Patent ID: 11966032
Assignee: NIKON CORPORATION
Field: Optics (Instruments)
Classification: CPC G | IPC G

Claim 20:
21. A variable magnification optical system comprising, in order from an object side, a first lens group having negative refractive power, a second lens group having positive refractive power, a third lens group and a fourth lens group;
upon varying a magnification, a distance between the first lens group and the second lens group being varied, a distance between the second lens group and the third lens group being varied, and a distance between the third lens group and the fourth lens group being varied;
the first lens group comprising a negative lens and a positive lens;
the second lens group consisting of, in order from the object side, a 2a lens group having positive refractive power, a 2b lens group and a 2c lens group;
the 2a lens group consisting of one lens component;
the 2b lens group consisting of a cemented lens constructed by a negative lens cemented with a positive lens; and
the 2c lens group consisting of one lens component;
wherein the following conditional expressions are satisfied:

1.40<f12/(−f1)<2.80

0.185<G2/TLt<0.500

80.0°<2ω<110.0°

where f12 denotes a focal length of the positive lens of the first lens group, f1 denotes a focal length of the first lens group, G2 denotes a length on the optical axis of the second lens group, TLt denotes a length on the optical axis of the variable magnification optical system as a whole in the telephoto end state and 2ω denotes an entire angle of view of the variable magnification optical system in the wide angle end state.