| 摘要 |
PROBLEM TO BE SOLVED: To provide a method and an apparatus for inspecting foreign matters, whereby foreign matters can be detected with a high S/N, while a point sensor is used and illumination of a realizable spot diameter is carried out. SOLUTION: According to this inspection method for foreign matters, an illumination light is irradiated on a face 6 to be inspected, and a reflecting light is detected by the point sensor such as a photomultiplier 10 or the like and converted to electrical signals. The foreign matter 8 is determined on the basis of data obtained, by sampling the signals by a predetermined sampling time. The signals from the photomultiplier 10 are sampled by an A/D conversion part 12. A difference between each of the data and preceding or succeeding data is calculated by a difference-calculating part 13. The foreign matter 8 is determined on the basis of the calculated difference value at a signal- processing part 14.
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