| 摘要 |
PROBLEM TO BE SOLVED: To prevent light transmission foreign matter, having a large area, from being recognized wrongly to be a foreign matter higher than a predetermined height. SOLUTION: A projection system of an optical system 10 irradiates a surface of a glass substrate 1 with a band-like inspection light at an incoming angle of about 20°. A first light-receiving system of the optical system 10 receives scattered light formed, by scattering the inspection light with a foreign matter on a surface of the glass substrate 1 substantially vertically, with respect to the inspection light. The second light-receiving system of the optical system 10 receives reflected light formed by reflecting the inspection light with the surface of the glass substrate 1, at a reflection angle with respect to the incident angle of the inspection light. Regarding foreign matter that makes light transmitted, when the inspection light transmitted into the foreign matter is radiated at a position shifted largely from the incoming position of the inspection light, the first light-receiving system receives light at an angle closer to the horizontal angle than the conventional art, and hence the focus is not achieved at a light irradiated position and emitted light is hardly received. COPYRIGHT: (C)2006,JPO&NCIPI
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