Imaging lens and imaging device
An imaging lens consists of a negative first lens, a negative second lens, a third lens of a plano-convex shape having a convex surface directed toward an object side or of a positive meniscus shape having a convex surface directed toward the object side, and a fourth lens of a plano-convex shape having a convex surface directed toward an image side or of a positive meniscus shape having a convex surface directed toward the image side, which are arranged in this order from the object side. Further, the following conditional formula (1) is satisfied: 2.25<ν d 2/ν d 3 (1), where νd2: an Abbe number of a material of the second lens for d-line, and νd3: an Abbe number of a material of the third lens for d-line.
1. An imaging lens consisting of:
a negative first lens;
a negative second lens;
a third lens of a plano-convex shape having a convex surface directed toward an object side or of a positive meniscus shape having a convex surface directed toward the object side; and
a fourth lens of a plano-convex shape having a convex surface directed toward an image side or of a positive meniscus shape having a convex surface directed toward the image side, which are arranged in this order from the object side,
wherein the following conditional formula (1) is satisfied:
2.25< νd 2 /νd 3 (1), where
νd2: an Abbe number of a material of the second lens for d-line, and
νd3: an Abbe number of a material of the third lens for d-line.
2. The imaging lens, as defined in claim 1 , wherein the following conditional formula (1-4) is satisfied:
2.25 <νd 2 /νd 3<2.8 (1-4).
3. The imaging lens, as defined in claim 1 , wherein the following conditional formula (1-6) is satisfied:
2.35 <νd 2 /νd 3<2.6 (1-6).
4. The imaging lens, as defined in claim 1 , wherein the following conditional formula (13) is satisfied:
8 <R 1 /f< 50 (13), where
R1: a curvature radius of an object-side surface of the first lens, and
f: a focal length of an entire system.
5. The imaging lens, as defined in claim 1 , wherein the following conditional formula (14) is satisfied:
2 <R 6 /f (14), where
R6: a curvature radius of an image-side surface of the third lens, and
f: a focal length of an entire system.
6. The imaging lens, as defined in claim 1 , wherein the following conditional formula (15) is satisfied:
0.5 <D 3 /f< 5.0 (15), where
D3: a center thickness of the second lens, and
f: a focal length of an entire system.
7. The imaging lens, as defined in claim 1 , wherein the following conditional formula (16) is satisfied:
0.1≦( R 1 −R 2)/( R 1 +R 2)≦1.0 (16), where
R1: a curvature radius of an object-side surface of the first lens, and
R2: a curvature radius of an image-side surface of the first lens.
8. The imaging lens, as defined in claim 1 , wherein the following conditional formula (17) is satisfied:
0.2 <R 1 /L< 3.0 (17), where
R1: a curvature radius of an object-side surface of the first lens, and
L: a distance from a vertex of an object-side surface of the first lens to an image plane.
9. The imaging lens, as defined in claim 1 , wherein the following conditional formula (18) is satisfied:
−1.0≦( R 5 −R 6)/( R 5 +R 6)≦−0.1 (18), where
R5: a curvature radius of an object-side surface of the third lens, and
R6: a curvature radius of an image-side surface of the third lens.
10. The imaging lens, as defined in claim 1 , wherein the following conditional formula (19) is satisfied:
−0.8 <f/f 123<0.8 (19), where
f: a focal length of an entire system, and
f123: a combined focal length of the first lens, the second lens and the third lens.
11. The imaging lens, as defined in claim 1 , wherein the following conditional formula (20) is satisfied:
1≦ f 34/ f≦ 10 (20), where
f34: a combined focal length of the third lens and the fourth lens, and
f: a focal length of an entire system.
12. The imaging lens, as defined in claim 1 , wherein a material constituting the third lens is polycarbonate.
13. An imaging apparatus comprising:
the imaging lens, as defined in claim 1 , mounted thereon.
14. An imaging lens consisting of:
a negative first lens;
a negative second lens;
a third lens of a plano-convex shape having a convex surface directed toward an object side or of a positive meniscus shape having a convex surface directed toward the object side; and
a fourth lens of a plano-convex shape having a convex surface directed toward an image side or of a positive meniscus shape having a convex surface directed toward the image side, which are arranged in this order from the object side,
wherein the following conditional formula (2) is satisfied:
0.09 <Nd 3 −Nd 2 (2), where
Nd2: a refractive index of a material of the second lens for d-line, and
Nd3: a refractive index of a material of the third lens for d-line.
15. The imaging lens, as defined in claim 14 , wherein the following conditional formula (2-2) is satisfied:
0.09 <Nd 3 −Nd 2<0.16 (2-2).
16. An imaging lens consisting of:
a negative first lens;
a negative second lens;
a third lens of a plano-convex shape having a convex surface directed toward an object side or of a positive meniscus shape having a convex surface directed toward the object side; and
a fourth lens of a plano-convex shape having a convex surface directed toward an image side or of a positive meniscus shape having a convex surface directed toward the image side, which are arranged in this order from the object side,
wherein the following conditional formula (8) is satisfied:
8.0 <L/f< 13.9 (8), where
L: a distance from a vertex of an object-side surface of the first lens to an image plane, and
f: a focal length of an entire system.
17. The imaging lens, as defined in claim 16 , wherein the following conditional formula (8-2) is satisfied:
9.0 <L/f< 13.5 (8-2).
18. The imaging lens, as defined in claim 16 , wherein the following conditional formula (8-3) is satisfied:
10 <L/f< 13 (8-3).
19. An imaging lens consisting of:
a negative first lens;
a negative second lens of a biconcave shape;
a third lens of a plane-convex shape having a convex surface directed toward an object side or of a positive meniscus shape having a convex surface directed toward the object side; and
a fourth lens of a plane-convex shape having a convex surface directed toward an image side or of a positive meniscus shape having a convex surface directed toward the image side, which are arranged in this order from the object side,
wherein the following conditional formula (9) is satisfied:
1.0 <Bf/f< 3.0 (9), where
Bf: a distance from a vertex of an image-side surface of a most-image-side lens to an image plane (a distance in air), and
f: a focal length of an entire system.
20. The imaging lens, as defined in claim 19 , wherein the following conditional formula (9-2) is satisfied:
1.5 <Bf/f< 2.5 (9-2).
21. The imaging lens, as defined in claim 19 , wherein the following conditional formula (9-3) is satisfied:
1.7 <Bf/f< 2.3 (9-3).