| 摘要 |
PURPOSE:To optionally set a detection area by providing a means which corrects the counted value of an area where a light beam can be scanned into an effective scanning area counted value to a surface inspecting device which scans the light beam on a plate to be inspected to detect a defect. CONSTITUTION:The laser beam projected from a laser tube 11 is scanned by the plate 15 to be inspected by an electromagnetic diaphragm 13 and a plane mirror 14 and it diffracted light is guided to a photoelectron multiplier tube 17 through an optical fiber 16 to detect the defect from variation in the quantity of the diffracted light. At this time, an area conversion data table 1 stored with clock data corresponding to the dead zone area of the plate 15 to be inspected in the area where the light beam can be scanned is provided and a computer 19 performs arithmetic operation for correcting the counted value corresponding to the light beam scanning area into the effective scanning area counted value while referring to the table 1. Consequently, signal processing for the dead zone area need not be performed, so the reliability of defect detection can be improved.
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