visiblenearinfrared

Visible near infrared (VIS-NIR) denotes the portion of the electromagnetic spectrum that includes the visible range and extends into the near-infrared. A common definition spans roughly 380–2500 nanometers, with the boundary between visible and near-infrared often placed around 700–800 nanometers. The VIS-NIR region is used in spectroscopy and imaging because many materials show characteristic reflectance and absorption features in this range, arising from overtone and combination vibrations as well as various molecular absorptions.

Detectors and sources for VIS-NIR measurements rely on specialized technologies. Silicon detectors cover roughly 380–1100 nanometers, with some extended devices reaching around 1200–1300 nanometers. Indium gallium arsenide (InGaAs) detectors extend sensitivity to about 1700–2500 nanometers, depending on composition. For longer wavelengths, detectors such as indium antimonide (InSb) or mercury cadmium telluride (HgCdTe) are used. Light sources include light-emitting diodes and laser diodes in the 750–980 nanometer and 1050–1550 nanometer ranges, along with broadband sources for spectroscopy.

Applications span several fields. In remote sensing and agriculture, VIS-NIR is used for vegetation indices and crop monitoring. In chemistry and pharmaceuticals, NIR spectroscopy enables non-destructive composition analysis. Medical imaging employs near-infrared techniques for tissue imaging and functional monitoring (NIRS). In industry, VIS-NIR helps with material identification, quality control, and process monitoring. In telecommunications, the near-infrared window near 1310 and 1550 nanometers supports fiber-optic data transmission.

Limitations and considerations include strong water absorption bands and atmospheric attenuation at certain wavelengths, which can constrain outdoor measurements. Infrared sensitivity in imaging sensors is often balanced with the need to suppress NIR to preserve true color in visible cameras, and terminology can vary between disciplines.