| 摘要 |
PURPOSE:To make it possible to detect relative positional errors between objects with a high precision by dividing light in a range from ultra violet to infrared into multiple channels to allow it pass through a prism with time differences and then pick up the image of an object for the correction of misalignment. CONSTITUTION:To a prism 22 with half mirrors 24 and 25 mounted on its first inclination and a second inclination provided in parallel thereto, ultraviolet light is caused to enter through a cold mirror 21. There are arranged a first object 30 which emits fluorescent when exposed to this ultraviolet light, and a second object 27 above the prism 22. Then, from the rear side thereof, infrared light is made incident on the prism 22. The optical images of the objects 30 and 27 are picked up by image pick up means 31 with time differences thereby to operate the image output signals. In accordance with the electric signal corresponding to the difference between the objects 30 and 27, the object 27 is shifted with respect to the object 30 for alignment. Thus, it becomes possible to detect the relative positional errors with a high precision. |
