Zoom optical system, optical apparatus and method for manufacturing the zoom optical system
A variable magnification optical system having a front lens group and a rear lens group arranged in order from the object side along an optical axis, the rear lens group comprising a first focusing lens group and a second focusing lens group. When the magnification is changed, the spacing between lens groups adjacent to each other changes, at the time of changing from focusing on an object at infinity to focusing on an object at a short distance, the position of the front lens group is fixed, the first and second focusing lens groups move to the image surface side along different trajectories, and the conditional expression 0.05<(−fF2)/ft<0.50 is satisfied, where fF2 is the focal length of the second focusing lens group, and ft is the focal length of the variable magnification optical system in a telephoto end state.
1. A zoom optical system consisting of a preceding lens group and a succeeding lens group that are disposed in order from an object side along an optical axis, wherein
the succeeding lens group comprises a first focusing lens group and a second focusing lens group disposed on an image surface side of the first focusing lens group and having a negative refractive power,
upon zooming, a distance between the lens groups adjacent to each other changes,
upon focusing from an infinity object to a short distance object, a position of the preceding lens group is fixed, and the first focusing lens group and the second focusing lens group move along different trajectories, and
the following conditional expressions are satisfied:
0.05<(− fF 2)/ ft< 0.50 and
0.00<1/β F 2<0.90,
where
fF2: Focal length of the second focusing lens group,
ft: Focal length of the zoom optical system in a telephoto end state, and
βF2: Lateral magnification of the second focusing lens group upon focusing on an infinity object.
2. A zoom optical system consisting of a preceding lens group and a succeeding lens group that are disposed in order from an object side along an optical axis, wherein
the preceding lens group comprises, in order from the object side along the optical axis, a first lens group having a positive refractive power and a second lens group having a negative refractive power,
the succeeding lens group comprises a first focusing lens group and a second focusing lens group disposed on an image surface side of the first focusing lens group and having a negative refractive power,
upon zooming from a wide-angle end state to a telephoto end state, a distance between the lens groups adjacent to each other changes, and the first focusing lens group and the second focusing lens group move to the object side along different trajectories,
upon focusing from an infinity object to a short distance object, the first focusing lens group and the second focusing lens group move along different trajectories, and
the following conditional expression is satisfied:
0.00<1/β F 2<0.90,
where
βF2: Lateral magnification of the second focusing lens group upon focusing on an infinity object.
3. A zoom optical system consisting of a preceding lens group and a succeeding lens group that are disposed in order from an object side along an optical axis, wherein
the succeeding lens group comprises a first focusing lens group and a second focusing lens group disposed on an image surface side of the first focusing lens group and having a negative refractive power,
upon zooming, a distance between the lens groups adjacent to each other changes,
upon focusing from an infinity object to a short distance object, a position of the preceding lens group is fixed, and the first focusing lens group and the second focusing lens group move to the image surface side along different trajectories,
the second focusing lens group comprises one positive lens and one negative lens disposed side by side in order from the object side, and
the following conditional expression is satisfied:
0.00<1/β F 2<0.90,
where
βF2: Lateral magnification of the second focusing lens group upon focusing on an infinity object.
4. The zoom optical system according to claim 1 , wherein the second focusing lens group comprises one positive lens and one negative lens disposed side by side in order from the object side.
5. The zoom optical system according to claim 3 , wherein the following conditional expression is satisfied:
ν d< 37.00,
where
νd: Abbe number of the positive lens constituting the second focusing lens group.
6. The zoom optical system according to claim 3 , wherein the following conditional expression is satisfied:
0.80< NdF 2 n/NdF 2 p< 1.25,
where
NdF2n: Refractive index of the negative lens constituting the second focusing lens group with respect to a d-line, and
NdF2p: Refractive index of the positive lens constituting the second focusing lens group with respect to the d-line.
7. The zoom optical system according to claim 1 , wherein the following conditional expression is satisfied:
0.05< MF 1 t/MF 2 t< 0.40,
where
MF1t: Movement amount of the first focusing lens group in a telephoto end state upon focusing from an infinity object to a close-range object, and
MF2t: Movement amount of the second focusing lens group in a telephoto end state upon focusing from an infinity object to a close-range object
(Movement amount is the amount of movement to the image surface side, expressed by a positive value).
8. The zoom optical system according to claim 1 , wherein the following conditional expression is satisfied:
0.04< BF 1 t/βF 2 t< 0.20,
where
βF1t: Lateral magnification of the first focusing lens group in a telephoto end state upon focusing on an infinity object, and
βF2t: Lateral magnification of the second focusing lens group in a telephoto end state upon focusing on an infinity object.
9. The zoom optical system according to claim 1 , further comprising a rear lens group disposed adjacent to the second focusing lens group on an image surface side of the second focusing lens group, wherein the following conditional expression is satisfied:
0.05<β F 1 w/βLGW< 2.50,
where
βF1w: Lateral magnification of the first focusing lens group in a wide-angle end state upon focusing on an infinity object, and
βLGw: Lateral magnification of the rear lens group in a wide-angle end state upon focusing on an infinity object.
