New Freeform NURBS Imaging Design Code

A new optical imaging design code for NURBS freeform surfaces is described, with reduced optimization cycle times due to its fast raytrace engine, and the ability to handle larger NURBS surfaces because of its improved optimization algorithms. This program, FANO (Fast Accurate NURBS Optimization), is then applied to an f/2 three mirror anastigmat design. Given the same optical design parameters, the optical system with NURBS freeform surfaces has an average r.m.s. spot size of 4 microns. This spot size is six times smaller than the conventional aspheric design, showing that the use of NURBS freeform surfaces can improve the performance of three mirror anastigmats for the next generation of smaller pixel size, larger format detector arrays.