Zoom optical system, optical device and method for manufacturing the zoom optical system
A first lens group (G 1 ) 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 (G 1 ) is moved with respect to an image surface, a distance between the first lens group (G 1 ) 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.
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.
2. 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,
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.
3. 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.
4. 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.
5. The zoom optical system according to claim 1 , wherein the following conditional expressions are satisfied:
−10.000< fRF/fRF 2<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.
6. 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.
7. The zoom optical system according to claim 1 , wherein the following conditional expression is satisfied:
0.390< DXnW/ZD 1<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
ZD 1 denotes a movement amount of the first lens group upon zooming from the wide-angle end state to a telephoto end state.
8. The zoom optical system according to claim 1 , wherein the following conditional expression is satisfied:
2.250< TLW/ZD 1<10.000
where TLW denotes the total length of the optical system in the wide-angle end state, and
ZD 1 denotes a movement amount of the first lens group upon zooming from the wide-angle end state to a telephoto end state.
9. The zoom optical system according to claim 1 , wherein the following conditional expression is satisfied:
−0.400<β Ft< 0.400
where βFt denotes a lateral magnification of the focusing lens group in a telephoto end state.
10. 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.
11. 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.
12. 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:
ν dp> 55.00
where νdp denotes an Abbe number of a medium of the positive lens with respect to d-line.
13. 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:
ν dn< 40.00
where νdn denotes an Abbe number of a medium of the negative lens with respect to d-line.
14. The zoom optical system according to claim 1 , wherein the following conditional expression is satisfied:
0.000<β Fw< 0.800
where βFw denotes a lateral magnification of the focusing lens group in the wide-angle end state.
15. 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.
16. 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.
17. 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.
18. 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.
19. An optical device comprising the zoom optical system according to claim 1 .
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.