Zoom optical system, optical apparatus, imaging apparatus and method for manufacturing the zoom optical system

Patent metadata

Field	Value
Publication number	US-11175485-B2
Application number	US-201616345185-A
Country	US
Kind code	B2
Filing date	Nov 21, 2016
Priority date	Nov 21, 2016
Publication date	Nov 16, 2021
Grant date	Nov 16, 2021

Abstract

A zoom optical system comprises, in order from an object: a front lens group (GFS) having a positive refractive power; an M1 lens group (GM1) having a negative refractive power; an M2 lens group (GM2) having a positive refractive power; an RN lens group (GRN) having a negative refractive power; and a subsequent lens group (GRS). Upon zooming, the distance between the front lens group (GFS) and the M1 lens group (GM1) changes, the distance between the M1 lens group (GM1) and the M2 lens group (GM2) changes, and the distance between the M2 lens group (GM2) and the RN lens group (GRN) changes. Upon focusing from an infinite distant object to a short distant object, the RN lens group (GRN) moves.

First claim

The invention claimed is:

1. A zoom optical system comprising, in order from an object: a front lens group having a positive refractive power; an M 1 lens group having a negative refractive power; an M 2 lens group having a positive refractive power; an RN lens group having a negative refractive power; and a subsequent lens group, wherein
upon zooming, a distance between the front lens group and the M 1 lens group changes, a distance between the M 1 lens group and the M 2 lens group changes, and a distance between the M 2 lens group and the RN lens group changes,
upon zooming, a lens group disposed closest to an image is moved,
upon focusing from an infinite distant object to a short distant object, the RN lens group moves, and
following conditional expressions are satisfied,
0.15<(− fTM 1)/f1<0.35

0.264≤ fTM 2/ f 1<0.40

where
f1: a focal length of the front lens group,
fTM1: a focal length of the M 1 lens group in a telephoto end state, and
fTM2: a focal length of the M 2 lens group in a telephoto end state,
wherein the RN lens group comprises:
at least one lens having positive refractive power; and
at least one lens having negative refractive power.

2. The zoom optical system according to claim 1 , wherein
the subsequent lens group comprises, in order from the object: a lens having a negative refractive power; and a lens having a positive refractive power.

3. The zoom optical system according to claim 2 , wherein
a following conditional expression is satisfied,
0.70<(− fN )/ fP< 2.00

where
fN: a focal length of a lens having a strongest negative refractive power in the subsequent lens group, and
fP: a focal length of a lens having a strongest positive refractive power in the subsequent lens group.

4. The zoom optical system according to claim 1 , wherein
upon zooming from a wide-angle end state to a telephoto end state, the front lens group moves toward the object.

5. The zoom optical system according to claim 1 , wherein
the subsequent lens group comprises a negative meniscus lens that has a concave surface facing the object, and is adjacent to an image side of the RN lens group.

6. The zoom optical system according to claim 1 , wherein
a following conditional expression is satisfied,
1.80 <f 1 /fw< 3.50

where
f1: a focal length of the front lens group, and
fw: a focal length of the zoom optical system in a wide-angle end state.

7. The zoom optical system according to claim 1 , wherein
a following conditional expression is satisfied,
3.70 <f 1/(− fTM 1)<5.00

where
f1: a focal length of the front lens group, and
fTM1: a focal length of the M 1 lens group in a telephoto end state.

8. The zoom optical system according to claim 1 , wherein
a following conditional expression is satisfied,
3.20 <f 1 /fTM 2<5.00

where
f1: a focal length of the front lens group, and
fTM2: a focal length of the M 2 lens group in a telephoto end state.

9. The zoom optical system according to claim 1 , wherein
upon zooming, a lens group nearest to the object in the M 1 lens group is fixed with respect to an image surface.

10. The zoom optical system according to claim 1 , wherein
the M 2 lens group comprises a vibration-proof lens group movable in a direction orthogonal to an optical axis.

