Imaging lens
An imaging lens which forms an image of an object on a solid-state image sensor includes a first through fifth lens in order from an object side to an image side of the imaging lens. The imaging lens includes: a first lens that is a meniscus lens having a convex surface facing the object side; a second lens; and a third lens that is a meniscus lens and has a convex surface facing the image side near an optical axis of the imaging lens. The imaging lens further includes: a fourth lens having a concave surface facing the object side and a convex surface facing the image side near the optical axis; and a fifth lens. An F-value of the imaging lens is 2.5 or less.
1. An imaging lens which forms an image of an object on a solid-state image sensor, comprising, in order from an object side to an image side of the imaging lens:
a first lens that is a meniscus lens having a convex surface facing the object side;
a second lens;
a third lens that is a meniscus lens and has a convex surface that faces the image side and intersects an optical axis of the imaging lens;
a fourth lens having a concave surface facing the object side and a convex surface that faces the image side and intersects the optical axis; and
a fifth lens;
wherein an F-value is 2.5 or less, and conditional expressions (4b) and (6b) below are satisfied:
0.6≤ f 1/ f≤ 0.8 (4b)
1.65≤ r 4/ f≤ 1.9 (6b)
where
f: overall focal length of the imaging lens,
f1: focal length of the first lens, and
r4: curvature radius of an image-side surface of the second lens.
2. The imaging lens according to claim 1 , wherein the first lens has positive refractive power, the image-side surface of the second lens is concave, and the second lens has negative refractive power.
3. The imaging lens according to claim 1 , wherein the fourth lens has aspheric surfaces facing both sides, the fifth lens has a concave surface facing the image side and aspheric surfaces facing both sides, and the aspheric surface facing the image side of the fifth lens has a pole-change point separated from the optical axis.
4. The imaging lens according to claim 1 , wherein conditional expressions (1) and (2) below are satisfied:
TTL/2 ih≤ 0.8 (1)
20<ν d 1−ν d 2<50 (2)
where
TTL: total track length,
ih: maximum image height,
νd1: Abbe number of the first lens at d-ray, and
νd2: Abbe number of the second lens at d-ray.
5. The imaging lens according to claim 1 , wherein a conditional expression (3) below is satisfied:
0<ν d 3−ν d 4<40 (3)
where
νd3: Abbe number of the third lens at d-ray, and
νd4: Abbe number of the fourth lens at d-ray.
6. The imaging lens according to claim 1 , wherein a conditional expression (5) below is satisfied:
−1.5< f 2345/ f<− 0.6 (5)
where
f2345: composite focal length of the second lens, the third lens, the fourth lens, and the fifth lens.
7. The imaging lens according to claim 1 , wherein a conditional expression (7) below is satisfied:
−1.9<( r 1+ r 2)/( r 1− r 2)<−0.7 (7)
where
r1: curvature radius of an object-side surface of the first lens, and
r2: curvature radius of an image-side surface of the first lens.
8. The imaging lens according to claim 1 , wherein a conditional expression (8) below is satisfied:
−6.0< f 45/ f<− 3.0 (8)
where
f45: composite focal length of the fourth lens and the fifth lens.
9. An imaging lens which forms an image of an object on a solid-state image sensor, comprising, in order from an object side to an image side of the imaging lens:
a first lens having a convex surface facing the image side;
a second lens having a concave surface facing the image side;
a third lens having a concave surface facing the image side and negative refractive power;
a fourth lens; and
a fifth lens having a convex surface that faces the object side and intersects an optical axis of the imaging lens;
wherein an F-value is 2.5 or less, and conditional expressions (3) and (8b) below are satisfied:
0<ν d 3−ν d 4<40 (3)
−4.68≤ f 45/ f≤− 3.49 (8b)
where
νd3: Abbe number of the third lens at d-ray,
νd4: Abbe number of the fourth lens at d-ray,
f: overall focal length of the imaging lens, and
f45: composite focal length of the fourth lens and the fifth lens.
10. The imaging lens according to claim 9 , wherein the first lens has a convex surface facing the object side and positive refractive power, and the second lens has negative refractive power.
