Hololens 2 First Impressions: Good Ergonomics, But The LBS Resolution Math Fails!

Update Feb 28, 2019

  • Updated that Microsoft is using 3:2 aspect ratio
  • A report from some that used a Hololen 2 that they saw flicker on the outside of the image(as I predicted).
  • Blog Down for 20 Hours thanks to lousy bluehost customer service (see rant at bottom)

Hololens 2 Announcement Feb 24th

As Expected, the Hololens 2 (HL2) was announced at Mobile World Congress (MWC) in Barcelona on Feb 24th, 2019. As I reported last time prior to the announcement, HL2 it is using Laser Beam Scanning for the display device. We also got quite a few details, some good, some not so good, and some “fibs” to put it generously.

The announcement was streamed and is now on YouTube (the key information on the HL2 starts about 23 minutes into the over 1-hour presentation with Alex Kipman). Additionally, for this article, I used some pictures from Microsoft as well as CNET and The Verge articles which are labeled accordingly. I relied primarily on the information from the above sources on the HL2 for my comments below.

Much Improved Human Factors – “Hololens 2 makes the Magic Leap One Look Like a Poorly Designed Child’s Toy”

HL2 Optics Flip Up

The best thing I saw was the much improved human factors of the helmet design. It looks to me like they went for functionality over looks or messing up the person’s hair. I suspect there will be a name for hair that gets smooshed down in the front, but it beats having it hurt when you wear it for a long time. Last month I even commented that NReal should adopt the configuration of putting the compute- pack and battery on the back of on some form of a cap which would result in a similar configuration.

I also very much like the flip-up of the optics what work like a Magnifying Glasses Headset. or a welding helmet. It is good to be able to get the display totally out of the way without having to take off the headset and find a safe place to put it.

Keeping the compute-pack and battery on the head means there is no cable to snag or catch. They maintain enough eye relief that most people will be able to wear ordinary glasses a huge plus for realist use cases. The design is relatively open an does not block the users downward or peripheral vision.

Another big factor to me is that the HL2 appears to be about 70% transmissive but this is a very rough estimate. Note in the picture on the right how you can see the person’s eyes, something you can’t do with the Magic Leap One and I have been critical about with the ML1. Not only do humans want to see another person’s eye, but it is a very important safety issue. I don’t think qualifies as ANSI “Transparent” (requires 85% transmissive) from the pictures I have seen so far. And if it did meat ANSI Transparent, I would think Microsoft would say so.

In terms of practical human factors, the Hololens 2 makes the Magic Leap One
(ML1) look like a poorly design child’s toy. It looks to me that the ML1 went for style over substance, where the HL2 focused on utility. The HL2 is vastly more practical than the ML1 including you can wear ordinary glasses, flip-up so you can get the optics out of the way without having to take the headset off, no cord to snag, much better peripheral vision, many times more see-through, as well as automatic IPD adjustment based on pupil tracking and about 1.5X the display brightness (more on these later).

Hololens seems to have more than doubled down on gesture recognition. The first generation’s gesture approach was an ergonomic nightmare that would leave your arm sore and pulling your hair out just to input a long WIFI security code. The videos make it looks like the gesture recognition is much improved, but the proof will be when we get to use it on a regular basis.

HL1 Spec’ed at 500 Nits – Good Not Great

First, it is interesting to see nits (common name for candelas per meter squared or cd/m2) being discussed. Usually, nits are not discussed. As I am fond of saying, “when a spec is not given by the manufacturer, the number is usually not good.” In fact, if you Google “Magic Leap Nits” this blog is currently the first hit because Magic Leap does not like to talk about it. I found that the ML1 outputs comparatively dim 210 nits where the first Hololens output about 350 nits. By way of contrast, Lumus which likes to talk nits claims 7,000 nits (yes more than 10X more than the H2) with their new Vision 1080 design.

I have heard that Hololens went to lasers for brightness but this makes no sense. Lumus is getting 7,000 nits with LCOS, Vuzix Blade is >1,000 nits using DLP with a similar diffractive waveguide, where the HL2 is only 500 nits. One should also be concerned as to the scalability of the brightness for eventual outdoor use (say with the Hololens Military Contract) with laser scanning as I discussed last time.

