Zoom optical system, optical device and method for manufacturing the zoom optical system
A zoom optical system comprises, 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. 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 and distances between the first lens group and the front-side lens group, between the front-side lens group and the intermediate lens group, and between the intermediate lens group and the rear-side lens group change. The following conditional expressions are satisfied: −0.750< fF/fRF <4.000 2.250< TLW/ZD 1<5.000 32.000≤ Wω 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, TLW denotes an entire length of the optical system in a wide angle end state, ZD1 denotes a movement amount of the first lens group upon zooming from the wide angle end state to a telephoto end state, and Wω denotes a half angle of view in the wide angle end state.
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 expressions are satisfied:
−0.750 <fF/fRF< 4.000
2.250 <TLW/ZD 1<5.000
32.000 ≤Wω
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,
TLW denotes an entire length of the optical system in a wide angle end state,
ZD1 denotes a movement amount of the first lens group upon zooming from the wide angle end state to a telephoto end state, and
Wω denotes a half angle of view in the wide angle end state.
2. The zoom optical system according to claim 1 , wherein the following conditional expression is satisfied:
0.650 <|fF/fXR |<6.000
where
fXR denotes a focal length of a lens group closet to the image surface in the front-side lens group.
3. The zoom optical system according to claim 1 , wherein the following conditional expression is satisfied:
0.010 <fF/fXR< 3.400
where
fXR denotes a focal length of a lens group closet to the image surface in the front-side lens group.
4. The zoom optical system according to claim 1 , wherein the following conditional expression is satisfied:
0.428<(− fXn )/ 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, and
fXR denotes a focal length of a lens group closet to the image surface in the front-side lens group.
5. The zoom optical system according to claim 1 , wherein the following conditional expression is satisfied:
0.50 <|fF|/fM< 1.60
where
fM denotes a focal length of the intermediate lens group.
6. The zoom optical system according to claim 1 , wherein the following conditional expression is satisfied:
0.51<(− 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, and
fM denotes a focal length of the intermediate lens group.
7. The zoom optical system according to claim 1 , wherein the following conditional expression is satisfied:
1.000 <DGXR/fXR< 1.500
where
DGXR denotes a thickness of the lens group closest to an image in the front-side lens group on an optical axis, and
fXR denotes a focal length of a lens group closet to the image surface in the front-side lens group.
8. 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 end state.
9. 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.
10. A method for manufacturing a zoom optical system, comprising:
arranging, in a lens barrel and 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,
the front-side lens group being composed of one or more lens groups and having a negative lens group,
at least part of the intermediate lens group being a focusing lens group,
the rear-side lens group being composed of one or more lens groups,
the arrangement being such 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
satisfying the following conditional expressions:
−0.750 <fF/fRF< 4.000
2.250 <TLW/ZD 1<5.000
32.000 ≤Wω
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,
TLW denotes an entire length of the optical system in a wide angle end state,
ZD1 denotes a movement amount of the first lens group upon zooming from the wide angle end state to a telephoto end state, and
Wω denotes a half angle of view in the wide angle end state.