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Celluon LBS Analysis Part 2B – “Never In-Focus Technology” Revisit
I received concerns that the chroma aberrations (color fringes) seen in the photos in Part 2B were caused by poor alignment of the lasers. I had aligned the lasers per Celluon’s instructions before running the test but I decided to repeat the alignment to see if there would be a difference.
After my first redo of the alignment I notice that the horizontal resolution got slightly better in places but the vertical resolution got worse. The problem I identified is that the alignment procedure does not make aligning the pairs of red and green lasers easy. The alignment routine turns all 5 lasers on a once which makes it very difficult to see pairs of lasers of the same color.
To improve on the procedure, I put a red color filter in front of the projector output to eliminate the blue and two green lasers and then aligned the two red laser to each other. Then using a green color filter, I aligned the two green lasers. I did this for both horizontally and vertically. On this first pass I didn’t worry about the other colors. On the next pass I moved the red pair by always the same amount horizontally and vertically and similarly for the green pair. I went around this loop a few times trying for the best possible alignment (see picture of alignment image above).
After the re-alignment I did notice some slightly better horizontal resolution in the vertical lines (but not that much and not everywhere) and some very slight improvement in the vertical resolution. There was still the large chroma aberrations, particularly on the left side of the image (much less so on the right side) that some had claimed were “proof” that the lasers were horribly aligned (which they were not before). The likely cause of the chroma aberrations is the output lens and/or angle error in the mechanical alignment of the lasers.
Below shows the comparison before and after on the 72-inch diagonal image.
Note the overall effect (and the key point of the earlier article_ of the projected image going further out of focus at smaller image sizes. Even at 72-inch diagonal the image is far from what should be considered sharp/in-focus even after the re-calibration.
Below shows the left and right side of the 72-in diagonal image. The green arrows show that there is minimal chroma aberration on the right side but there is a significant issue on the left side. Additionally, you may note the sets of parallel horizontal lines have lost all definition on the left and right side and the 1 pixel wide targets are not resolved (compare to the center target above). This loss of resolution on the sides of the image is inherent in Microvision’s scanning process.
While the re-alignment did make some parts of the image a little more defined, the nature of the laser scanning process could not fully resolved other areas. In future article I hope to get into this some more.
One other small correction from the earlier article, the images labeled “24-inch diagonal” are actually closer to 22-inches in diagonal.
Below are the high-resolution (20 megapixel) images for the 72-in, 22-in, and 12-in images after calibration. I used a slightly different test patter which is also below (click on the various images for the high-resolution version).
Just to verify that my camera/lens combination was in no way limiting the visible resolution of the projected image, I also took some pictures of about 1/3 of the image (to roughly triple the resolution) and with an 85mm F1.8 “prime” (non-zoom) lens shot at F6.3 so it would show extremely find detail (including the texture of the white wall the image was projected onto).
Below are the images showing the Center-Left, Center and Center-Right resolution targets of the test chart above. Among other things to notice how the resolution of the projected image drops from the center to the left and right and also how the chroma/color aberrations/fringes are most pronounce on the center-left image.
Karl
The last test images you produced do seem to be much clearer with better contrast. The use of your colored filters held outside the projector was a clever way to tune distinctly colored lasers. I’ll have to remember that trick, as it may be useful to observe color channel output for many projectors.
Is the Celluon a fanless projector? And do you expect most laser based projectors (e.g., DLP, LCOS,etc.) to be fanless in the future?
I’ve always been annoyed by the noise, extra power consumption, and open housing vents that exist with mechanical cooling fans inside small handheld projectors.
The laser alignment improved the clarity. I also made sure to shoot them at ISO100 which may have helped slightly. I found a handy product on Amazon (linked to below) that has a paddle of various handy color filters, polarizers, and diffraction gratings.
The Celluon project is fanless, but this is due to the heat sink/spreading design and the requirement to have the projector “suspended” in air rather than the project being efficient. The projector system requires over 6 watts at 32 lumens which is worse than DLP or LCOS. A totally black image takes about 2.6 watts. So in reality the Celluon projector is not very efficient.
