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Thread: Green dim on certain images..

  1. #1
    Join Date
    Jan 2007
    Location
    Anaheim, CA
    Posts
    387

    Default Green dim on certain images..

    When I'm scanning an image and it is all white, the white looks "whiter" than when I'm scanning an image with white and other colors. When I am using other colors, the green is much more dim, making the white look more magenta.. I'm guessing this a problem with the modulation, and it's not getting to high enough power soon enough. I am using the Flexmod 3 for all of lasers in the projector.

    For instance, If I wanted to scan this image:

    http://img388.imageshack.us/img388/4271/hpim1607cb3.jpg but in pure white, the white would look pretty white

    but If I try and scan this image:

    http://www.laserist.org/ldi2007/imag...Test_1024w.jpg the white part looks magenta, and the green "O" is dim and sometimes flickers..

    Note: Those are not my images, just there for reference..

    Also, in Quickshow there is an option for Analog with Log Response and Analog with Linear Response.. not sure which one I should choose.
    - instinct

  2. #2
    Join Date
    Sep 2006
    Location
    Netherlands
    Posts
    1,435

    Default

    It's called blanking induced dimming. It's caused by thermal issues in the doubling crystal.
    If you search the forums for modulating dpss it will give you more in dept info.
    There's no real cure for it except running your dpss continuous wave and adding an AOM.

    Also, in Quickshow there is an option for Analog with Log Response and Analog with Linear Response.. not sure which one I should choose.
    Choose this test pattern:
    --------------
    OOOOOOOOOO
    --------------
    Choose the response that gives you the best linear gradient.

  3. #3
    Join Date
    Jun 2007
    Location
    Lake Geneva, WI.
    Posts
    2,704

    Default

    I've dealt with this by controlling the temp of my laser heads inside of my projector. Using a fan controller, I allow the laser heads to hover between 85 and 80 degrees F. This seems to alleviate my low power, noise and mode hopping problems very well.

  4. #4
    Join Date
    Nov 2007
    Location
    Cairns, Australia
    Posts
    1,896

    Default

    It can also be caused by some images being scanned much faster than others. You'll find if you scan something much slower it'll be brighter.

    But since you mention flickering, it's definitely a modulation problem. Very common in pretty much all DPSS lasers.

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