Archive for May 15, 2012

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 (

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 7: Microvision’s Obfuscations Causing a Buzzing Sound

Microvision continues to make thinly veiled accusations against this blog in their May 9th, 2012 Company Displayground Blog (quoting directly with my bold emphasis added):

Our shareholders are following the topic of direct green lasers with avid interest and we get a lot of questions from them on price and availability. They have ridden the green laser wave with MicroVision and are understandably anxious for their investment and patience to pay off. There is another group of MicroVision watchers that take an active interest in direct green lasers and for that matter, all things MicroVision and have quite a bit to say. We welcome such interest as we are really proud of what our patented solution can do and the advancements we have made with the PicoP Gen2 display technology. But it does get tiring to have an open mic of misinformation from parties who only seem to have an interest in not seeing Microvision succeed. We try and ignore this contingent just like the best thing to do when a fly is buzzing around your head is to ignore it. Eventually the fly finds something or someone else to buzz around and the problem resolves itself.

Like most things Microvision writes they raise more questions than they answer.  For example, who is this “group” of watchers that “ have quite a bit to say” about green lasers?  As far as I know, this is the only blog regularly writing about green lasers for small projectors.   I guess they feel like I have them surrounded :-).   I would suggest that the real reason they cannot ignore the “buzzing sound” is that is goes contrary to Microvision’s attempts at obfuscation and eventually their investors and analysts ask questions.

I take the most interest went key specs are missing or when states what is at best a half-truth.  From what I read, Microvision obfuscates, uses straw-men, half-truths,  give meaningless ratios of improvements, and state goals/expectations as if they have been met.  They could put this all to rest if they could be specific about what they consider “misinformation” and give direct clear answers.  

$200 Green Laser Clarification:

Microvision’s blog when on to clarify(?) what Microvision’s Lance Even’s was saying green lasers costing nearly $200 that I address in my April 30th blog.  Quoting directly from the Microvision Blog:

The price of direct green lasers is understandably a topic of speculation since the manufacturers of the diodes have not publicly discussed pricing or even the exact timing of commercial availability. We cannot reveal specifics around these issues, but we can and have stated that we expect the prices of direct green lasers to be significantly less than synthetic green lasers which have cost nearly $200.

Microvision, apparently in response to my blog on the “nearly $200” price of DGL clarified that Mr. Evan’s $200 remark was in reference to the synthetic green lasers.   But note it is only an “expectation” (as in some time in the future) that the prices will be lower.

It is also interesting that Microvision is admitting publicly that the lasers were costing them nearly $200 (or maybe more at some point).  You have to wonder why they went to market with the ShowWX using a $200 laser for projector with only 10 to 15 lumens.  Can you imagine what investor reaction would have been back in 2009, 2010, or 2011 if they knew that Microvision was selling a supposedly high volume consumer product with a $200 laser in it?   My speculation is that unless they agreed to pay $200 for the lasers and buy a lot of them, that they would have had no way to build any product and if they couldn’t show (some pun intended) and that would make it impossible to raise money.   To keep investors on the hook, so to speak, they had to use obfuscation about the cost of lasers (some things never seem to change).  The losses on the ShowWx were essentially marketing expenses to raise money from the “shareholders” that were following the company back then.

They seem to have made the calculation that they needed to loose many millions of dollars on the ShowWx product line in order to keep the investor money flowing in.  Now that they consider those losses in the rear view mirror, they are admitting to them.   I wonder when they will come clean on the cost and specs of today’s direct green lasers.

More Half-Truths from Microvision

One more interesting set of half truths from Microvision’s blog:

We are confident that the manufacturers of the direct green lasers will be able to meet the volume requirements as the market demand for direct green lasers grows, and we expect price to fall accordingly.”

