# US 11,079,575 B2 · Variable magnification optical system, optical device, and method for manufacturing variable magnification optical system

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- Number: US 11,079,575 B2
- Document ID: US11079575B2
- Status: Granted
- Kind: B2
- Application number: 16/338,736
- Filed: 2017-10-16
- Published: 2020-08-13
- Granted: 2021-08-03
- Earliest claimed: 2016-10-18
- Assignees: Nikon Corporation
- Applicants: Nikon Corporation
- Inventors: Tomoki Ito
- Web page: https://patentgrep.com/patent/US11079575B2

## CPC

- G02B 15/145113: {arranged +-++-}
- G02B 13/009: {having zoom function}
- G02B 15/20: having an additional movable lens or lens group for varying the objective focal length
- G02B: OPTICAL ELEMENTS, SYSTEMS OR APPARATUS

## Abstract

Comprising, in order from an object side: a first lens group having positive refractive power, a second lens group having negative refractive power, a third lens group having positive refractive power, a fourth lens group having positive refractive power, and a fifth lens group having negative refractive power; upon varying a magnification, the first lens group being fixed with respect to the image plane, and each distance between the neighboring lens groups being varied; upon focusing, at least a portion of the fourth lens group being moved; and predetermined conditional expression(s) being satisfied, thereby variations in various aberrations upon varying magnification being superbly suppressed.

## Claims

### Claim 1

A variable magnification optical system comprising, in order from an object side: a first lens group having positive refractive power, a second lens group having negative refractive power, a third lens group having positive refractive power, a fourth lens group having positive refractive power, and a fifth lens group having negative refractive power;
upon varying a magnification, the first lens group being fixed with respect to the image plane, and distances between the neighboring respective lens groups being varied;
upon focusing, at least a portion of the fourth lens group being moved; and
the following conditional expressions being satisfied:
1.20<f5/f2<2.80
0.80<f3/f4<2.20
where f5 denotes a focal length of the fifth lens group, f2 denotes a focal length of the second lens group, f3 denotes a focal length of the third lens group, and f4 denotes a focal length of the fourth lens group.

### Claim 2 (depends on 1)

A variable magnification optical system according to claim 1, wherein, upon varying magnification, the third lens group is fixed with respect to the image plane.

### Claim 3 (depends on 1)

A variable magnification optical system according to claim 1, wherein, upon varying magnification, the fifth lens group is fixed with respect to the image plane.

### Claim 4 (depends on 1)

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

### Claim 5 (depends on 1)

A variable magnification optical system according to claim 1, wherein at least a portion of the fifth lens group is movable to have a component in a direction perpendicular to the optical axis.

### Claim 6 (depends on 1)

A variable magnification optical system according to claim 1, wherein the following conditional expression is satisfied:
0.64<f4/(−f2)<2.20
where f4 denotes a focal length of the fourth lens group, and f2 denotes a focal length of the second lens group.

### Claim 7 (depends on 1)

A variable magnification optical system according to claim 1, wherein the following conditional expression is satisfied:
0.94<(−f5)/f4<3.00
where f5 denotes a focal length of the fifth lens group, and f4 denotes a focal length of the fourth lens group.

### Claim 8 (depends on 1)

A variable magnification optical system according to claim 1, wherein the following conditional expression is satisfied:
1.00<f1/(−f2)<4.50
where f1 denotes a focal length of the first lens group, and f2 denotes a focal length of the second lens group.

### Claim 9 (depends on 1)

A variable magnification optical system according to claim 1, wherein the following conditional expression is satisfied:
1.00<f3/(−f2)<4.20
where f3 denotes a focal length of the third lens group, and f2 denotes a focal length of the second lens group.

### Claim 10 (depends on 1)

A variable magnification optical system according to claim 1, wherein the following conditional expression is satisfied:
0.60<f1/(−f5)<2.70
where f1 denotes a focal length of the first lens group, and f5 denotes a focal length of the fifth lens group.

### Claim 11 (depends on 1)

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

### Claim 12

A variable magnification optical system comprising, in order from an object side: a first lens group having positive refractive power, a second lens group having negative refractive power, a third lens group having positive refractive power, a fourth lens group having positive refractive power, and a fifth lens group having negative refractive power;
upon varying a magnification, distances between the neighboring respective lens groups being varied;
an aperture stop being disposed between the second lens group and the fourth lens group; and
the following conditional expressions being satisfied:
1.55≤(−f5)/f4<3.00
1.00<f3/(−f2)<4.20
where f5 denotes a focal length of the fifth lens group, f4 denotes a focal length of the fourth lens group, f3 denotes a focal length of the third lens group, and f2 denotes a focal length of the second lens group.

### Claim 13 (depends on 12)

A variable magnification optical system according to claim 12, wherein the following conditional expression is satisfied:
1.20<f5/f2<3.60
where f5 denotes a focal length of the fifth lens group, and f2 denotes a focal length of the second lens group.

### Claim 14 (depends on 12)

A variable magnification optical system according to claim 12, wherein the following conditional expression is satisfied:
0.80<f3/f4<2.20
where f3 denotes a focal length of the third lens group, and f4 denotes a focal length of the fourth lens group.

### Claim 15 (depends on 12)

A variable magnification optical system according to claim 12, wherein the following conditional expression is satisfied:
0.64<f4/(−f2)<2.20
where f4 denotes a focal length of the fourth lens group, and f2 denotes a focal length of the second lens group.

### Claim 16 (depends on 12)

A variable magnification optical system according to claim 12, wherein the following conditional expression is satisfied:
1.00<f1/(−f2)<4.50
where f1 denotes a focal length of the first lens group, and f2 denotes a focal length of the second lens group.

### Claim 17 (depends on 12)

A variable magnification optical system according to claim 12, wherein the following conditional expression is satisfied:
0.60<f1/(−f5)<2.70
where f1 denotes a focal length of the first lens group, and f5 denotes a focal length of the fifth lens group.

### Claim 18 (depends on 12)

An optical system comprising a variable magnification optical system according to claim 12.

### Claim 19

A method for manufacturing a variable magnification optical system comprising, in order from an object side: a first lens group having positive refractive power, a second lens group having negative refractive power, a third lens group having positive refractive power, a fourth lens group having positive refractive power and a fifth lens group having negative refractive power; the method comprising one of steps (A) and (B):
step (A) including:
constituting to satisfy the following conditional expressions:
1.20<f5/f2<2.80
0.80<f3/f4<2.20
where f5 denotes a focal length of the fifth lens group, f2 denotes a focal length of the second lens group, f3 denotes a focal length of the third lens group, and f4 denotes a focal length of the fourth lens group;
constituting such that, upon varying magnification, the first lens group is fixed with respect to the image plane, and each distance between the neighboring lens groups is varied; and
constituting such that, upon focusing, at least a portion of the fourth lens group is moved along the optical axis; and
step (B) including:
constituting to satisfy the following conditional expressions:
1.55≤(−f5)/f4<3.00
1.00<f3/(−f2)<4.20
where f5 denotes a focal length of the fifth lens group, f4 denotes a focal length of the fourth lens group, f3 denotes a focal length of the third lens group, and f2 denotes a focal length of the second lens group;
constituting such that, upon varying a magnification, each distance between the neighboring lens groups is varied; and
constituting such that an aperture stop is disposed between the second lens group and the fourth lens group.