As I wrote in 2012’s Cynics Guide to CES—Glossary of Terms, when you see a demo at a conference, “sometimes you are seeing a “magic show” that has little relationship to real-world use.” I saw the Cogni Trax hard edge occlusion demo last week at SID Display Week 2024, and it epitomized the concept of being a “magic show.” I have been aware of Congi Trax for at least three years (and commented about the concept on Reddit), and I discovered they quoted me (I think a bit out of context) on its website (more on this later in the Appendix).
Cogni Trax has reportedly raised $7.1 million in 3 funding rounds over the last ~7 years, which I plan to show is unwarranted. I contacted Cogni Trax’s CEO (and former Apple optical designer on the Apple Vision Pro), Sajjad Khan, who was very generous in answering questions despite his knowing my skepticism about the concept.
Nobody will notice if you put a pixel-sized (angularly) dot on a person’s glasses. If it did, every dust particle on a person’s glasses would be noticeable and distracting. That is because a dot only a few millimeters from the eye is highly out of focus, and light rays from the real world will go around the dot before they are focused by the eye’s lens. That pixel dot will insignificantly dim several thousand pixels in the virtual image. As discussed in the Magic Leap soft occlusion article, the Magic Leap 2’s dimming pixel will cover ~2,100 pixels (angularly) in the virtual image and have a dimming effect on hundreds of thousands of pixels.
Hard Edge Occlusion (Optical and Camera Passthrough)
“Hard Edge Occlusion” means the precise, pixel-by-pixel light blocking. With camera passthrough AR (such as Apple Vision Pro), hard edge occlusion is trivial; one or more camera pixels are replaced by one or more pixels in the virtual image. Even though masking pixels is trivial with camera passthrough, there is still a non-trivial problem with getting the hard edge masking perfectly aligned to the real world. With passthrough mixel reality, the passthrough camera with its autofocus has focused the real world so it can be precisely masked.
With optical mixed reality hard edge occlusion,the real world must also be brought into focus before it can be precisely masked. Rather than going to a camera, the real world’s light goes to a reflective masking spatial light modular (SLM), typically LCOS, before combining it optically with the virtual image.
In Hard Edge (Pixel) Occlusion—Everyone Forgets About Focus, I discuss Arizona State University’s (ASU) optical solution for hard edge occlusion. Their solution has a set of optics that focuses the real world onto an SLM for masking. Then, a polarizing beam-splitting cube combines the result (with a change in polarization via two passes through a quarter waveplate not shown) after masking with a micro-display. While the ASU patent mentions using a polarizing beam splitter to combine the images, the patent fails to show or mention the need for a quarter waveplate between the SLM and beam splitter to work. One of the inventors, Hong Hua, was an ASU professor and a consultant to Magic Leap, and the patent was licensed to Magic Leap.
Other than being big and bulky, optically, what is wrong with the ASU’s hard edge occlusion includes:
It only works to hard edge occlude at a distance set by the focusing. Ano
The real world is “flatted” to be at the same focus as the virtual world.
Polarization dims the real world by at least 50%. Additionally, viewing a polarized display device (like a typical LCD monitor or phone display) will be at least partially blocked by an amount that will vary with orientation relative to the optics.
The real world is dimmed by at least 2x via the polarizing beam splitter.
As the eye moves, the real world will move differently than it would with the eye looking directly. You are looking at the real world through two sets of optics with a much longer light path.
While Cogni Trax uses the same principle for masking the real world, it is configured differently and is much smaller and lighter. Both devices block a lot of light. Cogni Trax’s design blocks about 77% of the light, and they claim their next generation will block 50%. However, note that this is likely on top of any other light losses in the optical system.
Cogni Trax SID Display Week 2024 Demo
On the surface, the Cogni Trax demo makes it look like the concept works. The demo had a smartphone camera looking through the Cogni Trax optical device. If you look carefully, you will see that they block light from 4 areas of the real world (see arrow in the inset picture below), a Nike swoosh on top of the shoe, a QR code, the Coke in the bottle (with moving bubbles), and a partially darken the wall to the right to create a shadow of the bottle.
They don’t have a microdisplay with a virtual image; thus, they can only block or darken the real world and not replace anything. Since you are looking at the image on a cell phone and not with your own eyes, you have no sense of the loss of depth and parallax issues.
