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

Patent metadata

Field	Value
Publication number	US-2016109692-A1
Application number	US-201514979409-A
Country	US
Kind code	A1
Filing date	Dec 27, 2015
Priority date	Jun 28, 2013
Publication date	Apr 21, 2016
Grant date	—

Abstract

A variable power optical system (ZL) used for an optical apparatus, such as a camera ( 1 ), includes, 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; a third lens group (G 3 ) having positive refractive power; and a fourth lens group (G 4 ) having positive refractive power. The distance between the respective lens groups changes upon zooming from the wide-angle end state to the telephoto end state. The third lens group (G 3 ) includes: an intermediate group (G 3 b ) constituted by a positive lens, a negative lens, a negative lens, and a positive lens; and an image side group (G 3 c ) having negative refractive power and disposed to an image side of the intermediate group (G 3 b ). Upon focusing, the position of the intermediate group (G 3 b ) with respect to the image plane is fixed and the image side group (G 3 c ) moves along the optical axis.

First claim

1 . A variable power optical system comprising, in order from an object:
a first lens group having positive refractive power; a second lens group having negative refractive power; a third lens group having positive refractive power; and a fourth lens group having positive refractive power, the distance between the first lens group and the second lens group, the distance between the second lens group and the third lens group, and the distance between the third lens group and the fourth lens group changing respectively upon zooming from a wide-angle end state to a telephoto end state, the third lens group including: an intermediate group constituted by, in order from the object, a positive lens, a negative lens, a negative lens and a positive lens; and an image side group having negative refractive power and disposed to an image side of the intermediate group, and the position of the intermediate group with respect to the image plane being fixed and the image side group moving along an optical axis upon focusing.

2 . The variable power optical system according to claim 1 , wherein the following conditional expression is satisfied:
0.4<(− f 2)/( fw×ft ) 1/2 <1.1

where f2 denotes a focal length of the second lens group, fw denotes a focal length of the variable power optical system in the wide-angle end state, and ft denotes a focal length of the variable power optical system in the telephoto end state.

3 . The variable power optical system according to claim 1 , wherein the third lens group includes an object side group having positive refractive power and disposed to the object side of the intermediate group.

4 . The variable power optical system according to claim 1 , wherein the image side group is constituted by one negative lens.

5 . The variable power optical system according to claim 1 , wherein the image side group is constituted by one negative meniscus lens having a concave surface facing the image plane.

6 . The variable power optical system according to claim 1 , wherein the image side group includes at least one negative lens, and satisfies the following conditional expressions:
ndF+ 0.0052×ν dF− 1.965<0
ν dF> 60

where ndF denotes a refractive index of a medium of the negative lens included in the image side group at d-line, and νdF denotes an Abbe number of the medium of the negative lens included in the image side group.

7 . The variable power optical system according to claim 1 , wherein
the third lens group includes an object side group having positive refractive power and disposed to the object side of the intermediate group, the object side group includes one positive lens, and the following conditional expression is satisfied:
ν dO> 60

where νdO denotes an Abbe number of a medium of the positive lens included in the object side group.

8 . The variable power optical system according to claim 1 , wherein the following conditional expression is satisfied:
4.0< f 4/ fw< 11.0
where f4 denotes a focal length of the fourth lens group, and fw denotes a focal length of the variable power optical system in the wide-angle end state.

9 . The variable power optical system according to claim 1 , wherein the first lens group moves toward the image plane first and then moves toward the object upon zooming from the wide-angle end state to the telephoto end state.

10 . The variable power optical system according to claim 1 , wherein the third lens group includes a vibration-isolating lens group which is disposed to the image side of the intermediate group, has positive refractive power, and moves so as to have a component in a direction orthogonal to the optical axis.

11 . The variable power optical system according to claim 1 , wherein
the third lens group includes, in order from the object: a first sub-group of which position with respect to the image plane is fixed upon correcting camera shake; and a second sub-group used as a vibration-isolating lens group which has positive refractive power and can move so as to have a component in a direction orthogonal to the optical axis upon correcting camera shake, and the following conditional expression is satisfied:
1.5< fv×FNOw/f 3<5.0

where f3 denotes a focal length of the third lens group, fv denotes a focal length of the second sub-group, and FNOw denotes an F number in the wide-angle end state.

12 . A variable power optical system comprising, in order from an object:
a first lens group having positive refractive power; a second lens group having negative refractive power; a third lens group having positive refractive power; and a fourth lens group having positive refractive power, the distance between the first lens group and the second lens group, the distance between the second lens group and the third lens group, and the distance between the third lens group and the fourth lens group changing respectively upon zooming from a wide-angle end state to a telephoto end state, the third lens group including: an intermediate group constituted by, in order from the object, a first positive lens, a first negative lens, a second negative lens and a second positive lens; and an image side group having negative refractive power and disposed to an image side of the intermediate group, the position of the intermediate group with respect to the image plane being fixed and the image side group moving along an optical axis upon focusing, and the following conditional expression being satisfied:
−0.8<( R 2 a+R 1 b )/( R 2 a−R 1 b )<0.5

where R2a denotes a radius of curvature of an image side lens surface of the first negative lens, and Rib denotes a radius of curvature of an object side lens surface of the second negative lens.

13 . The variable power optical system according to claim 12 , wherein the following conditional expression is satisfied:
0.4<(− f 2)/( fw×ft ) 1/2 <1.1

where f2 denotes a focal length of the second lens group, fw denotes a focal length of the variable power optical system in the wide-angle end state, and ft denotes a focal length of the variable power optical system in the telephoto end state.

14 . The variable power optical system according to claim 12 , wherein the third lens group includes an object side group having positive refractive power and disposed to the object side of the intermediate group.

15 . The variable power optical system according to claim 12 , wherein the image side group is constituted by one negative lens.

16 . The variable power optical system according to claim 12 , wherein the image side group is constituted by one negative meniscus lens having a concave surface facing the image plane.

17 . The variable power optical system according to claim 12 , wherein the image side group includes at least one negative lens, and satisfies the following conditional expressions:
ndF+ 0.0052×ν dF− 1.965<0
ν dF> 60

where ndF denotes a refractive index of a medium of the negative lens included in the image side group at d-line, and νdF denotes an Abbe number of the medium of the negative lens included in the image side group.

18 . The variable power optical system according to claim 12 , wherein the third lens group includes an object side group having positive refractive power and disposed to the object side of the intermediate group,
the object side group includes one positive lens, and the following conditional expression is satisfied:
ν dO> 60

where νdO denotes an Abbe number of a medium of the positive lens inc

Assignees

• Nikon Corp

Inventors

• Shibata Satoru

Classifications

• G02B27/646

  compensating for small deviations, e.g. due to vibration or shake (movement of one or more optical elements for control of motion blur in cameras, projectors or printers G03B2205/0007; image stabilisation in cameras peculiar to the presence or use of an electronic image sensor H04N23/68) · CPC title

• G02B13/18 Primary

  with lenses having one or more non-spherical faces, e.g. for reducing geometrical aberration {(G02B13/002 takes precedence)} · CPC title

• G02B15/20

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

• G02B15/173 Primary

  arranged +-+ · CPC title

• G02B15/144113 Primary

  arranged +-++ · CPC title