A study conducted for a friend using some excavated roman artifacts. The idea was to see, if deteriorated paint/lead glacing could be made visible after thousands of years, using these new high powered Nichia 4 dice UV LEDs (365nm + 385nm).
[click on image to see a larger one]
1) Visible light shot:
2) FL (385nm Nichia UV LED induced visible fluorescence):
3) FL (365nm Nichia UV LED induced visible fluorescence):
4) differential 1 - 2
5) differential 1 - 3
Interestingly enough, the induced fluorescence was quite different, although the LED emissions are just 20nm apart. A comparison was done to see, if a nearly monochromatic excitation using UV LEDs would provide a different result than a wide band filtered Xenon lamp (300-400nm) excitation, which was not the case (not shown here).
Stay tuned, more will follow on that fascinating subject...
More info on this very interesting field may be found on my site http://www.pbase.com/kds315/uv_photos