样品内部非平行界面的反射式terahertz波层析研究

Investigation on reflection tomography imaging with terahertz wave of nonparallel interfaces inside the sample

已有的反射式terahertz(THz)波层析研究都是针对平行界面进行,开展了样品内非平行界面的反射式THz波层析成像的数值模拟研究.根据物理模型给出了重构算法,并编制了相应的重构软件,数值计算结果表明非平行界面的重构是可行的.分析表明,重构误差主要来源于计算中的近似处理和累积误差.讨论了曲线轮廓界面的近似处理方法,提出当曲线轮廓各点的曲率半径都比较大时,可以把曲线分割成多段直线处理.最后分析了影响纵向分辨率的因素.结果表明,输入脉冲的脉宽越大则纵向分辨率越低,一般情况下纵向分辨率可达到亚毫米量级.

In previous studies on reflection tomography imaging with terahertz wave, only parallel interfaces were considered. In this article we report the numerical simulation on reflection tomography imaging with terahertz wave of nonparallel interfaces inside the sample. The reconstructing algorithm is given according to the physical model and the correlative reconstructing software is compiled. The results show that the reconstructing method of nonparallel interface is feasible. The analysis indicates that the reconstructing errors result from approximate treatment and accumulative error. The approximate treatment method of the curve contour is discussed. If the curvature radii at all points are large, the curve can be treated by cutting it into several line segmeants. The factors affecting longitudinal resolution are analyzed finally. The results show that the longitudinal resolution becomes worse as the pulse width of input pulse becomes larger. The longitudinal resolution can reach sub-millimeter size usually.