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 positive or negative refractive power, a third lens with positive or negative refractive power, a fourth lens, a fifth lens with negative refractive power, a sixth lens with positive refractive power, and a seventh lens with negative refractive power, wherein said first lens has an object-side surface being convex in a paraxial region, said third lens has an object-side surface being convex in a paraxial region, said fifth lens is formed in a biconcave shape having an object-side surface and an image-side surface being concave in a paraxial region, and said seventh lens has an image-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,
a second lens with positive or negative refractive power,
a third lens with positive or negative refractive power,
a fourth lens,
a fifth lens with negative refractive power,
a sixth lens with positive refractive power, and
a seventh lens with negative refractive power,
wherein said first lens has an object-side surface being convex in a paraxial region, said third lens has an object-side surface being convex in a paraxial region, said fifth lens is formed in a biconcave shape having an object-side surface and an image-side surface being concave in a paraxial region, and said seventh lens has an image-side surface being concave in a paraxial region, and the following conditional expressions (1), (2), (3), and (8) are satisfied:
13.00< vd 3<34.00 (1)
0.55<( vd 2/ vd 4)×( vd 5/ vd 6)<1.30 (2)
1.50< r 12/( T 5+ D 6)<14.00 (3)
0.80< r 12/ f 6<1.90 (8)
wherein
vd3: an abbe number at d-ray of the third lens,
vd2: an abbe number at d-ray of the second lens,
vd4: an abbe number at d-ray of the fourth lens,
vd5: an abbe number at d-ray of the fifth lens,
vd6: an abbe number at d-ray of the sixth lens,
r12: a paraxial curvature radius of an image-side surface of the sixth lens,
T5: a distance along the optical axis from an image-side surface of the fifth lens to an object-side surface of the sixth lens,
D6: a thickness along the optical axis of the sixth lens, and
f6: a focal length of the sixth lens.
2. The imaging lens according to claim 1 , wherein an image-side surface of said third lens is concave in a paraxial region.
3. The imaging lens according to claim 1 , wherein the following conditional expression (4) is satisfied:
2.50<( D 1/ f 1)×100<16.20 (4)
where
D1: a thickness along the optical axis of the first lens, and
f1: a focal length of the first lens.
4. The imaging lens according to claim 1 , wherein the following conditional expression (5) is satisfied:
−1.75< f 1 /f 7<−0.50 (5)
where
f1: a focal length of the first lens, and
f7: a focal length of the seventh lens.
5. The imaging lens according to claim 1 , wherein the following conditional expression (6) is satisfied:
−4.65< f 3/ f 2<−0.25 (6)
where
f3: a focal length of the third lens, and
f2: a focal length of the second lens.
6. The imaging lens according to claim 1 , wherein the following conditional expression (7) is satisfied:
−2.75< r 9/ f<− 0.20 (7)
where
r9: a paraxial curvature radius of an object-side surface of the fifth lens, and
f: a focal length of the overall optical system of the imaging lens.