| 摘要 |
PURPOSE:To prevent the exposure of a substrate by an external leakage light by a method wherein a light-shielding plate is shifted, and the driving of the light- shielding plate is stopped at the position where an opaque pattern is detected. CONSTITUTION:The distance to the optical axis of the light-shielding plate 21 can be adjusted using a driving device 22, a photo sensor 23 is shifted simultaneously with the light-shielding plate 21 and optically detects the opaque pattern to be used for light-shielding. A reticle 2 has a chromium thin film adhered on a glass substrate, and an opaque pattern for light shielding can be optically detected from the back side of the reticle. The light-shielding plate 21 is moved in the direction which is approaching to the luminous source from the position away from the optical axis using the driving device, and the driving device 22 is stopped at the point where an opaque pattern 11 for light-shielding is detected by the photo sensor 23. Accordingly, if the distance of the light-shielding plate 21 and the photo sensor 23 from the optical axis is set, the light-shielding plate 21 can be automatically set at an appropriate position, even when the size 10 of brightness image is changed by the exchange of the reticle 2. |
