Introduction – I was almost done, and then . . .

Since starting this blog, I have been interested in AR optical designs that are different from others I have seen. When Xreal showed their Xreal One Pro at CES 2025, I was curious to know how it worked. As it turned out, the design was not as different as I had first thought. I had seen it before but didn’t realize it until I was well into writing this article. I did one last search through my files, and as my British friends say, the penny dropped (it clicked), and I had a bit of a different story to write.

According to IDC (as shown by Xreal), Xreal has shipped over half a million AR Glasses to date and had about 47.2% of the “AR Market” in 2024 (see data from Xreal’s presentation at AR/VR/MR 2025, right). As will be discussed toward the end of this article, Xreal is going after applications that are more “VR-like” than what people classically think of as Augmented Reality. Xreal’s birdbaths block about 75% (25% transmissive) of real-world light, and the One Pro blocks about 78% (22% transmissive in its most transmissive state of the integrated dimmer) or are like dark sunglasses. The Waveguide and other nearly clear (>80% transparent) AR glasses.

Background

I have been covering Xreal (then named Nreal) since CES 2019. Xreal design was very similar to ODG’s R-8 and R-9 designs, which I covered in 2017 (see: ODG R-8 and R-9 Optic with an OLED Microdisplays (Likely Sony’s)). Since 2019, I have covered Xreal many times, including a 2021 teardown of (then) Nreal’s birdbath design (see: Nreal Teardown: Part 1, Clones and Birdbath Basics, Nreal Teardown: Part 2, Detailed Look Inside, and Nreal Teardown: Part 3, Pictures Through the Lens).

Then there is Ant Reality (formerly named AntVR), which I first saw at AWE 2018, then CES 2020, and covered in a 2022 AWE video with Brad Lynch. It has been reported that Google acquired Ant Reality in December 2023, but the exact nature of that “acquisition” of a Chinese-based company has not been reported.

My coverage of Google and AR goes back to the early days of this blog (see 2012’s Google Glass and Himax Whirlwind, Augmented Reality / Head Mounted Displays (Part 1 Real or Not?), and Augmented Reality and Google Project Glass Part 2). This blog caused quite an uproar and over $100M movement in a day in Himax’s stock when I identified a Himax LCOS panel in Google Glass (Google Glass and Himax Whirlwind). I have also written about Google’s crazy spend of $500M on Magic Leap that enabled them to raise over $2B more (see, for example, 2020’s Magic Leap Starts to Auger-In with ~3.7X the Money as Theranos – I Tried to Warn Everyone).

Xreal One Pro at CES 2025

Xreal was showing their new One Pro at CES 2025 in preparation as part of a product launch for shipping in March 2025. While all prior Xreal (or Nreal) devices used a birdbath architecture, the new One Pro was using what Xreal called a “flat prism.” At first, I thought it might be a typical “freeform optics” (more on this later), but on closer examination, it was obviously not a common freeform.

Xreal had all the parts of the Xreal One Pro in a glass box with a light underneath (right). I was able to get a close-up of the optic module at an angle (seen later). The parts view also clearly shows the two polarization-based dimmers.

The One Pro’s “Flat Prism” optics are much thinner, allowing the user’s eyes to get closer to the optics. This will, among other things, mean the One Pro does not have to sit so far out on the user’s nose, which will help keep the glasses from being as front-heavy. As will be discussed later, it also improves the field and effective magnification. The Xreal one has a larger FOV even though it is using a new, smaller Sony 1920×1080 Micro-OLED, which Xreal attributes to their new “Flat Prism” optical design.

Ant-Reality

I first saw Ant-Reality (then named AntVR) at AWE 2018 (below left), and they were not that impressive. However, by 2023, they had a moderately large and well-attended booth at CES 2023 (below right). But then, by December 2023, it was reported that Google had acquired Ant-Reality, so I figured it was the last I would see or hear of them.

I started finding AntVR’s (aka, Ant Reality) technology interesting at CES 2020 (below left). But they seemed to improve massively by the time I got a demo of Ant Realities 120° dual display Crossfire (below right) at AWE 2022 (see my video report).

One thing to notice in the AntVR 85° design above is that the (in-air) polarizing beam splitter does not extend to the top and bottom of the optics/FoV. While this “works” for displaying the image, it results in a darker (out-of-focus) band in the center of the real world (less so in the virtual image) and out-of-focus lines at the top and bottom of the beamsplitter. This will be important later when looking at the concept diagrams for the Xreal One Pro.

The Crossfire design works by using a total internal reflection (TIR) of the display’s light into a polarizing beam splitter at a shallower angle than a common birdbath’s ~45° beamsplitter. Because of the angle from the TIR bounce, it is still “on-axis” with the spherical birdbath mirror. Crossfire has two prisms and displays that are combined to make a single 120° image. However, this same concept with the TIR bounce can be applied to a single display and prism.

Another thing to notice in the Crossfire figure is the front projection of the image, which happened to be a test pattern from this blog. This image is polarized, and Nreal/Xreal (among others) have eliminated this front projection from their birdbath designs using a front polarizer (see my Nreal teardown).

