The reflective projection system has a relatively wide field of view that comprises two concave and two convex spherical mirrors, situated in certain non-light-blocking positions with respect to one another, for deriving, with negligible image aberrations, a projected magnified or demagnified image over...http://www.google.de/patents/US5410434?utm_source=gb-gplus-sharePatent US5410434 - Reflective projection system comprising four spherical mirrors
