Bringing it All Together

Image courtesy Facebook

So, we learned about folded optics and we learned about holographic lenses. And now the phrase ‘folded holographic optics’ hopefully sounds a bit less like technical mumbo-jumbo.

The whole goal of this approach is to enable truly glasses-sized VR displays. Even in this proof-of-concept stage, the researchers have already demonstrated a headset equipped with such displays that could really be called ‘glassed-sized’ even more fairly than ‘goggles’. And they say it achieves the “resolution and FOV of a modern VR headset.”

Image courtesy Facebook

It’s important to note though that the sleek headset pictured does not include critical components necessary for a real product. In order to focus squarely on the heart of their research (the optics), they left out things that would normally be inside the headset, like the light source (laser in this case), driving electronics, tracking cameras, etc. Among the design’s limitations, the researchers “acknowledge size reduction challenges when integrating light sources into the glasses, as current laser modules tend to be larger than commonly used LED sources.”

With further R&D, the researchers say, folded holographic optics could be a practical approach to making compact VR headsets that offer a wide field of view, very large color gamut, and perhaps even retinal resolution.

Which makes us wonder…

When Will We See This Technology in a Headset?

Image courtesy Facebook

My guess is not for another 10 years at least. Although the research demonstrates some really compelling possibilities, there’s still much work to be done before this technology leaves the labs. As such, the researchers explored the limitations of their present design.

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First, they have yet to demonstrate a full-color version of their work in the glasses-sized form-factor (though they did demonstrate full-color in a proof-of-concept that was not head-worn).

The complete VR display, lens, screen, and all. | Image courtesy Facebook

Another issue is the eye-box of the optics (the volume of space where your eye can actually see the image). The proof-of-concept demonstration had an eye-box of 8 mm, but it will need at least 10–12 mm to make a “practical [stereoscopic] headset,” the researchers say.

Further, the researchers note that while the technology is likely to support retina resolution, much higher resolution displays will still need to become widely available. That and a calibration protocol will need to be developed to improve “geometric uniformity, intensity uniformity, color uniformity, and color alignment.”

And then there’s the whole matter of being able to build the rest of the components into such a small form factor. The researchers envision a standalone Quest-like VR headset with everything on-board for the complete VR experience with no tether.

“Our prototypes were monoscopic and used external light sources and display drivers. A truly portable and practical display would integrate a pair of display modules, a computing platform, batteries, positional trackers, and all external components into a sunglasses-like frame.”

So it’s going to be a while before this tech makes it out of the lab, and that’s only if a better solution isn’t found by then. Still, this is a very exciting proof-of-concept, primarily because of the combination of form-factor, resolution, field of view, and color gamut.

If you really want to take a technical deep dive, check out the full research paper titled Holographic Optics for Thin and Lightweight Virtual Reality.

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  • VRagoso

    Cool explanation guys. Well done.

  • Ad

    Just by the tone I could tell this was Ben. Talking about this as speculative tech is the right way to go, I don’t think there’s much point hoping for the next generation of headsets to be like this. Comfort isn’t necessarily about form factor. A Vive or Quest is night and day compared to an index not because they’re the wrong form factor but because weight is distributed wrong, the straps are not nearly good enough, and they try to be as compact as possible even though they just shoved everything towards your face. The “google” prototypes last year were like this. They clearly should have had straps but they didn’t just because they wanted them to look like glasses. And it seems like that just made them really expensive and uncomfortable, but giving off the impression of being a huge step forward even though the displays were pretty bad as a resulting of the folding method they used.

  • Rudl Za Vedno

    Holographic Optics??? Corteks leaked that NVIDIA’s coming out with ultra high res 4 panel (2×2 displays like Varjo) HMD with Holographic technology and eye tracking with dynamic foveated rendering when It releases RTX Ampere GPUs. I was LMAO discarding leak immediately, but damn, now I’m not so sure it isn’t true.

  • Andrew Jakobs

    Sounds cool, but especially what they say So it’s going to be a while before this tech makes it out of the lab, and that’s only if a better solution isn’t found by then.
    I think something like directly projecting the image onto your retina will probably be out before this (as it’s already being shown), and that doesn’t require lenses.
    Personally I don’t care if the headset isn’t as small as a regular pair of sunglasses, as I want to have a set that blocks out all light.

  • Foreign Devil

    I was reading recently about another nano technology making VR lens out of “metaloids” rather than glass. Anyways it was some sort of nano-material and actually looked to be more provmising aas soon as they can find a way to sale up production .

  • Lucidfeuer

    So how is this different from Nvidia’s Lightfield glasses from a few years back?

