Multispectral and Hyperspectral Imaging

Since the invention of photography, a variety of approaches have made noninvasive imaging for cultural heritage applications possible. Multi‐ and hyperspectral imaging (together denoted spectral imaging) are two techniques that evolved from conventional color photography, having overcome its spectral limitations. Instead of imaging in three broad spectral bands, multispectral imaging acquires data in up to ten more or less equally wide and nonoverlapping spectral bands. Hyperspectral imaging goes beyond the multispectral approach by generating images in tens to hundreds of narrow, contiguous (i.e., adjacent but not overlapping) spectral bands. Most spectral imaging techniques are limited to the optical electromagnetic spectrum and acquire the reflected portion of the radiation that is used to illuminate the scene. However, imaging the emitted thermal radiation or active techniques based on laser scanners do exist as well. In cultural heritage, all these techniques are used to gain a better, noninvasive insight into the chemical and physical properties of the object(s) under investigation.