基于光波导的扩展眼盒全息近眼显示系统  

Holographic Near-Eye Display System with Expanded Eyebox Based on Waveguide

作　　者：于超 孟翔宇 江丽 蔡宏[1] 毛慧[1] 王锐 浦世亮[1] Yu Chao;Meng Xiangyu;Jiang Li;Cai Hong;Mao Hui;Wang Rui;Pu Shiliang(Hikvision Research Institute,Hangzhou Hikvision Digital Technology Co.Ltd.,Hangzhou 310051,Zhejiang,China;College of Computer Science and Technology,Zhejiang University,Hangzhou 310058,Zhejiang,China)

机构地区：[1]杭州海康威视数字技术股份有限公司海康威视研究院,浙江杭州310051 [2]浙江大学计算机科学与技术学院,浙江杭州310058

出　　处：《光学学报》2023年第9期54-65,共12页Acta Optica Sinica

基　　金：浙江省博士后科研项目择优资助(zj2019052)。

摘　　要：全息近眼显示系统受到空间光调制器(SLM)空间带宽积的限制,光学扩展量一般较小,在保持适当视场(FOV)时容易出现眼盒较小的情况,使得用户观察到的图像容易出现缺失。基于二维表面浮雕光栅(SRG)和光波导的扩瞳作用,在适当FOV下,实现了眼盒的二维连续扩展。基于随机梯度下降算法,利用计算全息显示系统生成目标图像,利用目镜将之准直,再利用耦入光栅将其耦合进光波导内。利用光线在光波导内传播时遇到耦出光栅后部分光会被耦合出射、部分光继续传播的特性,系统在两个维度上对光束宽度进行了拓展,实现了扩展的眼盒。该系统与RGB彩色激光照明和SLM时分复用结合时可以实现彩色显示。实验证实,该方案实现了在38.6°FOV和20 mm的出瞳距下,大小为8 mm×6 mm的扩展眼盒,可有效解决用户观察到的图像易缺失的问题。Objective Holographic near-eye displays(NEDs)have attracted ever-increasing attention in recent years.Through wavefront modulation of the incident beam by the spatial light modulator(SLM),a holographic NED can achieve multiple functions that are not within the reach of conventional two-dimensional(2D)displays,such as controlling the depth of the displayed image and dynamically correcting the aberration.However,due to the limited space-bandwidth product of the SLM,the etendue of the entire system is small,leading to a long-standing trade-off between the field of view(FOV)and the eyebox.For example,Microsoft reported at the SIGGRAPH conference in 2017 that they had achieved a FOV of 80°,but the eyebox was small.Two main types of methods have been proposed to expand the eyebox,i.e.,active methods and passive methods.The active methods utilize a pupil-tracking system and move the eyebox subject to the position of the user's eye.Their energy efficiency can be high,contributing to lower power consumption of the system,longer battery life,and simpler thermal design.However,the main challenge for achieving high immersion in augmented reality(AR)use cases is low motion-to-photon latency,which is more difficult to obtain when the process of eye-tracking is incorporated.The passive solutions generally provide multiple discrete eyebox points simultaneously to expand the entire eyebox.However,they are exposed to the risk that no or two eyebox points may enter the pupil at a certain position as the user's eye moves.In such a case,missing of fields,low brightness uniformity,or ghost artifact occurs.In this paper,a holographic NED system with an expanded eyebox based on a surface relief grating(SRG)waveguide is investigated,showcasing a continuously and two-dimensionally expanded eyebox.Methods In the calculation of holograms,the angular spectrum method(ASM)and the stochastic gradient descent(SGD)algorithm are adopted because they can provide much better image quality than that offered by the traditional Gerchberg-Saxton(GS)alg

关 键 词：全息 计算全息 近眼显示 光波导 扩展眼盒 光瞳扩展 

分 类 号：O438.1[机械工程—光学工程]