Augmented reality is still in its infancy and is projected to grow substantially over the next few years. Grating-based waveguides are now established as the key enabling display technology for merging the physical and digital worlds in implementations as diverse as near eye displays, auto HUDs and large-scale retail displays. Despite significant design effort, delivering wide field-of-view (FoV) color, daylight-compatible brightness and ultra-compact glasses-like form factors at an acceptable price remain major development hurdles for consumer AR displays. The form factor challenge is only partially met using thin waveguides; current picture generation units, comprising the microdisplay beam splitter and projection optics, are increasingly seen as too bulky to satisfy the aesthetic requirements of consumer eyewear, while traditional input, fold and output grating architectures occupy too much waveguide real estate. Brightness and power consumption are compromised by losses of typically 95% incurred in coupling light from a picoprojector into a waveguide. DigiLens is prototyping a compact wide angle, full-color laser-illuminated consumer AR waveguide based on its Integrated Dual Axis (IDA) waveguide architecture which uses Digilens’s proprietary Switchable Bragg Grating (SBG) technology. An IDA waveguide multiplexes beam expansion and extraction gratings using a high index modulation holographic LC-photopolymer material system optimized for wide angle multiplex grating applications. A 50-degree diagonal FoV, full-color, low-cost IDA waveguide lens was demonstrated at the Consumer Electronics Show (CES) in Las Vegas (January 2020). As shown in Figure 1, DigiLens’s current waveguide display range includes helmet (25° diagonal), smart glass (30° diagonal) and head-worn (50° diagonal) color waveguide displays.
Wide field of view color waveguide display reference designs for low-cost consumer AR displays using high index modulation photopolymer and liquid crystal material for providing compact wide-angle, displays are presented.
Waveguide technology for providing compact wide-angle, low-cost HUDs for partially autonomous road vehicles with scalability to meet future HUD requirements, extending beyond safety and vehicle informatics, to fully autonomous vehicles will be presented.
DigiLens Switchable Bragg Grating (SBG) waveguide technology for transportation AR HUD consumer products enables switchable, tunable and digitally reconfigurable color HUDs with a field of view, brightness and form factor surpassing those of competing technologies. DigiLens waveguide gratings are printed into a proprietary polymer and liquid crystal mixture that can provide any required combination of diffraction efficiency and angular bandwidth in a thin waveguide with high transparency and very low haze. DigiLens waveguides can be laminated to integrate multiple optical functions into a thin transparent device. Our current reference designs for dashboard mounted and wearable ARHUDs will be presented.
DigiLens’s Switchable Bragg Grating (SBG) waveguides enable switchable, tunable and digitally reconfigurable color waveguide displays with a field of view, brightness and form factor surpassing those of competing technologies. DigiLens waveguides can be laminated to integrate multiple optical functions into a thin transparent device. DigiLens waveguide gratings are printed into a proprietary polymer and liquid crystal mixture that can provide any required combination of diffraction efficiency and angular bandwidth in a thin waveguide with high transparency and very low haze. The waveguide combines two key components: an image generation module, essentially a pico projector, and a holographic waveguide for propagating and expanding the image vertically and horizontally. Color is provided by a stack of monochrome waveguides each capable of addressing the entire field of view, incorporating an input rolled K-vector grating, a fold grating, and an output grating. Rolling the K-vectors expands the effective angular bandwidth of the waveguide. Fold gratings enable two-dimensional beam expansion in a single waveguide layer, which translates into lower manufacturing cost, reduced haze, and improved image brightness. The design of these complex SBGs is complicated by their birefringent properties, taking the design of DigiLens waveguides well beyond the frontiers of established ray-tracing codes. Our paper summarizes the key features of DigiLens waveguide technology and discusses our optical design methodology, with examples from DigiLens’s current waveguide HUD products.