11. The imaging lens according to claim 9 , wherein the fourth lens is a meniscus lens having a convex surface facing the image side and aspheric surfaces facing both sides, the fifth lens has a concave surface facing the image side and aspheric surfaces facing both sides, and the aspheric surface facing the image side of the fifth lens has a pole-change point separated from the optical axis.
12. The imaging lens according to claim 9 , wherein conditional expressions (1) and (2) below are satisfied:
TTL/2 ih≤ 0.8 (1)
20<ν d 1−ν d 2<50 (2)
where
TTL: total track length,
ih: maximum image height,
νd1: Abbe number of the first lens at d-ray, and
νd2: Abbe number of the second lens at d-ray.
13. The imaging lens according to claim 9 , wherein conditional expressions (4) and (5) below are satisfied:
0.4< f 1/ f< 1.0 (4)
−1.5< f 2345/ f<− 0.6 (5)
where
f1: focal length of the first lens, and
f2345: composite focal length of the second lens, the third lens, the fourth lens, and the fifth lens.
14. The imaging lens according to claim 9 , wherein a conditional expression (6) below is satisfied:
1.5< r 4/ f< 2.3 (6)
where
r4: curvature radius of an image-side surface of the second lens.
15. The imaging lens according to claim 9 , wherein a conditional expression (7) below is satisfied:
−1.9<( r 1+ r 2)/( r 1− r 2)<−0.7 (7)
where
r1: curvature radius of an object-side surface of the first lens, and
r2: curvature radius of an image-side surface of the first lens.
16. An imaging lens which forms an image of an object on a solid-state image sensor, comprising, in order from an object side to an image side of the imaging lens:
a first lens having a convex surface facing the image side;
a second lens having a concave surface facing the image side;
a third lens having a concave surface facing the image side and negative refractive power;
a fourth lens; and
a fifth lens that is a meniscus lens;
wherein an F-value is 2.5 or less, and conditional expressions (3), (5b), and (8b) below are satisfied:
0<ν d 3−ν d 4<40 (3)
−1.42≤ f 2345/ f≤− 0.76 (5b)
−4.68≤ f 45/ f≤− 3.49 (8b)
where
νd3: Abbe number of the third lens at d-ray,
νd4: Abbe number of the fourth lens at d-ray,
f: overall focal length of the imaging lens,
f2345: composite focal length of the second lens, the third lens, the fourth lens, and the fifth lens, and
f45: composite focal length of the fourth lens and the fifth lens.
17. The imaging lens according to claim 16 , wherein the first lens has a convex surface facing the object side and positive refractive power, and the second lens has negative refractive power.
18. The imaging lens according to claim 16 , wherein the fourth lens is a meniscus lens having a convex surface facing the image side and aspheric surfaces facing both sides, the fifth lens has a concave surface facing the image side and aspheric surfaces facing both sides, and the aspheric surface facing the image side of the fifth lens has a pole-change point separated from an optical axis of the imaging lens.
19. The imaging lens according to claim 16 , wherein conditional expressions (1) and (2) below are satisfied:
TTL/2 ih≤ 0.8 (1)
20<ν d 1−ν d 2<50 (2)
where
TTL: total track length,
ih: maximum image height,
νd1: Abbe number of the first lens at d-ray, and
νd2: Abbe number of the second lens at d-ray.
20. The imaging lens according to claim 16 , wherein a conditional expression (4) below is satisfied:
0.4< f 1/ f< 1.0 (4)
where
f1: focal length of the first lens.
21. The imaging lens according to claim 16 , wherein a conditional expression (6) below is satisfied:
1.5< r 4/ f< 2.3 (6)
where
r4: curvature radius of an image-side surface of the second lens.
22. The imaging lens according to claim 16 , wherein a conditional expression (7) below is satisfied:
−1.9<( r 1+ r 2)/( r 1− r 2)<−0.7 (7)
where
r1: curvature radius of an object-side surface of the first lens
r2: curvature radius of an image-side surface of the first lens.