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Thread: Why can't other light sources be used to get tight (laser like) beams?

  1. #11
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    I went to a show last night. They had LED lights that looked pretty good. Almost laser like. This image doesn't do it justice. It looked much better in person. Still NOT a laser but not bad for LEDs.

    Click image for larger version. 

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  2. #12
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    One word, coherent.
    This space for rent.

  3. #13
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    Check out Wavien, they make ultra narrow beam LED flashlights:
    http://www.wavien.com/flashlights/

  4. #14
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    Quote Originally Posted by dream View Post
    Just found flashlights with focusing lens to get a straight beam which shoots few hundred meters before dimming.
    It's still no comparison to the low divergence beam from a laser.

    Maybe I should get into xenon/led focusable lights.
    This is a good chance to learn by experimenting. Do some tests with various lenses and an incoherent light source and you'll soon see the difference that a coherent laser beam makes.

    EDIT: Holy shit...


    Didn't know there were such "spot lights".
    There aren't. That picture is a photoshop. You can get "pretty good" performance with awesome optics and a super-bright source, but you can't get results like you see in the picture above.

    I was gathering parts to build a 10W blue laser, but don't think it will look half as impressive for the tourists. Then again I haven't seen brighter than 2W and from a distance to be sure.
    Thought?
    Half as impressive, as compared to what?

    If you want to make it look really impressive, build your 10 watt blue laser and then up-colimate the beam. That is, expand the beam diameter (basically run the beam through a telescope in reverse) to lower the divergence. If you blow the beam diameter up to something really fat like 25 or 30 mm, you can get the divergence down to very low levels. (Around .1 mrad) That will yield a nearly parallel beam that will appear* to travel for miles without getting larger... Assuming this is the effect you're looking for.

    Adam

    * In fact, it will be diverging, of course. It's just that at such low divergence, you won't be able to notice it easily.
    Last edited by buffo; 03-27-2015 at 15:36. Reason: typo

  5. #15
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    swamidog is offline Jr. Woodchuckington Janitor III, Esq.
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    Quote Originally Posted by buffo View Post
    If you want to make it look really impressive, build your 10 watt blue laser and then up-colimate the beam. That is, expand the beam diameter (basically run the beam through a telescope in reverse) to lower the divergence. If you blow the beam diameter up to something really fat like 25 or 30 mm, you can get the divergence down to very low levels. (Around .1 mrad) That will yield a nearly parallel beam that will appear* to travel for miles without getting larger... Assuming this is the effect you're looking for.

    Adam

    * In fact, it will be diverging, of course. It's just that at such low divergence, you won't be able to notice it easily.
    tried that... shattered some expensive optics in the process.
    suppose you're thinkin' about a plate o' shrimp. Suddenly someone'll say, like, plate, or shrimp, or plate o' shrimp out of the blue, no explanation. No point in lookin' for one, either. It's all part of a cosmic unconciousness.

  6. #16
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    Lightbulb

    Quote Originally Posted by dream View Post
    ...I was gathering parts to build a 10W blue...Then again I haven't seen brighter than 2W.. Thought?
    ..yer gonna need a bigger Blue.. http://www.photonlexicon.com/forums/...213#post302213

    ..Not spamming yer thread.. OK fine, I am.. jk..

    j
    ....and armed only with his trusty 21 Zorgawatt KTiOPO4...

  7. #17
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    After reading through all the accurate responses to the OP, I like Steve's statement in #3 the best because I think it is the most direct reason. Coherence is the reason the light is the way it is ie monochromatic and intense. Amplification is what allows it to be more intense than the limit set by a black body source.

    Non-coherent sources can be impressive because the eye can only "see" some of the properties of lasers. Ultra-narrow line widths look the same as broad band sources to the eye. Ultra-fast pulse trains look the same as a CW beam of the same average power. Ultra-low divergence beams are not going to be distinguished from low divergence beams if they both are under the resolution limit of human vision. Super powerful beams will look no more intense than moderately powerful beams once the saturation limit of the retina is reached; the beam just seems to get fatter. Try looking at a 5W , 532nm far field spot and then look at it through a ND filter. It looks much smaller.

  8. #18
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    The searchlight on the back porch in the picture above looks like a Carlisle Marine Xenon Searchlight ...

    http://carlislefinch.com/content/commercial-marine


    Call them to get a quote and die of sticker shock.... 12" / 24 cm parabolic mirrors with a 95% reflective coating are not inexpensive.


    To get a good beam with non laser sources you need VERY large diameter optics and a tiny arc source on the order of 0.6 mm wide.

    http://www.victorysearchlights.com/victory5.html

    http://www.victorysearchlights.com/

    I used to love seeing those as a child.

    Here is a link to some of the original beam show guys, including manuals and schematics, although where you would get a Amplidyne these days boggles my mind:

    http://www.searchlightparts.com/sear...ts/?page_id=14

    Steve
    Last edited by mixedgas; 03-28-2015 at 04:16.
    Qui habet Christos, habet Vitam!
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    When I still could have...

  9. #19
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    Unless I misunderstood the point.
    No, you get it!
    When you consider that probably 95+% of the posts on this forum deal with the visual, not the optical, aspects of lasers then the difference between lasers and incoherent sources is just a matter of how it looks. That is why there is so little discussion of IR diodes even though, in terms of power, they're just as cost effective.
    A sharp beam from a 3kW xenon short arc is going to throw maybe 150,000 lumens into the sky. This is about equivalent to 100W from a 555nm source which is close enough to a 532nm LaserScope to be basically the same thing. So, with 2 1/2 x the power of an LS this is much brighter, but the beam from a LS is still much tighter than a search light, yet the CW xenon is a lot safer than the Q switched laser and probably lighter and cheaper. Yet again, just try to pump a dye with a search light.
    As long as you get the right tool for the job, they should both be considered. The LASER does sound sexier though. Know what I mean?

  10. #20
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    The get almost laser like beams with a point source before lasers folks used Zr arc lamps. Sylvania made from 2W to at least 100W, the lower the power the smaller the arc and the tighter the beam could be but also the lower the power. So if you took the 2 watter, a good lens and filters you could get a few microwatts of collimated beam at one wavelength with a 25 nm bandwidth; I will tale a laser.

    I still use a C100 Gates/Sylvaina system as a collimated white light sourse for demonstrations like dispersion, thin film interference etc at USF Physics in Tampa. The beam is about 2" diameter with a <10 mR divergernce; the image of the arc.
    Phil Bergeron( AKA 142laser)

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