When I took the picture above, I was not planning on writing an article and missed capturing the whole setup. Fortunately, Robert Scoble put out an X-video that showed most of the rig used to align the masking to the real world. The rig supports aligning the camera and Cogni Trax device with six degrees of freedom. This demo will only work if all the objects in the scene are in a precise location relative to the camera/device. This is the epitome of a canned demo.
One could hand wave that developing SLAM, eye tracking, and 3-D scaling technology to eliminate the need for the rig is a “small matter of hardware and software” (to put it lightly). However, requiring a rig is not the biggest hidden trick in these demos; it is the basic optical concept and its limitations. The “device” shown (lower right inset) is only the LCOS device and part of the optics.
Cogni Trax Gen 1 Optics – How it works
Below is a figure of Congi Trax’s patent that will be used to diagram the light path. I have added some colorization to help you follow the diagram. The dashed-lined parts in the patent for combining the virtual image are not implemented in Cogni Trax’s current design.
The view of the real world follows a fairly torturous path. First, it goes through a polarizer where at least 50% of the light is lost (in theory, this polarizer is redundant due to the polarizing beam splitter to follow, but it is likely used to reduce any ghosting). It then bounces off of the polarizing beam splitter through a focusing element to bring the real world into focus on an LCOS SLM. The LCOS device will change the polarization of anything NOT masked so that on the return trip through the focusing element, it will pass through the polarizing beam splitter. The light then passes through the “relay optics,” then a Quarter Waveplate (QWP), off a mirror, and back through the quarter waveplate and relay optics. The two passes through the “relay optics” have to undo everything done to the light by the two passes through the focusing element. The two passes through the QWP will rotate the polarization of the light so that the light will bounce off the beam splitter and be directed at the eye via a cleanup polarizer. Optionally, as shown, the light can be combined with a virtual image from a microdisplay.
I find it hard to believe that real-world light will go through all that and will behave like nothing other than the light losses from polarization that have happened to it.
Cogni Trax provided a set of diagrams showing the light path of what they call “Alpha Pix.” I edited several of their diagrams together and added some annotations in red. As stated earlier, the current prototype does not have a microdisplay for providing a virtual image. If the virtual display device were implemented, its optics and combiner would be on top of everything else shown.
I don’t see this as a practical solution to hard-edge occlusion. While much less bulky than the ASU design, it still requires polarizing the incoming light and sending it through a torturous path that will further damage/distort real-world light. And this is before they deal with adding a virtual image. There is still the issue that the hard edge occlusion only works if everything being occluded is at approximately the same focus distance. If the virtual display is implemented, it would seem that the virtual image would need to be at approximately the same focus distance for it to be occluded correctly. Then, the hardware and software are required to get everything between the virtual and real world aligned with the eye. Even if the software and eye tracking were excellent, there where will still be a lag with any rapid head movement.
Cogni Trax Waveguide Design / Gen 2
Cogni Trax’s website and video discuss a “waveguide” solution for Gen 2. I found a patent(with excerpts right and below) from Cogni Trax for a waveguide approach to hard-edge occlusion that appears to agree with the diagrams in the video and on the website for their “waveguide.” I have outlined the path for the real world (in green) and the virtual image (in red).
Rather than using polarization, this method uses time-sequential modulation via a single Texas Instrument’s DLP/DMD. The DLP is used during part of the time block/pass light from the real world and as the virtual image display. I have included Figure 1(a), which gives the overall light path; Figures 1(c) and 1(d), which show the time multiplexing; Figure 6(a) with a front view of the design; and Figures 10 (a) and (b) which show a side view of the waveguide with the real world and virtual light paths respectively.
Other than not being polarized, the light follows a more torturous light path that includes a “fixed DMD” to correct for the micro-tilts of the real world by time-multiplexed displaying and masking DMD. In addition to all the problems I had with the Gen 1 design, I find putting the relatively small mirror (120 in Figure 1a) in the middle of the view very problematic as the view over or below the mirror will look very different than the view in the mirror with all the addiction optics. While it can theoretically give more light throughput and not require polarization of the real world, it can only do so by keeping the virtual display times short, which will mean more potential field sequential color breakup and lower color bit depth from the DLP.
Overall, I see Cogni Trax’s “waveguide” design as trading one set of problems for another set of probably worse image problems.
Conclusion
Perhaps my calling hard-edge occlusion a “Holy Grail” did not fully convey its impossibility. The more I have learned, examined, and observed this problem and its proposed solutions, the more clearly it seems impossible. Yes, someone can craft a demo that works for a tightly controlled setup with what is occluded at about the same distance, but it is a magic show.
