| 摘要 |
PURPOSE:To realize an inspection method which is less affected in inspection accuracy depending on lighting conditions, by a method wherein two parts of the same disc under the same light conditions are monitored with separate cameras to compare images of the two discs and the generation of a defect is determined when non-coincidence of the two is found. CONSTITUTION:In the inspection of discs 1, a strobo emission is performed synchronizing a lighting means to judge the presence of a defect from images obtained with cameras 20 and 21. In this case, a plurality of judging sections a1, a2..., b1, b2... are so set as to continue radially toward the periphery from the center of the respective discs 1 in the images obtained with the cameras 20 and 21. Images positioned symmetrically are compared with a comparative decision circuit 40 separately between the judging sections, for example, a1 and b1. When a defect exists, it appears as white spot in the images. On the other hand, when the images of the judging sections to be compared are uniform, the results of comparison by the circuit 40 do not coincide with each other thereby enabling immediate judgement of a defect being present. |
