Ptychography and Related Diffractive Imaging Methods

Publisher Summary Ptychography is a nonholographic solution of the phase problem. It is a method for calculating the phase relationships among different parts of a scattered wave disturbance in a situation where only the magnitude (intensity or flux) of the wave can be physically measured. Its usefulness lies in its ability (like holography) to obtain images without the use of lenses, and hence to lead to resolution improvements and access to properties of the scattering medium that cannot be easily obtained from conventional imaging methods. The chapter discusses ptychography in the context of other phase-retrieval methods in both historical and conceptual terms. In an original and oblique approach to the phase problem, it was Hoppe who proposed the first version of the particular solution to the phase problem. The word “ptychography” was introduced to suggest a solution to the phase problem using the convolution theorem, or rather the “folding” of diffraction orders into one another via the convolution of the Fourier transform of a localized aperture or illumination function in the object plane. Apart from computers, the two most important experimental issues that affect ptychography, relate to the degree of coherence in the illuminating beam and the detector efficiency and dynamic range.