Optical Coherence Tomography (OCT) provides fast, non-invasive, non-contact imaging of 3D surface and subsurface microstructure of materials providing stratigraphic information of objects. OCT offers a micrometre level resolution in the direction normal to the surface of an object and is well suited for the investigation of fine details of structures which moderately absorb infrared light, such as varnishes, glaze and paint layers and underdrawings of paintings, reverse paintings on glass, glazes on ceramics and faience, jade, historic glass and enamels, amber, rock art, parchment and paper etc. Images obtained by OCT are usually presented in the convenient manner of cross-sectional views, similar to microscopic images of sample cross-sections extracted from the object. If necessary, information of an entire volume (a cube) may be collected by combining a sequence of 100 – 1000 cross-sections across the surface. The major advantages of OCT are the ability to see the layers and microstructure below the object surface in a non-contact and non-invasive manner (intensity of light used for examination is in the order of a few milliwatts), rapid data collection with online display of images and no object preparation. Given the non-invasive nature of the technique, the number of measurements across the entire surface can be unlimited, making it possible to have a representative view of the whole object.
decorative arts, film, glassware, manuscript, mosaics, musical instrument, painting, photo
animal product, botanic collection, mineral, shell
ceramics, glass, pigments
binding media, glues, wood, varnishes, amber
The 850 nm Fourier domain OCT (NCU) comprises a broad-band light source made up of optically coupled super luminescent LEDs emitting in a band of 750-960 nm. The intensity of radiation at the object never exceeds 1.5 mW, and due to fast scanning is focused at any given spot on the object for 45 μs...