What if there were a handheld device that could help a technician look at the surface of an airplane fuselage to detect corrosion and cracks beneath the paint? Imagine if this device could eventually be optimized so that a dermatologist could move it over a patient’s skin lesion and use the images it produces to identify potential skin cancer.
Those are just two of the applications that IEEE Fellow Reza Zoughi hopes to develop with the portable and real-time high-resolution microwave camera that he and his colleagues have been working on over the last decade. In the current bench-top prototype, a transmitter generates a microwave signal, which passes through a nonmetallic object while a collector on the opposite side picks up the scattered signals and displays the resulting images onto a computer screen in real time.
A professor of electrical and computer engineering at the Missouri University of Science and Technology, in Rolla, Zoughi has spent more than two decades developing instruments and methodologies that apply microwaves and millimeter waves to evaluate properties of materials, composites, and structural system without causing any damage to them, known as nondestructive evaluation. For his groundbreaking work in the field, he received the 2011 IEEE Joseph F. Keithley Award in Instrumentation for “contributions to microwave and millimeter wave measurement techniques for nondestructive testing and evaluation.”
Zoughi and his team of researchers at Missouri S&T’s Applied Microwave Nondestructive Testing Laboratory have spent the past decade designing and developing their camera to make it faster and more portable while improving its resolution and sensitivity. A video describing the camera’s operation can be found on the laboratory’s website.
DETECTING HIDDEN DAMAGE
Zoughi's technology has potential applications in examining bridges, buildings, aircraft, and other vehicles for a variety of defects and anomalies. Although microwaves cannot penetrate metallic objects, they can penetrate a variety of dielectric-based composites and non-metallic materials of which some components of aircraft and spacecraft are made, as well as concrete and wooden structures. The camera may also be optimized to help homeowners see through wood to spot termites and their damage.
The current model of the camera is composed of basically two parts: a microwave transmitter, which is pointed at an object, and a collector grid of 576 resonant switched slot antennas that sits on the other side of the object. The collector detects the scattered microwave field from the object and produces approximately 30 images per second.
The next step, Zoughi says, is to find a way to place the transmitter and receiver on the same side of the object so users can move the device along a surface and capture images the way a video camera does. He also wants to make the technology wireless so that users can take the device to remote areas and transmit images from anywhere in the world.
GOING SKIN DEEP
Microwaves don’t penetrate deep inside the body the way X-rays do because they’re absorbed by moisture—so Zoughi’s device could not help doctors check for broken bones or damaged muscle tissue. It could potentially help doctors look just beneath the surface to check for skin cancer or monitor how well a burn is healing.
“Normal skin and tumor lesions have different biophysical properties, and the high-quality images created by microwaves can detect those differences,” Zoughi says. “Used properly, the tool has the potential to distinguish between a blemish and a cancerous tumor.”
He notes that because the microwaves his devices use are non-ionizing compared to X-rays, and the imaging uses very low levels of power, it would be safe for both patient and technician. Medical professionals could use his device to, for example, see through a wound dressing and monitor a patient’s burn without having to remove bandages. And in areas where specialists are not available, rescue workers could use the device to record a patient’s surface wounds and transmit the data over the Internet to help diagnose and treat the patient.
YEARS IN THE MAKING
The idea for a handheld microwave camera came to Zoughi in 1998 while he was on sabbatical at École Supérieure d’Électricité (Supélec), in Gif-sur-Yvette, France. Researchers there had built the first real-time microwave camera using modulated scattering technique.
“With their camera you had to put the object you wanted to observe in water—which is not really practical for nondestructive testing applications,” Zoughi says.
“However, it demonstrated the potential to develop into a useful handheld and portable device,” he says. “I knew that when device and computer technology advanced, higher frequency waves could be used to get better resolution and faster images and then it would have a great number of applications.”
Zoughi and a team of researchers at Missouri S&T began working on their camera a few years later. In 2007 they finished the first prototype. With sufficient funding, he says, such cameras might be on the market within the next few years.
Nondestructive evaluation wasn’t always the focus of Zoughi’s research. After receiving bachelor’s, master’s, and doctoral degrees in electrical engineering from the University of Kansas in Lawrence, where he concentrated on microwave and radar remote sensing, he became a faculty member in the electrical and computer engineering department at Colorado State University in Fort Collins from 1987 until 2001, when he left for Rolla.
“I didn’t know anything about nondestructive evaluation until I got to Colorado State,” he says. After attending several conferences on the technique, he realized that very few, if any, researchers were using microwaves for nondestructive evaluation.
“A professor I worked with said, ‘You know, Reza, if you use your knowledge of radar remote sensing and apply it to nondestructive testing, then you could have a niche,’” Zoughi says. “And he was right.”