Phase retrieval is a useful imaging modality, which has significantly contributed to an improved imaging quality in the fields of astronomy, x-ray imaging, and electron microscopy.     The advantage of phase retrieval imaging lies in its robustness against disturbing environmental conditions, the recovery of quantitative phase information, the application of partially coherent light sources, the possibility of a lensless setup implementation (resolution only restricted by size of sensor and distance to sample). In particular the latter of the advantage offers a great potential to revolutionise the imaging quality in x-ray and electron microscopy, where the manufacturing of high quality lenses is connected with great difficulty.     A key to phase retrieval imaging is the recording of speckle de-correlated diffraction patterns. Many a different phase retrieval techniques have been developed based on this principle e.g. Through focus series (axial speckle decorrelation), multiple wavelength (chromatic speckle decorrelation) and so on.     Ptychography and its relative Fourier-ptychography have become the state of the art phase retrieval technique.   Ptychography is based on the illumination that is laterally displaced over the object while a series of either Fraunhofer of Fresnel diffraction patterns are recorded. Each diffraction pattern is obtained from an area of the specimen which overlaps with another area of specimen previously illuminated, thus introducing a large degree of redundancy in the data: this is used to solve the phase problem (i.e. to calculate the phase of the diffraction patterns which can only be measured in intensity). This roundabout lensless method creates aberration-free very high contrast quantitative phase images (less than 0.02 radian sensitivity) at a resolution determined by the effective numerical aperture dictated by the angle subtended by the detector at the object plane.