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, comprising in order from an object side to an image side of the imaging lens:
a first lens having positive refractive power and a convex surface facing the object side;
a second lens;
a third lens that is a double-sided aspheric lens having a convex surface facing the image side;
a fourth lens that is a double-sided aspheric lens having positive refractive power;
a fifth lens that is a double-sided aspheric lens having a concave surface facing the image side; and
a sixth lens that is a double-sided aspheric lens, at least one of an object-side surface and an image-side surface of the sixth lens having a pole-change point separated from an optical axis of the imaging lens,
wherein a maximum field of view of the imaging lens is 80 degrees or more.
2. The imaging lens according to claim 1 , wherein the first lens has a convex surface facing the image side,
the second lens has negative refractive power, a convex surface facing the object side, and a concave surface facing the image side, and
the third lens has positive refractive power and a convex surface facing the object side.
3. The imaging lens according to claim 1 , wherein the fourth lens has a convex surface facing the image side,
the fifth lens has a convex surface facing the object side, at least one of an object-side surface and an image-side surface of the fifth lens having a pole-change point separated from the optical axis, and
the sixth lens has negative refractive power and a concave image-side surface.
4. The imaging lens according to claim 1 , wherein when f is an overall focal length of the imaging lens, and f1 is a focal length of the first lens, a conditional expression (1) below is satisfied:
0.55< f 1/ f< 1.7. (1)
5. The imaging lens according to claim 2 , wherein when f is an overall focal length of the imaging lens, and f2 is a focal length of the second lens, a conditional expression (2) below is
−2.3< f 2/ f<− 0.8. (2)
6. The imaging lens according to claim 1 , wherein when νd1 is an Abbe number of the first lens at d-ray, and νd2 is an Abbe number of the second lens at d-ray, conditional expressions (3) and (4) below are satisfied:
45<ν d 1<80 (3)
20<ν d 2<40. (4)
7. The imaging lens according to claim 1 , wherein when νd3 is an Abbe number of the third lens at d-ray, νd4 is an Abbe number of the fourth lens at d-ray, νd5 is an Abbe number of the fifth lens at d-ray, and νd6 is an Abbe number of the sixth lens at d-ray, 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)
8. The imaging lens according to claim 1 , wherein when TTL is a distance along the optical axis from an image plane of the imaging lens to an object-side surface of an optical element located nearest an imaged object, and Ed is a distance along the optical axis from an object-side surface of the first lens to the image-side surface of the sixth lens, a conditional expression (9) below is satisfied:
0.65<Σ d/TTL< 0.90. (9)
9. The imaging lens according to claim 3 , wherein when TTL is a distance along the optical axis from an image plane of the imaging lens to an object-side surface of an optical element located nearest an imaged object, and f is an overall focal length of the imaging lens, a conditional expression (10) below is satisfied:
TTL/f< 1.6. (10)
10. The imaging lens according to claim 1 , wherein when f is an overall focal length of the imaging lens, and ih is a maximum image height, a
0.8< ih/f< 1.2. (11)
11. The imaging lens according to claim 2 , wherein when f is an overall focal length of the imaging lens, and f3 is a focal length of the third lens, a conditional expression (12) below is satisfied:
1.3< f 3/ f< 7.0. (12)
12. An imaging lens for a solid-state image sensor, comprising, in order from an object side to an image side of the imaging lens:
a first lens having positive refractive power and a convex surface facing the image side;
a second lens having a convex surface facing the object side;
a third lens that is a double-sided aspheric lens;
a fourth lens that is a double-sided aspheric lens having a concave surface facing object side;
a fifth lens that is a double-sided aspheric lens; and
a sixth lens that is a double-sided aspheric lens, at least one of an object-side surface and an image-side surface of the sixth lens having a pole-change point separated from an optical axis of the imaging lens,
wherein when νd4 is an Abbe number of the fourth lens at d-ray, and νd5 is an Abbe number of the fifth lens at d-ray, conditional expressions (6) and (7) below are satisfied:
50<ν d 4<75 (6)
20<ν d 5<40. (7)
13. The imaging lens according to claim 12 , wherein the first lens has a convex surface facing the object side,
the second lens has negative refractive power and a concave surface facing the image side, and
the third lens has positive refractive power and convex surfaces facing the object side and image side.
14. The imaging lens according to claim 12 , wherein the fourth lens has positive refractive power and a convex surface facing the image side,
the fifth lens has negative refractive power, a convex surface facing the object side, and a concave surface facing the image side, at least one of an object-side surface and an image-side surface of the fifth lens having a pole-change point separated from the optical axis, and
the sixth lens has negative refractive power and a concave image-side surface.
15. The imaging lens according to claim 13 , wherein when f is an overall focal length of the imaging lens, and f1 is a focal length of the first lens, a conditional expression (1) below is satisfied:
0.55< f 1/ f< 1.7. (1)
16. The imaging lens according to claim 13 , wherein when f is an overall focal length of the imaging lens, and f2 is a focal length of the second lens, a conditional expression (2) below is satisfied:
−2.3< f 2/ f<− 0.8. (2)
17. The imaging lens according to claim 12 , wherein when νd1 is an Abbe number of the first lens at d-ray, and νd2 is an Abbe number of the second lens at d-ray, conditional expressions (3) and (4) below are satisfied:
45<ν d 1<80 (3)
20 <νd 2<40. (4)
18. The imaging lens according to claim 12 , wherein when νd3 is an Abbe number of the third lens at d-ray, and νd6 is an Abbe number of the sixth lens at d-ray, conditional expressions (5) and (8) below are satisfied:
50<ν d 3<75 (5)
50<ν d 4<75. (6)
19. The imaging lens according to claim 12 , wherein when f is an overall focal length of the imaging lens, and ih is a maximum image height, a conditional expression (11) below is satisfied:
0.8< ih/f< 1.2. (11)
20. The imaging lens according to claim 13 , wherein when f is an overall focal length of the imaging lens, and f3 is a focal length of the third lens, a conditional expression (12) below is satisfied:
1.3< f 3/ f< 7.0. (12)