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 composed of seven lenses to form an image of an object on a solid-state image sensor, in which the lenses are arranged in order from an object side to an image side, comprising:
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,
wherein an air gap is provided between lenses,
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
wherein a conditional expression (5) below is satisfied:
—2.0< f 67/ f<− 0.6 (5)
where
f67: composite focal length of the sixth lens and the seventh lens
f: focal length of the overall optical system of the imaging lens.
2. The imaging lens according to claim 1 ,
wherein the first lens is a lens with positive refractive power having a convex surface on the object side;
the second lens is a lens with positive or negative refractive power having a convex surface on the image side; and
at least one of facing surfaces of the first lens and the second lens is a concave surface.
3. The imaging lens according to claim 1 ,
wherein a conditional expression (1) below is satisfied:
0< f 12 (1)
where
f12: composite focal length of the first lens and the second lens.
4. 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.
5. 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.
6. The imaging lens according to claim 1 ,
wherein the image-side surface of the sixth lens has the aspheric shape in which the concave shape changes to a convex shape in a peripheral portion distant from the optical axis.
7. 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: composite focal length of the first lens and the second lens
f: focal length of the overall optical system of the imaging lens.
8. 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: focal length of the third lens
f: focal length of the overall optical system of the imaging lens.
9. 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: composite focal length of the fourth lens and the fifth lens
f: 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
νd3: Abbe number of the third lens at d-ray.
11. An imaging lens composed of seven lenses to form an image of an object on a solid-state image sensor, in which the lenses are arranged in order from an object side to an image side, comprising:
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,
wherein an air gap is provided between lenses,
the first lens is a lens with positive refractive power having a convex surface on the object side,
the second lens is a lens with positive or negative refractive power having a convex surface on the image side,
at least one of facing surfaces of the first lens and the second lens is a concave surface, and
wherein a conditional expression (13) below is satisfied:
−2.0< f 67/ f<− 0.6 (13)
where
f67: composite focal length of the sixth lens and the seventh lens
f: focal length of the overall optical system of the imaging lens.
12. The imaging lens according to claim 11 ,
wherein a conditional expression (9) below is satisfied:
0< f 12 (9)
Where
f12: 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 (10) below is satisfied:
0.6< f 12/ f< 1.3 (10)
Where
f12: composite focal length of the first lens and the second lens
f: focal length of the overall optical system of the imaging lens.
17. The imaging lens according to claim 11 ,
wherein a conditional expression (11) below is satisfied:
−2.2< f 3/ f<− 1.0 (11)
where
f3: focal length of the third lens
f: focal length of the overall optical system of the imaging lens.
18. The imaging lens according to claim 11 ,
wherein a conditional expression (12) below is satisfied:
0.6< f 45/ f< 2.2 (12)
where
f45: composite focal length of the fourth lens and the fifth lens
f: focal length of the overall optical system of the imaging lens.
19. The imaging lens according to claim 11 ,
wherein conditional expressions (14) to (16) below are satisfied:
50<ν d 1<70 (14)
50<ν d 2<70 (15)
20<ν d 3<30 (16)
where
νd1: Abbe number of the first lens at d-ray
νd2: Abbe number of the second lens at d-ray
νd3: Abbe number of the third lens at d-ray.