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 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  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.

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Karl Guttag
Karl Guttag
Articles: 243


  1. >I know me_wwwing to be a fan of Microvision ….

    I am also a MVIS shareholder.

    > simple answer is LCOS panels can use any of the lasers that LBS can use and can use lasers that LBS cannot use.

    That brings up the question. How many lumen can be used without using heat sinks? From your answer I would be interested the size of those LEDS.


    I brought up the PCB because I’ve seen the insides of 3M pico projector and DLP projectors. Their PCBs look rather large. But from image posted on the web I would be only guessing at there size. Both these companies have the money to do what they want.


    > an Intersil laser driver (5mm x 5mm)
    Nice. thanks

    > No, the light is not significantly spread out before the dichroic color combiners in an LCOS system

    I guess the laser’s light is spread out by a lens near the lasers.

    > the ShowWX which takes 4+ Watts for about 15 lumens.
    With MVIS’s Gen2 spec sheet. We see MVIS reaching 24lm (C2 without FDA confirmation) using 4.2W. do you know how many LED lumen will a LCoS need to equal MVIS’s claim of 24lm. 4.2V

    What is strange. why hasn’t Syndiant build a smaller micron HD display?
    One would think Syndiant would want to get into cell phone since there are laser out there.

    Thanks for taking the time to answer my questions. It is always interesting to read answers from someone who knows the Display panel business.

  2. Please just stop.

    That is not a laser feedback sensor. The optical path does not allow for it. And there is no such thing as a “despeckle lens”. Even if there was, it is in the wrong place.

  3. Karl,

    One thing that I don’t really have an understanding of is the laser eye safety aspects. Will you have some post looking at that?

    • I plan on doing a general overview of the subject of laser safety in a future article. There are a couple of detailed technical papers on the subject recently done by Dr. Ed Buckley and I have provided links to those two papers below. The rules are set by the IEC 60825-1 which can be bought for about $285, but even then it is pretty complicated to apply as can be seen from Dr. Buckley’s papers.

      The most basic concept of the standard is that the radiation is measure though a 7mm circle that is 10 centimeters away from were the light exits the device. The 7mm is suppose to approximate the a dilated human pupil. It becomes more complicated when you factor in pulsing and scanning duration for laser scanning. The wavelengths of light used for red, green, and blue also factor into the equation.

      With LCOS, the 7mm diameter circle is only sampling a small part of the whole image. As wider angle/shorter throw optics are used, the radiation per square goes down as a square law. If there was a 1:1 throw lens (image diagonal grows by 1cm for ever 1cm in distance) then at 10cm the image area for a 16×9 image would be about 4272 square mm and the area of a 7mm diameter circle is only 38.5 square mm or about 1/111th of the total area of the image at 10cm. If the throw angle is reduce to 0.5:1, which I expect to happen, then the radiation per square would be reduced by 4x. Additionally, even if the viewer gets inside the 10cm, the laser light has already been spread over the area of the panel and spread some more by the projection lens. The SSTDC LCOS+Laser projector was Class 1 at 20 lumens and Fujitsu introduced a Class 1 40 lumen laser projector that fit in PC bay.

      With laser beam scanning (LBS), the scanning beam is generally always much smaller than 7mm circle and while a shorter throw ratio helps, it only helps LINEARLY. This is in sharp contrast in the case LCOS/DLP case throw ratio helps as a square law. According to Dr. Buckley’s paper the Class 1 limit for LBS is only about 1 lumen and for Class 2 it will be between 11 and 15 lumens depending on several factors. Microvision’s recent spec sheet on their upcoming 720p device seems to confirm this as it says that a 25 lumen version would be Class 3R and the 15 lumen version would be Class 2

      Laser Beam Scanning paper by Dr. Ed Buckley:
      LCOS with Laser paper by Dr. Ed Buckley:

  4. Karl,

    I am a bit confused with the calculation showed above.

    Area = pi*r2 or (pi/4)*d2 ~ 77 sq mm

    If i am not wrong, the 7mm circle you are talking about is the size (i.e. diameter) of the pupil not the radius, but your calculations are based on 7mm circle (radius, seems pretty big eyes for humans).

