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Thread: Using a prism instead of multiple dicroics?

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    Default Using a prism instead of multiple dicroics?

    Just a thought that occurred while I was puzzling over the possibilities of a 405/445/457/532/640/660 rig for getting the best out of lumia and grating effects and was wondering how to combine the beams:

    We all use some mix of PBS/Dicro for combining multiple laser sources, but why not use a prism?
    Alignment has a bit of a pain in the arse feel to it (angle and position matter) but the win is that a good quality coated prism will put 2 surfaces in the beam (plus whatever mirrors you need to get the beams into it correctly), where dicros and PBS put at least 4 and possibly 8 or more if doing the above.

    Has anyone tried this approach to beam combining?

    Regards, Dan.

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    mixedgas is offline Creaky Old Award Winning Bastard Technologist
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    Yes, prisms have been used in the past for split and recombine color control.

    Big baseplate required, probably, otherwise with a good prism and a proper prism table mount, no problem.

    I have some drawings some where of neat prism tricks, some involving AOs or Galvos. No promises I can find them.

    Steve

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    Quote Originally Posted by DMills View Post
    Just a thought that occurred while I was puzzling over the possibilities of a 405/445/457/532/640/660 rig for getting the best out of lumia and grating effects and was wondering how to combine the beams:...
    where dicros and PBS put at least 4 and possibly 8 or more if doing the above.

    Has anyone tried this approach to beam combining?

    Regards, Dan.

    I only count one surface for dichro reflect and two surfaces for both PBS and dichro transmit (for each beam same as a prism) but with the advantage that angles are 90 degrees which makes steering easy.

    The fact that they are the same surface for many beams does not reduce the effective surface count for each beam and makes physical alignment a real pig, unless as Steve says you have a really big optics table.

    You can get approx 90 degree angle from a prism which helps with the steering a bit but you still need the approach beams in the right place as well as traveling in the right direction.

    Cheers

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    Given the fact that dispersion in a prism is wavelength dependent, drift in wavelenght will translate in an angular drift. This works for separating as well as for combining.
    Wavelength of red laserdiodes is die-temperature dependent, something around 0,5nm/degC. The prism material and orientation will be optimised for maximum dispersion to make combing feasible.
    This may result in problems in the far field alignment. I predict a drift in the mrad-range if the temperature of the diodes is not properly stabilised.

    The spectrum spread of multiple-blue-diode modules will likely pose insurmountable problems when shooting through a prism.
    Last edited by -bart-; 02-15-2011 at 04:52.

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    Medialas used to do this in their early RGB lasers

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    Quote Originally Posted by DMills View Post
    Just a thought that occurred while I was puzzling over the possibilities of a 405/445/457/532/640/660 rig for getting the best out of lumia and grating effects and was wondering how to combine the beams:

    We all use some mix of PBS/Dicro for combining multiple laser sources, but why not use a prism?
    Alignment has a bit of a pain in the arse feel to it (angle and position matter) but the win is that a good quality coated prism will put 2 surfaces in the beam (plus whatever mirrors you need to get the beams into it correctly), where dicros and PBS put at least 4 and possibly 8 or more if doing the above.

    Has anyone tried this approach to beam combining?

    Regards, Dan.
    for the grating effects i could see you wanting the beams on top of each other...for lumia, i dont see why it would matter. But yes, as others said, no problem if your table is big enough. I wouldnt be concerned about drift...its a lumia projector....everything is moving
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