Preserving cultural heritage – through research and high-tech

CultLab3D: 3D digitalization on the conveyor belt

CultLab3D – the scanner allows objects of varying size to be digitalized fully automatically, capturing their geometry, texture and physical/optical material properties so as to enable faithful reproduction to the nearest micrometer.
© Fraunhofer IGD

CultLab3D – the scanner allows objects of varying size to be digitalized fully automatically, capturing their geometry, texture and physical/optical material properties so as to enable faithful reproduction to the nearest micrometer.

Researchers capture the frieze of the Pergamon Altar using a laser scanner.
© Fraunhofer IGD

Researchers capture the frieze of the Pergamon Altar using a laser scanner.

Many cultural artifacts fall victim to looting, war and natural disasters. So how can research make a difference? After all, preventing wars and natural disasters would not be an easy task. But there is a way of saving cultural heritage for posterity: 3D digitalization of the artifacts. This allows them to be used at any time – and simultaneously, too: while teams of researchers investigate a digitalized temple online, museum visitors all over the world can take a virtual stroll through the ancient structure at the same time.

Up until now, 3D digitalization was a very time-consuming process. “For the first time, our automated scanner CultLab-3D now makes it possible to send out entire museum collections into the digital world,” explains Pedro Santos, Head of Department at the Fraunhofer Institute for Computer Graphics Research IGD in Darmstadt. Simply scan in the QR code of the object concerned, place it on a tray – and the rest takes care of itself. The result is a three-dimensional digital copy – and the speed is incredible: A new object can be digitalized every five minutes. The principle: multiple cameras – nine in the case of the scanner – are used to photograph the item from several sides. A software then puts the images together to assemble a three-dimensional reconstruction. The method even works with large statues, though in this case the scanning is done by hand rather than automatically. This was how Fraunhofer IGD researchers digitalized the Pergamon Altar, for example – using a lightweight laser scanner. The scientists are now even going one step further: “In future, we won't just be mapping geometry, texture and optical material properties – i.e. the exterior of the object – but also its interior,” says Constanze Fuhrmann, a researcher at Fraunhofer IGD. “For the first time, the data relating to both the inside and outside of the object are combined in standardized fashion to create a 3D model and visualized three-dimensionally in front of the screen.”

 

3D digitalization meets ultrasound

Among other things, experts have extended the CultLab3D approach with the addition of ultrasound analysis. “This means restorers can zoom into the inside of the object in the digital representation and immediately detect any instabilities, corrosion or holes,” says Peter-Karl Weber, Group Leader at the Fraunhofer Institute for Biomedical Engineering IBMT. A highlight here is that this type of analysis previously had to be carried out by hand, which could easily take several hours: now the process is complete within a few seconds.

This is possible thanks to an elastic strap that is attached to the object. “The strap has ultrasound transducers attached to it. A special electronics system allows the transducers to switch between transmitter and receiver. Instead of having to constantly reposition the transducers, the strap is simply placed around the artifact,” says Weber. QR codes on the transducers allow a camera to detect where the ultrasound tomogram has been recorded, and a software inserts the ultrasound images into the digital scan.

When doctors carry out ultrasound examinations, they apply a gel to the patient’s skin so as to conduct the ultrasound into the body. This is not a good idea with art objects because the gel would cause damage. Researchers at the Fraunhofer Institute for Applied Polymer Research IAP are therefore developing a material that allows the ultrasound to be transmitted in a dry state. This material has the same properties as gel – its consistency is similar to that of dough – and it can be removed free of residue. “We’ve already successfully measured the hair on the Dresdner Knabe statue using this method,” says Weber. The IAP team were able to achieve the required properties using a matrix material to which small particles are added.

The Freiburg Minster: a finial as a 3D print-out

Photogrammetry, the technique on which CultLab3D is based, can also simplify the restoration of churches. If a piece has to be reproduced at the top of a church tower – such as a finial – the restorers previously had to dismantle the existing finial and use it as a template in the workshop to chisel out an identical one in stone. The Fraunhofer Institute for Physical Measurement Techniques IPM joined forces with the traditional stonemason’s Münsterbauhütte Freiburg and opted for a different method: using a portable scanner and an endoscope camera, they are able to digitally capture the finials and everything else – complete with cavities and undercuts – and print them out on a 3D printer. Restorers then use this 3D print-out as template for chiseling out a replacement – without even having to touch the original. This protects the object itself as well as significantly reducing the time and cost involved.