Design of Optical Near-eye See-through Display

The Metaverse is a digital living space built by human beings for an extended experience beyond the real world. It is a virtual world in nature that maps, transcends, and reacts with the real world, with a new social system. The Metaverse is featured by highly immersive and interactive in which people can socialize, learn, play, live and work, just as they do in the real world. Augmented reality (AR) is an important medium to support the Metaverse by connecting the virtual world and the real world. The optical imaging module is a key component of AR display, providing the users with a clear digitalized image or video that can be superimposed on a realistic external view. For AR, the main requirements on the optical module include a large field of view (FOV), large pupil exit, clear display, small size, light weight, and a small shift in the centre of gravity. Although there have been significant advances in AR display in the recent decade, better optical performance and more compact hardware structures are still being pursued as a long-term goal for researchers. This is also a major barrier that obstructs the wide uptake of AR devices in the
consumer market, as it is still quite challenging to make a satisfactory balance between the system compactness and optical display performance. Based on the requirements mentioned above, this thesis presents an in-depth study of near-eye see-through displays and proposes some innovative research outputs on both the optical system design and AR application mode. The main contents are as follows: This thesis starts with the motivation for carrying out this project, followed by a comprehensive literature review. The identified challenges in this area underpin the objectives presented in Chapter 1. In Chapter 2, based on the characteristics of human eyes, the main design requirements
and performance indicators of AR imaging systems are analysed. By comparing the mainstream AR display technologies, the geometrical waveguide is considered as the most promising solution in virtue of its 85% transparency, large FOV over 50°, large eye relief around 20mm, large eye box, smaller size, and light weight. In Chapter 3, based on the requirements of the AR display system, we develop one-dimensional geometrical waveguide with 72º FOV and two-dimensional geometrical waveguide with 69° horizontal FOV and 56° vertical FOV. The illumination uniformity can reach 0.83 after optimization. Stray lights causing ghost images are systematically discussed and tailored solutions are presented which suppress the stray lights under 1% proved by simulation. Another major barrier for AR display, vergence accommodation conflicts are discussed in Chapter 4. A dual-layer waveguide design is proposed to achieve depth changing with 34° FOV to mitigate the dizziness caused by vergence accommodation conflicts in long time use. The angular uniformity of the intensity across the exit pupil is more than 70%. Another varifocal geometrical waveguide is also developed and evaluated by the illumination of different depths. Manufacturing of geometrical waveguide is discussed in Chapter 5, which is a major obstacle for widespread uptake of such a promising solution. Besides, the evaluation indicators, tolerance and characterization methods of each step are analysed and proposed. Finally, based on the study on near-eye see-through display, a fast positioning and calibration system combining waveguide and micro-lens array is proposed for improving the depth accuracy of 3D imaging. The system could filter out a useful object from complex background or in poor lighting condition, and scope targeted information rapidly to avoid the waste of time and resources on useless work. It can also calibrate the synthesized images by plenoptic camera.