Active Terahertz imaging with high acquisition rates and its application for moisture sensing

In the emerging field of THz imaging, various possible applications have been demonstrated. For many of them, practical usage is restricted by slow acquisition speeds. We present fast fully electronic scanning THz imaging systems operating at room temperature at frequencies up to 0.812 THz and with targeted frame rates of 10 Hz. The measurements of moisture content in paper using THz radiation is one application we want to discuss in more detail. The precise knowledge of water content in the sheet is important for the paper manufacturer because of the moisture's influence on paper quality and production costs. Several features of THz radiation are helpful in this context: High transmittance of paper, combined with the strong absorption by water provide a brilliant contrast, while the long wavelength prevents scattering, some prevailing moisture sensing methods are suffering from.