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

Patent metadata

Field	Value
Publication number	US-10877240-B2
Application number	US-201615777910-A
Country	US
Kind code	B2
Filing date	Nov 28, 2016
Priority date	Nov 30, 2015
Publication date	Dec 29, 2020
Grant date	Dec 29, 2020

Abstract

A zoom optical system comprises, in order from an object: a first lens group (G 1 ) having positive refractive power; a second lens group (G 2 ) having negative refractive power; and a subsequent group (GR) including at least one lens group. Upon zooming, distances between the first lens group (G 1 ) and the second lens group (G 2 ) and between the second lens group (G 2 ) and the subsequent group (GR) change. The subsequent group (GR) comprises a focusing group (Gfc) having negative refractive power for focusing. The first lens group (G 1 ) comprises a 1-1st lens that has positive refractive power and is disposed closest to the object. A following conditional expression is satisfied:

0.20< f 1/ fR <0.85
where, f1 denotes a focal length of the first lens group, and fR denotes a focal length of a lens component, in the subsequent group, closest to an image surface.

First claim

The invention claimed is:

1. A zoom optical system comprising, in order from an object: a first lens group having positive refractive power; a second lens group having negative refractive power; and a subsequent group including at least one lens group, wherein
upon zooming, the second lens group is moved along an optical axis, and distances between the first lens group and the second lens group and between the second lens group and the subsequent group change,
the subsequent group comprises a focusing group having negative refractive power for focusing,
the first lens group comprises a 1-1st lens that has positive refractive power and is disposed closest to the object, and
following conditional expressions are satisfied:
0.20<f1/fR<0.85
4.30<f1/(−f2)<5.00
where,
f1 denotes a focal length of the first lens group,
fR denotes a focal length of a lens component, in the subsequent group, closest to an image surface, and
f2 denotes a focal length of the second lens group.

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

3. The zoom optical system according to claim 1 , wherein the focusing group comprises at least one lens having positive refractive power and at least one lens having negative refractive power.

4. The zoom optical system according to claim 3 , wherein
a following conditional expression is satisfied:
1.00<nFP/nFN <1.20
where,
nFP denotes a refractive index of a lens with largest positive refractive power in the focusing group, and
nFN denotes a refractive index of a lens with largest negative refractive power in the focusing group.

5. The zoom optical system according to claim 3 , wherein
a following conditional expression is satisfied:
0.52<νFP/νFN <0.82
where,
νFP denotes an Abbe number of the lens with the largest positive refractive power in the focusing group, and
νFN denotes an Abbe number of the lens with the largest negative refractive power in the focusing group.

6. The zoom optical system according to claim 1 , wherein the first lens group includes, in order from the object: the 1-1st lens; a 1-2nd lens having negative refractive power; and a 1-3rd lens having positive refractive power.

7. The zoom optical system according to claim 1 , wherein the second lens group includes, in order from the object: a 2-1st lens having negative refractive power; a 2-2nd lens having positive refractive power; and a 2-3rd lens having negative refractive power.

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

9. A zoom optical system comprising, in order from an object: a first lens group having positive refractive power; a second lens group having negative refractive power; and a subsequent group including at least one lens group, wherein
upon zooming, the second lens group is moved along an optical axis, and distances between the first lens group and the second lens group and between the second lens group and the subsequent group change,
the first lens group includes, in order from the object: a 1-1st lens having positive refractive power; a 1-2nd lens having negative refractive power; and a 1-3rd lens having positive refractive power,
the subsequent group comprises a focusing group having negative refractive power for focusing, and
a following conditional expression is satisfied:
0.20<f1/fR<0.75
where,
f1 denotes a focal length of the first lens group, and
fR denotes a focal length of a lens component, in the subsequent group, closest to an image surface.

10. The zoom optical system according to claim 9 , wherein the first lens group moves toward the object upon zooming from a wide angle end state to a telephoto end state.

11. The zoom optical system according to claim 9 , wherein the focusing group comprises at least one lens having positive refractive power and at least one lens having negative refractive power.

12. The zoom optical system according to claim 9 , wherein the second lens group includes, in order from the object: a 2-1st lens having negative refractive power; a 2-2nd lens having positive refractive power; and a 2-3rd lens having negative refractive power.

13. The zoom optical system according to claim 9 , wherein a lens group disposed closest to an image side moves upon zooming.

14. The zoom optical system according to claim 9 , wherein a lens disposed closest to an image side has positive refractive power.

15. A method for manufacturing a zoom optical system which comprises, in order from an object: a first lens group having positive refractive power;
a second lens group having negative refractive power; and a subsequent group including at least one lens group,
the method comprising a step of arranging the lens groups in a lens barrel so that:
upon zooming, the second lens group is moved along an optical axis, and distances between the first lens group and the second lens group and between the second lens group and the subsequent group change,
the subsequent group comprises a focusing group having negative refractive power for focusing, and
further comprising one of the following features (A) (B), or (C):
(A) the first lens group comprises a 1-1st lens that has positive refractive power and is disposed closest to the object, and
following conditional expressions are satisfied:
0.20<f1/fR<0.85
4.30<f1/(−f2)<5.00
where,
f1 denotes a focal length of the first lens group,
fR denotes a focal length of a lens component, in the subsequent group, closest to an image surface, and
f2 denotes a focal length of the second lens group;
(B) the first lens group includes, in order from the object: a 1-1st lens having positive refractive power; a 1-2nd lens having negative refractive power; and a 1-3rd lens having positive refractive power, and
a following conditional expression is satisfied:
0.20<f1/fR<0.75
where,
f1 denotes a focal length of the first lens group, and
fR denotes a focal length of a lens component, in the subsequent group, closest to an image surface; and
(C) a lens placed closest to an object in the subsequent lens group has positive refractive power, and
a following conditional expression is satisfied:
0.30<f1/fR ≤0.44
where,
f1 denotes a focal length of the first lens group, and
fR denotes a focal length of a lens component, in the subsequent group, closest to an image surface.

16. A zoom optical system comprising, in order from an object: a first lens group having positive refractive power; a second lens group having negative refractive power; and a subsequent group including at least one lens group, wherein
upon zooming, the second lens group is moved along an optical axis, and distances between the first lens group and the second lens group and between the second lens group and the subsequent group change,
a lens placed closest to an object in the subsequent lens group has positive refractive power,
the subsequent group comprises a focusing group having negative refractive power for focusing, and
a following conditional expression is satisfied:
0.30<f1/fR ≤0.44
where,
f1 denotes a focal length of the first lens group, and
fR denotes a focal length of a lens component, in the subsequent group, closest to an image surface.

Assignees

• Nikon Corp

Inventors

• Machida Kosuke

Classifications

• G02B15/145121 Primary

  arranged +-+-+ · CPC title

• G02B9/12

  having three components only · CPC title

• G02B13/0045

  having five or more lenses · CPC title

• G02B9/60

  having five components only · CPC title

• G02B15/20

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