As the optics become more transparent to see the real world and as you want to be able to work in brighter light, the virtual image has to be brighter to stand out. HL2’s 500 nits reasonably good for indoor use where a computer monitor is typically about 200 nits and a smartphone on max brightness is typically 500 to 600 nits, but it still about an order of magnitude too low for outdoor use where concrete sunny day can be 7,000 to 10,000 nits.

How Can 52 Degrees Be More Than Double 34 Degrees?

52-degrees is more than 2X 34-degrees???

In a bit of marketing puffery, Alex Kipman said with a big picture so it was no slip of the tong:

“Today, I’m incredibly proud to announce with Hololens 2 we more than double our field of view while maintaining 47 pixels per degree of sight for Hololens”

Alex Kipman https://youtu.be/c1CZsqwnWtM?t=1719

The CNET article stated that the HL2 Field of View (FOV) was 52 degrees when the original Hololens was about 34 degrees. BTW, when only one number is quoted for the FOV, almost always it is the diagonal, because “bigger is better.” How is 52 more than double 34? Well, as Alex Kipman wrote on twitter that they were talking “Area,” good old marketing square law. It was at best misleading, as it is not the way people commonly talk about FOV (and Alex at least certainly must know it). This was an “unforced error” as they weren’t hiding the actual number elsewhere.

Laser Beam Scanning – Resolution Numbers Not “Adding Up”

This blog has 7.5 year history of explaining laser beam scanning and its pros and (mostly) cons. I have measured the claimed resolution through several generations and the always comes out to be about 1/2 the resolution in each direction that is claimed. I have every reason to believe that the HL2’s LBS will be no different in claiming a higher resolution than it can deliver. In fact, the number fail right off the bat.

The Resolution Math Fails!: 54,000 Cycles Divided by 60 = 900 cycles

Microsoft said in the video (and reported elsewhere) that the fast (horizontal scanning) mirror goes at 54,000 cycles per second. I started working in graphics in 1977 (I designed the Sprite Logic on the TMS9918, the first chip to have “Sprites”) and the first thing I do when I see a “big” number is to divide by 60. For any display without persistence, 60 frames per second is the bare minimum to have flicker free video, and for LBS with no persistence, it should be much higher. Doing this simple math, I get only 900 cycles per 1/60th of a second. Note also that a significant percentage of the lines will have to be blanked out while the vertical scan retraces (old CRT knowledge comes in handy here). Only about 720 cycles are in the “active” display (with the laser on).

But Microsoft said they have a 52-degree FOV and 47 pixels per degree and Alex Kipman said the aspect ratio is “more square” than HL1’s 16:9 (HDTV aspect ratio). Likely the aspect ratio is close to 4:3 like Magic Leap and this works out to the Horizontal FOV being 41.6 degrees and the vertical being 31.2 degrees. Multiplying 31.2 by 47 gives 1466 or extremely close 1440 which is twice 720 (within rounding error on the 47 pixels per degree).

Interlaced Video “Trick”

So how do you get 1440 lines out of 720 scans? You have to count both direction of a “cycle” of a scan scan line. This is what Microvision did with their old single mirror design and it must be what Hololens 2 is doing. But then there is the problem that you will end up with alternating pairs of pixels and then and gap of 2 pixels on the sides. So then Microvision old deign and I believe Hololens 2 uses the old CRT trick of Interlaced display.

On the figure below, I have colorized and annotated a 2011 Microvision patent that explained LBS with interlaced scanning. It shows a very simplified image with only a few scan lines. On field is shown in blue and the other field is show in red. I have also drawn a green grid of square pixel locations to show how the scan lines go through pixels and number the columns C0 to C5 and rows of pixels (R0 through R7). A percentage of the scans are blanked out (shown in gray). Below the figure in dark yellow I have show brightness of the beam has to vary to give uniform brightness (it varies dramatically from the sides to the center).

Because they turn the laser on in both direction of the scan, unlike an old CRT that only turns on in one direction, the result is a zig-zag scan. Following just the blue field, you should see that in Column 5 (C5) crosses through the very top of R0 and the very bottom of R1, but then it crosses the very top of R2. So the “pixels” in C5 are in pairs. The red field has the same effect but shifted down one row. So they are counting on the interlaced fields compensating for each other. From experience with prior Microvision projectors, the effect is that left and right side tend to be blurrier than the middle, but even the middle is not sharp (see for example my study of the Microvision based Celluon projector).

