Four-mirror unobscured anastigmatic telescopes with all-spherical surfaces.


A variety of four-mirror telescopes are described, all corrected for spherical aberration, coma, and astigmatism; all unobscured; and all with spherical surfaces. Performance is discussed with an afocal beam expander and a flat-field telescope as typical design examples. 
DOI: 10.1364/AO.17.001072


8 Figures and Tables