Star Trek’s Geordi LaForge made wearing a hair barrette look cool, but a key reason Google Glass never took off with consumers was because the augmented reality (AR) headset’s design wasn’t socially acceptable – wearers risked looking like a “glasshole.”

Achieving a sleek appearance for true AR glasses is the biggest barrier to widespread AR headset adoption. A recent report by IDTechEx, “Optics for Virtual, Augmented and Mixed Reality 2022-2032: Technologies, Players and Markets,” outlines the technologies that could make AR headsets ubiquitous by creating a socially acceptable form factor.

IDTechEx defines VR as being closed to the real world, replacing reality with a completely new 3D digital environment, while AR is open to the real world, overlaying digital content on top of it. AR might also include mixed reality (MR); it’s open to the real world but adds superimposed digital content that superficially interacts with the environment in real-time.

“Mixed reality is a bit contentious,” said Sam Dale, IDTechEx technology analyst and author of the report. “No one seems to agree on a definition, but it basically refers to augmented reality devices where you’ve got…a lot higher level of immersion.” An increasingly popular catchall definition is “extended reality” or “XR,” he said in an interview.

In some ways, VR headset optical architecture is simpler. The challenge with AR is the technology required to overlay the superimposed digital content – an optical combiner/waveguide is a critical component that takes a projected image and overlays it on top of reality. Dale said it could be as simple as a slanted semi-silver mirror or something incredibly more complicated. “And you sometimes need some sort of lenses in between.”

No matter the lens requirement, the main challenge is a creating a solution that’s affordable and doesn’t make the headset unwieldy – this remains a barrier to making AR socially acceptable in public.

Headset makers must balance many tradeoffs

It’s difficult for AR glasses not to be bulky, due to the many components necessary if a headset is to have an integrated display – these displays along with bulkier batteries and other components take up more space.

Optical combiners are required to overlay projected images onto reality, and that’s where the biggest roadblock remains, Dale said. Optical waveguides have the potential to aid in the design of AR headsets so they may conform more closely to existing eyewear. As broadly defined, optical waveguides bend and combine different frequencies of light to direct it into the eye and create the virtual images seen by the wearer that are overlaid on the environment.

But waveguides still have hardware hurdles to overcome, he said, the biggest being poor light efficiency – the more inefficient the waveguide, the brighter display required, and hence, larger batteries. The resulting bulkiness simply isn’t socially acceptable. Dale said one solution is to swap out the diffractive optical elements used in most commercial AR waveguides such as those used in Microsoft’s HoloLens 2 for reflective optics – this results in approximately a tenfold increase in light efficiency for comparable waveguide specifications.

There are tradeoffs, however, as reflective waveguides currently must be made with more traditional optical manufacturing techniques if they are to be cost effective, and optical combiners already form one of the most expensive components of AR headsets. Keeping costs down is critical for AR headset ubiquity. “There are some major issues that are left to solve versus lenses for VR devices,” Dale said.

Waveguide technology most promising solution

No matter who comes with the optimum AR headset that’s ready for the masses, the optical challenges are the biggest limiter that must be overcome. It’s a technological bottleneck that involves solving for size, power, and heat and greatly affects the usability of the device, Dale said. “You need to be able to use it for long periods of time without it getting hot on your head.”

He said waveguides are only now becoming feasible but not yet at a mass market level, but ultimately, optics are key for ubiquitous XR because headset design is a function of optical architecture and image quality is the number one factor in XR immersion. It’s not that there’s a shortage of technology options; emerging optical technologies have the potential to improve the utility of XR devices, but for AR/MR headsets, optics are often too expensive for the mass market. IDTechEx has segmented a huge range of AR image optics technologies into two major categories, including optical combiners, where there’s two major sub-categories: waveguide combiners and non-waveguide combiners.

Dale said waveguide combiners come out on top because they can be made to look like glasses lenses, enable a wide field of view, and most of all, enable socially acceptable and immersive AR/MR. But within that category, there are different options. The current market leading option is a diffractive waveguide that uses surface relief gratings for incoupling and outcoupling, which can be found in Microsoft Hololens products based on IP from Nokia.

Among the companies working on this technology are Snap Inc., which acquired WaveOptics last year. WaveOptics sees an optical engine composed of waveguides and projectors as the key to enabling successful AR smartglasses and headsets. Its core technology, which it refers to as the as the waveguide or waveguide stack, include a projector coupled to a diffractive waveguide combiner.

A challenger to surface relief gratings is another diffractive waveguide technology: holographic gratings are garnering big interest and investment, Dale said. They combine a planar waveguide between holographic elements and are used in Sony SED-100 Smart Glasses.

Meanwhile, reflective/geometric waveguides are making big strides and getting more interest, he said. They employ prism or mirror incoupling with transflective surfaces to deliver an outcoupled image to the pupil. Used in Lenovo’s ThinkReality A6, companies that are developing this technology include Optinvent and Lumus.

Similar to WaveOptics, Lumus’ reflective waveguide-based optical engines consist of a micro projector and a reflective waveguide. The micro projector generates and projects the image into the entrance aperture of our waveguide combiner. The projector itself is comprised of a micro-display that generates the virtual image and a collimating optics module that collimates (or accurately aligns) the image toward the waveguide’s entrance aperture. The waveguide performs pupil expansion in both “X” and “Y” dimensions and projects the image towards the user’s eye.

Ubiquitous AR is years away

Even with all waveguide technologies available, Dale said the market is still in its early stages despite AR devices being on sale for more than a decade. One impetus for solving the AR lens issue is the push by Meta to move people into the VR/AR direction, which is why Facebook acquired Imagine Optix in 2021.

To date, there’s been some modest enterprise adoption of AR headsets – someone monitoring a factory floor from a control room, for example. Even the maligned Google Glass has seen some success in big companies over the years, he said, while there are rumors Apple is bringing out its own AR headset solution. “It’s sort of like nuclear fusion; it’s always sort of just around the corner,” he said.

No matter the technology used to create a socially acceptable headset, it needs to be cost-effective – we’re likely a decade away from ubiquitous consumer AR. IDTechEx expects easy to manufacture plastic reflective and holographic waveguides to capture market share in durable, low-cost consumer devices by 2032.

According to research firm Statista, consumer and enterprise AR glassware revenue was US$3.6 billion in 2022, with the AR hardware market growing at a rate of 126.2%. It noted that the current retail price for a Microsoft HoloLens 2 is $3,500.

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