| CPC G01N 21/892 (2013.01) [G01N 21/8901 (2013.01); G01N 2021/8854 (2013.01)] | 14 Claims |

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1. A surface inspection device comprising:
two or more oblique line light sources configured to emit oblique illumination light beams onto a same inspection target region of steel material;
one or more line sensors configured to receive each of reflected light beams of the oblique illumination light beams from the respective oblique line light sources, the reflected light beams being from the inspection target region for each oblique line light source, and to capture images; and
a detector configured to detect a linear surface defect at the inspection target region using the images captured by the one or more line sensors, wherein
orthographic projections of at least two oblique illumination light beams, out of the oblique illumination light beams from the two or more oblique line light sources, onto a surface of the steel material are orthogonal to each other on the inspection target region, and
the two or more oblique line light sources are configured to emit the oblique illumination light beams in a direction oblique to a transport direction of the steel material.
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