North Carolina State University News Services
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Media Contacts: Dr. Jan F. Schetzina, 919/515-3314 or [email protected]
Tim Lucas, News Services, 919/515-3470 or [email protected]
September 2, 1999
Scientists Develop New Digital Camera That Senses Only UV Light
FOR IMMEDIATE RELEASE
Scientists and students at North Carolina State University have teamed with researchers at the Night Vision Laboratory at Fort Belvoir, Va., and the Honeywell Technology Center to demonstrate the world's first digital camera that senses only ultraviolet light.
The prototype camera was developed in NC State's Solid State Physics Laboratory under the direction of Professor Jan F. Schetzina. The camera's first images -- of a ultraviolet light-emitting sign reading "NCSU" -- and a peer-reviewed scientific paper describing the camera are being published worldwide Thursday, Sept. 2, on the Internet at http://nsr.mij.mrs.org/.
As the technology becomes more fully developed in coming years, scientists anticipate it will have a wide range of practical uses, from national defense to environmental monitoring.
Ultraviolet (UV) light has shorter wavelengths than visible light. It is sometimes called "black light" and is used to excite visible fluorescence in materials such as rocks or glow-in-the-dark paints. Invisible to the human eye, UV light is emitted by many objects, including rockets during their boost stage, other flame-producing sources such as soldering and welding equipment, and astronomical objects like the sun and stars.
The ultraviolet digital camera Schetzina and his colleagues have developed and demonstrated employs a new semiconductor material called aluminum gallium nitride. Special structures of this material are fabricated into small cells called photodiodes that act like miniature solar cells, except that they sense only ultraviolet light. These photodiodes convert ultraviolet light into an electrical current. The digital camera developed at NC State employs a 32 x 32 array of the photodiode sensors -- or 1,024 sensors in all. As light from a UV source is focused onto the sensor array, currents are generated in the various photodiodes in proportion to the intensity of the light falling on each sensor.
The electrical current that each photodiode generates is collected and stored in a computer using special silicon readout circuitry. This information is then used to create a digital image of the UV light source that can be displayed on any computer monitor.
When fully developed using large-format photodiode arrays, this new type of ultraviolet digital camera could be used for numerous tasks, including biological agent detection, missile and shellfire detection, welding imagery, flame sensing and atmospheric ozone-level detection. "As there is less and less ozone in the atmosphere, more ultraviolet light comes through. Our camera can monitor this," Schetzina says.
In addition, large-format ultraviolet cameras based on aluminum gallium nitride photodiodes are expected to play a vital role in obtaining ultraviolet images of the stars and other astronomical objects -- images that may help scientists better understand the creation and evolution of the universe.
The new digital camera doesn't use film -- its sensing element is the array of photodiodes -- and it "looks somewhat different from typical cameras," Schetzina adds. "You probably wouldn't recognize it as a camera unless you were told." He estimates it will take several years before there are enough of the new cameras to satisfy demand by scientists and government agencies.
Students and faculty members in NC State's Solid State Physics Laboratory have worked for two years to develop the camera. Their research is funded by the Army Research Office and the Defense Advanced Research Projects Agency.
The decision was made to publish his team's findings on the Materials Research Society Internet Journal of Nitride Semiconductor Research rather than through a traditional print journal "to report this significant advance in camera technology very rapidly," Schetzina says.
"The site we are publishing on is peer-reviewed, just like the best print journals," he says. "But unlike print journals, our paper has been reviewed and is being made available to the whole world within one week after we submitted it for publication. We can get it into the hands of more people, much more quickly, than would be possible in the print format, where it may take six toeight months for a paper to see the light of day. In the future, all significant advances in science and technology will be reported in this way."
-- lucas --
NOTE TO EDITORS: The full text of Schetzina's team's paper, along with color images of their camera's first images, are accessible on the Internet at http://nsr.mij.mrs.org/4/.
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