Geometrical-lightguide-based head-mounted lightfield displays using polymer-dispersed liquid-crystal films

Integrating the promising waveguide or lightguide optical combiners to head-mounted lightfield display (LF-HMD) systems offers a great opportunity to achieve both a compact optical see-through capability required for augmented or mixed reality applications and true 3D scene with correct focus cues required for mitigating the well-known vergence-accommodation conflict. Due to the non-sequential ray propagation nature of these flat combiners and the ray construction nature of a lightfield display engine, however, adapting these two technologies to each other confronts several significant challenges. In this paper, we explore the feasibility of combining an integral-imaging-based lightfield display engine with a geometrical lightguide based on microstructure mirror arrays. The image artifacts and the key challenges in a lightguide-based LF-HMD system are systematically analyzed and are further quantified via a non-sequential ray tracing simulation. We further propose to utilize polymer-dispersed liquid-crystal (PDLC) films to address the inherent problems associated with a lightguide combiner such as increasing the viewing density and improving the image coupling uniformity. We finally demonstrate, to our best knowledge, the first lightguide-based LF-HMD system that takes the advantages of both the compact form factor of a lightguide combiner and the true 3D virtual image rendering capability of a lightfield display.