CATADIOPTRIC LENS Russian patent published in 2008 - IPC G02B17/08 

FIELD: physics.

SUBSTANCE: lens contains two-lens correction element in the form of negative and positive lenses, primary reflector, secondary convex spherical mirror with reflective coating, its convex surface facing toward the image side, and double-lens compensator in the form of biconcave and biconvex lenses provided between secondary mirror and image plane. The primary reflector is designed in the form of concave spherical mirror with reflective coating, its concave surface facing toward the object side. Biconcave lens of double-lens compensator is spaced (0.06...0.12)f' apart from biconvex lens, f' being lens focal length. The equivalent focal length of two-lens correctional element can be (6...9)f', and that of double-lens compensator (-1.5...0.9)f'.

EFFECT: increased aperture ratio, improved image quality along the whole field and better manufacturability, as well as reduced central screening.

2 cl, 4 dwg