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Thread: Beams exist as cross

  1. #1
    Join Date
    Mar 2011

    Default Beams exist as cross


    Newbie question here. I have a chinese laser as my introduction to working with lasers (low cost, but still expensive for me)

    I noticed out of the red and blue prism cube, the beam exits as a sharp dot with a spilled cross shape?

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    This of course means some spill over at the galvos. I'm not after nor expecting perfection at this stage, but curious as to the problem here

  2. #2
    Bradfo69's Avatar
    Bradfo69 is offline Pending BST Forum Purchases: $47,127,283.53
    Join Date
    Jul 2010
    Wilmington, DE


    Welcome to the joy of red. Yes, you will likely be losing some power from spillover off the galvo mirrors. Usually in the cheaper chinese style lasers, the wavelength used is 650nm which, while an attractive color of red, also has the worst beam specs. It's also the least expensive to produce. While your greens and blues may come out the size of a pencil lead, the 650 red is often the diameter of the the whole damn pencil. The cross shape is because the beam is actually a little more rectangular than round and (I believe) it has to do with polarization. To get a nice tight red beam, you need to buy up to around the 640 or 660 nm wavelengths with the 640 being a little more orange and the 660 being a deeper, darker red. Both are much more expensive than 650.

    Keep asking questions! And welcome to PL. Lot's to learn here and lots of great people to learn from.

  3. #3
    Join Date
    Apr 2006
    Miami, FL


    yep, theres no problem, just the way it is... one of the lasers is vertically polarized, the other is horizontally polarized (so they can be combined with the PBS cube) so you get a + beam shape

    if you want to lose less power then you need galvos with bigger mirrors

  4. #4
    Join Date
    Oct 2010
    Athens, Greece


    maybe when you adjust the focus of the red modules the problem will become smaller?
    "its called character briggs..."

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