NIST unveils prototype video imaging system for remote detection of hidden threats

 

 

                       Researcher Dan Becker demonstrates NIST's prototype imaging system for remote
                                    detection of hidden weapons. The inset on the left is the image created by the instrument,
                                    which detects naturally emitted or reflected light at sub-millimeter wavelengths.
                                    The ceramic knife is cooler and reflects cooler light from the room, and therefore appears
                                    darker than the surrounding image. Credit: Becker/NIST

 
http://phys.org/news/2013-10-nist-unveils-prototype-video-imaging.html#jCp
By adapting superconducting technology used in advanced telescope cameras, researchers at the National Institute of Standards and Technology (NIST) have built a prototype video imaging system for detecting hidden weapons and other threats at distances up to 28 meters away.

 With further development, the new NIST imager might eventually be used for applications such as detecting suicide bomb vests under clothing at military checkpoints or identifying threats at sea such as ships hidden in fog.

NIST's prototype imager, unveiled at a conference last week, has three key features, which may offer advantages over other screening systems such as those used for airport security.

First, the NIST imager has NIST-developed software to weave together high-resolution still images to make video in near real time. Second, the system operates from a longer "standoff" distance, 16 to 28 meters away from a target, than other similar imaging systems. These combined features make the NIST instrument unique.

Third, unlike screening systems that bombard a target with X-rays or other types of radiation, the NIST imager is passive, which means it merely detects naturally emitted or reflected light. Similar to an infrared camera, the NIST instrument scans a target to detect emissions of terahertz (also called sub-millimeter) light and then generates images based on variations in temperature and reflected light among different target materials, such as biological tissues versus metals or ceramics.

The long-distance operation is made possible by very sensitive detectors—NIST's transition-edge sensors. These tiny but sensitive thermometers are made of a superconducting metal, which changes resistance in response to very faint light. The system currently has 251 sensors, and the resulting images show detail as small as 1 centimeter in size across a target area about 80 by 60 centimeters. The system produces less detailed images at the farther end of its operating range.

The technology is similar to the NIST camera in the SCUBA-2 telescope in Hawaii. Both instruments detect emissions at a wavelength of 850 micrometers, a wavelength of light that passes through both clothing and the atmosphere. Both sets of sensor arrays are packaged with superconducting amplifiers to boost signal strength, using a NIST technique that makes large arrays practical. But the new imager's sensors are made of a different metal, aluminum, which superconducts at higher temperatures of 1.2 Kelvin (minus 272 degrees C). This allows the sensor array to be cooled by a more compact, custom refrigerator

 

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