| 摘要 |
PURPOSE:To detect an inclination angle of a surface of a detection object accurately without being affected by reflection light from a rear of the detection object when the detection object transmits light. CONSTITUTION:A horizontal position detection system for leveling is constituted of an irradiation optical system 14 with a first light screening board 18, a conversing optical system 22 with a second light screening board 25 and a photosensitive element 28. A focus position detecting system is constituted of light source 29 to a photosensitive element 35. After a surface 1a of a glass plate 1 is lowered to a lowermost position, it is raised gradually and a detection region of the surface 1a is aligned to a best image forming surface of a projection optical system 8 by using an in-focus position detecting system. Thereafter, an inclination angle of the surface 1a is detected by a horizontal position detecting system. |
