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在彩色波导全息平视器的设计中,易出现色彩不均和结构复杂的问题。将折射率、厚度各异的膜层,分别嵌入双层波导中,对一种新型的双层耦合光栅结构进行了优化设计。基于严格耦合波理论(RCWA)的计算表明,该双层光栅可实现主视场内较均匀的彩色成像,且结构精简。相较于传统的体全息元件,该结构批量制造的可靠性更高。双层光栅的设计分别以470nm和632nm为中心波长,实现衍射能量的相互补偿。优化结构参数后,当入射角在[-11°,11°]内变化时,主视场内RGB三波长的衍射效率(DE)可大于85%,各波长间最大的效率差异可小于5%。
In the design of color waveguide holographic head-up device, the problem of color unevenness and complicated structure tends to occur. The films with different refractive index and thickness are respectively embedded in double waveguides, and a novel double-layer coupled grating structure is optimized. The calculation based on RCWA shows that the double grating can achieve a more uniform color image in the main field of view and the structure is simplified. Compared with the traditional body holographic element, the structure is more reliable in mass production. The design of double-layer grating is centered at 470nm and 632nm, respectively, to achieve the mutual compensation of the diffraction energy. When the incident angle is changed within [-11 °, 11 °], the diffraction efficiency (DE) of the three wavelengths of RGB in the main field of view can be greater than 85% after optimization of the structural parameters. The maximum efficiency difference between the wavelengths can be less than 5% .