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, and
upon zooming, 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 expressions are satisfied:
0.50<| fF/fM< 5.00
where, fF denotes a focal length of the focusing lens group,
fM denotes a focal length of the intermediate lens group.
2. The zoom optical system according to claim 1 , wherein
upon zooming, the rear-side lens group is moved with respect to the image surface, and
the following conditional expressions are satisfied:
0.20<(− fXn )/ fM< 1.60
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.
3. The zoom optical system according to claim 1 , wherein
upon zooming, the first lens group is moved toward the object side and the front-side lens group is moved with respect to the image surface, and
an air lens, formed between the focusing lens group and an adjacent lens group and positioned on a side on which the focusing lens group is moved upon focusing from infinity to a short-distance object, satisfies the following conditional expression:
1.50<( rB+rA )/( rB−rA )
where, rA denotes a radius of curvature of an object side lens surface of the air lens, and
rB denotes a radius of curvature of an image side lens surface of the air lens.
4. The zoom optical system according to claim 1 further comprising a vibration-proof lens group that is disposed between the focusing lens group and a lens closest to an image in the optical system, and is configured to be movable with a displacement component in a direction orthogonal to an optical axis, wherein
the following conditional expressions are satisfied:
0.01< dV/|fV< 0.50
where, dV denotes a distance between the vibration-proof lens group and a lens disposed to the image side of the vibration-proof lens group in the telephoto end state on an optical axis,
fV denotes a focal length of the vibration-proof lens group.
5. The zoom optical system according to claim 1 , wherein
upon zooming, the front-side lens group is moved with respect to the image surface, and
the rear-side lens group is composed of two or more lens groups.
6. The zoom optical system according to claim 1 , wherein
the intermediate lens group includes an object side group and an image side group arranged in order from the object side, and
the image side group is the focusing lens group.
7. The zoom optical system according to claim 1 , wherein
the intermediate lens group includes an object side group and an image side group arranged in order from the object side,
the image side group is the focusing lens group, and
the following conditional expression is satisfied:
0.01< dAB/|fF< 0.50
where, fF denotes a focal length of the focusing lens group, and
dAB denotes a distance between the focusing lens group and a lens disposed to the object side of the focusing lens group on an optical axis, upon focusing on infinity in the telephoto end state.
8. The zoom optical system according to claim 1 , wherein the focusing lens group has positive refractive power.
9. The zoom optical system according to claim 1 , wherein
the focusing lens group includes a positive lens when having positive refractive power as a whole, and
the following conditional expressions are satisfied:
( ndp+ 0.0075×ν dp− 2.175)<0
ν dp> 50.00
where, ndp denotes a refractive index of the medium as the positive lens in the focusing lens group with respect to the d-line, and
νdp denotes Abbe number based on the d-line of the medium as the positive lens in the focusing lens group.
10. The zoom optical system according to claim 1 , wherein
the focusing lens group includes a negative lens when having negative refractive power as a whole, and
( ndn+ 0.0075×ν dn− 2.175)<0
ν dn> 50.00
where, ndn denotes a refractive index of the medium as the negative lens in the focusing lens group with respect to the d-line, and
νdn denotes Abbe number based on the d-line of the medium as the negative lens in the focusing lens group.
11. The zoom optical system according to claim 1 , wherein the first lens group is moved with respect to the image surface upon zooming.
12. The zoom optical system according to claim 1 , wherein the front-side lens group is moved with respect to the image surface upon zooming.
13. The zoom optical system according to claim 1 , wherein the intermediate lens group is moved with respect to the image surface upon zooming.
14. The zoom optical system according to claim 1 , wherein the rear-side lens group and all lens groups disposed to the image side of the rear-side lens group or at least the rear-side lens group is moved with respect to the image surface upon zooming.
15. The zoom optical system according to claim 1 , wherein the lens group with the largest absolute value of the refractive power in the negative lens groups of the front-side lens group is the second lens group.
16. The zoom optical system according to claim 1 , wherein the intermediate lens group includes one lens group integrated upon zooming.
17. The zoom optical system according to claim 1 , wherein
the focusing lens group has positive refractive power, and
a lens in the intermediate lens group is the same as a lens in the focusing lens group.
18. The zoom optical system according to claim 1 , wherein
the focusing lens group has positive refractive power, and
part of the intermediate lens group is the focusing 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, 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, and
lenses are arranged in a lens barrel in such a manner that upon zooming, 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 expressions are satisfied:
0.50<| fF/fM< 5.00
where, fF denotes a focal length of the focusing lens group,
fM denotes a focal length of the intermediate lens group.