A new method-of generating aspheric elements is discussed. In this method, the aspheric element is produced by sputtering a non-uniform, but radially symmetric. coatino onto the substrate. The desired non-uniformity is produced by selective masking of the substrate. As proof of the concept, an 8.25-inch diameter aspheric element was made. This asphere has a maximum departure from spherical of 84pm and a maximum slope deviation from spherical of 132µm/in. The finished sputtered asphere departed from the design asphere by 0.38µm.
"Aspheric Generation By Sputtering Techniques", Proc. SPIE 0126, Clever Optics: Innovative Applications of Optics, (21 November 1977); doi: 10.1117/12.955892; https://doi.org/10.1117/12.955892