Full-color holographic near-eye displays

Near-eye displays (NEDs) for augmented reality (AR) applications are expected to be the next computing paradigm. NEDs offer to combine computer-generated visuals with our physical world in a seamless fashion. Depth cues and natural blurring of images are all critical for a comfortable 3D experience with near-eye displays. Holography for NEDs is a commonly accepted strong candidate in meeting the human visual system's demands by offering natural depth cues. Holographic near-eye displays (HNEDs) deliver virtual images using computer-generated holograms (CGHs) displayed on spatial light modulators (SLMs). Holographic displays allow for a vast range of optical architectures that are not possible with conventional microdisplay-based designs. However, due to the current technological limitations of SLMs, most existing HNEDs have a limited field of view (FOV) and viewing region around the eye pupil (i.e., eyebox size). However, improving SLMs have a positive impact on improving FOV and eyebox size in HNED design. In this thesis, we propose various solutions for overcoming the current technological limitations of SLMs and HNEDs. We start by offering a paraxial matrix optics-based analysis of a conventional HNED design to formulate the relation between eyebox, FOV, and SLM characteristics. We developed a CGH computation procedure that applies to arbitrary paraxial optical architectures, where the SLM illumination beam can be collimated, converging, or diverging. The virtual or real SLM image as seen by the eyebox plane may form at an arbitrary location. Using this approach, we designed full-color HNEDs with varying FOV and resolution characteristics and proper depth control. We demonstrated a lensless HNED architecture with diverging beam illumination, which provides 3D images within a wide FOV (70°) at retinal resolution (30 cycles-per-degree), exceeding 4,000 resolvable pixels on a line. The experiments using binary holograms imprinted on masks prove that the proposed CGH computation procedure eliminates chromatic aberrations and speckle noise observed in all other laser-based displays. We also designed two systems with 10° and 20° FOV using dynamic SLM. While the first design has a uniform resolution, the second design demonstrates a foveated display, which has gradually degrading resolution across the FOV. To further explore HNED architectures, we analyzed the light source coherence requirements and investigated HNED designs utilizing light-emitting diodes (LEDs). While laser light sources have the highest degree of spatial and temporal coherence, lasers' usage in direct contact with a human may cause health hazards. We show that under certain design restrictions, it is possible to utilize LEDs instead of lasers and get better quality holographic images. We analyzed the effect of LED emission areas on image resolution, quality, and depth perception. Lastly, we designed micro-mirror array (MMA) based thin components and demonstrated that those could be used as off-axis thin lenses in AR displays to reduce size and volume.