Imaging Freeform Optical Systems Designed with NURBS Surfaces
MASSACHUSETTS INST OF TECH LEXINGTON LEXINGTON United States
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The designs of two imaging freeform systems using NURBS optical surfaces are described. The first system, a three-mirror anastigmat has six times higher spatial resolution over the image plane compared with the equivalent conventional design. Analyzing the mirror surface shapes for both designs shows that the average aspheric departures per surface are the same. Alignment tolerances are tighter for the freeform design to maintain the higher spatial resolution. In the second system, a Ritchey-Chretien telescope is corrected by a two-mirror freeform system, providing a telecentric exit pupil and meeting the spatial resolution requirements for a visible to mid-wave infrared imaging spectrometer. Both of these NURBS freeform designs are possible due to a custom optical design code for fast accurate NURBS optimization FANO, and its advantages in designing freeform systems are presented.