Our Technology–Multispectral Imaging and RTI

WSRP’s most recent work has involved the combination of Multispectral Imaging and RTI. Multispectral imaging entails capturing a sequence of images in different wavelengths across the light spectrum, including ultraviolet and infrared. As we have shown, RTI technology provides the capacity to view in detail the textured surface of an artifact. The combination of the two allows the user to see data beyond the visible light spectrum, together with the texture on the surface of the manuscript or other object. Multispectral imaging can be helpful with objects that utilize ink or pigments. This is because various inks or pigments react to wavelengths differently and this property can be used to enhance contrast in a composite image to see data not apparent to the unaided eye. This 16th century manuscript page has been erased, and very little of the ink remains, making it difficult to read. RTI can be useful, because even if the ink is gone, the parchment still retains the impressions of the pen that was used to make the letters. Note that, even without enhancement, the texture of the writing can be seen as the “flashlight” moves around the page. This evidence of texture can be combined with spectral data in which images from across the spectrum, including ultraviolet and infrared, can be mapped to the normal red, green and blue wavelengths that can best be seen by the human eye. Further, pseudocolor images can be produced by creating principal component images and manually selecting the two or three most useful images to place in the red, green, and blue channels of an RGB image. The pseudocolor combination makes it easy to see at a glance the difference between the letters and the background, or, in some cases, the difference between two layers of ink. For more information on this technology see the discussion on “Spectral RTI Technology” at http://palimpsest.stmarytx.edu.