| 摘要 |
<p>PURPOSE:To exchange an X-ray mask at an adequate timing, by detecting the contamination degree of the X-ray mask, on the basis of the amount of light passing through the X-ray mask. CONSTITUTION:The visible light which has entered objectives 24, 25 is relayed by a relay lens 26, and is supplied to a light sensor 17, which generates electric signal proportional to the intensity of the received visible light, and supplies the signal to a signal processing equipment 28 via a conductor wire 27. The signal processing equipment 28 compares the supplied electric signal with an electric signal whose level is corresponding to the state that an X-ray mask 13 is not contaminated, and judges the contamination degree of the X-ray mask 13, on the basis of the comparison results. When the contamination degree exceeds a limit, the X-ray mask 13 is exchanged. Thereby the X-ray mask 13 can be exchanged at an adequate timing.</p> |
