| Terahertz time-domain spectroscopy is a very effective non-contact nondestructive testing method,compared with continuous wave imaging,a continuous signal in the time domain can be obtained,through the processing and analysis of the signal,information such as refractive index,extinction coefficient and thickness of the material through which the terahertz signal passes can be obtained,which is very important for the study of the internal structure and materials of frescoes in archaeology.The application of terahertz in archaeology is still in its infancy,and the application of terahertz in archaeology abroad is mainly focused on the application of layering of paint layers in oil paintings,and there are few relevant studies on frescoes,and there is basically none in China.The terahertz signal can pass through the surface white ash to obtain the structure and material information of the mural itself.The direct imaging can obtain good results when the interior is more uniform,but it is difficult to complete the distinction when the interior is complex,the paper proposes two methods from denoising and fitting to eliminate this effect,and has good results for some of the pigments;the multiple subinterfaces inside the object are too close to produce the overlap of reflected signals,and the overlapping signals cannot be judged by the naked eye when the distance is less than the width of the pulse,using the discrete deconvolution and In order to further improve the spatial resolution,a point diffusion model is set up for the Gaussian distribution of the terahertz signal,and the Gaussian blurred image is eliminated by deconvolution of the data opposite to the point diffusion model.further improve the spatial resolution,a walshHardamard encoded optical mask modulated solid-state source signal is set,and only the total amplitude is measured using a single-pixel detector,and the ultra-high resolution image can be obtained by calculation. |
PDF Full Text Request