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I understand the basic principle, bodies with higher temperature than 0K produce infrared radiation emission, a thermographic camera detects that radiation.

However, my question is how that radiation/information is captured and transferred into an image picture?

For example, for photographic film the light impacts the film, the compound reacts to external light with a small chemical reaction, based on those modifications we have an image pattern.

What's the equivalent process for thermographic cameras?

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  • $\begingroup$ See en.wikipedia.org/wiki/Thermographic_camera. These cameras use cooled, narrow-gap semiconductor sensors (similar to a CCD or a CMOS chip in cameras for visible light) or bolometer arrays. A bolometer is basically a very sensitive thermometer that reacts to radiation heating it. $\endgroup$
    – CuriousOne
    Commented Feb 22, 2016 at 22:58
  • $\begingroup$ @CuriousOne that's the point. Wikipedia ir really poor describing how that narrow-gap semiconductor is really working. Everything googling are books. Bolometer looks easier to understand (however, how temperature is measured in a surface?) $\endgroup$
    – Trebia Project.
    Commented Feb 22, 2016 at 23:07
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    $\begingroup$ Narrow gap semiconductors work pretty much the same way as silicon does (notice the handwaving!), just the band gap is smaller, i.e. it takes less photon energy to separate an electron and a hole. In silicon that's approx. 1.1eV, in Germanium it's still 0.67eV. PbSe gets us to 0.27eV, InSb to 0.17eV at room temperature and 0.23eV at 80K. en.wikipedia.org/wiki/Mercury_cadmium_telluride has a variable band gap and can seemingly be used down to $12\mu m$ wavelength... much beyond that it's probably better to use bolometers. $\endgroup$
    – CuriousOne
    Commented Feb 22, 2016 at 23:14
  • $\begingroup$ @CuriousOne arg... the explanation of the physical principle is actually in the description of a material!!! Sometimes wikipedia is kind of odd... $\endgroup$
    – Trebia Project.
    Commented Feb 22, 2016 at 23:22

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