| 摘要 |
PURPOSE:To freely arrange a laser system for exposure use either longitudinally or transversely by a method wherein a reflection mirror to send the alignment light is installed en bloc on the side of a rear mirror of the laser system for exposure use. CONSTITUTION:A reflection mirror 4 is installed en bloc at the back part of a rear mirror 3 of a laser tube 1 in such a way that it is tilted by 45 deg. with reference to the direction of laser radiation. A laser beam, for alignment use, from a laser system 5 for alignment use enters the mirror 3 via the mirror 4 and goes out from a front mirror 2. Accordingly, if the position of the center of gravity of an exposure system is to be lowered, it is possible to constitute the system in such a way that the laser tube 1 is arranged transversely so that the laser beam enters a projection optical system 6 through mirrors 7a-7c. In addition, if it is not possible to obtain a sufficiently large area for installation of the laser system for exposure use, it is possible to constitute the system in such a way that the laser tube 1 is arranged longitudinally so that the laser beam enters the optical system 6 through mirrors 9, 10.
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