Imaging lens
An imaging lens includes, in order from an object side, a first positive lens having a convex object-side surface, a second negative lens having a concave image-side surface, a third positive double-sided aspheric lens, a fourth positive lens having a convex image-side surface, and a fifth negative double-sided aspheric lens having a concave image-side surface, wherein the fifth lens image-side surface has pole-change points off an optical axis; and conditional expressions below are satisfied: 0.80<ih/ f <1.00 (1) 0.6< TTL /2ih<0.75 (2) 2.3< f 3/ f <10.3 (3) 0.5< f 1/ f 4<1.4 (4) where f denotes focal length of the imaging lens overall optical system, f 1 , f 3 and f 4 denote focal lengths of the first, third and fourth lenses respectively, ih denotes maximum image height, and TTL denotes distance on the optical axis from the first lens object-side surface to the image plane.
1. An imaging lens which forms an image of an object on a solid-state image sensor, in which an F-value is 2.4 or less and elements are arranged in order from an object side to an image side, comprising:
a first lens with positive refractive power having a convex surface on the object side;
a second lens with negative refractive power having a concave surface near an optical axis on the image side;
a third lens with positive refractive power as a double-sided aspheric lens;
a fourth lens with positive refractive power having a convex surface on the image side; and
a fifth lens with negative refractive power as a double-sided aspheric lens having a concave surface on the image side, wherein
the image-side surface of the fifth lens has pole-change points off the optical axis; and
conditional expressions (1), (2), (3), (4) and (10) below are satisfied:
0.80<ih/ f <1.00 (1)
0.6< TTL/ 2ih<0.75 (2)
2.3< f 3/ f< 10.3 (3)
0.5< f 1/ f 4<1.4 (4)
1.75≦( r 3+ r 4)/( r 3− r 4)<3.0 (10)
where
f: focal length of an overall optical system of the imaging lens
f 1 : focal length of the first lens
f 3 : focal length of the third lens
f 4 : focal length of the fourth lens
ih: maximum image height
TTL: distance on the optical axis from the object-side surface of the first lens to an image plane
r 3 : curvature radius of the object-side surface of the second lens
r 4 : curvature radius of the image-side surface of the second lens.
2. The imaging lens according to claim 1 ,
wherein the fourth lens has an aspheric shape in which positive refractive power becomes weaker with increasing distance from the optical axis and changes to negative refractive power in the peripheral portion.
3. The imaging lens according to claim 1 ,
wherein a conditional expression (5) below is satisfied:
0.5< f 1/ f< 1.0 (5)
where
f: focal length of the overall optical system of the imaging lens
f 1 : focal length of the first lens.
4. The imaging lens according to claim 1 ,
wherein a conditional expression (6) below is satisfied:
−1.6< f 2/ f<− 0.6 (6)
where
f: focal length of the overall optical system of the imaging lens
f 2 : focal length of the second lens.
5. The imaging lens according to claim 1 ,
wherein a conditional expression (7) below is satisfied:
25<ν d 1−ν d 2<40 (7)
where
νd 1 : Abbe number of the first lens at d-ray
νd 2 : Abbe number of the second lens at d-ray.
6. The imaging lens according to claim 1 ,
wherein a conditional expression (8) below is satisfied:
−0.9< f 5/ f<− 0.4 (8)
where
f: focal length of the overall optical system of the imaging lens
f 5 : focal length of the fifth lens.
7. The imaging lens according to claim 1 ,
wherein a conditional expression (9) below is satisfied:
−1.4<( r 1+ r 2)/( r 1− r 2)<−0.3 (9)
where
r 1 : curvature radius of the object-side surface of the first lens
r 2 : curvature radius of the image-side surface of the first lens.
8. The imaging lens according to claim 1 ,
wherein a conditional expression (11) below is satisfied:
0.7<( r 7+ r 8)/( r 7− r 8)<1.8 (11)
where
r 7 : curvature radius of the object-side surface of the fourth lens
r 8 : curvature radius of the image-side surface of the fourth lens.
9. The imaging lens according to claim 3 ,
wherein a conditional expression (9) below is satisfied:
−1.4<( r 1+ r 2)/( r 1− r 2)<−0.3 (9)
where
r 1 : curvature radius of the object-side surface of the first lens
r 2 : curvature radius of the image-side surface of the first lens.
10. The imaging lens according to claim 2 ,
wherein a conditional expression (11) below is satisfied:
0.7<( r 7+ r 8)/( r 7− r 8)<1.8 (11)
where
r 7 : curvature radius of the object-side surface of the fourth lens
r 8 : curvature radius of the image-side surface of the fourth lens.
11. An imaging lens which forms an image of an object on a solid-state image sensor, in which an F-value is 2.4 or less and elements are arranged in order from an object side to an image side, comprising:
a first lens with positive refractive power having a convex surface on the object side;
a second lens with negative refractive power having a concave surface near an optical axis on the image side and a convex surface near the optical axis on the object side;
a third lens with positive refractive power as a double-sided aspheric lens;
a fourth lens with positive refractive power having a convex surface on the image side; and
a fifth lens with negative refractive power as a double-sided aspheric lens having a concave surface on the image side,
wherein the image-side surface of the fifth lens has pole-change points off the optical axis; and
conditional expressions (11), (12), and (13) below are satisfied:
0.7<( r 7+ r 8)/( r 7− r 8)<1.8 (11)
0.55<( r 9+ r 10)/( r 9− r 10)<1.25 (12)
0.03< d 2/ f< 0.06 (13)
where
r 7 : curvature radius of the object-side surface of the fourth lens
r 8 : curvature radius of the image-side surface of the fourth lens
r 9 : curvature radius of the object-side surface of the fifth lens
r 10 : curvature radius of the image-side surface of the fifth lens
f: focal length of the overall optical system
d 2 : thickness of the second lens on the optical axis.
12. The imaging lens according to claim 11 ,
wherein a conditional expression (1) below is satisfied:
0.80 <ih/f< 1.00 (1)
where
f: focal length of an overall optical system of the imaging lens
ih: maximum image height.
13. The imaging lens according to claim 11 ,
wherein a conditional expression (2) below is satisfied:
0.6< TTL/ 2ih<0.75 (2)
where
ih: maximum image height
TTL: distance on the optical axis from the object-side surface of the first lens to an image plane.
14. The imaging lens according to claim 11 ,
wherein a conditional expression (3) below is satisfied:
2.3< f 3/ f< 10.3 (3)
where
f: focal length of an overall optical system of the imaging lens
f 3 : focal length of the third lens.
15. The imaging lens according to claim 11 , wherein a conditional expression (4) below is satisfied:
0.5< f 1/ f 4<1.4 (4)
where
f 1 : focal length of the first lens
f 4 : focal length of the fourth lens.
16. The imaging lens according to claim 11 ,
wherein a conditional expression (7) below is satisfied:
25<ν d 1−ν d 2<40 (7)
where
νd 1 : Abbe number of the first lens at d-ray
νd 2 : Abbe number of the second lens at d-ray.
17. The imaging lens according to claim 11 ,
wherein a conditional expression (8) below is satisfied:
−0.9< f 5/ f<− 0.4 (8)
where
f: focal length of the overall optical system of the imaging lens
f 5 : focal length of the fifth lens.
18. The imaging lens according to claim 11 ,
wherein a conditional expression (9) below is satisfied:
−1.4<( r 1+ r 2)/( r 1− r 2)<−0.3 (9)
where
r 1 : curvature radius of the object-side surface of the first lens
r 2 : curvature radius of the image-side surface of the first lens.