Ptychography is a diffractive imaging method, where the function of a lens is replaced by a computer algorithm. Diffraction patterns are recorded from sparse scan coordinates onto an array detector, which is positioned equivalently to the imaging lens in a conventional microscope, where the intensity of the diffraction structure is recorded. It is the successful phasing of these intensities that allows for the propagation of the wave field and thus the formation of a fully complex, aberration-free image. As the detector is now an intrinsic part of the image forming process, the quality of the final image is far more sensitive to imperfections within the detection stage – an issue that has previously hindered the progress of ptychography in the electron regime.
We present a new reconstruction algorithm which is able to correct for the first order response profile of the detector during the image forming process. In so doing we are able to enhance an electron ptychograph [1], resolving 1.4Å atomic spacings in gold nanoparticles while retaining the structure of the thin amorphous carbon support film. Achieving such resolutions in a low cost SEM (with a nominal resolution of 1.2nm) has potentially large implications for the role of the SEM within electron microscopy.