Researchers at the Fraunhofer Institute forHigh Frequency Physics and Radar Techniques (FHR; Wachtberg, Germany) have developed a standalone millimeter-wave imager (SAMMI) that can see through non-transparent materials.
According to the researchers, the imager could be used forquality control purposes as well as to analyze materials in a laboratory. Dr. Helmut Essen, head of the FHR's millimeter-wave radar and high-frequency sensors department, said it could be used to detect wooden splinters lurking in diapers, air pockets in plastic, breaks in bars of marzipan, and foreign bodies in foodstuffs.
Inside the imager, a transmitting and a receiving antenna are mounted on each of two opposing rotating plates. When a conveyor belt transports a sample between the antennae, it is bombarded withelectromagnetic waves from the transmitters at a frequency of 78 GHz. Different areas of the sample then absorb the signal to different degrees. The resulting signals picked up by the transmitters can then be used to construct an image of the sample showing its composition on the scanner’s fold-out display.
At present, SAMMI is only suitable for spot checks. However, the FHR researchers are working on adapting the millimeter-wave sensor for industrial assembly lines where it could be used to automatically inspect products. They envision mounting a line of sensors over the conveyor belt, so that, in the future, products can be scanned at a speed of up to 6 m/s.
They also plant to upgrade the system to work atterahertz frequencies of 2 THz. "Then we'll be in a position not just to detect different structures but also to establish which type of plastic a product is made from. That's not possible at the moment," says Essen.
-- By Dave Wilson, Senior Editor,Vision Systems Design