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Thread: ILDA Format BS

  1. #21
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    Quote Originally Posted by carmangary View Post
    Some assumptions here are that laser display will stay analog. As soon as a smart person creates a better galvo driver (perhaps one that offers feedback information to the host) with a bidirectional digital interface any argument of using WAV falls flat on the floor.
    Actually, there's been a good bit of speculation around exactly that idea, Gary: Moving the digital-to-analog converstion process *off* the laser show controller and into the scanner amp itself. Several people were talking about it on the ILDA cruise. Rumor has it that great minds are investigating the concept, and at least one person has claimed to see a prototype (that evidently didn't work very well, but it was an early attempt.)
    Quote Originally Posted by keeperx View Post
    um.. whats all this about "points" instead of WAVE? ilda files store points SO DO JAMES"S WAVES.. you can never send "POINTS" to your scanner you send VOLTAGE.. no matter how you look at it, you are sending analog voltage.
    Unless scanner amps evolve to have digital inputs, as discussed above. There are a lot of good reasons to do this, not the least of which is the fact that it's hard to send analog signals over long distances with the current ILDA cable standard. A digital link would be far superior.

    Of course, this might increase the cost of the scanners, but it would also offer less noise and better performance. (And controllers would probably become cheaper in the process.) Time will tell I guess, but I'm keeping my eye on the boys from Cambridge...

    Adam

  2. #22
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    same thing is being done in network with a "Media converter"
    basically you use a digital signal (fiber/Ethernet/802.11 or whatever) and put the dac in the projector. the dac acts as the media converter but the signal comes over a digital wire.

    I can't see selling a set of scanner amps that have a built in DAC, it makes no sense.. they are components.. maybe in the LOW end it would be OK or as an OEM thing
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    You have to think outside the box a little. You can do more than just combine a DAC board and scanner amp board. You can integrate them and allow them to work together. I could imagine a nice DAC/scanner amp where you feed it frames as fast as you can and it figures out out fast it should send them to the galvos. And instead of just sending incremental point values, it could use feedback from the galvo positioner sensor to add real time interpolation to the voltage coming from the DAC. Then, maybe enhance the thing a bit farther to where it knows how to draw a circle, or a curve, or shapes.

    What I am talking about is the difference between an unaccelerated graphics card of the 80s and one of the 3D DirectX cards that we see today. That opened up a whole new world of graphics. And being able to push some of the drawing to the scanner would also open up a new world. Today, we can do a pretty good job of drawing in software but it's a bit of guesswork. We have to add points to corners, and hope that we didn't add too many or too few. We have to correct for other things as well. By combining the DAC and scanner amp so that position information is known you can take that burden of guesswork off of the programmer and make it so that a perfect angle is drawn evertime because the hardware will make sure that it reaches the end of a segment before turning the corner. That would be an awesome! But, I can't imagine anyone sending frame data to the device using analog voltages in that case. And, it is currently impossible to do it without combining the DAC and scanner amp since there is no feedback information available from the ILDA cable.

    Ask any laser show software programmer if they would like to have the functionality I just described and I bet they all say yes. It would still be nice to have analog control for abstracts or possibly some other things but in general, analog is not desireable.
    Last edited by carmangary; 01-13-2009 at 05:46.

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    Quote Originally Posted by carmangary View Post
    You have to think outside the box a little. You can do more than just combine a DAC board and scanner amp board. You can integrate them and allow them to work together. I could imagine a nice DAC/scanner amp where you feed it frames as fast as you can and it figures out out fast it should send them to the galvos. And instead of just sending incremental point values, it could use feedback from the galvo positioner sensor to add real time interpolation to the voltage coming from the DAC. Then, maybe enhance the thing a bit farther to where it knows how to draw a circle, or a curve, or shapes.
    OMG! Were you on the ILDA cruise, Gary? Or maybe you've been talking with Chris Stuart lately... Because that is *exactly* the sort of thing they were talking about. (Specifically - just sending digital frame data and letting the scanner amps figure out the best way to display them. Also real-time feedback all the way to the digital frame buffer on the scanner amp.)
    What I am talking about is the difference between an unaccelerated graphics card of the 80s and one of the 3D DirectX cards that we see today. That opened up a whole new world of graphics.
    There was considerable talk about putting a DSP right on the scanner amp. I'm assuming this all related to some significant advance in scanner speed (MEMS scanners maybe?) but everyone was pretty tight-lipped about that.
    Today, we can do a pretty good job of drawing in software but it's a bit of guesswork. We have to add points to corners, and hope that we didn't add too many or too few. We have to correct for other things as well.
    Yeah, that was the whole point... Artwork would never need to be modified to account for deficiencies in the scanners. You send the artwork to the scanners as is, and they figure out for themselves the best way to draw it (within their own abilities). Of course, the whole idea will obsolete an entire generation of laser show controllers (and scanners), but the performance increases might be worth the cost...

