Ten implementations of ptychography

Summary Ptychography is an increasingly popular phase retrieval imaging technique, able to routinely deliver quantitative phase images with extended field of view at diffraction limited resolution. Different variants of this technique, like Bragg ptychography and Fourier ptychography, have also been developed and applied to various fields. Here we experimentally demonstrate 10 ways to implement the conventional real space transmission ptychography, and compare their properties to provide a guide to choosing the optimal setup for a specific application. Lay description Ptychography is a lensless imaging technique, able to routinely deliver quantitative phase images at diffraction limited resolution from a set of diffraction intensity measurements. There are three fundamental components: a confined coherent illumination, an overlapping scan strategy and an iterative image reconstruction algorithm. The confined illumination is scanned over the specimen at a grid of positions, such that the illuminated areas from two adjacent scan positions partially overlap (i.e. the overlapping scan). The transmitted (or reflected) wavefield is then captured by a camera located at somewhere downstream, but with the phase information of the wavefield lost. The overlapping scan generates redundancy in the measurements and the reconstruction algorithm allows us to utilise the redundancy to recover the phase information. Because no lens in involved during the whole imaging process, ptychography is able to bypass the resolution limits imposed by the poor lenses available at short wavelengths. Although invented to circumvent the need for lenses, ptychography can also be implemented with their assistance. The confined illumination can be formed by passing an extended beam through a pinhole or condensing the extended beam via a lens. In either way, a diffuser can be inserted to increase the angular range of the illumination, giving rise to the four probe‐forming methods. For each probe, three imaging setups can be used to perform ptychography: lensless setup, microscope setup and selected area setup. Lensless setup means no lens is involved between the specimen and the camera. Microscope setup replaces the camera in the lensless setup with its demagnified version using a microscope imaging system (an objective lens and a tube lens). Selected area setup replaces the specimen in the lensless setup with its magnified image using the same imaging system. Combined with the four probe typ