Patent ID: 6862408

Claim:
An image pickup system comprising a zoom lens, wherein: said zoom lens comprises a plurality of lens groups including a lens group having negative power and a lens group having positive power wherein, for zooming, the spaces between the respective lens groups are variable, said zoom lens further comprises an aperture stop, at least one lens group having negative power comprises a negative lens component having an aspheric concave surface on the side of said aperture stop, and said aspheric surface is configured to have refracting power that becomes weak with an increasing distance from an optical axis of the zoom lens and complies with the following conditions (1) and (2): 0.51 ≦a/Rh< 2.50 (1) 0.30 <Rc/R< 0.95 (2) where a is an absolute value of an axial distance from an apex of the aspheric surface (a point of intersection of the aspheric surface with the optical axis) to a position on the aspheric surface through which a chief ray passes at a maximum view angle at an wide-angle end of the zoom lens, Rh is an absolute value of a distance between the optical axis and a position on the aspheric surface through which an off-axis chief ray passes at a maximum view angle at the wide-angle end, Rc is an absolute value of a radius of curvature at the apex (an axial radius of curvature of the aspheric surface), and R is an absolute value of a radius of curvature of a spherical surface having an axis of symmetry defined by the optical axis and including an apex and a position on the aspheric surface through which a chief ray farthest off the optical axis passes, as represented by R=|(a 2 +Rh 2 )/(2a)|.