均匀照明用衍射光学器件的空间频域优化设计方法

为改善衍射光学器件(DOE)在均匀照明系统中的应用性能,提高元件优化设计的效率,提出了衍射光学器件的空间频域优化设计方法。基于对均匀照明系统焦面输出光强分布的空间频谱分析,从空间频域的角度,指出通过控制焦斑中的低频调制成分,能够进一步提高实际均匀照明的效果。在此基础上,该优化方法通过在频域内设定优化目标和费用函数,来确定优化方向,可以有效减少输出光强分布中的低频调制成分。应用该方法所得一维多台阶相位型衍射光学器件的设计结果表明,在考虑空间20μm匀滑后,焦斑主瓣光强均方差为3.3%。与已有空间域优化方法的对比表明,在元件实用效果方面,空间频域优化设计方法优于空域方法。

Spatial Frequency Spectrum Optimization Method for Design of Diffractive Optical Elements in Uniform Illumination

A spatial spectrum optimization method for the design of diffractive optical elements (DOE) used in uniform illumination, is presented to improve the design results and optimize efficiency. The spatial frequency spectrum of intensity distribution on the focal plane is analyzed, which shows that the uniformity can be further improved by controlling the low frequency spatial modulations in the focal spot. So the goal and cost functions of the new method are chosen in spatial spectrum domain to determine the searching path, which can decrease the low frequency modulations. By using the new method, a DOE that has multi-step phase distribution is optimized. The result shows that the root-mean-square error of light intensity of the main lobe of the focal spot is 3.3% with smoothing in 20 μm. Compared with existing spatial domain optimization methods, the new spatial spectrum optimization method can effectively improve the practical performance of DOE and save computing time.