A scanning beam time-resolved imaging system for fingerprint detection

A highly sensitive confocal scanning-beam system for time-resolved imaging of fingerprints is described. Time-resolved imaging is a relatively new for ensic procedure for the detection and imaging of latent fingerprints on flu orescent substrates such as paper, cardboard, and fluorescent paint. Ordina ry fluorescent imaging of latent fingerprints on these surfaces results in poor contrast. Instead, the specimens are treated with a phosphorescent dye that preferentially adheres to the fingerprint which allows time resolved discrimination between the fingerprint phosphorescence and the background f luorescence. Time resolved images are obtained by synchronizing the digital sampling of the specimen luminescence with the on-off cycle of the chopped illumination beam. The merit of this technique is illustrated with high co ntrast images of fingerprints obtained from the fluorescent painted surface of a Coke(TM) can.