Celluon/Sony/Microvision Optical Path

Celluon Light Path Labled KGOnTech

Today I’m going to give a bit of a guided tour through the Celluon optical path.  This optical engine was developed by Sony probably based on Microvision’s earlier work and using Microvision’s scanning mirror.   I’m going to give a “tour” of the optics and then give some comment on what I see in terms of efficiency (light loss) and cost.

Referring to the picture above and starting with the lasers at the bottom, there a 5 of them (two each of red and green and one blue) that are in a metal chassis (and not visible in the picture).   Each laser goes to it own beam spreading and alignment lens set.  These lenses enlarge the diameter of each laser beam and they are glued in place after alignment.  Note that the beams at this point are spread wider than the size of the scanning mirror and will be converged/focus back later in the optics.

Side Note: One reason for spreading the laser beams bigger than the scanning mirror is to reduce precision required of the optical components (making very small high precision optics with no/extremely-small defects becomes exponentially expensive).  But a better explanation is that it supports the despeckling process.  With the wider beam they can pass the light through more different paths before focusing it back.  There is a downside to this as seen in the Celluon output, namely is still too big when exiting the projector and thus the images are out of focus at short projection distances. 

After the beam spreading lenses there is glass plate at a 45 degree angle that splits a part of the light from the lasers down to a light sensors for each laser.   The light sensors are used to give feedback on the output of each laser and adjust to adjust them based on how they change with temperature and aging.

Side Note:  Laser heating and the changing of the laser output is a big issue with laser scanning. The lasers very quickly change in temperature/output.  In tests I have done, you can see the effect of bright objects on one side of the screen affecting the color on the other side of the screen in spite of the optical feedback.   

Most of the light from the sensor deflector continues to a complex structure of about 15 different pieces of optically coated solid glass elements glued together into a complex many faceted structure. There are about 3 times as many surfaces/components as would be required for simply combining 3 laser beams.   This structure is being used to combine the various colors into a single beam and has some speckle reducing structures.  As will be discussed later, having the light go through so many elements, each with their optical losses (and cost) results in loosing over half the light.

lenovo 21s cropFor reference compare this to the optical structure shown in the Lenovo video for their prototype laser projector in a smartphone at left (which uses an STMicro engine see).  There are just 3 lenses, 1 mirror (for red) and two dichroic plate combiners to combine the green and blue and a flat window. The Celluon/Sony/Microvision engine by comparison is using many more elements and instead of simple plate combiners they are using prisms which while having better optical performance, are considerably more expensive.  The Lenovo/STM engine does not show/have the speckle reduction elements nor the distortion correction elements (its two mirror scanning process inherently has less distortion) of the Celluon/Sony design.

Starting with the far left red laser light path, it goes to a “Half Mirror and 2nd Mirror” pair.   This two mirror assembly likely being done for speckle reduction.  Speckle is caused by light interfering with itself and by having the light follow different path lengths (the light off the 2nd mirror will follow a slightly longer path) it will reduce the speckle.  The next element is a red-pass/green-reflect dichroic mirror that combines left red and green lasers followed by a red&green-pass/blue-reflect dichroic combiner.

Then working from the right, there is another speckle reduction half-mirror/2nd-mirror pair for the right hand green laser followed by a green-pass/red-reflect dichroic mirror to combine the right side green and red lasers.  A polarizing combiner is (almost certainly) used to combine the 3 lasers on the left with the two lasers on the right into a single beam.

After the polarizing combiner there is a mirror that directs the combined light through a filter encased between two glass plates.  Most likely this filter either depolarizes or circularly polarizes the light because on exiting this section into the open air the previously polarized laser light has little if any linear polarization.   Next the light goes through a 3rd set of despeckling mirror pairs.   The light reflects off another mirror and exits into a short air gap.

Following the air gap there is a “Turning Block” that is likely part of the despeckling.   The material in the block probably has some light scattering properties to vary slightly the light path length and thus reduce speckle and thus the reason for the size/thickness of the block.   There is a curved light entry surface that will have a lens effect.

Light exiting the Turning Block goes through a lens that focuses the spread light back to a smaller beam that will reflect off the beam scanning mirror.  This lens set the way the beam diverges after it exits the projector.

After the converging lens the light reflects off a mirror that sends the light into the beam scanning mirror assembly.  The beam scanning mirror assembly, designed by Microvision, is it own complex structure and among other things has some strong magnets in it (supporting the magnetic mirror deflection).

