Variable magnification optical system, optical device, and method for manufacturing variable magnification optical system

Patent metadata

Field	Value
Publication number	US-11079575-B2
Application number	US-201716338736-A
Country	US
Kind code	B2
Filing date	Oct 16, 2017
Priority date	Oct 18, 2016
Publication date	Aug 3, 2021
Grant date	Aug 3, 2021

Abstract

Comprising, in order from an object side: a first lens group having positive refractive power, a second lens group having negative refractive power, a third lens group having positive refractive power, a fourth lens group having positive refractive power, and a fifth lens group having negative refractive power; upon varying a magnification, the first lens group being fixed with respect to the image plane, and each distance between the neighboring lens groups being varied; upon focusing, at least a portion of the fourth lens group being moved; and predetermined conditional expression(s) being satisfied, thereby variations in various aberrations upon varying magnification being superbly suppressed.

First claim

What is claimed is:

1. A variable magnification optical system comprising, in order from an object side: a first lens group having positive refractive power, a second lens group having negative refractive power, a third lens group having positive refractive power, a fourth lens group having positive refractive power, and a fifth lens group having negative refractive power;
upon varying a magnification, the first lens group being fixed with respect to the image plane, and distances between the neighboring respective lens groups being varied;
upon focusing, at least a portion of the fourth lens group being moved; and
the following conditional expressions being satisfied:
1.20< f 5/ f 2<2.80
0.80< f 3/ f 4<2.20

where f5 denotes a focal length of the fifth lens group, f2 denotes a focal length of the second lens group, f3 denotes a focal length of the third lens group, and f4 denotes a focal length of the fourth lens group.

2. A variable magnification optical system according to claim 1 , wherein, upon varying magnification, the third lens group is fixed with respect to the image plane.

3. A variable magnification optical system according to claim 1 , wherein, upon varying magnification, the fifth lens group is fixed with respect to the image plane.

4. A variable magnification optical system according to claim 1 , wherein an aperture stop is disposed between the second lens group and the fourth lens group.

5. A variable magnification optical system according to claim 1 , wherein at least a portion of the fifth lens group is movable to have a component in a direction perpendicular to the optical axis.

6. A variable magnification optical system according to claim 1 , wherein the following conditional expression is satisfied:
0.64< f 4/(− f 2)<2.20

where f4 denotes a focal length of the fourth lens group, and f2 denotes a focal length of the second lens group.

7. A variable magnification optical system according to claim 1 , wherein the following conditional expression is satisfied:
0.94<(− f 5)/ f 4<3.00

where f5 denotes a focal length of the fifth lens group, and f4 denotes a focal length of the fourth lens group.

8. A variable magnification optical system according to claim 1 , wherein the following conditional expression is satisfied:
1.00< f 1/(− f 2)<4.50

where f1 denotes a focal length of the first lens group, and f2 denotes a focal length of the second lens group.

9. A variable magnification optical system according to claim 1 , wherein the following conditional expression is satisfied:
1.00< f 3/(− f 2)<4.20

where f3 denotes a focal length of the third lens group, and f2 denotes a focal length of the second lens group.

10. A variable magnification optical system according to claim 1 , wherein the following conditional expression is satisfied:
0.60< f 1/(− f 5)<2.70

where f1 denotes a focal length of the first lens group, and f5 denotes a focal length of the fifth lens group.

11. An optical system comprising a variable magnification optical system according to claim 1 .

12. A variable magnification optical system comprising, in order from an object side: a first lens group having positive refractive power, a second lens group having negative refractive power, a third lens group having positive refractive power, a fourth lens group having positive refractive power, and a fifth lens group having negative refractive power;
upon varying a magnification, distances between the neighboring respective lens groups being varied;
an aperture stop being disposed between the second lens group and the fourth lens group; and
the following conditional expressions being satisfied:
1.55≤(− f 5)/ f 4<3.00

1.00 <f 3/(− f 2)<4.20

where f5 denotes a focal length of the fifth lens group, f4 denotes a focal length of the fourth lens group, f3 denotes a focal length of the third lens group, and f2 denotes a focal length of the second lens group.

13. A variable magnification optical system according to claim 12 , wherein the following conditional expression is satisfied:
1.20< f 5/ f 2<3.60
where f5 denotes a focal length of the fifth lens group, and f2 denotes a focal length of the second lens group.

14. A variable magnification optical system according to claim 12 , wherein the following conditional expression is satisfied:
0.80< f 3/ f 4<2.20
where f3 denotes a focal length of the third lens group, and f4 denotes a focal length of the fourth lens group.

15. A variable magnification optical system according to claim 12 , wherein the following conditional expression is satisfied:
0.64< f 4/(− f 2)<2.20

where f4 denotes a focal length of the fourth lens group, and f2 denotes a focal length of the second lens group.

16. A variable magnification optical system according to claim 12 , wherein the following conditional expression is satisfied:
1.00< f 1/(− f 2)<4.50

where f1 denotes a focal length of the first lens group, and f2 denotes a focal length of the second lens group.

17. A variable magnification optical system according to claim 12 , wherein the following conditional expression is satisfied:
0.60< f 1/(− f 5)<2.70

where f1 denotes a focal length of the first lens group, and f5 denotes a focal length of the fifth lens group.

18. An optical system comprising a variable magnification optical system according to claim 12 .

19. A method for manufacturing a variable magnification optical system comprising, in order from an object side: a first lens group having positive refractive power, a second lens group having negative refractive power, a third lens group having positive refractive power, a fourth lens group having positive refractive power and a fifth lens group having negative refractive power; the method comprising one of steps (A) and (B):
step (A) including:
constituting to satisfy the following conditional expressions:
1.20< f 5/ f 2<2.80
0.80< f 3/ f 4<2.20

where f5 denotes a focal length of the fifth lens group, f2 denotes a focal length of the second lens group, f3 denotes a focal length of the third lens group, and f4 denotes a focal length of the fourth lens group;
constituting such that, upon varying magnification, the first lens group is fixed with respect to the image plane, and each distance between the neighboring lens groups is varied; and
constituting such that, upon focusing, at least a portion of the fourth lens group is moved along the optical axis; and
step (B) including:
constituting to satisfy the following conditional expressions:
1.55≤(− f 5)/ f 4<3.00

1.00< f 3/(− f 2)<4.20

where f5 denotes a focal length of the fifth lens group, f4 denotes a focal length of the fourth lens group, f3 denotes a focal length of the third lens group, and f2 denotes a focal length of the second lens group;
constituting such that, upon varying a magnification, each distance between the neighboring lens groups is varied; and
constituting such that an aperture stop is disposed between the second lens group and the fourth lens group.

Assignees

• Nikon Corp

Inventors

• Ito Tomoki

Classifications

• G02B15/145113 Primary

  arranged +-++- · CPC title

• G02B15/20

  having an additional movable lens or lens group for varying the objective focal length · CPC title

• G02B13/009

  having zoom function · CPC title