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Thread: Small oscillations in my scanner

  1. #11
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    I have to go with the doctor on this one. I have seen a similar effect before on a set of CTI 6210's . They were being driven too hard on a large angle grid pattern . The top few lines showed a " sine wave " pattern on straight horizontal lines. De-tuning a little solved it.

    Either that or , do you live on the Pacific rim ?

    Regards

    Fluff
    The light at the end of the tunnel. Its' a white laser.
    www.rocknite.co.uk

  2. #12
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    There is only one power supply for both so I don't think that could be it. But, as I said above, some additional tuning got rid of them for the most part. I am going to mess with tuning a bit more and see how that goes before I do anything else.

  3. #13
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    Yes, again, detuning seemed to get rid of them mostly but now there is another problem that resulted. I will post a picture next time I can. But basically, now there are little "tails" on the very left. Kind of like Nike swoops.

  4. #14
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    Quote Originally Posted by carmangary View Post
    After I did that I did the sine pattern again and the oscillations are all but gone.
    Ok, so the tunning help, from your statement I thought you still had the same problem......?

    werner

  5. #15
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    This one could be a bugger to track down. Do you have a scope? if so look at the output from your dac. If you don't swap the x and y inputs going to the scan amps and make sure there isn't anything wrong with your output. If that is fine and you have swapped the scanners and drivers and it follows the x card then there is probably something wrong with the x driver.
    It looks like left side exhibits the problem more (could be just me). if it is more pronounced on one side there could be something wrong with an ic in either the -/+ rail, hence the worse output on one half.

    Does it do it at rest? In other words does it do it if you are just projection a dot? Do you have a dc bias that you can use to just steer a dot to the left? Does it get worse the further left you go?

    Chad


    When the going gets weird, the weird turn pro.


  6. #16
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    Quote Originally Posted by carmangary View Post
    Yes, again, detuning seemed to get rid of them mostly but now there is another problem that resulted. I will post a picture next time I can. But basically, now there are little "tails" on the very left. Kind of like Nike swoops.
    Try altering the blanking shift figure in your software projector settings.

    Fluff
    The light at the end of the tunnel. Its' a white laser.
    www.rocknite.co.uk

  7. #17
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    Here's a possible solution, though perhaps not the most practical one:

    COME TO SELEM 2007 in Newton, NC! Then you can have Bill Benner and Steve Robers both look at your galvos and give you their expert opinions. (And if it turns out to be a tuning issue, not only will they tune it for you, but will show you how to do it yourself in the future!)

    OK, I realize you're in Texas so it would be a 1200 + mile trip, but you gotta admit that there's a part of you that wants to go!

    Adam

  8. #18
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    Actually, it would be fun to go to Newton, NC since I used to live only a few miles from there as a kid. It would be fun to see how the place has changed and to get to meet some laser professionals. But, unfortunately I won't be able to make it. I'm still wondering how Newton was picked, of all places.

  9. #19
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    Quote Originally Posted by carmangary View Post
    It depends on the image I am scanning and what my scan rate is.
    This is normal for cheap chinese scanners.
    It is a mirror resonance.
    Chinese galvos are normally supplied with too thin mirrors (about 0.5 mm).
    This causes strong resonances at some scan frequencies and their harmonics.

    If one of the mirrors is not properly aligned to the center of the shaft, this resonance could be even stronger than at a proper aligned mirror.

    Another source could be a bad cable.
    I have seen lots of chinese cables, where the shields of the PD-sensor and motor were changed.
    Also a bad or missing grounding could increase the effect of resonance.

    So first check the cables (by changing them).
    If the resonance is still there, check if the body of the galvo is grounded.
    If the resonance is still there, slow down your driver.
    If the resonance is still there, change the mirror (if possible).
    If the resonance is still there, buy better scanners.

    Joachim
    Producer of EasyLase USB and NetLase
    Lasershow software DYNAMICS

  10. #20
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    Quote Originally Posted by carmangary View Post
    I'm still wondering how Newton was picked, of all places.
    That's simple... It's the only North Carolina venue we could find that had 3 phase power, water for cooling, would allow lasers and fog machines, was within our budget, and was available on such short notice. We had another venue all set up in North Carolina, but that whole plan fell apart about a month ago so we really had to scramble... (Didn't want to change the location too much since people were already making travel plans.) Fortunately the Newton Connover Civic and Performance Place was willing to work with us!

    I didn't know you used to live near there... Damn - small world eh? Depending on how it goes this time, we may try to do another event there next year, so you may still get a chance to check out your old stomping ground...

    Adam

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