Electronic Military & Defense magazine was developed for engineers, program managers, project managers, and those involved in the design and development of electronic and electro-optic systems for military, defense, and aerospace applications.
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Technology Figure 5: Visible image of a soldier wearing a typical camouflage uniform (left) and the thermal image of a scene with a sniper (right). obtained using this experimental scheme. Figure 3: Real-time detection images and their associated visible image before (top two images) and during (bottom six images) flare combustion. The different targets are labeled as follows: chemical 1 (blue), chemical 2 (yellow), and ammonia (red). Characterization Of Camouflage The camouflage material used in military uniforms is a combination of colors and patterns meant to match the predominant colors of the surrounding environment and trick the human eye. This approach is generally effective in the visible region of the electromagnetic spectrum, but not as much in the infrared region. For this reason, ther- mal imaging is a preferred approach for surveillance, as the human body emits considerable amount of infrared radiation compared to ambient-temperature objects in its environment. As such, intelligence agencies are mak- ing considerable investments in the design of composite camouflage material that reflects infrared radiation and mimics the thermal properties and infrared signature of natural objects like plants. However, soldiers in such uniforms can still exhibit some spectral signature that can readily be detected using hyperspectral imaging. Figure 4 shows a measurement setup used to carry out the characterization of different soldier uniforms. A piece of cloth is placed in front of one of the two blackbody sources (warm object), and its infrared signature is inferred from comparison of both blackbody sources. Typical spectra obtained during such experiments are illustrated by distinct spectral fea- tures corresponding to the uniform and can be effectively A representative field situation is illustrated in Figure 5, where a soldier uniform efficiently matches the color patterns of its surroundings but is still visible using thermal imaging. This collected infrared signature knowledge can be trans- lated into a recognition scheme during field experiments. In this situation, the warm human body acts as a blackbody source of radiation at the rear of the soldier uniform. Figure 6 demonstrates the efficiency of such strategy, in which a snip- er uniform can be easily distinguished from its surrounding and from a weapon. The collected spectra also reflect the spectral specificity of the uniform fabric in the scene. Figure 6: A distinct region of the scene, corresponding to the sniper's uniform, is represented in yellow (left) and the spectra of different pixels in the scene (right). The series of sharp signals between 1175 and 1300 cm-1 is associated with water vapor. Conclusion Standoff infrared hyperspectral imaging is a versatile tech- nique that intelligence agencies can use to gather strategic information previously unavailable. The technique provides more information than traditional thermal imaging in the characterization of military countermeasures. Real-time data processing makes field spectroscopy an accessible technique for military applications. And since the user can benefit immediately from the rich information provided by infrared hyperspectral imaging, the approach also improves efficiency of field trials. Finally, hyperspectral imaging can be used to characterize the spectral signature of soldiers' uniforms when used as a recognition scheme. Marc-André Gagnon is product-line manager for Telops. He earned his B.Sc. in chemistry from the Université de Sherbrooke and his Ph.D. in chemistry (spectroscopy) from the Université de Montréal. Figure 4: Determination of the spectral features of a soldier's uniform using remote sensing. 28 Electronic Military & Defense ■ www.vertmarkets.com/electronics