Patent ID: 6169637
Filing Date: 2001-01-02
Classification: G02B

Abstract:
A catadioptric lens having an overall focal length f and capable of forming an image of an object and comprising, along an optical axis: 1) a first lens group having an annular incident surface that is objectwise concave and upon which light from the object is first incident, and a most imagewise lens surface; 2) an annular main mirror arranged imagewise of said first lens group and having an objectwise concave reflective surface that reflects light objectwise; 3) a secondary mirror located objectwise of said annular main mirror and having an imagewise convex reflective surface that reflects light imagewise; and 4) a glass optical Path within said first lens group from said annular incident surface to said main mirror to said secondary mirror and to said most imagewise lens surface of said first lens group, wherein said annular incident surface satisfies the following condition: 0.5<.vertline.r.sub.a /f.vertline.<1 where r.sub.a is a radius of curvature of said annular incident surface.