Spectral imaging

Spectral imaging is photography that uses multiple bands across the electromagnetic spectrum. While an ordinary camera captures light across three wavelength bands in the visible spectrum, red, green, and blue (RGB), spectral imaging encompasses a wide variety of techniques that go beyond RGB. Spectral imaging may include the use of filters to capture a specific spectral range in an image. It may also involve illumination from outside the visible range, such as ultraviolet illumination. Capturing images in ultraviolet, infrared, x-rays, and other bands is possible through the use of the proper image sensors. It is also possible to capture multiple spectral bands for each pixel in an image, through the use of specialized hardware.

Various distinctions among techniques are applied, based on criteria including spectral range, spectral resolution, number of bands, width and contiguousness of bands, and application.

Multispectral imaging is a sub-category of spectral imaging in which filters and illumination are modified. For example, a scene could be illuminated with infrared and photographed in the visible range.

Hyperspectral imaging is another sub-category of spectral imaging. It is a combination of spectroscopy and photography, in which a complete spectrum or some spectral information (such as the Doppler shift or Zeeman splitting of a spectral line) is collected at every pixel in an image plane. Often, the phrase "spectral imaging" is used to denote this acquisition of a complete spectrum for every pixel in an image plane. Hyperspectral images are often represented as an image cube, a type of data cube.

imaging spectroscopy or

chemical imaging.

Applications include astronomy, solar physics, planetology, and Earth remote sensing.

See also

• Dopplergraph
• Imaging spectrometer