The Cogni Trax demo is not a particularly good magic show, as it uses a massive 6-axis control rig to position a camera rather than letting the user put on a headset. Furthermore, the demo does not support a virtual display.
Cogni Trax’s promise of a future “waveguide” design appears to me to be at least as fundamentally flawed. According to the publicly available records, Cogni Trax has been trying to solve this problem for 7 years, and a highly contrived setup is the best they have demonstrated, at least publicly. This is more of a university lab project than something that should be developed commercially.
Based on his history with Apple and Texas Instruments, the CEO, Sajjad Khan, is capable, but I can’t understand why he is pursuing this fool’s errand. I don’t understand why over $7M has been invested, other than people blindly investing in former Apple designers without proper technical due diligence. I understand that high-risk, high-reward concepts can be worth some investment, but in my opinion, this does not fall into that category.
Appendix – Quoting Out of Context
Cogni Trax has quoted me in their video on their website as saying, “The Holy Grail of AR Displays.” It is not clear that A) I am referring to Hard Edge Occlusion (and not Cogni Trax) and B) I go on to say, “But it is likely impossible to solve for anything more than special cases of a single distance (flat) real world with optics.” The Audio in the Cogni Trax video from me, which is rather garbled, comes from a MARCH 30, 2021, AR Show, “KARL GUTTAG (KGONTECH) ON MAPPING AR DISPLAYS TO SUITABLE OPTICS (PART 2) at ~48:55 into the video (the occlusion issue is only briefly discussed).
Below, I have cited (with new highlighting in yellow) the section from my blog discussing hard edge occlusion from November 20, 2019, where Cogni Trax got my “Holy Grail” quote. This section of the article discusses the ASU design. This article discussed using a transmissive LCD for soft edge occlusion about 3 years before Magic Leap announced the Magic Leap 2 with such a method in July 2022.
“Hard Edge Occlusion” is the concept of being able to block the real world with sharply defined edges, preferably to the pixel level. It is one of the “Holy Grails” of optical AR. Not having hard edge occlusion is why optical AR images are translucent. Hard Edge Occlusion is likely impossible to solve optically for all practical purposes. The critical thing most “solutions” miss (including US 20190324274) is that the mask itself must be in focus for it to sharply block light. Also, to properly block the real world, the focusing effect required depends on the distance of everything in the real world (i.e., it is infinitely complex).
The most common hard edge occlusion idea suggested is to put a transmissive LCD screen in the glasses to form “opacity pixels,” but this does not work. The fundamental problem is that the screen is so close to the eye that the light-blocking elements are out of focus. An individual opacity pixel will have a little darkening effect, with most of the light from a real-world point in space going around it and into the eye. A large group of opacity pixels will darken as a blurry blob.
Hard edge occlusion is trivial to do with pass-through AR by essentially substituting pixels. But it is likely impossible to solve for anything more than special cases of a single distance (flat) real world with optics. The difficulty of supporting even the flat-world special case is demonstrated by some researchers at the University of Arizona, now assigned to Magic Leap (the PDF at this link can be downloaded for free) shown below. Note all the optics required to bring the real world into focus onto “SLM2” (in the patent 9,547,174 figure) so it can mask the real world and solve the case for everything being masked being at roughly the same distance. None of this is even hinted at in the Apple application.
I also referred to hard edge occlusion as one of the “Holy Grails” of AR in a comment to a Magic Leap article in 2018 citing the ASU design and discussing some of the issues. Below is the comment, with added highlighting in yellow.
One of the “Holy Grails” of AR, is what is known as “hard edge occlusion” where you block light in-focus with the image. This is trivial to do with pass-through AR and next to impossible to do realistically with see-through optics. You can do special cases if all the real world is nearly flat. This is shown by some researchers at the University of Arizona with technology that is Licensed to Magic Leap (the PDF at this link can be downloaded for free: https://www.osapublishing.org/oe/abstract.cfm?uri=oe-25-24-30539#Abstract). What you see is a lot of bulky optics just to support a real world with the depth of a bookshelf (essentially everything in the real world is nearly flat).
Introduction – Contrast in Approaches and Technologies
This article will compare and contrast the Vuzix Ultralight, Lumus Z-lens, and DigiLens Argo waveguide-based AR prototypes I saw at CES 2023. I discussed these three prototypes with SadlyItsBradly in our CES 2023 video. It will also briefly discuss the related Avegant’s AR/VR/MR 2022 and 2023 presentations about their new smaller LCOS projection engine and Magic Leap 2’s LCOS design to show some other projection engine options.
