By virtue of its versatile recording geometries, ptychography is a promising full-field lensless phase imaging approach in the prosperous research area of terahertz imaging. In this paper, we propose an extrapolation extended ptychographical iterative engine, named as the EE-PIE reconstruction algorithm, to increase the lateral resolution of terahertz ptychography. A divergent spherical beam is applied to illuminate the object, while diffraction patterns are recorded in the Fresnel region. The signal-to-noise ratio of the diffraction patterns is enhanced under divergent probe illumination, while the size of the diffraction patterns is numerically enlarged by the proposed algorithm. Both the reconstruction quality and the resolution are enhanced without adding to the complexity of the setup or increasing the data acquisition time. The proposed method is experimentally demonstrated using a cluster of phylloclades, a patterned polypropylene plate and a Siemens star target. Compared with the planar illumination, the resolution of the divergent spherical illumination is improved by 2.14 times. On this basis, the extrapolation algorithm further improves the experimental resolution by 1.26 times.

凭借其多功能的记录几何形状，ptychography 在太赫兹成像的繁荣研究领域是一种很有前途的全场无透镜相位成像方法。在本文中，我们提出了一种外推扩展 ptychographical 迭代引擎，称为 EE-PIE 重建算法，以增加太赫兹 ptychography 的横向分辨率。使用发散的球面光束照亮物体，而衍射图案则记录在菲涅耳区域。衍射图案的信噪比在发散探针照射下得到增强，而衍射图案的尺寸通过所提出的算法在数值上放大。重建质量和分辨率都得到提高，而不会增加设置的复杂性或增加数据采集时间。所提出的方法使用叶状枝条簇、带图案的聚丙烯板和西门子星目标进行了实验证明。与平面照明相比，发散球面照明的分辨率提高了2.14倍。在此基础上，外推算法进一步将实验分辨率提高了1.26倍。