Archive for March 9, 2017

Avegant “Light Field” Display – Magic Leap at 1/100th the Investment?

Surprised at CES 2017 – Avegant Focus Planes (“Light Field”)

While at CES 2017 I was invited to Avegant’s Suite and was expecting to see a new and improved and/or a lower cost version of the Avegant Glyph. The Glyph  was a hardly revolutionary; it is a DLP display based, non-see-through near eye display built into a set of headphones with reasonably good image quality. Based on what I was expecting, it seemed like a bit much to be signing an NDA just to see what they were doing next.

But what Avegant showed was essentially what Magic Leap (ML) has been claiming to do in terms of focus planes/”light-fields” with vergence & accommodation.  But Avegant had accomplished this with likely less than 1/100th the amount of money ML is reported to have raised (ML has raised to date about $1.4 billion). In one stroke they made ML more believable and at the same time raises the question why ML needed so much money.

What I saw – Technology Demonstrator

I was shown was a headset with two HDMI cables for video and USB cable for power and sensor data going to an external desktop computer all bundle together. A big plus for me was that there enough eye relief that I could wear my own glasses (I have severe astigmatism so just diopter adjustments don’t work for me). The picture at left is the same or similar prototype I wore. The headset was a bit bulkier than say Hololens, plus the bundle of cables coming out of it. Avegant made it clear that this was an engineering prototype and nowhere near a finished product.

The mixed reality/see-through headset merges the virtual world with the see-through real world. I was shown three (3) mixed reality (MR) demos, a moving Solar System complete with asteroids, a Fish Tank complete with fish swimming around objects in the room and a robot/avatar woman.

Avegant makes the point that the content was easily ported from Unity into their system with fish tank video model coming from the Monterrey Bay Aquarium and the woman and solar system being downloaded from the Unity community open source library.  The 3-D images were locked to the “real world” taking this from simple AR into be MR. The tracking was not all perfect, nor did I care, the point of the demo was the focal planes, lots of companies are working on tracking.

It is easy to believe that by “turning the crank” they can eliminate the bulky cables and  the tracking and locking to between the virtual and real world will improve. It was a technology capability demonstrator and on that basis it has succeeded.

What Made It Special – Multiple Focal Planes / “Light Fields”

What ups the game from say Hololens and takes it into the realm of Magic Leap is that it supported simultaneous focal planes, what Avegant call’s “Light Fields” (a bit different than true “light fields” to as I see it). The user could change what they were focusing in the depth of the image and bring things that were close or far into focus. In other words, they simultaneously present to the eye multiple focuses. You could also by shifting your eyes see behind objects a bit. This clearly is something optically well beyond Hololens which does simple stereoscopic 3-D and in no way presents multiple focus points to the eye at the same time.

In short, what I was seeing in terms of vergence and accommodation was everything Magic Leap has been claiming to do. But Avegant has clearly spent only very small fraction of the development cost and it was at least portable enough they had it set up in a hotel room and with optics that look to be economical to make.

Now it was not perfect nor was Avegant claiming it to be at this stage. I could see some artifacts, in particularly lots of what looked like faint diagonal lines. I’m not sure if these were a result of the multiple focal planes or some other issue such as a bug.

Unfortunately the only available “through the lens” video currently available is at about 1:01 in Avegant’s Introducing Avegant Light Field” Vimeo video. There are only a few seconds and it really does not demonstrate the focusing effects well.

Why Show Me?

So why were they more they were showing it to me, an engineer and known to be skeptical of demos? They knew of my blog and why I was invited to see the demo. Avegant was in some ways surprising open about what they were doing and answered most, but not all, of my technical questions. They appeared to be making an effort to make sure people understand it really works. It seems clear they wanted someone who would understand what they had done and could verify it it some something different.

