# US 11,079,577 B2 · Variable magnification optical system, optical apparatus, and method for producing variable magnification optical system

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- Number: US 11,079,577 B2
- Document ID: US11079577B2
- Status: Granted
- Kind: B2
- Application number: 16/496,429
- Filed: 2017-04-05
- Published: 2021-04-15
- Granted: 2021-08-03
- Earliest claimed: 2017-04-05
- Assignees: Nikon Corporation
- Applicants: Nikon Corporation
- Inventors: Kosuke Machida
- Web page: https://patentgrep.com/patent/US11079577B2

## CPC

- G02B 15/1465: {the first group being negative}
- G02B 15/20: having an additional movable lens or lens group for varying the objective focal length
- G02B 13/0045: {having five or more lenses}
- G02B 13/02: Telephoto objectives, i.e. systems of the type + - in which the distance from the front vertex to the image plane is less than the equivalent focal length
- G02B 13/06: Panoramic objectives; So-called "sky lenses" {including panoramic objectives having reflecting surfaces}
- G02B 13/18: with lenses having one or more non-spherical faces, e.g. for reducing geometrical aberration {(G02B13/002 takes precedence)}
- G02B 5/005: {Diaphragms (for cameras G03B9/02)}
- G02B 13/009: {having zoom function}
- G02B: OPTICAL ELEMENTS, SYSTEMS OR APPARATUS

## Abstract

A variable magnification optical system comprising, in order from an object side, a first lens group having negative refractive power, a first intermediate lens group having positive refractive power, a second intermediate lens group having negative refractive power and a rear lens group; upon varying a magnification from a wide angle end state to a telephoto end state, a distance between the first lens group and the first intermediate lens group being varied, a distance between the first intermediate lens group and the second intermediate lens group being varied, and a distance between the second intermediate lens group and the rear lens group being varied; the rear lens group comprising at least one focusing lens group which is moved upon carrying out focusing from an infinitely distant object to a closely distant object and at least one lens component at an image side of the most image side focusing lens group in the focusing lens groups; and predetermined conditional expressions being satisfied, thereby the focusing lens group(s) being reduced in weight.

## Claims

### Claim 1

A variable magnification optical system comprising, in order from an object side, a first lens group having negative refractive power, a first intermediate lens group having positive refractive power, a second intermediate lens group having negative refractive power and a rear lens group; upon varying a magnification from a wide angle end state to a telephoto end state, a distance between said first lens group and said first intermediate lens group being varied, a distance between said first intermediate lens group and said second intermediate lens group being varied, and a distance between said second intermediate lens group and said rear lens group being varied; said rear lens group comprising at least one focusing lens group which is moved upon carrying out focusing from an infinite distance object to a close distance object and at least one lens component at an image side of the most image side focusing lens group in said focusing lens groups; and the following conditional expression being satisfied:
0.30<|fF|/|fRL|<2.50
where fF denotes a focal length of a focus lens group having a strongest refractive power in said focusing lens groups, and fRL denotes a focal length of a lens having a strongest refractive power in said at least one lens component; and wherein the following conditional expression is satisfied;
2.00 <D1Mw/fw<4.00
where D1Mw denotes a distance along the optical axis between the first lens group and the first intermediate lens group in the wide angle end state, and fw denotes a focal length of the variable magnification optical system 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:
0.70<|fF|/ft<3.30
where fF denotes a focal length of a focusing lens group having a strongest refractive power in the focusing lens groups, and ft denotes a focal length of the variable magnification optical system 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:
0.60<f1N/f1<2.00
where f1N denotes a focal length of a lens having a strongest negative refractive power in the first lens group, and f1 denotes a focal length of the first lens group.

### Claim 4 (depends on 1)

A variable magnification optical system according to claim 1, wherein
the following conditional expression is satisfied:
2.00<D1Mw/fw<4.00
where D1Mw denotes a distance along the optical axis between the first lens group and the first intermediate lens group in the wide angle end state, and fw denotes a focal length of the variable magnification optical system in the wide angle end state.

### Claim 5 (depends on 1)

A variable magnification optical system according to claim 1, wherein
the following conditional expression is satisfied:
2.00<νM1P/νM1N<3.00
where νM1P denotes an Abbe's number of a lens having a strongest positive refractive power in the first intermediate lens group, and νM1N denotes an Abbe's number of a lens having a strongest negative refractive power in the first intermediate lens group.

### Claim 6 (depends on 1)

A variable magnification optical system according to claim 1, wherein the following conditional expression is satisfied:
0.20<|fM1P/fM1N|<0.80
where fM1P denotes a focal length of a lens having a strongest positive refractive power in the first intermediate lens group, and fM1N denotes a focal length of a lens having a strongest negative refractive power in the first intermediate lens group.

### Claim 7 (depends on 1)

A variable magnification optical system according to claim 1, wherein
38.00°<ωw<85.00°
where ωw denotes a half angle of view of the variable magnification optical system in the wide angle end state.

### Claim 8 (depends on 1)

A variable magnification optical system according to claim 1, wherein said focusing lens group is composed of one or two lenses.

### Claim 9 (depends on 1)

A variable magnification optical system according to claim 1, wherein said first intermediate lens group comprises at least two lenses having negative refractive power.

### Claim 10 (depends on 1)

A variable magnification optical system according to claim 1, wherein said first lens group is composed of two lens components.

### Claim 11 (depends on 1)

A variable magnification optical system according to claim 1, wherein at least one of the focusing lens groups has positive refractive power.

### Claim 12 (depends on 1)

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

### Claim 13 (depends on 1)

A variable magnification optical system according to claim 1, wherein said rear lens group comprises at least two focusing lens groups.

### Claim 14 (depends on 1)

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

### Claim 15

A method for manufacturing a variable magnification optical system which comprises, in order from an object side, a first lens group having negative refractive power, a first intermediate lens group having positive refractive power, a second intermediate lens group having negative refractive power and a rear lens group, comprising the steps of: constructing such that, upon varying a magnification from a wide angle end state to a telephoto end state, a distance between said first lens group and said first intermediate lens group is varied, a distance between said first intermediate lens group and said second intermediate lens group is varied, and a distance between said second intermediate lens group and said rear lens group is varied; constructing such that said rear lens group comprises at least one focusing lens group which is moved upon carrying out focusing from an infinite distance object to a close distance object and at least one lens component at an image side of the most image side focusing lens group in said focusing lens groups; and constructing such that the following conditional expression is satisfied:
0.30<|fF|/|fRL|<2.50
where fF denotes a focal length of a focus lens group having a strongest refractive power in said focusing lens groups, and fRL denotes a focal length of a lens having a strongest refractive power in said at least one lens component; and wherein the following conditional expression is satisfied;
2.00 <D1Mw/fw<4.00
where D1Mw denotes a distance along the optical axis between the first lens group and the first intermediate lens group in the wide angle end state, and fw denotes a focal length of the variable magnification optical system in the 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:
0.10<BFw/fw<1.00
where BFw denotes a back focus of said variable magnification optical system in the wide angle end state, and fw denotes a focal length of said variable magnification optical system in the wide angle end state.