Gu Luo, Cheng Dewen, Wang Qiwei, Hou Qichao, Wang Shanshan, Yang Tong, Wang Yongtian
Opt Express. 2019 Apr 29;27(9):12692-12709. doi: 10.1364/OE.27.012692.
Nonuniform illumination is one of the factors in degrading image performance of geometrical waveguide-based head-up display. The two-dimensional (2-D) waveguide expanding the exit pupil along two orthogonal directions makes illumination uniformization more intractable. To solve this problem, the reasons for nonuniform illumination in 2-D geometrical waveguide were probed and a novel waveguide structure incorporating illumination compensator was proposed. A bilayer illumination compensator was first presented to change the period of rays propagating in waveguide to improve the inter-pupil illumination uniformity and inter-field illumination uniformity. Then optimized coating design for different partially reflective mirrors in horizontal waveguide and the vertical one allowed further improvement of these two kinds of illumination uniformity, raising both up to 70%. A matched catadioptric projection optics using freeform surface was designed and integrated with the resultant 2-D geometrical waveguide, achieving a head-up display with an eye relief of 400 mm, an eyebox of 80 mm × 80 mm and a field of 24° × 15°. A prototype of the proposed 2-D geometrical waveguide display was developed and demonstrated.
非均匀照明是降低基于几何波导的平视显示器图像性能的因素之一。沿两个正交方向扩展出射光瞳的二维（2-D）波导使照明均匀化变得更加棘手。为了解决这个问题，探究了二维几何波导中照明不均匀的原因，并提出了一种包含照明补偿器的新型波导结构。首先提出了一种双层照明补偿器，以改变在波导中传播的光线周期，从而提高瞳孔间照明均匀性和场间照明均匀性。然后，对水平波导和垂直波导中不同部分反射镜的涂层设计进行优化，进一步提高了这两种照明均匀性，使其均达到70%。设计了一种使用自由曲面的匹配折反射投影光学系统，并将其与所得的二维几何波导集成在一起，实现了一种出瞳距为400 mm、眼框为80 mm×80 mm且视场为24°×15°的平视显示器。开发并展示了所提出的二维几何波导显示器的原型。
