Terahertz energy, with its ability to penetrate clothing and non-conductive materials, has held much promise in the area of security scanning. Millimeter wave systems (300 GHz and below) have been widely deployed. These systems have used full two-dimensional surface imaging, and have resulted in privacy concerns. Pulsed terahertz imaging, can detect the presence of unwanted objects without the need for two-dimensional photographic imaging. With high-speed waveform acquisition it is possible to create handheld tools that can be used to locate anomalies under clothing or headgear looking exclusively at either single point waveforms or cross-sectional images which do not pose a privacy concern. Identification of the anomaly to classify it as a potential threat or a benign object is also possible.
Irl N. Duling, Irl N. Duling,
"Handheld THz security imaging", Proc. SPIE 9854, Image Sensing Technologies: Materials, Devices, Systems, and Applications III, 98540N (26 May 2016); doi: 10.1117/12.2224095; https://doi.org/10.1117/12.2224095