Oldal 34 [34]
Figure 1-21 shows an example of how the presence of ambient stray radiation can interfere
with the interpretation of luminescence phenomena. The UV-induced luminescence image
on the left Figure 1-21(a), was taken in the presence of some red ambient stray radiation.
Figure 1-21(b) shows the UV-induced luminescence of the same subject where the source of
this ambient stray radiation has been removed. Comparing these, it is clear that in Figure
1-21(a) the ambient stray radiation caused the dark areas in the image to appear lighter, the
areas of ‘blue’ luminescence around the figure appears purple and the ‘yellow’ luminescence
of the figure appears more orange.
The ambient stray radiation observed in images such as Figure 1-21(a), can be considered
as ‘background noise’ and, although this cannot be measured directly, it can be
mathematically reconstructed and removed from luminescence images by post-processing
methods, represented schematically in Figure 1-22 using a UV-induced luminescence image
as an example.
Figure 1-22. Schematic showing the correction of luminescence images for ambient stray radiation
using a UV-induced luminescence images image of a detail from a wall painting fragment from the
British Museum (Winged youth from the Tomb of the Nasonii, 1883,0505.5) as an example.
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NTH FRAMEWORK