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What beam angle are these please?

  • SkUG123 Friday, February 15, 2008 7:13 AM Reply
    Thank you
    I am a very rude naughty boy!
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  • dsvilko Wednesday, January 14, 2009 11:20 AM Reply
    When used with a Cree XR-E emitter (had to modify the white lens holder to fit) it produces about 20-degree wide beam surrounded by a ~5-deg darker ring and some spill. The central area is of relatively equal brightness (with some brighter and darker spots). It would probably produce a different (better?) pattern with a non-Cree emitter.
    There are some beamshots in this thread:
    http://forums.mtbr.com/showthread.php?t=483807
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  • dsvilko Monday, January 19, 2009 4:32 AM Reply
    I was talking about a wrong lens! This one fits Cree emitters perfectly and very tightly (really no need to glue them to the emitters) and has a nice 8-deg central hotspot with relatively sharp edge. There is also some spill.
    Here is a beam shot (scale is in degrees from the center):
    http://domjan.fizika.org/1920-clear.jpg
    This is with an added one layer of Scotch tape:
    http://domjan.fizika.org/1920-tape.jpg
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  • sheepish Top 10 Forum Poster Tuesday, May 25, 2010 6:37 AM Reply
    Remembering 30 years.
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  • Xumixu Monday, December 7, 2015 5:50 AM Reply
    Is it 8 deg cone or 8 deg from the center? (16º cone)?

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  • sheepish Top 10 Forum Poster Monday, December 7, 2015 5:56 AM Reply
    Remembering 30 years.
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  • Xumixu Monday, December 7, 2015 6:14 AM Reply
    Beside remembering me that I have to process some powder XRD data (scherrer's formula), you just gave me the feeling that "it seems" that is 8º cone (even though i think that 8º cone would be a quite narrow beam such as of throwers), so I maintain my question for a straight answer.

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  • sheepish Top 10 Forum Poster Monday, December 7, 2015 6:25 AM Reply
    You just gave me the feeling you might better understand that article if you read it in your own language. But all you need to understand is what "full width at half maximum" means. It's the "full width" part you're most interested in.

    The two main reasons why these are such nice total internal reflection (TIR) optics is they clip securely to the LED (which also positions the optic at the right place), and they produce a narrow beam. The sad thing is that the XR-E is no longer one of the best LEDs available.
    Remembering 30 years.
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  • Xumixu Monday, December 7, 2015 6:33 AM Reply
    That was what made me believe that was the cone. Thanks for confirming it. Also knowing that TIR has the advantage of having narrow beams is quite helpful (I thought that was just a simpler/thoughter alternative to metal reflectors) :)

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  • sheepish Top 10 Forum Poster Monday, December 7, 2015 6:49 AM Reply
    TIR optics are in some ways simpler, as they can be made of plastic and don't need extra polishing or chroming to reflect well. They are more efficient than reflectors and have less spill, which is the light that comes directly from the LED that's not in the central beam.

    I still use a keyring torch I modified with an XR-E and one of this sort of optic (bought from somewhere else many years ago). The optic works very well, producing a well defined spot.
    Remembering 30 years.
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