    • kontis

      It’s in the paper:

      Near-eye light field displays. An alternative method to create a thin virtual reality display is to synthesize a light field near the eye. Lanman and Luebke [2013] show how a microlens array placed over a display panel can create the focal depth cues and has produced the thinnest VR display known to date at 10 mm thick. With fur- ther engineering, designs could also likely be made significantly thinner. Although highly innovative, the display sacrifices signif- icant spatial resolution to generate the light field, and published prototypes [Huang and Hua 2018; Lanman and Luebke 2013] have preserved <10% of the resolution of the underlying display panel. The theoretical maximum resolution of the display is also limited by the aperture diffraction of the microlenses. An alternative design, Pinlight Displays [Maimone et al. 2014], creates an image without lenses using a structured backlight consisting of point light sources. The design preserves much of the resolution of the underlying dis- play panel, but has a very low diffraction limited resolution. In contrast to these light field designs, the proposed design is capable of preserving the full resolution of the display panel and has been demonstrated in slightly thinner form factors. Our optical design does not have a practical diffraction limit on resolution and we demonstrate that it scales to the limit of normal human vision. How- ever, unlike light field displays, we will require additional hardware to support the focal depth cues

      • Lucidfeuer

        Thanks, but I see it doesn’t explain how THEIR solution is different if they don’t use microlenses or pinholes?

    • benz145

      Great question. While the reply from @kontis:disqus explains the difference from a pros/cons standpoint, I’ll try to explain from a technological standpoint.

      Although this Facebook research involves holograms, it is not a light-field display because the viewable output is not a light-field. The display/optics pipeline in the Facebook prototype is functionally identical to what’s in today’s consumer headsets, but it uses a novel approach (which involves holography) to make the whole thing much more compact.

      A light-field display is a class of displays which output a light-field in real-time. There are several methods to create light-fields; the NVIDIA prototype you’re referring to uses a microlens array. The primary benefit of light-field is that they present light to our eyes in the same way that we see the real world.

      That means that light-field displays inherently support ‘accommodation’ (focusing of the light by the lens in your eye), depth-of-field (blurring of objects outside of your focal distance), and per-eye parallax (subtle changes in the view depending on the position of your eye relative to the virtual object). None of today’s VR headsets support these features because they don’t quite correctly model the virtual light as if it was coming from the real world.

      Back to Facebook’s prototype and its use of holograms. Although a hologram is a captured light-field, the hologram as used in the prototype headset is actually a hologram of a traditional lens. The purpose of doing this was to reduce the bulk of the optics from relatively large lenses down to paper-thin films. It was achieved by capturing the light-bending properties of a traditional lens onto a holographic sheet, and then placing that sheet where the real lens would normally be placed in the optical pipeline.

      So the hologram takes the place of a normal lens (only much thinner) in Facebook’s prototype. And just like a normal display/lens setup in today’s VR headsets, the output is a ‘flat’ image which is made stereoscopic by rendering a different view for each eye.

      Please let me know if this made any sense!

      • Lucidfeuer

        “Hologram of a traditional lens” my mind is blown. It’s so smart, but I’m not sure to understand: this prototype, just displays one fixed image through a screen, and the paper-thin lens is a “pre-rendered optical diffraction” of that same image? Which means you’d need one different paper for each image (although I can image the idea is to make it a mecanical/digital one) if I understood well?

        • benz145

          The headset shows rendered imagery just like VR headsets today. I think I see your confusion.

          A hologram as most of us known them are the weirdly colored ‘3D photos’ that you can view on a piece of holographic film. These are captures of a specific scene (a hologram is effectively a recording of the light from that scene).

          The hologram used in the Facebook prototype is a recording of how light interacts with a lens (lenses bend light). So instead of recording a scene in the hologram, they recorded a lens.

          The lens is not the display, it’s just the part that bends the light from the display so that it is focused.

          The display itself in these headsets is a fairly typical LCD. The thing that makes the headset so much thinner than normal headsets is purely the novel optics.

          • Lucidfeuer

            Ok thanks, I get the “concept” though I’m still not sure how they “recorded” or reproduced the light bending properties of a lenses unless they simply have micro-lenses arrays like in a typical lightfield display (without the need for multiple viewpoint rendering), like what the actual “holographic lens” is made of…

  • mfx

    Dream news

  • lieisacake

    Still going through the paper, but so far one thing is worth noting:
    “Speckle reducers” are actually very truthfully named, they reduce laser speckle, but don’t eliminate it. For anyone who doesn’t know what laser speckle is, it’s like an extremely fine grain mura effect. I’ve had a chance to see them in action in a video projection system. The speckle reducers make the grains less fine and more blurry but are far from eliminated and reducers have drawbacks too, like making the speckle appear to “swim” on the image. It’s a pretty “in-your-face” artifact, would be less noticeable on an AR headset but not sure VR users will tolerate it very well.