It will go a bit deeper into some of the human factors of the Digitlens’ Argo. Not to pick on Digilens’ Argo, but because it has more features and demonstrates some common traits and issues of trying to support a rich feature set in a glasses-like form factor.
When I quote various specs below, they are all manufacturer’s claims unless otherwise stated. Some of these claims will be based on where the companies expect the product to be in production. No one has checked the claims’ veracity, and most companies typically round up, sometimes very generously, on brightness (nits) and field of view (FOV) specs.
This is a somewhat long article, and the key topics discussed include:
MicroLED versus LCOS Optical engine sizes
The image quality of MicroLED vs. LCOS and Reflective (Lumus) vs. Diffractive waveguides
The efficiency of Reflective vs. Diffractive waveguides with MicroLEDs
The efficiency of MicroLED vs. LCOS
Glasses form factor (using Digilens Argo as an example)
They are each about 38 grams in weight, including frames, processing, wireless communication, and batteries, and wirelessVuzix developed their own diffractive waveguide and support about a 30-degree FOV. Both are self-contained with wireless, with an integrated battery and processing.
Vuzix developed their own glass diffractive waveguides and optical engines for the Ultralight. They claim a 30-degree FOV with 3,000 nits.
Oppo uses resin plastic waveguides, and MicroLED optical engine developed jointly with Meta Bounds. I have previously seen prototype resin plastic waveguides from other companies for several years. This is the first time I have seen them in a product getting ready for production. The glasses (described in a 1.5-minute YouTube/CNET video) include microphones and speakers for applications, including voice-to-text and phone calls. They also plan on supporting vision correction with lenses built into the frames. Oppo claims the Air Glass 2 has a 27-degree FOV and outputs 1,400 nits.
Lumus Z-Lens
Lumus’s Z-Lens (third from the top right) supports up to a 2K by 2K full/true color LCOS display with a 50-degree FOV. Its FoV is 3 to 4 times the area of the other three headsets, so it must output more than 3 to 4 times the total light. It supports about 4.5x the number of pixels of the DigiLens Argo and over 13x the pixels of the Vuzix Ultralite and Oppo Air Glass 2.
The Z-Lens prototype is a demonstration of display capability and, unlike the other three, is not self-contained and has no battery or processing. A cable provides the display signal and power for each eye. Lumus is an optics waveguide and projector engine company and leaves it to its customers to make full-up products.
Digilens Argo
The DigiLens Argo (bottom, above right) uses a 1280 by 720 full/true color LCOS display. The Argo has many more features than the other devices, with integrated SLAM cameras, GNSS (GPS, etc.), Wi-Fi, Bluetooth, a 48mp (with 4×4 pixel “binning” like the iPhone 14) color camera, voice recognition, batteries, and a more advanced CPU (Qualcomm Snapdragon 2). Digilens intends to sell the Argo for enterprise applications, perhaps with partners, while continuing to sell waveguides optical engines as components for higher-volume applications. As the Argo has a much more complete feature set, I will discuss some of the pros and cons of some of the human factors of the Argo design later in this article.
Through the Lens Images
Below is a composite image from four photographs taken with the same camera (OM-D E-M5 Mark III) and lens (fixed 17mm). The pictures were taken at conferences, handheld, and not perfectly aligned for optimum image quality. The projected display and the room/outdoor lighting have a wide range of brightness between the pictures. None of the pictures have been resized, so the relative FoVs have been maintained, and you get an idea of the image content.
The Lumus Z-lens reflective waveguide has a much bigger FOV, significantly more resolution, and exhibits much better color uniformity with the same or higher brightness (nits). It also appears that reflective waveguides have a significant efficiency advantage with both MicroLEDs (and LCOS), as discussed in MicroLEDs with Waveguides (CES & AR/VR/MR 2023 Pt. 7). It should also be noted that the Lumus Z-lens prototype has only the display with optics and has no integrated processing, communication or battery. In contrast, the others are closer to full products.
A more complex issue is that of power consumption versus brightness. LCOS engines today are much more efficient for an image with full-screen bright images (by 10x or more) than MicroLEDs with similar waveguides. MicroLED’s big power advantage occurs when the content is sparse, as the power consumption is roughly proportional to the average pixel value, whereas, with LCOS, the whole display is illuminated regardless of the content.
