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Thread: Focus mixed RGB beam into fiber...

  1. #11
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    Thumbs up

    WOW! A thousand words there!!! :bow: I need more smilies...

    Is that going into or out of the fiber? I assume in but I guess it will look the same on both ends?

    Will the Achromat Lens, well is it one piece, and will it just screw into a MM1?

    Is the MM1 just a bracket, or is the x/y screws part of it. I have 3, but they were given to me... thanks david, and I am not sure what is actually part of it. Is it everything but the optic? Meaning will the fiber coupler have an attachment for the MM1, or can I get a MM1 Fiber Coupler? If that make sense...

    Thanks again yadda! I can almost see it with that picture. Atleast getting it into a strand, maybe not distributing it, but into the fiber...

  2. #12
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    Yeah, it sounds odd hooking it to a MM1, but the miniscule movement of the angles is actually pretty helpful in getting it aligned...


  3. #13
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    So you can take a laser and feed it into a fiber and it will come out a laser on the other end?

  4. #14
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    Yes, you can, however, you'll need to recollimate the laser at the exit point in order to have a usable beam. Not too easy, but doable, as far as I can tell by these posts .

    I actually tried once with a single wavelength. I got the laser in, but never bothered to try and collimate it as I don't have the necessary tools.

    Jeess, I'm starting to believe I got in the wrong hobby
    Remember the future?, That'd today, as you imagined it yesterday.

  5. #15
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    Lightbulb

    And look, it only took you 200+ posts... I think I knew over at CPF this was another "wrong" hobby... I think wrong just means expensive. At least it's not a passive hobby like collecting... well anything. I collect first edition SciFi books and once you get a "good" one, you can't do anything with it. Although, I can't blow an eye collecting books either.

    yadda, I actually think using an MM1 is a great idea. Is that how it will look on both ends, in and out?

  6. #16
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    Sorry, I wrote that post in a hurry. Josh chased me into the car as we have a show in Vegas tommorrow. On an unrelated note, we saw some really cool double rainbows right at sunset framing some bright orange mountains as we were crossing them.

    First, the achromat can be one lens or many. With modern optics, the quality will be mostly the same regardless, but you can reduce the effective focal length required with say the 3 element lens below. The decision of which exact type to use will depend on what your divergence and beam size requirements. The general rule being, the wider your beam, the better the divergence. A reasonable beam is 3-5mm with a divergence <2 milliradians. You can throw more money at it to improve it, but in the end, the diameter of the of the fiber determines the limits. Which is why small diameter fiber is better. But, as I mentioned above, it gets very hard to align into a very small fiber (and the damage threshold is more easily reached the tighter the focal point on the input) so standard compromises apply.

    Yes, given any beam into a fiber, you can recollimate it into a beam out. The reason you don't see too many HID bulbs forced into fiber is because the arc lamps have a (relatively) large point source, so the fiber will have to be thicker to get it in properly (and that will affect the final beam as described above). You can use a pinhole filter (like in holography) to clean the input beam profile up if you're serious about it.

    You only "need" an MM1 (or a knockoff with varying degrees of success) on the input side. You can "finger adjust" the output beam into the scanheads without much difficulty. On the input, very fine control is required due to the small spot size of the fiber.

    The input is usually just attached to the an MM1 with a bracket. You can play the actual mounting details by ear.

    On commercial units, they should come with fine-adjustment knobs already. Just mount them to a standard L bracket.

    Making the output collimator for cheap is easy, take a $2 gas station laser pointer, drill out the diode and place the fiber so the tip is right where the output of the diode would normally be. It doesn't have to be precise as you can align the divergence by turning the thread on the lens or moving the fiber back and forth (at least on the el-cheapo pointers I've run across).

    The input collimator done correctly can be expensive, but you can buy surplus achromats fairly cheaply. For a monochrome laser, you can even use any small convex lens with a reasonable focal length (though your results will vary depending on the quality of the lens)... I know they make some cheap knockoff 1" micrometers, You can ghetto up a translation stage or MM1 knockoff using those...

    It's certainly not rocket science and the commercial units are expensive mainly because it's a niche audience... I like tiny scanheads because they're easy to move around and set up... Fiber helps me do that even if the source laser is bulky...

  7. #17
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    I read that original question a bit more carefully...

    The MM1 is the two metal plates with holes in it including the adjustmet screws.

    The fiber should be hard mounted to something so the achromat can be adjusted using the XY screws or by rotating the Z axis of the lens.

    If you're feeling masochistic, a gas station laser pointer can work as the input module as well as the output. If you have the space a single achromat can be used as the output collimator as you asked.

  8. #18
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    Congrats on your 500th post allthat

    Jim

  9. #19
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    You can play the actual mounting details by ear.
    That would be the safest way to do it. That way you don't risk popping your eyes with those dangerous photons
    Remember the future?, That'd today, as you imagined it yesterday.

  10. #20
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    Wink

    I'd have to get a pair of those special ear muffs... Probably one for each wavelength...

    Thanks Jim!

    Um... What's this...

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