Detective Work Using Terahertz Radiation (IMAGE) Fraunhofer-Gesellschaft Caption The terahertz scanner not only finds hidden wall pictures, but can also prove the presence of biocides on pieces of art. Credit © HfbK Usage Restrictions The picture may be used for editorial purposes only. It is protected by copyright. The use is free of charge if the reference is mentioned. License Licensed content Disclaimer: AAAS and EurekAlert! are not responsible for the accuracy of news releases posted to EurekAlert! by contributing institutions or for the use of any information through the EurekAlert system.