Facebook presents sunglasses-like VR display prototype
Image credit: Facebook Research Labs
Facebook’s Reality Labs has presented a proof-of-concept VR display with a sunglasses-like form factor. Engineers used holographic films and optical folding in order to make the device as slim as possible.
VR headsets tend to be bulky and too heavy to wear comfortably for hours on end, due to large lens systems for displaying media. Although tech companies have been developing smaller VR and mixed-reality wearable displays for many years (e.g.: Google Glass and Microsoft HoloLens), no products have yet attracted significant consumer interest.
Last year, Facebook presented slimmer variants of its “Half Dome” VR headset, which achieved significant reductions in the size of the optical module by folding the optical path into a very small space and using an electronically controlled lens array to cycle through 64 discrete focus planes.
Now, Facebook’s Reality Labs (formerly Oculus Research) have presented an even more compact proof-of-concept VR headset which appear closer to ordinary sunglasses than conventional VR headsets. The displays are less than 9mm thick: around the thickness of a modern smartphone. While the Oculus Quest weighs 571g, this prototype reportedly weighs less than 18g.
The displays were compacted through a technique described in a Siggraph 2020 paper called “Holographic Optics for Thin and Lightweight Virtual Reality”.
According to Facebook Reality Labs, this involves two techniques: holographic optics and polarisation-based optical folding. While most VR displays use a simple refractive lens composed of a thick, curved piece of glass or plastic, this proof-of-concept device replaces this with holographic optics, bending the light like a lens but looks like a very thin sticker-like film. By applying polarisation-based optical folding (forcing light to move forwards and backwards), they collapsed the space required to focus the image to a fraction of the volume that would otherwise be required.
The researchers said that this design would also deliver a visual upgrade, with potential for a wider colour range and resolution reaching “the limit of human vision” with visible pixels eliminated. The field of view should be comparable to existing headsets, they said.
Despite its promise, the device is a long way from commercial availability. The prototype device only displays images in green, with engineers working on either supporting a full-colour holographic directional backlight or constructing a full-colour polarisation volume hologram lens. The Siggraph paper also reports issues such as ghost images and laser speckle, as well as laying out future challenges such as systems integration.
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