Page 1 of 2 12 LastLast
Results 1 to 10 of 19

Thread: Time to Blank

  1. #1
    Join Date
    Aug 2007
    Location
    Portland
    Posts
    1,354

    Default Time to Blank

    Hey all,

    Last year I finally installed some DT40s on my laser and I'm very happy with the results so far. My next step, besides tuning my collimator on my DPSS is achieving adequate blanking. My laser (Melles Griot GSD-series) only has 40Hz TTL, so that's out the window.

    Assuming I can fit a third galvo in the path of the beam, (which I can -one way or another), what would you recommend as far as hardware to do this?

    I have a pair of GM20s, but I have a feeling one of those won't cut it. Additionally, I 'd need to get or build something to control one of those. Should I opt for another DT40 and amp?

    My DAC is an FB3 and I'm using a 3 watt, 532nm laser. The GM20s have mirrors on them and were originally installed on my laser system.

    -Jonathan

  2. #2
    Join Date
    May 2006
    Location
    Native Floridian
    Posts
    3,127

    Default

    Quote Originally Posted by platinum View Post
    Hey all,

    Last year I finally installed some DT40s on my laser and I'm very happy with the results so far. My next step, besides tuning my collimator on my DPSS is achieving adequate blanking. My laser (Melles Griot GSD-series) only has 40Hz TTL, so that's out the window.

    Assuming I can fit a third galvo in the path of the beam, (which I can -one way or another), what would you recommend as far as hardware to do this?

    I have a pair of GM20s, but I have a feeling one of those won't cut it. Additionally, I 'd need to get or build something to control one of those. Should I opt for another DT40 and amp?

    My DAC is an FB3 and I'm using a 3 watt, 532nm laser. The GM20s have mirrors on them and were originally installed on my laser system.

    -Jonathan
    Well, you have several options to choose from. You can use flag blanking, which is very easy to implement, however, it is your slowest option. The second option, is optical leverage blanking. Sorta hard to explain in text, see photo below. It is about as fast as you can get without going AOM. Which is your last option. If you can find a nice AOM, then you can get full analog blanking, which is by far the best way to go. The downside to the AOM is that you can expect to loose a significant percentage of that 3W. The upside, is you can use the waiste beam for other effects such as diffraction and lumia.

    Flag Blanking-------Very Slow----0% light loss
    Optical Leverage---some loss of light, challenging to align----Very fast
    AOM---Difficult to align, substantial loss of light---Very fast, capable of analog
    Attached Thumbnails Attached Thumbnails scanhead.jpg  

    Cap0053.JPG  


  3. #3
    Join Date
    Feb 2005
    Posts
    1,131

    Default

    AOM!
    min. power loss fast blanking for graphics

  4. #4
    Join Date
    Jan 2006
    Location
    Akron, Ohio USA
    Posts
    1,754

    Default

    I got real lucky and got a nice bunch of laser gear all at once. I did have to figure out how to align it by myself, but that was a lot of fun! I have always wondered what is really going on inside the PCAOM crystal. How does it really work to fade the beam?

    James.

  5. #5
    Join Date
    Feb 2005
    Posts
    1,131

    Default

    To fade the beam that is done by the intensity of the soundwave

  6. #6
    Join Date
    Oct 2006
    Location
    Central Florida
    Posts
    7,067

    Lightbulb

    David,
    I got a nice AOM out of a grocery store scanner that I need your help in hooking up. If it won't work on the blue, it should on the 130mW ttl maxyz I got. Maybe a quick project at SELEM.

    To be honest, I am about ready to go all AOM or PCAOM on the DPSS just so everything will blank togther. F the loss...
    Love, peace, and grease,

    allthat... aka: aaron@pangolin

  7. #7
    Join Date
    Aug 2007
    Location
    Portland
    Posts
    1,354

    Default

    The AOM option will probably have to wait for now. I feel that would be considerably pricey compared to the other two options. As far as flag blanking and optical leverage.. the keep-it-simple side of me says go with flag blanking. I have limited space to work with as I am working with a Mobolazer platform. The DT40s are mounted (rather extravagantly) over one of the 10 apertures on the unit.

    I decided to keep the Mobo option for mirror effects and wide-coverage capability. There's not too much room in between the aperture and the scanners, but I figure I could mount something the size of a GM20 in the path of the beam. I suppose if I was really crazy I might be able to blank the master beam before it goes into the servo array. This might make for interesting effects with the stationary beams somehow.

    Anyway, I'm unclear as yet, whether a GM20 could cut it as a blanking device. Am I right to assume it's too slow? Or am I not giving the old things enough credit?

    Attached are two pictures for illustration of what I have to work with:
    Attached Thumbnails Attached Thumbnails DT40Mobo.JPG  

    DT40Mobo2.jpg  


  8. #8
    Join Date
    Apr 2007
    Location
    Toronto Canada
    Posts
    1,120

    Default

    Quote Originally Posted by James Lehman View Post
    I got real lucky and got a nice bunch of laser gear all at once. I did have to figure out how to align it by myself, but that was a lot of fun! I have always wondered what is really going on inside the PCAOM crystal. How does it really work to fade the beam?

    James.
    Acousto Optic. Piezoelectric element that sends acoustic waves trough the crystal.

    An acousto-optic modulator consists of a piezoelectric transducer which creates sound waves in a material like glass or quartz. A light beam is diffracted into several orders. By vibrating the material with a pure sinusoid and tilting the AOM so the light is reflected from the flat sound waves into the first diffraction order, up to 90% deflection efficiency can be achieved.
    http://en.wikipedia.org/wiki/Acousto-optic_modulator
    I hired an Italian guy to do my wires. Now they look like spaghetti!

  9. #9
    Join Date
    May 2006
    Location
    Native Floridian
    Posts
    3,127

    Default

    Quote Originally Posted by allthatwhichis View Post
    David,
    I got a nice AOM out of a grocery store scanner that I need your help in hooking up. If it won't work on the blue, it should on the 130mW ttl maxyz I got. Maybe a quick project at SELEM.

    To be honest, I am about ready to go all AOM or PCAOM on the DPSS just so everything will blank togther. F the loss...
    Hey Aaron, I'd be glad to help get the AOM going at SELEM, though I probably wont have all the tools I may need. If you like, you can still send your stuff to me and I can fix it up here in Jax before SELEM. Either way, its up to you.

    Anyway, I'm unclear as yet, whether a GM20 could cut it as a blanking device. Am I right to assume it's too slow? Or am I not giving the old things enough credit?
    I'm not sure how well a GM20 would work for flag blanking, I think it would be very slow. I've never tried flag blanking with a dt-40, but that may be the best bet. Just rip the mirror off and replace it with a thin piece of metal, I use to cut apart the metal piece on diskettes to use for flag blanking. One other thought, what ever piece of metal you use, you may want to leave it shiny, if you paint it black, it will try to absorb alot of that 3W and may quickly overheat the scanner.

  10. #10
    mixedgas's Avatar
    mixedgas is offline Creaky Old Award Winning Bastard Technologist
    Infinitus Excellentia Ion Laser Dominatus
    Join Date
    May 2007
    Location
    A lab with some dripping water on the floor.
    Posts
    9,890

    Default

    check the polarization of your laser, if it is random, use a galvo and flag or figure 4 leverage
    like in that posted photo. If it is polarized, use a AOM. AOMs are not the difficult witchs they are made out to be. Most modern chinese stuff is polarized as they use YVo4 and not yag.

    Steve Roberts

Posting Permissions

  • You may not post new threads
  • You may not post replies
  • You may not post attachments
  • You may not edit your posts
  •