3-D Security Scanner May Be Too Effective for Air Travelers

	OTHER ARTICLES IN THE WTC SERIES Why Did the World Trade Center Collapse? Science, Engineering, and Speculation by Thomas Eagar and Christopher Musso Better Materials Can Reduce the Threat from Terrorism by Toni G. Maréchaux An Initial Microstructural Analysis of A36 Steel from WTC Building 7 by J.R. Barnett, R.R. Biederman, and R.D. Sisson, Jr. News & Update
Figure A. A three-dimensional image of a man is projected onto a computer screen as he passes through a holographic scanner.

Airline passengers who are willing to trade modesty for security may welcome a 3-D holographic scanner that, essentially, sees through clothing. Developed by the U.S. Department of Energy’s Pacific Northwest National Laboratory (PNNL) for the Federal Aviation Administration, the scanner can reveal hidden items, even non-metallic weapons, on airline passengers. Metal detectors used now cannot screen for plastic or ceramic weapons.

“To put it simply, the system rapidly scans objects and sends reflected signals into a high-speed image processing computer,” said Douglas McMakin, a PNNL engineer who helped develop the technology. “The computer produces a high-resolution 3-D image from the data.”

The wideband millimeter-wave holographic imaging system, called a Personal Security Scanner, uses ultrahigh frequency radio waves with relatively large wavelengths to penetrate clothing and other non-metallic objects (Figure A).

Although x-ray imaging systems might serve the same purpose, such systems would expose passengers to potentially harmful ionizing radiation. The holographic imaging system, with wavelengths in the same range as radar and satellite signals, is harmless, according to the Department of Energy.

The drawback to the system is that the people being scanned appear on a computer screen in an unclothed image. The PNNL has been working since 1997 to resolve the potential privacy issue by reprogramming the system to provide a view only of concealed items, not the person’s physical features.

As the technology exists now, the scanner could take two forms: either cylindrical or flat. With the cylindrical version, the person to be scanned would step onto a platform and an extended arm would circle them, providing an image at all angles. The flat scanner would involve two panels through which a person would walk to be scanned from both sides.

The aviation administration would like the process to take six seconds, according to Staci Maloof, a PNNL spokeswoman. Currently, the system requires about two seconds for the scan and another four to six seconds to process the image, Maloof said.

The research has been ongoing since 1989, with the FAA paying about $7.5 million for the work to date, she said. Although funding for the airport security project ended this spring, the lab, hoping to continue its work, responded this summer to a request for proposals by the aviation administration for further study.