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Thread: Ready to align a mini RGB

  1. #1
    Join Date
    Feb 2009
    Location
    Bedfordshire
    Posts
    46

    Default Ready to align a mini RGB

    Hi All,

    I've been working on a tiny RGB setup and am finally able to start the alignment process for the first time. I have some older version Laserwave dichros, (very kindly donated by Jem. Thanks Jem!), and just want to clarify a few things and seek advice.
    I have done some searching and looked through a few threads too. This one was particularly helpful -http://www.photonlexicon.com/forums/...=RGB+alignment

    The dichros I have are: Pass green/reflect red, and pass red and green/reflect blue, (pretty standard stuff). I'm also pretty sure I have them the right way round! Red reflects from the side that looks reddest, blue from the side that looks bluest, etc. Correct?

    I would just like to clarify, "near field alignment", and, "far field alignment", and the best approaches for both. I think I'm correct to say that I start with the green and go from there but from there this is all new!

    With near field, is it as simple as moving the beam to make sure the reflecting beam is hitting the dichro at the same point the passed beam(s), leaves the dichro? Should The beams be mixing as well as possible at this point too? Better done with smoke?

    After this, the dichros are tweaked for the far field? Is the green nailed and move all the others to it?

    Many thanks on any tips you can offer and I apologise for any clear ignorance in my questions. This is a bit of a weird homebrew setup so I dare say I'll have to work around a few problems but I will show how it turns out with some pics.

    All the best,

    M

  2. #2
    Join Date
    Aug 2008
    Location
    Berkshire
    Posts
    661

    Default RGB alignment

    Quote Originally Posted by Morgan View Post
    Hi All,

    I've been working on a tiny RGB setup and am finally able to start the alignment process for the first time. I have some older version Laserwave dichros, (very kindly donated by Jem. Thanks Jem!), and just want to clarify a few things and seek advice.
    I have done some searching and looked through a few threads too. This one was particularly helpful -http://www.photonlexicon.com/forums/...=RGB+alignment

    The dichros I have are: Pass green/reflect red, and pass red and green/reflect blue, (pretty standard stuff). I'm also pretty sure I have them the right way round! Red reflects from the side that looks reddest, blue from the side that looks bluest, etc. Correct?

    I would just like to clarify, "near field alignment", and, "far field alignment", and the best approaches for both. I think I'm correct to say that I start with the green and go from there but from there this is all new!

    With near field, is it as simple as moving the beam to make sure the reflecting beam is hitting the dichro at the same point the passed beam(s), leaves the dichro? Should The beams be mixing as well as possible at this point too? Better done with smoke?

    After this, the dichros are tweaked for the far field? Is the green nailed and move all the others to it?

    Many thanks on any tips you can offer and I apologise for any clear ignorance in my questions. This is a bit of a weird homebrew setup so I dare say I'll have to work around a few problems but I will show how it turns out with some pics.

    All the best,

    M
    Hello mate, just read your post. Have a look at Robs excellent 'Stanwax Laser laser alignment guide' in the downloads section of his site http://www.laser-wave.co.uk/

    cheers
    Adrian

  3. #3
    Join Date
    Feb 2010
    Location
    Melbourne, Australia
    Posts
    1,106

    Default

    ...and for my two cents worth:

    Assuming Green (1st), add Red (2nd), then add Blue (3rd)...

    Clear the area and ensure it is secure. Hook up your scanners to a power source and turn them on so that they centre. Safety goggles on. Power up your Green (1st) and give it enough modulation voltage to produce a clean beam, without burning the bejeezus out of anything and everything and so that the projected spot is dim enough to view comfortably with the goggles on.