Side Note: The STM/bTendo design in the Lenovo projector uses two simpler mirrors that move in only one axis rather than a single complex mirror that has to move in two axes.  The STM mirrors both likely uses a simple electrostatic only design whereas Microvision’s dual axis uses electrostatic for one direction and electromagnetic for the other.  

Finally, the light exits the projector via a Scanning Correction Lens that is made of plastic. It appears to be the only plastic optical element as all the other elements that could be easily accessed.   Yes, even though this is a laser scanning projector, it still has a correction lens, in this case to correct the otherwise “bow-tie” distorted scanning process.

Cost Issues

In addition to the obvious cost of the lasers (and needing 5 of them rather than just 3) and the Scanning Mirror Assembly, there are a large number of optically coated glass elements.  Addtionally, instead of using lower cost plate elements, the Celluon/Sony/Microvision engine use much more expensive solid prisms for the combiner and despeckling elements.   Each of these has to be precisely made, coated, and glued together. The cost of each element is a function of the quality/optical efficiency and which can vary significantly, but I would think there would be at least $20 to $30 of raw cost in just the glass elements even at moderately high volumes (and it could be considerably more).

Then there is a lot to assemble with precise alignment of all the various optics.  Finally, all of the lasers must be individually aligned after the unit with all the other elements has been assemble.

Optical Efficiency (>50% of the laser light is lost)

The light in the optical engine passes through and/or reflects off a large number of optical interfaces and there are light losses at each of these interfaces.  It is the “death by a thousand cuts” because while each element might have a 1% to 10% or more lose, the effects are multiplicative.   The use of solid rather than plate optics reduces the losses but as at added cost.  You can see in the picture of the walls of the chassis spots of colored light that has “escaped” the optical path and is lost.  You can also see the light glowing off optical elements including the lens; all of this is lost light.  The light that goes to the light sensors is also lost.

Celluon laser lable IMG_9715

Laser Warning Label From Celluon Case

Some percentage of the light that is spread will not be converged back onto the mirror.  Additionally, there are scattering losses in the Correction Lens and Turning block and in the rest of the optics.

When it is multiplied out, more than 50% of the laser light is lost in the optics.

This 50% light loss percentage agrees with the package labeling (see picture on the left) that says the laser light output for Green is 50mW even thought they are using two green lasers each of which likely outputs 50mW or more.

Next Time: Power Consumption

The Celluon system consumes ~2.6 Watts to put up a “black” image and ~6.1 Watts to put up a 32-lumen white image.  The delta between white and black being about 3.5 Watts or about 9 lumens per delta Watt from back to white.  For reference, the newer DLP projectors using LEDs can produce about double the delta lumens per Watt.  Next time, I plan on drilling down in the power consumption numbers.

26 comments

  1. Joe says:

    Karl,

    Interesting information. One question about the output numbers you referenced from the label on the back of the Celluon projector.Is it possible that the output is per laser and not the total? Would one blue laser really have that much greater output than two green?

    You said Sony is using a engine based on Microvision’s earlier work. Do you think there have been improvement made since this engine?

    Lastly, are there any disadvantages you see in the ST Micro engine because of the size and only using three lasers? Thanks.

    • Joe says:

      Karl, one additional question on the laser output. Why does just the green output signal to you there is a 50% loss? There are two red lasers as well, does the 90mw output signal a 50% loss?

      It is my understanding that the human eye is mouch more sensitive to green laser light and perceives it as brighter even at lower outputs. Couldn’t this lower out put you said signifies a 50% light loss be by design? Thanks.

      • Karl_Guttag says:

        Joe,

        The red probably suffers about the same loss and why they need two reds. The blue slightly less as it goes through less elements but powerful blue lasers are more readily available. I just quoted green because I had a pretty good idea as to the available green laser’s raw output power versus the output spec on the box so I knew there was at least a 50% loss. I didn’t know what red and blue laser they were using so there was no way to make a calculation.

        It is a flat out myth/lie that has been promulgated by Microvision that laser light is somehow brighter than other types of light. There is zero evidence but Microvision talks about some study that was done that has never been released. There is a Helmholtz–Kohlrausch or HK effect of highly saturated colors but this mostly applies to red (and has almost no effect on green) and ONLY if you are talking highly saturated colors and not a white image and applies to LEDs and other forms of light as well as lasers. Microvision used one part fact mixed with 99 parts lie to promote this myth. They never defend it, they just keep repeating it and reporters not knowing any better repeat the lie (“if you repeat a lie often enough people will believe it”).

