Holographic measurement technology at production speed
Fault tolerance in automobile production is increasingly diminishing. Until recently, this presented suppliers with a problem: There were no sufficient methods for detecting micro defects during production. Visual inspection was the solution of choice, but this is not suitable for in-line measurements in the production process. By developing digital holography to become suitable for production, researchers at the Fraunhofer Institute for Physical Measurement Techniques IPM in Freiburg, Germany have resolved this dilemma. Digital holography makes it possible to fully inspect all parts – in a matter of seconds.
Three researchers from the Fraunhofer IPM – Dr. Markus Fratz, Dr. Alexander Bertz and Dr. Tobias Beckmann – have now brought the process of digital holography out of the laboratory and into the production hall. "We have been able to eliminate all the disadvantages and have therefore, for the first time, developed a system that allows one hundred percent inspection in production," says Beckmann, who heads the project together with Fratz. "Our system can measure centimeter-sized rough objects in fractions of a second with micrometer accuracy, thereby compensating for disturbances, such as vibrations." This allows for in-line measurements during the production process for the first time. Instead of taking samples, as before, each individual part can therefore be checked for dimensional accuracy and, at the same time, for the smallest defects. The challenge the three researchers faced was anything but easy to solve. "The search for defects is like trying to measure the shape of a 25-meter-high football stadium from a height of 300 meters so accurately that you can find the footprint of a baby in the grass – and in fractions of a second, even if the stadium is shaken by a light earthquake," Fratz explains.