一种改进的太赫兹主动成像系统

An improved active terahertz imaging system

利用卡塞格伦反射镜组自行搭建了一套反射式太赫兹主动成像系统,以商用肖特基二极管探测太赫兹信号,进行室温下的太赫兹快速成像.系统采用二维旋转式扫描,相较于光栅扫描,其扫描速度得到了大幅提高.通过大量实验发现该太赫兹成像系统,仅对铜柱成像效果较好,对其他物体成像效果不佳,甚至无法成像.通过对其可能存在的问题进行分析,利用数学建模的方法重新构建系统扫描轨迹,解决了成像物体形变的问题.此外,采用狄洛尼三角剖分算法对采集的数据点进行插值运算,进一步改善了系统的成像质量.实验结果表明,改进后的太赫兹主动成像系统不仅成像结果形变小,而且对一些复杂结构的物体,仍能获得较好的成像效果,对于促进该系统应用于安检等领域有着重要的意义.

The reflection‐mode terahertz active imaging system with a Cassegrain reflector has been constructed .A commercial Schottky diode is utilized in the system to detect the reflected terahertz signal and realize rapid imaging at room temperature .The system adopts 2‐D rotating scanning .Compared with the raster scanning ,the scheme can substantially increase the scanning speed of the system .It is found from the experiment that the system can get clear images only when the objects are copper sticks .However ,for the other objects ,the system is not effective enough so that sometimes the clear images cannot be obtained .In this paper ,the possible reasons for its poor image quality is analyzed .Firstly ,the method of the mathematical modeling on the basis of the theory of optical reflection is employed to reconstruct a scanning trajectory .The method can solve the deformation of the terahertz images ,because the calculated trajectory is much more consistent with the actual one compared with reported method .Secondly ,in order to optimize the quality of the images without the sacrifice of scanning time ,the Delaunay triangle algorithm is proposed to demodulate data and thus improve image quality .Our experiments show that a higher image quality can be achieved from the improved imaging system .Specifically ,the terahertz images have little deformation for the copper sticks .Even for the objects with complex structures ,acceptable image quality can be obtained .Moreover ,it is＆amp;nbsp;meaningful to apply the improved terahertz active imaging system to practical fields ,including the security checking , nondestructive evaluation ,etc .