用于发散激光光束整形的自由曲面透镜设计

Design of Freeform Surface Lens for Shaping Divergent Laser Beam

提出了一种激光光束整形自由曲面透镜的设计方法,这种方法可以对有一定发散角的激光光束进行整形。设计分为两个过程:1)设计初始结构,以准直激光光束作为输入光束,采用能量网格划分法,设计自由曲面整形透镜,将设计好的透镜作为下一步设计的初始结构;2)逆向反馈优化法,以带有一定发散角的光束作为输入光束,用上一步获得的透镜作为初始结构,采用逆向反馈优化的方法作进一步优化设计。应用这种方法,以束腰为10mm,发散半角为2.5°的发散激光光束为例,将其整形为40mm×40mm的方形光束,辐射照度均匀度达到了90.4%。最后,对设计的透镜进行了加工误差分析和安装误差分析。分析结果表明:透镜表面面形误差在±5μm范围内对目标平面辐射照度的均匀度几乎没有影响;透镜安装时,纵向位移误差dz对目标平面辐射照度的均匀度影响较小,横向误差dx、倾斜角误差dφ对辐射照度均匀度影响较大。

A design method of laser beam shaping freeform surface lens is proposed,which can be applied to shape the diverging laser beam.Freeform surface lens design is a two-step process.Firstly,an initial lens layout is designed by establishing the input-output energy mapping relationship.Then,the reverse feedback optimization method is used to optimize the initial freeform lens when the divergent beam is applied.By this method,a freeform lens is designed for shaping a laser beam with beam waist of 10 mm and a half divergence angle of 2.5°.The simulation results show that the freeform lens can transform a Gaussian beam into a 40mm×40mm top-hat beam with an irradiance uniformity of 90.4%.Finally,the machining error analysis and the assembly tolerance analysis of the freeform lens are performed.It is shown that the uniformity is almost unchanged while the process error varies from-5μm to 5μm.And the longitudinal deviation error dz has little influence on the irradiance uniformity,but the lateral deviation error dxand slant angle error dφhave a significant influence on the irradiance uniformity.