连续太赫兹波双物距叠层定量相衬成像  

Continuous-wave terahertz quantitative dual-plane ptychography

作　　者：王大勇[1,2] 李兵 戎路 赵洁[1,2] 王云新 翟长超[1] Wang Da-Yong;Li Bing;Rong Lu;Zhao Jie;Wang Yun-Xin;Zhai Chang-Chao(College of Applied Sciences,Beijing University of Technology,Beijing 100124,China;Beijing Engineering Research Center of Precision Measurement Technology and Instruments,Beijing University of Technology,Beijing 100124,China)

机构地区：[1]北京工业大学应用数理学院,北京100124 [2]北京市精密测控技术与仪器工程技术研究中心,北京100124

出　　处：《物理学报》2020年第2期292-301,共10页Acta Physica Sinica

基　　金：国家自然科学基金(批准号:61675010);北京市科技新星(批准号:XX2018072)资助的课题~~

摘　　要：针对连续太赫兹波叠层成像重建算法收敛较为迟滞的问题,提出一种连续太赫兹波双物距叠层成像方法及相关重建算法,使用不同记录距离形成的差异化衍射图幅值作为重建算法记录平面的约束条件,增加了记录平面数据多样性和衍射信息冗余度.仿真结果表明,本方法可以加快算法收敛速率,有效减少迭代次数,提高连续太赫兹波定量相衬成像计算效率.随后构建了基于2.52 THz光泵连续太赫兹激光器的双物距叠层成像实验装置,应用双物距记录方法及改进算法重建获得了聚丙烯基字母图案样品的幅值和相位分布,结果表明改进方法可以减少算法迭代次数,提升计算效率,同时改善相位像重建结果保真度.Terahertz(THz) radiation lies between the millimeter and infrared region of the electromagnetic spectrum,which is typically defined as the frequency range of 0.1–10 THz and the corresponding wavelength ranges from 30 μm to 3 mm. Terahertz radiation due to wide spectrum, high penetration, low energy, and other important features, has been a valuable tool for imaging and non-destructive testing on a submillimeter scale. Continuouswave(CW) terahertz ptychography is a type of phase-contrast technique with advantages of simple set-up and large field-of-view. It retrieves the complex-valued transmission function of the specimen and the probe function at the same time. The extended ptychographic iterative engine(e PIE) algorithm is used as the reconstruction algorithm in the field of ptychography, because it is relatively simple, and can use computer memory efficiently.However, the problem of algorithm convergence delay makes us unable to acquire the reconstruction result very quickly. Since the ptychography is a problem of retrieving phase information, physical constraints affect the convergence speed of the algorithm strongly. In this paper, we propose a dual-plane e PIE(dp-e PIE) algorithm for CW THz ptychography. By moving detector along the axis and capturing diffraction patterns of one zone of an object at two recording planes, then, two sets of patterns used as the constraints simultaneously can increase the diversity of experimental parameter. Hence, the convergence rate can be improved. The simulation results suggest better reconstruction fidelity with a faster convergence rate by the dp-e PIE algorithm. The dual-plane terahertz ptychography experimental setup is built based on 2.52 THz optically pumped laser and Pyrocam-III pyroelectric array detector. Compared with other methods to increase the diversity of measurement, the setup of dual-plane ptychography can be compact and simple, thus reducing the terahertz wave transmission loss. A polypropylene sample is adopted and it is approximated as a pure phase

关 键 词：太赫兹成像 叠层成像 相位复原 双物距 

分 类 号：O441.4[理学—电磁学]