Imaging lens and imaging apparatus
An imaging lens consists of negative first lens, negative second lens of a biconcave shape, 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 (11) is satisfied: 3.1< R 4/ f (11), where R4: a curvature radius of an image-side surface of the second lens, and f: a focal length of an entire system.
1. An imaging lens consisting of:
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 (11) is satisfied:
3.1 <R 4 /f (11),
where
R4: a curvature radius of an image-side surface of the second lens, and
f: a focal length of an entire system.
2. The imaging lens, as defined in claim 1 , wherein the following conditional formula (11-2) is satisfied:
3.1 <R 4 /f< 50.0 (11-2).
3. The imaging lens, as defined in claim 1 , wherein the following conditional formula (11-6) is satisfied:
3.8 <R 4 /f< 6.0 (11-6).
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: 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
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: the focal length of the 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: 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 consisting of:
a negative first lens;
a second lens of a negative meniscus shape having a convex surface directed toward an object side;
a third lens of a plano-convex shape having a convex surface directed toward the 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 (11-1) is satisfied:
R 4 /f< 1.3 (11-1),
where
R4: a curvature radius of an image-side surface of the second lens, and
f: a focal length of an entire system.
15. The imaging lens, as defined in claim 14 , wherein the following conditional formula (11-7) is satisfied:
0.1 <R 4 /f< 1.3 (11-7).
16. The imaging lens, as defined in claim 14 , wherein the following conditional formula (11-10) is satisfied:
0.8 <R 4 /f< 1 (11-10).