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So I'm using near-infrared light of the wavelength of order 700-800 nm. I need it focused at one point. I was wondering if using glass lenses would do the job or not?

Dan
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1 Answers1

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Yes, they would work, I've done it myself.

Michael Walsby
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  • ok @MichaelWalsby . Two follow-up questions. First, are there some limits of the lens to be used? like the thickness of the lens and so on. Second, what can I do to make sure the lens that I'm working with actually bends infrared light? – Dan Jul 18 '19 at 11:02
  • The issue is that normal glass is not very transparent to IR. As focusing, it works, but may absorb most of your light. For your 700-800nm semms to have no problems. See here: https://physics.stackexchange.com/questions/74638/transmittance-of-glass – patta Jul 18 '19 at 12:16
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    Why not take some lenses and use an infra-red lamp or an electric fire as an infrared source, and focus the rays on the back of your hand? When it begins to hurt, that is a sign the infrared is being focussed, and the lense which hurts most of all is the best one to use. – Michael Walsby Jul 18 '19 at 13:23
  • @MichaelWalsby, that's a good point, but the issue is that I need the source and lens to be very small... – Dan Jul 18 '19 at 15:02
  • @patta, that's a good lead to start. Thanks :) – Dan Jul 18 '19 at 15:03
  • patta's link seems to indicate that at 700-800nm Michael Walsby's answer is correct – Paul Young Jul 18 '19 at 15:59