| 摘要 |
<p>A projection optical system in which OoB irradiation dose on a wafer is reduced while degradation in optical characteristics is suppressed. The projection optical system comprises a first reflecting mirror exhibiting a reflectivity lower than a predetermined value to a second wavelength light different from a predetermined first wavelength light, and a second reflecting mirror exhibiting a reflectivity higher than the predetermined value to the second wavelength light. When the reflecting mirrors in the projection optical system is classified as reflecting mirrors (M1, M2, M5, M6) having a high ratio of overlapped reflection regions corresponding to two different points on the wafer, and reflecting mirrors (M3, M4) having a low ratio of overlapped reflection regions the uppermost stream reflecting mirror (M3) in the optical path of the projection optical system out of reflecting mirrors having a low ration of overlapped reflection regions is the second reflecting mirror.</p> |