If you put the celluon projector on a surface like a tabletop rather than suspending it in the supplied cradle, and put a bright image up it will quickly overheat. What is done is that while the projector takes up about 1/3rd of the case, there are heat spreaders along the entire top and bottom of the case so if you block the air flow over the top or bottom it will overheat. I have also found that if you put up a white image (max power) and charge the product at the same time it will overheat. So they are right on the edge of overheating with the design even in normal use. The rest of the electronics do not produce a lot of heat so they use the rest of the product’s area to spread out the heat. You can argue it is a cleaver package design, but it is not a particularly energy efficient. I’m planning on showing how the heat spreading works in a future article.
Most other products have much higher lumens so the heat spreading alone is not sufficient and they require fans, it is NOT due to efficiency relative the the Celluon. Also the “tricks” use to spread the head would not work if the projector was say embedded in a cell phone as they could not move the heat to the rest of the system.
http://www.amazon.com/Rainbow-Symphony-Paddles-Diffraction-Gratings/dp/B00K6K2LM4
Karl, you said,
If you put the celluon projector on a surface like a tabletop rather than suspending it in the supplied cradle, and put a bright image up it will quickly overheat.
That is absolutely not true. I have run my unit for three hours while watching movie and this has never happened.
Bob, try putting up a full white image like you would have say viewing a computer file and see how long it last. On typical movie, the average pixel is about 25% on so the power of the projector is down to about 3.5 to 4 watts from its peak of 6 Watts with a white image.
Why would I even want to do so? The intended use is for entertainment, video and picture sharing. I think you are creating use case scenarios that are extreme and will rarely, if ever, be used to show faults in the technology.
Bob,
I’m creating a real use case for using it attached to a computer through an HDMI port. Take a look at more computer content and it is mostly white/light with a small percentage of black text. The product should be designed to where it does not overheat if you put up white image. There are no warning labels saying “only use this for video because we have not designed it to handle content with an average of over 50% white pixels” or the like. Similarly if they claim that it has 1920×720 resolution, it should be able to do it.
Karl
I just displayed this page for an hour, no problems.
I have the same paddle of colored filters, with a one-axis and two-axis diffraction grating to boot! Love it. I’ve used it for lots of experiments with coherent and incoherent, visible and non-visible light. Purchased mine from my local Science Surplus and Supply store.
“Most other products have much higher lumens so the heat spreading alone is not sufficient and they require fans, it is NOT due to efficiency relative the the Celluon.”
Then please explain why the AAXA l1 laser-illuminated LCoS projector required an internal fan while producing 20 lumen. (12 fewer lumen than the Celluon product.)
Geoffrey,
Perhaps because you are comparing something that was made 5 to 6 years ago with different laser technology that was less efficient. Also they had to have motors as a part of speckle reduction because of the frequency doubled lasers.
As far as the Celluon goes, so you doubt my measured number of 2.61 Watts for a totally black screen and 6.1 Watts for a white screen? Less than 0.3 Watts escape as “light” so with a white screen there are about 5.8 Watts of heat generated at 32 lumens. That is an awful lot to put in a phone or other small device. An iPhone 6, for example, in “high power” data use consumes about 0.6 Watts and with GPS and everything running and charging the battery may get a bit over 1 Watt. So if you were adding this projector to an iPhone 6 you have to design for about 4X to 8X the power consumption to put out 32 lumens or about 3X the power consumption with the projector putting out a black image.
Karl
Karl,
Can you explain why we’ve not seen a direct green laser illuminated LCoS projector embedded in a prototype tablet or smartphone?
Also, can you explain why Lenovo uses a Laser Beam Scanning engine in the Smartcast smartphone prototype?
“Can you explain why we’ve not seen a direct green laser illuminated LCoS projector embedded in a prototype tablet or smartphone?”
You seem to be confusing R&D and marketing prototypes with real products. Companies are fooling around with all kinds of concepts all the time. They may seem some extra marketing advantage in having a laser projector. But the reality is that embedding a laser projector of any type is not practical. So what difference does it make?.
Today it comes down to it being to expensive and the lack of a market for a low lumen projector being embedded in a product. LCOS is being tried in dozens of prototype and real products for “near eye” AR/VR applications where it has a large competitive advantage over other technologies in most uses.
