Design of optical surfaces conform the hyperbolic Monge-Ampère equationM.W.M.C. Bertens, M.J.H. Anthonissen, W.L. IJzerman and J.H.M. ten Thije BoonkkampEPJ Web Conf., 266 (2022) 02003DOI: https://doi.org/10.1051/epjconf/202226602003