For the waveguide displays, low diffraction efficiency and narrow response bandwidth at high spatial frequency limit the development of coupling elements. In this paper, a dual-monomer, with higher and lower refractive index modulation separately, allyl propionate H-PDLC system is proposed. After experimental optimization, the diffraction efficiency of prepared high transmittance (more than 90% in the visible spectrum) H-PDLC gratings is up to 91%, and the response bandwidth is 99 nm at 973 lp/mm. By increasing the proportion of initiator and changing the radiation conditions, the diffraction efficiency is optimized to 75.4% and the response bandwidth is 29 nm at 2941 lp/mm. The experiments demonstrate that the high-frequency H-PDLC gratings have considerable application prospects as coupling elements for augmented reality optical waveguide display systems.
Holographic displays enable the formation of a three-dimensional particle field distribution and is promised to be one solution of the key problems in present virtual and augmented reality displays. The biggest challenge in the computer-generated holography (CGH) is the high consuming calculation time and the restricted field of view due to the micro display screen. In order to solve the above mentioned problems, we propose a method for machine learning accelerated lensless holographic projection, which is based on the reconstruction of complex amplitude image from phase-only CGH. The runtime of generating the phase-only CGH is half of traditional iterative method. The complex amplitude image can achieve the maximum diffraction bandwidth of the spatial light modulator (SLM). The feasibility of this method is verified by experiments.
As an important diffractive optical element, the holographic grating has always been favored by users for its high diffraction efficiency and low cost. Especially in recent years, its value in the near-eye display waveguide structure has been further improved and explored. This paper derives a set of interference field theoretical models suitable for flexible curved radius grating, through the modification of the traditional two-wave interference principle. Based on this, the morphological law of the required interference pattern can be simulated. On the other hand, when we change the radius of flexible grating, the focus position of the diffraction field can be changed correspondingly, so as to achieve the purpose of quantitative focusing. Experiments show that the different degrees of bending of flexible curved radius grating can effectively adjust the focal length of the holographic element, and its diffraction efficiency can always be maintained above 88%. What’s more, the imaged brightness uniformity consistent, no interference of diffraction ghost lines, pave the way for the subsequent research on the key technologies of different surface-shaped curved waveguides.
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