As far as Lenovo, it is just an R&D prototype and highly impractical for significant consumer use. If they were really serious, they would have kept it a secret until it is a real product.
If you compare “real” products, then it comes down to the Celluon (a company that very few have heard of) projector using LBS versus the SK Telecom (the largest cell phone company in Korea) UO Smart Beam projector using lasers and LCOS that apparently just started shipping.
Karl
Karl,
1. How does a Laser Beam Scanning projector produce the color black?
2. Did you test the resolution of your Celluon Laser Beam Scanning projector with a black and white test pattern created by yourself?
3. Have you tested the resolution of the Celluon projector with a color test pattern?
Geoffey,
1. Black is produced by turning the lasers off (or mostly off, some lasers have a “subthreshold” current applied).
2. I have looked at both black and white and single color test patterns. BTW, even with an only blue test pattern and thus eliminating laser alignment, the same lack of focus results occur.
3. Yes I have tested with color test patterns. The color control is pretty poor and affected by the how much the lasers are heated up by other image elements.
Also, did you know that when you call for “pure” green, it turns on red and blue to try and get the right green point (and similarly they turn on green and red with “pure blue”, and green and blue with pure red — there goes the so called “HK effect”).
Karl
I’m kind of late arriving here, but this is after much reading on both camps (this blog and MVIS-related blogs). Standing from a distance, I can see biases on both sides. It is not much different from reading a flame war between “iSheeps” and “Fandroids”, which can break out at any moment on any tech blog and adds no real value. It may be possible that many people are not even aware of their own biases that color everything they say and the way in which they say it. Here is a typical example: instead of writing just…
“If you put the celluon projector on a surface like a tabletop rather than suspending it in the supplied cradle, and put a bright image up it will quickly overheat.”
…it would be a service to the customer to complete the picture by adding some contextual info (in caps), like this:
“If you put the celluon projector on a surface like a tabletop rather than suspending it in the supplied cradle, and put up a bright image WHERE MOST OF THE BACKGROUND IS WHITE (E.G., POWERPOINT SLIDE), it will quickly overheat. HOWEVER, IF YOU WATCH A MOVIE OR YOUTUBE VIDEOS, THEN THE OVERHEATING PROBLEM GOES AWAY BECAUSE THE PROJECTED IMAGE WON’T BE DOMINATED BY WHITE ANYMORE. IF YOU WANT TO REDUCE THE HEAT FOOTPRINT, POSSIBLY PROLONGING THE LIFE OF THIS DEVICE, THEN AVOID PROJECTING IMAGES THAT HAVE A WHITE BACKGROUND FOR LONG PERIODS OF TIME.”
An analysis can be objective, but it can also be objective and biased if you only include the bits that scare away people and leave out stuff that may pertain to them and give them a bigger, better picture of where the product stands in respect to their needs or usage patterns.
If there’s one thing I know about people, it’s that they have no issues leaving a negative review on Amazon if they didn’t like the product. After reading all the analysis of the Celluon PicoPro in this blog, I could’ve sworn that it would have a one- or two-star review on Amazon. To my surprise, it currently averages 4.1 stars (granted, some reviews are from current or former MVIS shareholders). You can analyze a product all you want, but at the end of the day customers will judge with their own eyes using the product in their own homes viewing their own content, and then decide to keep it or return it within the refund period.
A projector should be designed to work with any content you put up. Putting up a largely white image is typical of many text applications and business presentations. This product is at best on the edge in terms of overheating. As I later found out when I tore it down, much of the heat dissipation is designed to come out the bottom. What if your car engine overheated because you drove at 70MPH for over an hour, would you say that’s OK, because it does not overheat when you drive in stop and go traffic?
You still have a pretty select group of people buying the Celluon who are willing to spend $350 for a low brightness, low resolution projector that is lousy at projecting documents including PowerPoint type content. We will have to see how it goes when it gets passed the gimmick buyers.
Objectively measured (that’s what I do) the Celluon product has a lot of faults. By any objective measure it does not have 1920×720 or even 1280×720 that it claims, the demonstratable resolution is closer to 640×360 our about 1/6th to 1/8th the pixels claimed. I have posted my results and the resolution charts that go with them and nobody has shown otherwise. It is also a flat false claim that “laser lumens are brighter than “led lumens. Certainly gullible customers may be persuaded by such claims.
