Imaging lens and imaging apparatus

• US 8,964,312 B2
• Filed: 05/09/2014
• Issued: 02/24/2015
• Est. Priority Date: 11/09/2011
• Status: Active Grant

• Current Assignee: Fujifilm Corporation (Fujifilm Holdings Corporation)
• Original Assignee: Fujifilm Corporation (Fujifilm Holdings Corporation)
• Inventors: Kawamura, Daiki
• Primary Examiner(s): Choi, William
• Assistant Examiner(s): RAKOWSKI, CARA E
• Application Number:
  US14/273,898
• Publication Number:
  US 20140268367A1
• Time in Patent Office: 291 Days
• Field of Search: 359/781, 359/782, 359/691, 359/686, 359/793, 359/794, 359/771, 359680-682, 359/708, 359713-717, 359749-753, 359754-756, 359/761, 359763-770, 359/791, 359/796
• US Class Current: 359/793
• CPC Class Codes: G02B 13/0045 having five or more lenses
• CPC Class Codes: G02B 13/04 Reversed telephoto objectives
• CPC Class Codes: G02B 13/18 with lenses having one or more non-spherical faces, e.g. for reducing geometrical aberration G02B13/002 takes precedence
• CPC Class Codes: G02B 9/04 having two components only
• CPC Class Codes: G02B 9/58 arranged - + + -

Abstract

An imaging lens includes: a first lens group; an aperture stop; and a second lens group having a positive power, in this order from an object side. The first lens group includes a first lens having a negative power and a second lens having a positive power. The imaging lens satisfies Conditional Formulae (1), (2), and (3):
−0.50<f/f1<0.20  (1)
0.08<d12/f<0.35  (2)
2.5<TL/Y<4.0  (3)

• • wherein f is the focal length of the entire system, f1 is the focal length of the first lens group, d12 is a distance along an optical axis from the image side lens surface of the first lens to the object side lens surface of the second lens, TL is the distance along the optical axis from the most object side lens surface within the first lens group to an imaging surface Sim, and Y is a maximum image height, when focused on an object at infinity.

Claims

1. An imaging lens, substantially consisting of:

a first lens group having a negative or a positive refractive power;

an aperture stop; and

a second lens group having a positive refractive power, provided in this order from an object side;

the first lens group being constituted by an 11 lens group having a negative refractive power and a 12 lens group having a positive refractive power, which are constituted by 3 or fewer lenses as a whole, provided in this order from the object side;

the 11 lens group being constituted by a single first lens, and the 12 lens group being constituted by a single lens provided at a spatial interval from the first lens or by a cemented lens, which is a positive lens component, provided at a spatial interval from the first lens;

the second lens group substantially consisting of a 21 lens group having a positive refractive power and a 22 lens group having a negative refractive power, provided in which order from the object side;

the 21 lens group having at least one positive lens and at least one negative lens;

the 22 lens group substantially consisting of a total of three lenses including at least one positive lens and at least one negative lens; and

the imaging lens satisfying Conditional Formulae (1), (2), and (3) below;

−

0.50<

f/f1<

0.20 

 

(1)

0.08<

d12/f<

0.35 

 

(2)

2.5<

TL/Y<

4.0 

 

(3)

wherein f is the focal length of the entire lens system, f1 is the focal length of the first lens group, d12 is a distance along an optical axis from the lens surface toward an image side of the first lens within the first lens group to the lens surface most toward the object side of the positive lens component, TL is the distance along the optical axis from the lens surface most toward the object side within the first lens group to the imaging surface, and Y is a maximum image height, when focused on an object at infinity.

2. An imaging lens as defined in claim 1 that satisfies at least one of Conditional Formulae (1′

), (2′

), and (3′

) below;

−

0.45<

f/f1<

0.15 

 

(1′

)

0.10<

d12/f<

0.32 

 

(2′

)

1.7<

TL/Y<

3.8 

 

(3′

).

3. An imaging lens as defined in claim 1 that satisfies Conditional Formula (1″

) below;

0.42<

f/f1<

0.10 

 

(1″

).

4. An imaging lens as defined in claim 1, wherein:

the 22 lens group is constituted only by a sub lens group having a negative refractive power and a single positive lens, provided in this order from the object side.

5. An imaging lens as defined in claim 1 that satisfies Conditional Formula (4) below:

1.75<

Nd22 

 

(4)

wherein Nd22 is the average value of the refractive indices of all of the lenses within the 22 lens group with respect to the d line.

6. An imaging lens as defined in claim 5 that satisfies Conditional Formula (4′

) below;

1.78<

Nd22 

 

(4′

).

7. An imaging lens as defined in claim 1, wherein:

a lens having at least one surface which is aspherical surface is provided within the 22 lens group.

8. An imaging lens as defined claim 1, wherein:

a negative lens having a surface toward the object side which is concave toward the object side in a paraxial region, and of which at least one surface is an aspherical surface, is provided within the 22 lens group.

9. An imaging lens as defined in claim 1, wherein:

the 21 lens group is constituted by a total of three lenses, which are a positive lens and a negative lens cemented together, and a single positive lens.

10. An imaging lens as defined in claim 1, wherein:

a positive lens having at least one aspherical surface is provided within the 21 lens group.

11. An imaging lens as defined in claim 1 that satisfies Conditional Formula (5) below:

1.1<

TL/Σ

d<

1.5 

 

(5)

wherein Σ

d is the distance along the optical axis from the lens surface most toward the object side within the first lens group to the lens surface most toward the image side in the second lens group, and TL is the distance along the optical axis from the lens surface most toward the object side within the first lens group to the imaging surface, when focused on an object at infinity.

12. An imaging lens as defined in claim 11 that satisfies Conditional Formula (5′

) below;

1.20<

TL/Σ

d<

1.45 

 

(5′

).

13. An imaging lens as defined in claim 1 that satisfies Conditional Formula (6) below:

0.8<

|f1n|/f<

1.2 

 

(6)

wherein f1n is the focal length of the first lens, and f is the focal length of the entire lens system.

14. An imaging lens as defined in claim 13 that satisfies Conditional Formula (6′

) below;

0.82<

|f1n|/f<

1.15 

 

(6′

).

15. An imaging lens as defined in claim 1 that satisfies Conditional Formula (7) below:

2.0<

(R21+R12)/(R21−

R12)<

4.0 

 

(7)

wherein R12 is the radius of curvature of the surface toward the image side of the first lens, and R21 is the radius of curvature of the surface most toward the object side of the positive lens component.

16. An imaging lens as defined in claim 15 that satisfies Conditional Formula (7′

) below;

2.2<

(R21+R12)/(R21−

R12)<

3.8 

 

(7′

).

17. An imaging lens as defined in claim 1, wherein:

the 22 lens group is constituted by three lenses, which are a negative lens, a negative lens, and a positive lens, provided in this order from the object side.

18. An imaging lens as defined in claim 1, wherein:

the 12 lens group is constituted only by a single positive lens.

19. An imaging apparatus equipped with an imaging lens as defined in claim 1.