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Thread: A small laser with big problems

  1. #1
    Join Date
    Oct 2007
    Location
    Roman/NT/ROMANIA
    Posts
    10

    Default A small laser with big problems

    I've built a laser with the following components:
    -green laser module + power 50mW no-name
    -Laserworld scanner set LW-50K
    -Laserworld slave usb intreface
    -software HE-Laserscan III 3.4x
    -2 pc cooling fans + SMPS 12V\1,5A
    -blanking interface home made between +G signal and TTL laser connector.
    The settings are default for the software and for the galvos amplifiers. In the text mode i am pleased by the performances of the laser, but in the figure mode the problems appear. First of all i observed that through the Y mirror a small beam passes, altrough it doesn't have scratches. The biggest problem is that in complicated figures some lines become thin and dissappear. The software is very hard to use and to set. I cannot change the FPS number. The scanning angle is standard and it's like probably 15-20 degrees. With 7-8 kilo PPS the figures look better and the frame rate is too small and it's pulsing. At 25-30 kilo PPS the figures are continously, but some lines dissappear.
    I attach some pictures with the laser.
    2 movies on youtube with the laser:
    http://www.youtube.com/watch?v=rbYVGJ5I9iQ
    http://www.youtube.com/watch?v=x0zwnZ39IrQ
    The flicker it's from the camera(K800i 3.2MP).
    At the photo with the block of flats the blanking is not connected.
    The 4th picture is only a drawing with the 28k PPS from the software, it's not the ilda test pattern.
    Attached Thumbnails Attached Thumbnails DSC01567.JPG  

    DSC01568.JPG  

    DSC01571.JPG  

    DSC01634.JPG  

    DSC01602.JPG  

    Last edited by nenea dani; 04-06-2008 at 05:22.

  2. #2
    Join Date
    Jul 2007
    Location
    west sussex uk
    Posts
    2,279

    Default change the laser

    i have just fixed a simalar problem with mine my laser suffered from a jelly beaning problem and fixed mine by adjusting tec cooling you dont look like you have tec on yours ,so may have more trouble to fix its down to the laser its self not dealing with blanking at higher frequencys the internal crystals need to be at correct temp or they play up some one else may have another idea to fix it but i would change the laser for one with tec cooling
    regards
    chris

  3. #3
    Join Date
    Apr 2006
    Location
    Miami, FL
    Posts
    3,576

    Default

    looks like your laser dosent blank quickly enough...

  4. #4
    Join Date
    Oct 2007
    Location
    Roman/NT/ROMANIA
    Posts
    10

    Default

    I think i've understand what it's happening. After each blanking the laser diode needs some time to reach the normal intensity. If the scanning speed is too big the laser reaches the normal power too late. i think this is why the lines have the begining too thin. Am i right?

  5. #5

    Default

    Its a TTL head isnt it?

    looks ok there dani, a lot cheaper than a 5W from bucharest, buzz me on yahoo when you get time.




    Quote Originally Posted by nenea dani View Post
    I think i've understand what it's happening. After each blanking the laser diode needs some time to reach the normal intensity. If the scanning speed is too big the laser reaches the normal power too late. i think this is why the lines have the begining too thin. Am i right?

  6. #6
    Join Date
    Jan 2006
    Location
    Charleston, SC
    Posts
    2,147,488,211

    Default

    Quote Originally Posted by nenea dani View Post
    After each blanking the laser diode needs some time to reach the normal intensity. If the scanning speed is too big the laser reaches the normal power too late. i think this is why the lines have the begining too thin. Am i right?
    Yes, this is an accurate description of the "jellybeaning" problem. Basically the laser can't reach full power right away.

    You can play with the TEC circuit, as badger mentioned, or you may have to replace the laser entirely. All DPSS designs seem to suffer from this problem to one degree or another, but the cheaper brands are especially bad.

    Adam

  7. #7
    Join Date
    Oct 2007
    Location
    Roman/NT/ROMANIA
    Posts
    10

    Default

    My setup is just for testing , especially for evaluation of the scanners kit . I'll make some tests after wich i will decide if i'll construct another laser with a dpss tec perfomant or i'll buy one ready-built.

  8. #8

    Default

    Hi,

    It seems everyone has given you some idea of what the problem might be?

    I think you need to look at the X- axis scanner first of all, from the picture above it seems that the angle of the X- axis scanner is not correct. Just have a look as i have had it before that some of the image is cut short due to a wrong angle on one of the scanners.

    w.

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