Standoff imaging of chemicals using IR spectroscopy

Here we report on a standoff spectroscopic technique for identifying chemical residues on surfaces. A hand-held infrared camera was used in conjunction with a wavelength tunable mid-IR quantum cascade laser (QCL) to create hyperspectral image arrays of a target with an explosive residue on its surface. Spectral signatures of the explosive residue (RDX) were extracted from the hyperspectral image arrays and compared with a reference spectrum. Identification of RDX was achieved for residue concentrations of 20 μg per cm 2 at a distance of 1.5 m, and for 5 μg per cm 2 at a distance of 15 cm.