Patent US 8,947,778

New families of two mirror unobscured telescopes with compact Schiefspiegler, eccentric pupil Cassegrain geometries, incorporating aspheres, tilted and decentered secondaries, and tilted decentered focal surfaces. These variables allow control of focal surface tilt. All embodiments, from f/5 to f/16, are totally reflecting, fully baffled systems, with wide diffraction limited FOVs and unobscured aperture MTFs. Systems optimized with the focal plane normal to the gut ray are well suited for visual and general use. They can incorporate a variable iris for f/number control and allow focusing along the gut ray with minimal field tilt. Systems optimized with a fixed focal plane tilt are well suited for high resolution, wide field collimators and IR scene generators. Any light reflected at focus can be trapped, eliminating Narcissus or “cats eye” effects. Additionally, this reflection can be used to provide a uniform “background” irradiance field.