I created the GIF below (click on it to open the gif animation in a new tab) that isolates the two fields from the Microvision based Celluon projector. I shot two photos with a high shutter speed to capture the two fields. The animation shows the center and right side and you should note how the right side moves much more than the center. The colors also jump around in this animation due to the misalignment of the red, green, and blue lasers. It will be interesting to see if the Hololens as this issue as well. “Digitally” aligning the colors is another potential source of resolution loss with LBS.

Demonstration of Interlace, click in image to start GIF animation in new tab

Hololens 2 Should Have Significant 60Hz flicker – Long Term Use Human Factors Problem

Update Feb 28, 2019: After posting the original article, I receive an email from someone that got to try the HL2 and they reported noticing flicker on the sides of the image.

The older Microvision single mirror design used 60Hz “Interlaced” which means that parts of the field were only refreshed at 30Hz. I know of people that could not be in the same room with the old Microvision projectors as they were very sensitive to flicker. The Hololens 2 is likely using 120Hz interlaced which means parts of the image, particularly on left and right sides are only refreshed at 60Hz. If you look at the figure above, I have drawn two circles and area near the center that is refreshed at 120Hz and another area on the side that is only refreshed at 60Hz. The older people in the audience may remember the push in the late 1980s and 1990s to increase CRT refresh rates from 60Hz non-interlaced to over 75Hz due to flicker (once again old CRT knowledge). An this was with monitors that had phosphors with some persistence, unlike LBS that has none.

Horizontal Resolution

Horizontal resolution affected by the speed of switching of the laser beam and where the beam it located relative to the desired pixel including any distortion in the scanning process. As discussed above, the horizontal time of one pixel goes from relatively long on the left and right side of the scan to the shortest time in the center. The beam drive has to go from potentially off to an analog gray scale value with a surge in current that must be supported by the laser and it’s drive electronics. So far, I have yet to see an LBS projector came close to single pixel modulation in the center of the screen.

Regardless of the ability to control the laser and its intensity, the dual direction interlaced scan as well as other issue with LBS such a beam alignment will decimate the sharpness horizontally as well as vertically.

Expect the Effective Resolution To Be Less Than Half

Fundamentally the scan is not fast enough by about 2X to support 1440 lines or about 31 degrees at 47 pixels per degree. The interlaced and bidirectional scanning trick in my experience (see picture on the left) does not solve the resolution issue and in some ways makes it worse.

On top of the scanning rate issue, then we have the “usual suspects” with any laser scanning system. The two most common are laser speckle and beam alignment.

Laser speckle caused by the coherence of laser light. If you shot a laser directly into the eye, the person won’t see speckle, but that is not what the HL2 is doing. The HL2 likely have a pupil expander (essentially a rear projection screen) and then diffraction surfaces inside the waveguide which are all places where speckle should occur. This will give the picture a grainy appearance such as seen with front projecting laser scanning.

Another issue is the beam alignment of the various colored lasers.Even the most microscopic misalignment in 4 degrees of freedom (horizontal, vertical, pitch, and yaw) causes them to diverge by many “pixels” in the image. In the past Microvision (and others) have used “digital alignment,” either crude or fine. With crude alignment they just pick the closest line, but then you have to factor in the dual direction interlaced scan and the lines being at different angles, and since there are 4 degrees of freedom there it will not be the same everywhere on the screen. With “fine” correction, one color is picked, green is best, and then the red and blue images are re-sampled to match the green. But the re-sampling process means that the red and blue images are effectively blurred.

The bottom line based on my past studies of Microvision’s interlace LBS is that the effective resolution will be less than half of what is claimed.

Why No Microsoft Love for Microvision?

On April 26, 2018, Microvision announced they have shipped samples of a so-called 1440P ( 2560 x 1440) LBS engine. I say “so called” because both Microvision’s WVGA and 720p had less than half the measurable resolution that they claimed. This engine is a perfect fit for what it looks like the HL2 is using. Beyond just the numbers, Reddit User “lichtwellen” posted a comparison between a frame of the HL2 video and a Microvision patent.

In May 2019, Microvision, “Announces New License Agreement with a Leading Technology Company” and stated that they have, “entered into a license agreement with a leading global technology company to allow the licensee to use MicroVision’s display technology to manufacture and sell display-only engines based on MicroVision reference designs. The agreement grants a world wide, exclusive, five-year license to display-only technology. In order to maintain exclusivity, the licensee is required to purchase minimum quantities of MEMS and ASICs from MicroVision.” It is not a 100% certainty that this is referring to Microsoft, but everything so far points to it.

