Patent ID: 7382437

Claim:
A projection optical system for projecting a pattern on an object surface onto an image surface in a reduced size, said projection optical system comprising six reflective surfaces that include, in order of reflecting light from the object surface, a first concave reflective surface, a second convex reflective surface, a third convex reflective surface, a fourth concave reflective surface, a fifth reflective surface and a sixth reflective surface, and an aperture stop along an optical path between the first and second reflective surfaces that is located apart from each of the first and second reflective surfaces, wherein a surface apex is defined, with respect to each of the six reflective surfaces, as one of nodal points between an optical axis and an approximately spherical surface that is closest to a reflection point of the light on each of the six reflective surfaces, the approximately spherical surface having a center that is defined as a center of curvature of each of the six reflective surfaces, and a radius that is defined as a radius of curvature of each of the six reflective surfaces, and wherein the surface apexes of the six reflective surfaces are arranged in order of the fourth reflective surface, the second reflective surface, the third reflective surface, the first reflective surface, the sixth reflective surface and the fifth reflective surface in order from the object surface to the image surface along an optical axis.