A group of Sweden-based researchers proposed a novel e-ink display solution that could make way for super compact, retina-level VR headsets and AR glasses in the future.
The News
Traditional emissive displays are shrinking, but they face physical limits; smaller pixels tend to emit less uniformly and provide less intense light, which is especially noticeable in near-eye applications like virtual and augmented reality headsets.
In a recent research paper published in Nature, a team of researchers presents what a “retinal e-ink display” which hopes to offer a new solution quite unlike displays seen in modern VR headsets today, which are increasingly adopting micro-OLEDs to reduce size and weight.
The paper was authored by researchers affiliated with Uppsala University, Umeå University, University of Gothenburg, and Chalmers University of Technology in Gothenburg: Ade Satria Saloka Santosa, Yu-Wei Chang, Andreas B. Dahlin, Lars Österlund, Giovanni Volpe, and Kunli Xiong.
While conventional e-paper has struggled to reach the resolution necessary for realistic, high-fidelity images, the team proposes a new form of e-paper featuring electrically tunable “metapixels” only about 560 nanometres wide.
This promises a pixel density of over 25,000 pixels per inch (PPI)—an order of magnitude denser than displays currently used in headsets like Samsung Galaxy XR or Apple Vision Pro. Those headsets have a PPI of around 4,000.
As the paper describes it, each metapixel is made from tungsten trioxide (WO₃) nanodisks that undergo a reversible insulator-to-metal transition when electrically reduced. This process dynamically changes the material’s refractive index and optical absorption, allowing nanoscale control of brightness and color contrast.
In effect, when lit by ambient light, the display can create bright, saturated colors far thinner than a human hair, as well as deep blacks with reported optical contrast ratios around 50%—a reflective equivalent of high-dynamic range (HDR).
And the team says it could be useful in both AR and VR displays. The figure below shows a conceptual optical stack for both applications, with Figure A representing a VR display, and Figure B showing an AR display.
Still, there are some noted drawbacks. Beyond sheer resolution, the display delivers full-color video at “more than 25 Hz,” which is significantly lower than what VR users need for comfortable viewing. In addition to a relatively low refresh rate, researchers note the retina e-paper requires further optimization in color gamut, operational stability and lifetime.
“Lowering the operating voltage and exploring alternative electrolytes represent promising engineering routes to extend device durability and reduce energy consumption,” the paper explains. “Moreover, its ultra-high resolution also necessitates the development of ultra-high-resolution TFT arrays for independent pixel control, which will enable fully addressable, large-area displays and is therefore a critical direction for future research and technological development.”
And while the e-paper display itself is remarkably low-powered, packing in the graphical compute to put those metapixels to work will also be a challenge. It’s a good problem to have, but a problem none the less.
My Take
At least as the paper describes it, the underlying tech could produce XR displays approaching the size and pixel density that we’ve never seen before. And reaching the limits of human visual perception is one of those holy grail moments I’ve been waiting for.
Getting that refresh rate up well beyond 25 Hz is going to be extremely important though. As the paper describes it, 25 Hz is good for video playback, but driving an immersive VR environment requires at least 60 Hz refresh to be minimally comfortable. 72 Hz is better, and 90 Hz is the standard nowadays.
I’m also curious to see the e-paper display stacked up against lower resolution micro-OLED contemporaries, if only to see how that proposed ambient lighting can achieve HDR. I have a hard time wrapping my head around it. Essentially, the display’s metapixels absorb and scatter ambient light, much like Vantablack does—probably something that needs to be truly seen in person to be believed.
Healthy skepticism aside, I find it truly amazing we’ve even arrived at the conversation in the first place: we’re at the point where XR displays could recreate reality, at least as far as your eyes are concerned.
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