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470 nm和632 nm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 full-color waveguide holographic head-up display, the color is always uneven or the structure is over-complex. A novel double coupling grating structure is designed and optimized with embedded layers of different refractive indexes and thicknesses. Based on rigorous coupled-wave analysis (RCWA), the calculations show that the structure can achieve a more uniform color imaging in the primary field of view. It′s simplified and reliable for mass production. The double-grating is designed with central wavelength of 470 nm and 632 nm, respectively, to compensate the diffraction energy. After optimization, when the incident angle changes during the range from -11° to 11°, the diffraction efficiency (DE) of the RGB wavelengths is greater than 85% in the primary field of view and the maximum efficiency differs by less than 5%.