X-rays and e-beams are used for high-resolution imaging where the requirement for highly accurate lenses is one of the limiting factors. Hence, lensless imaging is preferred. Coherent Diffractive Imaging (CDI) is a lensless imaging technique which uses intensity patterns in the far-field to obtain the complex amplitude of the object. Ptychography, an emerging area of research, belongs to the class of CDI techniques. In ptychography, the object is partially illuminated by a scanning probe and the intensity patterns in the far-field for each probe position are recorded and used to reconstruct the object. One of the important aspects to the success of this method is the overlap between the adjacent probes and the accurate knowledge of the probe positions. Recently, we proposed a new method to correct the probe positions which uses the gradient of intensity patterns in the far-field. Here, we propose another method to correct probe positions.
For high resolution imaging, X-rays and electron beams are being used. However, for such a short wavelength, imaging with lenses becomes difficult as lenses absorb a part of radiation and lenses with very low aberrations must be used. Ptychography is a lens-less imaging technique which uses intensity information of the multiple diffraction patterns in the far field. These multiple far field diffraction patterns are generated by an unknown object which is scanned by a localized illuminated spot (probe).
Accurate knowledge of initial parameters is important for a good reconstruction of the object. Robustness of the Ptychography Iterative Engine (PIE) has already been studied for inaccurately known initial parameters, where the success of the algorithm was found to be sensitive to the accuracy of the estimate of lateral positions of the probe.
We present here a new method to correct the lateral position of the probe with respect to the object. This method is more straightforward to implement than other existing algorithms while comparable accuracy for the lateral position is achieved. Being able to correct the probe positions has positive implication in experiments, in particular at the short wavelength cases. It relaxes the requirement for the experimental set-up.