Archive for Pico Projection

Lenovo’s STMicro Based Prototype Laser Projector (part 1)

Lenovo Tech World Projector 001At Lenovo at their Tech World on May 27th 2015 showed a Laser Beam Scanning (LBS) projector integrated into a cell phone prototype (to be clear, a prototype and not a product).   White there has been no announcement of the maker of the LBS projector, there is no doubt that is made by STM as I will show below (to give credit where it is due, this was first shown on a blog by Paul Anderson focused on Microvision )

ST-720p- to Lenove comparison 2The comparison at left is base on video by Lenovo that included an exploded views of the projector and pictures of STM’s 720p projector from an article from Picoprojector-info.com on Jan 18, 2013.   I have drawn lines comparing various elements such as the size and placement of connectors and other components, the size and placement of the 3 major I.C.’s, and even the silk screen “STM” in the same place on both the Lenovo video and the STM article’s photo (circled in yellow).

While there are some minor differences, there are so many direct matches that there can be no doubt that Lenovo is using STM.

The next interesting to consider is how this design compares to the LBS design of Microvision and Sony in the Celluon projector.   The Lenovo video shows the projector as being about 34mm by 26mm by 5mm thick.  To check this I took the a photo from the STM to CelluonTO SCALE  003Picoprojector.com
article and was able to fit the light engine and electronic into a 34mm by 26mm rectangle arranged as they are in the Lenovo video (yet one more verification that it is STM).   I then took a picture I took of the Celluon board to the same scale and show the same 34x26mm rectangle on it.   The STM optics plus electronics are 1/4 the area and 1/5th the volume (STM is 5mm thick versus Microvision/Sony’s 7mm).

The Microvision/Sony is has probably about double the lumens/brightness of the STM module due to have two green and two red lasers and I have not had a chance to compare the image quality.   Taking out the extra two lasers would make the Microvision/Sony engine optics/heat-sinking smaller by about 25% and have a smaller impact on the board space, but this would still leave them over 3X bigger than STM.   The obvious next question is why.

One reason is that the STM either has a simpler electronics design or is more integrated and/or some combination thereof.  In particular the Microvision/Sony design requires an external DRAM (large rectangular chip in the Microvision/Sony).    STM probably still needs DRAM, but it is likely integrated into one of their chips.

There are not a lot of details on the STM optics (developed by bTendo of Israel before being acquired by STM).   But what we do know is STM uses separate simpler and smaller horizontal and vertical mirrors versus Microvision significantly larger and more complex single mirror assembly.  Comparing the photos above, the Microvision mirror assembly alone is almost as big as STM’s entire optical engine with lasers.   The Microvision mirror assembly has a lot of parts other than the MEMs mirror including some very strong magnets.  Generally the optical path of the Microvision engine requires a lot of space to enter and exit the Microvision mirror from the “right” directions.

btendo optics

On the right I have captured two frames from the Lenovo video showing the optics from two directions.  What you should notice is that the mirror assembly is perpendicular to the incoming laser light.  There appears to be a block of optics (pointed to by the red arrow in the two pictures) that redirects the light down to the first mirror and then returning it to the second mirror.  The horizontal scanning mirror is clearly shown in the video but it is not clear (so I took an educated guess) as to the location of the vertical scanning mirror.

Also shown at the right is bTendo patent 8,228,579 showing the path of light for their two scanning mirror design.   It does not show the more complex block of optics required to direct the light down to the vertical mirror and then redirect it back down to the horizontal mirror and then out as would be required in the Lenovo design.    You might also notice that there is a flat clear glass/plastic output cover shown in the at the 21s point in the video, this is very different from the Microvision/Celluon/Sony design show below.

Microvision mirror with measurements

Microvision Mirror Assembly and Exit Lens

Shown at left is the Microvision/Celluon beam scanning mirror and the “Exit” Lens.   First notices the size and complexity of the scanning mirror assembly with magnets and coils.  You can see the single round mirror with its horizontal hinge (green arrow) and the vertical hinge (yellow arrow) on the larger oval yoke.   The single mirror/pivot point causes an inherently bow-tied image.  You can see how distorted the mirror looks through the Exit Lens (see red arrow); this is caused by the exit lens correcting for the bow-tie effect.  This significant corrective lens is also a likely source of chroma aberrations in the final image.

