全息波导耦合元件是增强现实显示系统的关键光学元件,光束垂直入射至全息波导板中通过入耦合元件改变光束传播方向,在波导板中形成波导现象传输至出耦合元件处,通过出耦合元件再次改变传输方向从全息波导板出射至人眼。当入耦合元件与出耦合元件均为透射式或反射式耦合元件时,两次改变光束传播方向的角度值相等。根据全息波导的成像原理,结合k矢量圆理论与全息光学记录原理,设计了全息波导入耦合元件与全息波导出耦合元件的对称型周期结构。利用MATLAB软件模拟了全息波导耦合元件记录时的干涉光强模型,实验结果与所设计的耦合元件周期结构数据吻合;利用COMSOL软件模拟了全息波导耦合元件对光束传输角度的改变过程,实验结果与理论改变光束传播方向的角度值一致。实验证明了两个全息波导耦合元件以互为对称的结构排布在全息波导光学系统中,能够满足全息波导光学系统对光束传播方向的要求。

The holographic waveguide coupling element is a key optical component of the holographic waveguide imaging system. The beam is perpendicularly incident into the holographic waveguide plate and changes the beam propagation direction through the in-coupling element. A waveguide phenomenon is formed in the waveguide plate and transmitted to the out-coupling element. The direction of transmission is changed again from the holographic waveguide plate to the human eye through the coupling element. When both the in-coupling element and the out-coupling element are transmissive or reflective coupling elements, the angle values of changing the beam propagation direction twice are equal. Based on the imaging principle of holographic waveguide, combined with k-vector circle theory and holographic optical recording principle, a symmetric periodic structure of the holographic waveguide in-coupling element and the holographic waveguide out-coupling element is designed. The interference light intensity model of the holographic waveguide coupling element is simulated by MATLAB software. The change of the beam propagation angle caused by the coupling element of the holographic waveguide is simulated by using COMSOL software. The experimental results are consistent with the theoretical change of the beam propagation direction. It is proved that the two holographic waveguide coupling elements are arranged symmetrically in the holographic waveguide optical system, which can meet the requirements of the holographic waveguide optical system for the beam propagation direction.