Display manufacturer Kopin recently demonstrated its latest VR display and pancake optic which promises higher resolution and more affordability for future VR headsets.

Most modern VR headsets take on the ‘box on your face’ form-factor because of a simple display architecture which necessitates a certain distance between the display and the lens. In the effort to make VR headsets more compact in the near-term, so-called ‘pancake optics’ are emerging as a leading candidate. These more complex optics reduce the distance required between the display and the lens.

Why Are Today’s Headsets So Big?

Photo by Road to VR

It’s natural to wonder why even the latest VR headsets are essentially just as bulky as the first generation launched back in 2016. The answer is simple: optics. Unfortunately the solution is not so simple.

Every consumer VR headset on the market uses effectively the same optical pipeline: a macro display behind a simple lens. The lens is there to focus the light from the display into your eye. But in order for that to happen the lens needs to be a few inches from the display, otherwise it doesn’t have enough focusing power to focus the light into your eye.

That necessary distance between the display and the lens is the reason why every headset out there looks like a box on your face. The approach is still used today because the lenses and the displays are known quantities; they’re cheap & simple, and although bulky, they achieve a wide field-of-view and high resolution.

Many solutions have been proposed for making VR headsets smaller, and just about all of them include the use of novel displays and lenses.

Pancake Optics (AKA Folded Optics)

What are pancake optics? It’s not quite what it sounds like, but once you understand it, you’d be hard pressed to come up with a better name.

While the simple lenses in today’s VR headsets must be a certain distance from the display in order to focus the light into your eye, the concept of pancake optics proposes ‘folding’ that distance over on itself, such that the light still traverses the same distance necessary for focusing, but its path is folded into a more compact area.

You can think of it like a piece of paper with an arbitrary length. When you fold the paper in half, the paper itself is still just as long as when you started, but its length occupies less space because you folded it over on itself.

But how the hell do you do that with light? Polarization is the key.

Image courtesy Proof of Concept Engineering

It turns out that beams of light have an ‘orientation’ which is referred to as polarization. Normally the orientation of light beams are random, but you can use a polarizer to only let light of a specific orientation pass through. You can think of a polarizer like the coin-slot on a vending machine: it will only accept coins in one orientation.

Using polarization, it’s possible to bounce light back and forth multiple times along an optical path before eventually letting it out and into the wearer’s eye. This approach, known as pancake or folded optics, allows the lens and the display to move much closer together, resulting in a more compact headset.

Kopin is an electronics manufacturer best known for its microdisplays. In recent years the company has been eyeing the emerging XR industry as a viable market for their wares. To that end, the company has been steady at work creating VR displays and optics that it hopes headset makers will want to snatch up.

At AWE 2022 last month, the company demonstrated its latest work on that front with a new plastic pancake optic and flagship VR display.

Kopin’s P95 pancake optic has just a 17mm distance between the display and lens, along with a 95° field-of-view. Furthermore, it differentiates itself as being an all-plastic optic, which makes it cheaper, lighter, more durable, and more flexible than comparable glass optics. The company says its secret sauce is being able to make plastic pancake optics that are as optically performant as their glass counterparts.

Photo by Road to VR

At AWE, I got to peak through the Kopin P95 optic. Inside I saw a sharp image with seemingly quite good edge-to-edge clarity. It’s tough to formulate a firm assessment of how it compares to contemporary headsets as my understanding is that the test pattern being shown had no geometric or color corrections, nor was it calibrated for the numbers shown.

You’ll notice that the P95 is a non-Fresnel optic which should mean it won’t suffer from the kind of ‘god-rays’ and glare that almost every contemporary VR headset exhibits. Granted, without seeing dynamic content it’s tough to know whether or not the multi-element pancake optic introduces any of its own visual artifacts.

Even though the test pattern wasn’t calibrated, it does reveal the retina resolution of the underlying display—Kopin’s flagship ‘Lightning’ display for VR devices.

Photo by Road to VR

This little beauty is a 1.3″ OLED display with a 2,560 × 2,560 resolution running up to 120Hz. Kopin says the display has 10-bit color, making viable for HDR.

Photo by Road to VR

Combined, the P95 pancake optic and the Lightning display appear to make a viable, retina resolution, compact display architecture for VR headsets. But it isn’t necessarily a shoe-in.

For one, the 95° field-of-view is just barely meeting par. Ostensibly Kopin will need to grow its 1.3″ Lighting display larger if it wants to meet or exceed what’s offered in today’s VR headsets.

Further, the company wasn’t prepared to divulge any info on the brightness of the display or the efficiency of the pancake lens—both of which are key factors for use in VR headsets.

Because pancake lenses use polarized light and bounce that light around a few times, they always end up being less efficient—meaning more brightness on the input to get the same level of brightness output. That typically means more heat and more power consumption, adding to the tradeoffs that would be required if building a headset with this display architecture.

