Who has made their own lense?- Mtbr.com
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  1. #1
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    Who has made their own lense?

    I use cheap Amazon LED flashlights that tick all my boxes except the beam throw. They're focusable, but I want a cutoff.

    I know optics are not simple. Has anyone had any luck fashioning their own, or modifying existing lenses? These are round (flat on the back) and appear to be made of some sort of polycarbonate with a uniform density.

  2. #2
    Randomhead
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    from what I have seen, designing a reflector for a shaped beam is a fairly advanced activity, and there are specialized software programs to do it. I think that I could machine one, but it takes an expensive machine. Cygolyte uses fresnel lenses to shape their beams. It works pretty well. I'm not sure where you could get one, but it's within reason for a hobbyist, I think.

  3. #3
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    Making optics is very tough. To start, the design alone is complex. Then manufacturing it would best be done by injection molding. That requires a mold be made to extremely tight tolerances and surface finishes.

    I have tried making reflectors on a CNC lathe. The machine could produce the parabolic shape with a looping macro program containing a formula for interpolating a parabolic curve. After machining it required sanding and polishing. The reflectivity was not as good as commercially made reflectors which use a vapor deposited metallic coating.

    I did some experimenting trying to somewhat replicate the cut off beam from a Phillips Saferide light using modified commercial reflectors. I cut portions of the reflector away and oriented the emitter perpendicular to the parabolic axis. Because the commercial reflector's focal point and the emitter die no longer being in a good alignment the resulting beam had many defects. It did achieve a reasonable cut off but had rings of dark and bright areas.

    Some folks have found reasonable results using "hood" over the top of a light to shield upward cast light. There have been a few old threads on this forum discussing those.
    GoPro adapters for bike lights http://www.pacifier.com/~kevinb/index.html

  4. #4
    X83
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    I have the same flashlight with the 1-Mode Cree XM-L2 U2 LED and they use a plano convex glass lens that's permanently pressed into place inside an aluminum threaded cap.

    This type lens is very easy to located in the same diameter with a different center thickness heights but you would have to make a tube fixture to press them out and then re-crimp it back into the aluminum housing.

    If you're trying to modify the beam cutoff height you could mount a flat metal plate in between the focal point but my advice would be to discard this this flashlight and go with bicycle light that has replaceable XM-L 20mm stripe lenses with an oval beam cutoff pattern.

  5. #5
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    I think that there must be multiple revisions of this light, I've got two of them and there's a couple distinct differences. The lenses on both of mine are just set in place under the cap, definitely not pressed in. They sure feel like polycarb but I suppose they could be glass?

    I'll check into that stripe lens you recommended. That sounds like an ideal solution.

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