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Thread: Far field alignment

  1. #11
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    Quote Originally Posted by JD3 View Post
    Same. I do give or take 30'. Then walk the distance with a piece of white paper in my hand checking alignment all the way back to aperture.
    Confused as if you set near field, then far field. The light is coherent it doesn't bend out. Hence why all the way back to aperture or are you not setting near field first. Also a black piece of anodized metal would prob have less scatter than a white paper.
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  2. #12
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    I do it as far away as possible but unless you do the alignment at each gig once rigged, I find that you will always get some movement from your 'perfect' settings due to transport shift, etc.
    If you get your nearfield alignment right (e.g. everything straight and parallel inside the projector) then the farfield sorts itself out, and you don't need to do the 'walkback' trick with the paper, because you know they all originate from the same spot on the scanner mirrors.
    I spend a lot of time getting nearfield right, which is why I like to use a mirror between each module and dichro if space allows.
    Hitting the exact same spot on each dichro with each colour is where you win or lose on the alignment stakes imho.
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  3. #13
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    Quote Originally Posted by polishedball View Post
    Confused as if you set near field, then far field. The light is coherent it doesn't bend out. Hence why all the way back to aperture or are you not setting near field first. Also a black piece of anodized metal would prob have less scatter than a white paper.
    I must be confused on the difference.
    Assuming my diodes are all aligned. I'm using the dichro's to adjust "far field".
    If at 30' they are all perfectly aligned (I project a square yellow, then white)

    Up closer they will be off a bit. It's strange, maybe poor build quality is having something come off at a slight angle?

  4. #14
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    Quote Originally Posted by norty303 View Post
    I do it as far away as possible but unless you do the alignment at each gig once rigged, I find that you will always get some movement from your 'perfect' settings due to transport shift, etc.
    If you get your nearfield alignment right (e.g. everything straight and parallel inside the projector) then the farfield sorts itself out, and you don't need to do the 'walkback' trick with the paper, because you know they all originate from the same spot on the scanner mirrors.
    I spend a lot of time getting nearfield right, which is why I like to use a mirror between each module and dichro if space allows.
    Hitting the exact same spot on each dichro with each colour is where you win or lose on the alignment stakes imho.
    Exactly my thought. If everything nearfield is perfect. Farfield should also be on
    Projecting the longer distance just gives you more "resolution" if you will. Ie don't have to look at such a tiny box to align

  5. #15
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    If you are aligned in the farfield, but they become unaligned nearer the projector, then they are not aligned in the nearfield.
    Your farfield alignment is simply the beams converging at the point you measure at. If you were to go further out, they would misalign again.

    You need to start by getting every beam bouncing off every dichro at the same point the other beam is passing through it. This may involve shimming (which is why I use primary bounce mirrors) and is a PITA.
    Once you have done this, you adjust the dichros so that the each point hits the first galvo mirro at the same point. A piece of black metal in front of the galvo block makes this easier.
    You may need to go back and adjust the individual modules at this point as raising the beam end at the galvo causes it to not be parallel to the other beams. Its a slow process of walking each one in.
    If you get this bit right, the farfield alignment should almost do itself, and only require a little bit of tweaking. If you need to move a lot, your nearfield alignment isn't good enough.

    See this pic to demonstrate what I mean by primary bounce mirrors. None on the red because this is the one all others align to (and no space! )

    Click image for larger version. 

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    The top down view gives quite a good indication of what I'm talking about actually. The blue is too far to the bottom of the picture, so the green doesn't pass through the centre of the blue beam. By adjusting the blue mirror I would bring the blue beam to the right as we view it, so it hits the dichro earlier, and centralised with the green. I would probably then need a very small tweak on the blue dichro to keep that on its original trajectory.
    A little haze in the room really helps see where the beams are in relation to each other
    Last edited by norty303; 10-29-2013 at 09:51.
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  6. #16
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    Quote Originally Posted by JD3 View Post
    I must be confused on the difference.
    Assuming my diodes are all aligned. I'm using the dichro's to adjust "far field".
    If at 30' they are all perfectly aligned (I project a square yellow, then white)

    Up closer they will be off a bit. It's strange, maybe poor build quality is having something come off at a slight angle?
    Since I typically come off as a jerk that is not my attempt, but this is projector building 101. EDIT looks like north covered it.
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  7. #17
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    Quote Originally Posted by polishedball View Post
    Since I typically come off as a jerk that is not my attempt, but this is projector building 101. EDIT looks like north covered it.
    Once you "get it" both theoretically and experientially, practice a few times, it becomes second nature. You can look at beams from above and the side near and far and go "yeah, blah is out". I see it in photos and videos all the time now!

    Once you do this a few hundred, thousand, zillion times like some here, your projectors align themselves while you sleep
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  8. #18
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    Attachment 40661

    Gotcha. I understand.
    My projectors have no bounce mirrors. But use a spring type stand off for the modules to Adjust them. The dichro's are a pain to adjust in this thing. But I have to work with what I've got.

  9. #19
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    Quote Originally Posted by dnar View Post
    Once you "get it" both theoretically and experientially, practice a few times, it becomes second nature. You can look at beams from above and the side near and far and go "yeah, blah is out". I see it in photos and videos all the time now!

    Once you do this a few hundred, thousand, zillion times like some here, your projectors align themselves while you sleep
    Yea I have aligned them ALOT. I understand importance of near field now.
    Last edited by JD3; 10-29-2013 at 13:07.

  10. #20
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    I agree with you.
    Last edited by Stephany5846; 08-31-2015 at 02:04.

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