# US 2019/0170989 A1 · Zoom optical system, optical device and method for manufacturing the zoom optical system

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- Number: US 2019/0170989 A1
- Document ID: US20190170989A1
- Status: Published application
- Kind: A1
- Application number: 16/270,568
- Filed: 2019-02-07
- Published: 2019-06-06
- Earliest claimed: 2014-08-29
- Assignees: Nikon Corporation
- Applicants: Nikon Corporation
- Inventors: Satoru SHIBATA; Tomoyuki SASHIMA
- Web page: https://patentgrep.com/patent/US20190170989A1

## CPC

- G02B 15/145113: {arranged +-++-}
- G02B 15/145105: {arranged +-+--}
- G02B 15/145121: {arranged +-+-+}
- G02B 15/145129: {arranged +-+++}
- G02B 15/1461: {the first group being positive}
- G02B 15/173: arranged +-+
- G02B 15/20: having an additional movable lens or lens group for varying the objective focal length
- 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: OPTICAL ELEMENTS, SYSTEMS OR APPARATUS

## Abstract

A first lens group (G1) having positive refractive power, a front-side lens group (GX), an intermediate lens group (GM) having positive refractive power, and a rear-side lens group (GR) are arranged in order from an object side. The front-side lens group (GX) is composed of one or more lens groups and has a negative lens group At least part of the intermediate lens group (GM) is a focusing lens group(GF). The rear-side lens group (GR) is composed of one or more lens groups. Upon zooming, the first lens group (G1) is moved with respect to an image surface, a distance between the first lens group (G1) and the front-side lens group (GX) is changed, a distance between the front-side lens group (GX) and the intermediate lens group (GM) is changed, and a distance between the intermediate lens group (GM) and the rear-side lens group (GR) is changed.

## Claims

### Claim 1

A zoom optical system comprising, in order from an object side:
a first lens group having positive refractive power;
a front-side lens group;
an intermediate lens group having positive refractive power; and
a rear-side lens group,
wherein
the front-side lens group is composed of one or more lens groups and has a negative lens group,
at least part of the intermediate lens group is a focusing lens group,
the rear-side lens group is composed of one or more lens groups,
upon zooming, the first lens group is moved with respect to an image surface, a distance between the first lens group and the front-side lens group is changed, a distance between the front-side lens group and the intermediate lens group is changed and a distance between the intermediate lens group and the rear-side lens group is changed, and
the following conditional expression is satisfied:
0.010<fF/Fw<8.000
where fF denotes a focal length of the focusing lens group, and
fW denotes a focal length of the entire system in a wide-angle end state.

### Claim 2 (depends on 1)

The zoom optical system according to claim 1, wherein upon zooming, the intermediate lens group is moved, the rear-side lens group is composed of two or more lens groups,
upon zooming from the wide-angle end state to a telephoto end state, the intermediate lens group moves toward the object side, and a distance between the intermediate lens group and the rear-side lens group increases, and
the following conditional expressions are satisfied:
0.170<|fF/fRF|<10.000
0.010<(DMRT−DMRW)/fF<1.000
32.000≤Wω
Tω≤20.000
where fF denotes a focal length of the focusing lens group,
fRF denotes a focal length of a lens group closet to the object side in the rear-side lens group, p1 DMRW denotes a distance between the intermediate lens group and a lens group closest to the object side in the rear-side lens group in the wide-angle end state,
DMRT denotes a distance between the intermediate lens group and the lens group closest to the object side in the rear-side lens group in the telephoto end state,
Wω denotes a half angle of view in the wide-angle end state, and
Tω denotes a half angle of view in the telephoto end state.

### Claim 3 (depends on 1)

The zoom optical system according to claim 1, wherein the following conditional expressions are satisfied:
0.001<DXRFT/fF<1.500
Tω≤20.000
0.100<DGXR/fXR<1.500
where DXRFT denotes a distance between a lens group closest to the image surface in the front-side lens group and the focusing lens group in a telephoto end state,
fF denotes a focal length of the focusing lens group,
Tω denotes a half angle of view in the telephoto end state,
DGXR denotes a thickness, on an optical axis, of a lens group closest to the image surface in the front-side lens group, and
fXR denotes a focal length of a lens group closest to an image in the front-side lens group.

### Claim 4 (depends on 1)

The zoom optical system according to claim 1, wherein the following conditional expressions are satisfied:
−10.000<fF/fRF<10.000
0.010<fF/fXR<10.000
0.100<DGXR/fXR<1.500
where fF denotes a focal length of the focusing lens group, fRF denotes a focal length of a lens group closest to the object side in the rear-side lens group,
fXR denotes a focal length of a lens group closest to the image surface in the front-side lens group, and
DGXR denotes a thickness, on an optical axis, of a lens group closest to the image surface in the front-side lens group.

### Claim 5 (depends on 1)

The zoom optical system according to claim 1, wherein the following conditional expressions are satisfied:
−10.000<fRF/fRF2<10.000
0.100<DGXR/fXR<1.500
where fRF denotes a focal length of a lens group closest to the object side in the rear-side lens group,
fRF2 denotes a focal length of a lens group second closest to the object side in the rear-side lens group,
DGXR denotes a thickness, on an optical axis, of a lens group closest to the image surface in the front-side lens group, and
fXR denotes a focal length of a lens group closest to the image surface in the front-side lens group.

