# US 2022/0035142 A1 · Variable magnification optical system, optical equipment, and method for producing variable magnification optical system

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- Number: US 2022/0035142 A1
- Document ID: US20220035142A1
- Status: Published application
- Kind: A1
- Application number: 17/279,737
- Filed: 2018-11-20
- Published: 2022-02-03
- Earliest claimed: 2018-11-20
- Assignees: Nikon Corporation
- Applicants: Nikon Corporation
- Inventors: Takahiro ISHIKAWA; Norikazu YOKOI
- Web page: https://patentgrep.com/patent/US20220035142A1

## CPC

- G02B 15/145: {having five groups only}
- G02B 27/646: {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)}
- G02B 15/145105: {arranged +-+--}
- G02B: OPTICAL ELEMENTS, SYSTEMS OR APPARATUS

## 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.

## Claims

### Claim 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<(−f3n)/√(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.

### Claim 2 (depends on 1)

A variable magnification optical system according to claim 1, wherein the following conditional expression is satisfied:
0.200<(−f1n)/√(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.

### Claim 3 (depends on 1)

A variable magnification optical system according to claim 1, wherein the following conditional expression is satisfied:
0.200<(−f2n)/√(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.

### Claim 4 (depends on 1)

A variable magnification optical system according to claim 1, wherein the following conditional expression is satisfied:
−1.000<β1nt/β2nt<−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.

### Claim 5 (depends on 1)

A variable magnification optical system according to claim 1, wherein the following conditional expression is satisfied:
0.050<X1n/√(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.

### Claim 6 (depends on 1)

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.

### Claim 7 (depends on 1)

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.

### Claim 8 (depends on 1)

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

### Claim 9 (depends on 1)

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.

### Claim 10 (depends on 1)

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.

### Claim 11 (depends on 1)

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<f2p/(−f1n)<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.

### Claim 12 (depends on 1)

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<X2p/√(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.

### Claim 13 (depends on 1)

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.

### Claim 14

(canceled)

### Claim 15 (depends on 1)

A variable magnification optical system according to claim 1, wherein the following conditional expression is satisfied:
20.000°<2ωw<45.000°
where 2ωw denotes a total angle of view of the variable magnification optical system in a wide angle end state.

### Claim 16 (depends on 1)

A variable magnification optical system according to claim 1, wherein the following conditional expression is satisfied:
1.500<(β1nt−1)*βRt<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.

### Claim 17 (depends on 1)

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<m12tw/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.

### Claim 18 (depends on 1)

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:
0.150<(−f1n)/f1p<0.350
where fin denotes a focal length of the first negative lens group, and f1p denotes a focal length of the first positive lens group.

### Claim 19 (depends on 1)

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 a third negative lens group, wherein the following conditional expression is satisfied:
0.010<(−f3n)/f1p<3.000
where f3n denotes a focal length of the third negative lens group, and f1p denotes a focal length of the first positive lens group.

### Claim 20 (depends on 1)

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:
0.050<f2n/f3n<1.500
where f2n denotes a focal length of the second negative lens group, and f3n denotes the focal length of the third negative lens group.

### Claim 21 (depends on 1)

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:
0.080<(RR−RF)/(RR+RF)<1.000
where RR denotes a radius of curvature of a most image side lens surface of the third negative lens group, and RF denotes a radius of curvature of a most object side lens surface of the third negative lens group.

### Claim 22 (depends on 1)

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:
−10.000<RF/Bfaw<−1.500
where RF denotes a radius of curvature of a most object side lens surface of the third negative lens group, and Bfaw denotes an air converted back focus of the variable magnification optical system as a whole in the wide angle end state.

### Claim 23 (depends on 1)

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

### Claim 24

(canceled)

### Claim 25

A variable magnification optical system comprising a plurality of lens groups which include, in order from an object side, a first positive lens group having positive refractive power, 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 first negative lens group being movable with a movement 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 following conditional expressions being satisfied:
0.010<(−f3n)/f1p<3.000
0.150<Bfaw/fw<0.500
where f3n denotes a focal length of the third negative lens group, f1p denotes a focal length of the first positive lens group, Bfaw denotes an air converted back focus of the variable magnification optical system as a whole in the wide angle end state, and fw denotes a focal length of the variable magnification optical system as a whole in a wide angle end state.

### Claim 26 (depends on 25)

A variable magnification optical system according to claim 25, wherein the following conditional expression is satisfied:
0.200<(−f1n)/√(fw*ft)<0.400
where fin denotes a focal length of the first negative lens group, and ft denotes the focal length of the variable magnification optical system as a whole in the telephoto end state.

### Claim 27 (depends on 25)

A variable magnification optical system according to claim 25, wherein the following conditional expression is satisfied:
0.200<(−f2n)/√(fw*ft)<1.000
where f2n denotes a focal length of the second negative lens group, and ft denotes the focal length of the variable magnification optical system as a whole in the telephoto end state.

### Claim 28 (depends on 25)

A variable magnification optical system according to claim 25, wherein the following conditional expression is satisfied:
20.000°<2ωw<45.000°
where 2ωw denotes a total angle of view of the variable magnification optical system in a wide angle end state.

### Claim 29 (depends on 25)

A variable magnification optical system according to claim 25, wherein the following conditional expression is satisfied:
1.500<(β1nt−1)*βRt<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.

### Claim 30 (depends on 25)

A variable magnification optical system according to claim 25, comprising, in order from the object side, the 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<m12tw/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.

### Claim 31 (depends on 25)

A variable magnification optical system according to claim 25, comprising, in order from the object side, the 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:
0.150<(−f1n)/f1p<0.350
where f1n denotes a focal length of the first negative lens group, and f1p denotes a focal length of the first positive lens group.

### Claim 32 (depends on 25)

A variable magnification optical system according to claim 25, comprising, in order from the object side, the 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:
0.050<f2n/f3n<1.500
where f2n denotes a focal length of the second negative lens group.

### Claim 33 (depends on 25)

An optical equipment comprising a variable magnification optical system according to claim 25.

### Claim 34

A method for manufacturing a variable magnification optical system which comprises a plurality of lens groups including 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; the method comprising the following steps of:
constructing such that, upon varying a magnification, distances between the adjacent lens groups are varied;
constructing such that one of the following features A or B is satisfied:
the feature A comprising:
constructing such that the second negative lens group is moved along the optical axis upon carrying out focusing, and
constructing such that the following conditional expressions are satisfied:
0.500<(−f3n)/√(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; and
the feature B comprising:
constructing such that a first positive lens group having positive refractive power is disposed at a more object side than the first negative lens group;
constructing such that the first negative lens group is movable with a movement component in a direction perpendicular to the optical axis as a vibration reduction lens group;
constructing such that the second negative lens group is moved upon carrying out focusing, and
constructing such that the following conditional expressions are satisfied:
0.010<(−f3n)/f1p<3.000
0.150<Bfaw/fw<0.500
where f3n denotes a focal length of the third negative lens group, f1p denotes a focal length of the first positive lens group, Bfaw denotes an air converted back focus of the variable magnification optical system as a whole in the wide angle end state, and fw denotes a focal length of the variable magnification optical system as a whole in a wide angle end state.