Imaging lens and imaging apparatus
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 (3) is satisfied: 1.0<| f 2/ f |<2.6 (3), where f: a focal length of an entire system, and f2: a focal length of the second lens.
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 (3) is satisfied:
1.0<| f 2/ f|< 2.4 (3), where
f: a focal length of an entire system, and
f2: a focal length of the second lens.
2. The imaging lens, as defined in claim 1 , wherein the following conditional formula (3-3) is satisfied:
1.2<| f 2/ f|< 2.4 (3-3).
3. The imaging lens, as defined in claim 1 , wherein the following conditional formula (3-4) is satisfied:
1.5<| f 2/ f|< 2.4 (3-4).
4. The imaging lens, as defined in claim 1 , wherein the following conditional formula (3-5) is satisfied:
1.7<| f 2/ f|< 2.2 (3-5).
5. The imaging lens, as defined in claim 1 , wherein the following conditional formula (3-8) is satisfied:
1.9<| f 2/ f|< 2.4 (3-8).
6. 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: the focal length of the entire system.
7. 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: the focal length of the entire system.
8. 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.
9. 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.
10. 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.
11. 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.
12. 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.
13. 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.
14. The imaging lens, as defined in claim 1 , wherein a material constituting the third lens is polycarbonate.
15. An imaging apparatus comprising:
the imaging lens, as defined in claim 1 , mounted thereon.
16. 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 (10) is satisfied:
1.5<( D 4+ D 5)/ f< 3.2 (10), where
D4: a distance in air on an optical axis between the second lens and the third lens,
D5: a center thickness of the third lens, and
f: a focal length of an entire system.
17. The imaging lens, as defined in claim 16 , wherein the following conditional formula (10-1) is satisfied:
2.0<( D 4+ D 5)/ f< 3.2 (10-1).
18. The imaging lens, as defined in claim 16 , wherein the following conditional formula (10-2) is satisfied:
2.3<( D 4+ D 5)/ f< 3 (10-2).
19. The imaging lens, as defined in claim 16 , wherein the following conditional formula (10-3) is satisfied:
2.5<( D 4+ D 5)/ f< 2.9 (10-3).
20. 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 (3-1) is satisfied:
1.0<| f 2/ f|< 2.7 (3-1), where
f: a focal length of an entire system, and
f2: a focal length of the second lens.