Zoom optical system, optical device and method for manufacturing the zoom optical system

A method for manufacturing a zoom optical system, comprising:

• arranging a first lens group having positive refractive power, a front-side lens group, an intermediate lens group having positive refractive power, and a rear-side lens group in order from an object side,
• the front-side lens group being composed of one or more lens groups and having a negative lens group,
• at least part of the intermediate lens group being a vibration-proof lens group that is movable with a displacement component in a direction orthogonal to an optical axis, and at least part of the intermediate lens group being a focusing lens group,
• the rear-side lens group being composed of one or more lens groups,
• the arrangement being such that upon zooming, a distance between the first lens group and the front-side lens group is changed, a distance between the front-side lens group and the intermediate lens group is changed, and a distance between the intermediate lens group and the rear-side lens group is changed;
• and
• satisfying the following conditional expression:
• 0.2
• <
• (
• -
• fXn
• )
• /
• fM
• <
• 1.6
• where
• fM denotes a focal length of the intermediate lens group, and
• fXn denotes a focal length of a lens group with a largest absolute value of refractive power in a negative lens group of the front-side lens group.