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Thread: rotating mirror system for shifting a beam?

  1. #1
    Join Date
    Mar 2018
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    Default rotating mirror system for shifting a beam?

    I am looking for some mirror setup where rotation one or more elements in the mirror setup will allow to shift the beam along its axis.

    Two mirrors in a galvanometer scanner type setup work well for controlling the angle of the beam.

    Rotating risley prisms can be used to only offset the beam without changing its angle but the possible positions are limited.

    Dove prisms are great for rotating the beam along itself or rotate in a circular fashion if prism center is shifted.

    But as for offsetting (shifting) a beam along its axis from a (-1,-1) position to (1,1) without changing the angle of the beam, I can't find any setup which involves a rotating mirror rather than shifting mirror. But I feel there may be something missing from my limited optics knowledge.

    Some crazy 4 galvo setup may do this but that may be an overkill.

  2. #2
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    Why not three galvo mirrors?

  3. #3
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    Mar 2018
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    From what I know if you don't want to distort the beam profile by having mirrors at different angles you need two mirrors that will offset beam in one axis and cancel out each other's distortion and another set for the Y axis. Pretty much like having 2 glass slabs.
    With 3 rotating mirrors I don't know how you could do this.

    PS. I know I hadn't mention I need to not distort the beam profile but I had mentioned I need to achieve shifting without rotating the beam.

  4. #4
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    You're right, I wasn't thinking. Use two thick plates of glass in the beam. Tilt one at some big angle in one direction (to separate out extra reflections), and tilt the other in the orthogonal direction. Tilting them from that rest position translates the beam without affecting its angle.

  5. #5
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    Mar 2018
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    Such thick plates will be too hard to find, rotate mechanically for my 50mm shifting requirement. A 4 mirror setup can be used to mimick the same effect as 2 glass slabs but that is also not compact or elegant solution.

  6. #6
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    Mar 2018
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    Someone suggested to have telecentric lens or off-axis parabolic mirror after the galvo scanner to make the beams parallel. But he wasn't sure if these would work. Me neither as haven't used them before. Any ideas?
    Last edited by shoujin; 04-04-2018 at 05:21.

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