First demonstration of sub-mm wave radiometry for security scanning

A contract by GSTP has developed detector and imaging technology for submillimeter wave band and, for the first time ever, tested it on people carrying different objects under their clothes. 

Conducting radiometric imaging at submillimeter wave frequencies is vital for astronomical imaging, especially mapping the cosmic microwave background. But this technology can also be found on the ground, at security screenings.

To date,  the systems  used currently are limited by the number of detectors per imaging system due to cost. This activity, with VTT Millilab in Finland, wanted to improve this, by redesigning the system completely.

The activity led to the development of a startling number of new technologies including:

• a staring imaging system based on the focal plane of 8712 detectors;
• new detector arrays;
• a modified microfabrication process to increase the detector packing density;
• lens-based quasioptics based on a wide-angle double-Gaussian lens (to enable a wide field of view at close range);
• multiplexed electronics to read out the detector arrays;
• and cryogenics with quasioptical access.

As a last step, the activity analysed the performance  of the technology by using human test subjects. Carrying different test objects under different pieces of clothing to see if the images could detect them. They were able detect objects from below all clothing types (t-shirt, sweater, sports jacket, leather jacket), with dimensions down to 16 mm . 

The tests were the first-ever demonstration of using submillimeter wave radiometry for in-person security screening with a staring array without any optomechanical scanning.

Contract G617-171EE closed in July 2019.