Archive for Laser Projection

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

 

AR Display Device of the Future: Color Filter, Field Sequential, OLED, LBS and other?

I’m curious what people think will be the near eye microdisplay of the future.   Each technology has its own drawbacks and advantages that are well known.   I thought I would start by listing summarizing the various options:

Color filter transmissive LCD – large pixels with 3 sub-pixels and lets through only 1% to 1.5% of the light (depends on pixel size and other factors).  Scaling down is limited by the colors bleeding together (LC effects) and light throughput.  Low power to panel but very inefficient use of the illumination light.

Color filter reflective (LCOS) – same as CF-transmissive but the sub-pixels (color dots) can be smaller, but still limited scaling due to needing 3 sub-pixels and color bleeding.  Light throughput on the order of 10%.  More complicated optics than transmissive (requires a beam splitter), but shares the low power to panel.

Field Sequential Color (LCOS) – Color breakup from sequential fields (“rainbow effect”), but the pixels can be very small (less than 1/3rd that of color filter).   Light throughput on the order of 40% (assuming a 45% loss in polarization).  Higher power to the panel due to changing fields.  Optical path similar to CF-LCOS, but to take advantage of the smaller size requires smaller but higher quality (low MTF) optics.   Potentially mates well with lasers for very large depth of focus so that the AR image is in focus regardless of where the user’s eyes are focused.

Field Sequential Color (DLP) – Color breakup form FSC but can go to higher field rates than LCOS to reduce the effects.   Device and control is comparatively high powered and has a larger optical path.  The pixel size it bigger than FSC LCOS due to the physical movement of the DLP mirrors.   Light throughput on the order of 80% (does not have the polarization losses) but falls as pixel gets smaller (gap between mirrors is bigger than LCOS).    Not sure this is a serious contender due to cost, power of the panel/controller, and optical path size, and nobody I know of has used it for near eye, but I listed it for completeness

OLED – Larger pixel due to 3 color sub-pixels.  It is not clear how small this technology will scale in the foreseeable future.  OLED while improving the progress has been slow — it has been the “next great near eye technology” for 10 years.   Has a very simple optical path and potentially high light efficiency which has made it seem to many like on technology with the best future, but it is not clear how it scales to very small sizes and higher resolution (the smallest OLED pixel I have found is still about 8 times bigger than the smallest FSC LCOS pixel) .    Also it is very diffuse light and therefore the depth of focus will be low.

Laser Beam Steering – While this one sounds good to the ill-informed, the need to precision combine 3 separate lasers beams tends to make it not very compact and it is ridiculously to expensive today due to the special (particularly green) lasers required.  Similar to field sequential color, there are breakup effects of having a raster scan (particularly with no persistence like a CRT) on a moving platform (as in a head mount display).   While there are still optics involved to produce an image on the eye, it could have a large depth of focus.   There are a lot of technical and cost issues that keep this from being a serious alternative any time soon, but it is in this list for completeness.

I particularly found it interesting that Google’s early prototype used a color filter LCOS and then they switched to field sequential LCOS.    This seems to suggest that they chose size over issues with the field sequential color breakup.    With the technologies I know of today, this is the trade-off for any given resolution; field sequential LCOS pixels are less than 1/3rd the size (a typically closer to 1/9th the size) of any of the existing 3-color devices (color filter LCD/LCOS or OLED).

Olympus MEG4.0

Olympus MEG4.0 – Display Device Over Ear

It should also be noted that in HMD, an extreme “premium” is put on size and weight in front of the eye (weight in front of the eye creates as series of ergonomic and design issues).    This can be mitigated by using light guides to bring the image to eye and locating a larger/heavier display device and its associate optics to a less critical location (such as near the ear) as Olympus has done with their Meg4.0 prototype (note, Olympus has been working at this for many years).  But doing this has trade-offs with the with the optics and cost.

Most of this comparison boils down to size versus field sequential color versus color sub-pixels.    I would be curious what you think.

Laser Illumination Could Cause LCOS to Win Out Over OLED in Near Eye AR

Steve Mann IEEE adapted

The conventional wisdom is that eventually OLEDs will become inexpensive and they will push out all other technologies in near eye because they will be smaller and lighter with a simple optical path.   But in reading ‘Steve Mann: My “Augmediated” Life”‘ in IEEE Spectrum I was struck by his comment “It requires a laser light source and a spatial light modulator”  (a spatial light modulator are devices like LCOS, transmissive panels, and DLP).     The reason he gives for needing a laser light source is to support a very high depth of focus.   For those that don’t believe LCOS and lasers give a high depth of focus you might want to look at my blog from last year (and the included link to a video demonstration).

Steve Mann has “lived the dream” of Augmented Reality for 35 years and (with due affection) is a geek’s geek when it comes to wearing AR technology.  He makes what I think are valid points as to what he finds wrong about Google Glass including the need to have the camera’s view concentric with the eye’s view and issues of eye strain in the way the Google Glass image is in the upper corner of your field of view which can cause eye muscle strain.

But the part of Steve Mann’s article really caught my attention is the need for laser illumination to give a high depth of focus to reduce eye strain because you need what you see in the images to be in focus at the same depth as what you see in the real world.     Google Glass and other LED illuminated AR generally set the focus so that the display focuses in what would be a persons far vision.   Steve Mann is saying is that the focus in your eye from the display has to match that of the real world or there will be problems and the only known way to do this is to use laser illumination.

