Imaging lens and imaging apparatus
View Patent ↗An imaging lens is provided and includes: in order from an object side of the imaging lens, a first lens group having a positive power as a whole; a second lens group including a lens in the most object side thereof, the lens having a concave surface on the object side thereof; a third lens group including a cemented lens of a lens having a positive power and a lens having a negative power; and a fourth lens group having a negative power as a whole.
1. An imaging lens comprising: in order from an object side of the imaging lens,
a first lens group having a positive power as a whole;
a second lens group including a lens in the most object side thereof, the lens having a concave surface on the object side thereof;
a stop disposed on the object side from the second lens group;
a third lens group including a cemented lens of a lens having a positive power and a lens having a negative power; and
a fourth lens group having a negative power as a whole,
wherein a lens in the most image side of the second lens group has a convex surface on an image side thereof.
2. The imaging lens according to claim 1 , wherein
the first lens group includes a lens having a convex surface on the object side thereof and having a positive power,
the second lens group includes a cemented lens, the cemented lens including: in order from the object side, a lens having a concave surface on the object side thereof; and a lens having a convex surface on an image side thereof, and
the fourth lens group includes a lens having a concave surface on the object side thereof and having a negative power.
3. The imaging lens according to claim 1 , wherein
the first lens group includes a lens having a convex surface on the object side thereof and having a positive power,
the second lens group includes a meniscus lens having a concave surface on the object side thereof, and
the fourth lens group includes a lens having a concave surface on the object side thereof and having a negative power.
4. The imaging lens according to claim 1 , which satisfies condition (2):
0.3 <|R 2A /R 2B |<2 (2)
wherein R 2A represents a radius of curvature of a surface on the most object side of the second lens group, and R 2B represents a radius of curvature of a surface on the most image side of the second lens group.
5. The imaging lens according to claim 1 , which satisfies condition (3):
| ENP|/L< 0.5 (3)
wherein ENP represents a distance from a surface apex on the most object side of the first lens group to an entrance pupil of the imaging lens, and L represents a distance from a surface on the most object side of the first lens group to an imaging surface of the imaging lens.
6. The imaging lens according to claim 1 , wherein the lens having a positive power in the cemented lens of the third lens group is a biconvex lens, and the cemented lens satisfies conditions (4) and (5):
Nn−Np <0.40 (4)
vp/vn >1.0 (5)
wherein Np and vp represent a refractive index and an Abbe number of the biconvex lens at the d-line, respectively, and Nn and vn represent a refractive index and an Abbe number of the lens having a negative power in the cemented lens of the third lens group at the d-line, respectively.
7. The imaging lens according to claim 1 , which satisfies condition (6):
−6.0 <f 4 /f <−0.2 (6)
wherein f represents a focal length of the imaging lens, and f 4 represents a focal length of the fourth lens group.
8. The imaging lens according to claim 1 , which satisfies condition (1):
2.0 <|f 2 /f |(1)
wherein f represents a focal length of the imaging lens, and f 2 represents a focal length of the second lens group.
9. The imaging lens according to claim 8 , which satisfies condition (2):
0.3 <|R 2A /R 2B |<2 (2)
wherein R 2A represents a radius of curvature of a surface on the most object side of the second lens group, and R 2B represents a radius of curvature of a surface on the most image side of the second lens group.
10. The imaging lens according to claim 9 , further comprising a stop disposed on the object side from the second lens group.
11. The imaging lens according to claim 10 , which satisfies condition (3):
| ENP|/L <0.5 (3)
wherein ENP represents a distance from a surface apex on the most object side of the first lens group to an entrance pupil of the imaging lens, and L represents a distance from a surface on the most object side of the first lens group to an imaging surface of the imaging lens.
12. The imaging lens according to claim 11 , wherein the lens having a positive power in the cemented lens of the third lens group is a biconvex lens, and the cemented lens satisfies conditions (4) and (5):
Nn−Np <0.40 (4)
vp/vn >1.0 (5)
wherein Np and vp represent a refractive index and an Abbe number of the biconvex lens at the d-line, respectively, and Nn and vn represent a refractive index and an Abbe number of the lens having a negative power in the cemented lens of the third lens group at the d-line, respectively.
13. The imaging lens according to claim 12 , which satisfies condition (6):
−6.0 <f 4/ f <−0.2 (6)
wherein f represents a focal length of the imaging lens, and f 4 represents a focal length of the fourth lens group.
14. The imaging lens according to claim 13 , wherein
the first lens group includes a lens having a convex surface on the object side thereof and having a positive power,
the second lens group includes a cemented lens, the cemented lens including: in order from the object side, a lens having a concave surface on the object side thereof; and a lens having a convex surface on an image side thereof, and
the fourth lens group includes a lens having a concave surface on the object side thereof and having a negative power.
15. The imaging lens according to claim 13 , wherein
the first lens group includes a lens having a convex surface on the object side thereof and having a positive power,
the second lens group includes a meniscus lens having a concave surface on the object side thereof, and
the fourth lens group includes a lens having a concave surface on the object side thereof and having a negative power.
16. An imaging apparatus comprising:
an imaging lens according to claim 1 , and
an imaging device for outputting an imaging signal in accordance with an optical image formed by the imaging lens.
17. An imaging apparatus comprising:
an imaging lens according to claim 14 , and
an imaging device for outputting an imaging signal in accordance with an optical image formed by the imaging lens.
18. The imaging lens according to claim 1 , wherein the lens having a positive power in the cemented lens of the third lens group is a biconvex lens, and the cemented lens satisfies condition (4):
0.01 ≦Nn−Np <0.40 (4)
wherein Np represents a refractive index of the biconvex lens at the d-line, and Nn represents a refractive index of the lens having a negative power in the cemented lens of the third lens group at the d-line.
19. The imaging lens according to claim 1 , wherein the lens having a positive power in the cemented lens of the third lens group is a biconvex lens, and the cemented lens satisfies condition (5):
vp/vn >1.56 (5)
wherein vp represents an Abbe number of the biconvex lens at the d-line, and vn represents an Abbe number of the lens having a negative power in the cemented lens of the third lens group at the d-line.