The Celluon PicoPro projector has been out for a few months now for about $359. I have read a number of so-called “reviews” that were very superficial and did little more than turn on the projector and run a few pictures and maybe make a video. But I have not seen any serious technical analysis or review that really showed the resolution or measured anything beyond the lumens. So I am going to be doing a multi-part technical analysis on this blog (there is just too much to cover in one article).
In the photo at the top, I took a picture with the lasers on to more clearly see the various light paths. A surprise to many is that they used 5 lasers and not just three which adds to the cost and complexity of the design. They use two red and green lasers to get to the spec’ed (and measured) brightness of 32 lumens. In future articles, I will get into more details on the optical path and what is going on (there are a few “tricks” they are using).
It is no secret by now that the Celluon engine uses a beam scanning mirror from Microvision and the optical engine and electronics are from Sony (the engine looks identical to the one Sony Announced February 20, 2014) . Below I have taken the cover off the electrical part so you can see some of the chips. If you look carefully at the red arrows in the picture below, you can see the 3 clearly identified Sony ASICs used in the driver board (the 4th large chip is a Samsung SDRAM and the smaller device is a Texas Instruments power supply chip — there are more power supply chips on the backside of the board).
I have used test charts to measure the resolution, check the color control , and measured the power consumption. I have also taken a look inside to see how it is made (per the pictures above). I have collected data and many images so the biggest problem for me to boil this down into a manageable form for presentation on this blog. I decide to start with just a bit about the resolution and a summary of some other issues.
Celluon claims the resolution is “1920 x 720” pixels and not that is not a typo on my part, they really claim to have “1920” horizontal resolution with as claimed by Sony in a press release on the engine. It is easily provable that the horizontal resolution is much less than 1920 or even 1280 pixels and the vertical resolution is not up to fully resolving 720 lines. In fact the effective/measurable resolution of the Celluon engine is closer to 640 by 360 pixels than it is to 1280×720.
PC Magazine’s April 22, 2015 article on the Celluon PicoPro made the oxymoron statement “the image has a slight soft-focus effect.” To me “soft-focus” means blurry and indeed the image is in fact both blurry and lower in resolution. The article also stated “I also saw some reddish tinges in dark gray areas in some images, a problem that also showed up in a black-and-white movie clip“. The image is definitely “off to the red” (white point at about 4000K) and it has very poor color control in the darker areas of the gray-scale.
Resolution is a big topic and I have a lot of photos, but to get things started, below I have taken a center crop of 1280×720 HDMI input into the Cellulon projector. Below this image I have included the same crop of the text pattern in put zoomed in by 2X for comparison. In the photo you will see a yellow measuring tape that was flush against the projection screen, this both shows the size of the projected image AND proves that the camera was focused well and had enough resolution to show pixels in the projected image.
You might want to look at the various areas indicated by the red ovals corresponding to the same areas of the projected image and the test pattern. What you can see is that there is effectively no modulation/resolution of the sets of 1 pixel wide vertical lines so the horizontal resolution is below 1280 (more like about half 1280).
There is some modulation, but not as much as you should get if this were truly 720p, of the horizontal lines center of the of the image but this will fade out towards the left and right side of the projected image (I will get into this more in a future article).
You may also notices that the overall Celluon image is blurry. Yes, I know lasers are supposed to “always be in focus,” but the image is definitely out of focus. It turns out that at the size of this image (12 inches vertical or 24 inches diagonal which is moderately big, the width of the scanned laser beams are wider than a pixel and thus overlap.
The image is even more blurry if the image is say about 7-inches high projected on a standard letter size sheet of paper (the image is very blurry). The blurriness goes down if the image gets bigger but it is NEVER really sharp even with a 72-inch diagonal image. In a future article I will post the same test pattern at different image sizes to show the effects of image size and blurriness/focus. I have started to call this “never in-focus technology.”
Some summary observations (more to come on these subjects):
- Laser Speckle – much improved over previous Microvision ShowWX projectors. It still is far from perfect an most annoying where there are large flat areas and text on a bright background.