### Claim 6 (depends on 1)

The zoom optical system according to claim 1, wherein the following conditional expressions are satisfied:
010<(−fXn)/fXR<1.000
0.100<DGXR/fXR<1.500
where fXn denotes a focal length of a lens group with a largest absolute value of refractive power in a negative lens group of the front-side lens group,
fXR denotes a focal length of a lens group closest to the image surface in the front-side lens group, and
DGXR denotes a thickness, on an optical axis, of a lens group closest to the image surface in the front-side lens group.

### Claim 7 (depends on 1)

The zoom optical system according to claim 1, wherein the following conditional expression is satisfied:
0.390<DXnW/ZD1<5.000
where DXnW denotes a distance between a lens group with a largest absolute value of refractive power in negative lens groups of the front-side lens group in the wide-angle end state and a lens group closest to the image surface in the front-side lens group, and
ZD1 denotes a movement amount of the first lens group upon zooming from the wide-angle end state to a telephoto end state.

### Claim 8 (depends on 1)

The zoom optical system according to claim 1, wherein the following conditional expression is satisfied:
2.250<TLW/ZD1<10.000
where TLW denotes the total length of the optical system in the wide-angle end state, and
ZD1 denotes a movement amount of the first lens group upon zooming from the wide-angle end state to a telephoto end state.

### Claim 9 (depends on 1)

The zoom optical system according to claim 1, wherein the following conditional expression is satisfied:
−0.400<βFt<0.400
where βFt denotes a lateral magnification of the focusing lens group in a telephoto end state.

### Claim 10 (depends on 1)

The zoom optical system according to claim 1, wherein the following conditional expression is satisfied:
1.250<(rB+rA)/(rB−rA)<10.000
where rA denotes a radius of curvature of a lens surface facing a lens surface closest to the object side in the focusing lens group with a distance in between, and
rB denotes a radius of curvature of the lens surface closest to the object side in the focusing lens group.

### Claim 11 (depends on 1)

The zoom optical system according to claim 1, wherein the following conditional expression is satisfied:
−0.500<(rC+rB)/(rC−rB)<0.500
where rB denotes a radius of curvature of the lens surface closest to the object side in the focusing lens group, and
rC denotes a radius of curvature of the lens surface closet to an image side in the focusing lens group.

### Claim 12 (depends on 1)

The zoom optical system according to claim 1, wherein
the focusing lens group includes at least a positive lens, and
the following conditional expression is satisfied:
υdp>55.00
where υdp denotes an Abbe number of a medium of the positive lens with respect to d-line.

### Claim 13 (depends on 1)

The zoom optical system according to claim 1, wherein
the focusing lens group includes at least a negative lens, and
the following conditional expression is satisfied:
υdn<40.00
where vdn denotes an Abbe number of a medium of the negative lens with respect to d-line.

### Claim 14 (depends on 1)

The zoom optical system according to claim 1, wherein the following conditional expression is satisfied:
0.000<βFw<0.800
where βFw denotes a lateral magnification of the focusing lens group in the wide-angle end state.

### Claim 15 (depends on 1)

The zoom optical system according to claim 1, wherein the following conditional expression is satisfied:
32.000≤Wω
where Wω denotes a half angle of view in the wide-angle end state.

### Claim 16 (depends on 1)

The zoom optical system according to claim 1, wherein the following conditional expression is satisfied:
Tω≤20.000
where Tω denotes a half angle of view in the telephoto-angle end state.

### Claim 17 (depends on 1)

The zoom optical system according to claim 1, wherein the following conditional expression is satisfied:
0.010<|fF/fXR|<10.000
where fF denotes a focal length of the focusing lens group, and
fXR denotes a focal length of a lens group closest to the image surface in the front-side lens group.

### Claim 18 (depends on 1)

The zoom optical system according to claim 1, wherein the following conditional expression is satisfied:
0.100<DGXR/fXR<1.500
where DGXR denotes a thickness, on an optical axis, of a lens group closest to the image surface in the front-side lens group, and
fXR denotes a focal length of a lens group closest to the image surface in the front-side lens group.

### Claim 19 (depends on 1)

An optical device comprising the zoom optical system according to claim 1.

### Claim 20

A method for manufacturing a zoom optical system, comprising:
arranging, in order from an object side, a first lens group having positive refractive power, a front-side lens group, an intermediate lens group having positive refractive power, and a rear-side lens group,
wherein the front-side lens group is composed of one or more lens groups and has a negative lens group,
at least part of the intermediate lens group is a focusing lens group,
the rear-side lens group is composed of one or more lens groups,
the lens groups are arranged in a lens barrel in such a manner that, upon zooming, the first lens group is moved with respect to an image surface, a distance between the first lens group and the front-side lens group is changed, a distance between the front-side lens group and the intermediate lens group is changed and a distance between the intermediate lens group and the rear-side lens group is changed, and
the following conditional expression is satisfied:
0.010<fF/fW<8.000
where fF denotes a focal length of the focusing lens group, and
fW denotes a focal length of the entire system in a wide-angle end state.