        The eye is more sensitive to green light in terms of brightness and I discussed this a while back (see http://www.kguttag.com/2011/12/16/diode-green-lasers-part-1-wavelength-and-efficiency/). In terms of a projector you need to “balance” the color to get a perceived “white point.” It turns out that for say a standard D65 (a somewhat “warm” white) if the Green is 50mW at 522nm, then you want 64mW at 639nm of red and 28.5mW at 445nm of blue (the wavelength are the ones on given for the Celluon unit). The projector says it outputs 50mW of greeen, 90mW of red, and 85mW of blue. So they have way more red and blue then they need for color balance and this probably explains why the white point is so far to the red (and why “white” shows up redish in photos).

        The eye is much more sensistive to green in terms of milliwatts versus lumens. Assuming a color balanced D65 white point with the wavelength above, 28% of the lumens will come from red, 71% from green, and just 2% from blue.

        • joe says:

          Thanks, learned a lot.

        • geo says:

          Syndiant/Cremotech/SK Telecom/UO are making the exact same claim re laser lumen’s at UO’s site.

          “NOTE: perceived brightness is substantially higher on a laser diode when compared to an LED pico projector of similar lumens.”

          • Karl_Guttag says:

            It is still not true, i.e. a lie, and not supportable/defendable by any published and reviewed study. I have no connection, say, or input in what they write.

            Karl

        • Joe says:

          Karl,

          Is there anything to the word “perceived ” when describing the brightness that makes the claim accurate.

          • Karl_Guttag says:

            Joe,
            Lumens are a measure of perceived brightness and whether they are “laser or not” makes no difference. I think the genesis of this fiction was put out by Microvision starting in the 2008 time frame in a few places, it has been left unchallenged and moved into the laser projector “lore” (and unfortunately it has been picked up by others such as with the UO SMART BEAM LASER marketing). It is the old saying that if you tell a lie often enough people will start believing it. Below are two references from circa 2008 (the earliest I have found) were Microvision was making the claim:

            From 2008: http://www.laserfocusworld.com/articles/print/volume-44/issue-5/features/picoprojectors-nanosecond-modulation-makes-cell-phone-projectors-possible.html
            From circa 2008 (no date on the paper but citing references from 2000 to 2006) http://ssr.glidingsport.ru/download.php?id=679
            Per a 2008 laser focus world article, Microvision based their claim on the Helmholtz-Kohlrausch (HK) effect and it looks like nobody ever checked them out. Quoting from the 2008 Laser Focus World article:

            Using lasers as light sources is particularly valuable in projectors. The Helmholtz-Kohlrausch effect causes saturated colors in very narrow wavelengths to be perceived as up to 50% brighter than broader wavelengths of colored light, such as those produced by light-emitting diodes. Thus, the observed image has a significant increase in brightness without additional battery power.

            But the “HK effect”, while true, only applies to highly saturate colors and then mostly to the red colors (see graph in the Mike Woods Consulting article below) and has little effect on green. Note that the effect occurs with LEDs as well (and where it is used to an advantage of LEDs over red colored incandescent bulbs in signaling). It has NO effect when you show white and were lumens are measured for brightness. Additionally, with a pico projector the light output is so low that the least amount of ambient light means that that colors will not be “highly saturated”.

            Helmholtz-Kohlrausch effect see: http://www.mikewoodconsulting.com/articles/Protocol%20Summer%202012%20-%20HK%20Effect.pdf and https://en.wikipedia.org/wiki/Helmholtz%E2%80%93Kohlrausch_effect

          • bob says:

            “It has No effect when you show white” I am a little confused here. If the Helmholtz does apply to highly saturated colors I would think there is some merit to the claims from all the companies saying so. I don’t see the purpose in projecting just white.

            I will admit, most of this is way above my pay grade so to speak. I just don’t understand how you say the HK effect is true with highly saturated colors, but companies saying there is perceived brightness are not telling the truth. Even if there is no effect when projecting white, who projects just white? Thanks in advance.

            I

          • Karl_Guttag says:

            Bob,

            The spec for a projector on “Lumens” is for a white/brightest image. For white there is next to no saturation of the color (it is white). So when they claim 32 lumens, this is for an unsaturated color image and thus no HK effect.

