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 positive refractive power and a convex surface facing the object side near the optical axis, a second lens having negative refractive power near the optical axis, a third lens, a fourth lens, a fifth lens and a sixth lens having negative refractive power and a concave surface facing the image side near the optical axis, wherein the image-side surface of said sixth lens is formed as an aspheric surface having at least one off-axial pole point, the image-side surface of said first lens has the concave surface facing the image side near the optical axis, the image-side surface of said third lens has the concave surface facing the image side near the optical axis, said fifth lens has a biconvex shape having the convex surfaces facing the object side and the image side near the optical axis, the object-side surface of the sixth lens has the convex surface facing the object side near the optical axis, and predetermined conditional expressions are satisfied.
1. An imaging lens comprising in order from an object side to an image side,
a first lens having positive refractive power and a convex surface facing the object side near the optical axis,
a second lens having negative refractive power near the optical axis,
a third lens,
a fourth lens,
a fifth lens and
a sixth lens having negative refractive power and a concave surface facing the image side near the optical axis, wherein the image-side surface of said sixth lens is formed as an aspheric surface having at least one off-axial pole point, the image-side surface of said first lens has the concave surface facing the image side near the optical axis, the image-side surface of said third lens has the concave surface facing the image side near the optical axis, said fifth lens has a biconvex shape having the convex surfaces facing the object side and the image side near the optical axis, the object-side surface of the sixth lens has the convex surface facing the object side near the optical axis, and below conditional expressions (1), (2), and (10) are satisfied:
11< vd 4<36 (1)
2.0<( T 4/ f )×100<7.6 (2)
−2.4< r 9/ r 10<−0.5 (10)
where
vd4: abbe number at d-ray of the fourth lens,
T4: distance along the optical axis from the image-side surface of the fourth lens to the object-side surface of the fifth lens,
f: focal length of the overall optical system of the imaging lens,
r9: paraxial curvature radius of the object-side surface of the fifth lens, and
r10: paraxial curvature radius of the image-side surface of the fifth lens.
2. The imaging lens according to claim 1 , wherein a below conditional expression (6) is satisfied:
3.5<( T 3/ f )×100<11.5 (6)
where
T3: distance along the optical axis from the image-side surface of the third lens to the object-side surface of the fourth lens, and
f: focal length of the overall optical system of the imaging lens.
3. The imaging lens according to claim 1 , wherein a below conditional expression (4) is satisfied:
0.03< T 1/ T 2<0.15 (4)
where
T1: distance along the optical axis from the image-side surface of the first lens to the object-side surface of the second lens, and
T2: distance along the optical axis from the image-side surface of the second lens to the object-side surface of the third lens.
4. The imaging lens according to claim 1 , wherein a below conditional expression (7) is satisfied:
−3.7< f 4/ f<− 0.8 (7)
where
f4: focal length of the fourth lens, and
f: focal length of the overall optical system of the imaging lens.
5. The imaging lens according to claim 1 , wherein a below conditional expression (9) is satisfied:
−0.9< f 1/ f 4<−0.2 (9)
where
f1: focal length of the first lens, and
f4: focal length of the fourth lens.
6. The imaging lens according to claim 1 , wherein a below conditional expression (11) is satisfied:
1.5< r 3/ f< 6.3 (11)
where
r3: paraxial curvature radius of the object-side surface of the second lens, and
f: focal length of the overall optical system of the imaging lens.
7. The imaging lens according to claim 1 , wherein a below conditional expression (5) is satisfied:
0.55<| r 7|/ f< 1.95 (5)
where
r7: paraxial curvature radius of the object-side surface of the fourth lens, and
f: focal length of the overall optical system of the imaging lens.
8. The imaging lens according to claim 1 , wherein a below conditional expression (12) is satisfied:
0.35<| r 9|/ f< 1.50 (12)
where
r9: paraxial curvature radius of the object-side surface of the fifth lens, and
f: focal length of the overall optical system of the imaging lens.
