Facebook just revealed a holographic optical architecture for a future VR headset that will be both thinner and lighter, replacing the current bulkier glasses and headsets. The technology, described in “Holographic Optics for Thin and Lightweight Virtual Reality,” a Siggraph 2020 research paper, uses a “pancake optics” design that combines layers of holographic film with a laser projection system and directional backlights. The results can be either flat imagery or volumetric holograms.

VentureBeat reports that, “depending on how many color, lighting, and alignment-enhancing components a prototype contains, the thickness of the optical system can range from 11mm to just under 9mm … [and] in wearable prototype form, each eye display features a resolution of roughly 1,200 by 1,600 pixels.”

That resolution is “comparable to current VR goggles” and offers a “field of view that’s either a 93-degree circle or a 92-by-69-degree rectangle … roughly comparable to the display specs of a 571-gram Oculus Quest.” The difference is that the new glasses would weigh less than 10 grams, “albeit with only a single eye display in the prototypes.”

According to researchers, “they could cut parts and change materials to achieve a 6.6 gram weight equivalent to plastic aviator sunglasses, but would compromise performance by doing so.”

Facebook now has three prototypes, two wearables and a full-color one that’s still on a test bench. All of them rely on laser LCD illumination systems. The color prototype relies on three lasers and “exhibits shimmering speckles, requiring a despeckler that’s fine for static images but leaves color noise when displaying dynamic content.” In other words, all of the prototypes are early stage.

With regard to full color, researchers say they could create another prototype “by adding either a holographic backlight or lens but need more engineering work to get to that point.”

The proposed holographic system would still require processors and storage, which could be inside the display device or “wirelessly offloaded to a separate housing.” Facebook’s glasses-style prototypes “have most of their components mounted outside of the displays, which means their real-world implementation would be closer to Nreal’s Light AR glasses than Oculus Quest.”

Facebook’s ultimate goal is to “deliver both resolution matching normal human vision and a large viewing eye box so that eyes can rotate to see content rather than just staring forward at a small window.”

Nreal’s Light, scheduled to be released this year, “weighs 88 grams and has a 52-degree field of view.” Other companies working on holographic solutions are Akonia, purchased by Apple, which is seeking to “patent a retinal hologram projector system among other XR display technologies,” and U.K. startup WaveOptics supported by China’s Goertek.

DigiLens’ thin film holographic waveguide display is under consideration by both Samsung and Sony. In Germany, “Fraunhofer has developed microdisplays that are much smaller than traditional VR screens and can be brought closer to the user’s eyes, reducing the optical system’s volume by 75 percent and weight by 50 percent.”

For more information, visit the Facebook Research blog.