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Concentrating radiation from blackbody with lens

  1. Jun 22, 2011 #1
    1)Is it possible to concentrate infrared radiation from a blackbody with a lens?
    2)Should a lens be at different temperature from a blackbody?
  2. jcsd
  3. Jun 22, 2011 #2


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    Sorry, misunderstood the question!
    Last edited: Jun 22, 2011
  4. Jun 22, 2011 #3
    1) Yes. You can buy nowadays infrared cameras with infrared lenses. See http://www.flir.com/thermography/americas/us/products/?id=17972", for example. Infrared radiation is an electromagnetic wave just like visible light, so it obeys the law of refraction just as well and bends through a lens. The trick is to build a lens out of a material is not opaque in the infrared.

    2) A passive lens needs to be at a lower temperature then the blackbody, otherwise the lens' own blackbody radiation will swamp out the signal. But this is automatic for typical applications. The temperature of living creatures, machines in use, etc. tend to be higher than the room temperature at which the unmodified lens exists. To image lower temperatures than room temperature, two methods can be used. The camera can be cooled. This can be expensive but effective, as the http://en.wikipedia.org/wiki/Cosmic_Background_Explorer" [Broken] mission demonstrated. Or the camera can be actively stabilized but not significantly cooled. Using this approach, the system is held at a temperature and differences in temperature are measured.
    Last edited by a moderator: May 5, 2017
  5. Jun 23, 2011 #4
    I thought on possibility to use a lens method in geothermal power harness.
    For exampe underground cavity could be properly shaped and filled with water or similar liquid to concentrate infrared light coming from underground and direct IR ray to the surface where it could be transformed to electricity with help of photocells.I think it could eliminate problem with water cycling and management.But as you said the lens should stay at different temperature from heat source than it makes some complications.
    I thought on possibility to reduce amount of holes to cycle water and increase heat harvesting from large underground areas with minimal amount of holes to drill.Unfortunately water is not very energy dense carrier and it requires lot of expensive drilling.
  6. Jun 23, 2011 #5
    Ah, you don't seem to mean for imaging purposes, but for long-term energy transfer purposes. In that case, I think mirrors would be more suitable than lenses for beam shaping.
  7. Jun 24, 2011 #6

    Claude Bile

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    This is why it helps to give context when asking questions.

  8. Jun 24, 2011 #7
    Do you think something similar to what I was thinking about could be practically created?With help of mirrors?Should thouse mirrors stay at different temperature from underground cavity?
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