3D Laser Marking Method On Free-form Surface Based On Texture Mapping

Three dimensional laser marking technology is one of the applications of laser. It can quickly print complex, clear and beautiful graphic in 3D free surface. At the same time, due to the laser marking has the characteristics of no contact, no cutting force and small thermal impact, so the use of three-dimensional laser marking machine for processing, the workpiece will not deform and produce internal stress. In addition, with the development of industrial technology and market demand, more and more products are designed to streamline surface. So as to promote the application of 3D laser marking technology. Three dimensional laser marking technology is faced with the problem of how to generate patterns in 3D free form surfaces. A 3D laser marking method is proposed which can be applied to the surface of triangular mesh. Therefore, all the surfaces or entities in the paper are approximated by triangular meshes, and the mesh surface model is used to parse the STL(Stereolithography) file.Firstly, a texture mapping method based on the principle of projection is adopted. The mapping of texture mapping on 3D surfaces is determined by the projection principle. In this paper, a projection method is proposed, which ensures that the two-dimensional planar pattern can be accurately mapped to the upper surface of surface or cross surfaces. But the texture mapping method based on projection has large deformation when the Gauss curvature of the surface is large. Therefore, the improved projection method is proposed, which is mapping texture onto the deployable surface. And to achieve the mapping of the texture is not deformed. But this method can only be used for the curved surface.Secondly, it is impossible to make the texture mapping onto any undevelopable surfaces without any deformation. In order to solve the problem of reducing the degree of deformation of texture on any surface texture mapping, the method of surface parameterization is chosen. This approach would be to maintain the shape of the triangle unfolding in the plane as far as possible. In order to accurately locate texture position, the paper uses the ABF++(Angle Based Flattening) method. it uses the Newton iterative method, a set of angular values of triangular minimum deformation is obtained when the triangle mesh is expanded on the plane. This method not only maintains its own shape and topological relations, but also has no restrictions on its flattening.Furthermore, when using ABF++ triangulated surface parameters of texture mapping, in order to reduce unnecessary computation, paper use the grid segmentation method and combine the K neighborhood fast searching method for quick navigation to the target, reducing unnecessary computation and improve the texture of the speed of operation. In addition, in order to accurately map the two-dimensional texture mapping onto a surface, the paper combines the principle of projection to determine the position of the plane pattern. At the same time, using the coordinates of the center of gravity method implementation planar pattern linear mapping onto the three-dimensional surface, which avoiding complicated inverse transform calculation and increasing the speed of operation. And analyzing the degree of deformation of the texture, which is mapped onto surface by using the ABF.Finally, the paper takes VS2010 as the platform, and uses C# and C++ programming language and combined with the OpenGL library to build the three-dimensional display environment and to achieve the above algorithm. And the three dimensional model is used to simulate the feasibility of texture mapping algorithm. In addition, the optical path structure of the 3D laser marking system is used to verify the effectiveness of the laser marking machine marking on the surface which is reconstructed by triangular mesh. Last, the three-dimensional laser marking experiment is done to realize the marking on the 3D surface, which further proves the feasibility of the method mentioned above.