If and when MicroLEDs support full color, the efficiency of nits-per-Watt will be significantly lower than monochrome green. Whatever method produces full color will detract from the overall electrical and optical efficiency. Additionally, color balancing for white requires adding blue and red light with lower nits-per-Watt.
Some caveats:
The Lumus Z-Lens is a prototype and does not have all the anti-reflective and other coatings of a production waveguide. Lumus uses an LCOS device with about ~3-micron pixels, which fits 1440 by 1440 within the ~50-degree FOV supported by the optics. Lumus is working with at least one LCOS maker to get an ~2-micron pixel size to support 2K by 2K resolution with the same size display. The image is cut off on the right-hand side of the image by the camera, which was rotated into portrait mode to fit inside the glasses.
The Digilens through the lens image is from Photonics West in 2022 (about one year old). Digilens has continued to improve its waveguide since this picture was taken.
The Vuzix picture was taken via Vuzix Shield, which uses the same waveguide and optics as the Vuzix Ultralight.
The Oppo image was taken at the AR/VR/MR 2023 conference.
Optical Engine Sizes
Vuzix has an impressively small optical engine driving Vuzix’s diffractive waveguides. Seen below left is a comparison of Vuzix’s older full-color DLP engine compared with an in-development color X-Cube engine and the green MicroLED engine used in the Vuzix Ultralite™ and Shield. In the center below is an exploded view of the Oppo and Meta Bound glasses (joint design as they describe it) with their MicroLED engine shown in their short CNET YouTube video. As seen in the still from the Oppo video, they have plans to support vision correction built into the glasses.
Below right is the Digilens LCOS engine, which uses a fairly conventional LCOS (using Ominivision’s LCOS device with driver ASIC showing). The dotted line indicates where the engine blocks off the upper part of the waveguide. This blocked-off area carries over to the Argo design.
The Digilens Argo, with its more “conventional” LCOS engine, requires are large “brow” above the eye to hide it (more on this issue later). All the other companies have designed their engine to avoid this level of intrusion into the front area of the glasses.
Lumus had developed their 1-D pupil-expanding reflective waveguide for nearly two decades, which needed a relatively wide optical engine. With the 2-D Maximus waveguide in 2021 (see: Lumus Maximus 2K x 2K Per Eye, >3000 Nits, 50° FOV with Through-the-Optics Pictures), Lumus demonstrated their ability to shrink the optical engine. This year, Lumus further reduced the size of the optical engine and its intrusion into the front lens area with their new Z-lens design (compare the two right pictures below of Maximus to Z-Lens)
Shown below are frontal views of the four lenses and their optical engines. The Oppo Air Glass 2 “disguises” the engine within the industrial design of a wider frame (and wider waveguide). The Lumus Z-Lens, with a full color about 3.5 times the FOV as the others, has about the same frontal intrusion as the green-only MicroLED engines. The Argo (below right) stands out with the large brow above the eye (the rough location of the optical engine is shown with the red dotted line).
Lumus Removes the Need for Air Gaps with the Z-Lens
Another significant improvement with Lumus’s Z-Lens is that unlike Lumus’s prior waveguides and all diffractive waveguides, it does not require an air gap between the waveguide’s surface and any encapsulating plastics. This could prove to be a big advantage in supporting integrated prescription vision correction or simple protection. Supporting air gaps with waveguides has numerous design, cost, and optical problems.
A typical full-color diffractive waveguide typically has two or three waveguides sandwiched together, with air gaps between them plus an air gap on each side of the sandwich. Everywhere there is an air gap, there is also a desire for antireflective coatings to remove reflections and improve efficiency.
Avegant and Magic Leap Small LCOS Projector Engines
Older LCOS projection engines have historically had size problems. We are seeing new LCOS designs, such as the Lumus Z-lens (above), and designs from Avegant and Magic Leap that are much smaller and no more intrusive into the lens area than the MicroLED engines. My AR/VR/MR 2022 coverage included the article Magic Leap 2 at SPIE AR/VR/MR 2022, which discusses the small LCOS engines from both Magic Leap and Avegant. In our AWE 2022 video with SadlyItsBradley, I discuss the smaller LCOS engines by Avegant, Lumus (Maximus), and Magic Leap.
