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为确定卷积效应以及深度制作误差对小F数连续浮雕衍射透镜(DOE)轴向聚焦特性影响,基于瑞利-索末菲衍射理论建立了激光直写制作的连续浮雕衍射透镜非旁轴近似轴向光强分布模型。该模型考虑了连续浮雕衍射透镜的轴向衍射聚焦特性与透镜结构参数、写入光斑尺寸和扫描间距以及深度制作误差的关系,克服了傍轴近似条件下传统模型的不精确性。为验证模型的正确性,用激光直写制作了设计波长为441.6 nm,F数为4以及相位匹配因子为3的连续浮雕衍射透镜,并测试了波长441.6 nm激光入射时透镜的轴向聚焦特性。实验与分析表明,该模型分析结果与实验测试结果符合,从而证实模型的有效性,为激光直写制作的小F数连续浮雕衍射透镜的应用提供了理论依据。
In order to determine the influence of convolution effect and depth error on the axial focusing characteristics of a small F-number continuous relief diffractive lens (DOE), a non-paraxial approximation of continuous relief diffractive lens fabricated by laser direct writing was established based on the Rayleigh-Sommerfeld diffraction theory Axial light intensity distribution model. The model takes into account the relationship between the axial diffraction focusing characteristics of the continuous relief diffraction lens and the lens structure parameters, the write spot size and the scanning pitch and the depth production error, and overcomes the inaccuracy of the traditional model under the paraxial approximation. In order to verify the correctness of the model, a continuous relief diffraction lens with a designed wavelength of 441.6 nm, an F number of 4 and a phase matching factor of 3 was prepared by laser direct writing. The axial focusing characteristics of the lens at a wavelength of 441.6 nm . Experiments and analysis show that the results of the model are in good agreement with the experimental results to verify the validity of the model and provide a theoretical basis for the application of small F-number continuous relief diffraction lens made by laser direct writing.