The announcement also claims that “the new scanner operates at 120Hz.” But based on Microvisions track record of fudging on specifications and my past studies of their products, I believe they are doing 120Hz interlace which is a full field rate of only 60Hz.

Maybe it is still coming, but I was expecting some kind of joint announcement with Microvision. All signs are now pointing to Microsoft at least licensing technology from Microvision. I’m left wondering why there was no announcement and who didn’t want it yet?

And Why didn’t Microsoft Just Buy Microvision?

In December 2018, Microvision was trading for less than 60 cents a share and the market cap was less than $60M. If Microsoft was serious about LBS, why didn’t they just buy Microvision? Even at a multiple to the stock price, it would be chump change compared to other acquisitions in this space and Microsoft’s spending on Hololens thus far. Maybe they got too good a deal on the “exclusive license discussed above or maybe this is just a stop gap.

What Happens to the “Extra” Horizontal “Pixels?”- IPD

So if the display supposedly supports 2560 pixels and 47 pixels per degree, then why doesn’t HL2 support 2560/47=54 degrees horizontally and more like a 60-degree FOV? And why did Alex Kipman say the display is “more square” as in closer to 4:3 aspect ratio?

Update 2/28/2019: One thing I missed while getting this together is that Microsoft has said that the HL2 aspect ratio is going to 3:2. This will have a slight effect on the numbers below. Mainly it would seem that they would cover a smaller range of IPD adjustment or they also have some vertical adjustment/reserved pixels.

The answer is that they are using the “extra” horizontal pixels to support interpupillary distance (IPD) adjustment. Microsoft has said that they are going to electronically adjust the IPD. This means they have to have guard-band pixels so they can move the image to adjust for IPD. Nominal IPD is about 63mm. From the pictures, and assuming the waveguide are centered, it roughly works out that the exit grading of the waveguides being about 27mm wide (see picture above right).

Now we have to get into the variability in human IPD see for example here in table 2. To cover the 1% percentile of adult women to 99% percentile men requires a range of 50 to 75mm. Dividing by 2 for the two eyes and they need about 12.5m mm of adjustment. If they back off a bit to 95% of women and men, which is the range from 57mm to 71mm, or a 14mm range needing 7mm of adjustment per eye. BTW, the reason why ML has two sizes is due to IPD and not head size).

So if the exit area is 27mm wide and they support 95% of all adult IPDs, they are going to lose/guard-band at least 25% of the horizontal FOV. If you take 25% off of 2560 you get 1920 pixels wide which gives a 4:3 aspect ratio with 1440 lines.

I have found in ALL cases when a company only quotes a single number for the FOV without specifying horizontal or vertical, the FOV they quote is the diagonal. “Bigger is better” and the diagonal is the bigger than horizontal or vertical.

Then we have the fib that laser scanning scan lines equate to pixel rows (they don’t). Next is the fib they are doing 120Hz. Assuming Microsoft’s claim of 54KHz is true and they are using the Microvision so called (but not really) 1440P device, they are only doing 120Hz INTERLACED which is really 60Hz full field refresh.

Butterfly Waveguide Confirmation

A picture from The Verge article confirms that HL2 has a “butterfly waveguide” as I said was possible last time. If you look carefully at the picture below right (and as pointed to by the four arrows) you can see the faint diagonal outline of the right and left (as seen by the user) intermediate DOEs.

I will be curious to see whether there is some visible seam or gap between the left and right side of the image that the user will notice.

Another interesting point is that Magic Leap supports roughly the same FOV but without requiring the butterfly technique. It should be noted that Hololens supports a much wider range of IPD adjustments with a single headset, which is supporting a significantly wider FOV just some of it is reserved for IPD adjustment. Additionally, the HL2 much more eye relief (distance from the eye to the optics) which makes it harder to support a wider FOV.

  1. There is a huge improvement in ergonomics and they are squarely aiming at the industrial market. The HL2 puts ease of wearing at a premium over style. By contrast, the Magic Leap One went for style over substance and achieved neither. I expect that the HL2’s flip-up display concept is going to become common.
  2. The resolution numbers simply don’t “add up.” I’m rather surprised, and even a little disappointed, that no one else calls them out on the 54,000 cycles per second mirror after dividing by 60 for a nominal refresh rate. I also think they may have problems turning the laser on and off fast enough near the horizontal center of the display. Assuming there is an HL3, there is a good chance that Microsoft will be looking for a different display technology.
  3. I’m a bit baffled that they have did not name Microvision as part of the HLS announcement.

