Archive for December 27, 2011

Looking Ahead To CES and Future Articles

Thanks to the readership of this blog, I now have my “press credentials” for CES. If there is something in the Pico Projector field in particular or displays in general you hear of at CES you would like to see me try and cover, drop a line to info@kguttag.com.

I also want to let you know what I am working on and give you, the readers, a chance to help guide what I write about.

On the week before CES, I plan on putting out my “Cynics Guide to CES Demos.”   I plan it to be a bit tong-in-cheek as the tile would suggest, but hope it will also be informative.   For example, “The worse the image quality of the display, the less cloths they put on the female model in the picture they show.”

LCOS+Laser Focus Free Demo

I’m working on a technical piece explaining why laser illuminated panel (LCOS and DLP) projectors are focus free with lasers.   It seems to go against what even highly technical people believe from dealing with non-laser light with cameras and projectors that need focusing.

DLP Diamond Pixel Effects

Have you noticed that the newer WVGA (848×480) and SXGA (1280×800) DLP® projector’s pixels look funny?  All the pixels are turned at 45 degrees in what TI call’s “Diamond Pixels.”   This was done to try and make the DLP light engines thinner (it will take a while and some pictures to explain why) but it hurts the resolution and causes some strange artifacts (I will show what happens in some pictures).

Laser Beam Scanning Image Issues

 I know there has been a lot on Laser Beam Scanning (LBS) on the blog as of late.  It was a “hot topic” with Microvision’s “false soothsayer” comment coming out.   I do have a lot more information the many problems with LBS that they don’t want you to know.  The next subject about be on the resolution and flicker problems associated with LBS.

I plan and have an article on why lasers are the key to high volume embedded pico projectors and to continue the “use model” series.

I’m also planning on a series of article discussing the efficiency and size issues with the various pico projector technologies including LCOS, DLP and Lasers but this is going to take some time to write.

If you want to give feedback, ask for one of the above to come out sooner, and/or ask for particular topics, please either comment below or email info@kguttag.com.

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:

“False Soothsayer?” Part 2

ShowWX consumed 5.6 Watts

Microvision in their blog and their recent 8-K statement wrote Lest you be led astray by false soothsayers.”    I would agree not to be led by “false soothsaying”   but I think that it is Microvision that is trying to lead people astray.    I very much believe in the future of direct green lasers but the problem is that the reality does not fit with what Microvision appears to want people to believe.

In my previous post, Microvision’s “Soothsayer(?)” for their “Number One Question”, I outlined where Microvision’s blog response (to me I have every reason to believe) missed the mark on answering the key questions related to direct green lasers.   In my opinion, they gave non-answers and half-truths.

This certainly is not the first time Microvision has engaged in “false soothsaying.”  For this blog entry, I want to deal with Microvision’s comments and predictions on power consumption through the years.  Something for which there is a track record of Microvision predictions and then the measured results.

Since at least as far back as 2007, Microvision’s Alex Tokman has been saying that their “goal” is 1.5 Watts dropping to 1 Watts for their total power.   I have copied below a number of references quoting Mr. Tokman in 2007 and 2008 prior to the introduction of the ShowWX.

I have also personally measured (pictured above) the ShowWX that Microvision actually delivered in March of 2010.  It consumed not 1, not 2, not 3 or even 4, but rather it consumed a wopping 5.6 Watts and I measured only about 10.5 lumens of light output for about 2 lumens per Watt.  This was by far the worst efficiency than any of the “LED” pico projectors I had measure using DLP or LCOS that I have measured.  So much for Microvision’s claim that laser beam scanning is the most efficient.

I measured both the power consumption for white (top picture) and it came out to 5V times 1.12A or 5.6 Watts for 10.5 lumens.   Microvision claimed a big advantage for laser beam steering is how they save power when displaying black so I measure a full black image (lower picture) and it came to 5V times 0.7A or 3.5 Watts so that even when putting out a black image it consumed more power than the LED projectors did putting out well over 10 lumens.

