Inspection method for directional texture defects on steel strip surface

A variety of defect types exist on steel strip surface, most of which will be seen best in the arrangement that camera and illumination are arranged in one plane and with the same angle on both sides of the orthogonal. But for surface directional texture defects like scratches due to the "turn around" effect for some rays of light meeting the violations. So the camera would not see the illumination in orthogonal direction. This paper presents the multi-sensor and image fusion method in the reasonable arrangement of camera and illumination which are in different angles and at different positions against the strip to obtain the surface defects information exhaustively. The approach will most probably avoid the situation of two types of defects in the same strip only one will become visible. On pixel level, image fusion based on spatial domain and wavelet decomposition is proposed. Test on defect images of inclusion and scratch collected at a different angle, crack and scratch collected in diffuse and directed light respectively. The experiment results show that directional texture defects can be sufficient inspected by the multi-sensor and image fusion method.