Word of warning on Typos

Lately, Ron Padzensky has been helping me out by reviewing some of the article before they go out. I’m doing a lot of traveling lately and wanted to get this article out ASAP and could not wait to send it by Ron. So there will likely be more than the usual number of typos, but I thought it better to get this out than wait.

Default image
Karl Guttag

46 Comments

  1. Thanks Karl for the spot-on analysis!
    I think you described Microsoft’s misleading FOV claims very generously. In his presentation Kipman showed an animation of the old Hololens vs the new one that left no doubt that they claim a twice as large diagonal FOV. Due to those pictures the “viewing area” would be quadrupled.
    BTW, I found though that Microsoft’s marketing team has a tendency for good humor. The new Hololens 2 logo has a color shading that exactly resembles the color artifacts of their displays…

  2. man if only they could use the extra area for ipd for the fov

    • Yeah it seems surprising that if they are reserving some of the pixels for FOV this wouldn’t be dynamic with the eye-tracking (ie: set the IPD and then light all available pixels for FOV with correct software-distortion).

  3. man if only they could use the extra area for ipd for the fov

  4. Karl, another great summary. On your observation of the butterfly configuration, the likeliest reason for using this (when Magic Leap don’t) is to account for the fact that without it, you won’t have sufficient spectral coverage from the laser sources to fulfill the diffraction angle relationship. On another note – are you deducing 70% transmission based upon pixel values around the eyes in the pictures of people wearing the device? If so, how are you able to decouple the effects of them being shaded by it?

    • I used a different image for my analysis. It is very approximate but usually good to within 5%.

      Interesting comment about maybe the use of lasers driving the need for the butterfly waveguide. You should note that they have patents that show using the butterfly with LCOS (I don’t remember if it was laser illuminated.

      Overall, I get the feeling that Hololens is an R&D experiment that left the lab before it was done. The made some good practical decisions on improving the ergonomics, but the decision to use laser scanning was a bad idea IMO.

      • What display would you have ideally chosen ? just delay until MicroLED is available?

      • There really is no ideal choice. Using a diffractive waveguide, they are stuck with LCOS or DLP today. If you go with something like LUMUS’s LOE, they could use OLEDs but they might not be very bright (OLED are totally impractical as far as I am aware with diffractive waveguides).

        If there was an obvious choice, they would have used it. Part of Hololens’ problem is they start with the premise of a diffractive waveguide.

  5. Very nice analysis, Karl, thanks for sharing your thoughts.

    I’m a little bit confused about their FOV specs, I don’t know where does 52 degree come from, but MS does claim their display aspect ratio is 3:2, with 47 PPD. Taking those numbers together, it gives you a H 43.3 x V 28.8 degree FOV, with a weird 2034 x 1356 resolution (probably like you said, they only use the effective scanning area). So it covers almost the same image area comparing with ML1, but with a wider and shorter image (meanwhile they emphasis the importance of vertical field).

    However, if we assume a more common 1440 vertical resolution, still using 3:2 aspect ratio, 47 PPD. It turns out H 46 x V 30.6 degree FOV, with 2160 x 1440 resolution, right now you get a 55 degree DFOV, and the image area is much larger than ML1’s.

    Which one you think is closer to the truth?

    As for the LBS resolution, I read a patent of MS from 2017?, they propose to use two laser diodes mounting right next to each other vertically, by that way, it simultaneously scan two vertical lines, then you double the vertical resolution. I don’t know the image performance of this method, but theoretically it enables a 1440p image @60 fps with a 54000 Hz slow-axis MEMS (54000*80%/60*2= 1440), if they use interlace, then it becomes 120 fps.

    Still, like you said, those are just numbers on paper, doesn’t mean the effective resolution. What’s your thought on this?

    • I had my head down trying to get the article out and missed that they said it was 3:2. I noticed this the 3:2 aspect ratio after I posted the article but then the website crashed for 20 hour (what I nightmare).

