| 摘要 |
PURPOSE: To restrict the dimensional change in a laser beam so as to reach an aperture member over a long time by installing a reducing member on an oscillator and making the size of the laser beam arrived onto the aperture member smaller than the size of the laser beam just after it is oscillated. CONSTITUTION: For an excimer laser beam 2 emitted from an oscillator 1, an optical path reaching a machining table 8 is prepared with mirrors 3a to 3c. This oscillator 1 has a total reflection mirror 22 having curvature on the reflecting face and a partial transmission mirror 22 not having curvature on the reflecting face. The excimer laser beam 2 emitted from the partial transemission mirror 20 has the tendency of being converged. That is, the irradiation area of the excimer laser beam 2 reaching an aperture member 11 is smaller than the irradiation area of the excimer laser beam 2 just after it is emitted from the partial transmission mirror 20. Therefore, the enlargement of the beam spreading angle can be restricted, so that the excimer laser beam 2 being cut with the aperture member 11 is not almost changed even for a long time of operation. |