What They Are Doing With the Display

While Avegant calls their technology “Light Fields” it is implemented with (directly quoting them) “a number of fixed digital focal planes, and then interpolate the planes in-between them.” Multiple focus planes have many of the same characteristics at classical light fields, but require much less image data be simultaneously presented to the eye and thus saving power on generating and displaying as much image data, much of which the eye will not “see”/use.

They are currently using a 720p DLP per eye for the display engine but they said they thought they could support other display technologies in the future. As per my discussion on Magic Leap from November 2016, DLP has a high enough field rate that they could support displaying multiple images with the focus changing between images if you can change the focus fast enough. If you are willing to play with (reduce) color depth, DLP could support a number of focus planes. Avegant would not confirm if they use time sequential focus planes, but I think it likely.

They are using “birdbath optics” per my prior article with a beam splitter and spherical semi-mirror /combiner (see picture at left). With a DLP illuminated by LEDs, they can afford the higher light losses of the birdbath design and support having a reasonable amount of transparency to the the real world. Note, waveguides also tend to lose/wast a large amount of light as well. Avegant said that the current system was 50% transparent to the real world but that the could make it more (by wasting more light).

Very importantly, a birdbath optical design can be very cheap (on the order of only a few dollars) whereas the waveguides can cost many tens of dollars (reportedly Hololen’s waveguides cost over $100 each). The birdbath optics also can support a very wide field of view (FOV), something generally very difficult/expensive to support with waveguides. The optical quality of a birdbath is generally much better than the best waveguides. The downside of the birdbath compared to waveguides that it is bulkier and does not look as much like ordinary glasses.

What they would not say – Exactly How It Works

The one key thing they would not say is how they are supporting the change in focus between focal planes. The obvious way to do it would with some kind of electromechanical device such as moving focus or a liquid filled lens (the obvious suspects). In a recent interview, they repeatedly said that there were no moving parts and that is was “economical to make.”

What They are NOT Doing (exactly) – Mechanical Focus and Eye/Pupil Tracking

After meeting with Avegant at CES I decided to check out their recent patent activity and found US 2016/0295202 (‘202). It show a birdbath optics system (but with a non-see through curved mirror). This configuration with a semi-mirror curved element would seem to do what I saw. In fact, it is very similar to what Magic Leap showed in their US application 2015/0346495.

Avegant’s ‘202 application uses a combination of a “tuning assembly 700” (some form of electro-mechanical focus).

It also uses eye tracking 500 to know where the pupil is aimed. Knowing where the pupil is aimed would, at least in theory, allow them to generate a focus plane for the where the eye is looking and then an out of focus plane for everything else. At least in theory that is how it would work, but this might be problematical (no fear, this is not what they are doing, remember).

I specifically asked Avegant about the ‘202 application and they said categorically that they were not using it and that the applications related to what they were using has not yet been published (I suspect it will be published soon, perhaps part of the reason they are announcing now). They categorically stated that there were “no moving parts” and that the “did not eye track” for the focal planes. They stated that the focusing effect would even work with say a camera (rather than an eye) and was in no way dependent on pupil tracking.

A lesson here is that even small companies file patents on concepts that they don’t use. But still this application gives insight into what Avegant was interested in doing and some clues has to how the might be doing it. Eliminate the eye tracking and substitute a non-mechanical focus mechanism that is rapid enough to support 3 to 6 focus planes and it might be close to what they are doing (my guess).

A Caution About “Demoware”

A big word of warning here about demoware. When seeing a demo, remember that you are being shown what makes the product look best and examples that might make it look not so good are not shown.

I was shown three short demos that they picked, I had no choice. I could not pick my own test cases.I also don’t know exactly the mechanism by which it works, which makes it hard to predict the failure mode, as in what type of content might cause artifacts. For example, everything I was shown was very slow moving. If they are using sequential focus planes, I would expect to see problems/artifacts with fast motion.

Avegant’s Plan for Further Development

Avegant is in the process of migrating away from requiring a big PC and onto mobile platforms such as smartphones. Part of this is continuing to address the computing requirement.

