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First, I just added a grammar checker to my computer which should help make this blog more readable. I tried it out in the last two articles, and it picked up a “few” (ok, if over 30 counts as few) mistakes. This blog has over 15,000 “active users” (as defined by Google Analytics), including executives at both small and large companies, and I would like to make it easier for them to read.
Attending CES is the proverbial drinking from a firehose. I had over 25 meetings in 4 days on the show floors and in hotels all over the strip, and from breakfast through dinner. This year I was mostly focused on Augmented Reality (AR) displays and optics with some look at automotive HUD and projection. Unfortunately, some of the best things I saw, I can’t talk about, and it is going to take some time to write up what I can discuss. I thought it would be best to start with a set of photos with some quick comments and then will write some more in-depth articles laters on some selected topics.
I’m going to try and just present the various things I saw at CES without many comparisons or deep analysis. I had to make a bit of exception for “diffractive waveguides” as there are so many of them and it is a major topic concerning Microsoft Hololens and Magic Leap. It was tempting to go into a discussion of the pro’s and con’s of the various optical solutions, but I will have to save most of that for another day as there is so much to cover.
Show below is waveguide maker Lumus’s demo headset with dual 40-degree FOV waveguides, each driven by a Raontech 1080p field sequential color LCOS device. The headset is mocked up to look similar to Hololens, and there are no functional cameras, sensors, or computers in the headset. There is plenty of eye relief to wear over glasses, and you easily see the wearer’s eyes. The waveguides are over 80% transmissive of real-world light to the eyes. Additionally, with the “top shooter” design, it leaves the user’s peripheral vision to the sides and down unobscured.
Their image quality appears to be significantly better than diffractive waveguides. But I must caution that Lumus was only showing limited demo content, and I did not have the time nor opportunity to try test patterns that might catch problems. As I warn my readers, usually demos on a show floor are tested to show content that makes them look good and avoid content that highlights issues.
While the 40 Degree 1080p waveguide garnered the most attention in the Lumus booth, they were also showing their lower cost and lower resolution “side-shooter” designs along with a sleeker design concept. This design trades resolution for cost, weight, and smaller size. It blocks more of the user’s peripheral vision but not that much more than a pair of sunglasses with a large frame.
Lumus makes the optics and attaches the displays, the rest of the system is up to their OEM customers, so their prototypes are only mockups. The next company I am going to discuss, Vuzix, makes both the optics and the end product.
Vuzix represents perhaps a more practical, stylish, and end equipment business-oriented approach to waveguide glasses. Vuzix has dropped all pretext of using them for watching movies and is demoing text and simple graphics content. It is monocular (single eye display) aimed at providing basic information to the user.
The Vuzix Blade uses a diffractive waveguide custom made by them. Like Lumus, it transmits more than 80% of the real-world light to the eyes. The overall image quality suffers from being a diffractive waveguide, and there are noticeable color variations across the field of view; something that is inherent in all diffractive waveguides including Hololens and should be expected in Magic Leap’s if/when it comes out (so I am not just picking on Vuzix).
To begin with, they move the lenses so close to the eye that they require prescription lenses which is both a pro and a con. With the lenses worn closer to the eye, it put less weight on the person’s nose, as well fitting better and more comfortably. They have (only) a WVGA (854×480) DLP display that is portrait mode (long side running vertically) to allow them to move the image vertically in the user’s view to better position the location of the image. They can, with the DLP, make the image very bright (more than 3,000 nits) as needed for outdoor use. The Blade is wirelessly connected to the phone or computer system and will run for about 1 hour with the display on continuously or for about 8 hours of “typical” intermittent use.
Vuzix is trying to build a product to fit their customer’s needs. They are going to lose out spec and image quality wise to other people trying to make the best demo. The Blade is much more of a complete product and not a mock-up to show what they can do.
