| 摘要 |
PURPOSE:To directly discriminate a classification of a defect by receiving the scattered light caused by an internal defect, which is brought to internal reflection by the inside of a glass disk and outputted from the side face, in the vicinity opposed to the side face of the periphery of the glass disk. CONSTITUTION:A laser beam T is focused by a projection lens 2, and projected vertically to a glass disk 1. In such a case, since thickness (1-2mm) of the disk 1 is thin, in order to receive efficiently the scattered light, an optical fiber 6 whose diameter is roughly equal to its thickness is used for a light receiving device, and its tip is brought close to a side face 1a. In such a case, an interval (d) of the approach is made as narrow as possible within a range in which the disk 1 is allowed to rotate. In such a way, only the scattered light from the side face is inputted to the fiber 6, and it is evaded that the scattered light of a foreign matter defect from external force of the side face is inputted and S/N related to a defect classification is deteriorated. Also, to a terminal of the fiber 6, a photoelectric converter 7 having satisfactory sensitivity is connected, and a detecting signal to an internal defect and a detecting signal to a foreign matter defect from a light receiving device 4b are discriminated and outputted, respectively by the converter 7. |
