Imaging lens and imaging apparatus
An imaging lens includes 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 (4) is satisfied: 1.0< D 2/ f <2.5 (4), where f: a focal length of an entire system, and D2: a distance on an optical axis between the first lens and the second lens.
1. An imaging lens comprising:
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 (4) is satisfied:
1.0 <D 2 /f< 2.5 (4), where
f: a focal length of an entire system, and
D 2 : a distance on an optical axis between the first lens and the second lens.
2. The imaging lens, as defined in claim 1 , wherein the following conditional formula (4-2) is satisfied:
1.5 <D 2 /f< 2.5 (4-2).
3. The imaging lens, as defined in claim 1 , wherein the following conditional formula (4-3) is satisfied:
2 <D 2 /f< 2.4 (4-3).
4. The imaging lens, as defined in claim 1 , wherein the following conditional formula (13) is satisfied:
8 <R 1 /f< 50 (13), where
R 1 : a curvature radius of an object-side surface of the first lens, and
f: the focal length of the 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
R 6 : a curvature radius of an image-side surface of the third lens, and
f: the focal length of the 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
D 3 : a center thickness of the second lens, and
f: the focal length of the 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
R 1 : a curvature radius of an object-side surface of the first lens, and
R 2 : 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
R 1 : 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
R 5 : a curvature radius of an object-side surface of the third lens, and
R 6 : 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: the focal length of the entire system, and
f 123 : 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
f 34 : a combined focal length of the third lens and the fourth lens, and
f: the focal length of the 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 comprising:
a negative first lens;
a negative second lens of a biconcave shape;
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 (4-1) is satisfied:
1.0 <D 2 /f< 2.8 (4-1), where
f: a focal length of an entire system, and
D 2 : a distance on an optical axis between the first lens and the second lens.
15. The imaging lens, as defined in claim 14 , wherein the following conditional formula (4-5) is satisfied:
1.5 <D 2 /f< 2.8 (4-5).
16. The imaging lens, as defined in claim 14 , wherein the following conditional formula (4-7) is satisfied:
1.5 <D 2 /f< 2.5 (4-7).
17. The imaging lens, as defined in claim 14 , wherein the following conditional formula (4-8) is satisfied:
2 <D 2 /f< 2.3 (4-8).
18. An imaging lens comprising:
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 (5) is satisfied:
1.5 <f 3 /f< 3.0 (5), where
f: a focal length of an entire system, and
f 3 : a focal length of the third lens.
19. The imaging lens, as defined in claim 18 , wherein the following conditional formula (5-7) is satisfied:
2.2 <f 3 /f< 2.9 (5-7).
20. An imaging lens comprising:
a negative first lens;
a negative second lens of a biconcave shape;
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 (5-1) is satisfied:
1.5 <f 3 /f< 4.6 (5-1), where
f: a focal length of an entire system, and
f 3 : a focal length of the third lens.
21. The imaging lens, as defined in claim 20 , wherein the following conditional formula (5-4) is satisfied:
1.5 <f 3 /f< 3.5 (5-4).
22. The imaging lens, as defined in claim 20 , wherein the following conditional formula (5-5) is satisfied:
2.2 <f 3 /f< 3.2 (5-5).