Clearly they are going to continue refining the mechanical design of the headset and will either get rid of or slim down the cables and have them go to a mobile computer.  They say that all the components are easily manufactureable and this I would tend to believe. I do wonder how much image data they have to send, but it appears they are able to do with just two HDMI cables (one per eye). It would seem they will be wire tethered to a (mobile) computing system. I’m more concerned about how the image quality might degrade with say fast moving content.

They say they are going to be looking at other (than the birdbath) combiner technology; one would assume a waveguide of some sort to make the optics thinner and lighter. But going to waveguides could hurt image quality and cost and may more limit the FOV.

Avegant is leveraging the openness of Unity to support getting a lot of content generation for their platform. They plan on a Unity SDK to support this migration.

They said they will be looking into alternatives for the DLP display, I would expect LCOS and OLED to be considered. They said that they had also thought about laser beam scanning but their engineers objected to trying for eye safety reasons; engineers are usually the first Guinea pigs for their own designs and a bug could be catastrophic. If they are using time sequential focal planes which is likely, then other technologies such as OLED, LCOS or Laser Beam Scanning cannot generate sequential planes fast enough to support that more than a few (1 to 3) focal planes per 1/60th of a second on a single device at maximum resolution.

How Important is Vergence/Accomodation (V/A)?

The simple answer is that it appears that Magic Leap raised $1.4B by demoing it. But as they say, “all that glitters is not gold.” The V/A conflict issue is real, but it mostly affects content that virtually appears “close”, say inside about 2 meters/6 feet.

Its not clear that for “everyday use” there might be simpler, less expensive and/or using less power ways to deal with V/A conflict such as pupil tracking. Maybe (don’t know) it would be enough to simply change the focus point when the user is doing close up work rather than have multiple focal planes presented to the eye simultaneously .

The business question is whether solving V/A alone will make AR/MR take off? I think the answer to this is clearly no, this is not the last puzzle piece to be solved before AR/MR will take off. It is one of a large number of issues yet to be solved. Additionally, while Avegant says they have solved it economically, what is economical is relative. It still has added weight, power, processing, and costs associated with it and it has negative impacts on the image quality; the classic “squeezing the balloon” problem.

Even if V/A added nothing and cost nothing extra, there are still many other human factor issues that severely limit the size of the market. At times like this, I like to remind people the the Artificial Intelligence boom in the 1980s (over 35 years ago) that it seemed all the big and many small companies were chasing as the next era of computing. There were lots of “breakthroughs” back then too, but the problem was bigger than all the smart people and money could solve.

BTW, it you want to know more about V/A and related issues, I highly recommend reading papers and watching videos by Gordon Wetzstein of Stanford. Particularly note his work on “compressive light field displays” which he started working on while at MIT. He does an excellent job of taking complex issues and making them understandable.

Generally Skeptical About The Near Term Market for AR/MR

I’m skeptical that with or without Avegant’s technology, the Mixed Reality (MR) market is really set to take off for at least 5 years (an likely more). I’ve participated in a lot of revolutionary markets (early video game chips, home/personal computers, graphics accelerators, the Synchronous DRAMs, as well as various display devices) and I’m not a Luddite/flat-earther, I simply understand the challenges still left unsolved and there are many major ones.

Most of the market forecasts for huge volumes in the next 5 years are written by people that don’t have a clue as to what is required, they are more science fiction writers than technologist. You can already see companies like Microsoft with Hololens and before them Google with Google Glass, retrenching/regrouping.

Where Does Avegant Go Business Wise With this Technology?

Avegant is not a big company. They were founding in in 2012. My sources tell me that they have raise about $25M and I have heard that they have only sold about $5M to $10M worth of their first product, the Avegant Glyph. I don’t see the Glyph ever as being a high volume product with a lot of profit to support R&D.

