LARGE-FIELD UNIT-MAGNIFICATION PROJECTION OPTICAL SYSTEM

摘要

A large-field unit-magnification projection optical system (200) includes an optical axis (A2), a spherical concave mirror (Ml), a lens group with positive refracting power arranged adjacent the mirror with an air space therebetween, and a pair of prisms (P 1, P2) each laving respective first and second surface. The lens group includes a first plano-convex lens (El), a negative meniscus lens (E2) adjacent the plano-convex lens, a positive lens (E3) adjacent the negative meniscus lens, a negative double-convex lens (E4) spaced apart far from the positive lens, and a second plano-convex lens (ES). The second surface of the prism is arranged adjacent the flat surface of the plano-convex lens element on opposite sides of the optical axis, and the first surfaces of the prisms are arranged adjacent object planes and image plane, respectively. In this projection optical system, the object plane is parallel to the image plane.