Wide-angle zoom lens

Abstract

A wide-angle zoom lens is disclosed having four lens groups of negative, positive, positive, and positive refractive power, in order from the object side. By satisfying prescribed conditions, the overall length as well as the outer diameter of the wide-angle zoom lens can be kept small, the number of lens elements required can be minimized so as to keep manufacturing costs low, yet a high-quality image is provided over the entire range of zoom. During zooming, the first and fourth lens groups remain in a fixed position while the second and third lens groups are moved along the optical axis. The first lens group G.sub.1 includes at least one negative lens element with a concave surface of strong curvature on the image side. The second lens group G.sub.2 has at least one biconvex lens. The third lens group G.sub.3 may consist of a single positive lens. The following conditions are satisfied: -2.5<f.sub.1 /f.sub.w <-1.5 2.0<f.sub.2 /f.sub.w <4.0 where f.sub.1 of the focal distance of the first lens group G.sub.1, f.sub.w is the focal distance of the zoom lens at the wide-angle end, and f.sub.2 is the focal distance of the second lens group G.sub.2. Further, a diaphragm which serves as an aperture stop may be positioned between the first lens group and the second lens group to vary the brightness in the image plane as well as to control certain aberrations, and to ensure the outer diameter of the first lens group is small

Dependencies are inferred from the claim text.