Method: Imaging of cross sections of subsurface, semi-transaprent structures
Organization
Nicolaus Copernicus University
Alternative labels
OCT
SdOCT
Description
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 a convenient manner with cross-sectional views, similar to microscopic images of sample cross-sections extracted from the object. If necessary, information on 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.
Techniques
Optical coherence tomography (oct)
Type
Analysis Method, Conservation Support
Version
1.0
Parameters
Type: Axial resolution in air
Unit: micrometre
Value: 3.3
Type: axial resolution in varnish (n=1.5)
Unit: micrometre
Value: 2.2
Type: lateral resolution
Unit: micrometre
Value: 13
Type: central wavelength
Unit: nm
Value: 850
Type: wavelength range
Unit: nm
Value: 210
Type: working distance
Unit: mm
Value: 43
Type: maximum light power at the object
Unit: mW
Value: 1.2
Type: maximum fluency
Unit: mJ/cm2
Value: 30
Type: lateral scanning range
Unit: mm
Value: 17
Type: axial imaging range
Unit: mm
Value: 1.4