Introduction to Augmented Reality Displays
One of probably the most attractive ways to create an augmented reality image is to have a skinny, transparent waveguide in front of the attention that may display the specified images or symbols. This technology is getting used by corporations corresponding to Vuzix and Microsoft, who’ve developed their very own versions of augmented reality eyewear. However, one other company, DigiLens Inc., has developed a distinct approach that provides several advantages over the standard technology.
How Waveguides Work
Waveguides are commonly used today as LCD backlights. They work by injecting LED light into the waveguide, which then bounces around via total internal reflection (TIR) and is extracted to create a uniform illumination source. However, with augmented reality eyewear, the goal is to inject and extract an RGB image, which is a way more complex problem to unravel.
Surface Relief Grating (SRG) Technology
The SRG approach was originated in Nokia’s Research Labs about 10 years ago. This technology uses a series of nanometer-scale structures to extract a full-color image from the waveguide and supply some lensing to create a virtual image. The patterns have to be holographically defined after which etched into the glass waveguide. While this technology works well, it has some limitations, corresponding to a limited field of view and lower efficiency.
Switchable Bragg Grating (SBG) Technology
DigiLens has developed a distinct approach based on gratings made from liquid crystal photopolymers. These are patterned into more complex optical elements that may also be turned on and off. The company calls them Switchable Bragg Gratings (SBG). This technology offers several advantages over SRG, including thinner waveguides, wider field of view, higher efficiency, and switchability.
Benefits of SBG Technology
The SBG technology has several benefits over SRG. For example, the sector of view of an SBG element is about 40 degrees for color applications and as much as 60 degrees for night vision monochrome applications, which is double what is feasible with SRG technology. Additionally, SBG’s have nearly 98% efficiency, which suggests a brighter display and fewer power consumption. The ability to modify optical cores on and off can be a big advantage, because it may very well be used to vary the focal length of the virtual display or integrate eye tracking.
Design and Manufacturing
DigiLens has created plug-ins for common optical design tools like Zemax to model SBG elements. This makes it easier for patrons to design the answer they need and quickly prototype it. The IP cores are mastered using a special holographic exposure technique, and once done, inexpensive copies will be replicated with very high yield and only a 0.1% loss in performance.
Comparison to SRG Technology
In contrast, the SRG approach being pursued by Microsoft and Vuzix has some limitations. As the surface relief nano features decrease in size and increase in complexity, the associated fee and yield of duplicating parts greatly reduce quality when it comes to haze, which severely impacts display contrast. The only alternative for SRG developers is to uniquely etch the parts individually, using silicon wafer tools, which is a costlier and complicated process.
Conclusion
With the maturation of waveguide-based imaging systems using each surface relief gratings and switchable Bragg gratings, it seems likely that an entire recent class of display capability is destined to roll out in business, skilled, and consumer markets in the subsequent few years. The SBG technology offers several advantages over traditional SRG technology, including wider field of view, higher efficiency, and switchability. As this technology continues to develop, we will expect to see more advanced and complicated augmented reality displays that can change the best way we interact with information and one another.
