7)
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.