Below are some of the Microvision quotes (and my comments) on power consumption I found in a quick web search.  They show I think a consistent attempt to create an impression that their power consumption was much better than it actually was and was going to be:

As good a reference as any on to Microvision’s “sooth saying” on power was an article in the “The Economist”  from Mar 6th 2008:

http://www.economist.com/node/10789401

Mr Tokman says the big mobile-phone manufacturers have set an upper limit on the power consumption of a projector of 1.5 watts. Given a typical phone battery, this would allow a projector to operate for about 2.5 hours, long enough to watch a film. Microvision’s prototype consumes about three [3] watts at the moment, but Mr Tokman expects this figure to fall as the internal circuitry is concentrated within a smaller number of dedicated chips.”

So Mr. Tokman said in March 2008 that they were already at about 3 Watts in March 2008 and yet about 2 years later when the ShowWX started actually selling, they appear to have gone backwards because the ShowWX that they sold consumed over 5 Watts.   Was this a severe rounding error?    Or maybe he didn’t count everything that consumed power in the projector.   It looks to me that they couldn’t predict the present, no less the future.

I also find that Microvision particularly in their conference calls often talks in what seem to be almost riddles.  On direct green lasers they talk about them being less than SGL throwing around almost random “X’s” and “Y’s” and percentages but never give any real idea as to whether they will be cost effective, and  just as importantly, when they will be lower in cost (in semiconductors, you have to know the price, volume, and date to have anything meaningful).

Let’s look at some of the similar riddles they gave on power in their “Microvision, Inc. Q2 2008 Earnings Call” on August 5, 2008:

http://seekingalpha.com/article/93563-microvision-inc-q2-2008-earnings-call-transcript

Alexander Tokman, “First, let me talk about power consumption. The power consumption of the latest version of the MEMS scanner has been reduced by approximately 75% over the previous version initially shown about a year ago. What is the significance of this reduction? Let me give you the big picture. The cell phone manufacturers told us that the target spec for the overall power consumption for the embedded Pico Projector which includes MEMS scanner, light sources, ASIC optics and other components should not exceed 1 ½ watt.

And more numbers riddles in their Q1 2008 Microvision, Inc. Earnings Conference Call – 24-APR-08

http://goliath.ecnext.com/coms2/gi_0199-7829068/Q1-2008-Microvision-Inc-Earnings.html

“ALEXANDER TOKMAN: Again, excellent question. Let’s start with the application requirement. What the application requirement calls for, based on the direct user feedback and the OEM feedback we have solicited to date is that accessory device must function on its own for 2.5 hours without recharging. And 2.5 hours obviously comes from watching a long movie. That’s what our target is. The SHOW prototype that we demonstrated could function without recharging for 1.5 hours. So we are reducing the ultimate power of this device by 40%. I think we were talking about five more during CES so if you subtract 40% it will get you somewhere around sub three watts. On the accessory. Obviously, embedded targets are much more aggressive than this.”

I guess all those percentages made it sound real and important.  And in the second quote again that they had 3 Watts in 2008 and yet the product they actually sold nearly two years later consumed over 5 Watts.

From Q3 2007 Microvision, Inc. Earnings Conference Call –  01-NOV-07:

http://goliath.ecnext.com/coms2/gi_0199-9753613/Q3-2007-Microvision-Inc-Earnings.html

Alexander Tokman – “Recall that we said we want to target [access] rate for 2.5 hour continuous operation without recharging, and we targeted the embedded module for the first generation to be 1.5 watts, which is what cell phone manufacturers have expressed to us for all of us to be successful.”

Finally the earliest reference to their LBS consuming 1 to 1.5 Watts I found was back in 2007 in Microvision’s Blogspot 2007-05:

http://microvision.blogspot.com/2007/05/cc-notes-tokman-comments-on-embedded.html 

Alex Tokman: “we are targeting an engine that will draw 1.5 watts of power, going down to 1 watt. So we feel we’re on the threshold of getting inside the cell phone. Although other people are claiming that they’re capable of doing this, we feel good about our position for this specific application.”

