A Dyson lens system includes a radiation source, a concave mirror, and a plano-convex lens. There is also incorporated in the system an additional lens that is spaced from the plano-convex lens a large part of the distance from the plano-convex lens to the mirror. A roof prism and a turning prism are...http://www.google.de/patents/US5559629?utm_source=gb-gplus-sharePatent US5559629 - Unit magnification projection system and method
