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 a concave surface facing the image side near an optical axis;
a third lens having at least one aspheric surface;
a fourth lens having at least one aspheric surface;
a fifth lens having at least one aspheric surface;
a sixth lens that is a double-sided aspheric lens and has a concave surface facing the image side near the optical axis; and
a seventh lens with negative refractive power that is a double-sided aspheric lens, and has a pole-change point in a position off the optical axis on an image-side aspheric surface thereof; wherein the lenses are arranged with an air gap provided therebetween, and a conditional expression (1) below is satisfied:
50<ν d 1<70 (1)
where:
νd1 abbe number of the first lens at d-ray.
2. The imaging lens according to claim 1 , wherein a conditional expression (2) below is satisfied:
20<ν d 2<30 (2)
where
νd2: abbe number of the second lens at d-ray.
3. 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.
4. The imaging lens according to claim 1 , wherein a conditional expression (6) below is satisfied:
0.85<Σ d/f< 1.25 (6)
where
Σd: distance along the optical axis from an object-side surface of the first lens to the image-side surface of the seventh lens, and
f: focal length of the overall optical system of the imaging lens.
5. The imaging lens according to claim 1 , wherein a conditional expression (7) below is satisfied:
0.8< ih/f< 1.2 (7)
where
ih: maximum image height, and
f: focal length of the overall optical system of the imaging lens.
6. 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: focal length of the overall optical system of the imaging lens,
f1: focal length of the first lens, and
f2: focal length of the second lens.
7. The imaging lens according to claim 1 , wherein a conditional expression (10) below is satisfied:
2.0<| f 34/ f| (10)
where
f: focal length of the overall optical system of the imaging lens, and
f34: composite focal length of the third lens and the fourth lens.
8. The imaging lens according to claim 1 , wherein a conditional expression (11) below is satisfied:
0.6< f 5/ f< 1.2 (11)
where
f: focal length of the overall optical system of the imaging lens, and
f5: focal length of the fifth lens.
9. 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.