      My latest guess is that they are reserving some pixels in both directions for IPD and vertical centering. Assuming they are not out and out lying, then I would assume a 52-degree FOV with a 47 (probably a rounded number) pixels per degree. As I wrote in the article, the 47 pixels per degree is “theoretical” and I expect the effective resolution to half that both horizontally and vertically.

      I just did some quick playing with the numbers and it looks to me like they might be going with a nominal 1920 by 1280 display region with ~43.3 by ~28.8 degrees.

      I don’t think that they are actually using what that patent shows. It is difficult and expensive to get two lasers aligned like that. I think they are trying to get around their current problems by thinking of things like that patent. It is easier to think of than to make. And by the why, someone has already emailed me saying they saw flicker in the HL2 demo. Could they someday, maybe, but I would bet on MicroLEDs over it.

  6. Why Microsoft don’t use the LetinAR lenses for Hololens 2?

    • LetinAR is an interesting technology but it is not ready for “prime time.” They are still working on perfecting it.

      • Thanks Karl!!!! I always read your excellent articles. I learned a lot about opticals in AR thanks to you!!!!

        I have a friend that went to the Microsift conference and he test the Hololens 2 and he told me that the FOV is about the same of HL1. What a shame. I expected about 70 FOV. I think I’m going to wait for Hololens 3 or other technology from other company. I’m very interested in nReal glasses.

      • First, it has been confirmed by multiple sources that HL2 has 52 degrees. UploadVR did a nice diagram comparing them https://cdn.uploadvr.com/wp-content/uploads/2019/02/ARFoV-Real2.png. The HL2 is 43°×29° whereas the HL1 is 30°×17.5° of the original. It is then just about identical to the Magic Leap One at 40°×30°. So the HL2 is about 3-degrees wider and 1 degree vertically less than Magic Leap.

        It is very “one-dimensional thinking” to just look at FOV. The HL2 has much better eye relief and is much more open which is hard to do. I find the ML1’s cables to be a pain and think HL2 looks much more user-friendly. On the downside as a reported, I am expecting serious problems with the HL2’s use of laser scanning. In addition to the fuzzy math claiming 47 pixels per degree, I have already received a report of someone noticing flicker at the sides of the image.

        Realistically, something has to give. To get a wider FOV you either need very large optics or you have to move the optics near to the eye. Things start getting exponentially difficult for an AR display as you get much past a 50 degree diagonal. Everyone keeps bumping into this problem.

        nReal will blow away either Magic Leap One or Hololens 2 on the image quality of the virtual image. Compared to HL2 it will darken the real world more. I don’t think the SLAM and Gesture Tracking is as sophisticated as on HL2 or ML1. As I said, AR is an n-dimensional problem.

      • No one else who saw HL2 & HL1 said that HL1 FOV = HL2 FOV.

  7. They haven’t mentioned Microvision because there’s nothing to say. Probably MSFT hired the key people from MVIS, who then did the mems and projector design, and then fabbed it out to a CM (likely Bosch.)

  8. I wonder if the ODG patents had anything to do with Microsoft not buying microvision.

    • I doubt it. ODG was mostly working on “traditional optics” and user interfaces. Microvision/LBS is pretty different.

    • When will you pumpers ever realize – nobody has ever bought Microvision because they have nothing that anyone wants.

  9. Karl, another awesome article as usual! I grew up watching interlaced TV being dramatically enhanced, and being replaced, by today’s progressive scan HDTVs. How near, or how far away, are we to microLED displays @ 1920 x 1280 – or higher resolution?

    What type of diagonal FOV will a next gen Hololens be capable of, or some competitor, based on your background, experience, tradeshow scouting, research, etc.

    Microsoft seems to have elagantly decoupled the display engines on the front of HoloLens 2 from the ARM based QC 850 cpu/gpu/alu/networking/battery, etc. While Alex Kipman said this was done for ergonomic reasons and weight distribution reasons, doesn’t this also allow for a more rapid shift to a newer microLED display engine when available?

    • Thanks,
      They are really pushing just to get the field of view Hololens 2 got with a waveguide, particularly with the amount of eye relief. There are two things that limit the FOV which is an angle.

      One of the factors is the angle that the light will stay in the waveguide. If you go past this angle, the light will not TIR like they want for the waveguide and will exit prematurely. This is what drove Hololens to the “Butterfly.” Additionally I’m still expecting to see image problems with the butterfly waveguide if they put up a large flatly shaded image, I expect to see some problem in the region where the two halve joint.