This issue of laser light having a large depth of focus when used with a panel is an important “gem” that could have a big impact in terms of the technology used in near eye AR in the future.   LEDs and that includes OLEDs produce light with rays that are scattered and hard to focus.   Wheres lasers produce high f-number light that is easy to focus (and requires smaller optics as well).  As I said at the top of this post, the conventional wisdom is that cost is the only factor keeping OLEDs out of near eye AR, but if Steven Mann is correct, they are also prevented from being good for AR due to the physics of light.   And the best technology I know of for near eye AR to mate up with laser light is LCOS.

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

Lasers – DGL, SHG, and Hybrid

I have no doubt that eventually all projection devices will use laser illumination due to their huge optical advantage.    But there still remain serious technical and business questions as to when they will become a major factor in displays.   A couple of years back we were in the “wild enthusiasm stage” of direct green laser (DGL) development with several companies announcing they had a direct green laser.    But since then, it has become clear that there are still some significant technical and business hurdles to clear for DGL.

The immediate effect of the DGL announcements two years ago was to make the development of second harmonic generation (SHG) and other diode pumped green lasers more difficult as it tended to make the funding and management support of developments in SHG lasers more difficult.      Since then it has become clear that while the DGL developments were very promising, they were still a very long way from being ready for production products.

Simply put, it turns out that the physics for making DGL is very difficult.  All the DGL development are based on around indium gallium nitride (InGaN).  Semiconductor today had a very good article on the subject in 2009  (note UCSB developments led to today’s Soraa).  To get to green they have had to add more indium and to try different crystal plane orientations which are less stable/yieldable.   To have a production product they have to solve simultaneously key attributes including the yield/cost, wavelength/color, stability/lifetime, output power, temperature range, and efficiency.    To date, they can only solve a few of these key attributes at the same time.    I sometimes quip, “I can get everything I want in a green laser but it is spread over 5 different parts.”

It also seems very clear that DGL are at best only going to have enough power output to support low projectors for the next several years.   The big problem is that low lumen projects have low value in the market which means that can’t afford expensive DGL.   This is creating a very big chicken or the egg problem in that there really is no significant market for early expensive, low efficiency DGL.

As reality sets in on DGL progress, there seems to be a resurgence of interest in SHG green technologies.  Getting DGL powerful enough to support the hundreds of lumens for a portable projector and the thousands and tens of thousands of lumens for conference room projector could be more than a decade away.   Companies need the optical advantages of an all laser solution to provide higher efficiency, smaller and less expensive optics, better efficiency, and long lifetimes, than traditional lamps, and they can’t wait on DGLs.

There are several techniques for getting green lasers by pumping crystals with lasers of a different wavelength.   Most commonly this is done by using an infrared laser at 808nm to pump a non-linear crystal (often periodically poled lithium niobate {PPLN}) to generate the second harmonic at 532nm green.   Spectralus   and QD Laser are two small companies with promising developments for relatively efficient SHG green lasers.

One issue with using a SGH and combining it with say direct diode blue and red lasers is that each of the lasers has a different character/beam profile and ages differently which can cause color shifts that would require constant recalibration to achieve accurate colors.   Also the direct red lasers that are available are at about 640nm which while a very deep/saturated red; it is very inefficient in terms of perceived lumens.   A more “ideal” red wavelength is in the 615nm to 620nm range but just like with trying for a 532 green, it has proven difficult to make stable/yielding red lasers in much below about 635nm.   These factors and others have caused the current large laser projector developers, such as Laser Light Engines, to use SHG for red, green, and blue even though direct diode red and blue lasers exist that could produce enough light.

Photodigm  has a more radical approach where all three colors (plus orange) could be generated from a single infrared pump source.   This could be particularly useful and very cost effective in the mid-lumen (say 100 to 3,000 lumen) projectors which use field sequential color such as DLP and LCOS.    Philips at SID 2011 also proposed a single laser only this time a blue laser to pump a crystal to provide red green blue and orange.

Another development pioneered by Casio is the “hybrid” laser projector.  In these projectors they use a red LED and blue laser for blue and use either the same blue laser through a spinning wheel or a second blue laser to drive a green phosphor to get green.    The “green” is not tightly collimated laser light and is not ideal from an optical perspective, but it is the cheapest way to get a very bright and small green light source.  Using blue lasers to stimulate a green phosphor is an admission that DGL, at least bright ones, are a ways off.    There is a so much buzz in the industry about this hybrid green approach that market analyst Insight Media has release a report on it (http://www.insightmedia.info/reports/2012hybriddetails.php)

My conclusion is that projector makers aren’t going to be waiting around for DGL to get going with laser projection.    It is clear that the hybrid/phosphor-green approach is already taking off for 2K to 3K lumens.   I also foresee the hybrid approach migrating down into the 200 to 1000 lumen markets.   But there are bigger overall advantage with smaller optics and microdisplays to be had by having an all laser solution.

Soothsayer 6: Microvision’s Lance Evans “Green lasers alone are $200 each now”

First, sorry for being away so long.  Some family and other matters took me a way and I fell out of the habit of posting.  I am going to try to have at least couple of posts up a week.

