Revolutionizing Airport Security: The Impact of Walkthrough Screening Systems

A new security screener that people can simply walk past may soon be coming to an airport near you. In 2024, U.S. airports nationwide began adopting HEXWAVE—a commercialized walkthrough security screening system based on microwave imaging technology developed at MIT Lincoln Laboratory—to satisfy a new Transportation Security Administration (TSA) mandate for enhanced employee screening to detect metallic and nonmetallic threats.

The TSA is now in the process of evaluating HEXWAVE as a potential replacement for metal detectors to screen PreCheck passengers.

Typically, when you arrive at an airport security checkpoint line, you place your carry-on items on the conveyor belt, remove your shoes and any metallic items, and enter a body scanner. As you hold still for a few seconds with your feet spread apart and your arms extended over your head, the scanner creates a generic, featureless 3D body outline revealing any metallic or nonmetallic concealed weapons or other prohibited items.

Requiring individuals to stop, remove clothing and belongings, and pose for scans impedes traffic flow in airports and other highly populated venues, such as stadiums, shopping malls, mass transit stations, and schools.

To enable more efficient screening of unstructured crowds and ensure public safety, the Department of Homeland Security (DHS) Science and Technology Directorate (S&T) sponsored Lincoln Laboratory to prototype a high-resolution imaging system capable of scanning people and their belongings as they walk by.

This R&D effort was conducted as part of S&T’s Surface Transportation Explosive Threat Detection Program, which aims to provide the surface-transportation end-user community (e.g., mass transit) with a layered and integrated capability to detect threat items at the speed of the traveling public.

The Laboratory’s prototype microwave imager, which consists of a set of antennas installed on flat panels, operates under the same fundamental principle as existing body scanners. Low-energy radio waves (less powerful than those transmitted by a cell phone) are transmitted from antennas toward a person’s body and reflect off skin and any hidden objects; the reflected waves return to the antennas and are processed by a computer to create an image, which security personnel then review to identify any potential concealed threats.

The novelty of the Laboratory’s invention lies in its ability to discreetly handle a constant stream of subjects in motion, measuring each subject very quickly (within tens of milliseconds) and reconstructing 3D microwave images of each subject at a video rate.

To meet these challenging requirements, the laboratory team developed a cost-effective antenna array and efficient image-reconstruction algorithms. Compared to existing systems, the Laboratory’s 3D microwave imager runs 100 times faster using the same computing hardware.

In 2017, the team demonstrated the prototype’s ability to detect various simulated threat items at varying distances on a rail platform at the Massachusetts Bay Transmit Authority (MBTA) Emergency Training Center in Boston, Massachusetts.

“The goal of our work is to provide security staff with more effective tools to protect public spaces. To that end, microwave imaging technology can quickly and unobtrusively provide visibility of items carried into a venue,” says William Moulder, who led the technology’s development at Lincoln Laboratory.

Provided by
MIT Lincoln Laboratory