Development of a Two-Beam Terahertz FMCW Walk-Through Body Scanner for Seamless Security Screening

We have developed a body scanner that can measure both the front and back sides of a pedestrian walking at 4 km/h using a single 300 GHz frequency-modulated continuous-wave (FMCW) radar and scanning optical system. While maintaining a simple system architecture, the design builds upon a previously proposed method, with a novel implementation of a second beam to enable acquisition of the pedestrian's back side in a single pass. We have evaluated the position dependence of the lateral resolution and telecentricity, satisfying the requirements for both sides. We have also introduced the new method so as to perform three-dimensional rendering of both sides in a short time using their intensity images. Furthermore, we have newly evaluated the sweep time dependence of the noise level of the range profile, by changing the frequency sweep time of the signal source of the FMCW radar, digital direct synthesizer, from 10 μs to 10 ms.