Patent Number: 6,169,637

Title: Catadioptric lens

Abstract: A catadioptric lens (10) comprising, along an optical axis (AX), a first lens group (L.sub.1) having an objectwise concave annular incident surface (SI) upon which light from an object is first incident, and a most imagewise lens surface (16). The catadioptric lens further includes an annular main mirror (MM) arranged imagewise of the first lens group and having an objectwise concave reflective surface (R.sub.1) that reflects light objectwise. A secondary mirror (MS) is located objectwise of the annular main mirror and has an imagewise convex reflective surface (R2) that reflects light imagewise. The first lens group has a glass optical path from the incident surface to the main mirror to the secondary mirror and to the most imagewise lens surface of the first lens group. The catadioptric lens may also include a second lens group L.sub.2 imagewise of the first lens group. The second lens group may include two or more lenses, and preferably includes a cemented doublet (L.sub.34, L.sub.35). The catadioptric lens also preferably satisfies one or more of a number of design conditions.

Inventors: Tsunashima; Teruyoshi (Tokyo, JP)

Assignee: Nikon Corporation

International Classification: G02B 17/08 (20060101); G02B 017/00 ()

Expiration Date: 01/02/2018