STAND-OFF DETECTION OF HAZARDOUS SUBSTANCES SUCH AS EXPLOSIVES AND COMPONENTS OF EXPLOSIVES

摘要

In determining whether an object (3) contains a substance or molecules of a specific kind such as a hazardous substance of some kind, for example an explosive or a component of such a substance, the object is illuminated with light of a definite wavelength from a light source (1) and the light scattered by the object is analysed to obtain a Raman spectrum. The light scattered by the object is then collected and concentrated using an optical system (7) and analysed by a spectrometer (5). To obtain a high selectivity, sensitivity and /or accuracy in the determination, light is emitted from the light source with a plurality of different wavelengths around a wavelength that agrees with an absorption wavelength of the substance or the molecules of said one kind. Raman spectra are produced for each such wavelength and the spectra are then analysed (19) to determine whether the object contains the substance or molecules of said one kind. The wavelength of the emitted light can be changed with a predetermined step around the absorption wavelength.