      The other factor is the simple triangle form the eye to the waveguide. As the eye-relieve gets as long a the HL1 or HL2, this triangle gets bigger meaning the waveguide has to get bigger. Worse yet, with a flat waveguide at some point with eye relief the waveguide has to get infinitely bigger and the cross unless the waveguide is curved (as the FOV approaches 180 degrees, the flat waveguide size approaches infinity).

      Lots of companies have split the optics from the compute and I’m not sure that this would be a big factor going forward. Getting MicroLEDs will help with a number of factors but will not help much with the FOV issues above. With HL2, we are still talking a very industrial design and not the kind of thing most consumers would wear, so I guess it depends on the market.

      • Thank you Karl for the reply … so, what is the current state of microLED displays? Are 1920 x 1280 displays currently in production? What is nReal using?

      • Full-color MicroLED appears to be a few years (or more) away for microdisplays. Lumens LED demonstrated single color red, green, an blue that are 1080p at CES 2019. Some companies are pursuing blue with quantum dot conversion to Red and Gree while others are doing nano-wire direct colors such as GLO which demo’ed at Photonics West a lower resolution full color microdisplay. There are pros and cons to each approach.

        nReal is using a Sony 1080p Micro-Oled.

  10. Karl,

    I think your estimate of 25k units may prove to be a little low. Japanese press indicating Hololens will launch in 10 countries.

    https://vrscout.com/news/hands-on-with-hololens-2/

    I thought this article was very telling. “after delivering 200 demos on the first day at MWC (conference attendees were waiting over 3 hrs in line for a chance to try the device) not one person mentioned feeling limited by the FOV”

    Of course you could say this person is biased as they are a MSFT partner. Also, thus far the only one to mention anything about flicker is your friend.

    As far as your notion that LBS is a stop gap, I don’t get that feeling from this interview with Kipman.

    https://www.youtube.com/watch?v=grOLd6NY-QU ” invented new display engine, a miracle.” I’m sure they did this just as a stop gap.

    Hololens is here to stay, it will be massively succesful and it would not be possible with out LBS and the advances made in the last two years.

    • The FOV of the Magic Leap One was similar using LCOS. Hololens 2 increase FOV over HL1 as more to do with the butterfly waveguide.

      We will see how it holds up when it gets past doing demos. There are going to be problems with using LBS and I already have first-hand reports of there being flicker. The faster mirror is not moving fast enough to support 47 pixels per degree as I wrote.

      Kipman has a way of putting a heavy marketing spin on things, like the “fib” about the FOV (he should know that they were misleading people with the greater than 2X and has been called to task). I think the same thing will happen with the resolution once it is objectively measured.

      Hololens 2 is still a bit of a lab experiment at $3,500.

  11. […] emploie des MEMS (microelectromechanical systems) dont le mécanisme est expliqué en détail dans l’article de Karl Guttag. Les critiques sont globalement bonnes sur le rendu avec un bémol toutefois venant de Techradar […]

  12. Karl,

    People love the product right off the bat. The reviews are fantastic. People responsible for making the purchasing decisions at large multi national corporations do not care about 47 pixels or your resolution math. What do they care about? Does it feel good, do the images look good, is the FOV bigger, does it increase productivity.

    At $3500, Hololens is absolutely not a lab experiment! Take an employee making 75k, a mere 10% increase in efficiency pays for the unit 2x in the first year. That is just one employee. Perhaps this plant runs two shifts and 2 employees can use the same unit?!?!?!

    I will say, that if there is flicker that caused discomfort, that would be an issue. So far you are the only one reporting such an event. I also have to believe that MSFT did hundreds of hours of testing. After all they spent hundreds of hours alone on just head measurements. If this was an issue they would not have released V2. However, companies are not immune from doing dumb things so I cannot completely dismiss your concern.

    Karl, you are a genius and half of what you say goes so far over my head I could not reach it with a 10 foot ladder. In this case I think you are being too smart for your own good. This is not a stop gap, this is not a lab experiment, and this is not another LBS failed attempt. This is MSFT designing LBS and in turn MVIS directly into the product. This is very different than Sony and past failures.

    The largest software maker in the world has chosen to make AR one their most important initiatives over the next decade. Hololens in considered the third phase of computing to them. In order to achieve what they desired, they could have chosen any technology. They chose LBS and MVIS and with out them Hololens does not work.

