Self-Referencing Method for Removing Surface Tilting and Warping in THz Time-Domain Reflection Imaging
In this work, we demonstrate a self-referencing method for removing the optical distortion from terahertz time-domain reflection imaging. To the authors’ knowledge, this is the first time a robust and flexible method is proposed to solve spatial phase variation problem without relying on any numerical parameter optimization nor extra-instrumental components. Here, we show the errors induced by the object physical distortion in the evaluation of the electric field phase and amplitude can be removed by correcting the spatial misalignment of the temporal terahertz signal. This consequently adjusts the severe corruption of the electric field in the far-infrared frequencies. We explain and demonstrate how to address the spatial misalignment of an object, employing the method on a tilted rigid surface and a warped surface. On these examples, we obtained highly successful results, being capable to remove imaging artifacts in the frequency-domain. We retain the method advantageous for preliminary data treatment of any not-perfectly flat surface, whenever the scope of the analysis consists in the estimation of phase and amplitude of THz signal in imaging modality.