My “Soothsayer” series started back in December 2011 when Microvision released an 8-K a very trasparent response to this blog.  In Microvision’s Dec. 19th 2011 8-K they stated ““In the coming weeks we intend to provide a series of posts that discuss direct green lasers in more detail, as well as other business updates. Stay tuned!”

Well, it has been 19 weeks since Microvision’s 8K and there has been pretty much silence from them on “more details.”  Microvision has had plenty of opportunities to add “more details” in the last 5 months but has chosen not to.  They say a “slip in Washington is when you accidentally tell the truth” well maybe Microvision did that today.

In a way, Microvision finally broke the silence with an article today in an April 30th Technology Review article with Lance Evans (a director of business development at Microvision) stating, “Green lasers alone are $200 each now.” Remember this is probably for a green laser that supports on the order of a 15 lumen projector and has a wavelength that is too short (too blue) to be used in a typical projector and it not very efficient in terms of lumens per Watt. These are lasers that are a best useable in a car HUD display and not a batter powered cell phone or hand held projector.

Back in December 2011 Microvision’s 8K stated, “DGLs will be much cheaper than synthetic green lasers at introduction.”  How does this fit with DGL’s costing $200 today? 

The article does day that “Evans expects that costs should fall to a tenth of current levels by the end of this year,” but note the word “expects” is corporate speak for “believe, wish, hope, or dream” because you generally can’t hold them legally accountable for an “expectation.”  What other than a wish causes the direct green laser cost road map to drop from $200 now to one-tenth that cost or $20 in less than 7 months?  Are there people lined up to buy lasers first at $200, then $100, then $50 say to support a 15 lumen projector?  None of this makes any business sense.

Even if Mr. Evans “expectations” come true, and DGL drop by 10x in less than 7 months to $20 by the end of the year (really for 2013 production), is this really a viable business?   By comparison, there are 200 lumen LED base projectors on the market today and the cost of the red, green, and blue LEDs combined cost less than $20 today.   For a 15 lumen LED projector today, the LEDs are more like $3 for the RGB set.  For a pico projector to make it into a cell phone, the cost to the cell phone maker of the whole projector including electronics has to be on the order of $25 or less (just ask any cell phone maker, I have asked many).  You can even come close with even a $10 DGL, no less 20, when you factor in the cost of everything it takes to make a projector including optics and electronics.

I’m a long term believer that eventually all projectors and in fact a vast number of other products will be using lasers.   It is just going to take more than 2 year for the brilliant people at the laser manufactures to figure out how to make the direct green lasers at a cost point that will lead to mass adoption.

Answering Questions on Laser with LCOS and LBS

Syndiant 720p LCOS Panel

I got asked a series of questions by reader “me_wwwing” after the article Laser with LCOS is Focus Free — Yes Really! that I am answering in this post because I thought they would be of general interest.  I did have to edit a few of the questions for clarity but tried to keep the intent as best I could and I have re-ordered the questions to put what I think are the more interesting questions first.   For background for the reader I need to add that from prior questions and comments, I know me_wwwing to be a fan of Microvision’s laser beam scanning (LBS) so that may color some of the questions and the answers.

Q1. Does Syndiant need to use the same lasers as MVIS [Microvision laser beam scanning (LBS)]?

The simple answer is that LCOS panels can use any of the lasers that LBS can use and can use lasers that LBS cannot use.   LBS puts constraints on both Diode Pump Solid State Lasers (DPSS also known as “synthetic” or “frequency doubled) and for direct diode lasers (DGL).

Answer Part 1: DPSS Green Lasers

First, Syndiant makes the LCOS microdisplays and not the entire optical engine.     A panel (LCOS or DLP) optical engine has a wider selection of lasers that it can use both for direct green lasers as well as DPSS green lasers.   So the quick answer is that it can use any of the lasers that a LBS system can use plus it can use laser types and variation that LBS cannot use.

With DPSS green lasers, panels could use the less expensive to make and much more electrically efficient (generally about 2X the efficiency) slower switching lasers.  The slower switching frequency doubled lasers are capable of greater than 12% wall plug efficiency (WPE) with the desirable 532nm wavelength green.   About the best the fast switching frequency double green lasers ever got to was about 6% WPE.

The slower switching DPSS greens are capable of going to very high brightness; they can be over 10 times brighter than today’s Direct Green Diode Lasers (DGL).   Their electrical to lumen efficiency is over 3X the best DGLs today.   And their cost is lower than DGLs.   But the drawbacks to DPSS greens include the size and the small spectral bandwidth that causes higher speckle.

Answer Part 2: Direct Green Diode Lasers (DGL)

It turns out that there are different kinds of direct-diode lasers as well.  Most notably there are “single mode” and “multi-mode” lasers.

LCOS or DLP can use either the single-mode or multi-mode lasers, but lasers LBS can only use single-mode lasers.   Multi-mode lasers change wavelength, phase, and/or optical polarity somewhat randomly.  The rate of mode changing would look like noise in a LBS scanning process so it is unusable in an LBS system, but in a panel (LCOS or DLP) system the hopping simply gets average out as it is faster than the eye can detect.

