| 摘要 |
A description is given of an optical inspection device for inspecting two oppositely located surfaces (3, 4) of a transparent object (1), for example a lithographic mask. The device is constructed in such a manner that for each inspection beam (a, c) the radiation path to the surface to be inspected (3, 4) is substantially equal to the radiation path from the surface to be inspected to a detector (29, 40), so that these paths comprise the same scanning element (10), preferably a mirror polygon. By virtue thereof, the radiation spots formed on the detectors are stationary and an inspection signal having a good signal-to-noise ratio is obtained.
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