Variable magnification optical system, optical equipment, and method for producing variable magnification optical system

A variable magnification optical system comprising a plurality of lens groups which include, in order from an object side, a first positive lens group having positive refractive power, a first negative lens group having negative refractive power, a second negative lens group disposed at a more image side than the first negative lens group and having negative refractive power, and a third negative lens group disposed at a more image side than the second negative lens group and having negative refractive power;

• upon varying a magnification, distances between adjacent lens groups being varied;
• the first negative lens group being movable with a movement component in a direction perpendicular to the optical axis as a vibration reduction lens group;
• the second negative lens group being moved along the optical axis upon carrying out focusing;
• and
• the following conditional expressions being satisfied:
• 0.010<(−f3n)/f1p<3.000
• 0.150<Bfaw/fw<0.500
• where f3n denotes a focal length of the third negative lens group, f1p denotes a focal length of the first positive lens group, Bfaw denotes an air converted back focus of the variable magnification optical system as a whole in the wide angle end state, and fw denotes a focal length of the variable magnification optical system as a whole in a wide angle end state.

A method for manufacturing a variable magnification optical system which comprises a plurality of lens groups including a first negative lens group having negative refractive power, a second negative lens group disposed at a more image side than the first negative lens group and having negative refractive power, and a third negative lens group disposed at a more image side than the second negative lens group and having negative refractive power;

• the method comprising the following steps of:
• constructing such that, upon varying a magnification, distances between the adjacent lens groups are varied;
• constructing such that one of the following features A or B is satisfied:
• the feature A comprising:
• constructing such that the second negative lens group is moved along the optical axis upon carrying out focusing, and
• constructing such that the following conditional expressions are satisfied:
• 0.500<(−f3n)/√(fw*ft)<2.500
• 0.150<Bfaw/fw<0.500
• where f3n denotes a focal length of the third negative lens group, fw denotes a focal length of the variable magnification optical system as a whole in a wide angle end state, ft denotes a focal length of the variable magnification optical system as a whole in a telephoto end state, and Bfaw denotes an air converted back focus of the variable magnification optical system as a whole in the wide angle end state;
• and
• the feature B comprising:
• constructing such that a first positive lens group having positive refractive power is disposed at a more object side than the first negative lens group;
• constructing such that the first negative lens group is movable with a movement component in a direction perpendicular to the optical axis as a vibration reduction lens group;
• constructing such that the second negative lens group is moved upon carrying out focusing, and
• constructing such that the following conditional expressions are satisfied:
• 0.010<(−f3n)/f1p<3.000
• 0.150<Bfaw/fw<0.500
• where f3n denotes a focal length of the third negative lens group, f1p denotes a focal length of the first positive lens group, Bfaw denotes an air converted back focus of the variable magnification optical system as a whole in the wide angle end state, and fw denotes a focal length of the variable magnification optical system as a whole in a wide angle end state.