Multispectral imaging is a form of imaging that involves collecting data from two or more ranges of frequencies along the spectrum, such as visible light and infrared energy. There are a number of applications for multispectral imaging and the roots of the technology lie in satellite imaging. Many examples can be found on various websites, especially sites that provide data from orbiting satellites.
In something like a conventional photograph, people are only seeing data from the range of the spectrum that includes visible light. With a multispectral image, data from infrared, near infrared, radar, and other areas of the spectrum can be displayed as well. There are a number of different ways to present the data so that it will be meaningful to observers.
One option is a composite image that combines input from multiple spectra. This image will have a false color, with the data from spectra outside the visible range represented either with an artificial color like red or blue or in grayscale. Composite images can show areas of high energy and other things that may be of interest. Multispectral imaging can also result in a series of images showing the same thing at different wavelengths.
As an example of how multispectral imaging can be used, many archaeologists use this imaging technique routinely in their work. They start by recording data from the visual spectrum, showing an object as it is seen by the naked eye. Then they take images in areas of the spectrum like the infrared region to reveal things that are otherwise invisible. This technique can be especially useful for document inspection and restoration as hidden markings can become visible in infrared.
Forensics, geology, meteorology, and many other sciences take advance of multispectral imaging to collect important data about the natural world as well as man-made objects. Devices capable of this type of imaging vary in size and complexity, including specialized devices mounted on satellites and telescopes that may be custom designed for specific applications. Learning to interpret multispectral images takes training and time, as people need to learn what various representations mean.
It is important to be aware that many multispectral images are presented in false color. Composite satellite images, for example, may have vivid and striking appearances, but they do not reflect what would be seen by the naked eye. Colors may be exaggerated or highlighted in order to stress particular features of interest and a note on the image may be included to indicate whether it is in true or false color.