Patent ID: 7221517

Claim:
An image forming device comprising: a zoom lens system having a plurality of lens units and performing magnification varying by changing the distance between the lens units; and an image sensor that converts an optical image formed by the zoom lens system into an electric signal, wherein the zoom lens system comprises at least a first lens unit having negative optical power and a second lens unit having positive optical power from the object side, at least the first lens unit and the second lens unit move in zooming from the wide angle end to the telephoto end, and wherein the second lens unit comprises three lens elements of, from the object side, a positive meniscus lens element convex to the object side, a negative lens element and a positive lens element, and the following condition (1) is satisfied: −1.0<( CR 1− CR 2)/( CR 1+ CR 2)<0.0 (1) where CR 1 is the front radius of curvature of the most object side lens element in the second lens unit, and CR 2 is the rear radius of curvature of the most object side lens element in the second lens unit.