Imaging lens and imaging apparatus
An imaging lens includes negative first lens, negative second lens, 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 (6) is satisfied: 0.75≦( R 8− R 9)/( R 8+ R 9)≦1.0 (6), where R8: a curvature radius of an object-side surface of the fourth lens, and R9: a curvature radius of an image-side surface of the fourth 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 (6) is satisfied:
0.75≦( R 8− R 9)/( R 8+ R 9)≦1.0 (6), where
R8: a curvature radius of an object-side surface of the fourth lens, and
R9: a curvature radius of an image-side surface of the fourth lens.
2. The imaging lens, as defined in claim 1 , wherein the following conditional formula (6-3) is satisfied:
0.81≦( R 8− R 9)/( R 8+ R 9)≦0.95 (6-3).
3. The imaging lens, as defined in claim 1 , wherein the following conditional formula (13) is satisfied:
8< R 1/ f< 50 (13),
R1: a curvature radius of an object-side surface of the first lens, and
f: a focal length of an entire system.
4. 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.
5. 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.
6. 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.
7. 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.
8. 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.
9. 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.
10. 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.
11. The imaging lens, as defined in claim 1 , wherein a material constituting the third lens is polycarbonate.
12. An imaging apparatus comprising:
the imaging lens, as defined in claim 1 , mounted thereon.
13. 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 (6-1) is satisfied:
0.60≦( R 8− R 9)/( R 8+ R 9)≦1.0 (6-1), where
R8: a curvature radius of an object-side surface of the fourth lens, and
R9: a curvature radius of an image-side surface of the fourth lens.
14. The imaging lens, as defined in claim 13 , wherein the following conditional formula (6-5) is satisfied:
0.7≦( R 8− R 9)/( R 8+ R 9)≦1.0 (6-5).
15. 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 (7) is satisfied:
6.2<| R 8 /f| (7), where
R8: a curvature radius of an object-side surface of the fourth lens, and
f: a focal length of an entire system.
16. The imaging lens, as defined in claim 15 , wherein the following conditional formula (7-2) is satisfied:
7.0<| R 8/ f| (7-2).
17. The imaging lens, as defined in claim 15 , wherein the following conditional formula (7-5) is satisfied:
15<| R 8/ f|< 500 (7-5).
18. 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 (7-1) is satisfied:
4.5<| R 8 /f| (7-1), where
R8: a curvature radius of an object-side surface of the fourth lens, and
f: a focal length of an entire system.
19. The imaging lens, as defined in claim 18 , wherein the following conditional formula (7-6) is satisfied:
5<| R 8 /f| (7-6).
20. The imaging lens, as defined in claim 18 , wherein the following conditional formula (7-9) is satisfied:
6.5<| R 8/ f|< 500 (7-9).