Imaging lens and imaging apparatus
View Patent ↗An imaging lens substantially consists of six lenses of a negative first lens, a negative second lens, a positive third lens, a positive fourth lens, a negative fifth lens and a positive sixth lens in this order from an object side. An object-side surface of the second lens has a shape having negative refractive power at a center, and including a part having positive refractive power in an area between the center and an effective diameter edge, and having negative refractive power at the effective diameter edge (concave shape facing the object side), and the refractive power at the effective diameter edge being weaker than the refractive power at the center. Further, an object-side surface of the third lens is convex toward the object side. Further, a predetermined conditional formula about a combined focal length of the first lens, the second lens and the third lens is satisfied.
1. An imaging lens substantially consisting of six lenses of a negative first lens, a negative second lens, a positive third lens, a positive fourth lens, a negative fifth lens and a positive sixth lens in this order from an object side,
wherein an object-side surface of the second lens has a shape having negative refractive power at a center, and including a part having positive refractive power in an area between the center and an effective diameter edge, and having negative refractive power at the effective diameter edge, and the refractive power at the effective diameter edge being weaker than the refractive power at the center, and
wherein an object-side surface of the third lens is convex toward the object side, and
wherein the following conditional formulas (17-4), (14-3) and (20) are satisfied:
−3.5 <f 123 /f<− 1.0 (17-4);
0.5≦( R 3 +R 4)/( R 3 −R 4)≦0.80 (14-3); and
1.0 <f 4 /f< 4.0 (20), where
f123: a combined focal length of the first lens, the second lens and the third lens,
f: a focal length of an entire system,
R3: a curvature radius of an object-side surface of the second lens,
R4: a curvature radius of an image-side surface of the second lens, and
f4: a focal length of the fourth lens.
2. The imaging lens, as defined in claim 1 , wherein the following conditional formula (11) is satisfied:
9 <L/f< 16 (11), where
L: a length from an object-side surface of the first lens to an image plane on an optical axis when a back focus portion is a distance in air, and
f: a focal length of an entire system.
3. The imaging lens, as defined in claim 2 , wherein the following conditional formula (11-3) is satisfied:
12.5 <L/f< 15.0 (11-3), where
L: a length from an object-side surface of the first lens to an image plane on an optical axis when a back focus portion is a distance in air, and
f: a focal length of an entire system.
4. The imaging lens, as defined in claim 1 , wherein the following conditional formula (12) is satisfied:
1 <Bf/f< 3 (12), where
Bf: a length from an image-side surface of a most image-side lens to an image plane on an optical axis when the length is a distance in air, and
f: a focal length of an entire system.
5. The imaging lens, as defined in claim 4 , wherein the following conditional formula (12-2) is satisfied:
1.7 <Bf/f< 2.3 (12-2), where
Bf: a length from an image-side surface of a most image-side lens to an image plane on an optical axis when the length is a distance in air, and
f: a focal length of an entire system.
6. The imaging lens, as defined in claim 1 , wherein the following conditional formula (13) is satisfied:
vd 3 +vd 5<50.0 (13), where
vd3: an Abbe number of the material of the third lens for d-line, and
vd5: an Abbe number of the material of the fifth lens for d-line.
7. The imaging lens, as defined in claim 6 , wherein the following conditional formula (13-2) is satisfied:
38.0 <vd 3 +vd 5<48.0 (13-2), where
vd3: an Abbe number of the material of the third lens for d-line, and
vd5: an Abbe number of the material of the fifth lens for d-line.
8. The imaging lens, as defined in claim 1 , wherein the following conditional formula (15) is satisfied:
−10≦( R 5 +R 6)/( R 5 −R 6)≦−1 (15), 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 8 , wherein the following conditional formula (15-3) is satisfied:
−3.5≦( R 5 +R 6)/( R 5 −R 6)≦−1.3 (15-3), 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 (16) is satisfied:
1.1≦( R 1 +R 2)/( R 1 −R 2)≦3.0 (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.
11. The imaging lens, as defined in claim 10 , wherein the following conditional formula (16-2) is satisfied:
1.3≦( R 1 +R 2)/( R 1 −R 2)≦2.0 (16-2), 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.
12. The imaging lens, as defined in claim 1 , wherein the following conditional formula (17-3) is satisfied:
−3.2 <f 123 /f<− 1.8 (17-3), where
f123: a combined focal length of the first lens, the second lens and the third lens, and
f: a focal length of an entire system.
13. The imaging lens, as defined in claim 1 , wherein the following conditional formula (18) is satisfied:
2 <f 3 /f< 12 (18), where
f3: a focal length of the third lens, and
f: a focal length of an entire system.
14. The imaging lens, as defined in claim 13 , wherein the following conditional formula (18-3) is satisfied:
3.5 <f 3 /f< 10 (18-3), where
f3: a focal length of the third lens, and
f: a focal length of an entire system.
15. The imaging lens, as defined in claim 1 , wherein the following conditional formula (19) is satisfied:
0.01 <D 9 /f< 0.5 (19), where
D9: an air space between the fourth lens and the fifth lens on an optical axis, and
f: a focal length of an entire system.
16. The imaging lens, as defined in claim 15 , wherein the following conditional formula (19-1) is satisfied:
0.05 <D 9 /f< 0.3 (19-1), where
D9: an air space between the fourth lens and the fifth lens on an optical axis, and
f: a focal length of an entire system.
17. The imaging lens, as defined in claim 1 , wherein the following conditional formula (20-1) is satisfied:
1.5 <f 4 /f< 3.0 (20-1), where
f4: a focal length of the fourth lens, and
f: a focal length of an entire system.
18. The imaging lens, as defined in claim 1 , wherein the following conditional formula (21) is satisfied:
2.5 <ER 1 /f< 7.5 (21), where
ER1: an effective radius of an object-side surface of the first lens, and
f: a focal length of an entire system.
19. The imaging lens, as defined in claim 18 , wherein the following conditional formula (21-1) is satisfied:
2.5 <ER 1 /f< 8 (21-1), where
ER1: an effective radius of an object-side surface of the first lens, and
f: a focal length of an entire system.
20. The imaging lens, as defined in claim 18 , wherein the following conditional formula (21-4) is satisfied:
4.0 <ER 1 /f< 6.5 (21-4), where
ER1: an effective radius of an object-side surface of the first lens, and
f: a focal length of an entire system.
21. The imaging lens, as defined in claim 1 , wherein a stop is arranged between the third lens and the fourth lens.
22. An imaging apparatus comprising:
the imaging lens, as defined in claim 1 , mounted thereon.