    Lastly, to answer one of your previous questions, Why doesn’t MSFT just buy out MVIS for pennies. First, the shareholders of MVIS would not allow that to happen. More importantly, that would be like asking in the mid 80’s why doesn’t MSFT buy out Intel? MSFT wants HPQ, Dell, Lenovo, and everybody else to make a version of this headset. They want to sell software!! A more likely candidate to buy MVIS is a Qualcom, ST Micro or even Intel. But not MSFT unless they plan on staying in the hardware business for the third phase of personal computing.

    Very exciting and interesting times!

      • Thanks,
        I’m not sure that the problem they are talking about. When you use lasers, you are dealing with color points outside the expected standard color ranges. You can get around this by blending colors (for example, a solid red must have some green and blue mixed into it). A classic problem is that if you don’t desaturate the colors is that things like grass almost glows green.

        There likely will be some color control problems due to the variable speed of the scan.

  13. […] HoloLens 2 first impressions: good ergonomics, but the LBS resolution math fails! […]

  14. It is fair to write the article from the base-line of the suggested quality Microsoft gives in the announcement, but it seems that results in an overly negative analysis. If you take the ‘real’ specs as you describe and just forget the announcement, the Hololens still fares very well compared to other solutions.
    As always, a great analysis though, thanks!

    • The 54kHz of the fast scanning mirror is a “real spec” and I tried to translate that into what it means in terms of image resolution and quality.

      The fact that the “fibbed” on the increase in the FOV and the 54kHz makes me seriously question whether their 47 pixels per degree is also a “fib.” They have established that they will play fast and loose with specifications (not to mention the word “Hologram”). I will be looking forward to trying to get in an objectively measure their resolution and other image quality aspects when possible.

  15. I saw strong reflective images on the shield in many HL2 pictures.
    Why do MS coat a AR coating on the shield?

  16. […] article follows up on information in my February 2019 article on the HL2. In researching this article, I came across an April 28th, 2019 video by Kipman called, “What […]

  17. […] As I have reported, my expectation based on other laser projectors I have seen and the scanning rate specification of the Hololens 2 is that there are going to be problems with the image quality. I have had verbal reports that there is flicker and that there are resolution issues, but this is the first public writing I have seen discussing “colours fuzz and jitter.” Unfortunately, there are zero “through the lens” pictures I can find of Hololens 2. If you know of any, please let me know. […]

  18. […] I reported on February 27, 2019, in Hololens 2 First Impressions: Good Ergonomics, But The LBS Resolution Math Fails!, based on my calculations on the numbers given by Microsoft and my experience with laser beam […]

  19. […] refresh) is ergonomically poor and should be disqualifying IMO. Both based on my calculation (see my article on Hololens 2 Interlacing) and my observation, the refresh rate falls far below the ISO-9241-3 standard’s recommendation […]

  20. […] I wrote in Hololens 2 First Impressions: Good Ergonomics, But The LBS Resolution Math Fails!, “Hololens 2 makes the Magic Leap One Look Like a Poorly Designed Child’s Toy.” As […]

  21. […] для полноценной системы дополненной реальности [26]. Во-вторых, сама технология подразумевает прохождение […]

  22. […] для полноценной системы дополненной реальности [26]. Во-вторых, сама технология подразумевает прохождение […]

  23. […] 2019; namely, Hololens 2 is Likely Using Laser Beam Scanning Display: Bad Combined with Worse and Hololens 2 First Impressions: Good Ergonomics, But The LBS Resolution Math Fails!. Regarding the second of the two articles, there is a slight change in the “math” […]

  24. […] that he was talking about “area” when everyone else measures FOV linearly (see my Hololens 2 First Impressions: Good Ergonomics, But The LBS Resolution Math Fails!, RoadtoVR, and UploadVR among […]

  25. […] of the image itself being discussed in the Microsoft patents/applications. It appears that the HL2’s butterfly waveguide ends up roughly doubling the width of the image, as about half of the image propagated down each […]

  26. […] blog back in February 2019 in Hololens 2 First Impressions: Good Ergonomics, But The LBS Resolution Math Fails!, stated that the HL2 was going to have flicker. It turned out that the HL2 uses 4-Way interlacing, […]

  27. […] of the image itself being discussed in the Microsoft patents/applications. It appears that the HL2’s butterfly waveguide ends up roughly doubling the width of the image, as about half of the image propagated down […]

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