| 摘要 |
PURPOSE:To allow the detection of the dust sticking particularly to the inside surface of a pellicle film by scanning and irradiating the pellicle film with a laser beam to reflect the beam, detecting the irregular reflected beam of the laser beam and decting the foreign matter sticking to the pellicle film and the surface of the film stuck therewith. CONSTITUTION:The laser beam L cast from a laser beam source 4 is scanned. The laser beam L reflects irregularly when the laser beam falls onto the dust D1 sticking to the inside surface of the pellicle film 2. This irregularly reflected beam R is condensed by a condenser lens 5 and a photodetector 6 detects this beam. Decision is then made that the inside surface of the pellicle film 2 has the dust D1. A disposition such as washing is made. On the other hand, the dust D2 existing on the outside surface of the pellicle film 2 reflects irrelevantly and the beam does not reflect irregularly if the inside surface is scanned in such a manner and, therefore, the surface stuck with the dust D2 is judged. The dust sticking to the pellicle film and more particularly the inside surface thereof is detected in this way. |
