Research teams at The University of Texas at Dallas (UT Dallas) and Oklahoma State University have developed a terahertz (THz) imager microchip for industrial and other applications that helps the viewer “see” through packaging and other obstacles, such as fog, snow, dust, smoke, and fire.
Terahertz imaging is classified as a nondestructive evaluation technique that uses THz waves to assess opaque objects. Terahertz imaging has proven useful in material analysis, quality control, and security screenings. Numerous applications for terahertz imaging have been identified in the aerospace, automotive, biomedical, industrial, security, and other industries. Terahertz imaging can be used to inspect the physical structure of multi–layered objects, as well as identify structural defects and abnormalities.
The terahertz imager is the fruit of 15+ years of work by Dr. Kenneth K. O, professor of electrical and computer engineering at UT Dallas, and his team of students, researchers, and collaborators. The terahertz imager includes a microchip and a reflector. The reflector’s purpose is threefold and serves to increase imaging distance and quality, as well as reduce power consumption by more than 100x. The microchip emits radiation beams that travel through obstacles. The beams bounce off objects and back to the microchip, where pixels pick up the signal and produce images. The radiation beams are in the THz range (430 GHz) of the electromagnetic spectrum “from pixels no larger than a grain of sand,” explained Kim Horner, communications manager for UT Dallas.
Using a 430 GHz signal, instead of 2.4 and 5.8 GHz, for example, allows the viewer to “discern smaller objects spaced smaller distances apart,” Dr. O said. If the terahertz imager is being used to differentiate between two similarly sized objects, then distance comes into play.
“The size depends on how far away the object is from our imaging module. At 3 meters, we can distinguish [between] objects that are about 3 centimeters [in size]. At 10 meters from the imager, we expect we will be able to distinguish objects that are about 10 centimeters in size and [distance] apart.”
Though the microchip looks delicate, the team’s work indicates that this type of circuit can be fabricated using low–cost quad flat no–lead packages, which are leadless packages that provide moderate heat dissipation in printed circuit boards.
“Once packaged, [the terahertz imager microchip] could be used like any other electronic components for commercial applications subject to shock limits,” Dr. O said. “The performance [of the terahertz imager microchip] is expected to degrade as the temperature is increased. The temperature impact and keeping cool are clearly a subject of further study.”
Dr. O and his team used a type of integrated circuit technology known as CMOS to design the terahertz imager. Using CMOS makes the imager more affordable, as it is widely used to manufacture consumer electronics devices.
An additional advantage of the UT Dallas terahertz imager is its smaller footprint. Researchers from the Massachusetts Institute of Technology developed a similar technology that uses 2.4 and 5.8 GHz Wi–Fi signals to “see” through obstacles, including walls, with a wavelength that is 100x larger than the UT Dallas system. This means that if the viewer wants the same raw resolution, the UT Dallas system is 100x smaller and produces the same image quality.
Currently, the UT Dallas research team is developing a terahertz imaging device for industrial applications with the ability to produce imaging up to 20 meters away. Dr. O has said that the technology can be adapted to other applications and uses where reduced visibility is a factor, such as drivers in a snowstorm or firefighters battling smoke and fire.
While the use of terahertz imaging in medical applications continues to expand, especially in the early detection and treatment of skin, breast, and colon cancer, the new terahertz imager microchip from UT Dallas is not currently indicated for medical use because the 430–GHz signals would be absorbed by the skin. However, Dr. O indicates that one promising medical application would be to monitor dehydration.