- The Celluon eliminated the “bowtie” effect of earlier Microvision ShowWX product so that the image is rectangular
- The lost the 100% offset of the ShowWX meaning that this requires a “stand” and the image will either be keystone or the projector will be between the viewers eye and the image. This is bad/wrong for a short throw projector. There is no keystone correction supported by the product.
- Low effective resolution – absolutely nowhere close to 720p (see above, more on this in future articles).
- Blurry image – not the same per se as resolution. The size of the laser beam appears to be bigger than a pixel until the image is very large. Additionally there are issues with aligning the 5 lasers into a single “beam” and issue with the interlaced bi-directional scan process (see https://www.kguttag.com/2012/01/09/cynics-guild-to-ces-measuring-resolution/ for more on the scan process and how it hurts resolution).
- Class 3R laser product – This is a very serious problem as it is not safe for use with children (in fact laser safety glasses are recommended) but it this is not well marked. The labels on the product are ridiculously tiny (particularly the one on the projector itself). The EU is reported in the process of banning consumer products that emit 3R laser light (http://www.laserpointersafety.com/news/news/other-news_files/tag-european-union.php and http://eur-lex.europa.eu/legal-content/EN/TXT/?uri=CELEX:32014D0059)
- Flicker – this is a serious problem with this product and I will discuss more about this in a later article. About 1 in 7 people I showed the projector to said it gave them headaches or other problems (I had multiple people tell me to turn it off as it was painful to even be in the room with it). The scan process is 60-hertz “interlaced” with no persistence (as with an old CRT).
- The power consumption is high taking about 2.6W to show a totally back image and 6.1W for a totally white 32 lumen image with the power consumption in between roughly proportional to the image content. Don’t let the lack of fans fool you, they are using heat spreading over the entire package to dissipate the heat from just the projector. The device will quickly overheat if left on a tabletop (as opposed to the fan) as much of the heat is spread over the bottom of the package. It will also overheat if a bright image is left on the screen for too long even if the device is floating in air.
- The color/gray scale control is pretty poor particularly with the darker parts of a gray ramp. At the dark end of the gray scale the “gray” turns red. Additionally there is “crosstalk” caused from the lasers heating or cooling based on the brightness on one part of the screen that affects the color/brightness on the other side of the screen. In other words the content of the image in one area will affect the color in another area (particularly horizontally).
I have seen Microvision laser scanned projectors since the Microvision ShowWX came out in 2010 or 5 years ago and the Celluon unit has many of the same issues that I found with the ShowWX. While the Celluon is much improved in terms of brightness and speckle, has better resolution (but not as near what is claimed) and it delivers about 3X the brightness for the about the same power (much of this is due to laser improvements over the last 5 years) the progress is very modest considering that 5 years have passed.
Frankly, I still consider this technology far from ready for “prime time” high volume and sill has some major and in many ways fatal flaws. Being laser safety class 3R at only 32 lumens is chief among them. The flicker I also consider to be a fatal problem for a consumer product but this perhaps could be solved by going to a higher refresh rate (which would require a much faster scanning mirror). The power consumption is far too high for embedding into small portable products.
And then we come back to the issues with the “use model” that still exists with Pico Projectors (see my discussion from way back in 2011 about this).
On a final note, I know that Laser Beam Scanning has a very dedicated following with some people that vigorously defend it. I will be providing test patterns and other information so people can duplicate my experiments and verify my results. I am more than happy to discuss the technology and respond to dissenting opinions, but I won’t tolerate rude comments or personal attack in the discussion.
Addendum — Test Patterns
Below are some test patterns stored in lossless PNG format to try out on the Celluon or other 720p projector to see for yourself.
Right-Click on the given pattern download the original full size pattern. Note, they should be view at “100%” if not on a 720p monitor and should totally fill the screen on 720p projector.
The first one below is a resolution test with 9 “zone patterns” has well as sets of 1 pixel wide black and white horizontal and vertical lines.
Below may look dark gray or even black but it a totally flat R=B=G=16 everyone (a flay gray of 16/255). See how it looks on the Celluon.