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题名	大视场虚拟现实头盔显示器光学系统研究
作者	孟祥翔
学位类别	博士
答辩日期	2015-05
授予单位	中国科学院大学
导师	刘伟奇
关键词	虚拟现实 头盔显示器 部分双目重叠 大视场 光学系统 非球面
其他题名	Study on Large Field of View Optical System of Virtual Reality Head-mounted Display
学位专业	光学
中文摘要	虚拟现实是利用计算机生成多感知的数字化环境并使人与之发生交互作用的技术，在航空航天、军事训练、模拟仿真、虚拟设计、医疗、教育、娱乐等领域有着非常广泛的应用。虚拟现实技术既包括完全脱离现实环境的沉浸式虚拟现实，也包括叠加于现实环境之上的增强现实。头盔显示器是虚拟现实技术中的关键设备，承担着视觉信息的模拟仿真。大视场头盔显示器所实现的沉浸感是虚拟现实技术的一个重要特征，视场越大，沉浸感越强。但对于固定的显示屏，在增大视场的同时，会导致分辨率的降低。随着显示屏制造技术的不断发展，像素密度和像素数目不断提高，在为头盔显示器提供更多选择的同时也对其光学系统的设计提出了更高的要求。部分双目重叠是一种扩大双目视场范围并且保证分辨率不变的有效方法，其前提是优良的大视场单目光学系统设计。本文对大视场虚拟现实头盔显示器光学系统进行了深入研究。主要内容如下： (1) 理论分析了目视光学系统的轮廓尺寸计算和像差特性；分析了提高视场大小对于同轴和离轴两种结构带来的设计难点，为HMD光学系统的设计提供了理论依据。以人眼特性为依据，分析了HMD的主要设计要求及指标。 (2) 推导了发散式部分双目重叠形式的单目视场、双目视场、重叠视场之间的关系式。分析了大视场低畸变的双椭球HMD在对除畸变以外的其他像差校正的局限性。提出了一种基于双自由曲面反射镜的大视场HMD光学系统，与双椭球结构对比，新结构使得系统MTF提高两倍左右，并简化了中继透镜组和后继透镜组，避免了“W”或“M”形非球面透镜面形的出现。系统出瞳直径8mm，单目视场范围为：106.3°(H)80°(V)，最大相对畸变为6.97%，单目像素分辨率为19201200。采用光轴向外倾斜的部分双目重叠形式，光轴向外各倾斜8°，双目水平视场范围为122.3°(H)80°(V)，双目重叠水平视场为90.3°。 (3) 分析了同轴广角目镜的像差特点，采用三片玻璃透镜和一片塑料透镜，引入五个非球面，实现了基于同轴结构的对角视场不小于114°、全视场相对畸变值小于9.6%、像元分辨率为19201080的虚拟现实头盔单目光学系统设计。系统出瞳直径10mm，单目视场范围为：105.6°(H)×73.08°(V)。采用光轴向外倾斜的部分双目重叠形式，光轴向外各倾斜18°，双目水平视场范围为141.6°(H)73.08°(V)，双目重叠水平视场为69.6°。 (4) 分析了同轴大视场HMD单目光学系统的加工公差和装配公差，并数值分析验证了非球面面形精度公差范围。采用超精密数控光学铣磨加工中心、数控光学表面成型技术对玻璃非球面进行精磨与抛光。使用超精密单点金刚石车削技术加工塑料非球面透镜，并采用高精度接触式轮廓测量仪进行了面形检测。系统的镜筒采用加工中心一体加工成薄壁结构，双目结构通过左旋和右旋的两种螺纹实现瞳距在55~71mm范围内可调节。同时根据部分双目重叠方式的特点进行了图像校正，针对部分双目重叠HMD斜置视场时的双目不一致问题，提出了双目图像的平移校正模型。
英文摘要	Virtual reality is the technology that makes people interact with the digital environments which is produced by computer. It has widely used in aerospace, military training, simulation, virtual design, health care, education, entertainment and other fields. Virtual reality technology includes not only immersive virtual reality which is separated the true world absolutely, but also augmented reality which is overlapped on the true world. Head-mounted display (HMD) is the key equipment in virtual reality technology, which bears the simulation of visual information. Immersion is an important feature of virtual reality, which is achieved by large field of view (FOV) HMD, and the larger the FOV, the stronger the sense of immersion. However, for a fixed display, the resolution will be decreased by the field of view increasing at the same time. With the development of display manufacturing technology, the number of pixels and pixel density are rising speedily. The new displays provide more choice for the HMD and also put forward higher requirements for the design of the optical system of the HMD. Partial binocular overlap is an effective way to expanding binocular field of view and to ensure the resolution constant at the same time, provided that the excellent design of the optical system with large FOV. This article conducted in-depth research on the large field of view of virtual reality head-mounted display optical system. The key contents include the following work: (1) The calculation of the size and outline and the aberration characteristics of visual optical system were analyzed theoretically. The design difficulties of coaxial and