Variable magnification optical system, optical equipment, and method for producing variable magnification optical system

Patent metadata

Field	Value
Publication number	US-11409086-B2
Application number	US-201817279737-A
Country	US
Kind code	B2
Filing date	Nov 20, 2018
Priority date	Nov 20, 2018
Publication date	Aug 9, 2022
Grant date	Aug 9, 2022

Abstract

A variable magnification optical system comprising a plurality of lens groups which includes a first negative lens group having negative refractive power, a second negative lens group disposed at a more image side than the first negative lens group and having negative refractive power, a third negative lens group disposed at a more image side than the second negative lens group and having negative refractive power; upon varying a magnification, distances between adjacent lens groups being varied; the first negative lens group being movable to include a component in a direction perpendicular to the optical axis as a vibration reduction lens group; the second negative lens group being moved along the optical axis upon carrying out focusing; and the predetermined conditional expression (s) being satisfied. The variable magnification optical system can attain a high optical performance and be made in small in size.

First claim

What is claimed is:

1. A variable magnification optical system comprising a plurality of lens groups which include a first negative lens group having negative refractive power, a second negative lens group disposed at a more image side than the first negative lens group and having negative refractive power, and a third negative lens group disposed at a more image side than the second negative lens group and having negative refractive power;
upon varying a magnification, distances between adjacent lens groups being varied;
the second negative lens group being moved along the optical axis upon carrying out focusing, and
the following conditional expressions being satisfied:
0.500<(− f 3 n )/√( fw*ft )<2.500

0.150 <Bfaw/fw< 0.500

where f3n denotes a focal length of the third negative lens group, fw denotes a focal length of the variable magnification optical system as a whole in a wide angle end state, ft denotes a focal length of the variable magnification optical system as a whole in a telephoto end state, and Bfaw denotes an air converted back focus of the variable magnification optical system as a whole in the wide angle end state.

2. A variable magnification optical system according to claim 1 , wherein the following conditional expression is satisfied:
0.200<(− f 1 n )/√( fw*ft )<0.400

where f1n denotes a focal length of the first negative lens group, fw denotes the focal length of the variable magnification optical system as a whole in the wide angle end state, and ft denotes the focal length of the variable magnification optical system as a whole in the telephoto end state.

3. A variable magnification optical system according to claim 1 , wherein the following conditional expression is satisfied:
0.200<(− f 2 n )/√( fw*ft )<1.000

where f2n denotes a focal length of the second negative lens group, fw denotes the focal length of the variable magnification optical system as a whole in the wide angle end state, and ft denotes the focal length of the variable magnification optical system as a whole in the telephoto end state.

4. A variable magnification optical system according to claim 1 , wherein the following conditional expression is satisfied:
−1.000<β1 nt/β 2 2 nt <−0.300

where β1nt denotes a transverse magnification of the first negative lens group in the telephoto end state, and β2nt denotes a transverse magnification of the second negative lens group in the telephoto end state.

5. A variable magnification optical system according to claim 1 , wherein the following conditional expression is satisfied:
0.050< X 1 n /√( fw*ft )<0.250

where X1n denotes an amount of movement of the first negative lens group at the time of varying magnification from a wide angle end state to a telephoto end state, assuming that a direction of the movement toward the image side is positive, fw denotes the focal length of the variable magnification optical system as a whole in the wide angle end state, and ft denotes the focal length of the variable magnification optical system as a whole in the telephoto end state.

6. A variable magnification optical system according to claim 1 , wherein the first negative lens group includes, in order from the object side, a first negative lens, a second negative lens and a positive lens.

7. A variable magnification optical system according to claim 1 , wherein the second negative lens group includes, in order from the object side, a positive lens and a negative lens.

8. A variable magnification optical system according to claim 1 , wherein the third negative lens group is disposed at a most image side.

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

10. A variable magnification optical system according to claim 1 , comprising, in order from the object side, a first positive lens group having positive refractive power, the first negative lens group, a second positive lens group having positive refractive power, the second negative lens group and the third negative lens group.

11. A variable magnification optical system according to claim 1 , comprising, in order from the object side, a first positive lens group having positive refractive power, the first negative lens group, a second positive lens group having positive refractive power, the second negative lens group and the third negative lens group, and satisfying the following conditional expression:
0.500< f 2 p /(− f 1 n )<1.500

where f2p denotes a focal length of the second positive lens group, and fin denotes a focal length of the first negative lens group.

12. A variable magnification optical system according to claim 1 , comprising, in order from the object side, a first positive lens group having positive refractive power, the first negative lens group, a second positive lens group having positive refractive power, the second negative lens group and the third negative lens group, and satisfying the following conditional expression:
−0.300< X 2 p/√ ( fw*ft )<0.000

where X2p denotes an amount of movement of the second positive lens group upon varying the magnification from the wide angle end state to the telephoto end state, assuming that a direction of the movement toward the image side is positive, fw denotes the focal length of the variable magnification optical system as a whole in the wide angle end state, and ft denotes the focal length of the variable magnification optical system as a whole in the telephoto end state.

13. A variable magnification optical system according to claim 1 , comprising, in order from the object side, a first positive lens group having positive refractive power, the first negative lens group, a second positive lens group having positive refractive power, the second negative lens group and the third negative lens group, wherein, upon varying the magnification, the first positive lens group is moved.

14. A variable magnification optical system according to claim 1 , wherein the following conditional expression is satisfied:
20.000°<2ω w< 45.000°

where 2ωw denotes a total angle of view of the variable magnification optical system in a wide angle end state.

15. A variable magnification optical system according to claim 1 , wherein the following conditional expression is satisfied:
1.500<(β1 nt −1)*β Rt <4.500

where β1nt denotes a transverse magnification of the first negative lens group in the telephoto end state, and βRt denotes a composite transverse magnification of all lens groups disposed at a more image side than the first negative lens group in the telephoto end state.

16. A variable magnification optical system according to claim 1 , comprising, in order from the object side, a first positive lens group having positive refractive power, the first negative lens group, a second positive lens group having positive refractive power, the second negative lens group and the third negative lens group, wherein the following conditional expression is satisfied:
0.500< m 12 tw/fw <2.000

where m12tw denotes an amount of change of a distance between the first positive lens group and the first negative lens group upon varying the magnification from the wide angle end state to the telephoto end state, and fw denotes the focal length of the variable magnification optical system as a whole in the wide angle end state.

17. A variable magnification optical system according to claim 1 , comprising, in order from the object side, a first p

Assignees

• Nikon Corp

Inventors

• Ishikawa Takahiro
• Yokoi Norikazu

Classifications

• G02B15/145 Primary

  having five groups only · CPC title

• G02B27/646 Primary

  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

• G02B15/145105

  arranged +-+-- · CPC title