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Thread: Do your lasers "move"???

  1. #1
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    Default Do your lasers "move"???

    this question applies to pretty much anyone on here with a laser, but I think people with full color (RGB) systems will be able to answer better,

    I have a RGB set and I noticed that my lasers "move".

    For example, I will align all three beams perfectly (good, clean white dot at a good distance). After about 30 minutes of doing various effects, I'll project that same white dot and I notice that the beams have moved relative to each other.

    Its not much, but being the perfectionist that I am, I have to move my MM1's til I get a good clean white dot again.

    Is this due to heat? (ie. is the heat of the lasers heating the dichros and/or mounts to the point where they move slightly?)

    Is there something in the laser module itself that cause them to shift under heat? Nothing physically moves relative to the projector box so I definetely dont think its anything vibrating loose.

    Again, we aren't talking about much, (maybe an inch over 50ft) but to a perfectionist trying to get a clean, white beam it makes a difference.

    Anyone else experience this??

    -MO-

  2. #2
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    Default

    I haven't gotten my RGB set up but should have it in a few days to a week. If I have this issue I'll post a report here for ya. Sounds like you scanners might be putting off a harmonic just low enough to move a filter. Somethin I doubt you could pick up on audibly or visually until it had move a beam. Do you have to re-align all the filters or just one?
    Love, peace, and grease,

    allthat... aka: aaron@pangolin

  3. #3
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    Default

    I tested the beams tonight and I ruled out the scanners being a factor.

    I basically just projected all the aligned beams without moving the scanners at all, no effects. I noticed that all the beams move somewhat in the same direction (to the left) but only a small distance.

    Could it be that the dichros all heat up and warp slightly in the same manner? They are good quality (edmund optics).

    -MO-

  4. #4
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    Maybe something with the mounts collecting heat and ecpanding a lil. I'm guessing here. I don't even have optics yet... ops: Next paycheck... I doubt the optics would "warp"... What would be affected by heat first, metal or optics?

  5. #5
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    Default

    What are you using for the optic table?
    It may be a problem with that.
    Once you realign them after the 1st half hour do they drift again?

    Jim

  6. #6
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    Sure sounds like a thermal problem. Something heating up and bending ever so slightly. Could be the baseplate, but my guess is it's one of the mounts. Jim has the right idea though. Let it warm up, then align it. If it doesn't drift after that, then you know it's thermal...

    Adam

  7. #7
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    Default

    When i had the Isssue with my projector, it was because my baseplate was too tight into my case and when it heated up it expanded and warped a bit to move the beam.. BUT on different effect. As the lasers heat up, the beam does move ever so slightly. At a distance of 150 ft i have noticed that a beam can move an inch or so over a 1 hr period....
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  8. #8
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    I think lasers do drift slightly with time. It's called beam stability or drift or something like that , :roll: . I think it happens due to thermal shifting of the optical components inside the laser. This drift is not much though. It's supposed to be less than 0.1mrad per hour. At least that's what is advertised on some modules :P

    As already stated, might also be a problem with the base heating and bending with time.
    Remember the future?, That'd today, as you imagined it yesterday.

  9. #9
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    I have to agree; there is no reason that any optics should move, unless the base that the optics are mounted on is heating up too (which may be the case inside the laser, pushing around the crystals). Keep in mind that copper and aluminum have rather noticeable coefficients of expansion, and isn't surprising that with this level of accuracy you need, there will be drifting, both inside the laser and between the module and mounting surface. If you can, try using a steel mounting surface too; it's coefficient is less than half of aluminums, and will not move as much under the same temperature. Just make sure you can lift it :P

    Otherwise, I have to agree with the others who said just to align it after the system has warmed up.

  10. #10
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    Well... :roll: Did you fix it? :?

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