Conclusions

All the above does not mean that the Leveno/STM is going to be a successful product.   I have not had a chance to evaluated the Lenovo projector and I still have serious reservations about any embedded projector succeeding in a cell phone (I outlined my reasons in an August 2013 article and I think they still hold true).    Being less than 1/5th the volume of the Microvision/Sony design is necessary but I don’t think is sufficient.

This comparison only shows that the STM design is much smaller than Microvisions and Microvision has only made relatively small incremental progress in size since the ShowWX announced in 2009) and Sony so far has not improved on it much, at least so far.

IRIS HUD on Indiegogo Appears to be Repackaged Pioneer HUD(s)

The startup IRIS has started and Indiegogo presale campaign for not just one (a major challenge for a new company)  but two different HUD designs, one “laser” and one DLP based.    Their video and “story” talk about how they designed this HUD and even show some CAD pictures, 3-D printing (of what?), and a CNC milling machine (but not showing what is being made).

The problem is that this “new” unit looks almost identical at every point to Pioneer HUD announced shipped in Japan in 2012 (with a slightly updated version in 2013) see such as, “The Verge” article from May 2012.   Pioneer’s model was also a “Laser HUD” and used a Microvision beam scanning mirror and laser control electronics.

Pioneer then in late 2013 Pioneer introduced a less expensive model based on Texas Instrument’s DLP that I wrote about on Seeking Alpha.   And low and behold IRIS also has a DLP version.  Where the Laser version was sold with Pioneer’s proprietary navigation system, the DLP version was sold in Europe that connect to a smart-phone.

According to IRIS’s Indiegogo campaign,

This limited quantity of Laser (30) and DLP (300) units are being assembled and will be ready to ship at the end of the campaign.  

Assuming that if IRIS is actually going to be delivering these products (that is always a big “if” for a new high-tech product on Indiegogo), the only rational conclusion is that they are shipping Pioneer’s unsold inventory of at least Laser and DLP engines if not whole systems.

Below are a series of comparison photos with alternating photos of the IRIS HUD and the Pioneer Laser HUD.   I have draw lines connecting corresponding elements between the IRIS and Pioneer HUDs.   I will go into some more of the business issues after the photos.

IRIS Pioneer Comparison 003

IRIS does claim to be adding features that were not in the either the Laser or DLP based Pioneer systems, specifically they say they are adding “gesture recognition” and connection to the OBD (on-board diagnostics) port.   Being I think most generous, it could be that they are taking the old unsold Pioneer units and modifying them.   I could be OK with this, but I am always a bit distrustful when I catch someone fudging on what they did.

Pioneer DLP hud2Interestingly, the Pioneer DLP HUD (left) while it worked with smartphones, as does IRIS’s HUD, it looks quite different and it optically different in just about every way but the combiner.   The Pioneer Laser HUD rear projected on a screen behind a large plastic lens that is then viewed via the combiner (the “combiner” is that large curved plastic mostly transparent but slightly mirrored lens at the front of the unit).  The Pioneer DLP HUD front projects on a a screen that is then seen reflected in- and magnified by- the combiner.

Additionally, the Pioneer Laser HUD required you to remove your sun visor to mount the unit where their DLP HUD strapped to the sun visor (see the photo above).   This got me curious how they could be selling two radically different designs that also mounted differently while showing a single product so I posted the follow question and got the response below on IRIS’s Facebook page:

Karl Guttag‎, “Is the case and mounting the same for the Laser and the DLP versions of the product?

IRIS “Yes, Absolutely the same!

I guess it is possible that they took Pioneer Laser HUD cases and reworked/redesigned them to fit the DLP and added gesture recognition and OBD.   That would seem to me to be a pretty major effort for a small team with little known funding.

Yet they say they are going to ship units at the end of their Indiegogo campaign this month which would suggest they have them in-stock.   If they are so close to having real product, then I would have expected them to be out there demonstrating them to reviewers and not just showing the carefully staged video on Indiegogo.   Maybe they have something, but maybe it does not work very well.   Something just does not seem to add up.

BTW, I have had the opportunity to see both the Pioneer Laser and DLP based HUDs.  Frankly, neither one seems very practical.  The Laser HUD requires you to remove your sun visor to mount it and they give you a small sun visor that only goes up and down (can’t block your side window and and does not cover enough).  Additionally unless you are very short, the combiner tends to cut through your critical forward vision.   The DLP version was worse in that it mounted below the sun visor and totally blocks the forward vision if you are tall and/or your seat adjust to a high position.  The bottom line, there are reasons why the Pioneer units did not sell well.

