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Thread: Split Beam Problem

  1. #1
    Join Date
    Feb 2005
    Location
    Southampton, UK
    Posts
    166

    Default Split Beam Problem

    I am having a problem with a module I am experimenting with. It is a Lead Light 110, and it puts close to 500ma into the diode (too much I know).

    The problem I have is that with the latest mod, the beam splits into 2 parallel beams, but it seems stable (to a madman). If I remove the mod the beam slowly returns to normal (both beams get dimmer then "snap" back to a single beam.

    I belive that this behaviour is in the MCA, but is it simply because the crystal is being overdriven or is it a personailty of this particular MCA ?

    I have not tried a realignment yet, whats your opinion ?

    Gold

  2. #2

    Default

    welcome to the wide world of mode hopping. TEM00 to TEM02

    I get the same thing when I press down on the bore of one of the smaller HENE's here.

    the crystal should not introduce hopping, sounds like the diode is freaking out in new and interesting ways.

    Would love to see a video of this phenomenon.

  3. #3
    Join Date
    Jan 2005
    Location
    lancaster Pa. USA
    Posts
    130

    Default

    i had a greenie(not a leadlight) that if i shook it, the beam would spawn a smaller offshoot. on that one i think it was crystal or optic misalignment.
    Those who stand for nothing, Will fall for anything.

  4. #4
    Join Date
    Feb 2005
    Location
    Southampton, UK
    Posts
    166

    Default

    OK Spec, today is not the best day but after a really bad day at work I had 20 minutes to set up and reproduce the splitting effect.

    I have to appologise about the quality of the images, this weekend I am going to set up a high res camera with a controllerable shutter so I can get some "realistic shots". At the moment I am using i-Catcher CCTV software with a webcam.......

    Now for some background, the module is a leadlight 110, with 2 resistor mods. I think we all have a module like this, about 3 months ago it died, and I put it in the bit bucket. Last week I hooked it up to a bench PSU and it came to life, I used it to to take images for my crystal mixing experimentation. If you follow lasermods experiences of the 110 you will note that he posted a correction to a resistor mod, well I ended up modding both the correct and incorrect components, this is when I thought the unit had died.

    Following is resurection (NO not a Pheonix?) I tried Wyverns shot of the cap A106 this is when the beam splitting started.

    This is a link to a shot video of a split/hop

    http://www.rav89.dial.pipex.com/lasers/split.avi

    If you download it it should play in media player.

    I am also posting the following frames of a "hop"



    I am about to short the cap.



    After a short time the beam splits perfectly into 2 parallel beams





    After the A106 cap short is removed the beam snaps back after about half a second. I was going to bin this unit but now the plan is to play with it more. I was going to put the latest mod on a toggle switch so I could easily add and remove these strange effects.

    Whats it good for ?

    How can I play with it ?

    Gold

  5. #5
    Join Date
    Feb 2005
    Location
    Florida
    Posts
    802

    Default

    Wow...Free Effects

    I want my laser to do that :?
    "My signature has been taken, so Insert another here"
    http://repairfaq.ece.drexel.edu/sam/laserfaq.htm
    *^_^* aka PhiloUHF

  6. #6
    Join Date
    Feb 2005
    Location
    Florida
    Posts
    802

    Default

    Just kiddin Gold

    Do you have your module "heatsinked" ?

    May be temperature related...sounds like the diode is "Not Happy"
    "My signature has been taken, so Insert another here"
    http://repairfaq.ece.drexel.edu/sam/laserfaq.htm
    *^_^* aka PhiloUHF

  7. #7
    Join Date
    Feb 2005
    Location
    Southampton, UK
    Posts
    166

    Default

    It does sit in a heatsink, BUT it has been running 24 hours a day for 3 days into a crystal (quartz varity). This said it is running at about 120ma and that only just gets it going.

    To get the effects I set the voltage to 3.5 volts and short the cap, put on some pink floyd and relax. Once the beam has split the "dots" seems very....fluid, it (they) seems to change shape slightly in a liquid type fasion.

    If I get the time to set up the new camera then I can get some decent shots this weekend. I will try and get a high frame rate avi to show the beam in detail, including looking towards the module.

    Gold

  8. #8

    Default

    3.5V is a bit hot for the circuit.

    Looks like you are also introducing nasties in the form of ripples, the caps might simply be for eddy current/ripple protection to and from the diode.

    Its a modern marvel that it is not completely dead...

    Interesting "problem" you have there. I will take a video in a couple moments of my hene laser doing the exact same thing when I do the equivalent of "beating up the emitter"

    gimme a little bit, hopefully I can get this to show up right.

  9. #9
    Join Date
    Feb 2005
    Location
    TX
    Posts
    29

    Default

    i've also had this problem with a modded 105. after I did the diode alighnment mod(i already had a resistor mod) it started splitting. Mine starts out cold with 2 beams, then after 20 secs of warming up it snaps into 1, or if I just click the button again it snaps into 1.

  10. #10

    Default

    as promised:

    The "mode hop" video.

    http://www.photonlexicon.com/hostedcontent/modehop.avi

    It was recorded at 30fps, however I cut the frame rate to 15fps to slow it down so you could get an idea of the "liquid transitional period" involved.

    the video started out at 30 megs raw mpeg but i managed to slap it into a 1.2meg xvid/divx file. there is enough grain in the video to annoy me, but it gets the point across.

    Tell me what you think.

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