11. The zoom optical system according to claim 10 , wherein
the vibration-proof lens group consists of, in order from the object: a lens having a negative refractive power;
and a lens having a positive refractive power.

12. The zoom optical system according to claim 11 , wherein
a following conditional expression is satisfied,
1.00 <nvrN/nvrP< 1.25

where
nvrN: a refractive index of the lens having the negative refractive power in the vibration-proof lens group, and
nvrP: a refractive index of the lens having the positive refractive power in the vibration-proof lens group.

13. The zoom optical system according to claim 11 , wherein
a following conditional expression is satisfied,
0.30 <νvrN/νvrP< 0.90

where
νvrN: an Abbe number of the lens having the negative refractive power in the vibration-proof lens group, and
νvrP: an Abbe number of the lens having the positive refractive power in the vibration-proof lens group.

14. The zoom optical system according to claim 1 , wherein
the M 1 lens group comprises a vibration-proof lens group movable in a direction orthogonal to an optical axis.

15. The zoom optical system according to claim 14 , wherein
the vibration-proof lens group consists of, in order from the object: a lens having a negative refractive power; and a lens having a positive refractive power.

16. The zoom optical system according to claim 15 , wherein
a following conditional expression is satisfied,
0.80 <nvrN/nvrP< 1.00

where
nvrN: a refractive index of the lens having the negative refractive power in the vibration-proof lens group, and
nvrP: a refractive index of the lens having the positive refractive power in the vibration-proof lens group.

17. The zoom optical system according to claim 15 , wherein
a following conditional expression is satisfied,
1.20 <νvrN/νvrP< 2.40

where
νvrN: an Abbe number of the lens having the negative refractive power in the vibration-proof lens group, and
νvrP: an Abbe number of the lens having the positive refractive power in the vibration-proof lens group.

18. An optical apparatus comprising the zoom optical system according to claim 1 .

19. An imaging apparatus comprising: the zoom optical system according to claim 1 ; and an imaging unit that takes an image formed by the zoom optical system.

20. A zoom optical system comprising, in order from an object: a front lens group having a positive refractive power; an M 1 lens group having a negative refractive power; an M 2 lens group having a positive refractive power; an RN lens group having a negative refractive power; and a subsequent lens group, wherein
upon zooming, a distance between the front lens group and the M 1 lens group changes, a distance between the M 1 lens group and the M 2 lens group changes, and a distance between the M 2 lens group and the RN lens group changes,
upon zooming, a lens group disposed closest to an image is moved,
upon focusing from an infinite distant object to a short distant object, the RN lens group moves,
the subsequent lens group comprises a lens having a positive refractive power, and
following conditional expressions are satisfied,
0.20 <fTM 2 /f 1<0.40
1.80 <f 1 /fw≤ 2.441

where
fTM2: a focal length of the M 2 lens group in a telephoto end state,
f1: a focal length of the front lens group, and
fw: a focal length of the zoom optical system in a wide-angle end state.

21. The zoom optical system according to claim 20 , wherein
a following conditional expression is satisfied,
0.15<(− fTM 1)/ f 1<0.35

where
fTM1: a focal length of the M 1 lens group in a telephoto end state.

22. The zoom optical system according to claim 20 , wherein
a following conditional expression is satisfied,
3.70 <f 1/(− fTM 1<5.00

where
fTM1: a focal length of the M 1 lens group in a telephoto end state.

23. The zoom optical system according to claim 20 , wherein
a following conditional expression is satisfied,
3.20 <f 1 /fTM 2<5.00.

24. An optical apparatus comprising the zoom optical system according to claim 20 .

25. An imaging a

Assignees

• Nikon Corp

Inventors

• Machida Kosuke

Classifications

• G02B15/173

  arranged +-+ · CPC title

• G02B15/145121 Primary

  arranged +-+-+ · CPC title

• G02B15/20

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

• G02B15/1451 Primary

  the first group being positive · CPC title

• G02B15/145125

  arranged +--++ · CPC title