9. An imaging lens comprising in order from an object side to an image side,
a first lens having positive refractive power and a convex surface facing the object side near the optical axis,
a second lens having negative refractive power near the optical axis,
a third lens,
a fourth lens,
a fifth lens having positive refractive power, and
a sixth lens having negative refractive power and a concave surface facing the image side near the optical axis, wherein the image-side surface of said sixth lens is formed as an aspheric surface having at least one off-axial pole point, said third lens has the positive refractive power and the concave surface facing the image side near the optical axis, the object-side surface of said sixth lens has the convex surface facing the object side near the optical axis, and below conditional expressions (3), (4) and (5) are satisfied:
−2.5<( D 2/ f 2)×100<−0.7 (3)
0.03< T 1/ T 2<0.15 (4)
0.55<| r 7|/ f< 1.95 (5)
where
D2: thickness along the optical axis of the second lens,
f2: focal length of the second lens,
T1: distance along the optical axis from the image-side surface of the first lens to the object-side surface of the second lens,
T2: distance along the optical axis from the image-side surface of the second lens to the object-side surface of the third lens,
r7: paraxial curvature radius of the object-side surface of the fourth lens, and
f: focal length of the overall optical system of the imaging lens.
10. The imaging lens according to claim 9 , wherein said fifth lens has the biconvex shape having convex surfaces facing the object side and the image side near the optical axis.
11. The imaging lens according to claim 9 , wherein a below conditional expression (8) is satisfied:
0.3< f 5/ f< 1.2 (8)
where
f5: focal length of the fifth lens, and
f: focal length of the overall optical system of the imaging lens.
12. The imaging lens according to claim 9 , wherein a below conditional expression (7) is satisfied:
−3.7< f 4/ f<− 0.8 (7)
where
f4: focal length of the fourth lens, and
f: focal length of the overall optical system of the imaging lens.
13. The imaging lens according to claim 9 , wherein a below conditional expression (9) is satisfied:
−0.9< f 1/ f 4<−0.2 (9)
where
f1: focal length of the first lens, and
f4: focal length of the fourth lens.
14. The imaging lens according to claim 9 , wherein a below conditional expression (10) is satisfied:
−2.4< r 9/ r 10<−0.5 (10)
where
r9: paraxial curvature radius of the object-side surface of the fifth lens, and
r10: paraxial curvature radius of the image-side surface of the fifth lens.
15. The imaging lens according to claim 9 , wherein a below conditional expression (11) is satisfied:
1.5< r 3/ f< 6.3 (11)
where
r3: paraxial curvature radius of the object-side surface of the second lens, and
f: focal length of the overall optical system of the imaging lens.
16. The imaging lens according to claim 9 , wherein a below conditional expression (12) is satisfied:
0.35<| r 9|/ f< 1.50 (12)
where
r9: paraxial curvature radius of the object-side surface of the fifth lens, and
f: focal length of the overall optical system of the imaging lens.
17. An imaging lens comprising in order from an object side to an image side,
a first lens having positive refractive power and a convex surface facing the object side near the optical axis,
a second lens having negative refractive power near the optical axis,
a third lens,
a fourth lens,
a fifth lens and
a sixth lens having negative refractive power and a concave surface facing the image side near the optical axis, wherein the image-side surface of said sixth lens is formed as an aspheric surface having at least one off-axial pole point, an aperture stop is arranged between said second lens and said third lens, the object-side surface of third lens has the convex surface facing the object side near the optical axis, the image-side surface of said fourth lens has the concave surface facing the image side near the optical axis, and said fifth lens has a biconvex shape having the convex surfaces facing the object side and the image side near the optical axis, and
a below conditional expression (10) is satisfied:
−2.4< r 9/ r 10<−0.5 (10)
where
r9: paraxial curvature radius of the object-side surface of the fifth lens, and
r10: paraxial curvature radius of the image-side surface of the fifth lens.
18. The imaging lens according to claim 17 , wherein a below conditional expression (4) is satisfied:
0.03< T 1/ T 2<0.15 (4)
where
T1: distance along the optical axis from the image-side surface of the first lens to the object-side surface of the second lens, and
T2: distance along the optical axis from the image-side surface of the second lens to the object-side surface of the third lens.