The Encyclopedia of Archaeological Sciences || Multispectral and Hyperspectral Imaging

摘要： In the field of archaeology (and heritage in general), many documentation and examination methods are based on imaging techniques that characterize and depict artifacts in a nondestructive and mechanically noninvasive way. Multi- and hyperspectral imaging (together denoted spectral imaging) are two possible forms of such noninvasive imaging. Both are based on the detection of reflected or emitted optical electromagnetic radiation, the latter being defined as electromagnetic waves with wavelengths between 10 nm (0.01 μm) and 1 mm (1,000 μm). This detection can be better understood when considering that optical digital imaging usually generates a signal that is the outcome of a three-variable process: electromagnetic radiation of a radiation source falls onto the object; this radiation is partly absorbed, transmitted, and reflected by the object, with the interaction being wavelength dependent; and the imager detects and digitizes the incoming radiance in specific spectral regions. Spectral imaging extends traditional trichromatic digital camera approaches by capturing data in at least four different spectral bands, with hyperspectral imaging featuring higher spectral resolution and more contiguous spectra. Applications include archaeological prospection, color-accurate documentation, material identification, and enhancing the reading of old documents. Drawbacks involve data quantity, noise proneness, and reliance on specialized hardware and software, with future research focusing on active systems like multi-wavelength laser scanners.