A multispectral imaging technique has been developed to detect and identify explosive particles, e.g. from a fingerprint,
at stand-off distances using Raman spectroscopy.
When handling IED's as well as other explosive devices, residues can easily be transferred via fingerprints onto other
surfaces e.g. car handles, gear sticks and suite cases. By imaging the surface using multispectral imaging Raman
technique the explosive particles can be identified and displayed using color-coding.
The technique has been demonstrated by detecting fingerprints containing significant amounts of 2,4-dinitrotoulene
(DNT), 2,4,6-trinitrotoulene (TNT) and ammonium nitrate at a distance of 12 m in less than 90 seconds
(22 images × 4 seconds)1. For each measurement, a sequence of images, one image for each wave number, is recorded.
The spectral data from each pixel is compared with reference spectra of the substances to be detected. The pixels are
marked with different colors corresponding to the detected substances in the fingerprint.
The system has now been further developed to become less complex and thereby less sensitive to the environment such
as temperature fluctuations. The optical resolution has been improved to less than 70 μm measured at 546 nm
wavelength. The total detection time is ranging from less then one minute to around five minutes depending on the size
of the particles and how confident the identification should be. The results indicate a great potential for multi-spectral
imaging Raman spectroscopy as a stand-off technique for detection of single explosive particles.