Variable-power imaging optical system and imaging device

摘要

A variable-power imaging optical system is provided and includes three, negative, positive and positive lenses. A first group includes a negative lens and a positive lens. A second lens group includes a positive lens, a negative lens and an aberration-correcting lens. A third lens group includes an aberration-correcting lens L₆. During zooming, the first and second lens groups are independently moved from each other. During focusing, the first and second lens groups are moved jointly. Ng2>1.6, nug2<29 and TL/YIM<11.0 are satisfied. (Ng2: refractive index of the second lens L₂, nug₂: Abbe number of the second lens L₂, TL: maximum lens-system overall length, YIM: image height (a half length of a diagonal line).)