    Adam

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    but in general, analog is not desirable
    WHAT ? ! ? !

    Life is analog, physics is analog, galvo's are analog, movement is analog, light is analog..

    The digital world strives every day to be as good as analog...

    no matter how you look at it, you ALWAYS loose something when converting information from analog to digital .
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    Adam, actually I just made all of that up as I was sitting there typing. I don't think it is any revelation at all. That's just the way most computer controlled hardware works. In fact, when I first starting messing with galvos it took me awhile to understand how they worked because they DON'T work that way.

    Keeperz, computers aren't analog and as long as galvos are being controlled by computers analog will not be a desirable way of controlling them. The galvos themselves will always be analog at that level, but by adding the type of thing I mentioned to them you can improve it because you'll be able to control the speed at which the analog voltage changes. The reason you have to tune your galvos is because they are analog devices and you have to make sure the feedback and gain is just right in order to display an image properly. The type of thing I explained above would make tuning less critical. Even a poorly tuned set of scanners would produce a perfect image. They would just work harder at it and might be slower.

  7. #27
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    I suggested DSP based self amps at the ilda tech comm meeting 5 years ago, and BB and Dirk both turned around and said too expensive. The cambridge people grinned and turned away a bit. Guess what, they're here if your doing laser platemaking for printing. Cambridge makes them, GSI makes them, and they self tune, and can change tuning on the fly.

    Canon (as in canon cameras) makes galvos with digital feedback, yes, digital , laser based interferometric encoders, for precision laser micro machining. I've been in a room watching them sinter steel dust into turbine blades for jet engines with a 500 watt CO2. (cant say where, I signed a ND) They were moving mirrors the size of new jersey at 5000 steps per second. The steel was getting sintered at a accuracy of .0001 inch with the scanners 2 feet away. The machine floated on a granite slab on air for a reason.

    So yes, digital is possible, but in the near future you gonna get digital dsp amps still interfaced with the analog position sensors first. And there will always be analog in the drive coils. And there is analog in the form of the rotor inertia and bearing noise and thermal noise that you will NEVER get rid of.

    At some point, it still has to be analog. God and/or the Laws of Physics both say so. :-)

    These have been out to selected customers for years.
    If you have to ask the price, right now you can't afford them:

    http://www.cambridgetechnology.com/p...l%20Servo.html

    http://www.gs-scanners.com/opticalsc...olution.html#h

    But its just a matter of time before they spill out of a marking machine onto the bay, but good luck getting the proprietary interface specs.

    These are NOT the ones I've seen, but they are talking about them:

    http://www.canon.com/optoelectro/7_2D/index.html

    Do note the +- 96V power supplies and 22 amps peak currents, a Cambridge is what, +- 35V and 6-8 amps peak?

    Steve
    Last edited by mixedgas; 01-13-2009 at 08:53.

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    I'm not surprised that they already exist. The funny thing is that I have probably worked with them before and never realized it since I have had to interface with GSI Lumonics wafer marking tools in the past.

    You know the drill, Cambridge or whoever will make it first but they will be expensive, then the Chinese will catch wind of it and copy it, then we'll all have it. It will be tougher for them, though, since they just can't copy the board. There will surely be firmware involved.

    I'm not holding my breath but I won't be surprised when it surfaces.

  9. #29
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    And another shocker, as long as digital is discrete time sampling, which it will ALWAYS be as long as its clocked like a cpu or by logic gates have propogation times, it will always be discrete time steps per second, IE POINTS, and they will never go away, at least in my lifetime.

    If you do a fourier transform on any wave, it breaks down, first into more waves, and then into points, when you bin them.

    just cant get rid of those pesky points......

    Steve

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    I don't exactly follow what you mean. But I agree points will never go away since they are needed to define an image in the first place. But at the scanner level, the frame points could be thought of as control points. From there the "smart" scanner could interpolate between them to much smaller increments and finally they get filtered out all together. So, instead of the scanner operating from 30K (relatively) big steps it might be operating from 300K tiny steps. This would allow for better acceleration control or whatever.

    I'm not saying that's how it should work, though. I'm just throwing out some ideas. My point is that by placing more intelligence nearer to the galvos you can have much better control. And the likely way of interfacing to this "smarter" scanner is via a digital signal of some kind.

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