Study On The Mechanism And Key Technology Of The Colorful Holographic Waveguide Display

With the rapid development of technology,the helmet display(HMD)gradually installed to meet the requirements of lighter,large field of view,follow-up tracking,high resolution,full color,etc.of pilots in modern air combat.Also,it has begun to be obtained the attention in the research of consumer market.In the diffractive optical waveguide device,the Volume Holographic Grating waveguide scheme is a promising technical approach,which has significant advantages in terms of diffraction efficiency,fabrication cost,and design processing difficulty.The exploration of the direction has never stopped.However,at present,holographic waveguide display technology based on holographic body grating is still in the research stage,and there are still several problems to be solved,including: 1.Lack of unified system simulation platform covering geometric optics and wave optics,and comprehensive far field imaging and near-field coupling calculations mean huge computational power requirements;2.Limited by the refractive index modulation of holographic materials,the system's field of view(FOV)is small;The display uniformity,sharpness,color and other aspects have not yet reached the level of commercial requirements;4,the process and equipment for batch preparation are still to be further researched and developed.In view of the above problems,this thesis has carried out in-depth research and development on the color holographic waveguide display system,mastered several key technologies involved in it,and mainly carried out the following aspects of work,and achieved corresponding results:Based on the principle of wave optics and geometric optics,the holographic waveguide display device characteristics and imaging simulation platform were established for the first time through the combination of self-programming interface and commercial software platform.The combination of simulation and experiment revealed the volume holographic grating and waveguide display.The correlation between structural-related parameters and system imaging performance points out the key factors affecting system indicators and optimizes them accordingly.By configuring and optimizing the photopolymer material;designing and optimizing the structure of the holographic waveguide display;optimizing the grating parameters and the holographic exposure preparation process,the method of expanding the field of view angle of the volume holographic grating waveguide display system is established,and the principle design and experimental verification were carried out.Study analyzed the problem of uniformity of holographic waveguide display system under large field of view.In this paper,ray tracing is carried out in the waveguide conduction process and the coupling out process from different coupling angles with a large FOV range,and the output light intensity and FOV angle are extracted,the local peak efficiency of the grating is coupled out on the propagation path.The correlation model between uniformity selects the coefficient of variation of the sample group of the exit pupil as the criterion of uniformity of the system,and optimizes the efficiency distribution of the coupled output grating through the genetic algorithm program,while ensuring the overall light efficiency of the system.The optimization system has the requirement that the brightness uniformity is greater than 25% when displayed in red,green,blue and white display.In addition,the wavelength selectivity of the grating device and its own dispersion characteristics are a great challenge to realize the color display system.The paper discusses the research of wavelength recombination and cascading,system color shift mechanism to get the techniques and methods for displaying system color implementation;In this paper,through the study of the above key technologies in the color holographic waveguide display system,the simulation design model of the holographic waveguide display system is developed,and the high performance photopolymer holographic material is developed.The holographic grating preparation process system is designed.And successfully developed a prototype of the color holographic waveguide display system.The prototype has an exit pupil of 23mm*23mm;the FOV reaches 35°*25°,reaching the domestic leading level.