微透镜阵列出瞳扩展全色激光扫描显示方法研究

Retinal Scanning Display (RSD) as a revolutionary technology has been used in hand-held or head-worn devices, as it has many advantages, such as small volume, low power consumption, high resolution, large color gamut, and high brightness. However, the exit pupil of laser scanning display is only a few mm, which is limited by the factor αD of MEMS mirror. These make RSD difficult to be applied in helmet-mounted display. In this proposal, we try to present a new method to expand the exit pupil by using the Dual Micro-Lens Arrays (DMLA) as diffraction optical element. The method can overcome the dependence on wavelength. In order to analyze the optical field distribution from DMLA and RSD, the physical model is established, which is based on Fresnel diffraction integral and Fourier transform principles. Many problems in fabrication process of micro-lens arrays with high filling ratio, high uniformity will be solved. The measurement setup will be designed to align and bond two identical micro-lens arrays. Finally, full-color RSD with DMLA will be optimized to satisfy the requirement of helmet-mount display, such as large exit pupil, full-color and high brightness uniform. All the done in this project will provide theoretical basis for the development and application of full-color RSD with DMLA.

激光为光源的视网膜扫描显示具有小体积、低功耗、高分辨率、大色域、高亮度等优点，成为头盔显示中一项最新且具有革命性的技术，但是，由于受到MEMS振镜转角和尺寸乘积的限制，出瞳仅有几个毫米，难以应用到头盔显示中。本项目拟采用微透镜阵列衍射光学元件扩展激光扫描显示的出瞳，实现全色、大出瞳显示，克服普通出瞳扩展光学元件对波长的强烈依赖性。为此，利用菲涅耳衍射积分和傅里叶变换方法，建立双微透镜阵列和视网膜扫描显示的光束传输物理模型、出瞳光场分布计算模型，探讨影响双微透镜阵列输出光强分布及视网膜扫描显示出瞳大小的因素，解决高填充比、高均匀性微透镜阵列制备技术问题，建立高精度双微透镜阵列对准检测系统。实现基于微透镜阵列的全色激光扫描显示，满足头盔显示大出瞳、全色、高亮度均匀性等要求，为激光扫描显示（头盔显示的图像源）的发展和应用提供理论基础。

针对MEMS微反射镜扫描激光显示系统，受到MEMS微反射镜机械转角和尺寸乘积的限制，出瞳仅有几个毫米，难以满足头盔显示的需求。本项目重点是通过研制了间隙金属填充型微透镜阵列作来有效地解决了上述问题。在项目实施中，申请人及团队成员建立了有效分析经微透镜阵列传输后光强分布的理论模型，分析计算不同孔径、不同波长、不同入射角下单个和双微透镜阵列输出的光强分布。计算结果表明，要在直径为15mm的出瞳范围内获取均匀的光强分布，要求微透镜阵列的NA为0.25，单个微透镜通光孔径为8μm。单个微透镜阵列和双微透镜阵列实现的光强均匀性分别为73%和82%。利用热熔法和AZ5214光刻胶，通过两步光刻套刻工艺和对准误差的有效矫正完成了间隙填充金属型微透镜阵列的制作。通过优化光刻胶的深宽比，有效地克服了微透镜之间粘连和微透镜顶部的凹陷。实现了面形均匀光滑、间隙完全填充金属、填充因子为70%、成品率达90%的微透镜阵列。根据头盔显示的分辨率要求，优化设计了带矫正透镜的激光扫描显示系统，可在对角线为0.77英寸的显示屏上，实现1280×960分辨率的图像显示。利用研制的0.8μm间隙填充金属和有效焦距约为19μm的微透镜阵列作为出瞳扩展元件，实现了亮度均匀、清晰的彩色图像显示。通过本项目的实施，一方面研制了一种间隙填充型微透镜阵列，有效解决了MEMS微反射镜扫描激光微显示系统出瞳小的问题，推动了激光扫描显示在头盔显示、近眼显示中的应用；另一方面，微透镜阵列具有的光束整形、扩束和成像等功能，可在光通讯和光计算中发挥重要的作用。