Design Method Of Diffractive Optical Waveguide Near-eye Display

Near-Eye Display Device（NED）is a visual optical system that puts a micro-display screen in front of observer’s eyes to provide an immersive viewing experience.Whether it’s from the early military flight applications,or now into the civilian and entertainment fields,near-eye display devices have played an irreplaceable role in the display device,which also reflects the comfort,portability,and reality of human display devices.This paper refers to the past design experience of near-eye display devices,selects the current design scheme with superior performance,and combines the accuracy of the existing grating processing technology to meet the needs of large field of view and large exit pupil as much as possible,and proposes a design of diffractive optical waveguide NED.The main research results and innovations of the thesis are as follows:（1）Research the basic principles and system structure of various near-eye reality device systems,and compare the structure and performance of various waveguide NED devices,and propose a device that achieve a compact overall device,good portability,and large field of view and large exit pupil expansion area technical solution for near-eye augmented reality equipment.Based on the rigorous coupled wave analysis method and Powell algorithm,a new surface-relief diffraction grating waveguide design and optimization strategy is proposed.（2）For the design of the waveguide device system,a collimating lens system that meets the requirements of near-eye display devices is designed.Through reasonable distribution of optical power,a large field of view and small size of the lens system,as well as good imaging performance,are achieved;for NED devices the transmission optical path and the requirements of the grating coupler are designed to design a waveguide structure with good processing and damage resistance,which effectively avoids the secondary coupling effect of the grating;at the same time,the reasonable design of the waveguide structure allows the total reflection beam to be emitted.The pupil expansion area has enough width to avoid discontinuities in the exit pupil expansion area.（3）In accordance with the design requirements of the grating coupler of NED equipment,the coupling-in grating and coupling-out grating systems are designed respectively.Through rigorous coupling wave analysis theory,the initial grating structure design is obtained,and the directional acceleration algorithm is used to optimize the coupling grating,and a realization is proposed.Coupling grating design with large field of view diffraction efficiency uniformity.This design is not sensitive to the incident angle,the angular uniformity of the diffraction efficiency is 87.61%,and the average diffraction efficiency of the full field of view is 85.41%.Aiming at the requirement of uniformity of illuminance in the expanded area of exit pupil,a four-coupling grating design is proposed.This design reasonably distributes the reflected energy R₀ and diffraction order energy R_-1 of each grating,and combines the designed collimation system and the uniformity of the coupled-in grating illuminance.,Expand the exit pupil area and optimize the diffraction efficiency of the grating.（4）Complete the overall simulation of the light path of the NED device on the basis of the design,and analyze the uniformity of the illuminance of the exit pupil of the device through the simulation.The eye movement range of the NED device is 20mm×16mm measured by the simulation,and the uniformity of the illuminance within the scope of the exit pupil is optimized.23.79%increased to 98.27%,and the full field of view MTF of the device is greater than 0.2 at 18lp/mm,which meets the imaging quality required by the human eye.