So 3 and a half years later, how is Microvision’s sooth saying?

 

Microvision’s “Soothsayer(?)” for their “Number One Question”

My, the power of the blogosphere!  I just started this blog two weeks ago and Microvision has all the appearances of making a veiled response to my blog and having to issue an 8-K statement to the SEC.  Personally, I found Microvision blog/8-K full of half truths and obfuscations.  It also appears that since they couldn’t deal factually with what I wrote, they resorted to name calling with the pejorative “false soothsayer.”

Since my blog has led to a lot of questions and a firestorm of activity on the Yahoo Financial Message Boards (and the deletion of many of these posts) and the Investor’s Village Board on Microvision last week, and as far as I am aware I am the only person writing about the availability of green lasers in 2012 recently, I think it is pretty clear that the “soothsayer” they are referring to Microvision’s blog is me (if not me then who else?).

For those who haven’t seen the Form 8-K it can be found at:

http://biz.yahoo.com/e/111219/mvis8-k.html

Anything quoted below I will take directly from the 8-K statement.   For brevity, I did take snippets out but I will try snip enough to keep it in context.

First to the “soothsayers”:

“Lest you be led astray by false soothsayers, based on our periodic discussions and latest updates from three direct green laser developers we anticipate that Nichia, Osram and Soraa will release commercial versions of their lasers in 2012 and two of the three should have commercial direct green laser released by mid-2012.”

So who, other than me, are they accusing of being a “false soothsayer?”  How about being specific about what they think I (or someone else if there really is someone else they are speaking about) wrote that is false?    I would be happy to answer their accusations.

Their “number one question” is “.  .  . the topic we overwhelmingly receive the most questions about – direct green lasers (DGLs). Everyone wants us to tell them when they will be available!”   

This certainly is a key question for them, but really hides behind it a bunch of other issues.     I would suggest that they should also be asked about the price, efficiency, and wavelength of these lasers and whether they are expected to be suitable for making a practical embedded cell phone pico projector engine in 2012.

“ . . . So what do I mean by “commercial version” direct green laser?  It’s a laser that has passed through intense qualification by the component manufacturer to insure that it meets all of its intended performance specifications, with confirmed reliability and manufacturability necessary for mass production.”

The real question is whether these lasers will be available at a price point, with a wavelength, and an efficiency that is practical.   I don’t doubt that most if not all the companies will be in production with a green laser in 2012, but what constitutes “mass production” is a different matter.   Nichia already has a 510nm green laser in production, for example, and it might be possible to build a heads up display for an automobile with it (albeit a bit expensive for the purpose), but that is clearly impractical in terms of wavelength, efficiency, and cost for building a high volume battery powered projector.   I also question whether they will be bright enough for a volume product other than a HUD.

Also give a ball park as to what they mean by “mass production.”

“� DGLs will be much cheaper than synthetic green lasers at introduction.”

I would consider this to be obfuscating.   While they will be cheaper, the real question is whether they will be cheap enough and for what products?  Also are the lasers efficient enough, have the right green wavelength, and bright enough to make a practical projector?

“� Ultimately, pricing depends on volume and yield hence we will not know the final pricing next year. However, the two important points to focus on are: DGL are much easier to manufacture than their “synthetic” predecessors and the budgetary quotes we see today reflect cost that is substantially less than the cost of the synthetic green lasers we purchased from 2010-2011.”

More obfuscating about whether they will be cost effective, at least in 2012.   But it sound like a roundabout way of saying that the price could be about anything next year as at least some of the variables like yield are out of their control.    Note, the cost could be a lot less than what they paid for SGL and still way too expensive for a practical product.

“� DGLs will be available in higher quantities than SGLs.

� Based on our discussions with suppliers, we expect volumes to reach monthly run rates that far exceed historical production of SGL volumes. Direct green laser diodes will be manufactured similar to established manufacturing processes used for red and blue diodes today by some of the largest laser suppliers in the world. It’s an easy equation: Simpler = easier to manufacture = higher volumes and yields.

