The photoluminescence detection of latent fingerprints has in the last twenty years become a very successful methodology. However, there are still all too many items that defy processing because of intense background fluorescence from the article itself Time-resolved approaches involving gated (time-domain) and phase-resolved (frequency-domain) imaging are being explored to permit background suppression. From the instrumentation perspective, gated imaging is mature. Although photoluminescence lifetimes of microsecond order and even shorter are amenable in principle to gated fingerprint imaging, practicality considerations generally call for lifetimes of millisecond order. The pertinent fingerprint treatments, largely involving lanthanide-based strategies that mostly utilize europium complexes, leave much to be desired for detection on porous surfaces of fingerprints that are not fresh, however. Moreover, while phase-resolved imaging systems have been operational for some time in cell microscopy, for instance, and instruments for fingerprint work are under development, these systems are suitable for photoluminescence lifetimes of nanosecond order, but the needed companion fingerprint treatment strategy has yet to be developed.
USPTO Backgrounds
USPTO Backgrounds