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Thread: Noob scanner questions.

  1. #1
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    Default Noob scanner questions.

    Hi there,

    We have recently bought a used 1000mw rgb laser from ebay, its a meirlight chinese unit and im quite impressed with it so far. It came with 30K scanners that worked well but we have now installed some 40K scanners from NRG lasers in manchester. With a bit of fiddleing we have aligned the diodes quite well, but the scanners need setting up properly and im not sure on a few things.

    1, When the scanners are spec'ed as 40k at 20 degrees, is this +/- 20 degrees or +/- 10 degrees?
    When i set the size in Quickshow to 50% x 50% (default) im getting 20 degrees (+/- 10 degrees) so when i set the size to 100% im getting 40 degrees from the laser (+/- 20 degrees)

    Is this normal? Im about to have a go at tuning the scanners so i really need to know what size to set it to.

    Also, is there any way to get quickshow to run faster than 30K? Or do i have to buy livepro or some other software to use scanning speeds faster than 30K?

    Many thanks.

    James

  2. #2
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    Jan 2006
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    Quote Originally Posted by timebomb View Post
    1, When the scanners are spec'ed as 40k at 20 degrees, is this +/- 20 degrees or +/- 10 degrees?
    Hi James;

    20 degrees means plus or minus 10 degrees. However, for very complex frames (read: most graphics frames), you will not be able to scan that wide. The accepted standard for a given point-speed rating (Kpps speed) is the ability to scan the ILDA test pattern at 8 degrees with no obvious artifacts at that speed.

    If you can get more than 8 degrees at a given speed with the pattern still looking good, that's a bonus. But if you can't get at least 8 degrees, then you can't meet the quality standard for that speed.

    My advice would be to reduce your scan speed to 30K and re-tune the scanners. At 30K, you'll get a wider scanning angle, which will come in handy when you're displaying graphics. (Most graphics are designed to be displayed at 30K anyway.)
    When i set the size in Quickshow to 50% x 50% (default) im getting 20 degrees (+/- 10 degrees) so when i set the size to 100% im getting 40 degrees from the laser (+/- 20 degrees) Is this normal?
    It is normal to be able to push the scanners beyond their rating? Yes. Is it a good idea? No. The quality of the image will suffer, and you can cause your scanners to overheat and burn out.

    Also, the scale (0-100%) in Quickshow does not correspond to your scanner's ability, but rather to the range of the output of the FB3 controller. There are other variables (including how the scanners are tuned, and where the input gain on the scanner amp is set at, as well as the quality of the scanners themselves) that will determine where on the size scale your scanners are capable of operating correctly.

    So how do you set your size in Quickshow correctly?

    First you need to figure out if your scanners are tuned correctly or not. Set your scan speed at 30K and display the ILDA test pattern with the size in Quickshow set to a very low level (say, 10%). Then look at the pattern. Is the circle completely round, or does it look like an oval? (If it's an oval, you need to re-tune your scanners.) Does it just barely touch the sides of the inner square, or does it protrude beyond it (or worse, is it so small it doesn't touch the square)? If it's not touching the square, you need to re-tune.

    Finally, look at the square itself. Do you see nice, bright dots at the corners with no signs of overshoot or undershoot? If not, then you need to re-tune.

    Once you've verified that your tuning is OK, then you can start increasing the size in Quickshow. When you see the center circle start to distort, STOP. This is the "safe" setting for size. At this setting or smaller, you should be able to display complex images without problems.

    Now measure your scan angle (here's a link to a handy table that will make it easier; just scroll down a bit). If you are at or above 8 degrees, congratulations! Your scanners are at least capable of 30K speeds. (And if you can go significantly above 8 degrees, say to 11 or 12 degrees, then they probably are capable of 40K speeds, even though it's best to continue to run them at 30K.)

    Now, even though this is the "safe" setting, most people recognize that nearly all of the images they display are far less demanding than the ILDA test pattern. Thus, they increase their size setting beyond this safe range so they can get a wider image.

    You can do that if you want, and you'll be able to get a wider scan field if you do, but you'll want to pay attention to what the image looks like when you're running with the larger scan field. If it starts to look really bad (distorted image, corners getting rounded off, etc), then you need to reduce your size setting.

    There is no hard and fast rule about how far past the "safe" setting you can go. Some people simply load up a typical graphics frame and then adjust the size up until the frame starts to distort a bit, and then they use that as their maximum setting. Just understand that the wider you go, the more load you're placing on the scanners. If they overheat, they can die.
    Im about to have a go at tuning the scanners so i really need to know what size to set it to.
    When you are tuning your scanners, the only thing that is important is that you are scanning at an angle that is SMALLER than the maximum angle the scanners can handle the test pattern at (for that speed). Many people make the mistake of setting the initial scan angle too wide. You can tune scanners just fine at 3 degrees, 5 degrees, or 8 degrees. But if you've got a set of scanners that are just a little bit off-spec, and maybe can only handle the ILDA test pattern at 7 degrees, then you'll have no end of trouble trying to tune them at 8 degrees, because you'll be chasing an imaginary target. (You'd already be beyond the capabilities of the scanners.) So if anything, set the scan size small.

