Augmented Reality Display Based On Liquid Crystal Devices

The realization of natural and comfortable 3D display is the ultimate goal of display technology.In recent years,the augmented reality(AR)technology has been developed rapidly which brings a new appliacation scenario for the 3D display technology.However,most of the current products have accommodation-vergence conflict problem,which makes viewers feel tired and visual fatigue after long-term use.To solve this problem,many true 3D technologies are suggested to be used in AR displays.Compared with other true 3D displays,multiplane displays use discrete 2D slice images to construct 3D objects,which have many advantages,such as compact design,low computational complexity,and high image quality.The key components of multiplane displays using the time-multiplexing method are fast tunable optical devices.For AR display applications,small size and low weight of tunable optical devices are required.The liquid crystal device realized by the spatial distribution of the refractive index has many excellent electro-optic properties: electronic controllable,flat panel design,thin and compact design.In order to realize multiplane AR display,our work focuses on liquid crystal devices,including normal mode polymer stabilized liquid crystal(PSLC),reverse mode PSLC,and Pancharatnam-Berry(PB)liquid crystal lens.The main work includes:1.The multiplane AR display based on the normal mode PSLC scattering shutter is studied.In order to realize the multiplane augmented reality display using the time multiplexing method,the tunable device needs to have a fast response time,and the fast-switching normal mode PSLC which is capable of acting as a screen applied in the multiplane AR display system.(1)The working mechanism of normal mode PSLC is studied,and a dynamic response time of 0.65 ms is achieved.(2)A compact multiplane AR display system is designed.By switching the states of the normal mode PSLC in time sequence,images at different depths are constructed and the multiplane AR display function is realized.2.We study on the multiplane AR display based on reverse mode PSLC.In order to reduce the power consumption based on the liquid crystal scattering film,the reverse mode PSLC is proposed to be used in multiplane display because of the the advantages of driving method,low threshold voltage,and high optical transmittance.(1)The working mechanism of the reverse mode PSLC is investigated,and the influence of different factors on its electro-optic characteristics are analyzed,and a fast response time within 2 ms is achieved.(2)Multiplane AR display system is designed to realize multiplane display with correct focus cues.3.Investigation of the full-color multiplane display based on PSLC is implemented.In order to realize the full-color multiplane display with higher image quality,and more comfortable experience,it is proposed to use PSLC in the full-color multiplane AR system.(1)The stable transmittance spectra of the PSLC are studied,and the diffraction characteristics of the digital micromirror device are analyzed.(2)We designed a quasi-collimated color projection system,using RGB LED as illumination light,digital micromirror device as a microdisplay,to implement and demonstrate a 62.5 Hz binocular full-color multiplane AR display system with correct depth information.4.The multiplane AR display based on PB liquid crystal lens is investigated.In order to realize the construction of images at different planes and the display system with small size and light weight,PB liquid crystal lens is used in the multiplane display system.By changing the focal length of the lens,the construction of pictures with different depths can be realized.(1)The polymer-stabilized PB liquid crystal lens fabricated based on the photoalignment method is studied.A multiplane display system is designed,and a multiplane AR display with the same field of view is realized by adopting a double-telecentric system composed of a 4f system.A dual-plane AR display was set up and implemented.(2)An achromatic PB liquid crystal lens is proposed,and we study on its focusing effect on three R,G,B wavelengths,and a full-color multiplane display system based on achromatic lens is designed.