For all the advancements in virtual reality technology in recent years, one major factor still holding the space back is the size and relative discomfort of current headset design. Even the most compact and comfortable VR headsets today still resemble something like a cross between ski goggles and a motorcycle helmet, requiring massive headstraps to secure a heavy display that protrudes multiple inches away from the face.
Now, researchers at Facebook Reality Labs are using holographic film to create a prototype VR display that looks less like ski goggles and more like lightweight sunglasses. With a total thickness less than 9mm and without significant compromises on field of view or resolution these displays could one day make today’s bulky VR headset designs completely obsolete.
Holographic Optics for Thin and Lightweight Virtual Reality Researchers, Andrew Maimone and Junren Wang detail the optics behind their lightweight prototype. The key to the thinness is a series of flat, polarized films that use a “pancake optics” light-folding technique to reflect the displayed image multiple times in a small space.
That design effectively extends the apparent focal length of the image (which is key to user-eye comfort) without the need for a large physical space for the light to travel through.
Holographic films used to focus the image onto the eye also eliminate the need for the kinds of bulky refractive lensing systems found in current headsets.
Despite the thinness, the prototype display is able to provide a roughly 90-degree horizontal field of view in testing. That’s a big improvement over thin-film AR displays like Microsoft Hololens or Magic Leap and it’s comparable to VR headsets like the Oculus Rift and Quest (but less than higher-end headsets like the HTC Vive and Valve Index).
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