    Also, the area for 16:9 image at 10 cm (10 cm as diagonal with 1:1 ratio) should be approximately 4300 sqmm.

    Just trying to understand the concept about how the LCOS and LBS would differ in terms of throw ratio and their impacts of linear and square. If you can explain that a bit more would be great.
    Hope my post makes it and Thanks for the information

    • Thanks. You are correct on my accidentally using the diameter rather than the radius in the calculation. You are also right about the area of the 16×9 image. This makes the ratio of the area of the pupil to the area of the image about 1/111. I have made corrections accordingly.

  5. Karl,

    If you dont mind can you please elaborate on the comment you made about LCOS following the square law for radiation to throw ratio while LBS following linear law. Or even you can refer somewhere and i can educate myself.

    Thanks a lot

    • Mihir,

      The fundamental issue is the density of radiation. With a panel based projector (DLP or LCOS), at any instant in time the light is spread over the whole microdisplay and then the entire image if enlarged by the projection lens. Thus if you measure at 10 centimeters away with a panel projector the radiation inside a 7mm diameter circle. For a 16 by 9 image and a 1 to 1 throw ratio, this ratio of areas of the image to the 7mm circle is about 111 to 1. If you had a 0.5:1 throw ratio so the image gets 2X bigger linearly, the area will be 4X bigger and thus the exposure at 10cm from the projector will be about 4X less.

      With a laser beam scanner, the beam spot that is scanned is well under 1mm tall. So at the worst case instance in time when the beam scans across the eye, essentially all the light from the beam is inside the 7mm circle for the duration of the time it takes to cross the pupil. The exposure/hazard is a function of how bright the beam is and how long it stays in one place on the eye and is fairly complicated (the Ed Buckley paper gets into the math/rules for the Class designation). IN the case of the LBS, if the throw ratio is shortened, then the the beam will move faster by that ratio and it reduces the duration of the exposure linearly.

      Hopefully this helps. Ed Buckley’s papers are the best public references I know of for explaining how the safety rules are applied. But note his papers make make assumptions that can vary from system to system so you have to use them as a guideline and not an absolute number.

    • Interesting question about bTendo since the article talks about it like it was STMicro’s product although you can see the bTendo name in some of the pictures. This would suggest that you have more than a casual interest in laser projectors.

      bTendo was in STMicro’s suite at CES 2012 as well. The word I heard is that STMicro has put some money into bTendo to keep them alive, but that it is not a large investment.

      bTendo uses a 2-mirror (one horizontal, one vertical) scanning technology. This is subject to less inherent distortion than the single mirror (this is discussed in some old Symbol papers ; ; — see particularly slide 15 in Wittenberg). The downside of the two mirror approach is that you have two mirrors, two sets of light losses, and perhaps (not sure) more alignment issues.

      Whether it is one or two mirrors, you still have the big issue of laser safety classification with beam scanning. bTendo by their own admission is class 2M and the Symbol papers suggest that class 2 was going to be their limit. This is a serious issue for companies that are going to be selling consumer product, they want class 1 (at most). bTendo, like Microvision, waffles about this issue on their web site ( by giving the definition of the safety classes and saying it is “It’s the overall system safely that counts”). You then have the issue that somewhere around only 20 lumens they become Class 3 that nobody will want to use for even a business projector. DLP and LCOS can be class 2 at over 1000 lumens.

      Then you get into most of the same issues that Microvision has with beam scanning including:

