Zoom lens and imaging apparatus

Patent metadata

Field	Value
Publication number	US-9383559-B2
Application number	US-201514629550-A
Country	US
Kind code	B2
Filing date	Feb 24, 2015
Priority date	Feb 26, 2014
Publication date	Jul 5, 2016
Grant date	Jul 5, 2016

Abstract

A zoom lens consists essentially of, in order from the object side, a positive first lens group, a positive second lens group, a negative third lens group, a negative fourth lens group, and a positive fifth lens group. During magnification change from the wide-angle end to the telephoto end, the first lens group and the fifth lens group are fixed relative to the image plane, and the second lens group, the third lens group, and the fourth lens group are moved along the optical axis direction to change distances between the lens groups.

First claim

What is claimed is:

1. A zoom lens consisting essentially of five lens groups consisting of, in order from an object side:
a first lens group having a positive refractive power;
a second lens group having a positive refractive power;
a third lens group having a negative refractive power;
a fourth lens group having a negative refractive power; and
a fifth lens group having a positive refractive power,
wherein, during magnification change from a wide-angle end to a telephoto end, the first lens group and the fifth lens group are fixed relative to an image plane, and the second lens group, the third lens group, and the fourth lens group are moved along an optical axis direction to change distances between the lens groups.

2. The zoom lens as claimed in claim 1 , wherein the condition expression (1) below is satisfied:
5< f 2/ fw   (1),

where f 2 is a focal length of the second lens group, and fw is a focal length of the entire system at the wide-angle end.

3. The zoom lens as claimed in claim 1 , wherein the condition expression (2) below is satisfied:
0.005<Δ G 2 m /( TL×Zr )<0.050  (2),

where ΔG 2 m is a positional difference along the optical axis between a position of the second lens group at the wide-angle end and a position of the second lens group at the telephoto end, TL is a distance along the optical axis from a most object-side surface of the first lens group to the image plane, and Zr is a zoom ratio.

4. The zoom lens as claimed in claim 1 , wherein the condition expression (3) below is satisfied:
TL/Y< 40  (3),

where TL is a distance along the optical axis from a most object-side surface of the first lens group to the image plane, and Y is a maximum image height.

5. The zoom lens as claimed in claim 1 , where the condition expression (4) below is satisfied:
1.75< Nd 31  (4),

where Nd 31 is a refractive index with respect to the d-line of a most object-side lens of the third lens group.

6. The zoom lens as claimed in claim 1 , wherein the condition expression (5) below is satisfied:
−10< f 4/ fw<− 1  (5),

where f 4 is a focal length of the fourth lens group, and fw is a focal length of the entire system at the wide-angle end.

7. The zoom lens as claimed in claim 1 , wherein a position of the second lens group at the telephoto end is on the image side of a position of the second lens group at the wide-angle end.

8. The zoom lens as claimed in claim 1 , wherein a position of the third lens group at the telephoto end is on the image side of a position of the third lens group at the wide-angle end.

9. The zoom lens as claimed in claim 1 , wherein a position of the fourth lens group at the telephoto end is on the image side of a position of the fourth lens group at the wide-angle end.

10. The zoom lens as claimed in claim 1 , wherein the first lens group consists essentially of, in order from the object side, a first lens-group front group having a negative refractive power, a first lens-group middle group having a positive refractive power, and a first lens-group rear group having a positive refractive power, and only the first lens-group middle group is moved along the optical axis direction during focusing.

11. An imaging apparatus comprising the zoom lens as claimed in claim 1 .

12. A zoom lens consisting essentially of five lens groups consisting of, in order from the object side:
a first lens group having a positive refractive power;
a second lens group having a positive refractive power;
a third lens group having a negative refractive power;
a fourth lens group; and
a fifth lens group having a positive refractive power,
wherein, during magnification change from a wide-angle end to a telephoto end, the first lens group and the fifth lens group are fixed relative to an image plane, the second lens group, the third lens group, and the fourth lens group are moved along an optical axis direction to change distances between the lens groups, and the condition expression (1) below is satisfied:
5< f 2/ fw   (1),

where f 2 is a focal length of the second lens group, and fw is a focal length of the entire system at the wide-angle end.

13. The zoom lens as claimed in claim 12 , wherein the condition expression (2) below is satisfied:
0.005<Δ G 2 m /( TL×Zr )<0.050  (2),

where ΔG 2 m is a positional difference along the optical axis between a position of the second lens group at the wide-angle end and a position of the second lens group at the telephoto end, TL is a distance along the optical axis from a most object-side surface of the first lens group to the image plane, and Zr is a zoom ratio.

14. The zoom lens as claimed in claim 12 , wherein the condition expression (3) below is satisfied:
TL/Y< 40  (3),

where TL is a distance along the optical axis from a most object-side surface of the first lens group to the image plane, and Y is a maximum image height.

15. The zoom lens as claimed in claim 12 , where the condition expression (4) below is satisfied:
1.75< Nd 31  (4),

where Nd 31 is a refractive index with respect to the d-line of a most object-side lens of the third lens group.

16. The zoom lens as claimed in claim 12 , wherein the condition expression (5) below is satisfied:
−10< f 4/ fw<− 1  (5),

where f 4 is a focal length of the fourth lens group, and fw is a focal length of the entire system at the wide-angle end.

17. The zoom lens as claimed in claim 12 , wherein a position of the second lens group at the telephoto end is on the image side of a position of the second lens group at the wide-angle end.

18. The zoom lens as claimed in claim 12 , wherein a position of the third lens group at the telephoto end is on the image side of a position of the third lens group at the wide-angle end.

19. The zoom lens as claimed in claim 12 , wherein the fourth lens group has a negative refractive power, and a position of the fourth lens group at the telephoto end is on the image side of a position of the fourth lens group at the wide-angle end.

20. An imaging apparatus comprising the zoom lens as claimed in claim 12 .

Assignees

• Fujifilm Corp

Inventors

• Nagatoshi Yukiko

Classifications

• G02B15/167 Primary

  having an additional fixed front lens or group of lenses · CPC title

• G02B15/163 Primary

  having a first movable lens or lens group and a second movable lens or lens group, both in front of a fixed lens or lens group (G02B15/177 takes precedence) · CPC title

• G02B15/177

  having a negative front lens or group of lenses · CPC title

• G02B15/16

  with interdependent non-linearly related movements between one lens or lens group, and another lens or lens group (G02B15/22 takes precedence) · CPC title

• G02B15/145119

  arranged ++--+ · CPC title