Millimetre-wave thermography is used to image through the soles of shoes as proof of principle study into the application of such an approach for security inspection. Current airport security screening practice necessitates the removal of shoes prior to x-ray screening for potential threats or other concealments, for example explosive or explosive precursor materials; narcotic substances or small weapons. The authors demonstrate that thermography at ~250 GHz is able to reveal a variety of objects concealed within the soles of typical shoes, and that such an approach might be applied to rapidly screen passengers without necessitating the removal of their footwear.
2. Appleby, R. and H. B. Wallace, "Standooff detection of weapons and contraband in the 100 GHz to 1THz region," IEEE Transactions on Antennas and Propagation, Vol. 55, 2944-2956, 2007.
3. Kemp, M. C., "Millimetre wave and terahertz technology for the detection of concealed threats — A review," Proceedings of SPIE, Vol. 6402, 2006.
4. Agurto, A., Y. Li, G. Tian, N. Bowring, and S. Lockwood, "A review of concealed weapon detection and research in perspective," Proc. IEEE Int. Conf. MonE02 Networking, Sensing and Control, 443-448, 2007.
5. Salmon, N. A., "W-band real-time passive millimeter-wave imager for helicopter collision avoidance," Proc. SPIE, Vol. 3703, 28-32, Apr. 1999.
6. Owda, A. Y., N. Salmon, S. W. Harmer, S. Shylo, N. J. Bowring, N. D. Rezgui, and M. Shah, "Millimeter-wave emissivity as a metric for the non-contact diagnosis of human skin conditions," Bioelectromagnetics, Vol. 38, 559-569, 2017.
7. Harmer, S. W., S. Shylo, M. Shah, N. J. Bowring, and A. Y. Owda, "On the feasibility of assessing burn wound healing without removal of dressings using radiometric millimetre-wave sensing," Progress In Electromagnetics Research M, Vol. 45, 173-183, 2016.
8. Mann, C., "First demonstration of a vehicle mounted 250 GHz real time passive images," Proc. SPIE, Vol. 7311, 73110Q-1-73110Q-7, May 2009.
9. Appleby, R., P. Coward, and J. N. Sanders-Reed, "Evaluation of a passive millimeter wave (PMMW) imager for wire detection in degraded visual conditions," Proc. SPIE, Vol. 7309, 73090A-1-73090A-8, Apr. 2009.
10. Waldschmid, C., E. Topak, J. Hasch, R. Schnabel, R. Weigel, and T. Zwick, "Millimeter-wave technology for automotive radar sensors in the 77 GHz frequency band," IEEE Transactions on Microwave Theory and Techniques, Vol. 60, No. 3, 845-860, Mar. 2012.
11. Singh, S., "Explosives detection systems (EDS) for aviation security," Signal Processing, Vol. 83, No. 1, 31-55, 2003.
12. Lamb, J. W., "Miscellaneous data on materials for millimetre and submillimetre optics," International Journal of Infrared and Millimeter Waves, Vol. 17, No. 12, 1997-2034, Dec. 1996.
13. Yujiri, L., M. Shoucri, and P. Moffa, "Passive millimeter-wave imaging," IEEE Microwave Magazine, Vol. 4, No. 3, 39-50, 2003.
14. Goodman, J. W., Introduction to Fourier Optics, McGraw Hill, Jan. 2005.
15. Sinclair, G. N., R. N. Anderton, and R. Appleby, "Outdoor passive millimetre wave security screening," Proc. IEEE 35 Annual 2001 International Carnahan Conference on Security Technology, Oct. 2001.
16. Prasad, B. S., K. A. Prabha, and P. V. S. G. Kumar, "Condition monitoring of turning process using infrared thermography technique — An experimental approach," Infrared Phys. Technol., Vol. 81, 137-147, Mar. 2015.
17. Dietlein, C. R., E. Grossman, F. G. Meyer, X. Shen, and Z. Popovic, "Detection and segmentation of concealed objects in terahertz images," IEEE Transactions on Image Processing, Vol. 17, No. 12, Dec. 2008.
18. Andrews, D. A., D. O’Reilly, M. J. Southgate, N. D. Rezgui, N. J. Bowring, and S. W. Harmer, "Development of an ultra-wide band microwave radar-based footwear scanning system," Proc. SPIE Security + Defence, Vol. 8900, Oct. 2013.