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Laser Beam Scanning Versus Laser-LCOS Resolution Comparison
I apologize for being away for so long. The pictures above and below were taken over a year ago and I meant to format and publish them back then but some other business and life events got in the way.
The purpose of this article is to compare the resolution of the Celluon PicoPro Laser Beam Scanning (LBS) projector and the UO Smart Beam Laser LCOS projector. This is not meant to be a full review of both products, although I will make a few comments here and there, but rather, it is to compare the resolution between the two products. Both projectors claim to have 720P resolution but only one of them actually has that “native/real” resolution.
This is in a way a continuation of the serious I have written about the PicoPro with optics developed by Sony and the beam scanning mirror and control by Microvision and in particular articles http://wp.me/p20SKR-gY and http://wp.me/p20SKR-hf. With this article I am now included some comparison pictures I took of the UO Smart Beam projector (https://www.amazon.com/UO-Smart-Beam-Laser-Projector-KDCUSA/dp/B014QZ4FLO).
As per my prior articles, the Celluon PicoPro has no where close to it stated 1920×720 (non-standard) nor even 1280×720 (720P) resolution. The UO projector while not perfect, does demonstrate 720P resolution reasonably well, but it does suffer from chroma aberrations (color separation) at the top of the image due to optical 100% offset (this is to be expected to some extent).
Let me be up front, I worked on the LCOS panel used in the UO projector when I was at Syndiant but I had nothing to do with the UO projector itself. Take that as bias if you want, but the pictures I think tell the story. I did not have any contact with either UO (nor Celluon for that matter) in preparing this article.
I also want to be clear that both the UO projector and the Celluon PicoPro tested are now over 1 year old and there may have been improvements since then. I saw serious problems with both products, in particular with the color balance, the Celluon is too red (“white” is pink) and the UO very red deficient (“whilte is significantly blue-green). The color is so far off on the Celluon that it would be a show stopper for me ever wanting to buy one as a consumer (hopefully UO has or will fix this). Frankly, I think both projectors have serious flaws (if you want to know more, ask and I will write a follow-up article).
The UO Smart Beam had the big advantage in that it has “100% offset” which means that when placed on table-top, it will project upward not hitting the table without any keystone. The PicoPro has zero offset and shoots straight out. If you put it flat on a table the lower half of the image will shoot into the tabletop. Celluon includes a cheap and rather silly monopod that you can used to have the projector “float” above the table surface and then you can tilt it up and get a keystone image. To take the picture, I had to mount the PicoPro on a much taller tripod and then shoot over the Projector so the image would not be keystoned
I understand that the next generation of the Celluon and a similar Sony MPCL1 projector (which has a “kickstand) have “digital keystone correction” which is not as good a solution as 100% offset as it reduces the resolution of the image; this is the “cheap/poor” way out and they really should have 100% offset like the UO projector (interestingly, earlier Microvision ShowWX projector with lower resolution had 100% offset) .
For the record – I like the Celluon PicoPro flatter form factor better; I’m not a fan of the UO cube as hurts the ability to put the projector in one’s pocket or a typical carrying bag.
Both the PicoPro with laser scanning and the Smart Beam with lasers illuminating an LCOS microdisplay have no focus knob and have a wide focus range (from about 50cm/1.5 feet to infinity), although they are both less sharp at the closer range. The PicoPro with LBS is a Class 3R laser product whereas the Smart Beam with laser “illumination” of LCOS is only Class 1. The measure dbrightness of the PicoPro was about 32 Lumens as rated when cold but dropped under 30 when heated up. The UO while rated at 60 lumens was about 48 lumens when cold and about 45 when warmed up or more significantly below its “spec.”
Now onto the main discussion of resolution. The picture at the top of this article shows the center crop from 720P test pattern generated by both projectors with the Smart Beam image on the left and the PicoPro on the right. There is also an inset of the Smart Beam’s 1 pixel wide text pattern near the PicoPro’s 1 pixel wide pattern for comparison This test pattern shows a series of 1 pixel, 2 pixel and 3 pixel wide horizontal and vertical lines.
