New algorithm of shape from shading for cold rolling steel surface defect

Abstract:

To improve the classification performance of cold rolling steel surface defect, a 3D reconstruction algorithm of surface defect is proposed based on shape from shading theory. A modified Oren-Nayar diffuse re- flection model is presented according to the design of optical path for surface defect detection system, then cor- responding reflection map equation is deduced with perspective projection model. The equation is solved by fast sweeping method based on high-order Lax-Friedrichs Hamilton function and Newton iteration, and finally the extraction of surface defect 3D information is realized. The 3D reconstruction experiments with synthetic image and surface defect image are carried out, and the results show that the reconstruction precision is high, the accuracy of modified illumination model is confirmed. The 3D information of cold rolling steel surface de- fect could be extracted effectively by this algorithm, which is helpful for improving the classification perform- ance of surface defect