Below is what Avegant demonstrated at AR/VR/MR 2022 with their small “L” shaped optical engines. These engines have very little intrusion into the front lenses, but they run down the temple of the glasses, which inhibits folding the temple for storage like normal glasses.
At the AR/VR/MR 2023, Avegant showed a newer optical design that reduced the footprint of their optics by 65%, including shortening them to the point that the temples can be folded, similar to conventional glasses (below left). It should be noted that what is called a “waveguide” in the Avegant diagram is very different from the waveguides used to show the image in AR glasses. Avegants waveguide is used to illuminate the LCOS device. Avengant, in their presentation, also discussed various drive modes of the LEDs to give higher brightness and efficiency with green-only and black-and-white modes. The 13-minute video of Avegant’s presentation is available at the SPIE site (behind SPIE’s paywall). According to Avegant’s presentation, the optics are 15.6mm long by 12.4mm wide, support a 30-degree FOV, with 34 pixels/degree, and 2 lumens of output in full color and up to 6 lumens in limited color outdoor mode. According to the presentation, they expect about 1,500 nits with typical diffractive waveguides in the full-color mode, which would roughly double in the outdoor mode.
The Magic Leap 2 (ML2) takes reducing the optics one step further and puts the illumination LEDs and LCOS on opposite sides of the display’s waveguide (below and described in Magic Leap 2 at SPIE AR/VR/MR 2022). The ML2 claims to have 2,000 nits with a much larger 70-degree FOV.
Transparency (vs. Birdbath) and “Eye Glow”
Transparency
As seen in the pictures above, all the waveguide-based glasses have transparency on the order of 80-90%. This is a far cry from the common birdbath optics, with typically only 25% transparency (see Nreal Teardown: Part 1, Clones and Birdbath Basics). The former Osterhout Design Group (ODG) made birdbath AR Glasses popular first with their R6 and then with the R8 and R9 models (see my 2017 article ODG R-8 and R-9 Optic with OLED Microdisplays) which served as the models for designs such at Nreal and Lenovo’s A3.
OGD Legacy and Progress
Several former ODG designers have ended up at Lenovo, the design firm Pulsar, Digilens, and elsewhere in the AR community. I found pictures of Digilens VP Nima Shams wearing the ODG R9 in 2017 and the Digilens Argo at CES. When I showed the pictures to Nima, he pointed out the progress that had been made. The 2023 Argo is lighter, sticks out less far, has more eye relief,is much more transparent, has a brighter image to the eye, and is much more power efficient. At the same time, it adds features and processing not found on the ODG R8 and R9.
Front Projection (“Eye Glow”)
Another social aspect of AR glasses is Front Projection, known as “Eye Glow.” Most famously, the Hololens 1 and 2 and the Magic Leap 1 and 2 project much of the light forward. The birdbath optics-based glasses also have front projection issues but are often hidden behind additional dark sunglasses.
When looking at the “eye glow” pictures below, I want to caution you that these are random pictures and not controlled tests. The glasses display radically different brightness settings, and the ambient light is very different. Also, front projection is typically highly directional, so the camera angle has a major effect (and there was no attempt to search for the worst-case angle).
In our AWE 2022 Video with SadlyItsBradley, I discussed how several companies, including Dispelix, are working to reduce front projection. Digilens is one of the companies I discussed that has been working to reduce front projection. Lumus’s reflective approach has inherent advantages in terms of front projection. DigiLens Argo (pictures 2 and 3 from the right) have greatly reduced their eye glow. The Vuzix Shield (with the same optics as the Ultralite) has some front projection (and some on my cheek), as seen in the picture below (4th from the left). Oppo appears to have a fairly pronounced front projection, as seen in two short videos (video 1 and video 2)
DigiLens Argo Deeper Look
DigiLens has been primarily a maker of diffractive waveguides, but it has, through the years, made several near-product demonstrations in the past. A few years ago, they when through a major management change (see 2021 article, DigiLens Visit), and with the management came changes in direction.
Argo’s Business Model
I’m always curious when a “component company” develops an end product. I asked DigiLens to help clarify their business approaches and received the following information (with my edits):
Optical Solutions Licensing – where we provide solutions to our license to build their own waveguides using our scalable printing/contactless copy process. Our licensees can design their waveguides, which Digilens’ software tools enable. This business is aimed at higher-volume applications from larger companies, mostly focused on, but not limited to, the consumer side of the head-worn market.
