Concealed object detection by far infrared sensing of the acoustic phase

In this contribution we present a novel far infrared technique that is capable to detect concealed objects of virtually all materials. In our approach, we detect the acoustic phase of the objects when they follow a driven oscillation. This acoustic phase can be measured inferferometrically with continuous wave gigahertz radiation or by time resolved terahertz techniques. In both cases objects can be located behind several layers of textiles (Buersgens et al., 2007; and Chen and Kaushik, 2007). The presented technique gives no insight into the item´s material properties. It exclusively shows whether or not an object is concealed, which is the most relevant information for many sensing applications.