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 positive refractive power, a fifth lens, and a sixth lens with negative refractive power, wherein said first 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 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 positive refractive power,
a fifth lens, and
a sixth lens with negative refractive power,
wherein said first lens has an object-side surface being convex in a paraxial region, and said sixth lens has an image-side surface being concave in a paraxial region, and the following conditional expressions (1), (2), (3) and (4) are satisfied:
11.00< vd 3<26.00 (1)
0.10<( r 2/| r 6|)×100<100.00 (2)
1.60<(| r 5/ r 6|)×100 (3)
0.50< r 11/( T 4+ D 5+ T 5)<6.75 (4)
where
vd3: an abbe number at d-ray of the third lens,
r2: a paraxial curvature radius of an image-side surface of the first lens,
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,
r11: a paraxial curvature radius of an object-side surface of the sixth lens,
T4: a distance along the optical axis from an image-side surface of the fourth lens to an object-side surface of the fifth lens,
D5: a thickness along the optical axis of the fifth lens, and
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.
2 . The imaging lens according to claim 1 , wherein an object-side surface of said second lens is convex in a paraxial region.
3 . The imaging lens according to claim 1 , wherein an image-side surface of said second lens is concave in a paraxial region.
4 . The imaging lens according to claim 1 , wherein an image-side surface of said fourth lens is convex in a paraxial region.
5 . The imaging lens according to claim 1 , wherein the following conditional expression (5) is satisfied:
0.05<( r 2/ r 4/| r 6|)×100<7.00 (5)
where
r2: a paraxial curvature radius of an image-side surface of the first lens,
r4: a paraxial curvature radius of an image-side surface of the second 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 (6) is satisfied:
−5.00< r 3/ f 2<−1.00 (6)
where
r3: a paraxial curvature radius of an object-side surface of the second lens, and
f2: a focal length of the second lens.
7 . The imaging lens according to claim 1 , wherein the following conditional expression (7) is satisfied:
3.25< r 3/( T 2/ T 1)<11.50 (7)
where
r3: a paraxial curvature radius of an object-side surface of the second lens,
T2: a distance along the optical axis from an image-side surface of the second lens to an object-side surface of the third lens, and
T1: a distance along the optical axis from an image-side surface of the first lens to an object-side surface of the second lens.