      1. The lasers it needs are less efficient and not cost effective for a number of years.
      2. The horizontal scan is constantly accelerating and decelerating from zero to peak speed in the middle which means you have to compensate in both time and drive strength which limits efficiency. This means you need more powerful lasers and you spend a lot of power controlling the lasers.
      3. If they drive the lasers in both directions of the horizontal scan, then the lasers are off over half the time. If they drive the lasers in both direction then you have flicker and line-line spacing issues that Microvision has which in turn effectively lower the resolution. This means they will need more powerful lasers, more expensive lasers than one might otherwise think as well as impacting efficiency.
      4. The big power loss in beam scanning is in driving the lasers. They have to have high speed analog power drivers which consume/waste power. I have not seen anything that lets you measure the power consumption of bTendo’s system. Microvision so far has demonstrated only about 3 lumens per Watt which is horrible (the better LCOS and DLP systems are about 7 to 10 lumens per Watt).
      5. I have not seen the size and power of bTendo’s control electronics but this is another issue for beam scanning systems. Basically, they have about twice as much to do as with a DLP or LCOS system in terms of control because they have to process the image for the beam scanning process, control the mirror, and control the laser with it variable motion. Microvision’s electronics for example is huge compared to DLP and LCOS and consumes a lot of power.

      I probably missed some points, but the key thing is that the laser beam scanning companies want you to focus on the size of the optics and the power losses in the optics ONLY. This is the old “magician’s trick” of misdirection. The serious issues with LBS are in the size and power losses in the electronics that have to do with driving/controlling the laser and the mirror.

      In summary, until they get “serious” and talk about cost, power, availability, and brightness/safety, I think it is just a R&D demonstration that STMicro is testing the market with. It still doesn’t change the fact that there are serious technical, physical, and business issues with LBS.

  6. Holy Cow. There goes Karl again spewing out half truths using scientology to decipher issues in which he has little knowledge.

    Using lasers in an LCOS system is near ludicrous. It adds tremendous power on a system that already consumes high power.Then you also add speckle and have to remove it using some expensive vibrating, dual-plane screen, or some other silly technique like Dyoptyka (in-phase aligned mechanically mirrors vibrating at 100kHz – can you say power hog, voluminous, etc.)

    Why did Nikon kill LCOS in its projector camera? They could have gone to lasers + LOCS. They didn’t. LEDs are too diffuse. Won’t work.

    Ed Buckley’s paper makes several bad assumptions – the light power on laser/MEMS projectors is much higher, and fully eye safe up to 30+ lumens.

    I do not work for Microvision, do not own stock. That company has decent technology, but is too expensive and burdened their financials with too much stray funding into high-end technologies that just won’t pay off at all, or for a long time until MVIS closes its doors. Btendo and several other companies will eat their lunch – lean, mean, hungry, focused. Patents will save MVIS, if they have deep pockets to go after laser-MEMS companies. I predict MVIS shuts its doors by Dec 2012.

    • Once again your out putting out vitriol without any facts to back it up.

      You comment on using lasers with LCOS makes no sense at all. Laser are a tremendous help to LCOS as they have polarized light and low etendue which enable LCOS to make smaller pixels/panels, use smaller optics, reduce costs, and improve efficiency. Your claims that it “adds tremendous power” is baseless. Today LCOS is MUCH lower in power than Laser Beam Scanning.

      The issues with speckle reduction are much less for panel (LCOS or DLP) than they are for laser beam scanning. You are just very misinformed.

      Nikon was using a color filter LCOS panel by Himax which had very poor color quality and contrast but it was cheap. What a silly comment about why they didn’t go to Laser + LCOS. Lasers are not cost effective today for any high volume application. On Nikon’s second generation, they went with DLP with LEDs (in spite of LEDs being “too diffuse” as you wrote) to get better color and contrast. They certainly were not even considering LBS. The bigger issue is that any pico projector today is really too expensive to embedded in a camera so they are only going into a few test-the-market type products.

      Why don’t you point out where Dr. Buckley was wrong? Microvision’s own Gen2 flyer ( states that “25 lumens would be a Class 3R device.” Whether or not you work for Microvision or own stock, you are simply repeating the marketing spin of the laser beam scanning company(s).

      Microvision has many problems both financially and technically. I suggest you read though my blog and understand the content including the issues with driving the the laser in a LBS system. You seem to only have a very superficial knowledge of the issues and have bought off on all the marketing spin by the LBS companies. You have bought off on the “big lie” that the availability of direct green lasers is their only problem, I guarantee that it is not. The other LBS companies can be “lean, mean, hungry, focused” as you put it and still fail because there are fundamental problems that cannot be solved, at least in a reasonable time frame if ever.

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