            If they were talking about pure red (only) lumens then maybe there could be some reason to bring up the HK effect. But note with a low lumen projector the ambient light is generally so significant that even if the projector is projecting a saturated red that unless the room is totally dark the resultant screen image will not be that saturated.

            Beyond all this, the Celluon project NEVER projects a pure saturated color. When you project a “pure green” image the projector still mixes some red and blue in it (and similarly for red and blue they mix the other two colors in). The reason to mix colors even for a “pure” color is to match the color space used by most images in video. If you don’t “detune” the pure saturated colors, then for example, green grass will look like it is glowing/plastic rather than like grass in a picture or video (this is true for LED as well as laser illumination). So even with a “pure red” there is very little HK effect because A) they don’t project a pure saturated red, and B) the ambient light further reduces the saturation.

          • trololo says:

            I would say perception is indeed the keyword here. How the differential process and opponent process work for the cone cells for wide spectrum (LED) and narrow spectrum (Laser) color mixing directly impacts the perceived luminance. The hint of “saturation” in Helmholtz–Kohlrausch effect indeed originates from this differential processing.

          • Karl_Guttag says:

            trololo,

            It is all about perception, that is not the issue. They are miss-applying the concept for marketing purposes. The spectrum does not have to be extremely narrow as with lasers, for the effect to work. In fact the effect has been noted with LEDs, particularly red used in airport lights. With a low lumen projector and the least amount of ambient light, any effect is quickly lost.

            There are no studies that back up the marketing claims of the laser projector makers. If the effect were real and as much as they wish, there should be unbiased papers showing the effect.

  2. Ken says:

    It’s surprising to learn about the complexity in the optical path for the Celluon projector. But I don’t mean to be only critical of the Celluon projector, since optical complexity is commonplace in all image projectors.

    I wish there were some ways to reduce complexity and cost for Celluon and all micro projectors in general.

    For example…

    How can optical complexity be reduced in micro projectors?
    ———————————————————
    Celluon has a 15 piece optical glass element (probably of various highly machined, glass materials) — which seems to be an absurdly complex, expensive, and heavy component. Moreover, due to the use of lasers there is a de-speckling mechanism comprised of some half-mirror, full-mirror combination elements.

    To all readers: Is there any new research on the horizon and new prototyping occurring to reduce optical complexity in image projectors?

    For example:

    Might the use of injection molded transparent plastics be of value? Optical elements could be injection molded that refract and diffract in novel and a highly-controllable manner. Perhaps even 3D printing may have potential value in this area, as 3D printing could facilitate various optical materials (e.g., different index of refraction) to be molded together to render complex optical elements.

    To dream a bit, perhaps new manufacturing and construction techniques could then reduce optical element count, cost, weight, and complexity in the finished product.

    Also on the Celluon and other projectors, is there a means to reduce power consumption for the “black” image?
    ——————————————————————————————————–

    Karl mentioned “The Celluon system consumes ~2.6 Watts to put up a “black” image and ~6.1 Watts for a visible image.”

    In other words, the black image is still consuming nearly 43% of power usage in contrast to when the image is lit. This seems exceptionally poor. I would intuitively think that maybe 10-20% of maximum power usage would be more reasonable during a “black” image. Couldn’t one “turn off” the laser diodes and maybe even the actuated mirror during black image?

    Where is Celluon consuming so much power during the “black” image period?

    Again, to dream a bit, wouldn’t it be wonderful if image projectors could reduce power consumption to 10-20% of maximum power usage during a “black pixel” region (for panel type projectors) or a “black pixel” period of scan time (for scanning type projectors). The results would be a dramatic increase in play time of movie video and perhaps other types of image content.

    • Karl_Guttag says:

      Thanks Ken,

      Believe me, the complexity is there not because they want to be complex (to the contrary they want to be simple and cheap) but to make it work.

      In the Celluon/Sony/Microvision case they are trying to combine 5 lasers which adds about 30% of the components. They have to have lens to spread the beam, elements to aligned the lasers, ways to combine the various colors into a set of coaxial beams. Then there is the added elements to reduce speckle. Some of the size/volume is a function of the angle that the light has to enter and leave the scanning mirror.

      Weight, however, is not a big issue as the elements are still not that big and heavy.

      If you look at the left to right width of the main color combiner element, it is set by how far the lasers are set in a line including their case and the surrounding heat sinking case. Packing the lasers closer together would reduce the size.

