To obtain an inspection apparatus by which a patternlike flaw or an uneven flaw on a surface is detected continuously in an on-line manner and by which the degree of an abnormality can be judged precisely by a method wherein a flaw feature amount is computed from a computed ellipsometric parameter and the polarity of a surface reflection intensity.
Linear cameras 10a to 10c detect optical intensities I1 to I3 from polarized light reflected on the surface (the face to be inspected) of a steel plate. On the basis of their image signals, a parameter computing part 16 computes ellipsometric parameters (an amplitude reflectance ratio tanΨ and cosΔ indicating a phase difference Δ) and a surface reflection intensity I0 so as to be stored 17a to 17c respectively as image data. Images are corrected 19 regarding a luminance irregularity, binarized 20 and ORed 22 so as to be stored in a binarization memory 23. A flaw-candidate-area extraction part 24 specifies the position of a flaw candidate area on the basis of the density of every pixel in the binarized images which are stored 23. The tanΨ, the cosΔ and the I0 in the region are extracted by a feature-amount computing part 25, a peak value or a mean value is computed, and a feature amount is clarified. The degree of an abnormality is judged 26 on the basis of a polarity indicating whether the value is in a + region or a - region from a normal part.
MATOBA YUJI
KAZAMA AKIRA
OSHIGE TAKAHIKO
