Ptychographic Ambiguity and Reconstruction
share
Blind ptychography is the scanning version of coherent diffractive imaging which seeks to recover both the object and the probe are simultaneously. Concrete examples of ambiguity in blind ptychography are presented to illustrate the challenge of blind ptychography. Two opposing classes of measurement schemes are discussed: the mixing schemes and the raster scans. The former generally admit only a complex scaling factor and a linear phase ambiguity as ambiguities while the latter a host of other ambiguities of many degrees of freedom. AMDRS is a reconstruction algorithm based on alternating minimization by Douglas-Rachford splitting. Enabled by an initialization method informed by the probe phase constraint in the theory of uniqueness, AMDRS converges globally and geometrically. The technique of bright-field boundary condition is introduced to remove the linear phase ambiguity and accelerate convergence, and the technique of adding salt noise is used to improve the quality of reconstruction of objects exhibiting extensive area of dark pixels.
READ FULL TEXT