      Injection molded plastics of any significant thickness are problematic with the highly polarized light coming out the laser. Note in the Celluon projector, only the output correction lens is plastic and only after the light has been depolarized.

      One can expect laser “line width” (laser speak for the frequency spread of the laser) and this alone will reduce speckle to the point that despeckling may not be necessary. Someday there may be a way say with holographic elements to reduce the size and complexity. In theory you could shoot 3 lasers at a ideal holographic element that would make them coaxial even though they enter from different angles.

      I hope to get into more with the power consumption in my next article. Part of the power taken in black is that they have to keep the scanning mirror running and there are still ASICs doing processing if the pixels are all black. On many lasers if you want them to switch fast (as required for laser beam scanning), you also have to keep the “primed” and ready to go with a sub threshold (below visible) current.

      • Ken says:

        Thanks Karl. I was not aware of that lasers can be kept in a “primed” state with low current flow for fast full-power on switching. This may be what Celluon designers did as well.

        It’s always a pleasure reading your tech comments and the conversation that ensues with your readers.

        However, help me better understand the use of plastics in optics. You mentioned: “Injection molded plastics of any significant thickness are problematic with the highly polarized light coming out the laser.”

        Does polarized light behave differently through a plastic PMMA lens relative to a glass lens of equal refractive power?

        The only adverse effects I can think of is that plastic may be more prone to deform or melt along the intense laser beam than glass. Large plastic PMMA molecules (being more complex than silicon glass molecules) might be more prone to absorb or scatter photons, increase temperature, reduce polarization, and perhaps even change refractive characteristics.

        Am I on the right track here? Or did you have another perspective on the use of plastic optics?

        -Ken

        • Karl_Guttag says:

          Ken,
          First a point of clarification, I don’t think Celluon designers did any “design” with the light engine. I would think that Sony did the design based on the older Microvision design and the spec/requirements of the lasers. Celluon probably just used the engine provided by Sony.

          You are on the right track with the effects on polarization. Polarized light definitely behaves differently through PMMA (know as Acrylic to most people) and Polycarbonate plastics. The stress from molding and how the plastics flows and cools will cause the plastic to show birefrigence and the light passing through at different point will have its polarization affected differently. Glass does not have this problem. There are some optical plastics that that can be diamond cut (not molded) that can be used with polarized light I have been told.

          If you send polarized light through a “thick” piece of plastics (PMMA or the like) it will come out unpolarized (but many not uniformly so).

          One of the problems in dealing with polarized light in a projector is that you have to use glass everything (lenses and plates) as long as you need to preserve the polarization in the optical path. As in the case of the Celluon engine, in the later stages you may depolarize the light and then use plastic.

          Karl

  3. joe says:

    Karl,

    One last question for you. Do you ever answer some questions offline? You have my email address. Thanks.

    Joe

  4. Chris says:

    Karl,

    I have a question about the laser safety classification of the Celluon (and the new Sony) device. I thought that class 3R is limited to 5mW output. How can this laser projector in class 3R if the specification is “output Red 90mW / Blue 85mW / Green 50mW (
    Red 639nm / Blue 445nm / Green 522nm)”?

  5. Y. Cem Aygun says:

    First of all thanks a lot for the incredible work and articles. Your studies will definitely have an impact…

    I have a very funny question: Is there any perceivable impact of the ridiculous “advertised” horizontal resolution (admittedly upscaled) or is it overshadowed by the incompetence of the output?

    I tried to see any sign of “non square” pixels in your samples (which is what it has to be for the claimed resolution and aspect ratio) but I could not. So I am guessing the unclarity of the output conceals the effect (which should be apparent on raster images). I would like to know how much toll this “upscaling” takes…

    PS: I cannot begin to explain how much I personally appreciate your efforts; as we have been suffering from this “fake specs war” for almost two decades in the digital camera market. It did nothing but harm. And although industry is slowly taking steps back, it still is there to haunt the consumers (like the latest gopro still being sold as a 4K video recorder, whereas it’s lens setup can only resolve 2.3K. The sensor having that kind of capability on paper was good enough for the marketing department; they did not care if the final results were nowhere near their claims.)

    Seeing the same pattern emerge in the projector market is just painful. I hope they come to their senses and let their engineering department design their products instead of the marketing one…

    • Karl_Guttag says:

      Y.,

      Thanks for your appreciation. I have been very busy starting up a new company and my blog updates have fallen behind.

