Imaging lens and image pickup apparatus

• US 7,746,572 B2
• Filed: 08/20/2008
• Issued: 06/29/2010
• Est. Priority Date: 08/21/2007
• Status: Active Grant

• Current Assignee: Tianjin OFILM Opto Electronics Co., Ltd.
• Original Assignee: Fujinon Corporation (Fujifilm Holdings Corporation)
• Inventors: Asami, Taro
• Primary Examiner(s): Spector; David N
• Application Number:
  US12/195,029
• Publication Number:
  US 20090052061A1
• Time in Patent Office: 678 Days
• Field of Search: 359/748, 359/753, 359/771, 359/781, 359/783
• US Class Current: 359/783
• CPC Class Codes: G02B 13/04 Reversed telephoto objectives
• CPC Class Codes: G02B 9/34 having four components only

Abstract

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 ν₂, 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:
ν₂>30  (1),
2.5<L/f<4.0  (2), and
0.5<Bf/f<1.3  (3).

Claims

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 f₃ and the focal length of the imaging lens is f, the following conditional expression (4) is satisfied:

1<

f₃/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 D₂ and the focal length of the imaging lens is f, the following conditional expression (5) is satisfied:

0.01<

D₂/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 f₁, the following conditional expression (6) is satisfied:

−

1.5<

d/f₁<

−

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 D₂ and the focal length of the imaging lens is f, the following conditional expression (5) is satisfied:

0.01<

D₂/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 f₁, the following conditional expression (6) is satisfied:

−

1.5<

d/f₁<

−

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 f₁, the following conditional expression (6) is satisfied:

−

1.5<

d/f₁<

−

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.