The use of high-frequency technology makes it possible to illuminate a large number of materials that are not transparent in the optical range. At the same time, even the smallest differences in the material that remain hidden in the X-ray range become visible. The experimental system SAMMI demonstrates these properties of the imaging radar and enables the non-contact detection of material differences in non-metallic solids.
The name SAMMI stands for Stand Alone MilliMeter wave Imager and, as the name implies, its primary task is to illuminate and image samples that appear transparent in the millimeter wave range (here 90 GHz). There, the dielectric material properties determine the transmission behavior of the electromagnetic waves through a massive body and zones of absorption or polarizability of varying degrees are differentiated in the fluoroscopy image.
As a result, different materials or material compositions in a body also show a distinguishable contrast and even the smallest foreign bodies and inhomogeneities can still be detected in a medium that is intransparent to humans.
Based on the use of these physical effects, the primary task developed to generate a method for measuring quality deviations on fast-running production lines. At the same time, the resulting system represents a successful know-how transfer of quality control by spatially resolved spectroscopy from the laboratory into an application-related environment.
SAMMI is obviously not a design that can easily be mounted on a production system. Rather, it currently represents a prototype for an innovative marketable measuring method and, as a stand-alone variant, can detect knives or explosives in letters and small packages just as independently as, for example, unwanted foreign bodies in chocolate. SAMMI makes a contribution in this way:
- for the protection of endangered persons and critical infrastructure
- for random industrial quality assurance
- in the laboratory for material analysis
The intention behind the minimalist design of SAMMI was to reduce the usually quite cost-intensive electronics and mechanics to a minimum. The goal is a system that is superior to conventional X-ray fluoroscopy due to an attractive price/performance ratio and the use of non-ionizing radiation.
The development of SAMMI proves that a production-integrated measuring and inspection system based on the use of millimeter waves is feasible. As a prototype, it covers a broad and commercially interesting range of tasks.
SAMMI Evolution
In the following evolutionary stage, SAMMI will be able to automatically recognize the dielectric properties of substances and use these to draw conclusions about the chemical composition of the measuring samples. This function also allows the classification of impurities e.g. in food and the detection and identification of hazardous substances and substance mixtures. On the basis of a cluster algorithm, the dielectric properties of the samples are examined for (un)similarities so that foreign bodies can be clearly detected and displayed.
Fraunhofer Institute for High Frequency Physics and Radar Techniques FHR
