Patent ID: 11933950
Assignee: NIKON CORPORATION
Field: Optics (Instruments)
Classification: CPC G | IPC G

Claim 11:
12. A method for manufacturing a variable magnification optical system comprising at least one of the following features (A) and (B):
(A) arranging, in order from an object side, a first lens group having positive refractive power, a second lens group having negative refractive power, a third lens group having positive refractive power, and a fourth lens group having negative refractive power;
constructing such that, upon varying a magnification, a distance between the first lens group and the second lens group is varied, a distance between the second lens group and the third lens group is varied, and a distance between the third lens group and the fourth lens group is varied;
constructing such that, upon focusing, the fourth lens group is moved;
satisfying the following conditional expressions:

0.55<f2/f4<1.40

1.40<f1/fw<2.80

0.82<(−f2)/f3<1.30

2.00<f1/(−f2)<3.50

where f1 denotes a focal length of the first lens group; f2 denotes a focal length of the second lens group; f3 denotes a focal length of the third lens group; f4 denotes a focal length of the fourth lens group; and fw denotes a focal length of the variable magnification optical system in the wide angle end state;
arranging a vibration reduction lens group that is movable to have a displacement component in a direction perpendicular to the optical axis; and
satisfying the following conditional expression:

0.70<|fvr|/f3<1.60

where fvr denotes a focal length of the vibration reduction lens group,
(B) arranging, in order from an object side, a first lens group having positive refractive power, a second lens group having negative refractive power, a third lens group having positive refractive power, a fourth lens group having negative refractive power, and a fifth lens group having positive refractive power;
constructing such that, upon varying a magnification, a distance between the first lens group and the second lens group is varied, a distance between the second lens group and the third lens group is varied, a distance between the third lens group and the fourth lens group is varied, and a distance between the fourth lens group and the fifth lens group is varied;
constructing such that, upon focusing, the fourth lens group is moved;
arranging a vibration reduction lens group that is movable to have a displacement component in a direction perpendicular to the optical axis; and
satisfying the following conditional expressions:

1.067≤|fvr|/f3<1.60

0.55<f2/f4<1.40

where f3 denotes a focal length of the third lens group; fvr denotes a focal length of the vibration reduction lens group; f2 denotes a focal length of the second lens group; and f4 denotes a focal length of the fourth lens group.