Potential of THz-time domain spectroscopy in object inspection for restoration

Teraherz-Time Domain Spectroscopy enables a parallel determination of tomographic and spectroscopic information. The electromagnetic pulses used for this method have pulse durations of approximately one picosecond. Thus, runtime measurements can be used to investigate the layered structure of materials with accuracy higher than geo-radar methods. While passing the material, the pulse shape changes because of dispersion. Rotational and vibrational resonances of polar molecular groups appearing as peaks in the Fourier spectrum serve as a useful means of identification of substances, as it was demonstrated with Lindane and Pentachlorophenol. THz-images can be made by scanning the object step by step as well. The method is tested on an oil painting. E(t) - and E(omega) - movies were calculated from the data at each point of the measuring grid. This method allows hidden paintings to be revealed.