Improvement Of Terahertz Active Imaging System

The development of THz technology has important academic value and broad application prospects with the characteristics of THz wave. With the continuous development of THz wave source and terahertz detector technology, THz imaging technology has gradually become the hotspot in the field of the THz field, many research groups and companies have put into the THz imaging system related researchThe 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 system is simulated by the ZEMAX and the possible reasons for its poor image quality is analyzed. After reconstructing the system, the method of reconstructing a new scanning trajectory is employed to solve the deformation of the terahertz images. Then 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 meaningful to apply the improved terahertz active imaging system to practical fields, including the security checking, nondestructive evaluation, etc.