| 摘要 |
<p>PROBLEM TO BE SOLVED: To prevent members around a reflection mirror from being damaged in the case where the reflection coating of the mirror is incapable of sufficient reflection. SOLUTION: Provided so as to open/close freely in a laser optical path is a reflection mirror 31 which shields the laser optical path by reflecting a laser beam with a reflection coating Rc provided on the surface of a base material 37 that transmits a laser beam LB. A light shielding plate 39 is arranged behind the reflection mirror 31, operating synchronously with the opening/closing operation of the reflection mirror 31, shielding and absorbing a laser beam transmitted through the reflection mirror 31. In the case where the reflection coating of the mirror 31 no longer reflects sufficiently, the laser beam transmitted through the base material 37 of the mirror 31 is absorbed in the light shielding plate 39 and heated; however, even if the plate 39 is bent due to the heating, the reflection mirror 31 is free from influence, deformation or cracks. A temperature detector 33 gives the alarm when the temperature of the light shielding plate 39 reaches a set temperature Ts or above.</p> |