A related aside: I have yet to see a Glyph “in the wild” being using say on an airplane (where they would make the most sense). Even though the Glyph and other headsets exist, people given a choice still by vast percentages still prefer larger smartphones and tablets for watching media on the go. The Glyph sells for about $500 now and is very bulky to store, whereas a tablet easily slips into a backpack or other bag and the display is “free”/built in.

But then, here you have this perhaps “key technology” that works and that is doing something that Magic Leap has raised over $1.4 Billion dollars to try and do. It is possible (having not thoroughly tested either one), that Avegant’s is better than ML’s. Avegant’s technology is likely much more cost effective to make than ML’s, particularly if ML’s depends on using their complex waveguide.

Having not seen the details on either Avegant’s or ML’s method, I can’t say which is “best” both image wise and in terms of cost, nor whether from a patent perspective, whether Avegant’s is different from ML.

So Avegant could try and raise money to do it on their own, but they would have to raise a huge amount to last until the market matures and compete with much bigger companies working in the area. At best they have solved one (of many) interesting puzzle pieces.

It seems obvious (at least to me) that more likely good outcome for them would be as a takeover target by someone that has the deep pockets to invest in mixed reality for the long haul.

But this should certainly make the Magic Leap folks and their investors take notice. With less fanfare, and a heck of a lot less money, Avegant has as solution to the vergence/accommodation problem that ML has made such a big deal about.

Near-Eye Bird Bath Optics Pros and Cons – And IMMY’s Different Approach

Why Birdbaths Optics? Because the Alternative (Waveguides) Must Be Worse (and a teaser)

The idea for this article started when I was looking at the ODG R-9 optical design with OLED microdisplays. They combined an OLED microdisplay that is not very bright in terms of nits with a well known “birdbath” optical design that has very poor light throughput. It seems like a horrible combination. I’m fond of saying “when intelligent people chose a horrible design, the alternative must have seemed worse

I’m going to “beat up” so to speak the birdbath design by showing how some fundamental light throughput numbers multiply out and why the ODG R-9 I measured at CES blocks so much of the real world light. The R-9 also has a serious issue with reflections. This is the same design that a number of publications considered among the “best innovations” of CES; it seems to me that they must have only looked at the display superficially.

Flat waveguides such as used by Hololens, Vuzix. Wave Optics, and Lumus as well as expected from Magic Leap get most of the attention, but I see a much larger number of designs using what is known as a “birdbath” and similar optical designs. Waveguides are no secret these days and the fact that so many designs still use the birdbath optics tells you a lot about the issues with waveguides. Toward the end of this article, I’m going to talk a little about the IMMY design that replaces part of the birdbath design.

As a teaser, this article is to help prepare for an article on an interesting new headset I will be writing about next week.

Birdbath Optics (So Common It Has a Name)

The birdbath combines two main optical components, a spherical mirror/combiner (part-mirror) and a beam splitter. The name  “birdbath” comes from the spherical mirror/combiner looking like a typical birdbath. It is used because it generally is comparatively inexpensive to down right cheap while also being relatively small/compact while having  good overall image quality. The design fundamentally supports a very wide FOV, which are at best difficult to support with waveguides. The big downsides are light throughput and reflections.

A few words about Nits (Cd/m²) and Micro-OLEDs

I don’t have time here to get into a detailed explanation of nits (Cd/m²). Nits is the measure of light at a given angle whereas lumens is the total light output. The simplest analogy is to water hose with a nozzle (apropos here since we are talking about birdbaths). Consider two spray patterns, one with a tight jet of water and one with a wide fan pattern both outputting the exact same total amount of water per minute (lumens in this analogy). The one with the tight patter would have high water pressure (nits in this analogy) over a narrow angle where the fan spray would have lower water pressure (nits) over a wider angle.

Additionally, it would be relatively easy to put something in the way of the tight jet and turn it into a fan spray but there is no way to turn the fan spray into a jet. This applies to light as well, it is much easier to go from high nits over are narrow angle to lower nits over a wide angle (say with a diffuser) but you can’t go the other way easily.