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Kopin has been touting its displays and optics as a solution for VR headsets for several years at this point, but at least in the consumer & enterprise space they don’t appear to have found any traction just yet. It’s not entirely clear what’s holding the company back from break into the VR space, but it likely comes down to the price or the performance of the offerings.

That said, Kopin has been steadily moving toward the form-factor, resolution, and field-of-view the VR industry has been hoping for, so perhaps the P95 optic and latest Lightning display will be the point at which the company starts turning heads in the VR space.

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  • Max-Dmg

    I want pancakes now.

    • Keopsys

      We all do, but all we get in the VR is teasing and nothing real.

      • Max-Dmg

        I’m going to cook some in the morning.

      • kontis

        There are already HMDs on the market with pancakes.

    • dk

      delicious

  • Chaven Yenketswamy

    Nice to see more businesses in that market.

  • Vlad

    Apparently that amazing Kopin module (OLED+optics) is supposed to be in Meganex glasses (from Shiftall/Panasonic) … unfortunately their release has been delayed till the end of this year.

    • Cless

      It is! They confirmed they still use them in theirs just a couple days ago in a Japanese video. They are still saying that the want to sell it for around 100.000JPY (tax included), so that sounds amazing really.
      They’ll make an event here in Japan after CES so I’ll try to go and check them out in person then! :D

  • Cless

    Wait, isn’t that size of display way too small? Won’t the magnification be an issue?

  • logi43212

    You used the term “retina resolution” twice to describe this. This isn’t retina resolution.

    • Charles

      Not retina-limit resolution, but more like viewing a 900p screen from a normal viewing distance.

      • logi43212

        More like 360p, maybe 480p tops.

        • ZeePee

          Yet most people say the Reverb G2 is akin to 1080p monitor quality in experience.

          Technically you may be right, but in experience it feels like the equivalent of HD.

        • Charles

          It depends on how close to the equivalent display you’re sitting, but I think my assessment is about right for “as close as you can comfortably use it”.

          For that distance, for a typical-FOV headset, I think a good approximation is 1/3 the vertical resolution.

          2560/3 is 853 vertical lines. Then, to account for the fact that the FOV is a bit smaller on this headset, I rounded up to 900p.

    • Even Glemmestad

      Agreed. At 95 deg FOV and 2560 pixels, that would work out to 27 PPD, which is higher than the Quest 2’s 20.5 PPD, and lower than the Varjo Aero at 35 PPD. “Retina” in VR is generally acccepted at 60+ PPD, like the Varjo XR3 at 70+ PPD.

  • logi43212

    The video shows clear color shift from side to side. Instead of white you see yellow that switches to pink hue. Typical for a reflective polarizer.

    Plastic lenses produce awful lot more scattering than glass, which makes pancake ghosting even worse. I don’t think they have found a workaround for that.

    Displaying a mostly white image with some very thin black lines is the best way to hide ghosting. Not saying it was intentional, but just saying.

    • Bob

      So are you suggesting that pancake lenses in general are doomed to failure? Do you have any better alternatives? If you do, please share.

      • logi43212

        The typical “do it better or your argument is invalid” response. All I said was that it has issues like any other tech, better in some areas, worse in others.

        • Bob

          “The typical “do it better or your argument is invalid” response”

          No it isn’t. Re-read the comment.

          As far as any reader can tell, your original comment only highlights the negatives of the technology; one after the other which doesn’t exactly paint an optimistic picture about its future.

          And that explains the somewhat “typical” and pessimistic response. Suggestions of alternatives that warrant a more positive outtake from you would be appreciated though.

          • logi43212

            You’re full of it.
            Criticism is about listing the issues.

          • Dave

            I’m with you Logi43212. I don’t know what these guys had for breakfast but it clearly wasn’t weetabix. Thank you for the informative insight on pancake lenses. I’m still excited to see what Meta come up with for there new headset and we already know resolution and FoV will not be ground breaking but the rest of the tech should make up for it.

          • Zantetsu

            It’s possible to provide an insightful original comment and NOT follow it up by acting like a douche when someone posts a follow-up question. Just saying.

          • Zantetsu

            All he asked is if you know of better alternatives to the thing you are criticizing. Originally, I would have been interested in hearing your response, but at this point, I really don’t want to hear anything else you have to say on the topic.

          • Bob

            Sure it is but ironically in this particular case, you’ve essentially “invalidated” this argument by stating beforehand “All I said was that it has issues like any other tech, better in some areas, worse in others.“. If you’re going to make an argument like this then it would make logical sense to follow through with it; list the pros and the cons.

            And there’s no need to rude about it either. Clearly, being respectful and civil about things isn’t something you’re particularly aquainted with.

