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为满足空间成像领域对大口径、轻量化、高衍射效率光学衍射元件的需求,研究了薄膜衍射元件微结构设计及制作工艺。应用Zemax光学软件设计了320 mm口径,F/#100的四台阶薄膜菲涅尔衍射元件,并利用Matlab软件将连续位相结构转化为离散化台阶分布。研究了薄膜菲涅尔衍射元件的制作技术,选用透明聚酰亚胺薄膜作为基底材料,以石英玻璃作为复制模板,通过多次旋涂的方式实现了厚度为20μm的衍射薄膜制作。应用Solidworks软件设计并加工薄膜支撑装置。测量复制基板及薄膜对应区域的微结构,实验结果表明条纹线宽转移偏差小于1.3%,台阶深度偏差小于8.6%。搭建光路测试在波长632.8 nm处衍射效率平均值为71.5%,达到了理论值的88%。实验结果表明,制作的薄膜重量轻,复制精度高,并且具有高衍射效率,满足空间望远镜的应用要求。
In order to meet the demand of large-aperture, lightweight and high-diffraction efficiency optical diffraction elements in the field of space imaging, the microstructure design and fabrication process of the thin-film diffraction element are studied. The four-step thin-film Fresnel diffraction element of 320 mm diameter and F / # 100 was designed with Zemax optical software and the continuous phase structure was transformed into discrete step distribution by Matlab software. The production technology of thin-film Fresnel diffraction element is studied. The transparent polyimide film is selected as the base material and the quartz glass is used as the replica template. The diffraction film with the thickness of 20μm is fabricated by multiple spin-coating. Application Solidworks software design and processing of film support device. The microstructures of the corresponding regions of the replica substrate and the film were measured. The experimental results show that the deviation of the line width of the stripes is less than 1.3% and the step depth deviation is less than 8.6%. The average diffraction efficiency of the constructed optical path at 632.8 nm was 71.5%, reaching 88% of the theoretical value. The experimental results show that the produced film has the characteristics of light weight, high replication precision, high diffraction efficiency and application requirements of the space telescope.