  Ptychography, a form of Coherent Diffractive Imaging, is used with short
wavelengths (e.g. X-rays, electron beams) to achieve high-resolution image
reconstructions. One of the limiting factors for the reconstruction quality is
the accurate knowledge of the illumination probe positions. Recently, many
advances have been made to relax the requirement for the probe positions
accuracy. Here, we analyze and demonstrate a straightforward approach that can
be used to correct the probe positions with sub-pixel accuracy. Simulations and
experimental results with visible light are presented in this work.
