Technology : Oh look, that must be his nose

时间:2019-02-27 08:12:04166网络整理admin

By Chris Watkins BEFORE you start piecing a jigsaw puzzle together, it helps to have a picture of the original and to know if any bits are missing. The same is true when restoring priceless mosaics—though the penalty for not being faithful to the original is that much greater. With this in mind, Leonardo Seccia and colleagues at the University of Bologna are creating an image processing tool kit that can draw up a detailed three-dimensional picture of the state of a mosaic before the restorers begin their task. The technique can reveal how badly damaged the artwork is, what harm previous restoration attempts may have done and even what materials were used in the original. Seccia and his colleagues are refining the image processing system while restoring the richly coloured mosaics at the 6th-century church of San Apollinaire Nuovo and a Neonian baptistry in the Italian city of Ravenna. The mosaics are composed of thousands of tiny tesserae—coloured glassy blocks—and depict scenes from the Byzantine era and the New Testament. The team shines lamps onto the mosaics, and then uses charge-coupled device (CCD) cameras to capture the reflected light. The researchers are interested in wavelengths extending through the visible range to the near ultraviolet and near infrared. CCDs convert light to digital signals that are fed to Matlab image processing software to create digital images at various wavelengths across the range. This allows the restorers to record the exact position of each tiny tile. The different degrees to which materials in the mosaic reflect heat and light reveal the inner structure of the artwork. This tells the restorers where layers of the plaster holding the mosaic have become detached, and where cement has been used in previous restoration attempts. Earlier studies of the church and baptistry revealed the materials used to create the mosaics. Seccia and his colleagues are using this data to verify the information their imaging system is producing. Because the process draws on previous conservation work it should provide a comprehensive and reliable digital database for future restoration work,