WaveOptics invited me to their suite to see their latest work in diffractive waveguides made of both glass and plastic. They were shooting a “top shooting” design running with a mocked-up set of glasses for how it will look in a more finished product. Like They are a waveguide component and not a whole system maker. One thing that makes WaveOptics stand out a bit is that they support both glass and a lower cost plastic waveguides whereas most other waveguide makers only use glass (which can be laminated for safety). WaveOptics claims to have made advances that allow their waveguides to be canted/angle to better wrap around a person’s head like normal glasses.
The picture (left) does not show the image as it very tricky and time-consuming to get a picture from a waveguide that looks anything like what you see with your eye. They also had several mockups of how their waveguides look in a finished product. It is also impossible to objectively compare the various waveguides when you have different setups and different content. I can say that I saw the “typical” diffractive waveguide issues (color uniformity across the field and “waveguide glow’), but not it was better or worse than any other diffractive waveguide.
Another Diffractive Waveguide maker is DigiLens. They use a “frozen LCD” process to make their diffraction gratings. I did not see them at CES (due to a mistake on my part), but I did meet with them at Display Summit in November and saw their technology. Digilens is in the process of coming to market with consumer products for bicycle and motorcycle use.
As I wrote concerning the other diffractive waveguides, it has similar advantages (thin and reasonably transparent) and image issues associated with diffractive waveguides.
I have seen many diffractive waveguides including Microsoft Hololens and the ones above and I’m sorry to take this aside but, this must be said. The same principles of physics that make waveguides work, the bending of light based on wavelength, is the source of their downfall when it comes to image quality. There are additional problems in that the image light must bounce many times across the waveguide exit grating and on each encounter with the exit grating the image quality is degraded.
Each manufacturer has their own “tricks.” Hololens uses Nokia’s slanted Waveguide, Vuzix started with Nokia’s slanted waveguide but have developed their own method, Digilens uses UV-frozen LCD, and Magic Leap, based on their latest papers and patents may be using dual nano-beams. But the fundamental principle of using a diffraction grating is all the same. The tricks may reduce some of the negative effects, but they can’t eliminate them.
Diffractive waveguides may be used to make useful products within their limits. They are thin, light, and usually, have good light transmission (often greater than 80%). They support the “look” of glasses. Companies appear to be getting better at manufacturing them, so costs should keep coming down. For making low-resolution basic information and “data snacking” diffractive waveguides such as Vuzix is doing, diffractive waveguides might very well be useful, but they are never going to have great image quality as objectively measured.
Note, Lumus with their partial mirror-based waveguide is in a different category as they don’t depend on refraction. They may have other optical issues (I have not had the chance to evaluate them). Their diffraction waveguide competitors suggest that Lumus waveguides are much more costly to make, but as I can’t get reliable cost data from any of the companies, this is impossible to prove one way or the other.
LetinAR is small Korean startup that has clear optics with “pin mirrors” embedded it that look like one or more dots in the clear material from far away. Their multi-pin-mirror 70-degree element is shown in the picture at left. The physics would seem to be related pinhole cameras and to the University of North Carolina’s Pinlight Display, but LentinAR uses larger and fewer pin mirrors. LetinAR makes their optics out of both glass and plastic.
The fascinating thing about their technology is that while it seems very simple, the resultant image light has a very high “f-number” which results in the image being in-focus regardless of where your eye is focused, and also a result, the image is very sharp. Their Pin Mirror optics are acting on the light in a very different way than any of the waveguides.
In my discussions with LetinAR, I was never able to understand the display light throughput of their system. One would expect a high f-number optical system to have low efficiency due to throwing away most more diffuse light. But then they showed it using an OLED which can not supply that much light and claimed to be reasonably efficient.
They support a ~40-degree FOV with a single pin-mirror and then add pin-mirrors to increase the FOV. The user’s eye must be relatively close to the pin-mirror for it to work and they will require prescription lenses for a person that uses glasses. Perhaps because of the pin mirror’s focus, they will only need the lenses to correct the user’s view of the real world (I’m not sure, particularly concerning astigmatism).
