Imaging lens
An imaging lens which uses a larger number of constituent lenses for higher performance and features a low F-value, low-profile design and a wide field of view. Designed for a solid-state image sensor, the imaging lens includes constituent lenses arranged in order from an object side to an image side: a first positive refractive power lens; a second negative refractive power lens; a third lens; a fourth lens; a fifth lens; a sixth lens having a concave image-side surface near an optical axis; and a seventh negative refractive power lens.
1. An imaging lens, comprising, in order from an object side to an image side thereof:
a first lens with positive refractive power;
a second lens having an aspheric surface;
a third lens having an aspheric surface;
a fourth lens having an aspheric surface;
a fifth lens having an aspheric surface;
a sixth lens that is a double-sided aspheric lens having an image-side surface that is concave near an optical axis of the imaging lens; and
a seventh lens that is a double-sided aspheric lens having an image-side surface that is concave near the optical axis, the image-side surface of the seventh lens having a pole-change point separated from the optical axis;
wherein a conditional expressions (1) and (2) below are satisfied:
50<ν d 1<70 (1)
20<ν d 2<30 (2)
where
νd1: Abbe number of the first lens at d-ray, and
νd2: Abbe number of the second lens at d-ray.
2. The imaging lens according to claim 1 , wherein the first lens has an object-side surface that is convex near the optical axis, and the second lens has negative refractive power and an image-side surface that is concave near the optical axis.
3. The imaging lens according to claim 1 , wherein the third lens has positive refractive power and an image-side surface that is convex near the optical axis, and the fourth lens has negative refractive power and an image-side surface that is concave near the optical axis.
4. The imaging lens according to claim 1 , wherein the fifth lens is a meniscus lens having positive refractive power and an image-side surface that is convex near the optical axis.
5. The imaging lens according to claim 4 , wherein a conditional expression (11) below is satisfied:
0.6< f 5/ f< 1.2 (11)
where
f: overall focal length of the imaging lens, and
f5: focal length of the fifth lens.
6. The imaging lens according to claim 1 , wherein the sixth lens is a meniscus lens having negative refractive power and a pole-change point separated from the optical axis on each of an object-side surface and the image-side surface thereof, and the seventh lens has negative refractive power.
7. The imaging lens according to claim 6 , wherein a conditional expression (12) below is satisfied:
−1.2< f 67/ f<− 0.6 (12)
where
f: overall focal length of the imaging lens, and
f67: composite focal length of the sixth lens and the seventh lens.
8. The imaging lens according to claim 1 , wherein conditional expressions (3) and (4) below are satisfied:
50<ν d 3<70 (3)
20<ν d 4<30 (4)
where
νd3: Abbe number of the third lens at d-ray, and
νd4: Abbe number of the fourth lens at d-ray.
9. The imaging lens according to claim 1 , wherein a conditional expression (5) below is satisfied:
0.6< TTL/ 2 ih< 1.0 (5)
where
TTL: 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
ih: maximum image height.
10. The imaging lens according to claim 1 , wherein a conditional expression (6) below is satisfied:
0.85<Σ d/f< 1.25 (6)
where
f: overall focal length of the imaging lens, and
Σd: distance along the optical axis from an object-side surface of the first lens to the image-side surface of the seventh lens.
11. The imaging lens according to claim 1 , wherein a conditional expression (7) below is satisfied:
0.8< ih/f< 1.2 (7)
where
f: overall focal length of the imaging lens, and
ih: maximum image height.
12. The imaging lens according to claim 1 , wherein conditional expressions (8) and (9) below are satisfied:
0.7< f 1/ f< 1.5 (8)
−5.0< f 2/ f<− 1.0 (9)
where
f: overall focal length of the imaging lens,
f1: focal length of the first lens, and
f2: focal length of the second lens.
13. The imaging lens according to claim 1 , wherein a conditional expression (10) below is satisfied:
2.0<| f 34/ f| (10)
where
f: overall focal length of the imaging lens, and
f34: composite focal length of the third lens and the fourth lens.
14. The imaging lens according to claim 1 , wherein conditional expressions (13), (14), and (15) below are satisfied:
50<ν d 5<70 (13)
20<ν d 6<30 (14)
50<ν d 7<70 (15)
where
νd5: Abbe number of the fifth lens at d-ray,
νd6: Abbe number of the sixth lens at d-ray, and
νd7: Abbe number of the seventh lens at d-ray.
15. An imaging lens, comprising, in order from an object side to an image side thereof:
a first lens with positive refractive power;
a second lens having an aspheric surface;
a third lens having an aspheric surface;
a fourth lens having an aspheric surface;
a fifth lens having an aspheric surface;
a sixth lens that is a double-sided aspheric lens having an image side surface that is concave near an optical axis of the imaging lens; and
a seventh lens that is a double-sided aspheric lens having an image-side surface that is concave near the optical axis, the image-side surface of the seventh lens having a pole-change point separated from the optical axis,
wherein a conditional expression (8) below is satisfied:
0.7< f 1/ f< 1.5 (8)
where
f: overall focal length of the imaging lens, and
f1: focal length of the first lens.
16. The imaging lens according to claim 15 , wherein the second lens has negative refractive power and an image-side surface that is concave near the optical axis.
17. The imaging lens according to claim 15 , wherein the third lens has positive refractive power and an image-side surface that is convex near the optical axis, and the fourth lens has negative refractive power and an image-side surface that is concave near the optical axis.
18. The imaging lens according to claim 15 , wherein the fifth lens is a meniscus lens having positive refractive power and an image-side surface that is convex near the optical axis.
19. The imaging lens according to claim 15 , wherein the sixth lens is a meniscus lens having negative refractive power and a pole change point separated from the optical axis on each of an object-side surface and the image-side surface thereof, and the seventh lens has negative refractive power.
20. The imaging lens according to claim 15 , wherein a conditional expression (5) below is satisfied:
0.6< TTL/ 2 ih< 1.0 (5)
where
TTL: 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
ih: maximum image height.