What is hyperspectral imaging?

Hyperspectral imaging is the capture and processing of an image across a large number of wavelengths. While multispectral imaging can evaluate an image in three colors (red, green, and blue), hyperspectral breaks it down into dozens or hundreds of colors. There are two broadly defined technology areas that have enabled the development and advancement of hyperspectral imaging: the development of cheap, high-quality diffraction gratings and advances in multi-dimensional data processing. To see how these technologies have improved the state of hyperspectral imaging, it is necessary to take a brief look at how most current systems operate. Most companies offering instruments or services involving hyperspectral imaging have unique, proprietary approaches that distinguish them from one another. Most hyperspectral imaging systems consist of imaging optics, a narrow slit, a diffraction grating, and a focal plane array (FPA) detector. The image is projected through the slit onto the diffraction grating, where the light is split into discrete, physically separated wavelengths before being projected onto the focal plane array. One dimension of the FPA corresponds to the wavelength of light, as separated by the diffraction grating. The other dimension corresponds to the "vertical" position along the slit. At each XY coordinate, a pixel is energized to some level, based on the intensity of the light at that position and wavelength. What ultimately results is a three-dimensional array (slit position, wavelength, and intensity) for each narrow slit width. By indexing the slit width, the entire image can be mapped into a four-dimensional array. This indexing can be done by moving the slit or by moving the sensing device.