    1. Get your Green (1st) beam lined up with the centre of the (typically) lower X scanner mirror and parallel to the baseplate, usually by placing sheets of aluminium (shims) under the laser module until it is the right height. Also ensure that you have both your dichros in approximately the right position and at approximately the correct angle (~45 degrees), so that the refraction of the beam is factored in when aligning with the scanners (valuable lesson learned here). You should get a nice clean spot on the wall perpendicular to your final beam path. Try and use a distant wall if you can (this will be important later for far-field alignment).
    2. Keeping your Green (1st) going, add some modulation voltage to your Red (2nd) until the two beams are of a similar brightness.
    3. Get your Red (2nd) beam at the same height as the Green (part 1 of near-field alignment), either:
      • by placing shims under the laser module until the beam is both parallel to the baseplate and at the same height as the green (less flexible i.e. harder) or...
      • by reflecting the beam off a mirror and aligning the reflected beam on the first colour mix dichro at the point where the Green beam passes straight through it (more flexible i.e. easier). This means you can have each laser at differing heights to each other without any issues.

    4. Get your Red beam, reflected off the first colour mix dichro, to align, centrally overlap the Green beam (part 2 of near-field alignment) and aimed toward the same spot on your X scanner mirror, by adjusting the dichro mount adjustments. The projected spot on the wall, off the scanners, should also overlap so that both the Green and Red spots make a nice yellow spot or a green surrounded by red spot (far-field alignment). You may have to revisit the aim of the Green beam's bounce mirror or laser module's positioning, as the dichro mount is unlikely to have the mirror-surface mounted mid-axis. As a result, I found a bit of tweaking of the dichro required a bit of tweaking of the bounce mirror (and vice-versa) until the beams were sweet (IMHO a strong argument for using bounce mirrors).
    5. Block your Red beam with a handy block of black anodised aluminium or similar (or turn off the Red's modulation voltage) and provide enough modulation voltage to get your Blue going.
    6. Repeat steps 3 and 4 for your Blue (3rd) beam, this time looking for a nice near-field alignment on the 2nd dichro and a good overlap of your beams to your scanners and centrally overlaid spot of Green and Blue on the wall demonstrating your perfect far-field alignment.
    7. Re-introduce your Red and check the alignment of all three, adjusting accordingly.
    8. Marvel in your mastery of total chromatically-aligned photonic goodness

    I've got some images here which may help (although the order of the lasers was slightly different in these - Red, add Green, add Blue).

  4. #4
    Join Date
    Feb 2009
    Location
    Bedfordshire
    Posts
    46

    Default

    Fan-bloody-tastic! Thanks to you both.

    I've had a look at Stanwax's article and read and understood the description above and all of this great advice has been absorbed, (or absorped, if you like!).

    I had a go the other night at aligning these on my own and didn't notice until after the process that the near field could have been much better. I don't think I had allowed for the refraction of the beams and therefore have stacked the three beams instead of overlaying them. (^a valuable lesson learned here too! ) I think the use of more smoke will help rectify this as the space to see the overlapping spots is a challenge but smoke showed the beams very well. I'm not the happiest blowing smoke over everything but needs must in this very confined build.

    Pre optic measurements add up to 500mW. Losses amount to what seems like a large 200mW. I'm really not going to be too concerned over this for a number of reasons but wish to understand why and where losses have ocurred. Below is a pic of the dichros and turning mirror, (left to right - Turning mirror; reflect red/pass green; reflect blue, pass/red and green). These are old style LaserWave dichros kindly donated by Jem. You can see that the one on the right is chipped, which is fine as I don't need to use that bit but also the colour seems patchy. Is this due to, 'bleaching'?



    I have some Casio projector dichros to try out too. These seem to be pass red and blue/reflect green and pass blue/reflect red and green. To me this means I will need to reverse the order of the modules, from Green/Red/Blue to Blue/Red/Green, but the advantage as I see it is that I can afford to drop much more blue being a 445 capable of 1W! The unfortunate thing though is that still won't allow me to put the weakest colour, Red, last in the optics and could end up losing even more than the current setup. Any thoughts here or is it a matter of just trying it?

    Here's another pic. This one of the spot I achieved last night. I will be giving all the optics a good clean before reassembling again so hopefully I will lose a little of the flare.



    I will post a more comprehensive thread showing the build so far. I do not yet have any beam control hardware or colour mix control. This combining set is the first part of a larger project so there is lots to do before a complete system is up and running for which I will no doubt require help too, so please be patient with me!

    Thanks for looking.

    M
    Last edited by Morgan; 07-20-2010 at 08:19.

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