Infrared imaging

All objects above 0 Kelvin emit electromagnetic radiation associated with the thermal activity on the surface of the object. For terrestrial temperatures (around 300 Kelvin), objects emit a good portion of the electromagnetic flux in the infrared part of the electromagnetic spectrum. The visible band spans wavelengths from 0.4 to 0.7 micrometers (infrared engineers typically use micrometer/μm for wavelength rather than the nanometer or wavenumber more commonly used in other fields). Infrared imaging devices convert energy in the infrared portion of the electromagnetic spectrum into images that can be created by the human eye. The unaided human eye cannot image infrared energy because the lens of the eye is opaque to infrared radiation. The infrared spectrum begins at the red end of the visible spectrum where the eye can no longer sense energy. It spans from 0.7 μm to 100 μm. The infrared spectrum is, by common convention, broken into five different bands (this may vary according to the application). The bands are typically defined as: near infrared (NIR) from 0.7 to 1.0 μm; short wavelength infrared (SWIR) from 1.0 to 3.0 μm; mid-wavelength infrared (MWIR) from 3.0 to 5.0 μm; long wavelength infrared (LWIR) from 8.0 to 14.0 μm; and far infrared (FIR) from 14.0 to 100 μm. These bands are depicted graphically in Fig. 1, which shows the atmospheric transmission for a 1-kilometer horizontal ground path for a ‘standard’ day in the United States. These types of transmission graphs can be tailored for any conditions, using sophisticated atmospheric....