Since changing wavelength and phase reduces speckle, multimode lasers have less speckle.  It turns out that lasers naturally want to mode hop, so it is easier (cheaper) to make multimode lasers, multimode lasers are more electrically efficient and multi-mode lasers can be made much brighter/more powerful (in fact, as they make the laser cavity bigger to make lasers more powerful it is hard to keep them from mode hopping).  So panel based projectors have a significant advantage in being able to use multi-mode lasers.

Historically, traditional laser uses such as telecom and interferometry, needed single mode lasers.   But the same coherent light for these applications is what causes speckle, so for panel based projectors you want “poor quality” lasers with less coherency and thus speckle.

Q2. How big is Syndiant Controller?

The Syndiant’s 720p ASIC is currently 9mm X 9mm in its current package, but could be put in a significantly smaller package by reducing the pin count for an embedded cell phone.  The current package has a lot of extra pins for supporting a mix of applications that make it bigger.

Q3. What are the dimensions of Syndiant’s PCB?  The new one or the old one to have a starting point.

Syndiant sells the panel and the driver ASIC and not a PCB per say.  Single SYA1231 ASIC for their 720p is currently 9mm x 9mm includes frame buffer memory and ARM CPU and can be put in a smaller package for embedded applications.    So there really isn’t much in the way of board space for the new Syndiant 720p controller.  Basically, it is just one small chip 9mm X 9mm chip and not a “PCB” per say.

Syndiant’s single small ASIC compares extremely favorably to the Microvision 720p board which has 2 custom ASICS (one about ~11mm x 11mm and the other ~10mm x 10mm)  and an Altera FPGA (~6mm x 6mm)  on it.  There is also a 4th I.C. on their board which is an Intersil laser driver (5mm x 5mm).   The  picture below is from www.technogytell.com with my notes added it:

Microvision "720p" Optics and Driver Board

Totalling up the area of Microvision’s two ASICs and FGPA, Syndiant’s current control ASIC takes about 1/3rd the area and 1/3rd the ICs of Microvision’s 3 chip controller.   Also just looking at all the power conversion circuitry required in the Microvision “720p” board suggests that it needs a lot of different voltages with some significant power requirements and all this adds cost, board space, and power.

Q4. What size diagonal lens (encased) does Syndiant’s displays need to cover the diagonal of the display?  A length too would be nice. old specs are ok to start with [assuming laser illumination]

The diagonal of the “active display” of the older SYL2010 was 0.21”.  It had a 5.4 micron (10-6 meter)  pixel such that an 800 pixel high display was 4.3mm.   The lens would need to be a bit thicker than this diagonal.  For a small high volume product the lens would be cut to a more rectangular than circular shape to reduce height.   So the lens could be about 6 mm thick.   The SSTDC SEE100 prototype engine http://www.picoprojector-info.com/laseno-see100-module-photo  engine’s lens with its barrel was non-optimized (circular) and was about 8mm thick and 8mm long.  An optimize rectangular-cut lens could have been about 5mm tall.

There is nothing keeping LCOS with laser illumination from going below 5 micron pitch (they will eventually get to around 3 micron and perhaps less) for its pixels.   At about 5 microns the active display for a 720p would be about 3.6mm tall.  A rectangular cut lens would then be about 4.5mm to 5mm tall or a round lens would be about 7mm tall.

Q5. Does the dichroic color combiner lens need to cover the surface of the Vibrating Despeckle unit [the answer addresses the broader question of the light combining system for LCOS and LBS]?

No, the light is not significantly spread out before the dichroic color combiners in an LCOS system.  Also the alignment of the dichroic mirrors/filters and the lasers is non-critical in an LCOS or DLP optical engine.

In should note, however that the alignment of the lasers and the dichroic combiners is very critical in an LBS design.  You should note in this teardown picture (picture taken from a laserpointerforums) that I have labeled the two ball shaped optics (pointed to in magenta) used to aligned the red and blue lasers and then glued into place.   The need to critically align the lasers adds cost and quality issues into to the manufacturing process.

Microvision ShowWX (WVGA) Optics

 

Q6. What is the power to run the PCB and the light engine on a Syndiant’s Displays? (SVGA and WVGA).

That really is a complex and involved question and depends on a lot of factors including the optical engine design and the target brightness.  I am also assuming that this is with LED illumination.   With LEDs the lumens per Watt of power tends to go down as the projector gets brighter, that is one of the advantages with lasers, namely that efficiency does not go down with power. 

It is helpful to break the power into two part, the panel and controller electronics and then the illumination and optics.   For low lumen (less than 30 lumen) projectors, the power of the display and its control is a significant part of the overall power (and less so at higher brightnesses).

The Syndiant LCOS display and ASIC for the WVGA or SVGA will usually consumed about 0.4W.   Due to a number of design improvements, Syndiant’s 720p panel and ASIC consume less power while have a higher color field rate and better light throughput than the older WVGA and SVGA devices while having about 3X the pixels.

In the low lumen area of 10 to 15 lumens with a small, 0.21” WVGA or SVGA panel optical companies were able to get about 7 to 10 lumens per LED Watt.    With some power conversion overhead and including the panel and ASIC this mean that you could get with LEDs about 12 to 15 lumens for 2W of power.  While this is still not good enough for the very high volume cell phone applications, it compares very favorably to the ShowWX which takes 4+ Watts for about 15 lumens.

