This paper describes a reflecting sight in which a mirror objective is used instead of a usual lens. The instrument becomes very small and the optical element is simple even for a large field of view. The astigmatism produced by the oblique reflecting plate is compensated by an off-center cylindrical lens. The problem is mathematically solved.
J. VOGL and S. TÄCKLIND, "A New Type of Reflecting Sight," J. Opt. Soc. Am. 37, 975-975 (1947)