Image capturing lens and image capturing apparatus
View Patent ↗Arranging a negative first lens, a positive second lens, a negative third lens, a positive fourth lens, and a positive fifth lens from the object side, in which the image side surface of the fifth lens has an aspherical shape with one or more inflection points and a concave shape toward the image side in a paraxial region, and, when the overall optical length, focal length of the entire lens system, focal length of the first lens, distance between image side surface of the second lens and object side surface of the third lens, refractive index of the second lens, and refractive index of the third lens are taken as TL, f, f1, Dg 2-3 , N2, and N3 respectively, the image capturing lens is configured to simultaneously satisfy conditional expressions (1a): 1.0≦TL/f≦1.8, (2a): 0.09<Dg 2-3 /f, (3a): 0.07<|N2−N3|, and (4a): −35≦f1/f≦−2.3.
1. An image capturing lens substantially consisting of a first lens having a negative power, a second lens having a positive power, a third lens having a negative power, a fourth lens having a positive power, and a fifth lens having a positive power, arranged in this order from the object side, wherein:
the image side surface of the fifth lens has an aspherical shape with one or more inflection points and a concave shape toward the image side in a paraxial region; and
the image capturing lens satisfies the following conditional expressions (1a), (2a), (3a), and (4a) simultaneously:
1.0 ≦TL/f≦ 1.8 (1a);
0.09 <Dg 2-3 /f (2a);
0.07 <|N 2 −N 3| (3a); and
−35 ≦f 1 /f≦− 2.3 (4a),
where:
TL is an overall optical length when a distance from the image side surface of the fifth lens to the image plane is represented by an air equivalent length;
f is a focal length of the entire lens system;
f1 is a focal length of the first lens;
Dg 2-3 is a distance (air space) between the image side surface of the second lens and the object side surface of the third lens;
N2 is a refractive index of the optical member constituting the second lens; and
N3 is a refractive index of the optical member constituting the third lens.
2. The image capturing lens of claim 1 , wherein the lens satisfies the following conditional expression (5a):
0.80 ≦f 12 /f≦ 1.40 (5a),
where f12 is a combined focal length of the first and second lenses.
3. The image capturing lens of claim 1 , wherein the lens satisfies the following conditional expression (6a):
54<ν2 (6a),
where ν2 is an Abbe number of the second lens.
4. The image capturing lens of claim 1 , wherein the lens satisfies the following conditional expression (7a):
20<ν3<35 (7a),
where ν3 is an Abbe number of the third lens.
5. The image capturing lens of claim 1 , wherein the lens satisfies the following conditional expression (8a):
−12<( R 1 +R 2)/( R 1 −R 2)<−0.21 (8a),
where:
R1 is a radius of curvature of the object side surface of the first lens (first lens surface); and
R2 is a radius of curvature of the image side surface of the first lens (second lens surface).
6. The image capturing lens of claim 1 , wherein the lens satisfies the following conditional expression (9a):
20<ν1<95 (9a),
where ν1 is an Abbe number of the first lens.
7. The image capturing lens of claim 1 , wherein the lens satisfies the following conditional expression (10a):
0.7 ≦f 4 /f≦ 2.1 (10a),
where f4 is a focal length of the fourth lens.
8. The image capturing lens of claim 1 , wherein the lens satisfies the following conditional expression (11a):
0.25<( Dg 2 +Dg 3)/ f< 0.7 (11a),
where:
Dg2 is a center thickness of the second lens (distance between the object side surface and image side surface of the second lens on the optical axis; actual length); and
Dg3 is a center thickness of the second lens (distance between the object side surface and image side surface of the third lens on the optical axis; actual length).
9. The image capturing lens of claim 1 , wherein the lens satisfies the following conditional expression (12a):
50<ν4<65 (12a),
where ν4 is an Abbe number of the fourth lens.
10. The image capturing lens of claim 1 , wherein the lens satisfies the following conditional expression (13a):
50<ν5<65 (13a),
where ν5 is an Abbe number of the fifth lens.
11. The image capturing lens of claim 1 , wherein the lens satisfies the following conditional expression (14a):
−4<Σ( fj/νj )/ f< 4 (14a),
where Σ(fj/νj)/f is [(f1/ν1)+(f2/ν2)+(f3/ν3)+(f4/ν4)+(f5/ν5)]/f fj is a focal length of the j th lens (where, j=1 to 5); and vj is an Abbe number for the j th lens (where, j=1 to 5).
12. The image capturing lens of claim 1 , wherein the image side surface of the fifth lens has only one extreme point.
13. The image capturing lens of claim 1 , wherein the lens satisfies the following conditional expression (4b):
−30 ≦f 1 /f≦− 4.0 (4b).
14. The image capturing lens of claim 1 , wherein the lens satisfies the following conditional expression (5b):
0.80 ≦f 12 /f≦ 1.30 (5b),
where f12 is a combined focal length of the first and second lenses.
15. The image capturing lens of claim 1 , wherein the lens satisfies the following conditional expression (5c):
0.60 ≦f 12 /f≦ 1.30 (5c),
where f12 is a combined focal length of the first and second lenses.
16. The image capturing lens of claim 1 , wherein the lens satisfies the following conditional expression (6b):
54<ν2<79 (6b),
where ν2 is an Abbe number of the second lens.
17. The image capturing lens of claim 1 , wherein the lens satisfies the following conditional expression (9b):
20<ν1<75 (9b),
where ν1 is an Abbe number of the first lens.
18. The image capturing lens of claim 1 , wherein the lens satisfies the following conditional expression (9c):
50<ν1<65 (9c),
where ν1 is an Abbe number of the first lens.
19. The image capturing lens of claim 1 , wherein the lens satisfies the following conditional expression (14b):
−2<Σ( fj/νj )/ f< 0.5 (14b),
where Σ(fj/νj)/f is [(f1/ν1)+(f2/ν2)+(f3/ν3)+f4/ν4)+(f5/ν5)]/f fj is a focal length of the j th lens (where, j=1 to 5); and vj is an Abbe number for the j th lens (where, j=1 to 5).
20. An image capturing apparatus, comprising the image capturing lens of claim 1 and an image sensor for outputting an image capturing signal obtained by capturing an optical image formed by the image capturing lens.