Retinal projection is a technology that uses the retina of your eye as a projection screen, sending light directly to your eye so you see a “screen” floating in space. It seems like it should be the future of virtual reality, so what happened?
Understanding Virtual Retinal Displays
All the flat panel displays you look at every day have a grid of pixels and then emit a backlight through that grid of pixels, or the pixels themselves emit light in the case of OLED displays.
Virtual Retinal Displays function more like the CRT (cathode ray tube) monitors and televisions of display days, where an image plot is drawn on the back of a phosphorescent screen. Except, in this case, the image is drawn directly onto the retina of the eye.
The end result is what appears to be a screen floating in space or an image that appears to be part of the scene.
Why do we want retinal projection?
Retinal projection has a number of advantages over current display technologies. While early retinal projection systems were bulky and heavy, modern systems use lightweight laser systems or modern LED technology to fire photons into the eyes.
Today’s VR headsets use one or more flat screens viewed through special lenses that precisely unscrew the distorted image on the LCD or OLED screen. This results in an image formed in such a way as to provide an immersive experience. Unfortunately, this design often results in visible pixel grids (the “chicken wire effect” or “screen door effect”) and somewhat blurry visuals.
In contrast, the resolution and sharpness of retinal projection images are exceptional. They don’t cause the same amount of eyestrain as OLED or LCD screens within an inch of your eye, thanks to the small amount of light needed.
Retinal projection systems also have optical advantages. This technology allows for on-the-fly optical correction, so you don’t have to worry about wearing glasses. You can also refocus to show near or far objects.
For virtual reality or mixed reality (MR) headsets, retinal projection systems have the potential to make sets much smaller and less power consuming. The holy grail of any type of VR or MR headset is to shrink it down to the size of sunglasses.
The limitations of retinal displays
There are some limitations to retinal projection that make it less than ideal as a replacement for current virtual reality systems. First, the field of view possible with the current retinal projection is too narrow for virtual reality. This means it’s not immersive enough to meet the standards of modern VR experiences.
Retinal displays use various approaches to project images onto the eye, including sophisticated arrays of micromirrors or lasers at precise angles. Tiny moving parts like these are inevitably more difficult to manufacture than solid-state systems like an OLED display. That complex hidden system creates many obstacles in the development process.
What happened to Avenger?
You may or may not know it, but there is actually a retinal projection technology headset that you can buy and own. In 2016, a company called Avegant released Avegant Glyph. The Glyph looks like a standard pair of headphones, but you can flip the headband over your eyes and enjoy a video stream projected onto your retinas. It didn’t look like virtual reality, but it was a 720p home theater system that you could take with you anywhere.
You can still buy a Glyph on Amazon, though it’s not likely to be new. On the Avegant site, however, you won’t find any mention of the Glyph as a product you can buy. Instead, Avegant sells “light engines” as components to other companies that want to develop wearable headphones. Even when the Glyph came out, reviewers were a bit lukewarm and it suffered from typical first-gen tech syndrome. If you read contemporary reviews of the Glyph, reviewers noted that the headset only had 720p, was heavy, difficult to set up initially, and overpriced for what it offers.
That said, Avegant is still around and working to push its technology forward, perhaps so that a partner company (like Facebook perhaps) can one day create a successful mainstream system. And while Avegant is the only company we know of that has released a commercial VRD product, many different players are investing in research and development to make VRD technology a reality.
In 2020, Bosch showed off smart glasses that use lasers to project images onto your retinas. QD Laser’s Viserium used retinal projection to help people with low vision see more clearly. Magic Leap is working on next-generation augmented reality, and the list of working companies involved with VRD technology has at least half a dozen more names to add.
Retinal projection could be the future of mixed reality
While the current retinal projection may not be the best for VR, it may have a future in MR applications. Devices like the Microsoft Hololens 2 incorporate laser-based retinal projection and don’t require large fields of view to be useful.
If retinal projection technology ever manages to achieve the same horizontal field of view as consumer VR headsets like the Quest 2, it could still end up being the sharpest, most realistic VR solution aside from connecting a computer directly to your visual cortex.
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