Ultra wide angle imaging optical system, ultra wide angle imaging lens device, and image sensing apparatus

摘要

An ultra wide angle imaging optical system includes, in order from an object side, a first lens group, an aperture stop, and a second lens group. The first lens group includes, in order from the position closest to the object side, a negative meniscus lens element convex to the object side, a negative lens element, and a negative lens element. The second lens group includes a plurality of positive lens elements. The first lens group and the second lens group each includes at least one anamorphic surface having different optical powers with respect to a first section extending in a first direction on a flat plane substantially orthogonal to an optical axis, and with respect to a second section extending in a second direction substantially orthogonal to the first direction. The first lens group includes the lens element satisfying the following conditional formula (1): <?in-line-formulae description="In-line Formulae" end="lead"?>-0.6<(Ph-Pv)*(fh+fv)<-0.1 (1)<?in-line-formulae description="In-line Formulae" end="tail"?> where Ph: an optical power in the first direction where a viewing angle is large; Pv: an optical power in the second direction where the viewing angle is small; fh: a focal length in the first direction with respect to the entirety of the optical system; and fv: a focal length in the second direction with respect to the entirety of the optical system.