(Note: This is a fictionalized account of how a journalist may have covered the paper, “Three-Dimensional Millimeter-Wave Imaging for Concealed Weapon Detection” by David M. Sheen, Douglas L. McMakin, and Thomas E. Hall. None of the quotations below are true and must be interpreted as fiction only.)
Pacific Northwest National Laboratory
Researchers at the Pacific Northwest National Laboratory have developed the world’s first 3D millimeter-wave imaging systems to replace metal detectors at airport security checkpoints.
“Current airport security measures can only detect a limited number of targets made of metals, and are ineffective at identifying weapons made of say, plastic,” says a senior researcher involved with the study. “We aim to replace these systems with imaging systems that can see through fabric and form images of objects concealed under clothing.”
The technology they seek to leverage is millimeter-wave imaging, which uses signals from the frequency band of 30 – 300 GHz. Like X-ray scanners, their system forms images by transmitting and receiving signals that penetrate through materials like fabric. However, unlike X-rays, millimeter waves are non-ionizing, and thus pose no risk to the human body even on repeated exposure.
While the idea of using millimeter waves for imaging has been around for a few decades, the main limitations of previous systems have been cost and limited reconstruction quality. “Previously built systems have focused on using signals comprising of only single frequencies,” says the lead author. “However, most objects are three dimensional, and these systems fail to accurately reconstruct 3D objects along their depth. We have broken this limit by using multiple frequencies; this allows us to form fully-focused 3D images of targets.”
Their system operates by scanning a large 2D plane with an antenna array that radiates multi-frequency signals and measures the response of the target to them. The target image is then formed using a fast reconstruction algorithm based on the fast Fourier transform (FFT). A major advantage of their prototype is the speed of data collection and image reconstruction, and their prototype operates in near real-time by forming full images from the collected data in less than 10 seconds. “The data collection process may be further accelerated by employing an electronically switched 2D antenna array,” says the lead author. “While our prototype uses a linear array that is mechanically swept across the 2D plane primarily for cost and complexity concerns, with further miniaturization and shrinking transistor sizes, cost-effective technology for such wide-band 2D antenna arrays may soon be available.
“This will also enable commercialization of this technology,” he says. “We think our technology is a promising first step towards adopting better non-invasive security measures throughout the world.”
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