          • logi43212

            Bob, quit trying to win an argument, I didn’t post here to babysit you. I shared info others found useful.
            You were clearly being sarcastic and I wasn’t the only one who saw it.
            I don’t need to list the pros, as it’s already listed here by the author of the article and CEO of Kopin.
            You’re clearly just arguing for the sake of arguing and have contributed zero useful info here.

            Go bother someone else.

          • Bob

            Pathetic man with a superiorirty complex.

          • logi43212

            Okay, are you done yet? You’re the one being a sarcastic douche wasting other people’s time with your bs and then get defensive when being called out for it.

          • Lucidfeuer

            STFU loser shill.

        • Zantetsu

          Bob never said your argument was invalid. You appear to be one of those people who immediately assume that any response to a comment is a personal attack. Try developing some human level conversational skills, they will take you far in life.

          • Dave

            FFS Bob’s comments are dripping with sarcasim. Zantetsu comment was the one which has got all emotional. Logi43212 comments are informative and to the point. Honestly you lot are acting like a bunch of old women!

          • Zantetsu

            Bob asked a reasonable follow up question and logi43212 went all super defensive. Not sure if we’re reading the same comments.

          • logi43212

            Accuse me of being presumptous while calling me “one of those people”.

            In the same comment you proceed to being a patronising a-hole while telling me to “Try developing some human level conversational skills”.

            You won the hypocrite award twice with your comment.

            I work in the VR hardware industry and post information on the tech here, I’m not here to babysit teenagers who are being sarcastic because they don’t have anything else to do with their time. You can call me rude but I don’t care.

    • silvaring

      Isn’t 1.3″ just a current limit of the wafer manufacturing process? If so that would be overcome like any other wafer manufacturing node challenge right? In other words higher densities and smarter packaging of transistors without massively decreasing yield / heat performance. I have no idea how challenging it is with regards to micro displays though, so pardon my ignorance.

      • logi43212

        Changing size of wafers is far from trivial. And extremely expensive so it’s the huge firms who attempt it and others like microdisplay manufacturers just take advantage of those improvements.

        I believe they (the big players) tried increasing the wafer size few years ago before COVID but had to abandon that idea back then because it was so hard. I wish I had that article bookmarked.

        Kopin’s CEO wouldn’t explicitly state that the 1.3″ is their limit without following it up with claim or hope that they would improve it, because it’s bad marketing. He had to say the limit because it is what it is.
        I was told the exact same thing by SeeYa last year.

        • silvaring

          Thanks for the follow up info, any thoughts on the Fraunhofer Micro OLEDs being worked on for glasses like devices like the LetinAR glasses? Those seem to be optimizing for the AR market, so small field of view but high pixel density and extremely small form factors. Thats probably the winning horse here to take VR / AR mainstream no?

    • Bjørn Konestabo

      With eye-tracking there is a lot more that can be corrected in software.

      • Andross

        you can’t correct what you can’t measure. knowing your eye movements doesn’t mean knowing what color aberration you are facing in that moment. it’s impossible.

    • Ming

      I’m pretty sure Kopin is at least partially owned by Chinese firms, so the technology will show up in consumer devices as soon as it’s practical to do so.

  • kontis

    There isn’t a company that will offer microdisplays-based HMD with wide FOV, because it’s a limitation of physics.
    It’s already impressive they can almost match current VR headsets with them.

    And the industry will love it. They don’t have an interest in going beyond 110 deg and form factor and comfort will be a better sell, because people care a lot about how things look.

    • Lucidfeuer

      And it’s cost/yield. Also saying people don’t care is not true, in fact that’s why VR is still a niche.

    • ZeePee

      People. Care a lot about how comfortable the headset is.

      If it means sticking to the same level of FoV, I think a lot of people are ok with that tradeoff for now.

      Personally I want both higher FoV and better comfort.

      If the display quality is better and the visuals are substantially improved (excluding FoV) in a significantly more comfortable, significantly smaller, lighter headset, then I’d go with that for now I think.

  • MasterElwood

    Why does everyone want a slim hmd? I don’t give a damn how bulky my hmd is. I just want the best resolution and the best fov.

    • Charles

      I don’t care about bulk, but I care a lot about weight, which I would assume would be reduced with less bulk.

    • Even Glemmestad

      Agreed, but I care about weight in the case of MOMENTUM. As in, the closer the weight is to my face or the less it weighs overall, the less it will jiggle-jiggle as I rapidly turn my head from left to right.

    • Andrew Jakobs

      But I do want clear lenses, not the fresnelcrap all headsets have today. But I certainly want at least the same FOV as current headset, rather larger. At this point in time I’d rather have 140+ degrees FOV than higher resolution (as the reverb G2).

  • Pancake lenses …? tss
    What about waffle lenses or somethin’ …?
    #TssTss

    • ZeePee

      Are you the dog whisperer?

  • ZeePee

    This is the display and optics that the Meganex is using.

    Can’t wait to try it!