Imaging lens
A compact high-resolution imaging lens which provides a wide field of view of 80 degrees or more and corrects various aberrations properly. Designed for a solid-state image sensor, the imaging lens includes constituent lenses arranged in the following order from an object side to an image side: a first positive (refractive power) lens having a convex object-side surface; a second negative lens having a concave image-side surface; a third positive lens as a double-sided aspheric lens having a convex object-side surface; a fourth positive lens having a convex image-side surface; a fifth lens as a double-sided aspheric lens having a concave image-side surface; and a sixth negative lens having a concave image-side surface. The image-side surface of the sixth lens has an aspheric shape with a pole-change point in a position off an optical axis.
1. An imaging lens for a solid-state image sensor in which elements are arranged in order from an object side to an image side, comprising:
a first lens with positive refractive power having convex surfaces on the object side and the image side;
a second lens with negative refractive power having a concave surface on the image side and a convex surface on the object side;
a third lens with positive refractive power as a double-sided aspheric lens having a convex surface on the object side;
a fourth lens with positive refractive power having a convex surface on the image side;
a fifth lens as a double-sided aspheric lens having a concave surface on the image side; and
a sixth lens with negative refractive power having a concave surface on the image side,
wherein the image-side surface of the sixth lens has an aspheric shape with a pole-change point in a position off an optical axis.
2. The imaging lens according to claim 1 ,
wherein a conditional expression (11) below is satisfied:
0.8< ih/f< 1.2 (11)
where
f: focal length of an overall optical system of the imaging lens
ih: maximum image height.
3. The imaging lens according to claim 1 ,
wherein a conditional expression (9) below is satisfied:
0.65<Σ d/TTL< 0.90 (9)
where
TTL: distance on the optical axis from an object-side surface of an optical element located nearest to an object to an image plane without a filter, etc.
Σd: distance on the optical axis from the object-side surface of the first lens to the image-side surface of the sixth lens.
4. The imaging lens according to claim 3 ,
wherein a conditional expression (10) below is satisfied:
TTL/f< 1.6 (10)
where
TTL: distance on the optical axis from an object-side surface of an optical element located nearest to an object to an image plane without a filter, etc.
f: focal length of an overall optical system of the imaging lens.
5. The imaging lens according to claim 1 ,
wherein:
the fifth lens is a meniscus lens with negative refractive power and the object-side surface and the image-side surface of the fifth lens have an aspheric shape with a pole-change point in a position off the optical axis; and
the sixth lens is a meniscus lens and the object-side surface of the sixth lens has an aspheric shape with a pole-change point in a position off the optical axis.
6. The imaging lens according to claim 1 ,
wherein a conditional expression (1) below is satisfied:
0.55< f 1/ f< 1.7 (1)
where
f1: focal length of the first lens
f: focal length of an overall optical system of the imaging lens.
7. The imaging lens according to claim 6 ,
wherein a conditional expression (2) below is satisfied:
−2.3< f 2/ f<− 0.8 (2)
where
f2: focal length of the second lens
f: focal length of an overall optical system of the imaging lens.
8. The imaging lens according to claim 7 ,
wherein a conditional expression (12) below is satisfied:
1.3< f 3/ f< 7.0 (12)
where
f3: focal length of the third lens
f: focal length of an overall optical system of the imaging lens.
9. The imaging lens according to claim 1 ,
wherein conditional expressions (3) and (4) below are satisfied:
45<ν d 1<80 (3)
20<ν d 2<40 (4)
where
νd1: Abbe number of the first lens at d-ray
νd2: Abbe number of the second lens at d-ray.
10. The imaging lens according to claim 1 ,
wherein conditional expressions (5) to (8) below are satisfied:
50<ν d 3<75 (5)
50<ν d 4<75 (6)
20<ν d 5<40 (7)
50<ν d 6<75 (8)
where
νd3: Abbe number of the third lens at d-ray
νd4: Abbe number of the fourth lens at d-ray
νd5: Abbe number of the fifth lens at d-ray
νd6: Abbe number of the sixth lens at d-ray.
11. The imaging lens according to claim 2 ,
wherein a conditional expression (9) below is satisfied:
0.65<Σ d/TTL< 0.90 (9)
where
TTL: distance on the optical axis from an object-side surface of an optical element located nearest to an object to an image plane without a filter, etc.
Σd: distance on the optical axis from the object-side surface of the first lens to the image-side surface of the sixth lens.
12. The imaging lens according to claim 11 ,
wherein a conditional expression (10) below is satisfied:
TTL/f< 1.6 (10)
where
TTL: distance on the optical axis from an object-side surface of an optical element located nearest to an object to an image plane without a filter, etc.
f: focal length of an overall optical system of the imaging lens.
13. The imaging lens according to claim 2 ,
wherein:
the fifth lens is a meniscus lens with negative refractive power and the object-side surface and the image-side surface of the fifth lens have an aspheric shape with a pole-change point in a position off the optical axis; and
the sixth lens is a meniscus lens and the object-side surface of the sixth lens has an aspheric shape with a pole-change point in a position off the optical axis.
14. The imaging lens according to claim 2 ,
wherein a conditional expression (1) below is satisfied:
0.55< f 1/ f< 1.7 (1)
where
f1: focal length of the first lens
f: focal length of an overall optical system of the imaging lens.
15. The imaging lens according to claim 14 ,
wherein a conditional expression (2) below is satisfied:
−2.3< f 2/ f<− 0.8 (2)
where
f2: focal length of the second lens
f: focal length of an overall optical system of the imaging lens.
16. The imaging lens according to claim 15 ,
wherein a conditional expression (12) below is satisfied:
1.3< f 3/ f< 7.0 (12)
where
f3: focal length of the third lens
f: focal length of an overall optical system of the imaging lens.
17. The imaging lens according to claim 2 ,
wherein conditional expressions (3) and (4) below are satisfied:
45<ν d 1<80 (3)
20<ν d 2<40 (4)
where
νd1: Abbe number of the first lens at d-ray
νd2: Abbe number of the second lens at d-ray.
18. The imaging lens according to claim 2 ,
wherein conditional expressions (5) to (8) below are satisfied:
50<ν d 3<75 (5)
50<ν d 4<75 (6)
20<ν d 5<40 (7)
50<ν d 6<75 (8)
where
νd3: Abbe number of the third lens at d-ray
νd4: Abbe number of the fourth lens at d-ray
νd5: Abbe number of the fifth lens at d-ray
νd6: Abbe number of the sixth lens at d-ray.
19. The imaging lens according to claim 8 ,
wherein conditional expressions (5) to (8) below are satisfied:
50<ν d 3<75 (5)
50<ν d 4<75 (6)
20<ν d 5<40 (7)
50<ν d 6<75 (8)
where
νd3: Abbe number of the third lens at d-ray
νd4: Abbe number of the fourth lens at d-ray
νd5: Abbe number of the fifth lens at d-ray
νd6: Abbe number of the sixth lens at d-ray.
20. The imaging lens according to claim 16 ,
wherein conditional expressions (5) to (8) below are satisfied:
50<ν d 3<75 (5)
50<ν d 4<75 (6)
20<ν d 5<40 (7)
50<ν d 6<75 (8)
where
νd3: Abbe number of the third lens at d-ray
νd4: Abbe number of the fourth lens at d-ray
νd5: Abbe number of the fifth lens at d-ray
νd6: Abbe number of the sixth lens at d-ray.