For those that remember that remarkable little scanner/computer/recorder/analyzer from the Star Trek television series, it seemed that there was nothing you could point it at and not get an instant readout of anything and everything about the object in question -- including what was inside. While the tricorder's operation is clouded in TV effects gimmickry, it was obvious that its sensors spanned just about any and every electromagnetic frequency known to man in the 20th century, and a few new ones known to the 23rd.
In true-life-imitates-art style, researchers at the University of Texas at Dallas (UT Dallas) have designed an imager chip that could turn cameras and mobile phones into devices that can see through walls, wood, plastics, paper, and other objects. What makes this possible is the frequency of electromagnetic waves to which the imager is sensitive.
Dr. Kenneth O, professor of electrical engineering at UT Dallas and director of the Texas Analog Center of Excellence(TxACE), and his team created a new complimentary metallic-oxide semiconductor (CMOS) sensor similar to the type used in cameras and cellular phones, except this sensor works in the terahertz (THz) region of the electromagnetic spectrum. The terahertz frequencies, or T-waves as they're called, fall between the microwave frequencies and the infrared light spectrum. They exhibit characteristics similar to both radio and light waves, which makes developing an imaging sensor for those frequencies difficult. Like radio waves, T-waves can penetrate objects. The degree of penetration depends upon the material from which the object is made and the frequency of the terahertz light source. This lets the researchers use the safe, non-ionizing radiation of the terahertz wavelengths as a form of x-ray to see into and through objects.
Dr. O states, “We've created approaches that open a previously untapped portion of the electromagnetic spectrum for consumer use and life-saving medical applications. The terahertz range is full of unlimited potential that could benefit us all.”
The biggest problem plaguing THz use has been the development of an imaging sensor that didn't need a laboratory full of equipment to work. Current CMOS imagers are sensitive to visible light, and are used as the "camera" element in many consumer devices including computers, smartphones, and game consoles. By using a new CMOS manufacturing technique, the UT group was able to create a CMOS imager sensitive to THz frequencies.
“CMOS is affordable and can be used to make lots of chips,” Dr. O said. “The combination of CMOS and terahertz means you could put this chip and receiver on the back of a cellphone, turning it into a device carried in your pocket that can see through objects.” Right now the focus is on distance ranges of four inches or less due to privacy concerns. But even that limited distance opens new doors for medical and health applications, industrial quality control, environmental monitoring, and high-speed communications.
“There are all kinds of things you could be able to do that we just haven't yet thought about,” said Dr. O.
The article "Shine the Light Fantastic" in the March 18, 2010 edition of MACHINE DESIGN offers additional information on terahertz imaging technology.