Harmless screening of humans for the detection of concealed objects

Multispectral screening systems are becoming more popular because of a wide range of applications. Terahertz and infrared radiation have unique properties applicable to the field of surveillance and security systems. One of the most significant applications of multispectral screening systems is the prevention of terrorist attacks. Visual detection of objects hidden under clothing of a person is one of the most challenging problems of threat detection. There are many solutions to the problem; however, the most effective utilize multispectral surveillance imagers. We investigate the possibility of harmlessly detecting objects covered by various types of clothing in three spectrums – visible, infrared and terahertz. The terahertz range of electromagnetic radiation has considerable potential to detect hidden objects because it penetrates clothes. The infrared imagers are also very useful in searching for concealed objects because infrared cameras can detect small temperature differences on the surface of clothing. Radiation from these three ranges is harmless to humans. We present the detection methodology using infrared and terahertz imagers as complementary sensors to provide image data for a multispectral threat detection system. Possible ways of using the results are also presented.