Infrared Imaging

The field of Infrared Imaging comprises wavelengths just outside the visible spectrum and into the far infrared. For classification purposes Infrared Imaging is commonly divided into near-infrared (NIR), shortwave infrared (SWIR), mid-wave infrared (MWIR) and long-wave infrared (LWIR).

Near-infrared (NIR): ranges from 0.7 to 1.0 micrometers (from the approximate end of the response of the visible). Most silicon based cameras (CCD and CMOS) are sensitive to VIS and NIR.

Short-wave infrared (SWIR): ranges from 1.0 to 3 micrometers (from the cut off of silicon to just prior to the MWIR atmospheric window). InGaAs based detectors typically cover to about 1.7 micrometers and then begin to drop off.

Mid-wave infrared (MWIR): range from 3 to 5 micrometers (defined by the atmospheric window and covered by detectors based on InSb or MCT).

Long-wave infrared (LWIR): covers 8 to 12, or 7 to 14 micrometers: the atmospheric window (Covered by MCT and microbolometers). This is the range for "thermal imaging", in which sensors do not require external light and instead obtain an image based on thermal emissions.

Very-long wave infrared (VLWIR): ranges from 12 to about 30 micrometers and is covered by doped silicon or MCT.

Each wavelength opens up different challenges and possibilities for the use of IR cameras. The applications of each type of technology are well documented and system designers can evaluate the pros/cons of each wavelength, sensor, and detector to identify the best choice for their application.