Eureka: National Institute of Standards and Technology (NIST) have built a prototype passive THz imaging system for detecting hidden weapons and other threats at distances up to 28m away. The technology is similar to the NIST camera in the SCUBA-2 telescope in Hawaii. Both instruments detect emissions at a wavelength of 850um, 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. This allows the sensor array to be cooled by a more compact, custom refrigerator.
The NIST imager's video frame rate is currently 6fps, but NIST researchers say their system can be developed further to have four times as many sensors (for a total of 1,004), which would produce larger, near-full-body images at faster video frame rates. A short lab video demonstrating the imager will be available at NIST web site, when it opens again. Here is the older NIST presentation.
Meanwhile, the passive THz imaging seems to attract more and more attention. Other recent works include ones at Johnson C. Smith University at Charlotte, NC, and European THz imaging project commercialized by Spain-based Alfa Imaging: