Extended ptychography in the transmission electron microscope: Possibilities and limitations

The extended-ptychographical iterative engine (e-PIE) is a recently developed powerful phase retrieval algorithm which can be used to measure the phase transfer function of a specimen and overcome conventional lens resolution limits. The major improvement over PIE is the ability to reconstruct simultaneously both the object and illumination functions, robustness to noise and speed of convergence. The technique has proven to be successful at optical and X-ray wavelengths and we describe here experimental results in transmission electron microscopy supported by corresponding simulations. These simulations show the possibilities – even with strong phase objects – and limitations of ptychography; in particular issues arising from poorly-defined probe positions. ► Ptychography is an alternative technique for solving phase problem in TEM. ► The extended-Ptychographical Iterative Engine (e-PIE) is an algorithm which allows solving both the probe and the illuminated object phase. ► A topological study demonstrates its capability in TEM. ► Simulations show the robustness to noise and capability to retrieve strong phase object but reveal also a high sensitivity to the probe position uncertainty.