With lasers the efficiency depends heavily on the lasers used and is dominated by the green laser efficiency which is pretty poor with today’s DGLs.   With today’s DGL efficiencies, LEDs will produce more lumens per Watt, but this will change in the future as lasers improve.   I fully expect to see eventually over 30 lumens per Watt with DGL and LCOS because today with the current DGL, they would be doing well to get 3 to 5 lumens per Watt .

Q7. What would be the lumen output from Syndiant’s displays using the new lasers that Microvision will use [this question was edited for clarity].

This is not a simple question as the spec’s on the lasers and how they can be driven have not been finalized.   I’m pretty sure the lasers that Microvision was using “lab prototype” lasers at CES that were being “over driven.”  The best I can answer right now is to give some insight into the lumens per watt that can be expected as the lasers are perfected.

To begin with, the optical throughput for a laser/LCOS engine should be in the 30% to 40% range where for LBS the optical throughput is reported to be in the 55% to 60% range.   But note, this is the part of the system were LBS looks best in terms of efficiency, but this does not tell the whole story.

Where LBS looses in terms of efficiency is in the drive and control of the laser and the MEM’s mirror.    The Microvision MEM’s mirror alone (not including the ASICs and FPGA’s) at WVGA has been reported to take about 0.4 Watts.   Syndiant’s new 720p LCOS Microdisplay and ASIC combined will take less than that.   Then you have all the power of the 2 ASIC’s and the FPGA that the Microvision 720p board requires.    So LCOS starts with a big lead in terms of power just in power of the display and control.

Then we have biggest power wasters for LBS, that of having to analog modulate the laser drive power.   First you have the fact that each pixel in the laser beam scanning process must be analog modulated at very high speed and high speed analog modulation wastes power.

Additionally, most people are not aware that the laser beam also has to be modulated due to the varying speed of the laser sweep.   If you think about it the laser beam horizontal sweep has to accelerate from zero to the maximum speed at the center of the screen and then decelerate to stop at the far side before returning.  To make a solid image appear uniform, the laser drive has to be constantly varying (for a “solid white” image the drive approximates a sine wave).  See such as the Microvision White Paper (a figure from which is copied below) and the excerpt (copied below) from the Microvision patent application”Apparatus and Method for Interpolating the Intensities of Scanned Pixels“:

From US Patent Application 20090213040

Q7. What is the power to run the PCB and the light engine on a Syndiant’s Displays? (SVGA and WVGA).

That really is a complex and involved question and depends on a lot of factors including the optical engine design and the target brightness.  I am also assuming that this is with LED illumination.   With LEDs the lumens per Watt of power tends to go down as the projector gets brighter, that is one of the advantages with lasers, namely that efficiency does not go down with power.

The LCOS display and ASIC for the WVGA or SVGA will usually consume less than ess than 0.4W.   Due to a number of design improvements, Syndiant’s 720p panel and ASIC consume less power while have a higher color field rate and better light throughput than the older WVGA and SVGA devices while having about 2X to 3X the pixels.

In the low lumen area of 10 to 15 lumens with a small, 0.21” WVGA or SVGA panel optical companies were able to get about 7 to 10 lumens per LED Watt.    With some power conversion overhead and including the panel and ASIC this mean that you could get with LEDs about 12 to 15 lumens for 2W of power.  While this is still not good enough for the very high volume cell phone applications, it compares very favorably to the ShowWX which takes 4+ Watts for about 15 lumens.

Q8. Which VGA display panel is best suited for the cell phone market?

I don’t know that there is a “best.”  Right now about the only reasonably high volume embedded panel is the color filter LCOS one by Himax that is used in cell phones for the India and China market.   The performance of these engines is too poor to be used in “first world” markets.   I think many of them are also less than VGA resolution.   They are typically about 5 to 10 lumens with pretty poor color and contrast and use very cheap but relatively large optics.

Personally, I don’t see a big “first world” need for a VGA or WVGA display.   Why bother projecting an image that lower in resolution than the cell phone’s display?   I think the big market will be to projector resolutions that are at least 720p

Q9. Does Syndiant plan on building the Light Engine?

I can’t comment on Syndiant’s future plans, but Syndiant’s business model has been to be a panel supplier.    There are very large number of good optical engine companies in the world so I don’t know why Syndiant would want to change.

Q10. Is Syndiant depending on someone else to make the Light Engine and Syndiant only sell the display panel?

Syndiant makes the panel and for use by many companies.   This allows different companies to make different products aimed at different markets.

Q11. Does Syndiant’s displays need a Vibrating Despeckle unit with DGLs?

It depends on the DGLs.  With the multimode DGLs you can drive them in such a way as to induce more mode-hopping to reduce speckle.   I would expect the there will not be despeckling required with volume production DGLs.

Q12. Does the light coming off the Vibrating Despeckle unit need to cover the homoginizer [a reference to the 3 year old SSTDC optical engine that used a vibrating despeckler]?

In the old SSTDC design with a vibrating despeckler, the light was partly spread before going to the despeckling mirror but not as large as the homoginizer.

 

Laser with LCOS is Focus Free — Yes Really!

Focus Free LCOS+Laser Projection (click for larger image)

Yes, when LCOS panels are used with lasers they can be “Focus Free.”   I have found that even very technical people have a hard time believing this as it goes against one’s everyday experience dealing with “normal” light and lenses.    People assume that the main function of a lens is to “focus light.”  After all, people are used to having to focus a camera lens or with a projector using lamps or LED light.

