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 an optical axis, a second lens having negative refractive power near the optical axis, a third lens, a fourth lens, a fifth lens having a concave surface facing the image side near the optical axis, and a sixth lens having a concave surface facing the image side near the optical axis, wherein an image-side surface of the sixth lens is formed as an aspheric surface having at least one off-axial pole point, the fifth lens has positive refractive power near the optical axis, an object-side surface of the sixth lens has a 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 an optical axis and,
a second lens having negative refractive power near the optical axis,
a third lens,
a fourth lens,
a fifth lens having a concave surface facing the image side near the optical axis, and
a sixth lens having a concave surface facing the image side near the optical axis, wherein an image-side surface of said sixth lens is formed as an aspheric surface having at least one off-axial pole point, said fifth lens has positive refractive power near the optical axis, an object-side surface of said sixth lens has a convex surface facing the object side near the optical axis, and below conditional expressions ( 1 ) and ( 2 ) are satisfied:
5.0<( D 3/| f 3|)×100<14.5 (1)
0.02< T 1/ T 2<0.12 (2)
where
D3: thickness along the optical axis of the third lens,
f3: focal length of the third 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.
2. 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 an optical axis,
a second lens having negative refractive power near the optical axis,
a third lens,
a fourth lens,
a fifth lens having a concave surface facing the image side near the optical axis, and
a sixth lens having a concave surface facing the image side near the optical axis, wherein an image-side surface of said sixth lens is formed as an aspheric surface having at least one off-axial pole point, an image-side surface of said third lens has a convex surface facing the image side near the optical axis, said fourth lens has negative refractive power near the optical axis, and below conditional expressions (2), (3) and (4) are satisfied:
0.02< T 1/ T 2<0.12 (2)
11.5<( T 2/ f )×100 (3)
−8.7< f 2/ f<− 2.0 (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,
T2: distance along the optical axis from the image-side surface of the second lens to the object-side surface of the third lens,
f: focal length of the overall optical system of the imaging lens,
f2: focal length of the second lens.
3. The imaging lens according to claim 1 , wherein composite focal length of said fifth lens and said sixth lens is positive near the optical axis.
4. The imaging lens according to claim 1 , wherein an image-side surface of said fourth lens has a convex surface facing the image side near the optical axis.
5. The imaging lens according to claim 2 , wherein an object-side surface of said sixth lens has a convex surface facing the object side near the optical axis.
6. The imaging lens according to claim 1 , wherein a below conditional expression (5) is satisfied:
0.5< vd 5/ vd 6<1.5 (5)
where
vd5: abbe number at d-ray of the fifth lens,
vd6: abbe number at d-ray of the sixth lens.
7. The imaging lens according to claim 2 , wherein a below conditional expression (6) is satisfied:
−3.60<( D 2/ f 2)×100<−0.55 (6)
where
D2: thickness along the optical axis of the second lens,
f2: focal length of the second lens.
8. The imaging lens according to claim 2 , wherein a below conditional expression (1) is satisfied:
5.0<( D 3/| f 3|)×100<14.5 (1)
where
D3: thickness along the optical axis of the third lens,
f3: focal length of the third lens.
9. The imaging lens according to claim 1 , wherein a below conditional expression (7) is satisfied:
0.15<( T 4/ f )×100<1.40 (7)
where
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.
10. The imaging lens according to claim 1 , wherein a below conditional expression (8) is satisfied:
−3.20< f 4/ f<− 0.65 (8)
where
f4: focal length of the fourth lens,
f: 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:
0.6< f 5/ f< 2.2 (9)
where
f5: focal length of the fifth lens,
f: focal length of the overall optical system of the imaging lens.
12. The imaging lens according to claim 3 , wherein a below conditional expression (10) is satisfied:
0.45< f 56/ f< 4.25 (10)
where
f56: composite focal length of the fifth lens and the sixth lens,
f: focal length of the overall optical system of the imaging lens.
13. The imaging lens according to claim 1 , wherein a below conditional expression (11) is satisfied:
−6.0< f 2/ f 5<−1.6 (11)
where
f2: focal length of the second lens,
f5: focal length of the fifth lens.
14. The imaging lens according to claim 1 , wherein a below conditional expression (12) is satisfied:
0.25<| r 7|/ f< 0.85 (12)
where
r7: paraxial curvature radius of the object-side surface of the fourth lens,
f: focal length of the overall optical system of the imaging lens.
15. The imaging lens according to claim 2 , wherein composite focal length of said fifth lens and said sixth lens is positive near the optical axis.
16. The imaging lens according to claim 2 , wherein an image-side surface of said fourth lens has a convex surface facing the image side near the optical axis.
17. The imaging lens according to claim 2 , wherein a below conditional expression (5) is satisfied:
0.5< vd 5/ vd 6<1.5 (5)
where
vd5: abbe number at d-ray of the fifth lens,
vd6: abbe number at d-ray of the sixth lens.
18. The imaging lens according to claim 2 , wherein a below conditional expression (7) is satisfied:
0.15<( T 4/ f )×100<1.40 (7)
where
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.
19. The imaging lens according to claim 15 , wherein a below conditional expression (10) is satisfied:
0.45< f 56/ f< 4.25 (10)
where
f56: composite focal length of the fifth lens and the sixth lens,
f: focal length of the overall optical system of the imaging lens.
20. The imaging lens according to claim 2 , wherein a below conditional expression (11) is satisfied:
−6.0< f 2/ f 5<−1.6 (11)
where
f2: focal length of the second lens,
f5: focal length of the fifth lens.