Disclaimer:

I previously worked as CTO for Navdy which is also developing an aftermarket HUD product and could be seen as a competitor for IRIS.  I currently have no financial interest in Navdy.   Because of my prior position at Navdy and knowledge of non-public information, it is not appropriate for me to comment on their product.

Celluon LBS Analysis Part 2B – “Never In-Focus Technology” Revisit

Celluon alignment IMG_9775

After Alignment alignment target (click for bigger image)

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.laser alignment comparison 2

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.

Celluon 72-in diag left-right targets

Center left and center right of 72-in diag. after re-alignment (click on thumbnail for full resolution image)

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).

Celluon 72-in diag  recalibrated IMG_9783

Celluon 72-in diag re-calibrated (click for full size image)

Celluon 22-in diag  recalibrated IMG_9864

Celluon 22-in diag re-calibrated (click for full size image)

Celluon 12-in diag recalibrated IMG_9807

Celluon 12-in diag re-calibrated (click for full size image)

 

 

 

 

interlace res-chart-720P G100A

Test Chart for 1280×270 resolution (click for full resolution)

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.

 

Celluon 72-in diag 85mm Center-Left 9821

85mm Prime Lens Center Left Target and Lines (click for full size image)

Celluon 72-in diag 85mm lens center  9817

85mm Prime Lens Center Target and Lines (click for full size image)

Celluon 72-in diag 85mm center-right 9813

85mm Prime Lens Center-Right Target and Lines (click for full size image)

Karl

Celluon Laser Beam Steering Analysis Part 2 – “Never In-Focus Technology”

June 6th 2015 – Note, I am in the process of updating this analysis with new photos.  The results are not dramatically different but I was able to improve the horizontal resolution slightly and now have some better pictures.    

Celluon image size comparison center cropsOne of the first things I noticed when projecting text pattern images with the Celluon PicoPro was that the images were very blurry.   I later found out that the smaller the image the blurrier it became.

To the left are high-resolution center crops of images taken with a 12-inch diagonal (about as big as you can get on a letter size sheet of paper, a 24-inch diagonal image (about as big as fits on a standard “B” size sheet of paper, and a 72-inch diagonal image I project on a wall.   For reference I have also included a the same portion of the source 3x magnified.

As you should notice the 12-in diagonal image is completely blurry even at 1/2 the stated resolution.  With the 24-inch diagonal you can start to see some “modulation” of the single pixel size lines horizontally but not vertically.  With the 72-inch diagonal the horizontal lines are pretty clear but still the vertical lines are still pretty much a blur (on close visual inspection there is a little modulation of the single pixel wide lines).

What is happening is that size of the laser beams is larger than the pixel size for small images.  The size of the beam diverges but at a slower rate than the size of the image grows so eventually the laser beam size is smaller than a “pixel” and you start to see separation between horizontal 1 pixel wide lines.

As for the horizontal resolution, whatever is driving the lasers in their horizontal sweep is not able to fully modulate them at single pixel resolution.

For the next set of 3 images (plus a 2x Magnified source) I have scale the images down so you can see more area.  Note you need to click on the image to see it at its intended size and to see the detail.  In these pictures you can see the ruler with both indicates the size of the image and shows that the camera was in-focus and could see the detail if it was in the projected image.

On the 24-inch diagonal and 72-in diagonal image I have drawn 3 ovals.  The left oval is around a set of 4 line pairs (see source image) of horizontal and vertical lines.   The middle and right ovals are each around 4 line pairs of vertical lines and two sets of 4 pairs of horizontal lines and where the horizontal and vertical lines cross is a set of 9 white pixels (never visible in any of the projected images).

Looking at the 72-inch image you may notice that you can barely make out the horizontal line pairs in the center oval but that they become blurry in the right oval.  This is due to the interlaced Lissajous scanning being done (for more detail on the Microvision interlaced scanning process see: http://www.kguttag.com/2012/01/09/cynics-guild-to-ces-measuring-resolution/).  The net effect of this scanning process is that vertical resolution is reduce from the center to the left and right sides.

