The International Commission on Illumination (CIE) recommended the division of infrared radiation into the following three bands:
IR-A
0.7 – 1.4 µm, 215 THz – 430 THz
IR-B
1.4 – 3 µm, 100 THz – 215 THz
IR-C
3 – 1000 µm, 300 GHz – 100 THz
Astronomy division scheme
Designation
Abbreviation
Wavelength
Near-Infrared
NIR
0.7–2.5 µm
Mid-Infrared
MIR
2.5–40 µm
Far-Infrared
FIR
40–350 µm.
Sensor response division scheme
Near-infrared
0.7 – 1.0 µm
from the approximate end of the response of the human eye to that of silicon
Short-wave infrared
1.0 – 3 µm
from the cut-off of silicon to that of the MWIR atmospheric window. InGaAs covers to about 1.8 µm; the less sensitive lead salts cover this region.
Mid-wave infrared
3 – 5 µm
defined by the atmospheric window and covered by Indium antimonide [InSb] and HgCdTe and partially by lead selenide [PbSe]
Long-wave infrared
8 – 12, or 7 – 14 µm
this is the atmospheric window covered by HgCdTe and microbolometers
Very-long wave infrared (VLWIR)
12 – 30 µm
covered by doped silicon
Commonly used sub-division scheme
Division Name
Abbreviation
Wavelength
Photon Energy
Characteristics
Near-infrared
NIR, IR-A DIN
0.75–1.4 µm
0.9–1.7 eV
Defined by the water absorption, and commonly used in fiber optic telecommunication because of low attenuation losses in the SiO2 glass (silica) medium. Image intensifiers are sensitive to this area of the spectrum. Examples include night vision devices such as night vision goggles.
Short-wavelength infrared
SWIR, IR-B DIN
1.4-3 µm
0.4–0.9 eV
Water absorption increases significantly at 1,450 nm. The 1,530 to 1,560 nm range is the dominant spectral region for long-distance telecommunications.
Mid-wavelength infrared
MWIR, IR-C DIN; MidIR.[7] Also called intermediate infrared (IIR)
3–8 µm
150–400 meV
In guided missile technology the 3–5 µm portion of this band is the atmospheric window in which the homing heads of passive IR ‘heat seeking’ missiles are designed to work, homing on to the Infrared signature of the target aircraft, typically the jet engine exhaust plume. This region is known as thermal infrared, but it detects only temperatures somewhat above body temperature.
Long-wavelength infrared
LWIR, IR-C DIN
8–15 µm
80–150 meV
The “thermal imaging” region, in which sensors can obtain a completely passive image of objects only slightly higher in temperature than room temperature, (for example, the human body), based on thermal emissions only and requiring no illumination such as the sun, moon, or infrared illuminator. This region is also called the “thermal infrared.”
