| 摘要 |
When determining the presence of foreign particles in a processing chamber by radiating a laser beam inside a processing chamber and detecting scattered light from foreign particles within the processing chamber, the detection of scattered light is performed using a detecting lens having a wide field angle and deep focal depth. Accordingly, the detection of foreign particles floating in the processing chamber can be performed across a wide range, and with uniform sensitivity, with a detecting optical system having a simple constitution.
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