      In terms of specmanship, the projector market has been bad for a long time. There is nobody that really checks the specs so it is a bit of “liars poker” where companies just make up numbers with the thinnest excuses (it is pretty much “how much do you think you can get away with”). I have found that Lumens are usually off about 20% and I have seen them off by 50% when measured. The contrast ratios given are also ridiculous. They always use “On-Off” contrast when they should be using “ANSI” (which can be lower by 10X or more the silly numbers they give); but nobody will give their ANSI numbers anymore because they are so low compared to the On-Off number and they assume (rightly) that most consumers won’t understand the difference.

      You would think resolution is a place where people would not fudge, but this has also being going on for a long time. Back in the CRT days, there were companies that claimed higher resolution than the number of phosphor triad (RGB) that they had. TI’s “diamond pixel” also had a bad effect on resolution as while they has the “right” number of mirrors, they are arranged such that images have to be re-sampled. Even with a “true” resolution panel (DLP or LCOS) the is going to be some effective resolution loss due to optics; a more reasonable metric is 50% MTF (see for example http://www.imatest.com/docs/sharpness/ for how it applies to lens measurement) which loosely translates that if you put up a series of black and white stripes, the black stripes will be 1/2 the amplitude of the white stripes.

      Back to your question as I understand it. From what I can tell is it NOT just a scaling problem that is lowering the effective horizontal resolution. The Sony laser scanning engine used in the Celluon projectors (and I would think in the Sony branded projectors using the same engine) is inherently incapable of resolving 1920 or 1280 pixels horizontally; its resolution is closer to 640 pixels horizontally by about 360 pixels vertically. There are multiple factors; the inherent Lissajous scanning process has to be re-sampled onto a rectangular grid, the way the Microvision scanner does interlacing effectively reduced the vertical resolution by 2X at the outsides of the image, spot size of the laser beam is too large (I suspect this is cause by the despeckling optics), they can’s seem to control/coordinate the laser on-off with the scanning process to this high a resolution.

      I have proven the resolution of the Celluon (Sony engine based) projector is nowhere near 1920 or even 1280 pixels horizontally with of serious of photos I have posted. What I get back is mostly garbage from people/stockholders trying to defend Microvision (the supplier of the laser scanner in the Sony engine) trying to discredit my results. I have gone so fare as provided the test patterns so that anybody can see that I am correct (they don’t have to use mine, and resolution test pattern would show the same). So far nobody has been able to refute my results.

      The burden of proof should be on the manufacturers to prove their claims, unfortunately there is nobody to to police the false claims being made so in this environment marketing people are free to make any claim they think they can get away with.

  6. Joaquin says:

    hello I wonder if this optical system laser used in the Sony projectors mp- cl1 and Celluon improve or make last longer the lifetime of the laser or otherwise can reduce and if it is better for performance or may worsen and what the approximate actual life of this optical system
    thank you

  7. N says:

    Hi Karl,

    It’s been almost a year since since you last blog.

    A few questions:

    1) In Culluon and Lenovo’s projector, what type of lasers are they using? Especially the green laser? From which supplier?

    2) How’s the development of DGL? You suggested before that multimode DGL is better than single mode in terms of speckle reduction. Is there any promising products?

    3) Seems Microvision is still surviving in the market and this blog¬¬LOL ¬I aways wondering, there is good applications for LBS technique in scanning microsocopy, confocal microscopy, superesolution microscopy, or anything using ultrafast laser, why don’t they focus on academics and research rather than invest so much on pico projector?

    • KarlG says:

      N,

      1) I don’t know who’s lasers are in the Celluon and Lenovo projectors.

      2) Green laser development has been slow. The two big problems are that the “physics” to make a direct green laser is tough/difficult and the market is still very small (very few projectors being made and there are not a lot of other markets with much volume for direct green lasers). Thus it takes a lot of R&D investment for what appears to be a small payoff. Multi-mode lasers will have lower speckle as each mode hope is incoherent with the others, but not multi-mode lasers cannot be use with laser scanning (as the mode hopping makes for a noisy image due to the scanning process).

      3) From what I see, Microvision survives by selling stock to keep to pay management salaries and not selling products at a profit. They keep finding gullible people that don’t have a clue how the technology works and its severe limitations. The problem for Microvision the other applications/research you mention is that they can’t sell stock based on these applications.

  8. N says:

    Thanks for the insights!

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