Contactless Inspection of Handwritten Documents with Terahertz Imaging

This paper presents results of studies on the use of Terahertz (THz) imaging for contactless inspection of handwritten and possibly sealed documents as a preliminary study for the THz-based inspection of historical documents. We investigated the use of focused B-scans in transmission mode. As a basis, some general aspects associated with the investigated scenario are presented. These include investigations of paper and ink as well as the system's image resolution. For possible application in scanning historical letters, one and stacks of two papers with handwriting inside an envelope were investigated.