Image Size Comparison

The 5 year old Microvision ShowWX having this blurring issue with small images.  In looking inside at the optics with the lasers on, I notice that the laser spot sizes were larger than expected.  I’m left wondering if the larger laser spot sizes were at least in part cause by efforts to reduce speckle or for some other reason.

Next time, I plan on giving a little “tour” of the optics.

Addendum – How the pictures were taken, full resolution images, and source pattern used

All the pictures were taken with a Canon 70D (5472 by 3648 pixel) DSLR.  By framing the pictures so that filled roughly 90% of the width, this meant there were roughly 4 camera pixel “samples” per pixel in the output image.   The ruler in the picture was both to keep track of the size of the image and to make sure the camera was in-focus and could resolve single pixels (if they were there).

I did selectively zoom in with the camera on smaller regions to see if it made any measurable difference in resolving features in the images and it did not.  I have included the test pattern I used and would welcome anyone using it to verify what I have shown.

By clicking on the thumbnails below you will bring up the full size image (depending on your browser it may not display full size until after you click on the magnifying glass).  You can then right click to download the images.   Each image is about 8 to 9 Megabytes and is stored in a high quality (low compression) JPG format.   The source test pattern is stored in loss-less PNG.

12-inch Diag Celluon_8572

12-in Diagonal Celluon Image (20 megapixels-click to see full size image)

24-inch Diag Celluon_8452

24-in Diagonal Celluon Image (20 megapixels click to see full size image)

72-inch Diag Celluon_8205

72-in Diagonal Celluon Image (20 megapixels click to see full size image)

Basic res-chart-720P

Test Pattern Source (1280×720 pixels PNG format, click for full size image)

Celluon Laser Beam Scanning Projector Technical Analysis – Part 1

Celluon Light Path w800 IMG_8087The 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).

Sony Devices IMG_9737

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.

Celluon test pattern comparison

720P Celluon Projected Image with Source Below It with key comparison point indicated by the red ovals

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):

  1. 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.
  2. The Celluon eliminated the “bowtie” effect of earlier Microvision ShowWX product so that the image is rectangular
  3. 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.
  4. Low effective resolution – absolutely nowhere close to 720p (see above, more on this in future articles).
  5. 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 http://www.kguttag.com/2012/01/09/cynics-guild-to-ces-measuring-resolution/ for more on the scan process and how it hurts resolution).
  6. 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)
  7. 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).
  8. 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.
  9. 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.

interlace res-chart-720P G100A

 

Simple horizontal gray ramp.  This is totally neutral gray from 0 to 255.Horz 0 to 255 gray ramp

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.

gray 16

 

I’m Back

Hi everyone,

Just a quick note today to say that I no longer at Navdy and I now have some time to get back to posting on this blog.   All the travel and work at a start-up was pretty all consuming.

I have some idea for some topics particularly related to the various head mounted display goings on from Google “Glass” to Microsoft’s recent “HoloLens.”   I also want to write more on the computer and game system history.   I like answering questions and would like suggestions for topics so please feel free to write.

The one thing I ask is that there be no questions directly related to Navdy as it would not be appropriate for me to answer them.   It is not going to make good reading for me to have to repeatedly reply with “no comment” or the like.   Almost everything else related to technology, projection, head mounted displays, lasers, computer/video-game history is fair game.

Oh yes one more thing, I am available again for consulting work.

Karl

Navdy Launches Pre-Sale Campaign Today

Bring Jet-Fighter Tech to Your Car with NavdyIts LAUNCH Day for Navdy as our presale campaign starts today. You can go to the  Navdy site to see the video.  It was a little over a year ago that Doug Simpson contacted me via this blog asking about how to make a aftermarket heads up display (HUD) for automobiels.     We went through an incubator program called Highway1 sponsored by PCH International that I discussed in my last blog entry.

The picture above is a “fancy marketing image” that tries to simulate what the eye sees (which is impossible to do with a camera as it turns out).   We figures out how to do some pretty interesting stuff and the optics works better than I thought was possible when we started.    The image image focuses beyond the “combiner/lens” to help with the driver seeing the images in the far vision is about 40 times brighter (for use in bright sunlight) than an iPhone while being very efficient.