I’m aware of all the limitations and incorrect specs, so not sure why you felt the need to rehash them in your last paragraph. Please allow me to repeat myself: regardless of whether the projected image is equivalent to 1920×720 or 640×360, the average customer will judge the performance of the projector with their own eyes (your vision and sensitivity to artifacts may be different than their’s) using the product in their own homes (every home layout is different and can determine wall distance range and placement angle) viewing their own content (not everyone, including myself, will be using this as a data projector) in the ambient light level that they are used to (movie theater dark for me), and from that experience make a decision whether to keep or return the projector within the return period.
Your deep analysis is very detailed–and dare I say, even admirable–but I’m afraid you’re mostly educating yourself and only reaffirming what you already feel, and that is that you are not a big fan of laser-based projection systems. The layperson will either not find your blog and buy the Celluon PicoPro based on the positive reviews in popular media (e.g., Editor’s Choice from PC Magazine), or find it too technical and end up buying the Celluon PicoPro anyway, and likely end up keeping it since I haven’t come across many cases of people returning this product other than when it’s defective.
It is OK for you not to like the Celluon PicoPro (it is not for everyone), but for you to expend so much time and effort on your blog, and in the comments section of other sites with links back to your blog, to try and educate everyone else why they should steer clear of this product doesn’t put you in the best of light (no pun intended), especially when you consider the fact that there is a 30- to 60-day period where people are allowed to evaluate the product and return it for a complete refund if they are not satisfied with their experience.
Thanks for your concern and you are probably at least partially correct. Going along (even with lies) will get one more friends but deep analysis is what I do. If you want “everyone gets a trophy” type reviews, you can find plenty of them.
PC Magazine certainly had the ability to run test similar to what I have done and verify the resolution. What service do they provide if not to test the products and show the results? David Stone article was a total cop-out with his comment “it offers suitable image quality for anything other than text-based material” and note that presenting text was not even listed as a con. The bottom line is that text of even moderate resolution and on non-black or white backgrounds looks terrible.
Additionally there is a serious flicker issues and the product is a Class 3 laser product.
I guess we should cut VW a break with their recent diesel problems. They had been making cars like that a long time and nobody complained.
Karl,
I can’t help but notice that you failed to answer the question about whether you had created the black and white test pattern yourself.
Also, why have you not posted the results of the tests that you’ve supposedly conducted with color test patterns?
Yes, I created the test pattern myself. The various “targets” are loosely based on the standard USAF test pattern (https://en.wikipedia.org/wiki/1951_USAF_resolution_test_chart). The long horizontal and vertical lines are there to show resolution changes across the display.
As far the color tests, I’m hoping to borrow a spectral meter to complete some of the tests and give some numbers. I can tell you that the Celluon “white point” is shifted very far into the red which is why when you take pictures of “white” with a camera it tends to come out looking a bit pink. One complication is that the colors are dependent on laser heating so that other content in the image affects the color. It make a significant difference if you put up a screen of a solid color, a small patch on a black background, or a small patch on a white background. Also the gray scale control is very poor and the color shifts with the brightness/gray-scale value.
Karl
Hi I would like to know the life of the laser diode projector sony mp- cl1 that according to its manual is 2000 hours seem few and the poyector Celluon picopro using the same laser diode manual says is 10,000 hours then approximate actual lifetime have these laser diodes
what happens when they finish their useful life
less light ? does not illuminate the projector ?
thank you
I don’t have a lot of information on the Laser lifetime. I know that LED lifetimes are generally spec’ed in terms of “half brightness” rather than stop working like a filament or arc bulb where is burns out/stops working.
I suspect that the lifetime differences between Sony and Celluon may be more one of specmanship (how they spec) rather than real differences, but it could be that Sony got a better “sorting” of the laser diodes. I would think that Celluon was getting the spec’s from Sony which built the enginer.