As my father said, “that is damning with faint praise.”  Since the SGL that they could use in laser beam scanning were only available in very limited quantities at high costs, this essentially says nothing.

“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!”

I hope they will because nothing they wrote in their blog/8-K told you anything but restating a few truisms that they have stated multiple times before.  They gave a answers to softball questions while telling you next to nothing about whether it would allow them to build a practical product.

I believe that even all the focus on green laser availability itself is a misdirection of sorts.  Beyond the cost, availability, efficiency, wavelength and other technical factors associated with direct green lasers, I believe the whole laser beam scanning concept has major other problems that are hiding behind the many years of scapegoating green lasers.

So what did one learn from their response that contradicts anything I  (or some other person) have written?   I couldn’t find anything.   Their statements are much like a politician that restates the problem and tries to pretend like this is the same as giving an answer.    I didn’t find anything Microvision wrote above to be factually wrong, it just doesn’t provide any real information other than restating the obvious and not telling the whole story.   Also nothing they wrote disagrees with anything, “the soothsayer” has written (mostly because it doesn’t really say much).

Pico Projector “Use Model” (Part 3 – Raison d’être)

For this installment on the pico projector “use mode” I would like to step back and talk about the original reason for pico projectors in the first place,  their Raison d’être if you will.  I will also discuss why drifted away from that use and how they should return.

Pico projectors original premise was built around producing an image larger than the physical dimensions of an ultra portable device such as a cell phone.  Implicit in this premise is that the device must be able to work within the power, size, and cost constraints imposed by a cell phone.    We simplified this to it having to be “battery powered and easily fit in a shirt pocket.”

So the Raison d’être for pico projectors was to give a bigger, and I would add, higher resolution image than is possible with a portable device such as a smart phone.

Surveying the market a few years ago, cell phone as a group had a similar set of requirements

  1. Cost less than $30 for the projector including electronics.
  2. 1 to at most 1.5 Watts of total power (display and any electronics)
  3. No more than 7mm tall and  about 4CC of space

Less well understood was the brightness and resolution for this new product concept so these were traded for the requirements the cell phone makers better understood.    Early on nobody could meet any of the requirements above.

To try and even get close to the cost, size, and power goals, TI’s DLP® pico devices went with very low resolutions of half VGA (480×320) and nHD (640×360).   With LCOS it was easier to make small low-power pixels, so we focused on WVGA (854×480) which was 6mm tall and SVGA (800×600) which was 7mm tall with both devices having a 0.21-inch diagonal displays.   LCOS’s challenge was that it works with polarized light and with LEDs causes 25% to 50% of the light to be lost.    BTW, laser beam scanning (LBS), was a non-factor as the cost of the required lasers alone would break the budget, not to mention the size of the electronics and a myriad of other problems.

Looming over DLP and LCOS when used with LEDs is an optical physical property call “etendue.”  (for a good paper on the subject of etendue with LEDs see OSRAM’s “Projection with LED Light Sources”).   Without getting into all the physics, LEDs produce light that spreads out such that the optical efficiency goes down dramatically as the microdisplay size decreases and/or the size of the LED increases.   One of the virtues of lasers used with microdisplays that they have near zero etendue and so there is no light loss due to etendue no matter how small the display.   An additional big benefit for LCOS is that lasers produce polarized light which eliminates the polarized light loss associated with LCOS using LEDs.

With the constraints imposed by LEDs and small size, the result was some “gimmick” products with low brightness and low resolution.    You could project a relatively low resolution image in a dark room.  It is impressive when you first see a big image coming from such a small product, but the big question became “how are you going to use this on a regular basis?”  Samsung and LG both made some exceeding low volume test the market cell with projectors in them.    Nikon has made a couple of cameras with pico projectors in them.  The biggest volume of embedded pico projectors has been some low resolution color filter LCOS projector embedded in cell phones sold mostly in India where they are use as cell phone based televisions.

