Determining the nominal body contour image using wideband millimeter-wave radar for characterizing person-worn threats

Abstract

Precise characterization of concealed person-worn objects will speed up the passenger screening process by reducing the rate of nuisance alarms, while also enhancing the airport security imaging systems. This paper presents an automatic, real-time method for wideband millimeter-wave radar identification of the nominal surface contours of the human body – even with affixed foreign objects or when a segment of the body cross-section is not captured by the radar – without relying on the body's bilateral symmetry. The developed method is verified experimentally when applied to the actual images generated by a laboratory airport scanning prototype developed recently by the US Department of Homeland Security (DHS). Our method uses the noisy collection of radar cross-section reflectivity data to extract the main contours and estimates the nominal body surface cross-sections through fitting a small-term Fourier series of circumferential variation. This is a necessary step for accurate characterizing of concealed terrorist threat objects affixed to the body.

Fast, Fully-Automatic Characterization of Metallic and Water-Based Threat Objects for Millimeter-Wave Personnel Screening Systems

“…Even with a high-resolution screening radar, the precise distinction of the boundary of the body surface is a challenging task. The authors have already developed an automatic, realtime algorithm for wideband mm-wave estimation of the nominal surface contours for different regions of human body [40][41][42]. Given an indication of the presence, centroid, and extent of an anomaly attached to a subject's body as established by an automatic target recognition (ATR) preprocessor, the algorithm employs a small-term Fourier circumferential series to estimate the NBCs even in the presence of affixed foreign objects when a portion of the body cross-section may not be captured by the imaging radar.…”

“…In other words, the object's back surface often cannot be observed in the radar images. To resolve the challenges, we employ our previously established methods for contour extraction and estimation of the NBCs [40][41][42], in addition to two important observations: 1) the deformation of the surface contour in the reconstructed images due to conductive foreign objects with respect to the NBC is always seen as a protrusion rather than a depression; and 2) the average image reflectivity of the extracted contours is higher for the region with the affixed metallic or waterbased objects, compared to the NBC without the object.…”