What you should hopefully notice is that the UO clearly resolves even the 1 pixel wide lines and the black lines are black whereas the 1 pixel wide lines are at best blurry and the 2 and even 3 pixel wide lines doe get to a very good black level (as in the contrast is very poor). And the center is the very best case for the Celluon LBS whereas for the UO with it 100% offset it is a medium case (the best case is lower center).
The worst case for both projectors is one of the upper corners and below is a similar comparison of their upper right corner. As before, I have included and inset of the UO’s single pixel image.
What you should notice is that while there are still distinct 1 pixel wide lines in both directions in the UO projector, 1 pixel wide lines in the case of the Celluon LBS are a blurry mess. Clearly they can’t resolve 1 pixel wide lines at 720P.
Because of the 100% offset optics the best case for the UO projector is at the bottom of the image (this is true almost any 100% offset optics) and this case is not much different than the center case for Celluon projector (see below):
Below is a side by side picture I took (click on it for a full size image). The camera’s “white point” was an average between the two projectors (Celluon is too red/blue&green deficient and the UO is red deficient). The image below is NOT what I used in the cropped test patterns above as the 1 pixel features were too near the resolution limit of the Canon 70D camera (5472 by 3648 pixels) for the 1 pixel features. So I used individual shots from each projector to double “sample” by the camera of the projected images.
For the Celluon PicoPro image I used the picture below (originally taken in RAW but digital lens corrected, cropped, and later converted to JPG for posting – click on image for full size):
For the UO Smart Beam image, I use the following image (also taken in RAW, digital lens corrected, straighten slightly, cropped and later converted to JPG for posting):
As is my usual practice, I am including the test pattern (in lossless PNG format below for anyone who wants to verify and/or challenge my results:
I promise I will publish any pictures by anyone that can show better results with the PicoPro or any other LBS projector (Or UO projector for that matter) with the test pattern (or similar) above (I went to considerable effect to take the best possible PicoPro image that I could with a Canon 70D Camera).
Welcome back!
Thanks for the article!
Seems speckle is still a problem for both projectors or for all the laser based projectors.
Any idea what LCOS was used in UO Smart Beam Laser LCOS projector? What’s the resolution? I assume much higher resolution is needed in order to achieve 720p resolution.
Please post more! Thanks!
Thanks for your interest,
There definitely is some speckle with both projectors, but it is not horrible with either one. I would not judge either to be significant better than the other, maybe a slight edge to the UO projector. You are seeing in the pictures in effect highly magnified images so you can see individual pixels and the cameras does not see same speckle your eye sees. The worst case for speckle is in large areas of a single color (say a large flat green patch) and when your eyes move (because the speckle moves relative to the image). It can also be tough if you put the
The camera can’t reproduce exactly what your eye sees in terms of speckle because the optics and sensor of the camera plus the “processing” is very much different than the human eye. There are two sources of speckle due to coherent light interference, the so called “objective speckle”, that occurs at the projection screen (light going in and reflected off the screen) and the “subjective speckle”, of the light going into and bouncing off the retina. The geometry of the camera lens is different and you can play with the F-number to try and get close to what you see but I did not do this with this set of pictures aimed at show the resolution.
Using direct green lasers helps significantly and as my prior article on the Celluon points out, there are some feature in the Sony optics with “multipaths” that probably helps. I would be interested to see say the Sharp Robohon projector that has much simpler and smaller laser combiner optics.
I have not seen inside the OU projector (I borrowed the one I used to take pictures for a few hours) and was not able to tear it apart. The panel inside is made by Syndiant and has 1280 by 720 pixels (physical reflective mirror locations) and uses field sequential color.
Is this at the same size/distance to the object? In other words, each is projecting a (ex: 3′ diagonal image?). With the double green lasers, Sony made improvements on speckle which is worst for green, so some improvements should be seen there (that would be the same for the UO). Contrast on lasers should be ultra high, so not sure why it’s not the case here. Just want to make sure nothing is optimized one way or another. Lastly, when will Navdy be available”
The Celluon PicoPro shot was a bit bigger image which helped it in terms of sharpness. I took some pictures of the Celluon and the UO at the same size but on inspection of the images close up the Celluon looked worse that other ones I had taken earlier so I used the better Celluon images.
