增强现实头盔显示器(HMD)需要两个或更多焦平面,用以显示不同焦距上的画面,既能增强景深效果又能减少单焦面带来的视觉辐辏冲突及不适感。较为传统的解决办法是使用两块分离的图像生成单元(PGU)分别显示两个焦面的内容,增加了成本,降低了可靠性并且体积庞大。使用单个图像生成单元和单个自由曲面棱镜设计了一个新的结构,在图像生成单元上设置两个分开的区域,并通过平面反射镜将其中一个图像区域中继到新的较远位置以实现双焦面显示,最终得到一个视场角为18°×16°,出瞳直径为8 mm,波长为540~640 nm,出瞳距大于15 mm,焦距为95.2 mm和35.2 mm的双焦面头盔显示光学系统。

Augmented reality helmet mounted display (HMD) requires two or more focal planes to display pictures at different focal lengths, which not only enhances the depth of field effect, but also reduces the visual conflict and discomfort caused by a single focal plane. A relatively traditional solution is to use two separate picture generation units (PGUs). However, it increases the cost, reduces the reliability, and is bulky. We design a new structure using a single PGU and a single free-form surface prism. By setting two separate areas on the PGU and making one of the image areas relayed to the new remote position through two flat mirrors, we achieve a bifocal surface display. Finally, a HMD optical system is designed, which possesses a field-of-view angle of 18°×16°, an exit pupil diameter of 8 mm, a working wavelength of 540--640 nm, an exit pupil distance greater than 15 mm, and two focal lengths of 95.2 mm and 35.2 mm.