衍射光栅是全息波导头盔显示系统中的关键元件, 但在彩色显示中, 因其特性, 红绿蓝三色波长的入射光会衍射不同的角度。在波导中经历数次全反射后, 三色光在出射光栅的不同位置处出射从而造成色散。针对彩色全息波导头盔显示系统中的色散问题, 结合全息波导系统本身的特点, 提出了采用多层波导的方法矫正色散。根据不同波长入射光的衍射角, 设计了四层波导, 每层采用不同折射率的材料, 对各个波长的光路进行矫正, 以此来达到矫正色散的目的;最后通过仿真分析验证设计的准确性。结果表明, 红绿蓝三色的光线几乎在同一位置处出射, 三色图案高度重叠。因此采用所提多层波导设计的方法能够有效解决全息波导头盔显示系统中的色散问题。

Diffraction grating is a key component in holographic waveguide helmet-mounted display system. However, in color display, incident polychromatic light comprised of red, green and blue wavelengths will diffract different angles. After several total reflections in the waveguide, the light of three wavelengths arrives at different locations at the output grating, thereby resulting in dispersion. Aiming at the chromatic dispersion problem in the holographic waveguide helmet-mounted display system and based on the characteristics of holographic waveguide system itself, this paper presents a multi-layer design of the waveguide for dispersion correction. According to the diffraction angle of the incident light with different wavelengths, waveguide of four layers with different refractive indexs was designed. The optical paths of different wavelengths were corrected to achieve the goal of dispersion correction. Simulations were carried out to verify the accuracy of the design. The results show that: the red, green, and blue light almost exit at the same position, presenting a highly overlapping color pattern. Therefore, the method can effectively solve the problem of the dispersion of the holographic waveguide helmet-mounted display system.