Light from an OLED is like the fan spray only it covers a 180 degree hemisphere. This can be good for a large flat panel were you want a wide viewing angle but is a problem for a near eye display where you want to funnel all the light into the eye because so much of the light will miss pupil of the eye and is wasted. With an LED you have a relative small point of light that can be funneled/collimated into a tight “jet” of light to illuminate an LCOS or DLP microdisplay.

The combination of light output from LEDs and the ability to collimate the light means you can easily get tens of thousands of nits with an LCOS or DLP illuminated microdisplay were OLED microdisplays typically only have 200 to 300 nits. This is major reason why most see-through near eye displays use LCOS and DLP over OLEDs.

Basic Non-Polarizing Birdbath (example, ODG R-9)

The birdbath has two main optical components, a flat beam splitter and a spherical mirror. In the case a see-through designs, the the spherical mirror is a partial mirror so the spherical element acts as a combiner. The figure below is taken from an Osterhaut Design Group (ODG) patent which and shows simple birdbath using an OLED microdisplay such as their ODG R-9. Depending on various design requirements, the curvature of the mirror, and the distances, the lenses 16920 in the figure may not be necessary.

The light from the display device, in the case of the ODG R-9 is a OLED microdisplay, is first reflect away from the eye and perpendicular (on-axis) to the curved beam splitter so that a simple spherical combiner will uniformly magnify and move the apparent focus point of the image (if not “on axis” the image will be distorted and the magnification will vary across the image). The curved combiner (partial mirror) has minimal optical distortion on light passing through.

Light Losses (Multiplication is a Killer)

A big downside to the birdbath design is the loss of light. The image light must make two passes at the beam splitter, a reflective and transmissive, with a reflective (Br) and transmissive (Bt) percentages of light. The light making it through both passes is Lr x Lt.  A 50/50 beam splitter might be about 48% reflective and transmissive (with say a 4% combined loss), and the light throughput (Br x Bt) in this example is only 48% x 48%= ~23%. And “50/50” ratio is the best case; if we assume a nominally 80/20 beam splitter (with still 4% total loss) we get 78% x 18% = ~14% of the light making through the two passes.

Next we have the light loss of the spherical combiner. This is a trade-off of image light being reflected (Cr) versus being transmitted  (Ct) to the real world where Cr + Ct is less than 1 due to losses. Generally you want the Cr to be low so the Ct can be high so you can see out (otherwise it is not much of a see through display).

So lets say the combiner has Cr=11% and the Ct=75% with about 4% loss with the 50/50 beamsplitter. The net light throughput assuming a “50/50” beam splitter and a 75% transmissive combiner is Br x Cr X Bt = ~2.5% !!! These multiplicative losses lose all but a small percentage of the display’s light. And consider that the “real world” net light throughput is Ct x Bt which would be 48% x 75% = 36% which is not great and would be too dark for indoor use.

Now lets say you want the glasses to be at least 80% transmissive so they would be considered usable indoors. You might have the combiner Ct=90% making Cr=6% (with 4% loss) and then Bt=90% making Br=6%. This gives the real world transmissive about 90%x90% = 81%.  But then you go back and realize the display light equation (Br x Cr X Bt) becomes 6%x6%x90% = 0.3%. Yes, only 3/1000ths of the starting image light makes it through. 

Why the ODG R-9 Is Only About 4% to 5% “See-Through”

Ok, now back to the specific case of the ODG R-9. The ODG R-9 has an OLED microdisplay that most like has about 250 nits (200 to 250 nits is commonly available today) and they need to get about 50 nits (roughly) to the eye from the display to have a decent image brightness indoors in a dark room (or one where most of the real world light is blocked). This means they need a total throughput of 50/250=20%. The best you can do with two passes through a beam splitter (see above) is about 23%.  This forces the spherical combiner to be highly reflective with little transmission. You need something that reflects 20/23=~87% of the light and only about 9% transmissive. The real world light then making it through to the eye is then about 9% x 48% (Ct x Bt) or about 4.3%.

