A wide-angle zoom lens is disclosed having five lens groups of negative, positive, positive, negative, and positive refractive power, respectively, in sequential order from the magnification side. The first lens group is fixed during zooming and is formed of first and second subgroups, each of negative...http://www.google.com.au/patents/US20020181120?utm_source=gb-gplus-sharePatent US20020181120 - Wide-angle zoom lens and projection-type display unit using it
