Ptychography: early history and 3D scattering effects

The coherent diffractive imaging method of ptychography is first reviewed from a general historical perspective. Much more recent progress in extending the method to the 3D scattering geometry and the super-resolution configuration is also described. Ptychography was originally conceived by Walter Hoppe as a solution to the X-ray or electron crystallography phase problem. Although the existence of this type of phase information was clearly evident in the early 1970s, the technique was not implemented at atomic-scale wavelengths until the 1990s, and then only in a way that was computationally inefficient, especially in view of the limited size of computers at that time. Fast and efficient ptychographic algorithms were developed much later, in the mid-2000s. The extremes of crystallography ptychography, which only requires two diffraction patterns, and the Wigner Distribution Deconvolution (WDDC) method, which needs a diffraction pattern for every pixel of the final reconstruction, are described. Very recent work relating to the application of serial iterative to 3D inversion are also described.