Patent ID: 6856467

Claim:
An image pickup system comprising a zoom lens and an image pickup plane located on an image side of the zoom lens, wherein: said zoom lens comprises, in order from an object side of said zoom lens, a first lens group of negative refracting power comprising a negative lens element having an aspheric surface and a positive lens element, a second lens group comprising, in order from an object side thereof, a positive single lens element L 21 , a doublet component of positive refracting power wherein a positive lens element L 22 and a negative lens element L 23 are cemented together in this order and which is in a meniscus form convex toward the object side and a positive single lens element L 24 , wherein two or more surfaces except a cementing surface in said doublet component are each defined by an aspheric surface, and a third lens group composed of one positive lens component, wherein: for zooming from a wide-angle end to a telephoto end of said zoom lens focused on an object point at infinity, said second lens group moves only toward the object side, said third lens group moves in a locus different from that of said second lens group, said third lens moves for focusing, and the following conditions (1) and (2) are satisfied: −0.4<( R 21F +R 21R )/( R 21F −R 21R )<0.3 (1) 1.4<−β 2T <2.1 (2) where R 21F is an axial radius of curvature of an object side-surface of the single lens element L 21 in the second lens group, R 21R is an axial radius of curvature of an image side-surface of the single lens element L 21 in the second lens group, and β 2T is a magnification of the second lens group at the telephoto end focused on an object point at infinity.