Variable magnification optical system, optical device, and method for manufacturing variable magnification optical system

A variable magnification optical system comprising, 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 positive refractive power, and a fifth lens group having negative refractive power;
• upon varying a magnification, distances between the neighboring respective lens groups being varied;
• an aperture stop being disposed between the second lens group and the fourth lens group;
• and
• the following conditional expressions being satisfied:
• 1.55≤(−f5)/f4<3.00
• 1.00<f3/(−f2)<4.20
• where f5 denotes a focal length of the fifth lens group, f4 denotes a focal length of the fourth lens group, f3 denotes a focal length of the third lens group, and f2 denotes a focal length of the second lens group.

A method for manufacturing a variable magnification optical system comprising, 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 positive refractive power and a fifth lens group having negative refractive power;
• the method comprising one of steps (A) and (B):
• step (A) including:
• constituting to satisfy the following conditional expressions:
• 1.20<f5/f2<2.80
• 0.80<f3/f4<2.20
• where f5 denotes a focal length of the fifth lens group, f2 denotes a focal length of the second lens group, f3 denotes a focal length of the third lens group, and f4 denotes a focal length of the fourth lens group;
• constituting such that, upon varying magnification, the first lens group is fixed with respect to the image plane, and each distance between the neighboring lens groups is varied;
• and
• constituting such that, upon focusing, at least a portion of the fourth lens group is moved along the optical axis;
• and
• step (B) including:
• constituting to satisfy the following conditional expressions:
• 1.55≤(−f5)/f4<3.00
• 1.00<f3/(−f2)<4.20
• where f5 denotes a focal length of the fifth lens group, f4 denotes a focal length of the fourth lens group, f3 denotes a focal length of the third lens group, and f2 denotes a focal length of the second lens group;
• constituting such that, upon varying a magnification, each distance between the neighboring lens groups is varied;
• and
• constituting such that an aperture stop is disposed between the second lens group and the fourth lens group.