There are some other effects such as the amount of total magnification and I don’t know exactly what their OLED display is outputting display and exact nits at the eyepiece, but I believe my numbers are in the ballpark. My camera estimates for the ODG R-9 came in a between 4% and 5%. When you are blocking about 95% of the real world light, are you really much of a “see-through” display?

Note, all this is BEFORE you consider adding say optical shutters or something like Varilux® light blocking. Normally the birdbath design is used with non-see through designs (where you don’t have the see-through losses) or with DLP® or LCOS devices illuminated with much higher nits (can be in the 10’s of thousands) for see through designs so they can afford the high losses of light.

Seeing Double

There are also issues with getting a double image off of each face of plate beam splitter and other reflections. Depending on the quality of each face, a percentage of light is going to reflect or pass through that you don’t want. This light will be slightly displaced based on the thickness of the beamsplitter. And because the light makes two passes, there are two opportunities to cause double images. Any light that is reasonably “in focus” is going to show up as a ghost/double image (for good or evil, your eye has a wide dynamic range and can see even faint ghost images). Below is a picture I took with my iPhone camera of a white and clear menu through the ODG R-9. I counted at least 4 ghost images (see colored arrows).

As a sort of reference, you can see the double image effect of the beamsplitter going in the opposite direction to the image light with my badge and the word “Media” and its ghost (in the red oval).

Alternative Birdbath Using Polarized Light (Google Glass)

Google Glass used a different variation of the birdbath design. They were willing to accept a much smaller field of view and thus could reasonably embedded the optics in glass. It is interesting here to compare and contrast this design with the ODG one above.

First they started with an LCOS microdisplay that was illuminated by LEDs that can be very much brighter and more collimated light resulting in much higher (can be orders of magnitude) starting nits than an OLED microdisplay can output. The LED light is passed through a polarizing beam splitter than will pass about 45% P light to the LCOS device (245). Note a polarizing beam splitter passes one polarization and reflect the other unlike a the partially reflecting beam splitter in the ODG design above. The LCOS panel will rotate the light to be seen to S polarization so that it will reflect about 98% (with say 2% loss) of the S light.

The light then goes to a second polarizing beam splitter that is also acting as the “combiner” that the user sees the real world through. This beam splitter is set up to pass about 90% of the S light and reflect about 98% of the P light (they are usually much better/more-efficient in reflection). You should notice that they have a λ/4 (quarter wave = 45 degree rotation) film between the beam splitter and the spherical mirror which will rotate the light 90 degrees (turning it from S to P) after it passes through it twice. This  λ/4 “trick” is commonly used with polarized light. And since you don’t have to look through the mirror, it can be say 98% reflective with say another 3% loss for the λ/4.

With this design, about 45% (one pass through the beamsplitter) of the real world makes it through, but only light polarized the “right way” makes it through which makes looking at say LCD monitors problematical. By using the quarter wave film the design is pretty efficient AFTER you loose about 55% of the LED light in polarizing it initially. There are also less reflection issues because all the films and optics are embedded in glass so you don’t get these air to glass index mismatches of off two surfaces of a relatively thick plate that cause unwanted reflections/double images.

Google Glass design has a lot of downsides too. There is nothing you can do to get the light throughput of the real world much above 45% and there are always the problems of looking through a polarizer. But the biggest downside is that it cannot be scaled up for larger fields of view and/or more eye relief. As you scale this design up the block of glass becomes large, heavy and expensive as well as being very intrusive/distorting in looking through a big thick piece of glass.

