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全息透镜是一种通过全息波前记录制作的成像元件. 由于其形状因子小、波长和角度选择性等优势, 在增强现实(augmented reality, AR)领域有着很好的应用前景. 全色全息透镜的制作与成像过程分析是当前的难点. 通过标量衍射理论推导了离轴全息透镜的共轭成像方程, 分析了现有成像系统中的畸变和像散问题. 此外, 通过 k 矢量圆和光线追迹相结合的几何光学方法模拟了一个视场角为18°, 眼盒为10 mm的AR系统, 通过干涉曝光实验制作了全色全息透镜, 其平均峰值衍射效率为56.7%, 达到国际较高水平. 将激光微投与全息透镜相结合, 搭建了AR系统原型, 得到了系统的畸变和像散效果实验效果, 与模拟的情况相一致. 并测量了系统的MTF参数, 其清晰度基本满足人眼的分辨率需求. 对于单色成像, 提出了添加柱面透镜的方式, 保证子午面和弧矢面的光焦度一致以消除像散; 提出了设计自由形式的波前记录方式以消除畸变. 对于全色成像, 提出了记录过程中预先补偿的方法, 以解决3个颜色通道之间图像不重合的问题.Holographic optical element (HOE) lens is an imaging element fabricated through recording wavefront by interference. Because of its advantages of small form factor and wavelength, angle selectivity and arbitrary wavefront formation, it has a good application prospect in augmented reality display. To make the system more compact, the HOE lens is adopted as an off-axis optical element. At the same time, according to diffraction principle, its wavelength response is more sensitive than those of traditional refractive and reflective optical elements. Thus the fabrication and design of a full-color HOE lens is a challenge to optimizing the free-space head-up display system. To systematically analyze the HOE imaging system, the conjugate relation between the object and image is derived by scalar diffraction theory. Then the Gaussian conjugate imaging equation is obtained and the off-axis aberration of distortion and astigmatism in the HOE imaging system are analyzed. In addition, A head-up display with field of view (FOV) of 18° and eyebox of 10 mm is simulated and its imaging process is visualized through the geometric optics method of k -vector diagram and ray-tracing. A full-color HOE lens with high diffraction efficiency is fabricated by interference. Its average peak diffraction efficiency is 56.7%, reaching a high level in the world. A prototype of augmented reality system is established by integrating laser pico-projectior with HOE lens. The experimental results of distortion effect and astigmatism effect of the system are obtained, which are consistent with the simulation results. The modulation transfer function (MTF) parameter of the system is measured, and its definition basically meets the requirements of the human eyes for resolution. The aberration of the system is analyzed and the optimization method is proposed. To optimize the monochromatic image quality, an extra cylindrical lens is added to ensure the same optical power of meridian and sagittal plane to eliminate the astigmatism. Besides, a freeform wavefront is designed by the geometric construction method and forms a freeform HOE to deal with the distortion problem. The local recording freeform wavefront can be calculated by the imaging equation. When full-color HOE is applied to the display system, the images of three channels may separate in the space because of their different reconstruction wavelengths and angles. We propose a pre-compensation method of recording process to solve this problem. If these above-mentioned problems can be solved, due to its good image uniformity, sufficient field angle and eyebox area, the head-up display based on HOE lens with extra optical power will have a better application in augmented reality technology.