  • Miqa

    It wasn’t touched upon in the article. Is this display technology varifocal? To me that seems more important than form factor.

    • wheeler

      Options for complementing this design with varifocal are mentioned in the paper

      • Miqa

        Cool, thanks

    • kontis

      No, it’s not.
      They suggest using mechanical solutions…

  • Jonathan Winters III

    Ummm…..yeah. VR glasses that don’t block out the outside world are absolutely useless for VR gaming. For AR, it’s ok, but VR, no.

    • Octo

      Did you just look at the top image and go straight to commenting? There is also an image of them capped off. Maybe the top image was for showing off the lenses..whatever, you’re jumping to conclusions for no good reason.

  • wait wait wait… virtual lenses? Virtual lenses. Virtual…. lenses? They make lenses virtual now? wait, waht?

    my mind cannot compute.

    • duck

      If its true , the holographic lenses can even be used in place of spectacles.

  • brubble

    Wow, very interesting!

  • As soon as I see these polarized reflective techniques it reminds me of the issues faced with the waveguides in the Hololens/Magic Leap. The devil will be in the details when it comes to colour convergence, brightness, resolution, etc.

  • duck

    Wow wow wow
    A big thumbs up
    This is revolution in optics
    Holographic lens + Polarization + rest of tech == The real thingy, what all want w/o a box on your face.
    Great job

  • duck

    If its true , the holographic lenses can even be used in place of spectacles by designing all parameters digitally, diopter settings, cylindrical aspect etc compute the holographic lens then print it on a thin sheet of glass/perspex/plastic. Hologram may even be stored on a pendrive so that the process can be repeated in case of damage. Finally specs wearers can have designer glasses.
    Great business opportunity that will overturn the optical lenses/spectacles industry upside down.

  • blue5peed

    I can’t stop laughing at how insane this sounds. Its like someone smoked a bowl and said “fu*k it lets just use holograms”.

  • Fascinating. And thanks for the explanation, it was better than the one provided by facebook. Regarding the timing, Jeri Ellsworth says that she expect this technology to be used “soon-ish”, so probably is more 5 years than not 10

    • Rogue Transfer

      Highly unlikely, if you look at the speckle grain and mura over the two prototypes’ images. It’s never going to be refined to an acceptable level in just 5 years.

      Just look how slow they’ve been to develop other, less optically challenging tech and this is a whole new ball game with a number of fundamental, unsolved issues. Not to mention they only managed 69° vertical FOV and less than that stereo-overlap(since they are widely-spaced, square views).

  • Chaven Yenketswamy

    If you can achieve retinal resolution then this technology also has the potential to be used for corrective eyeware and a whole assortment of optical consumer products.

  • MadMax1998

    The article sounds like science fiction… lasers as a light source? Why don’t we use LEDs as we do now? What is a “holographic film” and how do you “capture” a hologram onto it? AFAIK, holograms right now can only be displayed by a “slotted” display that shows different angles of an image per slot, which is crude and low-res.

  • Rogue Transfer

    “In order to focus squarely on the heart of their research (the optics), they left out things that would normally be inside the headset, like the light source (laser in this case), driving electronics, tracking cameras, etc.”

    So, they misrepresent the actual thickness necessary, by omitting the laser source, and show a publicity picture of some dummy black glasses that can’t display anything without it. Makes you wonder why they didn’t/couldn’t attach the laser light source for the press photos.

    • benz145

      Why shrink a laser light source if there isn’t first a reason? This research shows a good reason for future research to focus on shrinking a laser light source.

  • Kim from Texas

    They make eye glasses using this same technology. I tried these glasses and they failed miserable since they made me nauseous.

  • Bob

    The bit after you said ‘Now I’m going to blow your mind’ actually blew my mind.

  • allen mchey

    It is place ugly. I would refuse to buy it. I am so surprised at these amazing companies and their vision of technology is hijacked by few engineers that lack the focus for high end design. With all that Jazz, good and bad reviews. I do understand the build process and technology but this piece of glass is still way worse than magic leap (I am not a magic leap fan, I only helped to manufacture it).

  • dk

    sooo to make this work they have a light field display
    92◦×69◦ fov and good angular resolution ….hmmm interesting