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Cree X primary optics ! (do they even exist??)

  • Jerommel Friday, January 3, 2014 4:35 AM Reply
    I would love to see some lenses to pre-focus (condense) Cree X series LEDs, you know, like the Q5 and T6, which already have a lens like bubble, to bundle it to 120°.
    But 120° is not narrow enough..
    You can not catch all of it wit a plano-convex lens, because it will only reflect light that comes at it at an angle sharper than 45°.
    So how do we focus this 120° flood into something like a 80° beam, so that we can properly focus ALL of the light emitted on to a (preferably zoomable) lens to >0° (projection of the 'chip')?
    We would need a tiny little lens which would be rather hollow at the LED side, so it can take the full >120° flood of light, and on the other side it will probably be very bulbous.
    Maybe some fresnel type output-side ...?
    I'd better leave that to the experts.
    But do they make stuff like this somewhere?
    I want 10 pieces. ;)
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  • Jerommel Saturday, January 4, 2014 2:24 AM Reply
    Wow, the response is amazing, DX community !!

    lol
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  • desolder Top 10 Forum Poster Saturday, January 4, 2014 3:59 AM Reply
    Too bad DrJones is no longer as active on DX these days. He's the master of optics. Try reposting this over at BLF. I believe he's still active over there.

    What you propose sounds reasonable. I've seen this discussed a few times over at CPF and BLF, but I haven't seen anyone try it.

    You can not catch all of it wit a plano-convex lens, because it will only reflect light that comes at it at an angle sharper than 45°.

    I believe you're confusing the glass-to-air transition with the air-to-glass transition. Total internal reflection does not happen at the air-to-glass transition, so even beams entering beyond 45 degrees can get refracted, rather than totally reflected.
    What's up with the scrubbed LED driver IC markings?
    What are they trying to hide?

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  • Jerommel Saturday, January 4, 2014 9:54 PM Reply
    You're right.
    I should have said that beyond (give or take) 45° reflection increases and as a consequence refraction will decrease.
    (English is not my native tongue..)
    The (usually) flat 'input' side could also be made anti-reflective, but that's a costly process..
    I don't know what BLF or CPF is. The "F" probably means forum?
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  • gasbag11 Top 10 Forum Poster Saturday, January 4, 2014 10:43 PM Reply
    Budget Light Forum

    Candle Power Forum

    CPF is a little on the "snobby" side imo.
    NO! I don't know why DX screwed up the site so badly.
    Ask them.
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  • desolder Top 10 Forum Poster Sunday, January 5, 2014 6:22 AM Reply
    I wouldn't be too worried about the effect of reflection at high angles of incidence at the air-to-glass interface. Even at 60 degrees, the half-power beam angle for an XML/XPG LED, the reflection is only about 10%. At about 75 degrees, the reflection is about 20%, or 80% transmittance. Beyond 75 degrees, the reflectance rises sharply, but then the output of the LED itself drops off sharply. If you still want to capture this light, a parabolic reflector is probably your best option. See Fresnel Equations wiki: http://en.wikipedia.org/wiki/Fresnel_equations

    DX does not sell a large variety of lenses. Do a google search for "surplus lens" to find some other vendors. I've purchased many lenses for experimentation from the top search result.
    What's up with the scrubbed LED driver IC markings?
    What are they trying to hide?

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    post edited by desolder on 1/7/2014 at 7:31 AM
  • Jerommel Sunday, January 5, 2014 11:15 AM Reply
    Wow, that lens finder is really helpful !
    Thanks !
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  • Jerommel Saturday, February 22, 2014 2:13 AM Reply
    But they hardly have any aspherical lensen suited for LEDs...
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  • desolder Top 10 Forum Poster Saturday, February 22, 2014 2:28 AM Reply
    Right. I assumed you only needed a long focal length lens to pre-focus the beam so more of it hit the aspheric.
    What's up with the scrubbed LED driver IC markings?
    What are they trying to hide?

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  • Jerommel Saturday, February 22, 2014 5:07 AM Reply
    Yeah, something like that, but I get a ring or doughnut pattern with the sphericals.. :\
    Feels a bit like re-not-inventing the wheel... ;) A somewhat pricey lesson too...
    Found some candidates on Ali's though, but that's 20 pieces...
    Those are (on the drawing and in the text) aspherical postive meniscus lenses, about 9mm diameter.
    But the picture is suspiciously different from the technical drawing..
    Hmm..

    Maybe a small conical reflector can help getting all the light out..
    We'll see, maybe..
    Or one of them modern acrylic reflectors, no zoom..
    They sure can produce a nice floody beam.
    And I have a C8 on its way, plus an orange peel reflector, so we'll see what's actually best and / or most usable.
    I like the big circle of light from a zoomed out zoomer though.

    In the mean time very happy with the 2dn gen. CREE's.
    Lots of light and (as a consequence) significantly less heat then previous.
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