Variable-Magnification Optical System, Imaging Optical Device, and Digital Appliance

摘要

A variable-magnification optical system has five lens groups, namely, from object side, positive, negative, positive, positive, and negative lens groups, and achieves magnification variation by varying all axial distances between the lens groups. Focusing is achieved by moving the fourth lens group in optical axis direction. Vibration correction is achieved by moving all or part of the fifth lens group perpendicularly to optical axis. Fulfilled are formulae 4.0<|f1/f2|<6.0, 1.0

主权项

1. A variable-magnification optical system comprising, from an object side, a first lens group having a positive optical power, a second lens group having a negative optical power, a third lens group having a positive optical power, a fourth lens group having a positive optical power, and a fifth lens group having a negative optical power,
the variable-magnification optical system achieving magnification variation by varying axial distances between the lens groups, the variable-magnification optical system achieving focusing by moving the fourth lens group along an optical axis, the variable-magnification optical system achieving vibration correction by moving a sub group including a most image-side lens element within the second lens group on a plane perpendicular to an optical axis, wherein Formula (7) below is fulfilled:
M/N<0.5   (7) where M represents a number of lens elements composing the sub group; and N represents a number of lens elements composing the second lens group, lens elements constituting a doublet lens element being counted individually.