    Have you read through my scanner tuning tutorial that is hosted on LaserShowParts.com? If not, have a look. It's quite helpful, especially if you've never tuned a set of scanners before. (The quick and dirty method used to set the initial size in the tutorial is to increase the size until the central circle distorts, and then to back it off a good bit from there. But that assumes the scanners are already fairly close. It won't work if your tuning is totally hosed...)
    is there any way to get quickshow to run faster than 30K? Or do i have to buy livepro or some other software to use scanning speeds faster than 30K?
    I believe Quickshow only allows a maximum of 30K scanning. And really, it's recommended to tune your scanners to 30K even if they can run faster. For example, I'm running the Scanpro 50 scanners in my projector, which are capable of running at up to 50Kpps speeds, but I still have them tuned for 30Kpps. This gives me a much wider scan angle (nearly 20 degrees on the ILDA test pattern, which is *really* impressive).

    I'm running the Pangolin LD-2000 system, and even though it is capable of much faster speeds, I still run everything at 30Kpps or less. (For some beam effects, I drop down to as low as 12Kpps.)

    Adam

  3. #3
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    WOW!!

    I wasnt expecting such a comprehensive reply.

    Huge thanks Adam, i think you have covered all the things i was unsure about.

    Ive got the mirrors pointing exactly fowards now, and X is X and Y is Y which it wasent before, ive got to make the X size match the Y size to start with then ill follow your advice and start at a lower scan angle.

    Thanks again

    James

  4. #4
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    Quote Originally Posted by timebomb View Post
    I wasnt expecting such a comprehensive reply.
    Hehe... I tend to suffer from a condition known as verbal diarrhea. I can't seem to shut up sometimes!
    Huge thanks Adam, i think you have covered all the things i was unsure about.
    Happy to help out dude...
    Ive got the mirrors pointing exactly forwards now
    Good. This is a step many people forget, and it will cause your image to be skewed one way or the other. True, you can correct for it in software if it supports geometric correction, but it's always better to get it right in the projector first.
    I've got to make the X size match the Y size to start with then ill follow your advice and start at a lower scan angle.
    To adjust the size of the pattern in X and Y, look on your scanner amps. There should be a potentiometer labeled "Input Gain". Note that this is *NOT* the same thing as servo gain. Servo gain is used for tuning, and it affects the speed of the scanner. Input gain, on the other hand, adjusts the absolute size of the image.

    So if you can find the input gain pots, adjust them until the X and Y sizes are equal. (You can display most any pattern while doing this, as long as it's got a perfect square in it. The ILDA test pattern works, but you can also use the Lasermedia test pattern, or even a quadrature square wave pattern.) Check the manual that came with your scanners and you should be able to figure out which pot is used to adjust the input gain.

    Adam

  5. #5
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    Thanks again Adam

    Ive got the input gains sorted, also now got the proper ILDA test frame (i was using the one in pangolin with the huge square arround it - struggling to get it big enough to see at 10% size)

    Ill start following your guide this evening, it got a bit late last night.

    Cheers.

    James

  6. #6
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    Oct 2010
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    HELP!!

    I was working through quite well, Was turning down the LFD on the Y axis and its just jumped into a complete mess!! Tryed winding it back to where it was before and its stays a mess, im worrying now, this isnt my laser it belongs to a friend and thease scanners cost him a lot.

    Any ideas Adam, i havent touched anything sine, i think the pot may have broken?

    Thanks

    James

  7. #7
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    Few!!

    Just turned it on again and its looking ok, quite a lot of undershoot on the y axis, i think thease trimmers are a bit naff, ive been getting odd flickers like the wipers not in proper contact.

    Cancel panic

    James

  8. #8
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    Sorry I missed the excitement, but it seems you've got it figured out.

    If you have a lot of undershoot, that can be one of two things:

    1) it can be too much LF damping. But you'll know that right away, because as soon as you reduce the LF damping even a little bit, you'll see the undershoot go away.

    2) it could mean you need some HF damping. This is harder to tell, but the way to be sure is again to reduce your LF damping a bit. If you start to see overshoot and you've still got undershoot, then you needed more HF damping. (Turn the LF damping back until the overshoot is gone, and then add enough HF damping to get rid of the undershoot and bring you back to a perfect dot.)

    Be careful with the HF damping. It's very easy to over-damp your scanners using the HF damping control. Most people add too much.

    Adam

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