| 主权项 |
1. An apparatus for detecting periodic defects comprising:
a sensor that obtains signals to evaluate properties of an area having a length longer than an expected defect period on a target sample; a small area selector that separates a plurality of small areas, wherein a length of each small area is shorter than the length of the area and the length of each small area is between the range of ¼ or more and twice or less than the maximum length of an expected defect, 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 calculator that calculates a similarity evaluation index between signal patterns among a plurality of signals selected by the small area selector; a set value changer that changes the positions of the small areas and the distance interval, and repeating computational processings of the small area selector and the evaluation index calculator; a period judgment device that judges the distance interval as a period when the evaluation index is higher than a value set beforehand; and a defect judgment means that judges the existence of a periodic defect in the small area on the basis of signals in the small area in which the periodicity judging is conducted, wherein the small area selector comprises: a first small area selector that determines one position of a small area whose length is shorter than the length of the area to define the small area as a first small area, and selecting a signal corresponding to the position of the first small area from the sensor output; and a second small area selector that disposes a plurality of second small areas having the same size as the first small area in a periodic defect arrangement direction on the basis of the position of the first small area while separating the second small areas so that all distance intervals are equal, and selecting signals corresponding to positions of the plurality of second small areas from the sensor output, and the set value changer changes the position of the first small area and the distance interval, and repeats computational processings of the small area selector and the evaluation index calculator; and wherein the sensor is a magnetic sensor that magnetizes a target sample formed of a magnetic metal component, and obtains a leakage flux signal. |