Navdy Office

Being CTO at a new start-up has kept me away from this blog (a start-up is very time consuming).  We have raise some significant initial venture capital to get the program off the ground and the pre-sale campaign takes it to the next level to get products to market.  In the early days it was just me and Doug but now we have about a dozen people and growing.

Karl

Whatever happened to pico projectors embedding in phones?

iPad smBack around 2007 when I was at Syndiant we started looking at the pico projector market, we talked to many of the major cell phone as well as a number of PC companies and almost everyone had at least an R&D program working on pico projectors.  Additionally there were market forecasts for rapid growth of embedded pico projectors in 2009 and beyond.  This convinced us to develop small liquid crystal on silicon (LCOS) microdisplay for embedded pico projectors.  With so many companies saying they needed pico projectors, it seemed like a good idea at the time.  How could so many people be wrong?

Here we are 6 years later and there are almost no pico projectors embedded in cell phones or much else for that matter.   So what happened?   Well, just about the same time we started working on pico projectors, Apple introduced their first iPhone.    The iPhone overnight roughly tripled the size of the display screen of a smartphone such as a Blackberry.  Furthermore Apple introduced ways to control the screen (pinch/zoom, double clicking to zoom in on a column, etc.) to make better use of what was still a pretty small display.   Then to make matter much worse, Apple introduce the iPad and tablet market took off almost instantaneously.    Today we have larger phones, so called “phablets,” and small tablets filling in just about every size in between.

Additionally I have written about before, the use model for a cell phone pico projector shooting on a wall doesn’t work.   There is very rarely if ever a dark enough place with something that will work well for a screen in a place that is convenient.

I found that to use a pico projector I had to carry a screen (at least a white piece of paper mounted on a stiff board in a plastic sleeve to keep clean and flat) with me.   Then you have the issue of holding the screen up so you can project on it and then find a dark enough place that the image looks good.    By the time you carry a pico projector and screen with you, a thin iPad/tablet works better, you can carry it around the room with ease, and you don’t have to have very dark environment.

The above is the subjective analysis, and the rest of this article will give some more quantitative numbers.

The fundamental problem with a front projector is that it has to compete with ambient light whereas flat panels have screens that absorb generally 91% to 96% of the ambient light (thus they look dark when off).     While display makers market contrast number, these very high contrast numbers assume a totally dark environment, in the real world what counts is the net contrast, that is the contrast factoring in ambient light.

Displaymate has an excellent set of articles (including SmartPhone Brightness Shootout, Mobile Brightness Shootout 2, and Smartphone Shootout 2) on the subject of what they call “Contrast Rating for High Ambient Light” (CRHAL)  which they define as the display brightness per unit area (in candela’s per meter squared, also known as “nits”) of the display divide by the reflectivity of ambient light in percent by the display.

Displaymate’s CRHAL is not a “contrast ratio,” but it gives a good way to compare displays when in reasonable ambient light.  Also important, is that for a front projector it does not take much ambient light to end up dominating the contrast.  For a front projector even dim room light is “high ambient light.”

The total light projected out of a projector is given in lumens so to compare it to a cell phone or tablet we have to know how big the projected image will be and the type of screen.   We can then compute the reflected light in “nits”  which is calculated by the following formula Candelas/meter2 = nits = Gn x (lumens/m2)/PI (where Gn is the gain of the screen and PI = ~3.1416).   If we assume a piece of white paper with a gain of 1 (about right for a piece of good printer paper) then all we have to do is calculate the screen area in meters-square, multiply by the lumens and divide by PI.

A pico projector projecting a 16:9 (HDTV aspect ratio) on a white sheet of notebook paper (with a gain of say 1) results in 8.8-inch by 5-inch image with an area of 0.028 m2 (about the same area as an iPad2 which I will use for comparison).    Plugging a 20 lumen projector in to the equation above with a screen of 0.028 m2 and a gain of 1.0 we get 227 nits.  The problem is that same screen/paper will reflected (diffusing it) about 100% of the ambient light.   Using Displaymate’s CRHAL we get 227/100 = 2.27.

Now compare the pico projector numbers to an iPad2 of the same display area which according to Displaymate has 410 nits and only reflects 8.7% of the ambient light.   The CRHAL for the iPad2 is 410/8.7  = 47.   What really crushes the pico projector by about 20 to 1 with CRHAL metric is that the flat panel display reflects less than 10th of the ambient light where the pico projector’s image has to fight with 100% the ambient light.