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Keywords:
- holographic optical element /
- laser display /
- near-eye display /
- augmented reality
[1] Xiong J, Hsiang E L, He Z, Zhan T, Wu S T 2021 Light: Sci. Appl. 10 216Google Scholar
[2] Zhan T, Yin K, Xiong J, He Z, Wu S T 2020 iScience 23 101397Google Scholar
[3] 史晓刚, 薛正辉, 李会会, 王丙杰, 李双龙 2021 中国光学 14 1146Google Scholar
Shi X G, Xue Z H, Li H H, Wang B J, Li S L 2021 Chin. Opt. 14 1146Google Scholar
[4] Yu C, Peng Y F, Zhao Q, Li H F, Liu X 2017 Appl. Opt. 56 9390Google Scholar
[5] Han J, Liu J, Yao X C, Wang Y T 2015 Opt. Express 23 3534Google Scholar
[6] 金闻嘉 2020 硕士学位论文 (杭州: 浙江大学)
Jin W J 2020 M S. Dissertation (Hangzhou: Zhejiang University) (in Chinese)
[7] Peng H C, Cheng D W, Han J, Xu C, Song W T, Ha L Z, Yang J, Hu Q X, Wang Y T 2014 Appl. Opt. 53 H177Google Scholar
[8] Li G, Lee D, Jeong Y, Cho J, Lee B 2016 Opt. Lett. 41 2486Google Scholar
[9] Chang C, Bang K, Wetzstein G, Lee B, Gao L 2020 Optica 7 1563Google Scholar
[10] 刘奡 2019 博士学位论文 (南京: 东南大学)
Liu A 2019 Ph. D. Dissertation (Nanjing: Dongnan University) (in Chinese)
[11] 邬融, 孙明营, 周申蕾, 乔战峰, 华能 2020 物理学报 69 234209Google Scholar
Wu R, Sun M Y, Zhou S L, Qiao Z F, Hua N 2020 Acta Phys. Sin. 69 234209Google Scholar
[12] Cheng D W, Wang Y T, Hua H, Talha M M 2009 Appl. Opt. 48 2655Google Scholar
[13] Pulli K 2017 Sid Symposium Digest of Technical Papers 48 132Google Scholar
[14] Li G, Jeong J, Lee D, Yeom J, Jang C, Lee S, Lee B 2015 Opt. Express 23 33170Google Scholar
[15] Jang C G, Mercier O, Bang K, Li G, Zhao Y, Lanman D 2020 ACM Trans. Graph. 39 184Google Scholar
[16] Maimone A, Wang J 2020 ACM Trans. Graph. 39 67Google Scholar
[17] Jang C, Hong K, Yeom J, Lee B 2014 Opt. Express 22 27958Google Scholar
[18] Jang C, Lee C K, Jeong J, Li G, Lee S, Yeom J, Hong K, Lee B 2016 Appl. Opt. 55 A71Google Scholar
[19] Lee S, Lee B, Cho J, Jang C, Kim J, Lee B 2017 IEEE Photon. Technol. Lett. 29 82Google Scholar
[20] Li Y N Q, Yang Q, Xiong J H, Yin K, Wu S T 2021 Opt. Express 29 42696Google Scholar
[21] Xiong J, Yin K, Li K, Wu S T 2021 Adv. Photonics Res. 2 2000049Google Scholar
[22] Xie Y, Kang M W, Wang B P 2014 Appl. Opt. 53 4206Google Scholar
[23] Zhang Y N, Zhu X L, Liu A, Weng Y S, Shen Z W, Wang B P 2019 Appl. Opt. 58 G84Google Scholar
[24] Shen Z W, Zhang Y N, Weng Y S, Li X H 2017 IEEE Photonics J 9 7000911Google Scholar
[25] Piao J A, Li G, Piao M L, Kim N 2013 J. Opt. Soc. Korea. 17 242Google Scholar
[26] Piao M L, Kim N 2014 Appl. Opt. 53 2180Google Scholar
[27] Piao M L, Kwon K C, Kang H J, Lee K Y, Kim N 2015 Appl. Opt. 54 5252Google Scholar
[28] Zhu J, Yang T, Jin G F 2013 Opt. Express 21 26080Google Scholar
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图 4 单片全息透镜的成像原理图, 红、绿和蓝线分别为不同视场的物光线(图中FOV为视场角; HOEL为全息透镜)
Fig. 4. Principle diagram of the imaging process of a singlet HOE lens and the red, green and blue rays are the object rays with different fields of view. (FOV represents the field of view and HOEL represents the holographic optical element lens)
表 1 全息透镜成像系统的光学参数
Table 1. Optical parameters of HOE lens imaging system.