For round 2 of the pico projector market, DLP and LCOS drifted away from the embedded market which wasn’t selling well and backed up (got larger) to support portable media player projectors.  The projectors required more brightness and to go brighter with LEDs meant requiring bigger microdisplays and bigger optics.   Syndiant kept the 800×600 resolution and simply made the pixels bigger.  DLP keep the pixels the same size and added more pixels to make a bigger displays, first 0.31-inch diagonal 848×480 (WVGA) and later a 1280×800 0.44-inch.    These products require larger batteries or wall plugs and more for carrying in separate bag than in your pocket.   Interestingly, DLP also rotated the mirrors 45 degrees to what they call a “diamond pixel” which causes some strange artifacts and a loss of effective resolution (the issues with diamond pixels will be discussed in a future article).

I don’t think anyone believes that these portable projectors as they stand today are anywhere close to the vision of embedding projectors with cell phones.  The microdisplay makers found that at least there was a class of sellable products that could be made by going larger to support more light output with LEDs.

To get back to the original vision for pico projectors and the opportunity for very large volumes of products with the embedding in pocket sized portable products, my conclusion is that affordable lasers, particularly green, are required.   Lasers will enable the microdisplays to be made small without a large loss of light and this in turn will lead to smaller and less expensive optics.  Since the lasers naturally produce polarized like, LCOS will gain the additional efficiency benefit.

If I “plug into the equation” affordable lasers, then I see how to meet the requirements first outlined by the cell phone makers.   Additionally, the properties of laser light enable very short throw so that a image the size of a piece of letter paper (about the size of an iPad) can be projected from only a few inches above a surface in what I call “down-shooting.”    With a built-in inexpensive camera aimed at the projection image to capture user input and you have a ipad/tablet that fits in your pocket.

The concept art at the top is one I generated when I first started working on pico projectors several years ago.  I knew they would not be very bright if they were going to work on batteries so down-shooting onto a piece of paper seemed like the way to go and I think it will be coming back to this use model as the technology progresses.

One last thing:  While one is building a virtual iPad/Tablet product, it better have at least the resolution of an iPad which today is 1024×768 pixels and will likely be going higher in the future.   One reason will be is that more resolution is more useful, the other is that history has shown that consumers want more pixels whether they need them or not.

Appendix

While there is talk about someday having OLED’s or LCD display that will roll up like a sheet of paper, it is believed that a practical display that can roll up is still many years in the future.   There are many serious technical problems including ruggedness/lifetime in having a near perfect air tight seal with something that is thin and flexible enough to roll (air will destroy OLED’s and LCDs) and the optical uniformity problems with something that is flexible.

There have been some “lab prototypes” which may work if carefully handled and with short lifetimes, but these are far from being ready for consumers.  So this opens the door to pico projectors that can be small, rugged and project onto things like a piece of paper.

Diode Green Lasers (Part 1, Wavelength and Efficiency)

Today’s blog is the first in a series about green lasers, and in particular about how wavelength, power, efficiency, and lumens relate to each other.  Also, I’m also going to write a little about the difference between and R&D announcement and what needs to be known to build a projector.

I believe that direct green lasers are the key to making very small embeddable pico projectors regardless of the display technology be it LCOS, DLP, or Laser Beam Scanning (LBS).   Unfortunately the “physics” of green lasers makes them hard to produce. Read more

Meet with Karl Guttag at CES 2012

Hopefully you have been enjoying the content of this blog which as been covering pico projector technology.  I promise there is much more to come, but today I want to do a little (consulting) business. Read more

Why I started the blog and other things

I’m getting asked a lot why I started the KGonTech blog. The reasons are quite simple:

1. I wanted to talk write about the technology I have being involved with for 34 years. Since I have been most currently involved in pico projectors and it is a hot topic today, I expect to mostly be discussing it. I hope to weave in some history and perspective from by other experiences. Read more

Being Useful (Part 2 – Ambient Light)

From “Projector Images and Room Light” by Dukane AV Products Division

For this second in this series on the Pico Projector “use model” I want to discuss the issues with ambient light.  A front projector, like most pico projectors today, have to deal with the fact their best case “black” is limited by the the existing ambient light. Read more