The optical physics of why it is focus free would take a long technical discussion, but it has to do with the laser light being effectively infinite f-number.  It is analogous to stopping a camera down to a high f-number where the depth of focus become very large.

Hopefully, “seeing is believing.”  I have uploaded a couple of still pictures (click on images for larger versions) and a short YouTube video demonstrating the focus free nature of the a Laseno Projector (sold in the U.S. as the AAXA L2).  This projector used a SYL2010 SVGA (800×600) LCOS plane with a 5.4 micron pixel pitch and 0.21″ diagonal.

For the top picture in this article, I projected the image the ceiling and some crown molding in my house.  This ceiling has lots of angle and different depths to it and with the crown molding in the way there is some obvious depth differences. Of course with the Laseno/AAXA L2 projector, there is no focusing necessary.

Projected at and angle to demonstrate focus free

Projected at and angle to demonstrate focus free (click on image)

For the picture on the left, I projected the image at a skewed angle from the side to cause a range of depths to be displayed.  The problem you have is that while the projected image is focus free, when the laser light hits the screen it looses it high f-number characteristics and thus the camera needs to focus.   By projecting the image on a flat piece of paper and shooting the picture straight onto the piece of paper I was able to focus the camera while demonstrating the focus free nature of the projector.

But perhaps the best way to demonstrate the focus free nature of a laser/LCOS projector is with a video.  I shot a short ~1 minute video where I mounted the projector on a little dolly and pulled it back away from the screen.  There was some shaking as I moved the projector so I stopped occasionally as I moved it it back so you could see it was still in focus.   I zoomed with the video camera in so you could see the detail in the video image.   Note that the camera’s exposures was locked/fixed on the starting frame, so as the image gets larger, it becomes darker by the ratio of the area so as the projector pull back the video gets a little dark.

I would recommend watching the video at 720p and in full screen to see how the focus is maintained.

Focus Free Video Demonstration

Other Information on the Images

The ~2 year old Laseno projector I used for these pictures has a fixed focus lens.   The image become well focused about 8″ from the projector to infinity.

The Laseno projection lens is not of high quality and you will see some serious chroma aberrations in picture as well as some spots having some blur due to the quality of the lens.  Additionally the projector has “100% offset” meaning that it projects through only the top half of the projection lens so that the projector will project upward from a flat surface without having a keystone effect.  Because of the offset projection, the image is best at the bottom of the image (which is from the center of the lens) at the chroma aberrations (color separation) become progressively worst toward the time.

You definitely will see laser speckle in the images.  The despeckle design was low cost and done over 3 years ago and it uses frequency doubled green lasers which inherently have a high amount of speckle.  Most people who have seen the AAXA L1/L2 “live and compared it to the ShowWX have said that the speckle with the Laseno/AAXA L1/L2  is less than that of Microvision’s ShowWX.

Direct Diode Green Lasers (Part 2, Chromaticity)

In my last post on Direct Green Lasers (DGL) I wrote about electrical power to lumens conversion.  In this post, I am going to talk about the color range/space and how it is affected by the green wavelength used.   The color chart above is a standard CIE chromaticity chart, often referred to as a “horseshoe plot” due to its shape,  that plots all the possible colors in terms of an “x” and “y” chromaticity coordinate.  The color wavelengths in nanometers (nm) are labeled on the outside of the horseshoe.

First of all, I am not going to give a deep scientific definition to color space, but rather try and give the reader some practical information to help in understanding the significance of the wavelength spec for green lasers.  I apologize in advance to the serious color scientists as I am probably going to butcher some terms.

Humans are not very good at absolute color measurement as the human visual system is adaptive and relativistic.  A wide range of wavelengths of light will look “green,” and this is particularly if you don’t see them side by side.

Laser light has very narrow bandwidth which puts it on the edge of the CIE horseshoe so to speak.  It turn out that diode LED’s  while as pure as lasers are still comparatively very saturated and would plot very near the edge of the horseshoe as well.   A big exception to this would be so called “white LEDs” (and some other colors) that are actually made with blue LEDs stimulating phosphors).

Usually 3 primary colors with wavelengths that are considered, red, green, and blue are mixed to form any of the other possible colors (some systems use more than 3 color primaries).   The RGB phosphors used in old CRTs were not pure color wavelengths and so these “primaries” where inside the horseshoe rather than on the edge like lasers. The TV standards for broadcasting grew up with these limitations set how what color could be represented.  If you plot the 3 primaries used for standard definition television you the SDTV triangle.   Also ploted is the newer HDTV standard which defined a slightly larger color space triangle.

For more on the color space concept I would suggest reading the on-line article by Matthew S. Brennesholtz on expanded color gamuts and the Wikipedia article on CIE 1931.

The the lasers, I have also plotted the color spaces (triangles) assuming a 640nm red and a 460nm blue and then a triangle for each of 510nm, 525nm, or 532nm for the green.    For a given set of RGB wavelengths only colors “inside the triangle” can be represented.  Also if you follow an edge of the triangle it shows what color can be reproduced in between two of the colors assuming the 3rd color is off when mixing the the other two primary colors.

