Imaging lens
There is provided an imaging lens which satisfies demand of the wide field of view, the low-profileness and the low F-number and has excellent optical performance. 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 the convex surface facing the object side 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 an image side near the optical axis, wherein the second lens has negative refractive power near the optical axis, the third lens has the negative refractive power near the optical axis, the fourth lens has the positive refractive power near the optical axis, and below conditional expressions are satisfied: −3.00<( D 2/ f 2)×100<−0.05 0.25<( T 4/ f )×100<1.00 where D 2 : thickness along the optical axis of the second lens, f2: focal length of the second lens, T 4 : distance along the optical axis from the image-side surface of the fourth lens to the object-side surface of the fifth lens, and f: focal length of the overall optical system of the imaging lens.
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,
a second lens having the convex surface facing the object side 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 an image side near the optical axis, wherein said second lens has negative refractive power near the optical axis, said third lens has the negative refractive power near the optical axis, said fourth lens has the positive refractive power near the optical axis, and below conditional expressions (1), (2), and (7) are satisfied:
−3.00<( D 2/ f 2)×100<−0.05 (1)
0.25<( T 4/ f )×100<1.00 (2)
1<|f3|/f<20 (7)
where
D2: thickness along the optical axis of the second lens,
f2: focal length of the second lens,
f3: focal length of the third 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, and
f: focal length of the overall optical system of the imaging lens.
2. The imaging lens according to claim 1 , wherein an object-side surface of said fifth lens has the convex surface facing the object side near the optical axis.
3. The imaging lens according to claim 1 , wherein an object-side surface of said sixth lens has the convex surface facing the object side near the optical axis, and is formed as an aspheric surface having at least one off-axial pole point.
4. The imaging lens according to claim 1 , wherein a below conditional expression (3) is satisfied:
0.15< vd 5/ vd 6<0.70 (3)
where
vd5: abbe number at d-ray of the fifth lens, and
vd6: abbe number at d-ray of the sixth lens.
5. The imaging lens according to claim 1 , wherein a below conditional expression (5) is satisfied:
0.4<( T 3/ f )×100<14.0 (5)
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.
6. The imaging lens according to claim 1 , wherein a below conditional expression (6) is satisfied:
−77.0< f 2/ f<− 1.4 (6)
where
f2: focal length 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 (8) is satisfied:
0.1< r 1/ r 2<0.6 (8)
where
r1: paraxial curvature radius of the object-side surface of the first lens, and
r2: paraxial curvature radius of the image-side surface of the first lens.
8. The imaging lens according to claim 1 , wherein a below conditional expression (9) is satisfied:
0.5< r 3/ r 4<3.0 (9)
where
r3: paraxial curvature radius of the object-side surface of the second lens, and
r4: paraxial curvature radius of the image-side surface of the second lens.
9. The imaging lens according to claim 1 , wherein a below conditional expression (10) is satisfied:
0.4<| r 2|/ f< 2.6 (10)
where
r2: paraxial curvature radius of the image-side surface of the first lens, and
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 (11) is satisfied:
0.25< r 3/ f< 2.50 (11)
where
r 3 : 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.
11. 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 the convex surface facing the object side near the optical axis,
a third lens,
a fourth lens,
a fifth lens having the convex surface facing the object side near the optical axis, and
a sixth lens having negative refractive power and a concave surface facing the image side near the optical axis, wherein below conditional expressions (2), (3), (4), (7), and (11) are satisfied:
0.25<( T 4/ f )×100<1.00 (2)
0.15< vd 5/ vd 6<0.70 (3)
−0.36< f 1/ f 2<0.00 (4)
1<|f3|f<20 (7)
0.25<r3/f<2.50 (1)
where
T 4 : 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,
vd5: abbe number at d-ray of the fifth lens,
vd6: abbe number at d-ray of the sixth lens,
f1: focal length of the first lens, and
f2: focal length of the second lens.
f3: focal length of the third lens, and
r3: paraxial curvature radius of the object-side surface of the second lens.
12. The imaging lens according to claim 11 , wherein a below conditional expression (1) is satisfied:
−3.00<( D 2/ f 2)×100<−0.05 (1)
where
D2: thickness along the optical axis of the second lens, and
f2: focal length of the second lens.
13. The imaging lens according to claim 11 , wherein a below conditional expression (5) is satisfied:
0.4<( T 3/ f )×100<14.0 (5)
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.
14. The imaging lens according to claim 11 , wherein a below conditional expression (6) is satisfied:
−77.0< f 2/ f<− 1.4 (6)
where
f2: focal length of the second lens, and
f: focal length of the overall optical system of the imaging lens.
15. The imaging lens according to claim 11 , wherein a below conditional expression (8) is satisfied:
0.1< r 1/ r 2<0.6 (8)
where
r1: paraxial curvature radius of the object-side surface of the first lens, and
r2: paraxial curvature radius of the image-side surface of the first lens.
16. The imaging lens according to claim 11 , wherein a below conditional expression (9) is satisfied:
0.5< r 3/ r 4<3.0 (9)
where
r3: paraxial curvature radius of the object-side surface of the second lens, and
r4: paraxial curvature radius of the image-side surface of the second lens.
17. The imaging lens according to claim 11 , wherein a below conditional expression (10) is satisfied:
0.4<| r 2|/ f <2.6 (10)
where
r2: paraxial curvature radius of the image-side surface of the first lens, and
f: focal length of the overall optical system of the imaging lens.