Scanner (security technology)

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X-ray image of a truck
Mobile cargo scanner from the New Zealand Customs Service

In security technology, devices that search for hidden objects in a non-contact and non-destructive manner are called scanners .

X-ray technology

X-ray image of luggage

X-rays penetrate materials. The denser the material, the more it is absorbed. If the object to be examined is placed between the radiation source and the detector, a radiograph is obtained. The picture above shows a picture of a cargo scanner that can scan through entire trucks. The radiation exposure is significantly higher than with medical X-rays .

For airport security are baggage scanners used. The picture on the right shows an X-ray image of a piece of luggage. For better interpretation, an image processing system tries to color coherent objects uniformly. The result can be seen on the left monitor. The X-ray radiation is significantly lower than that of a cargo scanner and should be lower than with conventional X-ray examinations.

Compton scattering throws a small part of the radiation back to the radiation source. Devices that expose people to weak but high-energy X-rays have been in use in the USA since 2005. Clothing is irradiated largely unhindered, while the body is more or less naked on the backscatter image due to reflection.

Terahertz technology

People stand out from their surroundings due to their increased heat radiation . Short and medium wavelengths are completely absorbed by clothing. Detectors for the longer-wave range of terahertz radiation that penetrate clothing have recently been available . The passive terahertz technology does not require a radiation source, but registers the existing radiation with wavelengths of up to 1 mm. Compared to the X-ray backscatter method, a THz camera generates images without anatomical details. Objects on the human body cause a visible shadow on the thermal radiation image. In the active terahertz technique, the body is scanned with a fine microwave beam. Different materials can be detected by varying the wavelength.

Web links

Individual evidence

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