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Thread: Large Apature Scanners

  1. #1
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    Default Large Apature Scanners

    I'm struggelling with a large beam diameter projector project that requires reduction telescopes to fit a DT20H 7mm apature scanner. Looking through scanner related threads and on Google/Ebay all the scanners are reviewed based on speed and angle, but aperture is not discussed. Any options? There are industrial scanners for marking/cutting from China that might be available for realistic prices, but the sites are thin. There is no discussion of available optics, amps ect.

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    The set of DT-20H's I've got are truly fantastic
    They piss all over the EMS 4000's I've got on a projector.

    What is the beam size and divergence you are struggling with?
    - There is no such word as "can't" -
    - 60% of the time it works every time -

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    I currently own a set of the DT20H scanners and they do/did work well(well one of the amps failed, but Marc at C.T. Laser is sending me a replacement). Any way, the beams are square 20mmx10mm arrays of multiple beamlets before compression and diverge at 2.1x0.7u rad. I would hate to triple this divergence.

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    Quote Originally Posted by planters View Post
    I currently own a set of the DT20H scanners and they do/did work well(well one of the amps failed, but Marc at C.T. Laser is sending me a replacement). Any way, the beams are square 20mmx10mm arrays of multiple beamlets before compression and diverge at 2.1x0.7u rad. I would hate to triple this divergence.
    <Thought Experiment>
    This is how I would plan to do it:

    "Fold the beam":
    Knife edge the beam in two; bounce one around to rotate the polarisation or just use a half wave plate. Combine using a PBS. That gives you a 10mm square beam so far so good.
    (Unless... you've got two of these modules and need the PBS for that!! )


    Then if you actually needed a smaller beam, use this (Edmund Optics NT47-911) and this (Edmund Optics NT47-344)

    That would increase the divergence by a factor of 1.4, but should bring the beam down to 7mm.

    Alternatively, if you really wanted to keep the 10mm beam, you could place an identical FL PCX lens either side of the scanner entry and exit, to "scan off a smaller diameter beam". (Just not on the waist!)

    </Thought Experiment>

    Either way... rock on!


    Edit: 2.1x 0.7Rad?
    Sure that's not "milli" Rad?

    If it is... what lenses have you got in there? There is scope to easily get that to 1.1x0.3mRad...

    I smell a very do-able 20W+ at 10x10mm with 1.5mRad on the horizon
    - There is no such word as "can't" -
    - 60% of the time it works every time -

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    Not bad! Take a look at the 20 diode module thread and let me pic your brain. Where would you suggest the fold? I like your idea, but an elegant solution/lay out isn't obvious. I'd like to avoid super complex zigzags. Final tweaking a 10mm square with a telescope is a lot more attractive. Now I have thought a lot about the sandwiched scanner idea, but there is never a free lunch. If it only meant that a scanner placed between the lenses could benefit from the smaller converging-diverging beam at the cost of a proportionally reduced scan angle then that would be OK, but I believe the swept beam would experience a varying power with angle. Am I wrong or am I right (or am I right and it is too small to matter)? And yes, it is millirad.

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    I'm going to threadjack a bit. I have some Cambridge 6850s I bought for a canceled Q-switched YAG conversion project.
    I have Cambridge amps for them. Data is here, and you can compare to the 6800 numbers if you want to. While not thought of as a "graphics" scanner, they certainly can handle large mirrors for beam effects.

    http://www.camtech.com/products/6800/6850p.html

    If you cannot fold your beam down, let me know, and I'll let them go at my cost, which was very affordable.

    Steve

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    Quote Originally Posted by danielbriggs View Post
    "Fold the beam":
    Knife edge the beam in two; bounce one around to rotate the polarisation
    i was thinking around these lines some time ago, but i could not get the polarisation change figured out just using mirrors. in fact i could not get the beam back to the pbs without "suffering" another polarisation change...

    this should be the general idea, rite?

    "its called character briggs..."

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    Quote Originally Posted by LaNeK779 View Post
    i was thinking around these lines some time ago, but i could not get the polarisation change figured out just using mirrors. in fact i could not get the beam back to the pbs without "suffering" another polarisation change...

    this should be the general idea, rite?
    Close, but no cigar - you are only bouncing the beam around, not changing the polarization.

    The beam has to be rotated 90 deg - to do this you will have to send the beam not only horizontal, but also vertical.

    Andy_con has made a nice example in his Arctos tribute: Link

    /Thomas

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    sorry,i forgot to mention that there is a waveplate somewhere in there, (the only line that is not at 45 degrees)

    what i find difficult to imagine is how one can recombine the beams without re-changing the polarisation if you start from the same beam height.
    andy has two seperate beams at different heights
    "its called character briggs..."

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    Quote Originally Posted by LaNeK779 View Post
    sorry,i forgot to mention that there is a waveplate somewhere in there, (the only line that is not at 45 degrees)

    what i find difficult to imagine is how one can recombine the beams without re-changing the polarisation if you start from the same beam height.
    andy has two seperate beams at different heights
    Ah sorry, missed that...

    This illustrates what Andy has done:
    Click image for larger version. 

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    The lower mirror could be set to another angle to raise the beam again, and hit a third mirror.

    /Thomas

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