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Anti-stokes fingerprint illuminated with IR laser 

A extensive study into latent fingermark detection, on what have traditionally been known as ‘difficult’ surfaces, with anti-Stokes powders (also known as up-converter particles) produced by scientists and researchers at UTS has successfully demonstrated the potential of the new Foster + Freeman Crime-lite ASV illumination system

The study, conducted at the Centre for Forensic Science at the University of Technology Sydney and published in the April 2011 volume of the Forensic Science Internaional (FSI) journal, explores the potential of a commercially available anti-Stokes powder (NaYF4:Er,Yb) when used to visualise fingerprints on a selection of surfaces and illuminated at 980nm using the Crime-lite ASV.

Anti-Stokes can be described as being a photoluminescent process that is the reverse of standard fluorescence. Instead of short wavelength light being converted to longer wavelengths, the anti-Stokes effect converts invisible infrared illumination to shorter wavelengths visible to the eye. This almost completely eliminates the background leaving only the fingerprint visible. Excellent results can be obtained with fingerprints on 'busy' multicoloured backgrounds and on materials which fluoresce at similar wavelengths to common fingerprint treatments.

Researchers at UTS were able to produce a succession of prints on ‘difficult’ surfaces with the fingermarks appearing as bright regions on a dark background illustrating, for the first time, the potential of anti-Stokes powders to develop fingermarks with high contrast on substrates that would otherwise prove difficult.

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Crime-lite ASV: Anti-Stokes laser viewing enclosure for the illumination of fingermarks