Research On The Head-mounted Display System Using Polarization-insensitive Grating Waveguide

With the development of the information society and technology,the demands of mankind about information acquisition dimensions,methods,and speed,are constantly increasing.In terms of the types of information acquisition way,visual is the main information source of for people.In recent years,augmented reality or virtual reality technology as a new generation of information display and interaction technology,have been concerned by international and domestic departments,enterprises,and research institute.As the key technology of augmented reality,the head-mounted optical display system could meet the increasing application requirements with the continuous improvement of its optical performance.The grating-waveguide display system has been studied by many research institutes due to its advantages such as small size,light weight and high transparency.However,the current grating waveguide display system has low energy utilization due to the polarization sensitivity of the grating,causing the problem of low brightness display effect and high energy consumption.In order to solve this problem,this paper proposed a polarization-insensitive grating waveguide design method,and experimentally demonstrated a set of polarization-insensitive grating waveguide head-mounted display system.(1)This paper proposed a method of designing polarization-insensitive gratings based on the Rigorous Coupled Wave Analysis(RCWA)and the genetic algorithm.This paper simulated the proposed polarization-insensitive grating,and optimized the multi-objective parameters of the grating using genetic algorithm,and calculated the diffraction efficiency of the grating for different polarization states light source.Designed a polarization-insensitive grating waveguide display.The average diffraction efficiency of the TE polarization state of the in-coupling grating is 56.4%,the average diffraction efficiency of the TM polarization state of the in-coupling grating is 54.2%,the average diffraction efficiency of the non-polarization state of the in-coupling grating is 55.3%,and the average diffraction efficiency of the TE polarization state of the outcoupling grating is 42.7%,the average diffraction efficiency of the TM polarization state of the out-coupling grating is 11.7%,the average diffraction efficiency of the nonpolarization state of the out-coupling grating is 27.2%.The working center wavelength is 532 nm.(2)A polarization insensitive grating waveguide display system was designed,using a micro Organic Light-Emitting Diode(Micro-OLED)as the image source,and a fourpiece collimating lens structure was designed to complete the overall polarization insensitive grating waveguide display system.The ray tracing modeling was built,and simulation system got a good image display effect.(3)The experiment of measuring the diffraction efficiency of the grating was completed,and a prototype of the polarization-insensitive grating waveguide display system was built,and the display effect was photographed and tested.A polarizationinsensitive grating waveguide sample was fabricated based on nanoimprint technology.The pupil expansion effect of the grating was verified through the laser experiment,and the diffraction efficiency of the grating was measured.The experimental results showed that the diffraction efficiency of the in-coupling grating and the out-coupling grating in different polarization states have been improved.Meanwhile,the average diffraction efficiency of the coupled-in grating in the TE polarization state was increased from 6.1%to 21.0%,and the average diffraction efficiency in the TM polarization state was increased from 13.7% by 40.5%,and the average diffraction efficiency of the nonpolarization state was increased from 9.9% by 30.7%.The average diffraction efficiency of the out-coupling grating in the TE polarization state was increased from3.1% to 12.1%,and the average diffraction efficiency in the TM polarization state was increased from 0.8% to 10.7%,and the average diffraction efficiency of the nonpolarization state was increased from 1.9% by 11.4%,realizing the polarization insensitivity effect.The polarization-insensitive grating-waveguide display system realized a large field of view of 30°×22°,and the image quality was good,and the display effect was clear and bright.The design proposed in this paper effectively solved the polarization-sensitive characteristics of traditional gratings,improved the energy utilization and brightness of the system,improved the overall system energy consumption,and realized the highefficiency coupling of non-polarized light with a large field of view angle,and realized the combination of Micro-OLED and diffraction grating waveguide head-mounted display with good and bright display effect.