Mirror lens, especially for observatory cameras

摘要

The mirror lens has a collecting mirror and a correcting plate. The latter is arranged on the side of the mirror on which light is incident. The plate is deformed with fourth order aspherical surfaces on both sides, and has at least one surface with aspherical deformation whose order is greater than four. When a parabolic mirror is used, the plate has a spacing from it which is equal to the focal length. When an elliptically flattened mirror is used, this spacing is greater than the paraxial focal length, and when a hyperbolic mirror is used, this spacing is less than the paraxial focal length.