On their 70-degree FOV optics with 15 pin mirrors, I noticed some distortion/misalignment as my eye was viewing one pin mirror to the next. LetinAR assured me that this was due to this being an early prototype and they need to improve their manufacturing tolerances.
In Lumus’s booth and demonstrated with a Lumus waveguide was an electrically controlled, variable focus lens by Deepoptics. Waveguides, both Lumus semi-mirror-based and diffractive, required collimated (focused near infinity) light to work was a waveguide. As explored in my prior articles about Vergence Accommodation Conflict (VAC), to support VAC the focus of the light must change on or after the light exits the waveguide.
Deepoptics uses a phase modulated liquid crystal sandwiched between optically transmissive control plates. In their current demo, they did not have any eye tracking to control the focus as would be required for a working VAC system, but they did demonstrate that they could electronically control focus.
Because it must be between the output of the waveguide and the eye, changing the focus of the display image would also affect the real world focus. Deepoptics demonstrated using a polarizer on to polarized the real world light to the opposite polarity of the display’s light. In this way, their adaptive lens would only change the focus of the display’s light. But this does mean negating the >80% see-though advantage of Lumus and other waveguides.
An alternative approach that would block less light would be to have an adaptive lens on both sides of the waveguide; the inner adaptive lens would correct for VAC, and the outer adaptive lens would undo the correction for the real-world. But how well dual corrective optics would work is yet to be seen.
Raontech is a maker of LCOS microdisplays, and they had a significant presence in the AR area of CES this year. In addition to their booth, their LCOS devices could be found in Lumus’s 1080p demo as well as Mad Gaze and ThirdEye.
Raontech is currently shipping two different sizes of 720p field sequential color LCOS displays. One is smaller and less expensive and the other, used Mad Gaze, and ThirdEye is larger and more costly but makes for better image quality with simpler optics. Lumus was using Raontech’s 1080p display, and Raontech was demonstrating a Quad-HD (quad 720p or 2560 by 1440 pixel) device they recently developed.
Both Mad Gaze and Thirdeye appeared to be using the same optics that Raontech had developed for their panels. While the optics use a “birdbath” design (see my article on birdbath optics), the curved mirror is on the bottom rather than in front. This configuration results in significantly more real-world and display light getting through to the eye than say last year’s Osterhout Design Group’s R-8 and R-9 with the curved combiner in the path to the real world. Optically, Raontech’s design is very similar to Google Glass only scaled up and rotated 90 degrees. The image quality is relatively good, but is still blocks about 60% (before any additional tinting is added) of the real world light and polarizes it.
The Raontech design gives reasonably good eye relief so you can wear it over a person’s glasses. But this also means the lenses and optics are further away which puts more of weight on a person’s nose and looking bigger overall. These are just the type of design trade-offs that are made
Because it is a birdbath with a beam splitter, the optics are bulky. Thirdeye said that they are looking at other optical designs for their future products. ThirdEye’s design looks bulkier than Mad Gaze due to the larger batteries built into their design, a classic trade-off of battery life versus looks.
Meta 2 seems to be the one that started a trend of using a large flat panel display with dual large spherical combiners, what many are calling “bug-eye displays” for obvious reasons. In particular, I came across Dreamworld (one of the founders of which came from Meta), Real Max, and Mira using bug-eye optics.
The bug-eye approach with either an LCD or OLED flat panel (either dedicated or using a phone’s display) has to be about the least expensive way make a near-eye display with reasonably good display image quality. The downsides include it being big and bulky, blocks most (usually well more than 50%) percentage of the real-world light. You will see a blurry zone where the two spheres meet in the middle; it is only bright enough for indoor use, it blocks the view of the user’s eyes. Additionally, it makes the user look like well . . . , a giant robot insect.
Next time I plan to cover information related to Micro-LEDs and Heads Up Displays (HUD) for automobiles. In the future, I also plan on going into more detail some of the topics and devices I only briefly addressed in this article.