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Thread: Dichro Adjustment

  1. #1
    Join Date
    Jul 2006
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    Connecticut, USA
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    Default Dichro Adjustment

    Im having some issues here. i have posted many photos, lets see if you guys can give me some advice. i read a lot of the tutorials from here on properly aligning your lasers. i actually have 2 of the tutorials hanging on my wall in front of me. but im still having some issues.

    granted, nothing is really locked down right now, but it still looks WAAAAY off after some long time attempting to "Poor man" align. the dot on the wall (approx 15-20 feet) is a nice white, but the beam is TERRIBLE. you can just tell its a red green and blue beam overlapping. meaning, the colors arent "meshing." is this still an alignment issue?

    i will apologize in advance for the double posts with photos, i took about 20 pics for you guys to take a look at....

    -Marc
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  2. #2
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    Default

    more pictures-
    crap i need more text for it to submit...
    lol...
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  3. #3
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    Default

    and more pictures. how many words is the minimum? oy vey!!!
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  4. #4
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    Default

    and heres the last ones.
    sorry so many. wanted to make sure all angles were covered.
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  5. #5
    Join Date
    May 2007
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    Milwaukee WI
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    Default

    Yeah you need to re-align...

    You have to make sure that all the beams hit the dichros at the same point. Because what is happening is your near and far field alignment are not the same. Its difficult to get right, but trust me you can do it.

    I would drill a hole in the breadboard. Take a look at the pictures I posted recently in the thread I started regarding the building of my projector (to find it you can search for "planning building RGB" and its the one with like 7 or 8 pages)

    In that thread I have a close-up of a dichro combining a red and green. Its difficult because they line up because the red beam is larger (just like yours). The reason why the spot looks fine is because the beam is overwhelming to your eyes in a sense...

    The way I aligned my projector - is I have the beam hitting a mirror right after exiting the projector. It reflects to another mirror about 22 feet away and reflects back to the same wall the first mirror is on. This way you have a near field and a far field alignment all within a few feet of the projector. Makes it easier on you...

    Anyway - I need to stop writing I am still at work... Hopefully I will be able to contribute more soon, but in the mean time hopefully this'll help...

    -Max

  6. #6
    Join Date
    Oct 2006
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    Central Florida
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    Lightbulb

    Loookd like you nrrf to move the blue... make it hit the dichro right where the green/red is. They look fairly good in the pictures, just looks like the blue is off. Raise it up also. Rob/stanwax has a nice alignment tutorial also.
    Love, peace, and grease,

    allthat... aka: aaron@pangolin

  7. #7
    Join Date
    Jun 2007
    Location
    Monroe, Mi USA
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    812

    Default Move the mount

    Marc,

    I was rambling on about this in a recent reply..." Flexibillity...Projector 101"...I have currently been thinking that it would be the least hassle to move the Dichro mount to the x/y point where the beams intersect AND hit the dichro surface...this then will " stack" the beam profiles atop one another. There is a location where these conditions exist....and....Schizaam !!! there it is !! This assumes that the beam elevations are allready in alignment !!!...But...that is what the Floating Platforms provide !!
    It looks to me that the Green is allready centered inside the Red....but that your Blue is shifted to the left....so that is the one that needs to be further dialed in. IMNSHO.
    Question...How did you get such great beam pics ?????? the beam looks like a solid rod !!! mmmm ??? Camera on tripod.....several second exposure times ???... Magic ?? Thanx !

    BoB/CDBEAM

    Edit: ATWI was typing while little whisps of smoke were cummin from my ears.....But....He does not have a dog that spends hours in basement lab with him...patiently looking for her next "K9 Coherent fix"
    Last edited by CDBEAM; 04-08-2008 at 22:35. Reason: " Missed it by that much !"
    Beam Axiom #1 ~The Quantum well is DEEP ! Photons for ALL !!
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    Beam Axiom #3 ~Whe'n dout...Po ah Donk awn et !!
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  8. #8
    Join Date
    May 2007
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    Default

    Ok so here is one of the benefits to having 3 axis mounts over 2 axis. If you had three axis mounts you could easily turn all three knobs clockwise pushing the dichro diagonally towards the laser which would cause the beam to hit the dichro closer to the aperture which in turn would solve your problem pretty easily.

  9. #9
    Join Date
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    Charleston, SC
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    Cool

    Sorry I missed your call last night, Marc... I crashed kinda early and slept right through your message.

    All the advice above is right on the money, though. Your near-field alignment is off. The near field alignment is basically how closely the beams overlap when they hit the dichro. This *absolutely* has to be correct, or else you'll never get your far-field alignment correct.

    The idea of sliding the dichro along the baseplate is a good one. (Especially if you don't have any movement available in your laser mounts.) I have my dichros mounted on MM2's, and the bases of those mounts have a 1 inch long slot cut in them so they can slide and pivot on the baseplate. That makes it easy to get the dichro face to exactly the right plane.

    As mentioned above, the beams must overlap *perfectly* at the dichro face. In the case of your large-beam red, you need to be certain that the dot from your green laser is exactly centered inside the much larger dot from your red.

    Once you have the dichro aligned correctly so your near-field alignment is OK, then you adjust your far field. (Forget about blue for now. You need to dial in the red-green mix first!) Tweak the adjustment screws on the dichro until the red and green beams *stay* aligned even at a distance of 20-30 ft away from the projector.

    If you've nailed your near-field alignment, then the far field alignment is easy. But if you're even a little bit off on the near field, then you'll have trouble getting the far field correct. (A longer throw is better, because it will magnify any alignment error.) Also, be sure to check the far field alignment at several different distances. Say, 10 ft, 30 ft, and 50 ft. If they are all the same, then you've got it aligned correctly.

    If you can only get good far-field alignment on one of the three distances, then you need to go back and tweak your near field alignment again because it's not right.

    Once you get red and green dialed in, it's time to tweak the blue near field alignment. Make sure that the dot from the blue beam falls exactly in the center of the yellow dot on the dichro. (Remember that you'll have a red halo around the dot because the red beam is so much bigger. Try to keep the blue dot centered in the halo.)

    And again, once you get the near field alignment dialed in for the blue, then you can lock down the mount to the baseplate and start tweaking the adjustment screws to adjust the far field alignment.

    When you are done, you should have a perfect white beam that looks the same at 3 ft away from the projector as it does at 30 ft away.

    Alignment is tricky, but if you do it correctly you only need to do it once. I find that it helps to have a little adjustment available on the laser mounts as well as on the dichros, but if you have enough movement available on the dichro mounts you can hard-mount the lasers and still get your alignment correct.

    Adam

  10. #10
    Join Date
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    Default



    as people have said

    you can see from this pic the beams are in a line not on top of each other.

    the beams needs to be on top of each other when hitting the dichros
    Eat Sleep Lase Repeat


    Aluminium Optic Mounts

    http://www.laser-man.co.uk/opticmounts/

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