10. The zoom optical system according to claim 1 , wherein the following conditional expression is satisfied:
0.40<(− fF 2)/ fF 1<0.80,
where
fF1: Focal length of the first focusing lens group, and
fF2: Focal length of the second focusing lens group.
11. The zoom optical system according to claim 1 , wherein a lens component with a negative refractive power is disposed at a position closest to an image surface of the succeeding lens group.
12. The zoom optical systems according to claim 1 , further comprising an aperture stop disposed on the optical axis, wherein
the first focusing lens group and the second focusing lens group are disposed closer to the image surface than the aperture stop.
13. The zoom optical systems according to claim 1 , wherein the first focusing lens group and the second focusing lens group are disposed adjacent to each other.
14. The zoom optical system according to claim 1 , wherein the following conditional expression is satisfied:
0.00<β F 1<0.90,
where
βF1: Lateral magnification of the first focusing lens group upon focusing on an infinity object.
15. The zoom optical system according to claim 1 , wherein the following conditional expression is satisfied:
{β F 1+(1/β F 1)} −2 <0.25,
where
βF1: Lateral magnification of the first focusing lens group upon focusing on an infinity object.
16. The zoom optical system according to claim 1 , wherein the following conditional expression is satisfied:
{β F 2+(1/β F 2)} −2 <0.25 T .
17. The zoom optical system according to claim 1 , wherein the preceding lens group comprises, in order from the object side along the optical axis, a first lens group having a positive refractive power, a second lens group having a negative refractive power, and a third lens group having a positive refractive power.
18. The zoom optical system according to claim 17 , wherein the following conditional expression is satisfied:
0.05<(− f 2)/ TLw< 0.30,
where
f2: Focal length of the second lens group, and
TLw: Entire length of the zoom optical system in a wide-angle end state upon focusing on an infinity object.
19. The zoom optical system according to claim 17 , wherein the following conditional expression is satisfied:
0.05< EG 1/ TLw< 0.15,
where
ΣG1: Distance from an object-side surface of the lens disposed on the object side of the first lens group to an image-surface-side surface of the lens disposed on the image surface side of the first lens group, and
TLw: Entire length of the zoom optical system in a wide-angle end state upon focusing on an infinity object.
20. The zoom optical system according to claim 17 , wherein the following conditional expression is satisfied:
0.30<(− f 2)/ f 3<0.80,
where
f2: Focal length of the second lens group, and
f3: Focal length of the third lens group.
21. An optical apparatus equipped with the zoom optical system according to claim 1 .
22. A method for manufacturing the zoom optical system consisting of a preceding lens group and a succeeding lens group disposed in order from an object side along an optical axis,
the method comprising:
arranging the preceding lens group and the succeeding lens group in a lens barrel in order from an object side along an optical axis, and
configuring the succeeding lens group to comprise a first focusing lens group and a second focusing lens group disposed on an image surface side of the first focusing lens group and having a negative refractive power,
the method further comprising one of the following features A, B and C, wherein
the feature A including:
upon zooming, changing a distance between the lens groups adjacent to each other,
upon focusing from an infinity object to a short distance object, keeping the position of the preceding lens group fixed, and moving the first focusing lens group and the second focusing lens group along different trajectories, and
satisfying the following conditional expressions:
0.05<(− fF 2)/ ft< 0.50 and
0.00<1/β F 2<0.90,
where
fF2: Focal length of the second focusing lens group,
ft: Focal length of the zoom optical system in a telephoto end state, and
βF2: Lateral magnification of the second focusing lens group upon focusing on an infinity object,
the feature B including:
configuring the preceding lens group to comprise, in order from the object side along the optical axis, a first lens group having a positive refractive power and a second lens group having a negative refractive power,
upon zooming from a wide-angle end state to a telephoto end state, changing a distance between the lens groups adjacent to each other, and moving the first focusing lens group and the second focusing lens group to the object side along different trajectories,
upon focusing from an infinity object to a short distance object, moving the first focusing lens group and the second focusing lens group along different trajectories, and
satisfying the following conditional expression:
0.00<1/β F 2<0.90,
where
βF2: Lateral magnification of the second focusing lens group upon focusing on an infinity object, and
the feature C including:
upon zooming, changing a distance between the lens groups adjacent to each other,
upon focusing from an infinity object to a short distance object, keeping a position of the preceding lens group fixed, and moving the first focusing lens group and the second focusing lens group to the image surface side along different trajectories,
configuring the second focusing lens group to comprise one positive lens and one negative lens disposed side by side in order from the object side, and
satisfying the following conditional expression:
0.00<1/β F 2<0.90,
where
βF2: Lateral magnification of the second focusing lens group upon focusing on an infinity object.