Research On Imaging Simulation Of Polarization Volume Grating Holographic Waveguide Display

Head Mounted Display-Augmented Reality(HMD AR)is currently a hot spot in the field of information display technology.Among the various technical methods for realizing HMD AR,optical waveguide technology has become the mainstream technical solution for HMD AR due to its light and thin volume and large exit pupil area.Waveguide coupling is the most critical technology in the optical waveguide display system,which directly determines the imaging effect of the waveguide display system.We used polarized light orientation technology and liquid crystal self-assembly characteristics to develop a new type of coupling optical element—Polarization Volume Grating(PVG),which has a wide response bandwidth and unique polarization characteristics.The application of PVG in the optical waveguide display can improve the field of view(FOV)and color performance of the final imaging.However,due to the complicated principles of physical optics and geometric optics involved at the same time,there is currently a lack of effective imaging simulation methods for PVG holographic waveguide display systems.Therefore,a simulation tool for PVG holographic waveguide display system imaging is urgently needed.In order to solve this problem,the following three tasks is carried out:(1)Rigorous Coupled Wave Analysis(RCWA)theory is used to establish a PVG electromagnetic field calculation model,and this model is used to simulate the diffraction and polarization characteristics of PVG.The simulation results show that PVG is sensitive to the polarization state of incident light that PVG exhibits high diffraction efficiency for circularly polarized light whose rotation direction is the same as that of liquid crystal optical axis.It is also found in the simulation that the tilt angle of PVG liquid crystal optical axis will affect the polarization sensitivity of PVG and the polarization state of diffracted light.(2)The realization and optimization of PVG are completed in the optical design software ZEMAX.Through C++ programming,the PVG RCWA model is included in the dynamic link library(DLL).The DLL is called in ZEMAX to realize the integration of the physical optics of the PVG diffraction and the geometric optics of the imaging system.The Monte Carlo method is used to optimize the ZEMAX ray tracing method,which greatly improves the simulation speed and accuracy of the PVG waveguide display system.The test proves that the improved ZEMAX has the simulation function of PVG element.(3)The PVG holographic waveguide display system is established by using the improved ZEMAX,and the imaging effects of the one-dimensional pupil expansion structure and the twodimensional pupil expansion structure is simulated.The brightness and color unevenness in the simulation results is analyzed.The multi-layer composite grating is used to expand the FOV of the waveguide display system,and the composite grating and the three-layer waveguide structure are used to realize the color waveguide display.In this thesis,the RCWA electromagnetic field calculation model is established for the PVG structure,and the model is called in ZEMAX through DLL,so that ZEMAX has the imaging simulation function of the PVG holographic waveguide display system,which provides a simulation tool for the realization of the PVG holographic waveguide display system.