LDS implements spectrum processing algorithms and various processing, data fusion and filtering methods including RAMAN, UV-RAMAN, luminescence and Laser-Induced Breakdown Spectroscopy (LIBS).
Raman spectroscopy is an analytical tool for analyzing molecules properties. Its theoretical origins roots to Prof. C.V, Raman of India an Indian physicist whose work was influential in the growth of science in the world. Raman Spectroscopy is a non-destructive light scattering measurement technique, which provides extremely rich chemical and structural information of the sample. The existence of slight wavelength shift between the inelastically scattered photon wavelength and the stimulating photon wavelength is related to the sample molecule “finger-print” properties, and provides the chemical and structural information of the sample.
In Raman Spectroscopy, a laser source illuminates a spot on the surface being scanned, whether vehicle, drum, left-behind luggage, etc. Any explosive residue present on the object produces Raman scattering. Then, the scattered light is collected by a telescope and analyzed by a spectrometer and detector. A spectral fingerprint (i.e., the Raman spectrum) is generated in as little as 5-20 seconds. Finally, the spectrum is compared with previously recorded Raman spectral analysis to identify suspicious substances.
Laser-induced breakdown spectroscopy (LIBS)
Laser-induced breakdown spectroscopy (LIBS) employs a powerful laser beam, most often from a pulsed Nd:YAG laser, with an emission wavelength of 1064 or 532 nm, transmitted in a single, powerful pulse, less than 10 nanoseconds duration, packing 50 to 100 millijoules of energy, focused onto the sample material. The impact generates a plasma spark at the surface, with typical temperature in the plasma reaching 10,000 K. At that temperature the species present are exited into electronically excited atoms and ions. As the excited species decay, they emit radiation at wavelengths that are distinct to each chemical element, typically in the ultraviolet to near-infrared range. Light from the spark is gathered by a spectrometer and analyzed by a computer.