Design Of Grating Waveguide Head-Mounted Display System Using Differential Evolution Algorithm

With the growing demand for information,the grating waveguide head-mounted display provides high performance and a wide range of applications,making it an extremely valuable research.However,there are some issues such as small field of view,low diffraction efficiency and illuminance nonuniformity.Moreover,it is difficult to obtain the optimal solution of grating using general methods;and the sub-wavelength grating is hard to fabricate.To address the above issues,an optimization method based on differential evolution algorithm to design a high-performance grating waveguide head-mounted display system is proposed here.The main research results and innovations of the thesis include:1.The grating coupler optimization method based on differential evolution algorithm for waveguide display system is proposed to improve the rationality of the design process and reliability of the design results.2.Based on differential evolution algorithm,a high-angular uniformity input grating coupler with natural vignetting compensation is designed.The average efficiency reaches 89.13% for TE polarization across horizontal field of view of 45°,and the diffraction efficiency distribution increases continuously with incidence angle.The angular uniformity is up to 0.8885.2400L/mm input and output grating coupler are optimized to improve the diffraction efficiency of the grating and improve the uniformity of the efficiency distribution.The average diffraction efficiency of input grating coupler is optimized from 6.45% to 37.21% for TE polarization.The efficiency distribution uniformity is optimized from 0.3358 to 0.8062,and the average diffraction efficiency is optimized from 1.60% to 36.82% for TM polarization.Besides,the average diffraction efficiency of output grating coupler is optimized from 1.59% to 8.82% for TE polarization,and the efficiency distribution uniformity is optimized from 0.0949 to 0.5902.3.The manufacturing process of the grating coupler is proposed.The input and output grating coupler samples are fabricated.The profile of the sample is tested under the scanning electron microscope and the verification experiment of grating period is built.The refractive index and film thickness of the sample are measured using an ellipsometer and a step profiler,respectively.The efficiency measurement system is built to measure the efficiencies of the grating coupler.The simulation results of the grating coupler are compared with the experimental results.Furthermore,the results show that the sample of input and output grating couplers meet the performance requirements of the waveguide display system.4.The eyepiece system is designed and optimized.The optical path tracing simulation and experiment of EPE phenomenon of the grating waveguide HMD system are completed.The uniformity of the simulation is optimized from 0.7896 to 0.8945.The uniformity of the experimental measurements is optimized from 0.8185 to 0.9060.The results show that the experimental results are nearly identical to the simulation results,and the EPE uniformity is improved.Moreover,the display imaging experiment of the grating waveguide display system is completed,and three sets of prototypes based on different image sources are processed.The display effect of the grating waveguide display system under different external illumination conditions is measured.The results show that the system has a clear,bright and uniform display effect.