Analysis of influence of object–detector distance error on the reconstructed object and probe in ptychographic imaging

Ptychography is a lensless imaging technique that is capable of reconstructing an object and illumination simultaneously by scanning the object at several positions with respect to a localized illumination beam. It has emerged as a powerful tool with applications ranging from high resolution imaging to optical metrology. A precise image reconstruction in ptychography is of utmost importance in several applications. An error in the measurement of the object–detector distance was found to affect the reliability of the reconstructed probe and the object. Several axial distance correction algorithms have been proposed to address the issue. However, the additional axial distance correction increases the complexity of the reconstruction algorithm. In this study, a detailed theoretical analysis of the relationship between the reconstructed images and the object–detector distance error is presented. It shows that high resolution object and probe images can still be reconstructed without an axial distance correction algorithm. The theoretical analysis is quantitatively studied by numerical simulations and experimental results.