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 convex surfaces facing the object side and the image side;
a second lens having a convex surface facing the object side and a concave surface facing the image side;
a third lens that is a double-sided aspheric lens having positive refractive power;
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 negative refractive power and a convex surface facing the object 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.
2. The imaging lens according to claim 1 , wherein the second lens has negative refractive power, and the third lens has a convex surface facing the object side.
3. The imaging lens according to claim 1 , wherein the fourth lens has a concave surface facing the object side and a convex surface facing the image side,
the fifth lens has 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.
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 satisfied:
−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 Σd 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 conditional expression (11b) below is satisfied:
0.8< ih/f< 1.2. (11)
11. The imaging lens according to claim 1 , 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 convex surfaces facing the object side and the image side;
a second lens having a convex surface facing the object side and concave surface facing the image 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 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 composite refractive power of the fifth and sixth lenses is negative.
13. The imaging lens according to claim 12 , wherein the second lens has negative refractive power, and the third lens has positive refractive power and a convex surface facing the object 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 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,
the sixth lens has negative refractive power and a concave image-side surface.
15. The imaging lens according to claim 12 , 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<ν d 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, 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).