全息波导显示系统中输出光栅的衍射效率、位置和长度对整个显示系统的光强输出均匀性及能量利用率有重要的影响.通常输出光强均匀性由输出光栅的衍射效率决定, 能量利用率受多重光栅的位置和长度影响.本文以中心视场光束的输出光强均匀为目的, 对相应输出光栅衍射效率的位置分布进行优化与曲线拟合, 得到输出光栅衍射效率随输出位置连续递增的分布曲线, 并应用到所有视场光束.计算结果表明, 相比于传统阶梯状衍射效率分布输出光栅, 全息波导显示系统中采用具有连续衍射效率分布输出光栅时的光强输出均匀性得到明显提升.针对部分衍射光束未能进入出瞳的现象, 提出错位优化法, 按照出瞳大小和使用距离优化各重输出光栅的位置和尺寸, 减小了光栅的无效衍射区域, 提高了出瞳范围内的能量利用率.

In a holographic waveguide display system, the diffraction efficiency, location, and length of each ouput grating make great impact on the uniformity of output intensity and ratio of energy utilization. Generally uniformity of output intensity is decided by the diffraction efficiency distribution of each output grating, and ratio of energy utilization rests with the location and length of each ouput grating. Firstly, aming at the uniformity of central field of view, the diffraction efficiency distribution of corresponding output grating was optimized and curve fitting, and a continuous and increasing curve of efficiency distribution was obtained. Similar processing was carried out for other gratings corresponding to other FOV. Calculation results demonstrate that the uniformity of output intensity of HWDS will be improved notablely when output gratings with optimized continuous and increasing diffraction efficiency distributions are used than that of traditional output gratings with step diffraction efficiency distributions. A shifting-optimization method was proposed to optimize the location of each grating according to the size of exit pupil and usage distance, so that the ratio of energy utilization of HWDS could be greatly incereased resulted from the reduction of the invalid diffraction region.