| 摘要 |
<P>PROBLEM TO BE SOLVED: To provide superior image forming characteristics of an optical system that is highly reliable for a long period by preventing a contaminant from entering an inner portion of an optical element without performing maintenance on the optical system in an optical element unit used for an immersion exposure process. <P>SOLUTION: The optical element unit includes an optical element group, a housing 3.1 which houses the optical element group and has a housing inner portion and an exit end 3.2, and a purge unit which is connected to an inner housing and supplies a purge medium 15.2 to the housing inner portion. The optical element group includes an extreme optical element 9, which is arranged at the exit end of the housing to isolate the housing inner portion from an environment outside the housing. The extreme optical element and housing are formed so that a sealing gap 12 can be adjusted. The purge unit supplies the purge medium to the sealing gap so as to prevent a contaminant from entering the housing inner portion. <P>COPYRIGHT: (C)2011,JPO&INPIT |