Enterprise/Industrial Products – ARGO is the first product from DigiLens that targets the enterprise and industrial market as a full solution. It will be built to scale and meet its target market’s compliance and reliability needs. It uses DigiLens optical technology in the waveguides and projector and is built by a team with experience shipping thousands of enterprise & Industrial glasses from Daqri, ODG, and RealWear.
Image Quality
As I was familiar with Digilen’s image quality, I didn’t really check it out that much with the ARGO, but rather I was interested in the overall product concept. Over the last several years, I have seen improved image quality, including uniformity and addressing the “eye glow” issue (discussed earlier).
For the type of applications in the “enterprise market” ARGO is trying to serve, absolute image quality may not be nearly as important as other factors. As I have often said, “Hololens 2 proves that image quality for the customers that use it” (see this set of articles discussing the Hololen 2’s poor image quality). For many AR markets, the display information is simple indicators such as arrows, a few numbers, and lines. It terms of color, it may be good enough if only a few key colors are easily distinguishable.
Overall, Digilens has similar issues with color uniformity across the field of view of all other diffractive waveguides I have seen. In the last few years, they have gone from having poor color uniformity to being among the better diffractive waveguides I have seen. I don’t think any diffractive waveguide would be widely considered good enough for movies and good photographs, but they are good enough to show lines, arrows, and text. But let me add a key caveat, what all companies demonstrate are invariably certainly cherry-picked samples.
Field of View (FOV)
While the Argos 30-degree FOV is considered too small for immersive games, for many “enterprise applications,” it should be more than sufficient. I discussed why very large FOVs are often unnecessary in AR in this blog’s 2109 article FOV Obsession. Many have conflated VR emersion with AR applications that need to support key information with high transparency, lightweight, and hands-free. As Professor and decades-long AR advocate Thad Starner pointed out, requiring the eye to move too much causes discomfort. I make this point because a very large FOV comes at the expense of weight, power, and cost.
Key Feature Set
The diagram below is from DigiLen on the ARGO and outlines the key features. I won’t review all the features, but I want to discuss some of their design choices. Also, I can’t comment on the quality of their various features (SLAM, WiFi, GPS, etc.) as A) I haven’t extensively tried them, and B) I don’t have the equipment or expertise. But at least on the surface, in terms of feature set, Argo compares favorably to the Hololens 1 and 2, if having a smaller FOV than the Hololens 2 but with much better image quality.
Most realistic enterprise-use models for AR headsets include significant, if not exclusively, hands-free operation. The basic idea of mounting a display on the user’s head it so they can keep their hands free. You can’t be working with your hands and have a controller in your hand.
While hand tracking cameras remove the need for the physical controller, they do not free up the hands as the hands are busy making gestures rather than performing the task with their hands. In the implementations I have tried thus far, gestures are even worse than physical controllers in terms of distraction, as they force the user to focus on the gestures to make it (barely sometimes) work. One of the most awful experiences I have had in AR was trying to type in a long WiFi password (with it hidden as I typed by asterisk marks) using gestures on a Hololens 1 (my hands hurt just thinking about it – it was a beyond terrible user experience).
Similarly, as I discussed with SadlyItsBradley about Meta’s BCI wristband, using nerve and/or muscle-detecting wristbands still does not free up the hands. The user still has their hands and mental focus slaved to making the wristband work.
Voice control seems to have big advantages for hands-free operation if it can work accurately in a noisy environment. There is a delicate balance between not recognizing words and phrases, false recognition or activation, and becoming too burdensome with the need for verification.
Skull-Gripping “Glasses” vs. Headband or Open Helmet
In what I see as a futile attempt to sort of look like glasses (big ugly ones at that), many companies have resorted to skull-gripping features. Looking at the skull profile (right), there really isn’t much that will stop the forward rotation of front-heavy AR glasses unless they wrap around the lower part of the occipital bone at the back of the head.
Both the ARGO (below left) and Panasonic’s (Shiftall division) VR headsets (right two images below) take the concept of skull-grabbing glasses to almost comic proportions. Panasonic includes a loop for the headband, and some models also include a forehead pad. The Panasonic Shiftall uses pads pressed against the front of the head to support the front, while the ARGO uses an oversized large noise bridge as found on many other AR “glasses.”
ARGO supports a headband option, but they require the ends of the temples with the skull-grabbers temples to be removed and replaced by a headband.
As anyone who knows anything about human factors with glasses knows, the ears and the nose cannot support much weight, and the ears and nose will get sore if much weight is supported for a long time.
