Patent ID: 7457044

Claim:
An ultra wide angle imaging optical system comprising, in order from an object side: a first lens group; an aperture stop; and a second lens group, the first lens group including, in order from a 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 including a plurality of positive lens elements, the first lens group and the second lens group each including 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, and the first lens group including the lens element satisfying the following conditional formula (1): −0.6<( Ph−Pv )*( fh+fv )<−0.1 (1) 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.