Similarly, LetinAR has used a single TIR (versus a waveguide’s massive number of TIR bounces) in a spherical collimating mirror in their PinTilt design (above right).

Xreal 2025 AR/VR/MR with the same figures as Ant-Reality at 2023 AWE

At CES 2025, I started to wonder about the Xreal One Pro’s light path/optics, but with all the running around, processing photographs from CES, and then preparing for AR/VR/MR 2025, I didn’t get much of a chance to think about it. A couple of weeks later, I showed the design to some people at AR/VR/MR, and it became obvious that it was not freeform optics, and I had already ruled out a “bottom-ended birdbath” (like Google Glass – more on this later).

On the last day of the AR/VR/MR, Xreal presented on the One Pro and gave a very general diagram of the “Flat Prism” optical path (below left). It showed the display device (in yellow and orange) could be in any of four general locations, and it looked much thinner than what I had taken a picture of at CES (below right).

I eventually sorted out how to get the optical path to work with the various pictures I took of the One Pro’s optics. But I kept thinking that it must be something like a cross between the AntVR 85° and Ant Reality Crossfire. Then, like in the ending of MGM’s Wizard of Oz (where Dorothy is told she had the power to go home all along), I rediscovered Ant Realities slides from AWE 2023 that they had given me.

I was surprised to find four diagrams in Xreal’s 2025 presentation (upper set of slides below) that were identical to diagrams in Ant-Reality’s 2023 presentation (lower set of slides). Most interesting are the far right figures, which Xreal calls a Flat Prism, and Ant-Reality called a “Mixed Waveguide.”

If you look closely at the figures above, you will see that the Freeform prisms tilt in the opposite direction as the birdbath and Mixed Waveguide=Flat Prism. With a Freeform, all the virtual image light that reaches the eye stays in the eye-side prism. The second prism, known as the compensator, is used to keep the wedge-shaped freeform from distorting the real world. At CES 2025, P&C Solutions was showing Metalens 2, which used freeform optics (right), which, while less common today, is one of many headsets I have seen using freeform optics through the years.

Ant-Reality’s/Xreal’s diagrams above seem to overstate the advantages of the “Flat Prism.” For example, they show a distorted image due to freeform optics being off-axis of the semi-spherical mirror. Usually, there are “pre-correction” optics (left) that can help correct this issue. As will be shown later, Xreal’s Flat Prism also has a lens integrated into it, which is not shown in the diagrams above.

Ant-Reality’s AWE presentation included a video, and the still frame below shows their “Mixed Waveguide” prototype optics, which look a lot like the Xreal One Pro (below).

Connecting Xreal, Ant-Reality, and Google/Android XR

So, Google has (reportedly) “acquired” Ant-Reality (aka AntVR), but the form of the acquisition is unclear. A quick look at the U.S. Patent Office assignment still shows the patents and even new (ex. US 2025/0028176) applications assigned to “BEIJING ANTVR TECHNOLOGY CO., LTD. (Beijing, CN)” rather than to Google or an obvious subsidiary.

Xreal’s use of the same figures as Ant-Reality suggests Xreal’s “flat prism” based on Ant-Reality’s optical design. Xreal was also at the announcement of Google’s XR Unlock and the Announcement of Android XR (below left). Additionally, Xreal prominently featured their work with Android XR in their AR/VR/MR presentation (below right). I don’t know the exact relationship between Google and Xreal, such as a possible investment by Google in Xreal (a web search didn’t show any). Still, apparently, whatever is going on, it is a friendly relationship😁.

Xreal One Pro’s optics “concept” diagrams

Since I had better copies of Ant-Reality’s slides than the pictures of Xreal’s slides and the figures were identical, I’m using the Ant-Reality concept diagrams to explain how the Xreal Pro Optics work (right). These concept diagrams leave out components to show the basic idea. I have added some annotations in red.

I have lined up the birdbath diagram (top right) with the “Flat Prism” diagram (bottom right). While not to scale, a key point is that the eye can get closer to the curved mirror. The main reason is that the beam splitter no longer has to be 45 degrees due to the angle at which the light hits it after the TIR reflection.

The Xreal One Pro diagram “cheats” by making the optics much thinner, making the view distance appear much shorter. In the concept diagram, the PBS does not extend the full height of the FoV, which would cause the image to be darker in the center and with out-of-focus lines at the top and bottom of the PBS. As will be seen, the actual One Pro optics are much wider, I presume, to eliminate this obvious problem (and one I saw with the AntVR 85° at CES 2020).

Having the eye closer to the optics supports more magnification of the display’s image and enables a wider FOV.

For the TIR to work, they must have solid optics, whereas the birdbath can be in the air, thus tending to make them heavier even if they are smaller. To enable the TIR, there is an Air gap between the PBS prisms and the curved mirror. Both the conventional birdbath and the One Pro have a quarter waveplate in front of the curved mirror in order to rotate the polarization 90 degrees and thus pass through the polarizing beam splitter (PBS) on the return path to the eye.

