Self-aligned double-sided grating diffractive waveguide with enhanced efficiency

A self-aligned double-sided grating diffractive waveguide for augmented reality is described. This double-sided grating waveguide adopts a parallelogram grating vector design, which effectively addresses the issue of grating vector misalignment caused by low-angle alignment precision in the double-sided nanoimprint lithography process, enabling large-scale production. Furthermore, by adding single-sided turning gratings in specific regions of the waveguide, the dispersed in-coupled energy from the double-sided in-coupling gratings is fully utilized, ultimately improving the efficiency and uniformity of the self-aligned waveguide. Using non-sequential ray tracing and the Fourier Model Method, we present the design results of two sets of self-aligned waveguides with optimized grating profile parameters. One design prioritizes efficiency, achieving an average efficiency of 4550nits/lm (~7.16% for a 30° FOV and 13mm × 11mm eyebox) at the center of the eyebox. The other design emphasizes uniformity, with a central average efficiency of 1781nits/lm (~3.18% for a 30° FOV and 13mm × 11mm eyebox).