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

Patent metadata

Field	Value
Publication number	US-11899189-B2
Application number	US-202117359927-A
Country	US
Kind code	B2
Filing date	Jun 28, 2021
Priority date	Oct 18, 2016
Publication date	Feb 13, 2024
Grant date	Feb 13, 2024

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, and a fifth lens group;
upon varying a magnification, distances between the neighboring respective lens groups being varied; and
the following conditional expressions being satisfied:
1.00 <f 3/(− f 2)≤2.10

1.00 <f 1/(− f 5)<2.50

where f3 denotes a focal length of the third lens group, f2 denotes a focal length of the second lens group, f1 denotes a focal length of the first lens group, and f5 denotes a focal length of the fifth lens group.

2. A variable magnification optical system according to claim 1 , wherein, upon focusing, at least a portion of the fourth lens group is moved.

3. A variable magnification optical system according to claim 1 , wherein the third lens group comprises a lens having positive refractive power at the most object side.

4. A variable magnification optical system according to claim 1 , wherein the first lens group comprises a lens having positive refractive power at the most image side.

5. A variable magnification optical system according to claim 1 , wherein the following conditional expression is satisfied:
1.20 <f 5 /f 2<3.60.

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.

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

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

9. 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, and a fifth lens group;
upon varying a magnification, distances between the neighboring respective lens groups being varied; and
the following conditional expressions being satisfied:
2.60 <f 1/(− f 2)<4.50

1.00 <f 3/(− f 2)≤2.10

where f1 denotes a focal length of the first lens group, f2 denotes a focal length of the second lens group, and f3 denotes a focal length of the third lens group.

10. A variable magnification optical system according to claim 9 , wherein, upon focusing, at least a portion of the fourth lens group is moved.

11. A variable magnification optical system according to claim 9 , wherein the first lens group comprises a cemented lens constructed by, in order from the object side, a lens having negative refractive power and a lens having positive refractive power.

12. A variable magnification optical system according to claim 9 , wherein the third lens group comprises a lens having positive refractive power at the most object side.

13. A variable magnification optical system according to claim 9 , 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.

14. A variable magnification optical system according to claim 9 , 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.

15. An optical system comprising a variable magnification optical system according to claim 9 .

16. 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; and
the following conditional expressions being satisfied:
0.64 <f 4/(− f 2)<2.20

1.00 <f 3/(− f 2)<3.00

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

17. A variable magnification optical system according to claim 16 , 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.

18. A variable magnification optical system according to claim 16 , wherein the following conditional expression is satisfied:
0.80 <f 3 /f 4<2.20.

19. A variable magnification optical system according to claim 16 , 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.

20. A variable magnification optical system according to claim 16 , 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.

21. A variable magnification optical system according to claim 16 , 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.

22. An optical system comprising a variable magnification optical system according to claim 16 .

23. A method for manufacturing one of the variable magnification optical systems A and B:
the optical system A 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, and a fifth lens group;
the optical system B 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 for manufacturing the optical system A comprising steps of:
constructing such that, upon varying a magnification, distances between the neighboring respective lens groups are varied; and
constructing such that one of the following features X and Y is satisfied:
the feature X comprising:
constructing such that the following conditional expressions are satisfied:
1.00 <f 3/(− f 2)≤2.10

1.00 <f 1/(− f 5)<2.50

where f3 denotes a focal length of the third lens group, f2 denotes a focal length of the second lens group, f1 denotes a focal length of the first lens group, and f5 denotes a focal length of the fifth lens group; and
the feature Y comprising:
constructing such that the following conditional expressions are satisfied:
2.60 <f 1/(− f 2)<4.50

1.00 <f 3/(− f 2)≤2.10

where f1 denotes a focal length of the first lens group, f2 denotes a focal length of the second lens group, and f3 denotes a focal length of the third lens group; and
the method for manufacturing the optical system B comprising steps of:
constructing such that, upon varying a magnification, distances between the neighboring respective lens groups are varied; and
constructing such that the following conditional expressions are satisfied:
0.64 <f 4/(− f 2)<2.20

1.

Assignees

• Nikon Corp

Inventors

• Ito Tomoki

Classifications

• G02B15/145113 Primary

  arranged +-++- · CPC title

• G02B13/009

  having zoom function · CPC title

• G02B15/20

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