Development of a cost-effective remote explosives detection system based on Raman spectroscopy

Abstract

Near real-time detection and identification of explosives from safe distances remains a challenging defense technology that requires both scientific and engineering perspectives in the design and development. Here, we demonstrated a cost-effective standoff Raman system for detecting explosive materials from distances up to 30 m. The optical system consists of an 8-inch Schmidt–Cassegrain telescope for Raman scattering light collection, while a compact grism was used to generate Raman spectrogram. An image intensifier from night vision technology was incorporated for amplifying the extremely weak Raman spectrum to a level detectable by a thermoelectric-cooled CMOS camera. A nanosecond pulsed laser at 440 nm with peak power of 0.41 MW was used as an excitation source, and the standoff Raman measurement was performed for test samples, including Ba(NO3)2, BaSO4 and NaNO3 powders. The spectral resolution and signal-to-noise ratio performance of the system were evaluated for the samples placed at distances of 10, 20 and 30 m. It was found that the standoff Raman system can resolve such Raman spectra, showing clear characteristic peaks of Ba(NO3)2, BaSO4 and NaNO3 at 1,045.9, 986.4 and 1,066.5 cm−1, respectively. These spectrum results agree well with the Raman spectra obtained from a standard close-range Raman system.