| 摘要 |
PROBLEM TO BE SOLVED: To inspect on-line a pattern-like flaw on the surface of a sheet-like product such as a steel plate or the like continuously manufactured and conveyed. SOLUTION: Polarized light is forced to enter a steel plate at a fixed angle of incidence, and three kinds of different polarized light of the reflected light are detected by linear array cameras 8a, 8b, 8c to obtain a polarized light image. The polarized image is normalized by a signal processing part 10 that the normal part is central brightness of total gradation and converted into an image signal showing the relative change to the normal part. From the image signal, an ellipsoparameter tanψ, cosΔand reflected light intensity I0 to form a relative value image of tanψ, cosΔand I0 . From the relative value image, the relative changes of tanψ, cosΔand I0 are detected to detect the kind of a flaw on the surface of the steel plate 4.
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