One thing immediately obvious is that the laser primaries are way outside the color gamut/triangles for SDTV and HDTV.  While this means a wider range of color could be represented, it also poses a problem when using existing standard video and still image standards.  For example if you have bright green grass in a video, the video signal will call for nearly 100% green, but if you use a 532nm green laser at 100%, the grass will look like it is glowing green rather than green grass.   So if you want the grass to look right, you actually have to desaturate the green by adding red and blue to it to get to a point on or inside the HDTV/SDTV triangle if you want the image to look like it is indended.

If you have a “wide color gamut display” using lasers or LEDs then you need content that matches your gamut to take advantage of it.  If you use the commonly available video and photos formats which were coded/compressed for small color gamuts you can’t take advantage of the full color gamut if you want the images to look like they were intended (and not an over-saturated glowing look)

Consider particularly the triangle made by the 510nm green lasers and notice how it cuts off the bright yellows and yellow-greens of the SDTV and HDTV color spaces.  There is no way to mix 510nm “green” with 640nm “red” to give a good yellow.  You have to have at least a 520nm green to fully represent the yellow within the standards.    This a major reason why there is the push to have direct green laser wavelengths of at least 520nm or longer.

You may notice that any of the greens from 520nm to 545nm (much more than 545nm and it starts cutting off some of the blue-green areas) will give a larger color space than HDTV.    But if you go back and look at the photopic response curve from part one (copied below) you will see that as the wavelength goes from 510nm to 555nm, the lumens per Watt improves.  For example, if the wall plug efficiency (WPE) was the same you would get nearly double the lumens per Watt at 532nm that you would get at 510nm.  Since 532nm is the common wavelength targeted by frequency double green lasers I tend to “derate” the WPE of shorter wavelength green lasers by their difference in lumens per Watt.   So a 525nm greens efficiency would be multiplied by 542/603=90% to get its effective WPE compared to a 532nm green laser.

One more thing on the CIE chart at the top, you will the “black body curve” in the middle of the chart numbers on it like 6500 or 10,000; these are the so called “color temperatures” of a black body is heated to the given temperature (in Kelvin).    A 6500 “white” is a little on the red side (also known as “warmer”) where a 10,000 “white” is a little slightly blue (also known as colder) which to the human looks “whiter than white” (and why some detergents put “bluing agents” in them).    “D65” is a common standard “white” that is very close to 6500 but slightly off the black body curve.   In the industry it is known that most westerners tend to prefer warmer colors toward D65/6500, whereas people living in Asia seem to prefer the cooler colors such as D93/9300 or even 13,000 Kelvin where the “white” has a clearly blue tint to it (I haven’t seen a study as to why).

It turns out that the target color temperature and the wavelengths of the red, green and blue will set how much of each color in Watts you will want.   If for example the color temperature is set for 6500, it requires will need somewhat more red but if you want 10,000, it requires somewhat more blue and green.

“Soothsayer” Part 3 – Where Does the LBS Power Go?

In my last blog I wrote about the power measurements on the ShowWX and a number of people asking “where did the all the ShowWX’s power go?”

Microvision wants you to think that they just point the lasers directly at their mirror and with next to no power loss the laser light is steered onto the screen, but the truth is anything but this.  It turns out that there is considerable electronics consuming power to control the mirror and lasers and are significant light loosing optics required to make it work.    In this blog, I we will take a peek behind the Microvision curtain.

First, Microvision has not published specifications on the power consumption of their mirror or other chips in their system.   Second, I did opened a ShowWX to take a peek inside (see above), but I didn’t rip it apart to measure the current for each of the components.   It was clear with 5W of power consumption and the very poor image (more on that in the next installment) that it wasn’t going to be a serious competitor to Syndiant, so there was no point in our spending the time and effort to do a detailed power evaluation.   Even with these caveats, it is possible to get a reasonable understanding of the power consumption issues associated with laser beam scanning with the available information.

So per the above my number are not going to be “perfect” but I do believe them to be reasonable estimates.   Microvision could clear this all up by publishing their actual numbers instead of their usual hand waving like “making a 40% improvement” without saying what part of the total power was improved by 40% and what was the starting point.   I would welcome Microvision’s corrections with their actual numbers.    Personally, I think it is the case that Microvision feels “it is better to remain silent and be thought a fool, than to open your mouth and remove all doubt.”

Above is figure 28 from patent application 20110234919  by Microvision.   This block diagram outlines the major electronic components that would be required in a ShowWX (or ShowWX plus).  As seen from the picture of the opened projector and in Fig. 28 below, there are a lot of components each of which is consuming power.   Fig. 28 also gives some idea as to the complexity in driving a LBS.    And the picture of the inside of the ShowWX demonstrates that all this takes up a lot of space (note there is a two PC board “sandwich” with all the circuitry inside the ShowWX).

Some people have made the point that the ShowWX is a standalone projector and that the power would go down a lot if it was embedded.    In reality, there is not much from Fig. 28 that would go away.   The “media module” in the ShowWX is only an analog RGB to digital converter and for WVGA resolution this should consume about 0.2 Watts.  The battery and some of the power management might be reduced which might save another 0.2W to 0.5W.  There might be a few other things but most of the rest of Fig. 28 would have to be there for an embedded LBS projector.  So maybe out of the 5.5 Watts the ShowWX consumes, at the very most 1W might not be needed with embedding.  That still leaves around 4.5W if this was to be embedded which is way too high for any realistic volume cell phone application.

