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Part 6 of the KGOnTech and SadlyItsBradley discussion of AWE 2022 is now available on the KGOnTech YouTube Channel. Part 6 primarily covers MicroLED technology for augmented reality. In addition to discussing the companies showing their AR headsets using MicroLED displays at AWE, market and technical issues surrounding MicroLED microdisplays are discussed.
A few discussions were moved around group together discussions around a single topic in the editing process. Bradley of SadlyItsBradley and I recorded almost 7 hours of video (pre-editing) about AWE 2022. The recordings have been broken down into 7 parts. The first three parts were release on SadlyItsBradley and KGOnTech is releasing parts 4 through 7. The final part 7 will primarily cover Magic Leap 2.
These videos were to some degree targeted at SadleyItsBradley’s audience which is more VR headset focused and may have less knowledge of technical issues associated with see-through optics. The links to the various videos with their tables of contents (including chapter links) so people can more quickly access topics of their interest.
Most of the giant companies in AR are “voting with their wallets” that MicroLEDs microdisplays are the AR display technology of the future. Apple, Meta (aka Facebook), Google, Snap, and (not so giant) Vuzix have either bought outright or secured exclusive deals with at least one MicroLED startup. Microsoft is the only one of the giants in AR that I have not heard of buying a MicroLED company, and I can only find a small number of patents related to MicroLED microdisplays and waveguides (including application 20200271932).
The big question is whether all the publicity and money is justified or is it just a case of the “grass being greener” with relatively new display technology. The headlines grabbing performance numbers are about the “millions of nits.” But questions remain about manufacturability, producing full color, and perhaps most importantly power efficiency. While MicroLEDs have potential, I discusses some of the pros and cons of MicroLED microdisplay in AR. I specifically discuss some of the key efficiency issues MicroLEDs have working with Waveguides. So I didn’t dive too deep into topics like etendue.
The video goes on to discuss AR headsets from Snap, Oppo, Cellid, and Vuzix plus MicroLED based Mojo Vision contacts. We discussed relatively recent posting of Jade Bird Display’s color X-Cube using three-chip (R,G, & B) MicroLEDs.
A “Bonus Discussion” at the end groups together some of the issues with MicroLED manufacturing.
Porotech, a MicroLED startup (founded in 2018) in the UK, will also be mentioned a few times. At the time we were recording the video, I was about to travel to the UK, where was to meet with Porotech. I want to add some additional information on Porotech that I learned since the video was recorded.
Porotech has publicly demonstrated at several conferences, as well as to me in their lab, so they are not just some “paper tiger.” Chris Chinnock of Insight Media has a short summary video from a public showing in May 2022 and a white paper on the technology.
Porotech is in some way going for the “Holy Grail” display devices by having a single diode/emitter for all colors. The instantaneous current controls the diode’s color, and the brightness is controlled by pulse width. Porotech also claims that they have better electron-to-photon efficiency, particularly for red than single-color-per-diode technologies.
The use of a single emitter has multiple major technical advantages. It can have smaller pixels since there is only one emitter, and it can be optically more efficient since the light can emit from a smaller pixel area (better etendue). Additionally, there is only one pair of signals to drive per pixel versus three pairs with single-color diodes so there are 1/3rd the connections to make when marrying the diodes to the CMOS drive electronics, which should improve yields and reliability.
A few words of caution: Controlling the two-wire connection for both current to choose the color and pulse width is significantly more difficult than controlling a single color diode, and Porotech has the images statically wired into the demonstration devices (analogous to a segmented display – the demo butterflies on right change color but the shapes are the same). Porotech is still working on tuning/optimizing the wavelengths for the various colors. And of course, as a startup, Porotech has a long way to go to commercialize the process. Regardless, I think they deserve special mention because A) they are publicly demonstrating their single emitter for all colors technology, and B) they seem to be working on some of the key fundamental problems of MicroDisplays.
Porotech claims their “porous gallium nitride” has broad application in GaN beyond just LEDs.
After making the video, I met with Lumus and discussed their efficiency with MicroLEDs. At 07:05 in the video on WaveGuide Efficiency Problems, I was broadly discussing waveguides but primarily considered diffractive waveguides. Lumus pointed out to me that their light entrance area with a Lumus-type reflective waveguide is much larger and thus would have fundamental efficiency (etendue) advantage of several times and perhaps 10x. Lumus did not say whether or not they are working on a MicroLED-based engine to go with their waveguides. Lumus is currently making waveguides that output thousands of nits to the eye using LCOS microdisplays.
Table of Contents:
Below is the table of content for the video with time links to the start of the specific chapters:
Below is the table of contents of the Part 4 video on KGOnTech and covers the headset companies (less Magic Leap) I visited at AWE 2022.
The first three videos can be found on SadlyItsBradley YouTube site with links below:
The slide presentation video format let me cover content that would have taken many blog articles and many months to write versus a couple of weeks to generate the content, record, and edit. It seems like the best way to cover so much content on so many different companies and technologies. I would appreciate your feedback on your interest in more blog articles versus videos.
I would also like to find a good format for questions and answers (perhaps a live session on YouTube). I’m thinking it would be best to have at least some of the questions in advanced so I can have pictures and diagrams ready.
Please leave your comments below or on the YouTube video.
Great videos with lots of interesting bits information! The video format is nice, the only downside is, that it is harder to find information later on.
One question regarding efficiency and brightness for AR: What do you think is more important? What is the minimum brightness that has to be achieved to be “good enough” for a consumer/professional device to shift the development focus fully on battery lifetime (and lower heat). I would assume here, that shaded glasses (Hololens, Magic Leap) will never see wide adoption outside people working in the desert 😉 This will of course push the required brightness up quite a bit.
Yes, there are pros and cons to every media. There was just so much to talk about that it would have taken forever to write up and so I thought I would give video a try. I tried to give an extensive chapter list to help users find specific topics in the video.
A big problem for AR is that everybody seems to want everything. Also, a major issue in terms of power is the FOV. For the same brightness, the power is typically worse than the difference in area. So if you double the linear FOV, you more than quadruple the power.
There are no great answers as to what is enough brightness. I will say that even with some form of dimming (active or static), I think you need more than 2,000 nits and more like 4,000 nits to be “workable” outdoors in daylight. So if you can’t support more than 2K nits, you are confined to indoor and night (or shade if very shady) use outdoors. Unless you have that many nits, you just can’t deal with the dynamic range of outdoor use. That said, just blasting out the eyes has diminishing and perhaps painful returns. As I remember it, a typical built-in automotive HUD has about 15-17K nits which is probably not something you would want to look at for a long, but is necessary to see barely see text against sunlit concrete.
Hololens 2 has a peak (center of the display only) brightness of about 500 nits (so much for lasers being bright). Magic Leap 2 is claiming 2,000 nits so I think that are right on the line for outdoor use (probably not an accident). Lumus’s waveguide technology is inherently about 3 to 10 times more efficient depending on the display source and a dozen other factors so they are getting in the 4,000 nit range at 50 degrees (with about 1W per eye). For reference the nReal only outputs about 120 nits to the eye but consumes almost 1 Watt per eye.
As I have said and you suggested, a bigger issue than battery life will be heat dissipation. It starts getting hard to remove more than about 1 Watt per eye if you have relative small glasses (with gigantic semi-helmets like Hololens and Magic leap you can dissipate more)
They can’t currently come close to meeting all the requirements with today’s technology (Lumus seems closest in a waveguide form factor). So they are left making different trade-offs. To be used outside they need at least 2,000 nits so they will make the “helmet” big enough to deal with the heat and battery life.
[…] in general, as well as JBD and the glasses using their MicroLEDs, there is my 2022 blog article AWE 2022 (Part 6) – MicroLED Microdisplays for Augmented Reality and the associated video with SadlyItsBradley. Additionally, there is my 2021 article on JBD and […]