1.56 Terahertz 2-Frames per Second Standoff Imaging

A Terahertz imaging system intended to demonstrate identification of objects concealed under clothing was designed, assembled, and tested. The system design was based on a 2.5 m standoff distance, with a capability of visualizing a 0.5 m by 0.5 m scene at an image rate of 2 frames per second. The system optical design consisted of a 1.56 THz laser beam, which was raster swept by a dual torsion mirror scanner. The beam was focused onto the scan subject by a stationary 50 cm-diameter focusing mirror. A heterodyne detection technique was used to down convert the backscattered signal. The system demonstrated a 1.5 cm spot resolution. Human subjects were scanned at a frame rate of 2 frames per second. Hidden metal objects were detected under a jacket worn by the human subject. A movie including data and video images was produced in 1.5 minutes scanning a human through 180 of azimuth angle at 0.7 increment.
Sponsored in part by the Department of Homeland Security. Prepared in collaboration with the Spire Corporation, Bedford, Ma and the National Ground Intelligence Center, Charlottesville, VA. Presented at Integrated Optoelectronic Devices 2008 in San Jose, CA on 19-24 Jan 2008. Published in Terahertz Technology and Applications, Proceedings of SPIE v6893, paper 68930j, 14 Feb 2008.