Effects of image focal depth in geometrical lightguide head mounted displays

Waveguide or lightguide has the advantages of light weight, small volume and relatively high efficiency and thus is considered as one of the promising solutions to the optical combiner required for optical see-through augmented reality displays. Although there exist a few commercial products utilizing lightguides as the optical combiners, few works discussed the potential image artifacts caused by the ray bundle collimation errors in lightguides. In this paper, we discussed three causes of collimation errors in the geometrical waveguide: lightguide manufacture tolerance, change of image focal depth, and curved lightguide substrate. Based on the simulation and experiment results of the first two causes, we demonstrated two different types of image artifacts in the geometrical-waveguide-based AR displays.