Precisely curved, lightweight and low-cost reflectors for electromagnetic radiation are fabricated by use of a tool and a process in which a blank is planar stretched by uniformly applied isotropic and radially extending forces followed by deformation of the stretched blank to a precisely curved sur...http://www.google.es/patents/US4413500?utm_source=gb-gplus-sharePatente US4413500 - Tool for forming precisely curved surfaces
