| 摘要 |
PURPOSE:To enable detecting a focal position on a projection optical system with higher accuracy. CONSTITUTION:Provided are an aperture pattern formed in a pattern plate 4 adjacent to a wafer W; an illumination optical system 5, and 8 to 10 for detection for guiding illumination light EL to the aperture pattern; a photoelectric sensor which produces focal signals corresponding to the quantity of light. The quantity of light is obtained by limiting, through the aperture pattern, the image thereof which is formed on a mask pattern PA forming face under the illumination light EL through a projection optical system PL and then returned through the projection optical system PL; and zoom lenses 18 and 19 which freely sets sigma value of the illumination optical system 5b and 8 to 10 for detection for the illumination light EL. |
