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Lens Question for Design of an Infrared Spotlight

  1. Feb 23, 2015 #1
    Hello All.

    I'm working on a project to build an infrared spotlight which will hopefully light up a distant object so that I can see it on an IP enabled night vision camera. The lens problem seems very straight forward, but I could use some help. Per the attached diagram, I want to focus the light from an led (or cluster of LEDs) on an object that is 40m tall, 400m away. Ideally, I'd like the LEDs + Optics to be housed in a piece of PVC pipe less than 2m long. Whats the easiest way to do this with off the shelf cheap plastic lenses?

    Thanks for the help...
     

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  2. jcsd
  3. Feb 23, 2015 #2

    Bystander

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    IR transparency and plastic are mutually exclusive.
     
  4. Feb 23, 2015 #3

    CWatters

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    I'm not an expert but I suspect you will need more power than that type of LED can produce. How sensitive is the camera? Perhaps start with that and work back?

    Perhaps you could use LEDs that have a 6 degree beam angle? No optics needed then.
     
  5. Feb 23, 2015 #4

    CWatters

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    You might have to explain that. How do TV remote controls work if (at least some) plastic isn't IR transparent.
     
  6. Feb 23, 2015 #5
    Great call CW! That's a much easier solution. Digikey has some very narrow radiation angle LEDs, so I'll solder together a cluster of those first and give that a try. Thanks, Zach
     
  7. Feb 23, 2015 #6

    Bystander

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    Just googled IR optics, and no plastic components.
     
  8. Feb 23, 2015 #7

    Redbelly98

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    The LED in question is in the near IR, at 850 nm. Aren't plastics typically transparent there?
     
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