| 摘要 |
An apparatus for detecting periodic defect, has: a sensor 4; a small area selection means (72, 74) for separating a plurality of small areas whose area length is shorter than that of the area so that all distance intervals adjacent to one another are equal in a periodic defect arrangement direction to determine positions of the plurality of small areas, and selecting signals corresponding to the positions of the plurality of small areas from outputs from the sensor; an evaluation index calculation means 76 for calculating a similarity evaluation index between signal patterns among a plurality of signals selected by the small area selection means; a set value changing means (73, 75) for changing the positions of the small areas and the distance interval, and repeating computational processings of the small area selection means and the evaluation index calculation means; and a period judgment means 77 for judging the distance interval as a period when the evaluation index is higher than a value set beforehand. A method for detecting periodic defect has a signal inputting step, a small area selecting step, an evaluation index calculation step, a set value changing step, and a periodicity judging step. |
