Patent ID: 8102510
Filing Date: 2012-01-24
Classification: G02B,G03F

Abstract:
1. 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 reflective surface, a second reflective surface, a third reflective surface, a fourth reflective surface, a fifth reflective surface and a sixth reflective surface, wherein intersecting points formed between a principal ray from an object point in a center of an arc illuminated area on the object surface and the first to the fourth reflective surface are respectively defined as a first intersecting point to a fourth intersecting point, in a predetermined plane, wherein said predetermined plane is a plane that includes the center of the arc illuminated area and an optical axis, wherein a value of maximum value/minimum value is 2.2 or less among La La La La La wherein a surface apex is defined as one of intersecting points formed between the optical axis and an approximately spherical surface, which one is closest to a reflection point of the light, the approximately spherical surface having a center that is defined as a center of curvature of the first to the fourth reflective surface, and a radius that is defined as a radius of curvature of the first to the first to the fourth reflective surface, a value of maximum value/minimum value is 2.0 or less among Lb