The first half-truth is that “manufacturers of the direct green lasers will be able to meet the volume requirements.”  Yes, this is true today, but only because the volumes will be very low.   Among the reasons is that the price of the lasers will be very high and that they are not currently designed into any high volume products.   Secondly, by laws of supply and demand, if the lasers are expensive few will be bought and thus they will meet the volume requirements.  Thirdly, the growth in the market could be very slow so it would be easy to meet what Microvision “expects.”    In short, Microvision like a politician, used a lot of words to give no real information.

What Microvision won’t admit, I suspect because that would be bad for raising money, is that the direct green laser has so far proven difficult to make due to the physics involved.    Certainly very smart and capable people are working on DGL, but they are not ready in the near future for the high volume consumer products.

Augmented Reality and Google Project Glass Part 2

Google Glasses

Since my last post on Augmented Reality (AR) and near eye (head mount) display Google put out some publicity on their Project Glass concept.   Google made it abundantly clear that this was only for the purposes of concept testing and not a real product, but they also said that there would likely be some test products at the end of 2012.

Jason, “The Frugal Dad” wrote saying he had seen my first article on AR and that he has a new “Infographic” that includes Google Glasses as a Future “disruptive technology.”   Unfortunately most predictions about the future turn out to be wrong and nothing I have seen so far in the way of near eye AR, including Google Glasses, I believe will meet the consumer expectations and become pervasive.  I’m not saying it won’t ever happen, but rather there are still many major problems to be solved.

As I wrote before, I think there are many practical issues with near eye displays and augmented reality.   The Google Video “Project Glass: One day…” was obviously a “concept video” and all the images in the display were “fake” as in not what the actual display will look like.

Along these lines, the April 5, 2012 Wired had an article called “Google Glasses Face Serious Hurdles, Augmented-Reality Experts Say” which raises concerns that Google is over-touting the concept.  The Wired article quotes Pranav Mistry, from the MIT Media Lab  and and one of the inventors of the SixthSense wearable computing system, “The small screen seen in the photos cannot give the experience the video is showing.”  Also in the Wired article, Blair MacIntyre, director of the Augmented Environments Lab at Georgia Tech raised concerns that Google is raising expectations too much.   Both Dr. Mistry and Dr. MacIntyre are certainly proponents of AR.  Their concerns, and mine as well, are that that raising expectation too high could backfire on the AR concept in long run.

Dr. Thrun on Charlie Rose Looking Up

Sebastian Thrun, Google Fellow and Stanford professor, was on Charlie Rose on April 25, 2012 wearing a working Google Glasses prototype.   The first 4 and a half minutes of the Charlie Rose video discuss Google Glasses and gives some insight into the issues, not the least of which is whether people are really going to wear something like this.

To see the images in the “glasses” he has to look up, where the Google Concept video suggest the images are right in front of you all the time.  So he can’t see the person he is talking to and the computer image at the same time.   Imagine talking to somebody wearing these when they are clearly looking up while talking to you (particularly notice Dr. Thrun’s eyes in the picture above at 1:11 into the Charles Rose Video).   By instinct, humans are very sensitive to eye behavior, and someone constantly looking away (up) is a distracting behavior.  Now imagine you are walking down the street and searching for something on your glasses and a truck comes by — big oops.

The most insightful comment by Dr. Thrun was “we having yet found this [augmented reality] to be the compelling use case” but he didn’t elaborate as to why.   But this does indicate that Google is still be trying to figure out if AR is really compelling.    Dr. Thrun did say that “the compelling use case is the sharing experience” and commented on sharing pictures at being something they enjoyed — I guess this is Tweeting on steroids where all your friends can see what you are doing as you do it.  In this case the glasses become a hands free video camera.

The Google video has inspired some funny spoofs of it that in their own way make some of the points above:

ADmented Realility — Google Glasses Parody extrapolates on the what could happen with advertising gone wild.

Google Glasses: A New Way to Hurt Yourself and a video shown on Jimmy Kimmel Live demonstrate the dangers of “distractive walking”

The next time on the subject of AR, I plan to talk about more of the technical issues with AR.