It is not just a case of the laser alignment. I have looked at blue only images and ones where I only look at the blue channel the the image is only slightly sharper. The biggest resolution loss is due to the bi-directional, interlaced, Lissajous scanning process — please see my article on this subject at: https://www.kguttag.com/2012/01/09/cynics-guild-to-ces-measuring-resolution/
As for contrast, I plan on following up on that. The mythical 80,000:1 contrast is for a totally off image in a totally dark room. If you look at the interior of the optical engine (see https://www.kguttag.com/2015/07/13/celluonsonymicrovision-optical-path/) you will see that there are a lot of surfaces and optical components that the lasers go through. These optical components are likely there to reduce speckle but in the process they also cause light from the beam to be scattered. So a lot of what you are seeing is light meant for others parts of the image being scattered inside the optics and the sent by the scanning mirror into what should be the dark areas. Additionally, the lasers are likely kept a sub-threshold level even in the “black” state so they can be switched on more quickly; while considered “sub-threshold” the lasers still emit a little light.
What was the distance from projector to screen? A LBS projector should give better resolution at longer range (although a “good” resolution may correspond to a range which produces an image which is too large and too dim).
The Image (as you can see in the phone) is 35″ tall which means about a 70″diagonal so it is already a pretty very large image for a 32 lumen projector. I chose a larger image to try and be favorable to the PicoPro. The PicoPro has about 1.3 throw ratio so it was 91 inches (~7.6 feet or over two meters) away.
While the laser alignment and some chroma aberrations from the lens in the Sony engine cause some resolution loss, the main issue is that the scanning process of the Microvision engine is no where near 1920 x 720 in resolution particularly on the outside 1/3 of the image on the left and right side where the resolution is at best half that in the center. I explained the Microvision LBS scanning process in https://www.kguttag.com/2012/01/09/cynics-guild-to-ces-measuring-resolution/
That’s pretty long. Obviously the beam diameter is too large for good resolution.
No, the larger image is the BEST case for the Celluon projector. Please look at the series of images I posted in https://www.kguttag.com/2015/06/06/celluon-lbs-analysis-part-2b-never-in-focus-technology-revisit/. This proves that the larger the image the sharper it gets, the opposite of what you are suggesting.
The reason for smaller projected images being blurrier is that they have beam shaping generates a wider “beam” that spreads at roughly the same rate as the image gets bigger with distance. I believe they are doing this to reduce/prevent you seeing the individual scan lines on a large image. When the image is small, the wide scan beams overlap but the beams grow in diameter slightly slower than the image with distance so the overlap is reduced.
How about the color gamut comparison for both of them
Neither device had their colors tuned correctly. In theory using lasers either one could have a color gamut that would exceed the existing video standards. In fact, you need to desaturate the colors to work with existing content.
I noted, for example, that they even you called for 100% red, there was always another color (blue or green, I forget now which) mixed in. If you don’t do this then things like green grass will take on a plastic/glowing effect. You don’t even have to use lasers to have this problem, it happens when you use LEDs.
For high end theaters like Dolby’s new Laser Cinema (using laser illuminated DLPs) phenomenal contrast and color saturation, they can use content that is designed to take advantage of the added color gamut.
Hi,
Thanks for the (as always) awesome article.
I wonder if you had the chance to check on the “Laser Beam Pro” by Cremotech (what seems to be the successor of the UO Smart Beam). It uses LCoS with Laser as well. The specs sound promising, but I am not sure if the stated brightness of 200 Lumens is reasonable (especially since they claim to use a class 1 Laser). The specs can be found on their website: http://cremotech.co.kr/en/product/laser_beam_pro.php
Would be great if you could share your experience with the device (if you have seen it) or give a short estimation if that can even be possible…
Thank you in advance.
I wish you (and everyone else) a Merry Christmas, Happy Holidays and a Happy New Year.
