“Optical coherence tomography is an imaging method that uses infrared light,” explains Conner Phillips, a research scientist in the Characterization Technologies Group at Fraunhofer IKTS. “This method was originally developed for ophthalmology, but it can non-destructively generate three-dimensional images of the subsurface structure of a wide variety of materials and detect the presence of irregularities or defects.” The system works by sending near-infrared light into the material and detecting the reflected signals. This data produces high-resolution three-dimensional images of the internal structure. Material defects, air pockets or inadequately sealed areas are rendered visible without damaging the packaging or the product.
Continuously detecting the defects as small as eight micrometers
In the publicly funded OCTInline project, the IKTS researchers integrated the OCT technology directly in the sealing process in the packaging machine of an industrial partner. The system continuously and non-destructively tests the quality of the packaging seal in real time as the process is running at production rates of up to 25 meters per minute. “We can detect and visualize various pores in the seal down to a size of eight micrometers,” says Ralf Schallert, Characterization Technologies Group Manager at Fraunhofer IKTS.
The actual challenge lies in combining this high resolution with a high production rate. The smaller the defects are, the more data has to be collected and analyzed. Integrating the system into the industrial process also posed challenges for the project team. Even the slightest vibration of the film can affect the measurement. “We had to achieve a balance between depth of field, exposure time and film movement,” says Phillips.
New requirements for sustainable packaging make reliable seal integrity testing even more important. More manufacturers are turning to recyclable mono-material films. These are easier to recycle than multilayer composite materials. “Mono-material films are very attractive from an environmental perspective, but they are unfortunately more prone to seal defects,” says Schallert. “This increases the need for continuous monitoring.”
Lower scrap rates, higher process reliability
Real-time testing has multiple benefits for manufacturers. Faster defect detection reduces scrap and material consumption. In addition to detecting actual defects, the system also provides information on the condition of the machinery and tooling.
“Many defects arise because the pressure and temperature are not optimized for the material or because the tools are wearing down over time,” explains Schallert. “The OCT data enables us to visualize changes like this and to detect them at an early stage, such as when a tool change is necessary.”
A demonstration system has been in use at the project partner Kallfass Verpackungsmaschinen GmbH in Nürtingen since July 2026, where it is also presented to potential customers.
Flexibility for different applications
“The packaging industry is only one of many potential areas where this technology can be used,” adds Schallert. The systems can be individually adapted to different materials and requirements. The technology can thus be used for a wide range of industrial applications.
It is suitable for transparent and semitransparent materials and for many tasks in industrial quality assurance. For example, in addition to packaging, functional coatings, ceramic components or parts produced by additive manufacturing can be tested. “OCT can play an important role wherever thin layers, internal structures or the smallest defects have to be reliably detected. Potential applications range from medical technology to functional surfaces to industrial 3D printing,” says Schallert.
Fraunhofer-Gesellschaft
