Zoom optical system, optical apparatus and method for manufacturing the zoom optical system
A variable-power optical system (ZL) comprises a first lens group (G 1 ) having a negative refractive power and a succeeding lens group (GR), which are disposed on an optical axis in that order from the object side. When varying magnification from wide angle to telephoto, the space between the adjacent lens groups changes. The succeeding lens group (GR) comprises: a first focusing lens group (G 3 ) having a positive refractive power; and a second focusing lens group (G 5 ) having a positive refractive power. When focusing from infinity to a proximate distance, the first focusing lens group (G 3 ) moves toward the object side, and the second focusing lens group (G 5 ) moves toward the image side.
1. A zoom optical system essentially consisting of a first lens group having a negative refractive power and a succeeding lens group, which are disposed on an optical axis in order from an object side, wherein
the succeeding lens group comprises three or more lens groups,
distances between adjacent lens groups change upon zooming from a wide angle end to a telephoto end,
the succeeding lens group includes a first focusing lens group having a positive refractive power and a second focusing lens group having a positive refractive power, in which the second focusing lens group is placed on an image side of the first lens group,
the first focusing lens group moves toward the object side and the second focusing lens group moves toward the image side upon focusing from infinity to a short distance, and
the following conditional expressions are satisfied:
0.20< ff 1/ ff 2<1.40 and
0.10<(− f 1)/ ff 2<0.53
where,
f1: a focal length of the first lens group,
ff1: a focal length of the first focusing lens group, and
ff2: a focal length of the second focusing lens group.
2. The zoom optical system according to claim 1 , wherein the following conditional expression is satisfied:
0.01<(− MVF 1)/ MVF 2<30.0
where,
MVF1: an amount of movement of the first focusing lens group upon focusing on an object from infinity to a short distance
MVF2: an amount of movement of the second focusing lens group upon focusing on an object from infinity to a short distance
where movement of the first and second focusing lens groups toward the image side is set as positive, and movement of the first and second focusing lens groups toward the object side is set as negative.
3. The zoom optical system according to claim 1 , wherein the following conditional expression is satisfied:
0.15<(− f 1)/ ff 1<1.30.
4. The zoom optical system according to claim 1 , wherein the second focusing lens group consists of one convex lens.
5. The zoom optical system according to claim 1 , wherein the first focusing lens group consists of a cemented lens consisting of a convex lens and a concave lens.
6. The zoom optical system according to claim 1 , wherein
the succeeding lens group comprises a second lens group and a third lens group having a positive refractive power, disposed in order from the object side, and
the following conditional expression is satisfied:
0.10<(− f 1)/ f 2<1.20
where,
f2: a focal length of the second lens group.
7. The zoom optical system according to claim 1 , wherein the first lens group comprises three negative lenses disposed in order from the object side.
8. The zoom optical system according to claim 1 , wherein the following conditional expression is satisfied:
−0.80<β WF 1<0.80
where,
βWF1: lateral magnification of the first focusing lens group upon focusing on an infinity object in a wide angle end state.
9. The zoom optical system according to claim 1 , wherein the following conditional expression is satisfied:
−0.80<β WF 2<0.80
where,
βWF2: lateral magnification of the second focusing lens group upon focusing on an infinity object in a wide angle end state.
10. The zoom optical system according to claim 1 , wherein the following conditional expression is satisfied:
(β WF 1+(1/β WF 1)) −2 <0.25
where,
βWF1: lateral magnification of the first focusing lens group upon focusing on an infinity object in a wide angle end state.
11. The zoom optical system according to claim 1 , wherein the following conditional expression is satisfied:
(β WF 2+(1/β WF 2)) −2 <0.25
where,
βWF2: lateral magnification of the second focusing lens group upon focusing on an infinity object in a wide angle end state.
12. An optical apparatus comprising the zoom optical system according to claim 1 .
13. A zoom optical system comprising a first lens group having a negative refractive power and a succeeding lens group, which are disposed on an optical axis in order from an object side, wherein
distances between the adjacent lens groups change upon zooming from a wide angle end to a telephoto end,
the succeeding lens group comprises a first focusing lens group having a positive refractive power and a second focusing lens group having a positive refractive power,
the first focusing lens group and the second focusing lens group move respectively along different loci, and
the following conditional expressions are satisfied:
0.20< ff 1/ ff 2<1.40 and
0.10<(− f 1)/ ff 2<0.53
where,
f1: a focal length of the first lens group,
ff1: a focal length of the first focusing lens group, and
ff2: a focal length of the second focusing lens group.
14. The zoom optical system according to claim 13 , wherein the following conditional expression is satisfied:
0.15<(− f 1)/ ff 1<1.30.
15. The zoom optical system according to claim 13 , wherein
the succeeding lens group comprises a second lens group and a third lens group having a positive refractive power, disposed in order from the object side, and
the following conditional expression is satisfied:
0.10<(− f 1)/ f 2<1.20
where,
f2: a focal length of the second lens group.
16. An optical apparatus comprising the zoom optical system according to claim 13 .
17. A method for manufacturing a zoom optical system comprising:
arranging, in a lens barrel and on an optical axis in order from an object side, a first lens group having a negative refractive power and a succeeding lens group,
arranging the first lens group and the succeeding lens group so that a distances between adjacent lens groups change upon zooming from a wide angle end to a telephoto end,
configuring the succeeding lens group to comprise a first focusing lens group having a positive refractive power and a second focusing lens group having a positive refractive power,
the method further comprising one of the following features A or B,
the feature A including:
the zoom optical system essentially consisting of the first lens group and the succeeding lens group,
configuring the succeeding lens group to comprise three or more lens groups,
arranging the second focusing lens group to be on an image side of the first lens group,
arranging the first focusing lens group to move toward the object side and the second focusing lens group to move toward the image side upon focusing from infinity to a short distance, and
satisfying the following conditional expressions:
0.20< ff 1/ ff 2<1.40 and
0.10<(− f 1)/ ff 2<0.53
where,
f1: a focal length of the first lens group,
ff1: a focal length of the first focusing lens group, and
ff2: a focal length of the second focusing lens group,
the feature B including:
arranging the first focusing lens group and the second focusing lens group to move respectively along different loci, and
satisfying the following conditional expressions:
0.20< ff 1/ ff 2<1.40 and
0.10<(− f 1)/ ff 2<0.53
where,
f1: a focal length of the first lens group,
ff1: a focal length of the first focusing lens group, and
ff2: a focal length of the second focusing lens group.