off-axis optical system which brought by increasing FOV were proposed. These analyses provide a theoretical basis for the design of HMD optical system. Based on the characteristics of the human eyes, the design requirements and the main indicators of HMD were analyzed. (2) The relationship of the binocular FOV and monocular FOV and binocular overlapped FOV of divergent overlap was derived firstly. The aberration correction limitations of the double ellipsoid HMD which could achieve large FOV and low distortion were analyzed. Then the double free-form mirrors large FOV HMD optical system was proposed. Compared with the double ellipsoid structure, the new structure makes the system MTF increased by 200%, and simplifies the relay lens group and the subsequent lens group, and avoids the "W" or "M" shape of the aspheric lens surface. The monocular FOV is 106.3°(H)80°(V). The exit pupil diameter is 8mm. The maximum relative distortion is 6.97% and the monocular pixel resolution is 19201200. Through divergent overlap of optical system tilt outside and tilt outside 8°of each optical system, the binocular FOV is 122.3°(H)80°(V) and the horizontal binocular overlapped FOV is 90.3°. (3) The aberration characteristics of coaxial wide-angle eyepiece were analyzed firstly. Then a new large FOV coaxial optical system which was used in immersive virtual reality was proposed. The new optical system uses three pieces of glass lens and a plastic lens, and includes five aspheric surfaces. The diagonal FOV of the new optical system is 114°. The relative distortion of the whole FOV is less than 9.6%. The monocular pixel resolution is 19201080. The exit pupil diameter is 10mm and the monocular FOV is105.6°(H)×73.08°(V). Through divergent overlap of optical system tilt outside and tilt outside 18°of each optical system, the binocular FOV is 141.6°(H)73.08°(V) and the horizontal binocular overlapped FOV is 69.6°. (4) The machining tolerances and assembly tolerances of the new large FOV coaxial optical system were analyzed and the aspheric surface accuracy tolerances were verified by numerical analysis.Then the glass aspheric surfaces were grinded by ultra-precision CNC grinding optical machining centers and polished through computer controlled optical surfacing technology. The plastic aspheric lenses were processed through ultra-precision single point diamond turning technology. The aspheric surfaces accuracy of plastic aspheric lenses was tested by high-precision contacting contour measuring machine. The mechanical structures of the large FOV coaxial optical system were processed into thin-walled form by machining center. The IPD of the binocular structure is adjustable within 55~71mm by left-handed and right-handed screw thread. The image was corrected according the characteristics of partial binocular overlap. For the binocular scence inconsistencies when the HMD is titled, the image translation correction model was proposed.
公开日期	2015-12-24
内容类型	学位论文
源URL	[http://ir.ciomp.ac.cn/handle/181722/48883]
专题	长春光学精密机械与物理研究所_中科院长春光机所知识产出
推荐引用方式 GB/T 7714	孟祥翔. 大视场虚拟现实头盔显示器光学系统研究[D]. 中国科学院大学. 2015.

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