| 摘要 |
This device is provided with an elliptical mirror 2, a light source 5 that radiates coherent light towards an inspected edge 4 arranged near the location of its first focal point, a light blocking member 6 that blocks diffracted light of a low order that is radiated from light source 5 and reflected by inspected edge 4, and a photo detector arranged at the location of a second focal point 7 of the elliptical mirror 2. The light blocking member 6 is composed of a light absorbing member arranged on the mirrored surface of elliptical mirror 2 reached by the low order diffracted right.
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