Color is expressed in terms of electromagnetic wavelength frequencies. Only a limited range of these frequencies, called the visible spectrum, is visible to the human eye. Humans see color mostly in three bands of frequencies: long wavelengths are perceived as red, medium wavelengths are perceived as green and short wave lengths are perceived as blue.
Light Spectrum
Unlike the human eye, spectral imaging distinguishes many spectral bands. A hyperspectral camera records a series of consecutive images, where images represent progressively higher wavelengths, including long wavelengths invisible to the human eye. The images in this series are combined into a data cube containing the pixel values of each pixel in each wavelength. Each image in the data cube can be converted into a greyscale image where each pixel in the image represents light intensity. These greyscale images, particulaly those of longer wavelengths (infrared images) allow researches to detect hitherto unseen details which may, for example, complete and enhance the interpretation of ancient inscriptions.
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Hyperspectral Camera |
Data Cube |
Many Iron Age inscriptions were found in Israel. The majority of these inscriptions were written in ink on ceramic shrads (refered to as ostraca). Without extremely careful handling and special preservation conditions, the ink on the shrads fades rapidly, often blurring the inscription, and sometimes rendering it unreadable. In order to help preserve and document the inscriptions, our laboratory uses advanced hyperspectral imaging technologies to produce high quality images of the artifacts and inscriptions.
Infrared Image of an Ostracon