Asymmetric aspheric optical surfaces are very difficult to fabricate using classical techniques and laps the same size as the workpiece. Opticians can produce such surfaces by hand grinding and polishing, using small laps with orbital tool motion. However, this is a time consuming process unsuitable for large optical elements.
Robert A. Jones,
"Computer Controlled Optical Surfacing With Orbital Tool Motion", Proc. SPIE 0540, Southwest Conf on Optics '85, (20 November 1985); doi: 10.1117/12.976090; https://doi.org/10.1117/12.976090