Best, Chris
Thanks,
Cremotech is the company that makes the UO Smart Beam. I saw the Laser Beam Pro at CES last year but it was still a prototype. I would be suspicious of the brightness spec. as projector companies tend to “exaggerate” to put it nicely. With a panel projector illuminated by lasers, they can be Class 1 to more than 100 lumens but maybe not at 200 lumens. I’m told by experts that a laser illuminated projector (say DLP or LCOS) of the same brightness is no more dangerous than an LED projector Once you spread the light from the laser over the panel you no longer have that concentrated beam of light that can be dangerous to the eye.
The big advantage of a laser illuminated panel projector is that it is focus free. I have not seen a Cremotech Laser Pro, but I know the UO Laser Cube projector was not color balanced well and was lacking in red (the “white” looked a bit cyan). Hopefully they will have improved on this in the last year.
Dear Karl,
I’m a new face in the optics and photonics industry, but am so excited by the future of high dimensional laser-based systems particularly for the application of 3D scanning. My background is in developing neural networks for computer vision systems, and I’m in the process of trying to pin down some specs for the Cremotech Laser Beam Pro, which I believe uses the SYL2271. I’ve been trying to contact Cremotech, but am wondering if you know anyone or any way I could figure out specifically the distance from the microdisplay to the lens (focal length) on this device, or if this maybe a known trick for inferring this? (Manufacturer specs are of course preferred, but maybe I’m missing something obvious.) In any case thanks for being a voice of reason for all in the industry.
Following up with information for future readers, with thanks to a Reddit comment by you pointing out the Sony SXRD101A microdisplay used in the Laser Beam Pro C200, and doing experiments with a robotics apparatus we have, leading to deriving a focal length of 11.211mm. The error of this estimate from the device we tested, measured by removing samples, is below 10 μm.
Just heard from KDCUSA that “effective” focal length is 11.27mm, so I wonder whether to use our experimentally derived metric or their theoretical spec, but in any case not bad.
I apologize for being so late to respond. The LCOS Microdisplay is going to be on the other side of a beam splitting prism which affects the distance by the index of refraction of the prism. Also, the lens is not focused at infinity but likely more like a few meters away. What you can work back from to get the effective focal length of the projection lens is the divergence of the image (throw ratio). Note that it likely uses a lens with a few elements and at least one of them is movable to focus. They likely build the unit, then set and glue the focus making it focus free with the laser illumination. If the focus is set at a meter or two away due to the very high f-number of laser illumination, the image will be well enough in focus from about 30 cm to infinity.
Very cool, and insightful on the manufacturing process. My team just recently filed a provisional patent in the US for a “differentiable photonic generator-localizer” (https://3co.ai/static/assets/DifferentiablePhotonicGeneratorLocalizer.pdf) and the design of the math / data processing architectures described therein began to definitely inspire the desire for manufacturing new laser projectors, built for the task of 3D scanning. So hopefully one day it can make sense for me to learn about and help organize a brand new type of laser projector! Here is a quote: “Basic principles can therefore arise from prior art for broader and potentially more efficient photo-analytic explorations: more accurate and faster analysis can follow from dynamically generating more photons with more power at more frequencies in more directions, potentially distributed across more polarizations. This invention represents a control solution that can build on these principles.”
Very interesting comments. I have a Blackview Max1 phone. It incorporates a MEMES laser projector. The black level of this unit is CRT quality, together with CRT motion, due to the scanning principles.
I took colorimetry measurements. The colour gamut came very close to REC709 standards. There is a colour adjustment which takes the full native colour gamut to that of rec709. However, white balance from 0ire to 100ire was fairly consistent. The red being quite a bit too much. The lower 10ire showing a bit too much green. Gamma read at around 1.6. The overall image is very good from this projector, giving deep black levels, natural colour tones, nice motion and overall image is very good. The negatives being that the laser beam convergence isn’t perfect, although squinting improves it? Resolution, as suggested by Karl does not appear to reach 720p. If the white balance and resolution could be sorted, this would be one serious technology. I would say that the MEMS technology is better than lcos, due to the fact of pure laser light being scanned. We can achieve better black levels and motion than lcos. But as it stands, LCOS has the better resolution and brightness factors.
Thanks for the great review.