参数 数值 眼盒大小/mm 10 视场角/(°) 18 全息透镜焦距/mm 65 红、绿、蓝光栅角带宽/(°) 12 -
[1] Xiong J, Hsiang E L, He Z, Zhan T, Wu S T 2021 Light: Sci. Appl. 10 216Google Scholar
[2] Zhan T, Yin K, Xiong J, He Z, Wu S T 2020 iScience 23 101397Google Scholar
[3] 史晓刚, 薛正辉, 李会会, 王丙杰, 李双龙 2021 中国光学 14 1146Google Scholar
Shi X G, Xue Z H, Li H H, Wang B J, Li S L 2021 Chin. Opt. 14 1146Google Scholar
[4] Yu C, Peng Y F, Zhao Q, Li H F, Liu X 2017 Appl. Opt. 56 9390Google Scholar
[5] Han J, Liu J, Yao X C, Wang Y T 2015 Opt. Express 23 3534Google Scholar
[6] 金闻嘉 2020 硕士学位论文 (杭州: 浙江大学)
Jin W J 2020 M S. Dissertation (Hangzhou: Zhejiang University) (in Chinese)
[7] Peng H C, Cheng D W, Han J, Xu C, Song W T, Ha L Z, Yang J, Hu Q X, Wang Y T 2014 Appl. Opt. 53 H177Google Scholar
[8] Li G, Lee D, Jeong Y, Cho J, Lee B 2016 Opt. Lett. 41 2486Google Scholar
[9] Chang C, Bang K, Wetzstein G, Lee B, Gao L 2020 Optica 7 1563Google Scholar
[10] 刘奡 2019 博士学位论文 (南京: 东南大学)
Liu A 2019 Ph. D. Dissertation (Nanjing: Dongnan University) (in Chinese)
[11] 邬融, 孙明营, 周申蕾, 乔战峰, 华能 2020 物理学报 69 234209Google Scholar
Wu R, Sun M Y, Zhou S L, Qiao Z F, Hua N 2020 Acta Phys. Sin. 69 234209Google Scholar
[12] Cheng D W, Wang Y T, Hua H, Talha M M 2009 Appl. Opt. 48 2655Google Scholar
[13] Pulli K 2017 Sid Symposium Digest of Technical Papers 48 132Google Scholar
[14] Li G, Jeong J, Lee D, Yeom J, Jang C, Lee S, Lee B 2015 Opt. Express 23 33170Google Scholar
[15] Jang C G, Mercier O, Bang K, Li G, Zhao Y, Lanman D 2020 ACM Trans. Graph. 39 184Google Scholar
[16] Maimone A, Wang J 2020 ACM Trans. Graph. 39 67Google Scholar
[17] Jang C, Hong K, Yeom J, Lee B 2014 Opt. Express 22 27958Google Scholar
[18] Jang C, Lee C K, Jeong J, Li G, Lee S, Yeom J, Hong K, Lee B 2016 Appl. Opt. 55 A71Google Scholar
[19] Lee S, Lee B, Cho J, Jang C, Kim J, Lee B 2017 IEEE Photon. Technol. Lett. 29 82Google Scholar
[20] Li Y N Q, Yang Q, Xiong J H, Yin K, Wu S T 2021 Opt. Express 29 42696Google Scholar
[21] Xiong J, Yin K, Li K, Wu S T 2021 Adv. Photonics Res. 2 2000049Google Scholar
[22] Xie Y, Kang M W, Wang B P 2014 Appl. Opt. 53 4206Google Scholar
[23] Zhang Y N, Zhu X L, Liu A, Weng Y S, Shen Z W, Wang B P 2019 Appl. Opt. 58 G84Google Scholar
[24] Shen Z W, Zhang Y N, Weng Y S, Li X H 2017 IEEE Photonics J 9 7000911Google Scholar
[25] Piao J A, Li G, Piao M L, Kim N 2013 J. Opt. Soc. Korea. 17 242Google Scholar
[26] Piao M L, Kim N 2014 Appl. Opt. 53 2180Google Scholar
[27] Piao M L, Kwon K C, Kang H J, Lee K Y, Kim N 2015 Appl. Opt. 54 5252Google Scholar
[28] Zhu J, Yang T, Jin G F 2013 Opt. Express 21 26080Google Scholar
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