Imaging lens and image pickup apparatus
View Patent ↗An imaging lens comprises, in order from an object side: a first lens that has a negative refractive power and is convex toward the object side; a second lens that has a positive refractive power and is a meniscus lens convex toward the object side; a stop; a third lens that has a positive refractive power and is convex toward an image side; and a cemented lens that has a positive refractive power as a whole and is formed by cementing a fourth lens and a fifth lens, wherein assuming that an Abbe number of the second lens with respect to d-line is ν 2 , a distance on an optical axis from a vertex of a surface of the first lens facing toward the object side to an image plane of the imaging lens is L, a focal length of the imaging lens is f, and a back focus of the imaging lens is Bf, the following conditional expressions (1) to (3) are satisfied: ν 2 >30 (1), 2.5< L/f< 4.0 (2), and 0.5< Bf/f< 1.3 (3).
1. An imaging lens comprising, in order from an object side:
a first lens that has a negative refractive power and is convex toward the object side;
a second lens that has a positive refractive power and is a meniscus lens convex toward the object side;
a stop;
a third lens that has a positive refractive power and is convex toward an image side; and
a cemented lens that has a positive refractive power as a whole and is formed by cementing a fourth lens and a fifth lens,
wherein assuming that an Abbe number of the second lens with respect to d-line is ν 2 , a distance on an optical axis from a vertex of a surface of the first lens facing toward the object side to an image plane of the imaging lens is L, a focal length of the imaging lens is f, and a back focus of the imaging lens is Bf, the following conditional expressions (1) to (3) are satisfied:
ν 2 >30 (1),
2.5< L/f< 4.0 (2), and
0.5< Bf/f< 1.3 (3).
2. The imaging lens according to claim 1 , wherein assuming that a focal length of the third lens is f 3 and the focal length of the imaging lens is f, the following conditional expression (4) is satisfied:
1< f 3 /f< 4 (4).
3. The imaging lens according to claim 1 ,
wherein assuming that an on-axis airspace between the first lens and the second lens is D 2 and the focal length of the imaging lens is f, the following conditional expression (5) is satisfied:
0.01< D 2 /f< 0.7 (5).
4. The imaging lens according to claim 1 ,
wherein assuming that a distance on the optical axis from a vertex of a surface of the first lens facing toward the image side to the stop is d and a focal length of the first lens is f 1 , the following conditional expression (6) is satisfied:
−1.5 <d/f 1 <−0.1 (6).
5. The imaging lens according to claim 1 ,
wherein assuming that an Abbe number of the fourth lens with respect to d-line is ν 4 and an Abbe number of the fifth lens with respect to d-line is ν 5 , the following conditional expression (7) is satisfied:
ν 4 /ν 5 >1.5 (7).
6. The imaging lens according to claim 1 ,
wherein a thickness of the center of the first lens is 1 mm or more.
7. An image pickup apparatus comprising:
the imaging lens according to claim 1 ; and
an image pickup device that converts an optical image formed by the imaging lens into an electric signal.
8. The imaging lens according to claim 2 ,
wherein assuming that an on-axis airspace between the first lens and the second lens is D 2 and the focal length of the imaging lens is f, the following conditional expression (5) is satisfied:
0.01 <D 2 /f <0.7 (5).
9. The imaging lens according to claim 3 ,
wherein assuming that a distance on the optical axis from a vertex of a surface of the first lens facing toward the image side to the stop is d and a focal length of the first lens is f 1 , the following conditional expression (6) is satisfied:
−1.5 <d/f 1 <−0.1 (6).
10. The imaging lens according to claim 4 ,
wherein assuming that an Abbe number of the fourth lens with respect to d-line is ν 4 and an Abbe number of the fifth lens with respect to d-line is ν 5 , the following conditional expression (7) is satisfied:
ν 4 /ν 5 >1.5 (7).
11. The imaging lens according to claim 5 ,
wherein a thickness of the center of the first lens is 1 mm or more.
12. The imaging lens according to claim 8 ,
wherein assuming that a distance on the optical axis from a vertex of a surface of the first lens facing toward the image side to the stop is d and a focal length of the first lens is f 1 , the following conditional expression (6) is satisfied:
−1.5< d/f 1 <−0.1 (6).
13. The imaging lens according to claim 9 ,
wherein assuming that an Abbe number of the fourth lens with respect to d-line is ν 4 and an Abbe number of the fifth lens with respect to d-line is ν 5 , the following conditional expression (7) is satisfied:
ν 4 /ν 5 >1.5 (7).
14. The imaging lens according to claim 10 ,
wherein a thickness of the center of the first lens is 1 mm or more.
15. The imaging lens according to claim 12 ,
wherein assuming that an Abbe number of the fourth lens with respect to d-line is ν 4 and an Abbe number of the fifth lens with respect to d-line is ν 5 , the following conditional expression (7) is satisfied:
ν 4 /ν 5 >1.5 (7).
16. The imaging lens according to claim 13 ,
wherein a thickness of the center of the first lens is 1 mm or more.
17. The imaging lens according to claim 15 ,
wherein a thickness of the center of the first lens is 1 mm or more.
18. An image pickup apparatus comprising:
the imaging lens according to claim 17 ; and
an image pickup device that converts an optical image formed by the imaging lens into an electric signal.