Without getting too sidetracked, Lumus in effect takes the one thick beam splitter, and piece-wise cuts it into multiple smaller beam splitters to make the glass thinner. But this also means you can’t use the spherical mirror of a birdbath design with it and so you require optics before the beam splitting and the light losses of the the piece-wise beam splitting are much larger than a single beamsplitter.

Larger Designs

An alternative design would mix the polarizing beamsplitters of the Google Glass design above with the configuration of ODG design above.  And this has been done many times through the years with LCOS panels that use polarized light (an example can be found in this 2003 paper). The spherical mirror/combiner will be a partial non-polarizing mirror so you can see through it and a quarter waveplate is used between the spherical combiner and the polarizing beam splitter. You are then stuck with about 45% of the real world light times the light throughput of the spherical combiner.

A DLP with a “birdbath” would typically use the non-polarizing beam splitter with a design similar to the ODG R-9 but replacing the OLED microdisplay with a DLP and illumination. As an example, Magic Leap did this with a DLP but adding a variable focus lens to support focus planes.

BTW, by the time you polarized the light from an OLED or DLP microdisplay, there would not be much if any of an efficiency advantage sense to use polarizing beamsplitters. Additionally, the light from the OLED is so diffused (varied in angles) that it would likely not behave well going through the beam splitters.

IMMY – Eliminating the Beamsplitter

The biggest light efficiency killer in the birdbath design is the combined reflective/transmissive passes via the beamsplitter. IMMY effectively replaces the beamsplitter of the birdbath design with two small curved mirrors that he correct for the image being reflected off-axis from the larger curved combiner. I have not yet seen how well this design works in practice but at least the numbers would appear to work better. One can expect only a few percentage points of light being lost off of each of the two small mirrors so that maybe 95% of the light from the OLED display make it to the large combiner. Then you have the the combiner reflection percentage (Cr) multiplying by about 95% rather than the roughly 23% of the birdbath beam splitter.

The real world light also benefits as it only has to go through a single combiner transmissive loss (Ct) and no beamsplitter (Bt) loses. Taking the OGD R-9 example above and assuming we started with a 250 nit OLED and with 50 nits to the eye, we could get there with about an 75% transmissive combiner. The numbers are at least starting to get into the ballpark where improvements in OLED Microdisplays could fit at least for indoor use (outdoor designs without sunshading/shutters need on the order of 3,000 to 4,000 nits).

It should be noted that IMMY says they also have “Variable transmission outer lens with segmented addressability” to support outdoor use and variable occlusion. Once again this is their claim, I have not yet tried it out in practice so I don’t know the issues/limitations. My use of IMMY here is to contrast it with the classical birdbath designs above.

A possible downside to the the IMMY multi-mirror design is bulk/size has seen below. Also noticed the two adjustment wheel for each eye. One is for interpupillary distance to make sure the optics line up center with the pupils which varies from person to person. The other knob is a diopter (focus) adjustment which also suggests you can’t wear these over your normal glasses.

As I have said, I have not seen IMMY’s to see how it works and to see what faults it might have (nothing is perfect) so this is in no way an endorsement for their design. The design is so straight forward and a seemingly obvious solution to the beam splitter loss problem that it makes me wonder why nobody has been using it earlier; usually in these cases, there is a big flaw that is not so obvious.

See-Though AR Is Tough Particularly for OLED

As one person told me at CES, “Making a near eye display see-through generally more than double the cost” to which I would add, “it also has serious adverse affects on the image quality“.

The birdbath design wastes a lot of light as do every other see-through designs. Waveguide designs can be equally or more light wasteful than the birdbath. At least on paper, the IMMY design would appear to waste a less than most others. But to make a device say 90% see through, at best you start by throwing away over 90% of the image light/nits generated, and often more than 95%.

The most common solution to day is to start with LED illuminated LCOS or DLP microdisplay so you have a lot of nits to throw at the problem and just accept the light waste. OLEDs are still orders of magnitude in brightness/nits away from being able to compete with LCOS and DLP with brute force.