Development of imaging system using heterodyne interferometer with terahertz waves

太赫兹成像技术用于成像内部结构和绘制各种目标的功能状态，是有前途和理想的诊断工具，因为它们在几毫瓦的入射功率下是非侵入性的。太赫兹成像的优点是太赫兹波辐射是非电离的和安全的，观察到的图像具有亚毫米尺度的分辨率，许多材料对太赫兹波是相对透明的，包括纸，塑料和纸板。在这项研究中，我们提出了一种具有外差检测接收器的成像系统，用于高灵敏度成像。为了实际应用，我们开发了一种采用外差检测方法的太赫兹CT成像系统。此外，我们展示了一种基于吸收对比度的深度分辨率3D成像，使用断层合成技术，它类似于计算机断层扫描，只是投影数量要少得多。我们将适合于构造的检测配置的反投影方法应用于图像重建。利用该系统，我们对纸幻影进行成像，并复制用铅笔书写的字符。

THz imaging techniques to image the internal structure and map the functional state of various targets are promising and desirable diagnostic tools because of their non-invasiveness under adequate incident power of a few mW. The advantages of THz imaging are that THz-wave radiation is non-ionizing and safe, the observed image has submillimeter-scale resolution, and many materials are relatively transparent to THz waves, including paper, plastics, and cardboard. In this research, we propose an imaging system with a heterodyne detection receiver for high sensitivity imaging. For a practical use, we developed a THz CT imaging system using heterodyne detection method. Furthermore, We demonstrated a depth-resolved 3D imaging based on absorption contrast using the tomosynthesis technique, which is similar to computed tomography except that the number of projections is much smaller. We applied the back-projection method suitable for the constructed detection configuration to an image reconstruction. Using the system, we imaged a paper phantom, and reproduced characters written by pencil.