A 3D reconstruction method based on grid laser and gray scale photo for visual inspection of welds

摘要

Three-dimensional reconstruction of the weld surface is critical for online visual inspection of welds. A new three-dimensional reconstruction algorithm is proposed by fusion analysis of the images of weld under grid laser illumination and without additional light sources. A grid laser was used to form a 9 x 9 orthogonal beam grid on the weld surface and a single camera was used to make sure the images were captured in the same coordinate system. For every single grid, the height value at the points with grid laser beam was calculated. After that, the height value was combined with the gray value of the image to reconstruct the three-dimensional contour of the weld by nonlinear fitting algorithm. The developed laser-photo hybrid method acquires the 3D information of weld surface by a shot of picture rather than the continuous collecting method used in the line-laser sensor. The designed laser-photo based system can measure welds with satisfied accuracy and reliability, which eliminates errors caused by deflection between measured system and the workpiece.