Patent ID: 11892610
Assignee: NIKON CORPORATION
Field: Optics (Instruments)
Classification: CPC G | IPC G

Claim 7:
8. A method for manufacturing a variable magnification optical system, comprising:
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 rear lens group;
constructing such that, upon zooming, a distance between the first lens group and the second lens group, a distance between the second lens group and the third lens group, and a distance between the third lens group and the rear lens group are varied, and the second lens group and the third lens group are moved;
satisfying the following conditional expression:

5.00<f1/(−f2)<10.00

where f1 denotes a focal length of the first lens group, and f2 denotes a focal length of the second lens group; and
at least one lens satisfying the following conditional expressions:

1.928<ndh  (7)

28.60<νdh  (8)

where ndh denotes refractive index at d-line (wavelength λ=587.6 nm) of the lens, and νdh denotes Abbe number at d-line (wavelength λ=587.6 nm) of the lens.