Imaging lens
There is provided an imaging lens with high resolution which satisfies in well balance the low-profileness and the low F-number and properly corrects aberrations. An imaging lens comprises a first lens having positive refractive power, a second lens having the positive refractive power, a third lens, a fourth lens, a fifth lens being a double-sided aspheric lens, and a sixth lens being double-sided aspheric lens and having a concave surface facing the image side near the optical axis, wherein the image-side surface of the sixth lens is an aspheric surface changing to the convex surface at a peripheral area.
1. An imaging lens comprising in order from an object side to an image side,
a first lens having positive refractive power,
a second lens,
a third lens,
a fourth lens,
a fifth lens being a double-sided aspheric lens and has plane surfaces on both sides near an optical axis, and
a sixth lens being a double-sided aspheric lens and having a concave surface facing the image side near the optical axis, wherein an image-side surface of said sixth lens is an aspheric surface changing to the convex surface at a peripheral area,
wherein below a conditional expression (1) is satisfied:
1.5< vd 4/ vd 5<3.6 (1)
where
vd4: abbe number at d-ray of a fourth lens, and
vd5: abbe number at d-ray of a fifth lens.
2. The imaging lens according to claim 1 , wherein a second lens having the positive refractive power.
3. The imaging lens according to claim 1 , wherein below a conditional expression (2) is satisfied:
0.30<( T 3/ TTL )×100<0.85 (2)
where
T3: distance along an optical axis from an image-side surface of the third lens to an object-side surface of the fourth lens, and
TTL: distance along an optical axis from an object-side surface of the first lens to an image plane.
4. The imaging lens according to claim 1 , wherein a below conditional expression (3) is satisfied:
0.5< vd 1/( vd 2+ vd 3)<1.0
where
vd1: abbe number at d-ray of a first lens,
vd2: abbe number at d-ray of a second lens, and
vd3: abbe number at d-ray of a third lens.
5. The imaging lens according to claim 1 , wherein said second lens has a biconvex shape near the optical axis.
6. The imaging lens according to claim 1 , wherein said second lens has a meniscus shape having a concave surface facing the object side near the optical axis.
7. The imaging lens according to claim 1 , wherein said fourth lens has a biconvex shape near the optical axis.
8. The imaging lens according to claim 1 , wherein said fourth lens has a meniscus shape having a concave surface facing the object side near the optical axis.
9. The imaging lens according to claim 1 , wherein a below conditional expression (4) is satisfied:
1.35< f 1 /f< 3.30 (4)
where
f1: focal length of the first lens, and
f: focal length of the overall optical system.
10. The imaging lens according to claim 1 , wherein a below conditional expression (5) is satisfied:
0.8< f 2/ f< 3.4 (5)
where
f2: focal length of the second lens, and
f: focal length of the overall optical system.
11. The imaging lens according to claim 1 , wherein a below conditional expression (6) is satisfied:
−1.70< f 3/ f<− 0.65 (6)
where
f3: focal length of the third lens, and
f: focal length of the overall optical system.
12. The imaging lens according to claim 1 , wherein a below conditional expression (7) is satisfied:
0.65< f 4/ f< 2.10 (7)
where
f4: focal length of the fourth lens, and
f: focal length of the overall optical system.
13. The imaging lens according to claim 1 , wherein a below conditional expression (8) is satisfied:
1.9< |f 6 |/f (8)
where
f6: focal length of the sixth lens, and
f: focal length of the overall optical system.
14. The imaging lens according to claim 1 , wherein a below conditional expression (9) is satisfied:
0.1< D 6/Σ D< 0.3 (9)
where
D6: thickness on the optical axis of the sixth lens, and
ΣD: total sum of thickness on the optical axis of the first lens, the second lens, the third lens, the fourth lens, the fifth lens and the sixth lens.
15. The imaging lens according to claim 1 , wherein a below conditional expression (10) is satisfied:
0.7<Σ( L 1 F - L 6 R )/ f< 1.6 (10)
where
Σ(L1F-L6R): distance along the optical axis from the object-side surface of the first lens to the image-side surface of the sixth lens, and
f: focal length of the overall optical system.
16. The imaging lens according to claim 1 , wherein a below conditional expression (11) is satisfied:
0.1< r 5/ r 6<0.7 (11)
where
r5: paraxial curvature radius of the object-side surface of the third lens, and
r6: paraxial curvature radius of the image-side surface of the third lens.
17. The imaging lens according to claim 1 , wherein a below conditional expressions (12) and (13) are satisfied:
0.20 <r 11/ f< 0.55 (12)
0.15< r 12/ f< 0.45 (13)
where
r11: paraxial curvature radius of the object-side surface of the sixth lens,
r12: paraxial curvature radius of the image-side surface of the sixth lens, and
f: focal length of the overall optical system.
18. The imaging lens according to claim 1 , wherein a below conditional expression (14) is satisfied:
Fno≤ 2.0 (14)
where
Fno: F-number.
19. The imaging lens according to claim 1 , wherein a below conditional expression (15) is satisfied:
0.6< f 2/ f 4<2.6 (15)
where
f2: focal length of the second lens, and
f4: focal length of the fourth lens.