Imaging lens
There is provided an imaging lens with high-resolution which satisfies demand of the wide field of view, the low-profileness and the low F-number, and excellently corrects aberrations. An imaging lens comprises in order from an object side to an image side, a first lens having a convex surface facing the object side near an optical axis, a second lens, a third lens having negative refractive power near the optical axis, a fourth lens, a fifth lens, a sixth lens, a seventh lens, and an eighth lens having a concave surface facing the image side and the negative refractive power near the optical axis, wherein an image-side surface of said eighth lens is formed as an aspheric surface having at least one pole point in a position off the optical axis, said sixth lens has positive refractive power near the optical axis, an object-side surface of said seventh lens is a convex surface facing the object side near the optical axis, and a below conditional expression (1) is satisfied: 0.15<ν d 7/ν d 8<0.55 where νd7: an abbe number at d-ray of the seventh lens, νd8: an abbe number at d-ray of the eighth lens.
1. An imaging lens comprising, in order from an object side to an image side,
a first lens having a convex surface facing the object side near an optical axis,
a second lens having positive refractive power near the optical axis,
a third lens having negative refractive power near the optical axis,
a fourth lens,
a fifth lens having positive refractive power near the optical axis,
a sixth lens having positive refractive power near the optical axis,
a seventh lens having positive refractive power near the optical axis, and
an eighth lens having negative refractive power near the optical axis and having a concave surface facing the image side near the optical axis,
wherein
an image-side surface of said eighth lens is formed as an aspheric surface having at least one pole point in a position off the optical axis, and a below conditional expression (3) is satisfied:
3.00<( D 7/TTL)×100<8.70 (3)
where
D7: a thickness along the optical axis of the seventh lens, and
TTL: a total track length.
2. The imaging lens according to claim 1 , wherein an image-side surface of said sixth lens is a convex surface facing the image side near the optical axis.
3. The imaging lens according to claim 1 , wherein an image-side surface of said seventh lens is a concave surface facing the image side near the optical axis.
4. The imaging lens according to claim 1 , wherein a below conditional expression (1) is satisfied:
0.15<ν d 7/ν d 8<0.55 (1)
where
νd7: an abbe number at d-ray of the seventh lens, and
νd8: an abbe number at d-ray of the eighth lens.
5. The imaging lens according to claim 1 , wherein a below conditional expression (2) is satisfied:
0.50<( D 1/| f 1|)×100<13.00 (2)
where
D1: a thickness along the optical axis of the first lens, and
f1: a focal length of the first lens.
6. The imaging lens according to claim 1 , wherein a below conditional expression (4) is satisfied:
0.30< D 4/ D 8<1.20 (4)
where
D4: a thickness along the optical axis of the fourth lens, and
D8: a thickness along the optical axis of the eighth lens.
7. The imaging lens according to claim 1 , wherein a below conditional expression (5) is satisfied:
0.40< D 7/ D 8<1.40 (5)
where
D7: the thickness along the optical axis of the seventh lens, and
D8: the thickness along the optical axis of the eighth lens.
8. The imaging lens according to claim 1 , wherein a below conditional expression (6) is satisfied:
0.30< f 6/ f< 4.50 (6)
where
f6: a focal length of the sixth lens, and
f: a focal length of the overall optical system of the imaging lens.
9. The imaging lens according to claim 1 , wherein a below conditional expression (7) is satisfied:
1.40<| f 7|/ f (7)
where
f7: a focal length of the seventh lens, and
f: the focal length of the overall optical system of the imaging lens.
10. The imaging lens according to claim 1 , wherein a below conditional expression (8) is satisfied:
−1.90< f 8/ f<− 0.60 (8)
where
f8: a focal length of the eighth lens, and
f: the focal length of the overall optical system of the imaging lens.
11. The imaging lens according to claim 1 , wherein a below conditional expression (9) is satisfied:
0.70< r 4/ f< 2.70 (9)
where
r4: paraxial curvature radius of the image-side surface of the second lens, and
f: the focal length of the overall optical system of the imaging lens.
12. The imaging lens according to claim 1 , wherein a below conditional expression (10) is satisfied:
−3.00< r 12/ f<− 0.20 (10)
where
r12: paraxial curvature radius of the image-side surface of the sixth lens, and
f: the focal length of the overall optical system of the imaging lens.
13. An imaging lens comprising, in order from an object side to an image side,
a first lens having a convex surface facing the object side near an optical axis,
a second lens having positive refractive power near the optical axis,
a third lens having negative refractive power near the optical axis,
a fourth lens,
a fifth lens having positive refractive power near the optical axis,
a sixth lens having positive refractive power near the optical axis,
a seventh lens having positive refractive power near the optical axis, and
an eighth lens having negative refractive power near the optical axis and having a concave surface facing the image side near the optical axis,
wherein
an image-side surface of said eighth lens is formed as an aspheric surface having at least one pole point in a position off the optical axis, and a below conditional expression (5) is satisfied:
0.40< D 7/ D 8<1.40 (5)
where
D7: the thickness along the optical axis of the seventh lens, and
D8: the thickness along the optical axis of the eighth lens.
14. An imaging lens comprising, in order from an object side to an image side,
a first lens having a convex surface facing the object side near an optical axis,
a second lens having positive refractive power near the optical axis,
a third lens having negative refractive power near the optical axis,
a fourth lens,
a fifth lens having positive refractive power near the optical axis,
a sixth lens having positive refractive power near the optical axis,
a seventh lens having positive refractive power near the optical axis, and
an eighth lens having negative refractive power near the optical axis and having a concave surface facing the image side near the optical axis,
wherein
an image-side surface of said eighth lens is formed as an aspheric surface having at least one pole point in a position off the optical axis, and a below conditional expression (6) is satisfied:
0.30< f 6/ f< 4.50 (6)
where
f6: a focal length of the sixth lens, and
f: a focal length of the overall optical system of the imaging lens.