基于计算全息的衍射光学元件印模制备方法研究

介绍了一种基于计算全息的非对称多台阶衍射光学元件印模制备方法,研究了相位型计算全息的工作原理和设计方法,建立了相应的光学系统和衍射光波模型,设计了求取相位型印模微结构的算法流程。在理论分析的基础上,以叠心图案为例,利用MATLAB分别仿真了2台阶、4台阶、8台阶、16台阶衍射光学元件的相位信息以及表面微结构形貌,并对比了其再现图像的质量,发现台阶数越多,再现图像的质量越好。获得印模空间高度数据以及表面结构分布后,利用单点金刚石车削技术,采用快刀加工方式,分别加工了元件尺寸为6 mm×6 mm,最小特征尺寸为30 um的2台阶和4台阶印模,并获得了实际加工的台阶轮廓曲线以及表面结构轮廓。最后采用紫外固化纳米压印技术实现了4台阶印模的复制过程,并对复制样品进行了图像再现,结果表明该方法能用于非对称低台阶数衍射光学元件印模的制备。

Research on preparation method of mold of diffractive optical element based on computer generated holography

The preparation method of mold based on computer generated holography(CGH) of asymmetric multi-step diffractive optical element was introduced, the working principle and design method of phase-type CGH were studied, the corresponding optical system and the diffracted light wave model were established and the algorithm flow chart for obtaining phase-type mold microstructure was designed. Taking a folded heart pattern as an example, the phase information and surface microstructure morphology of 2-step, 4-step, 8-step and 16-step diffractive optical element were simulated by MATLAB, and the quality of the reconstructed image was compared on the basis of theoretical analysis. It is found that the more the number of steps is, the better the quality of the reproduced images will be. After obtaining the height data of the die space and the distribution of the surface structure, the 2-step and 4-step molds with the 6 mm×6 mm element size and the smallest characteristic size 30 um were respectively obtained by the fast knife processing method and the single-point diamond turning technology, and the step contour curve and surface structure contour of actual processing were obtained. Finally, the ultraviolet(UV)-curing nanoimprint technology was used to realize the replication process of the 4-step mold, and the image of replicated samples were produced. The results show that the method can be used for the mold preparation of asymmetric low-step diffractive optical elements.