Hello Karl, do you have checked the Sony MP-CL1? The big difference compared with the Celluon PicoPro is that it accepts Full HD (1920×720 pixels) as input without any problems (Miracast and HDMI, set 1920×1080 in screen settings manually). So, I assume that horizontally there is no (up)scaling anymore, each pixel will be projected 1:1. Only vertically there must be a downscaling. (PicoPro: horizontally: upsacling, verically: no scaling). I am not a specialist like you, but for me text is much better readable and smaller fonts are possible. It has some other improvements, e. g. “white” is really “white”. Because of the completely other scaling algorithm you may come probably to different results than with the PicoPro. Brightness does not changed much, if even.
Chris,
I have not had my hands on the Sony MP-CL1, not that I would not like to compare it. First, there is some confusion on your part because you said Full HD is 1920×720, but maybe you are saying the Sony accepts 1920×1080 (I couldn’t tell from the way you wrote it).
Beyond all that fundamentally the scanning process of laser beam scanning in general and the Microvision Lissajous pattern interlace method specifically effectively cuts the resolution by about 2X. It is NOT about scaling of the input, although that could make matters worse. The fundamental problem is that they are scanning a different pattern than the pixel grid and there is thus inevitable scaling to fit the grid.
Furthermore due the the non-offset optical system requiring digital keystone correction, there is a further reduction of resolution in the Sony system.
It sound like they have improved the colors on the Sony projector (the Celluon projector appears to be a bit too red).
If you have a system, why don’t you give the test pattern below a try and see what results you get. I will be happy to post your results. It possible mount your camera on a tripod or the like to keep it steady as you need a long exposure (generally slower than 1/10 of a second) to avoid the roll-bars of the scanning process. Try and make the image about 23-inches tall or more. Also it would be interesting to see how small and image you can make and stay in focus.
Karl
https://www.kguttag.com/wp-content/uploads/2015/06/interlace-res-chart-720P-G100A1.png
Hi Karl,
Could you help me on the topic that laser projection systems have such a large focus range ? Why is that? Does it really eliminate any kind of focus adjustment lenses?
Regards,
Aditya
To give you a good answer, I need to understand whether you are asking about front projection (with a screen) or something like Augmented or Virtual Reality glasses.
With AR/VR glasses there are two approaches, one is direct retinal scanning and the other uses a “pupil expander” (effectively a small projection screen).
While direct retinal scanning is “focus-free” but has an extremely small “eye box” thus making it very hard to see the image unless the eye is in exactly the right place. Also, the field of view is typically small and examples include North Focals (one, not sure about 2), Bosch at CES 2020, and QD-Laser. With direct retinal scanning, the image if focus-free but you get floaters.
The Hololens 2 is an example of using a pupil expander with a pupil replicating diffractive waveguide. With this approach, they effectively are projecting onto a small screen and that becomes the point of focus. The image past that point is no focus free.
Then we have front-projection where the scanning is done onto a projection screen. With this approach, there is a lens that adjusts the size of the beam. If the beam is too narrow you tend to see the scan lines, if the beam is too wide they overlap and blur the image. They typically try and set the beam divergence to be close to the throw ratio (the rate that the image expands with distance) but it won’t be exact and typically there is some overlap at short projection distances and scan lines visible at longer projection distances. Since the laser beam is essentially scanning the scanned image itself will be relatively in-focus. The problem is that the scanning process is non-rectangular so that scan-lines are not the same as lines of pixels. The pixels in the original thus have to be digitally resampled/scaled to map them onto the scanning process. I discussed and showed this issue back in 2015 with the Celluon Laser Scanning Projector (see for example https://www.kguttag.com/2015/06/01/celluon-laser-beam-scanning-projector-part-1/ and https://www.kguttag.com/2015/06/02/celluon-laser-beam-steering-analysis-part-2-never-in-focus-technology/). With front projection laser scanning there is almost always some amount of laser speckle as well which degrades the image quality.
I should also note that laser-illumination of LCOS (or DLP) can also relatively focus-free. I demonstrated this back in 2012 (https://www.kguttag.com/2012/01/27/laser-with-lcos-is-focus-free/). It still tends to have some speckle unless the screen is vibrated.
If you can be more specific about what you are trying to do, I may be able to give you a better answer.
[…] Steering Analysis Part 2 – “Never In-Focus Technology,” Celluon LBS Analysis Part 2B – “Never In-Focus Technology” Revisit, and Celluon/Sony/Microvision Optical […]