Imaging lens
An imaging lens which uses a larger number of constituent lenses for higher performance and features compactness and a wide field of view. The imaging lens is composed of seven lenses to form an image of an object on a solid-state image sensor. The constituent lenses are arranged in the following order from an object side to an image side: a first lens with positive refractive power; a second lens with positive or negative refractive power; a third lens with negative refractive power; a fourth lens with positive or negative refractive power as a double-sided aspheric lens; a meniscus fifth lens having a convex surface on the image side; a sixth lens with positive or negative refractive power as a double-sided aspheric lens; and a seventh lens with negative refractive power, in which an air gap is provided between lenses.
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;
a second lens having positive or negative refractive power;
a third lens having negative refractive power;
a fourth lens that is a double-sided aspheric lens having positive or negative refractive power;
a fifth lens that is a double-sided aspheric lens having positive or negative refractive power;
a sixth lens that is a double-sided aspheric lens having positive or negative refractive power;
a seventh lens that is a double-sided aspheric lens having negative refractive power; and
air gaps disposed between each pair of adjacent lenses,
wherein the imaging lens has a total of seven single lenses, and the sixth lens has a concave surface on the image side near an optical axis.
2. The imaging lens according to claim 1 , wherein a conditional expression (1) below is satisfied:
0< f 12 (1)
where
f12: a composite focal length of the first lens and the second lens.
3. The imaging lens according to claim 1 , wherein the third lens is a double-sided aspheric lens and has a concave surface on the image side near an optical axis.
4. The imaging lens according to claim 1 , wherein the fourth lens is a biconvex lens having a convex surface on the object side near an optical axis or a meniscus lens having a convex surface on the object side.
5. The imaging lens according to claim 1 , wherein an image-side surface of the sixth lens has an aspheric shape in which a portion near an optical axis has a concave shape and the concave shape changes to a convex shape in a peripheral portion distant from the optical axis.
6. The imaging lens according to claim 1 , wherein a conditional expression (2) below is satisfied:
0.6< f 12/ f< 1.3 (2)
where
f12: a composite focal length of the first lens and the second lens, and
f: a focal length of the overall optical system of the imaging lens.
7. The imaging lens according to claim 1 , wherein a conditional expression (3) below is satisfied:
−2.2< f 3/ f<− 1.0 (3)
where
f3: a focal length of the third lens, and
f: a focal length of the overall optical system of the imaging lens.
8. The imaging lens according to claim 1 , wherein a conditional expression (4) below is satisfied:
0.6< f 45/ f< 2.2 (4)
where
f45: a composite focal length of the fourth lens and the fifth lens, and
f: a focal length of the overall optical system of the imaging lens.
9. The imaging lens according to claim 1 , wherein a conditional expression (5) below is satisfied:
−2.0< f 67/ f<− 0.6 (5)
where
f67: a composite focal length of the sixth lens and the seventh lens, and
f: a focal length of the overall optical system of the imaging lens.
10. The imaging lens according to claim 1 , wherein conditional expressions (6) to (8) below are satisfied:
50<ν d 1<70 (6)
50<ν d 2<70 (7)
20<ν d 3<30 (8)
where
νd1: Abbe number of the first lens at d-ray,
νd2: Abbe number of the second lens at d-ray, and
νd3: Abbe number of the third lens at d-ray.
11. 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;
a second lens having positive refractive power;
a third lens having negative refractive power;
a fourth lens that is a double-sided aspheric lens having positive or negative refractive power;
a fifth lens that is a double-sided aspheric lens having positive or negative refractive power;
a sixth lens that is a double-sided aspheric lens having positive or negative refractive power;
a seventh lens that is a double-sided aspheric lens having negative refractive power; and
air gaps disposed between each pair of adjacent lenses,
wherein the third lens has a convex surface on the object side near an optical axis, and conditional expression (8) below is satisfied:
20<ν d 3<30 (8)
where
νd3: Abbe number of the third lens at d-ray.
12. The imaging lens according to claim 11 , wherein a conditional expression (1) below is satisfied:
0< f 12 (1)
where
f12: a composite focal length of the first lens and the second lens.
13. The imaging lens according to claim 11 , wherein the third lens is a double-sided aspheric lens and has a concave surface on the image side near an optical axis.
14. The imaging lens according to claim 11 , wherein the fourth lens is a biconvex lens having a convex surface on the object side near an optical axis or a meniscus lens having a convex surface on the object side.
15. The imaging lens according to claim 11 , wherein an image-side surface of the sixth lens has an aspheric shape in which a portion near an optical axis has a concave shape and the concave shape changes to a convex shape in a peripheral portion distant from the optical axis.
16. The imaging lens according to claim 11 , wherein a conditional expression (2) below is satisfied:
0.6< f 12/ f< 1.3 (2)
where
f12: a composite focal length of the first lens and the second lens, and
f: a focal length of the overall optical system of the imaging lens.
17. The imaging lens according to claim 11 , wherein a conditional expression (3) below is satisfied:
−2.2< f 3/ f<− 1.0 (3)
where
f3: a focal length of the third lens, and
f: a focal length of the overall optical system of the imaging lens.
18. The imaging lens according to claim 11 , wherein a conditional expression (4) below is satisfied:
0.6< f 45/ f< 2.2 (4)
where
f45: a composite focal length of the fourth lens and the fifth lens, and
f: a focal length of the overall optical system of the imaging lens.
19. The imaging lens according to claim 11 , wherein a conditional expression (5) below is satisfied:
−2.0< f 67/ f<− 0.6 (5)
where
f67: a composite focal length of the sixth lens and the seventh lens, and
f: a focal length of the overall optical system of the imaging lens.
20. The imaging lens according to claim 11 , wherein conditional expressions (6) and (7) below are satisfied:
50<ν d 1<70 (6)
50<ν d 2<70 (7)
where
νd1: Abbe number of the first lens at d-ray, and
νd2: Abbe number of the second lens at d-ray.