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Thread: Beam size issues RGB

  1. #1
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    Default Beam size issues RGB

    As my first green machine is now operating (sorta!) .. my mind keeps turning to the RGB system.
    One point of confusion seems to be the beam size. Greens abound in the 2-3mm size. Even blues and reds at lower power.
    The moment you look at blues and reds over say 100 mw you get a FAT beam. Like 5mm plus
    I am quite keen to look at one of Marconi's twin jobs but am hanging out hoping his new four beamer will show up soon.
    Obviously the red sets the game plan for the rest of the design (I think) as this is where the money has to go first.
    Any ideas ??
    How important is it or am I reading too much into fat beams for an RGB given that I do want it to do graphics.
    How do you compensate for say a nice 2mm green with a 2mm red and then a 5mm blue ?? how does that translate into white nicely ??
    Thanks guys

    Ray
    NZ

  2. #2
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    Quote Originally Posted by Pitts View Post
    As my first green machine is now operating (sorta!) .. my mind keeps turning to the RGB system.
    One point of confusion seems to be the beam size. Greens abound in the 2-3mm size. Even blues and reds at lower power.
    The moment you look at blues and reds over say 100 mw you get a FAT beam. Like 5mm plus
    I am quite keen to look at one of Marconi's twin jobs but am hanging out hoping his new four beamer will show up soon.
    Obviously the red sets the game plan for the rest of the design (I think) as this is where the money has to go first.
    Any ideas ??
    How important is it or am I reading too much into fat beams for an RGB given that I do want it to do graphics.
    How do you compensate for say a nice 2mm green with a 2mm red and then a 5mm blue ?? how does that translate into white nicely ??
    Thanks guys

    Ray
    NZ
    The first RGB I built the blue was about 1 to 2mm bigger then the rest of the beams. When doing beams you will not even notice it at all. On graphics you will see a little fringing but the untrained eye will not notice. The white is still white because it is so bright the glare covers the fringing.
    Now on the second the red is a little bigger and the effects are a little more pronounced due to the fact the eye is more sensitive to red.
    "Gravity its not just a good idea its the law"

  3. #3
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    actually my red starts off as 5mm but by the time it hits the wall it is the smallest of the three. The 100mW 650nm diode is set up to produce a convergent beam (at first) that beats the blue and green after 2 or 3 meters in terms of diameter.

  4. #4
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    My red and green beams when combined (with the green attenuated) look just that- red speckles in the air/ beam and green speckles. It's not a yellow beam. I guess it's the fog/ smoke that mixes them due to more photon collisions? I'd really like a pure orange beam, but that cost$$$.
    Too bad there isn't an optical "mixer" that could be put in the output to combine them before they hit the scanners..
    Last edited by steve-o; 06-05-2007 at 08:22. Reason: oops- sorry -getting off topic ;)

  5. #5
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    Lightbulb

    Quote Originally Posted by steve-o View Post
    My red and green beams when combined (with the green attenuated) look just that- red speckles in the air/ beam and green speckles. It's not a yellow beam. I guess it's the fog/ smoke that mixes them due to more photon collisions? I'd really like a pure orange beam, but that cost$$$.
    Too bad there isn't an optical "mixer" that could be put in the output to combine them before they hit the scanners..
    Isn't that what a PCAOM does?

    I find my beams are fairly close at the wall, but my wall is only 8 feet from my projector...
    Love, peace, and grease,

    allthat... aka: aaron@pangolin

  6. #6
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    Quote Originally Posted by steve-o View Post
    Too bad there isn't an optical "mixer" that could be put in the output to combine them before they hit the scanners..
    You could use fiber to do exactly this.
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  7. #7
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    You mean if I put R/G into a fiber, it would come out yellow or orange??
    Can you give details, cost, level of difficulty Dave?
    I suppose you have to re-collimate at the fiber end coupler?
    How about losses?

  8. #8
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    Cool

    Quote Originally Posted by steve-o View Post
    My red and green beams when combined (with the green attenuated) look just that- red speckles in the air/ beam and green speckles. It's not a yellow beam.
    That's strange. My red and green mix together to make a yellow beam, and it's clearly visible as yellow, not red speckles and green speckles.

    My guess is that you need to adjust your alignment. Have you checked your alignment in the near and far field? (IE: place a card a foot away from your projector and look at the overlap of the beams, then move the card 15-20 ft away and see if the overlap changes...)

    Also, what sort of fog machine are you using? If it's making monster particles (more like dust and less like fog) then that could contribute to the problem.

    But seriously, when I mix colors with my RGB rig, I can't see the individual color components that make up the final color. I only see the final color. As an aside, I think the human eye is better able to detect the "fringing" of a mis-aligned optical table than a camera is. For example, most of the pictures I took of my old setup (Argon, Hene, and DPSS pointer, which were *not* very well aligned at all) still showed the mixed color beams, but if you looked with your eyes you could see the two or three individual beams that were mixing together to produce the final color.

    If you mix red and green and your alignment is good and the beam profiles are close, you should see a yellow beam, not a partial red and partial green beam. Something is wrong...

    Adam

  9. #9
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    Adam,
    In normal air without any fog it looks like top picture. Wish it would look like bottom pic. Will a fiber do this? (I know i need fog)
    When it hits the white wall though it is bright yellow.
    Attached Thumbnails Attached Thumbnails rg beam.JPG  


  10. #10
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    Steve, you're so good with paint
    I have what you have in normal air, at least close to the projector. Haven't really looked at it further away. Once the beam starts moving the colors mix.
    I contribute this issue to the fact that my red beam is much wider than green and close to the projector. So a lot of particles cross only the red beam, showing red. Since the green beam diameter is still very small the green intensity is very high in the center of the mixed beam. Thus the particles that cross the center of the beam get hit by an ovewhelming amount of green making the red not show that much.
    Last edited by Zoof; 06-06-2007 at 09:00.

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