Every birdbath design I have seen has some lenses before the PBS, but they are not shown in the birdbath diagram above (other than the “field lens” I added in red). The One Pro also has a lens that is not shown in the simple figure above. See the figure (right) from my 2021 teardown of the Nreal (aka Xreal) birdbath for the difference between the high-level concept above and the actual design of a birdbath. Similarly, the conceptual Xreal One Pro diagram above leaves out necessary components.

As pointed out in Xreal’s slide in their AR/VR/MR presentation, the design shown is “on-axis,” which results in less geometric distortion.

The Actual Xreal One’s Optical Path

The figure (below left) uses the concepts from the diagram of One Pro’s theoretical optics and applies them to the pictures of the actual optics. Xreal had a somewhat side view of the prism (bottom right) that is covered up by the frame and Micro-OLED display in all the pictures of the optics (including upper right). As can be seen, there is a lens molded into the top of the prism that forms one side of the PBS. From the view of the prism in the presentation, I (by hand) created a side view diagram and overlaid it on a picture I took of the One Pro.

The curved spherical (or semi-spherical) mirror is not clearly visible, so I used the one from the diagram shown earlier for the side of the diagram (it shows the function but not the right size and curvature). This diagram roughly shows the light path and is not a perfect model. The diagram shows polarizers and a quarter waveplate (QWP), which must be used for the optics to work.

An obvious difference from the theoretical diagram is that the PBS and the two prisms on either side extend the full height of the possible view through the optics. This avoids the non-uniformity issues with a short beam splitter discussed earlier. To make this happen, the two main prisms are significantly wider.

Another major difference between the earlier theoretical diagram and the actual One Pro’s optics is their significant pantoscopic (top to bottom) tilt (shown right). In contrast, in the conceptual diagram shown earlier, there is no tilt. While I am not sure, I wonder if everything is still “on-axis” with respect to the spherical mirror. Note also that in the prism from the Xreals slide, a lens element is molded into the top of the prism. This lens might also be pre-correcting for off-axis issues.

Polarizing Dimmer

The Xreal One Pro has a polarization-based dimmer that blocks almost 100% of real-world light to create a black background for better image viewing. A polarization dimmer works by putting a liquid crystal cell between two polarizers. The dimmer’s polarizer nearest the glasses will prevent the front projection of light from the curved (non-polarized) semi-mirror, as seen in the Ant-Reality Crossfire shown above.

As discussed earlier, even in its most transparent state, the Xreal One Pro only lets through about 22% of the real-world light or about as much as dark sunglasses. Xreal has prioritized seeing the virtual image at the expense of seeing the real world.

Xreal Application Space – Closer to VR with Passthrough

My discussion at CES 2025 with Xreal CEO Chi Xu helped me better understand Xreal’s market. With ~22% transparency in the best case, it has a very different application space than waveguide and other nearly clear (>80% transparency) AR glasses.

I’m fond of saying that AR (optical see-through / OST) glasses prioritize clearly seeing the real world and, to some degree, sacrificing the image quality of the virtual world. VR with video see-through (VST) prioritizes the virtual image, and the video see-through is to augment the virtual world. In particular, the VST is generally only good enough to let someone see things in the room to pick them up or to keep from bumping into things. By these standards, Xreal’s application space is closer to VR than the nearly clear AR glasses.

Perhaps the most obvious use case for Xreal’s glasses is ultra-portable displays, such as when commuting on public transport. In these cases, seeing the real world is more for situational awareness rather than to overlay a small amount of virtual information on the real world.

According to Xreal, one of its biggest applications is a big FOV display for handheld virtual reality games such as the Steam Deck (above left).

Another application space for Xreal is a head-worn computer monitor, something I started working on in 1998 (right). Sightful, among others, has been using Xreal glasses to support multiple large virtual monitors. Originally, Sightful developed a “monitorless laptop.” Sightful has transitioned to being purely a software application running on other companies’ laptops using Xreal for a private large FOV virtual multi-monitor. (left).

For most of Xreal’s applications, they want the best possible image quality, which means needing to black out the real world. Thus, the electronic dimming shutter on the Xreal One Pro.

Based on how the Xreal glasses are being used, their newer One and Pro One glasses improve head tracking latency by moving 3 Degrees of Freedom (DoF) tracking from a software application running on a smartphone or laptop to their new X1 chip. In games and virtual monitor applications, it is important to respond quickly to head movement.

Conclusion

The funny thing is that if I had not been trying to figure out how it worked, I would never have stumbled across some old information that showed apparent connections between Xreal, Ant Reality, and Google.

In the end, it is a slightly more complex version of a birdbath, where the optics are encased in plastic. The use of a TIR bounce enables the beam splitter to be somewhat thinner. The thinner beam splitter results in the eye being closer to the spherical mirror, which enables using a smaller display device while providing a larger FoV.

My discussion with Xreal CEO Xu helped me better understand the application space for an “AR” headset with so little transparency in its more transparent state. It’s almost easier to think of Xreal’s glasses as very lightweight VR glasses as an alternative to Meta Quest 3 or Apple Vision Pro, where the passthrough is optical, rather than highly transparent AR glasses.

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