In terms of contrast,to get a barely “readable” B&W image, you need at least 1.5:1 contrast (the “white” needs to be 1.5 brighter than the black) and preferably more than 2:1.   To have moderately good (but not great) colors you need 10:1 contrast.

A well lit room has about 100 to 500 lux (see Table 1 at the bottom of this article) and a bright “task area” up to 1500 lux.   If we take 350 lux as a “typical” room then for the sheet of paper screen there are about 10 lumens of ambient light in our 0.028 m2 image from used above.   Thus our 20 lumen projector on top of the 10 lumens of ambient has a contrast ratio of 30/10 or about 3 to 1 which means the colors will be pretty washed out but black on white text will be readable.  To get reasonably good (but not great) colors with a contrast ratio of 10:1 we would need about 80 lumens.   By the same measure, the iPad2 in the same lighting would have a contrast ratio of about 40:1 or over 10x the contrast of a 20 lumen pico projector.   And the brighter the lighting environment the worse the pico projector will compare.    Even if we double or triple the lumens, the pico projector can’t compete.

With the information above, you can plug in whatever numbers you want for brightness and screen size and no matter was reasonable numbers you plug in, you will find that a pico projector can’t compete with a tablet even in moderate lighting conditions.

And all this is before considering the power consumption and space a pico projector would take.   After working on the problem for a number of years it became clear that rather than adding a pico projector with its added battery, they would be better off to just make the display bigger (ala the Galaxy S3 and S4 or even the Note).   The microdisplay devices created would have to look for other markets such as near eye (for example, Google Glass) and automotive Heads Up Display (HUD).

Table 1.  Typical Ambient Lighting Levels (from Displaymate)

Brightness Range

Description

0 lux  –

100 lux  –

500 lux  –

1,000 lux  –

3,000 lux  –

10,000 lux  –

20,000 lux  –

50,000 lux  –

100,000 lux  –

100 lux

500 lux

1,500 lux

5,000 lux

10,000 lux

25,000 lux

50,000 lux

75,000 lux

    120,000 lux

Pitch black to dim interior lightingResidential indoor lighting

Bright indoor lighting:  kitchens, offices, stores

Outdoor lighting in shade or an overcast sky

Shadow cast by a person in direct sunlight

Full daylight not in direct sunlight

Indoor sunlight falling on a desk near a window

Indoor direct sunlight through a window

Outdoor direct sunlight

Extended Temperature Range with LC Based Microdisplays

cookies and freezing

Extreme Car Temperatures

A reader, Doug Atkinson, asked a question about meeting extended temperature ranges with LC based microdisplays, particularly with respect to Kopin.    He asked the classic “car dash in the desert and the trunk in Alaska” question. I thought the answer would have broader interest so I decided to answer it it here.

Kopin wrote a good paper that is available on the subject in 2006 titled “A Normally Black, High Contrast, Wide Symmetrical Viewing Angle AMLCD for Military Head Mounted Displays (HMDs) and Other Viewer Applications”. This paper is the most detailed one readily available describing the how Kopin’s transmissive panels meet the military temperature and shock requirements.  It is not clear that Kopin uses this same technology for their consumer products as this paper is specifically addressing what Kopin did for military products.

With respect to LC microdisplays in general, it should realized that there is not a huge difference in the technical spec’s of the liquid crystals between the LC’s  most small panel microdisplays use and large flat panels in most cases. They often just use different “blends” of the very similar materials. There are some major LC differences including TN (twisted nematic), VAN (vertically aligned nematic), and others.   Field sequential color are biased to wanting faster switching “blends” of the LC.

In general, anywhere a large flat panel LC can go, a microdisplay LC can go. The issue is designing the seals and and other materials/structures to withstand the temperature cycling and mechanical shock which requires testing,  experimentation, and development.

The liquid crystals themselves generally will go through different phases from freezing (which is generally fatal) to heating up to the the “clearing point” where the display stops working (but is generally recoverable).  There is also a different spec for “storage temperature range” versus “operating temperature range.” Generally it is assumed the device only has to work in a temperature range in which a human could survive.

At low temperature the LC gets “sluggish” and does not operate well but this can be cured by various “heater mechanisms” including having heating mechanisms designed into the panel itself.  The liquid crystal blends are often designed/picked to work best at a higher temperature range because it is easier to heat than cool.

