Hyperspectral Imaging


Unlike panchromatic imagers, which, like the human eye, see objects in the visible spectrum only, hyperspectral imagers can detect discrete reflections and emissions in many other spectra. This enhanced ability increases the probability of detecting materials of interest and provides additional information necessary for identifying and classifying these materials. Hyperspectral Imaging technology revolves around the ability of an instrument to record the solar energy reflected or re-radiated from an object’s or material’s surface. As the energy, in the form of photons is reflected or absorbed from the materials, it is possible to derive certain information about the material (shape, texture, chemical composition). Within the optical sensor the received energy is transformed into an electric impulse, which in turn is translated into a series of images where each image represents one of many narrowly defined spectral channels (bands) over a defined spectral range – Ultraviolet (UV), Visible (VIS) Near-infrared (NIR), Shortwave Infrared (SWIR), and Long Wave Infrared (LWIR).

Hyperspectral imagers utilize hundreds of wavelength channels that can record even the subtlest variations in the surface-reflected solar energy allowing for efficient and unequivocal identification of the observed targets. The technology provides the capability to detect and discriminate unique characteristics of materials and features, much like a fingerprint or DNA have unique features and structures. Typical applications of Hyperspectral Imaging (HSI) data and methods include materials mapping, identification of geologic materials; and environmental assessments for water quality, vegetation, insect infestations and coral reef analysis.


Each spatial pixel of the resultant image contains the spectral response of that target across hundreds of wavelengths of light. The result is a “cube” formed by the two spatial dimensions of the image (x,y axis) and a third dimension of spectra (z axis). Measuring the energy that is reflected by materials and objects over a variety of different wavelengths results in a spectral characterization for that object in the pixel.


As depicted above, the power of hyperspectral imagery is in the spectra. Spectral detail allows for the ability to classify and identify a material of interest when spatial information is not sufficient to discriminate an object or material.


Documents

L3 Information Delivery Cycle and Support [pdf]