Let’s start with the beam scanning mirror in the lower right of Fig. 28.   To make the mirror scan the laser beam even roughly correctly requires actively driving mirror.   The shorter the throw angle or the higher the resolution, the more the power goes up.  Based off a published paper by Microvision from a few years back and datasheets from other makers of 1-D beam scanning mirrors, the power consumption of the Microvision mirror is about 0.3W to 0.5W (not exactly nothing).  There are “free oscillating” mirrors that consume much less power but these don’t produce a good scan for making a projector.

Next in Fig. 28 there is the DSP and MEMs ASIC.  The problem is that the mirror naturally wants to oscillate in a squiggly sinusoidal Lissajous pattern (see for example Microvision patent application 20090213040 ) which isn’t very good for generating video image.  To somewhat straighten out the Lissajous pattern (it still is not nice straight lines — more on that next time) takes power going to the mirror and power to constantly be calculating and correcting the scanning process.   The correction of the scanning process with the DSP and/or ASIC plus losses in the drive circuitry is probably taking about 0.5W.    So with the mirror itself and the drive circuitry and control of the mirror alone there is about 0.75W 1W being used.

The next big block in Fig. 28 is the “Video Control Module” (VCM) which is where most of the power is going.  Note that the HSYNC, VSYNC, and STATUS signals go from the MEMs Control Module to the VCM.   The reason is that the incoming image has to be stored and processed and distorted to match the scan process of the MEMs mirror.   Even with the active drive, the MEMs mirror does not move the laser beam in nice straight lines at a uniform speed.   In fact it moves in curves at a non-uniform speed and the VCM’s job is to re-shape/transform the image so that after it goes through the MEMs scanning it looks similar to the original image.

The VCM takes the digitized RGB data and stores it in the SDRAM.  I then processes/scales/transforms the image base on the distortion of the MEMs scanning process.  It then feeds the reprocessed image to the laser drivers.  All the read and writing to the DRAM and the processing by the ASIC/FPGA takes power, probably on the order of another 0.5W.

Next comes the power taken in driving the lasers.  To make a LBS system work, the laser beam has to be modulated (intensity changed) at high speeds which consumes significant power.   The lasers drivers are either analog (which consumes power) or have to be very high speed switching digital (which also consumes power) to give the various intensity levels for an image.  Even when displaying “black” this circuitry has to be “idling” to be ready to turn on in a few nanoseconds and is consuming power.   Likely 30% to 50% of the power going to the laser is being consumed in the laser drivers.

[Update 2011-12-22: The optics below show a polarization based combiner from the Microvision application.  My understanding is that Microvision currently is using dichroic mirrors instead of beam splitters for parts 610 and 612 and a total internal reflectance prism in place of beam splitter 614 to first reflect the light into the mirror and then let it pass out of the projector.  The light throughput for the dichroic mirror based combiner optics including the MEMs mirror is suppose to be about 60% which is the same number I used in the laser power calculations]

Now let’s get to the optics.  I have show below Figures 20 which is a simplified diagram and Figure 6 showing an optical module from the patent application.  To hear Microvision talk about it, you would think that only DLP and LCOS require optics and have losses from the optics.

The lasers 204, 206, and 208 have to have their beam shaped by lenses.  602, 604 and 606 each of which is probably losing about 1% of the light.   Then note that in order to combine them in a single beam, they have to go through mirror 608 and beam splitters 610, and 612.  There is roughly a 5% light loss in the mirror 5% to 10% in going through each beam splitter (note some lasers go through more than one beam splitter in the combiner).   Then you have the beam splitter 614 with another 5% to 10% loss, the quarter wave plate 2002 and another 2 to 4% loss that directs the laser light the MEMs mirror 616 which has about a 15% reflectivity loss, then back through the beam splitter with another 5% to 10% loss.   Taking all the optical losses together and only about 50% to 65% of the light from the lasers is going to make it out.

Finally, we have the losses from converting electrical energy to light energy in the lasers.   The frequency doubled lasers were reportedly getting about 6% WPE.    There is a lot of complicated math involving the wavelengths of the light the efficiency of the lasers for which I will use a spreadsheet to calculate the result assuming the lasers used by Microvision and about a 60% optical throughput from the optics.   The lasers themselves are taking on the order of 0.7 Watts.   remember that this number has to multiplied by about 1.3 to 1.5 to include the drivers for the lasers.  So the lasers and drivers alone are consuming about 0.9W to 1W.

Add it all up, subtract off the little bit from the batter circuit and the video-in chip and there is about 4 to 5 Watts being used by the LBS including its electronics.  Microvision can hand wave about saving 40% here and 20% there, but the problem is they have to save about 80% everywhere to get their power down to their “goal” of 1W.

Appendix:

Below is a figure taken from “Scanned Laser Pico projectors: Seeing the Big Picture (with a Small Device)” that shows a more simplified diagram than the one in Fig. 28 above.

Below is a top view of the inside of the ShowWX.

A typical Analog Devices analog RGB to Digital RGB converter AD9883A and it will take about 0.2W for WVGA resolution.

http://www.analog.com/static/imported-files/data_sheets/AD9883A.pdf

For anyone interested, I have added a picture showing the hottest point on the case.  It was roughly just above the large ASIC/FPGA in the picture above: