The Key Technology Research Of Laser Transmission Micro Welding Based On Diffractive Optical Element

More and more people are highlighting laser transmission micro welding of thermoplastics because of the increasing desire to high quality micro welding of plastics in micro fields such as Micro Electro-Mechanical Systems and Micro-flow devices.Recently, the research of laser transmission micro welding of thermoplastics has been developed in overseas,however,there is few domestic study on this research subject.Therefore, research on laser transmission simultaneous micro welding of thermoplastics has a significant meaning.Recently,the welding methods of the research almost are masking welding and scanning welding in overseas,a new technology of laser transmission simultaneous micro welding of thermoplastics based on diffractive optical element is researched in this dissertation.First of all,the principle of the laser transmission micro welding of thermoplastics is introduced,and based on that,the laser transmission micro welding method of thermoplastics based on DOE is researched.The optical path system of the laser transmission micro welding is established.The laser、plastic materials、welding absorbent of process system、welding fixture and welding process monitoring are studied.Secondly,the dissertation gives a detailed analysis of the basic design theory of diffractive optical element and a main research on the scalar diffraction theory.The optimization design algorithm of diffractive optical element based on the scalar diffraction theory is introduced.In succession,the type of diffraction of the welding system is determined,and the diffractive model is established;The traditional GS algorithm is modified and improved; The DOE is designed by using the modified GS algorithm,square is selected as target image to simulate and calculate.The weighted factor is determined during the simulating and calculating.The results indicate that introducing the weighted factor can get higher diffractive efficiency and smaller Sum of Square Error;The target image is encoded,the influences to the calculation results when adding amplitude freedom and phase freedom to the target image are analyzed.The results indicate that adding appropriate amplitude freedom and phase freedom to the target image simultaneously can improve the diffraction effect;The DOE is designed when the target image is complex,the results are good;The results from the procedure and the commercial software are compared,which prove the correctness of the procedure.At the end of dissertation,the DOE is designed and fabricated to the Nd:YAG laser. The diffraction experiment results indicate that the shape of laser beam spot after diffraction is almost as same as the shape of target image.The research of this dissertation lays a solid foundation of research on laser transmission micro welding of thermoplastics based on diffractive optical element.