Large soft nose pads are not an answer. There is still too much weight on the nose, and the variety of nose shapes makes them not work well for everyone. In the case of the Argo, the large nose pads also interfere with wearing glasses; the nose pads are located almost precisely where the nose pads for glasses would go.
Bussel/Bun on the Back Weight Distribution – Liberating the Design
As was pointed about by Microsoft with their Hololens 2 (HL2), weight distribution is also very important. I don’t know if they were the first with what I call “the bustle on the back” approach, but it was a massive improvement, as I discussed in Hololens 2 First Impressions: Good Ergonomics, But The LBS Resolution Math Fails! Several others have used a similar approach, most notably with the Meta Quest Pro VR (it has very poor passthrough AR, as I discussed in Meta Quest Pro (Part 1) – Unbelievably Bad AR Passthrough). Another feature of the HL2 ergonomics is the forehead pad eliminates weight from the nose and frees up that area in support of ordinary prescription glasses.
The problem with the sort-of-glasses form factor so common in most AR headsets today is that it locks the design into other poor decisions, not the least of which is putting too much weight too far forward. Once it is realized that these are not really glasses, it frees up other design features for improvement. Weight can be taken out of the front and moved to the back for better weight distribution.
ARGO’s Eye-Relief Missed Opportunity for Supporting Normal Glasses
Perhaps the best ergonomic/user feature of the Hololens 1 & 2 over most other AR headsets is that they have enough eye relief (distance from the waveguide to the eye) and space to support most normal eyeglasses. The ARGO’s waveguide and optical design have enough eye relief to support wearing most normal glasses, but still, they require specialized inserts.
You might notice some “eye glow” in the CNET picture (above right). I think this is not from the waveguide itself but is a reflection off of the prescription inserts (likely, they don’t have good anti-reflective coatings).
A big part of the problem with supporting eyeglasses goes back to trying to maintain the fiction of a “glasses form factor.” The nose bridge support will get in the way of the glasses, but the nose bridge support is required to support the headset. Additionally, hardware in the “brow” over the eyes could have been moved elsewhere, which may interfere.
Another technical issue is the location and shape of their optical engine. As discussed earlier, the Digilens engine shape causes issues with jutting into the front of glasses, resulting in a large brow over the eyes. This brow, in turn, may interfere with various eyeglasses.
It looks like Argo started with the premise of looking like glasses putting form ahead of function. As it turns out, they have what for me is an unhappy compromise that neither looks like glasses nor has the Hololens 2 advantage of working with most normal glasses. Starting from the comfort and functionality as primary would have also led to a different form factor for the optical engine.
Conclusions
While MicroLED may hold many long-term advantages, they are not ready to go head-to-head with LCOS engines regarding image quality and color. The LCOS engines are being shown by multiple companies that are more than competitive in size and shape with the small MicroLED engines. The LCOS engines are also supporting much higher resolutions and larger FOVs.
Lumus, with their Z-Lens 2-D reflective waveguides, seems to have a big advantage in image quality and efficiency over the many diffractive waveguides. Allowing the Z-lens to be encased without an air gap adds another significant advantage.
Yet today, most waveguide-based AR glasses use diffractive waveguides. The reasons include there being many sources of diffractive waveguides, and companies can make their own custom designs. In contrast, Lumus controls its reflective waveguide I.P. Additionally, Lumus has only recently developed 2-D reflective waveguides, dramatically reducing the size of the projection engine driving their waveguides. But the biggest reason for using diffraction waveguides is that the cost of Lumus waveguides is thought to be more expensive; Lumus and their new manufacturing partner Schott Glass claimed that they will be able to make waveguides at competitive or better costs.
A combination of cost, color, and image quality will likely limit MicroLEDs for use in ultra-small and light glasses with low amounts of visual content, known as “data snacking.” (think arrows and simple text and not web browsing and movies). This market could be attractive in enterprise applications. I’m doubtful that consumers will be very accepting of monochrome displays. I’m reminded of a quote from an IBM executive in the 1980s when asked whether resolution or color was more important said: “Color is the least necessary and most desired feature in a display.”
Not to pick on Argo, but it demonstrates many of the issues with making a full-featured device in a glasses form factor, as SLAM (with multiple spatially separated cameras), processing, communication, batteries, etc., the overall design strays away from looking like glasses. As I wrote in my 2019 article, Starts with Ray-Ban®, Ends Up Like Hololens.
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