Handheld Terahertz Sensor for Mobile Use

The special properties of terahertz waves include the ability to penetrate electrical insulators such as ceramics, glass, and plastics. This ability has an advantage over the established methods based on x-rays, ultrasound, or thermography, which all have limitations, especially, when assessing modern fiber reinforced plastics. A solution is now available in the form of the mobile, terahertz handheld scanner, which can also examine structures in hard to access places and detect defects in plastics.

 

Overcoming the Limits of Ultrasound Systems

Many applications demand measuring methods that are suitable for rapid and mobile use. Often, ultrasound is chosen for this reason. Water and gel are common coupling media to minimize the high losses when passing from air to a material. However, this is not possible for ceramics and foams. Fortunately, terahertz-measuring systems are non-contact, require no coupling medium and can even be used to examine hollow structures.

Hand-held terahertz sensor
© Fraunhofer ITWM
Hand-held terahertz sensor. Ready for use without additional devices, standard socket sufficient.
Hand-held terahertz sensor
© Fraunhofer ITWM
Hand-held terahertz sensor. Ready for use without additional devices, standard socket sufficient.

Innovative Handheld Scanners

The handheld scanner is a complete terahertz system for non-destructive on-site testing. Thanks to its compact, lightweight design, it is easily transported and ideal for use with non-movable samples as well as in various location within the production. Single-sided sample access is sufficient as the system operates in reflection. The housing of the sensor protects  from dust and spray water, which facilitates use in a manufacturing environment. An integrated touch screen ensures ease of operation and a clear display of all measurements.

When the handheld scanner is moved over a sample, it continuously records A-scans (thickness profiles) while the position sensor simultaneously registers the location. By linking these two data readings, the associated B-scans are created (spatially resolved cross sectional images). The position sensor corrects for uneven movements of the scanner.

 

Pipe Inspection During Production

The handheld scanner is already in use in some production settings, for example, to inspect pipes directly after extrusion and to ensure a real-time process control. In this case, ultrasound cannot be used because of the high pipe temperatures and the plastic core present inside the pipe. Another example is the post-welding inspection of pipe insulation.

Video: Mobile Terahertz Inspection Systems at Fraunhofer ITWM

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