Field sequential color LCOS is more affected by temperature change because temperature affects not only the LC characteristics, but the switching speed. Once again, this can be dealt with by designing for the higher temperature range and then heating if necessary.

As far as Kopin’s “brightness” goes (another of Doug’s questions), a big factor is how powerful/bright the back light has to be. The Kopin panel blocks something like 98.5% of the light by their own spec’s. What you can get away with in a military headset is different than what you may accept in a consumer product in terms of size, weight, and power consumption. Brightness in daylight is a well known (inside the industry) issue for Kopin’s transmissive panels and one reason that near eye display makers have sought out LCOS.

[As an aside for completeness about FLC]  Displaytech which was sold the Micron and then sold to Citizen Finetech Miyota and the Kopin bought Forth Dimension Display (FDD) both use Ferro-electric LC (FLC / FLCOS) which does have a pretty dramatically different temperature profile that is very near “freezing” (going into a solid state) a little below 0C which would destroy the device. Displaytech claimed (I don’t know about FDD) that they had extended the low temperature range but I don’t know by how much. The point is that the temperature range of FLC is so different that meeting military spec’s is much more difficult.

Sony and Sumitomo

Sorry for being away from the blog so long.  I had two big “consulting gigs” come in one right after the other and I have been working virtually non-stop for the last 6 weeks.  There has been a lot of news come in that period in the area of displays and lasers and I will try and get caught up on some of it.

Today I would like to talk about Sony and Sumitomo announcement of a 530nm 100mW Green laser with 8% efficiency.  At least on the surface, this appears to be a big improvement what Soraa, Osram, and Nichia have announced to date.   But the big question is whether this really changes anything for pico projectors?

Semiconductor laser diode/True green laser emitting

Sumitomo and Sony 530nm Direct Green Laser Diode

Sony was much quieter than Soraa, OSRAM and Nichia but it certainly should have been expected since they developed blue lasers for blue ray (see for example from 2007 “Sony’s Blue Laser Diodes Down to $8 – PS3 and BD Player Price Cuts Soon?”).  Sumitomo had announce they were working on green laser materials back in 2010 but they were not known as a maker of laser diode end products and were thought to be a material supplier (to Sony as it turns out).

Another company to watch would be Opnext who is a leader in red lasers and announced a blue laser diode back in January 2011. All the green laser diode developments I know of came from “stretching” their blue laser developments to get green.

Certainly the Sony-Sumitomo device looks on the spec’s to be significantly better than other companies’ prior announcements with a 100mW, 530nm wavelength (huge improvement over the others), and 8% efficiency.  When you factor in the luminous efficiency at 530nm, they appear to have about double the lumens/Watt of any other green laser announcement I have seen.

Something else to consider, Sony has long been a manufacture of LCOS devices so I would suspect (I have no inside knowledge) that Sony would be looking to couple this laser with their LCOS developments.  They also have the ability to make some very small pixels from their in high resolution LCOS devices.  But the question is whether they and support field sequential color which it necessary for making small embeddable devices.  It should be noted that Sony has a line of  embedded pico projectors in video cameras that use TI’s DLP®

With all this activity and the seeming much improved spec’s from Sony-Sumitomo does this change everything and will laser projectors soon be everywhere?  Unfortunately, I don’t see this as changing things much, at least in the next year few years.

Now the bad news and just based on what they have said.  A 100mW 530nm green laser only supports about a 20 lumen projector which is pretty dim except for a pretty dark room or a very small image. A projector using an 8% WPE green laser probably does not have net an efficiency advantage (after factoring in all the pro’s and con’s) over a good LED projector with at 20 lumens.  While this might have been an interesting product a couple of years ago, the market has mostly moved on to higher lumen projectors.

And then we have to some questions that were not in the release.  Such as how far away is the Sony-Sumitomo green laser diode is from being a product and how much will it cost. Today a green LED to support a 20 lumen projector probably costs about $2. I think there is a serious question as to whether a ~20 lumen project has a value proposition today even if the lasers were inexpensive by the time you factor in the rest of the projector cost.

My bottom line is that it looks like Sony and Sumitomo have made some great technical progress, but it is does not appear to be enough to have a seriously competitive volume product in the market any time soon.    Anyway, that is the way I see it,

Karl