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;
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 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 a concave surface facing the object side near an optical axis; and
air gaps disposed between each pair of adjacent lenses,
wherein the imaging lens has a total of seven single lenses, and when f12 is a composite focal length of the first lens and the second lens, a conditional expression (1′) below is satisfied:
6.01≤ f 12. (1′)
2. The imaging lens according to claim 1 , wherein the first lens has a convex surface facing the object side, the second lens has a convex surface facing the image side, and at least one of facing surfaces of the first lens and the second lens has a concave surface.
3. The imaging lens according to claim 1 , wherein the third lens is a double-sided aspheric lens and has negative refractive power and a concave surface facing the image side near the optical axis.
4. The imaging lens according to claim 1 , wherein the fourth lens is one of:
a biconvex lens having a convex surface facing the object side near the optical axis, and
a meniscus lens having a convex surface facing 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 the optical axis has a concave shape and the concave shape changes to a convex shape in a peripheral portion separated from the optical axis.
6. The imaging lens according to claim 1 , wherein when f is an overall focal length of the imaging lens, a conditional expression (2) below is satisfied:
0.6< f 12/ f< 1.3. (2)
7. The imaging lens according to claim 1 , wherein when f3 is a focal length of the third lens, and f is an overall focal length of the imaging lens, a conditional expression (3) below is satisfied:
−2.2< f 3/ f<− 1.0. (3)
8. The imaging lens according to claim 1 , wherein when f45 is a composite focal length of the fourth lens and the fifth lens, and f is an overall focal length of the imaging lens, a conditional expression (4) below is satisfied:
0.6< f 45/ f< 2.2. (4)
9. The imaging lens according to claim 1 , wherein when f67 is a composite focal length of the sixth lens and the seventh lens, and f is an overall focal length of the imaging lens, a conditional expression (5) below is satisfied:
−2.0< f 67/ f<− 0.6. (5)
10. The imaging lens according to claim 1 , wherein when vd1 is an Abbe number of the first lens at d-ray, vd2 is an Abbe number of the second lens at d-ray, and vd3 is an Abbe number of the third lens at d-ray, conditional expressions (6) to (8) below are satisfied:
50< vd 1<70 (6)
50< vd 2<70 (7)
20< vd 3<30. (8
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 or negative refractive power;
a third lens;
a fourth lens that is a double-sided aspheric lens having positive refractive power and a convex surface facing the object side near an optical axis;
a fifth lens that is a double-sided aspheric lens;
a sixth lens that is a double-sided aspheric lens having positive or negative refractive power and a concave surface facing the image side near the optical axis;
a seventh lens that is a double-sided aspheric lens having a meniscus shape near the optical axis; and
air gaps disposed between each pair of adjacent lenses.
12. The imaging lens according to claim 11 , wherein the first lens has a convex surface facing the object side, second lens has a convex surface facing the image side, and at least one of facing surfaces of the first lens and the second lens has a concave surface.
13. The imaging lens according to claim 11 , wherein the third lens is a double-sided aspheric lens having negative refractive power and a concave surface facing the image side near the optical axis.
14. The imaging lens according to claim 11 , wherein the fourth lens is one of:
a biconvex lens having a convex surface facing the object side near the optical axis, and
a meniscus lens having a convex surface facing 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 the optical axis has a concave shape and the concave shape changes to a convex shape in a peripheral portion separated from the optical axis.
16. The imaging lens according to claim 11 , wherein when f12 is a composite focal length of the first lens and the second lens, and f is an overall focal length of the imaging lens, a conditional expression (2) below is satisfied:
0.6< f 12/ f< 1.3. (2)
17. The imaging lens according to claim 11 , wherein when f3 is a focal length of the third lens, and f is an overall focal length of the imaging lens, a conditional expression (3) below is satisfied:
−2.2< f 3/ f<− 1.0. (3)
18. The imaging lens according to claim 11 , wherein when f45 is a composite focal length of the fourth lens and the fifth lens, and f is an overall focal length of the imaging lens, a conditional expression (4) below is satisfied:
0.6< f 45/ f< 2.2. (4)
19. The imaging lens according to claim 11 , wherein when f67 is a composite focal length of the sixth lens and the seventh lens, and f is an overall focal length of the imaging lens, a conditional expression (5) below is satisfied:
−2.0< f 67/ f<− 0.6. (5)
20. The imaging lens according to claim 11 , wherein when vd1 is an Abbe number of the first lens at d-ray, vd2 is an Abbe number of the second lens at d-ray, and vd3 is an Abbe number of the third lens at d-ray, conditional expressions (6) to (8) below are satisfied:
50< vd 1<70 (6)
50< vd 2<70 (7)
20< vd 3<30. (8)