Understanding Infrared Thermography Reading 7 Part 2 of 2.pdf

Infrared optics are available in two general configurations, refractive and
reflective;
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Refractive optics (lenses), which are at least partly transparent to the
wavelengths of interest, are used most often for high- temperature
applications where their throughput losses can be ignored.
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Reflective optics (mirrors), which are more efficient but somewhat
complicate the optical path, are used more often for low-temperature
applications, where the energy levels cannot warrant throughput energy
losses.
An infrared interference filter is often placed in front of the detector to limit the
spectral region or band of the energy reaching the detector. The reasons for
spectral selectivity will be discussed later in this section.
Charlie Chong/ Fion Zhang