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Part of a series on Phase retrieval

Data preparation

Object initialization

Probe initialization

Lines 140 to 170 set the parameters the probe in the p object. The probe initialization script is found at +core/prepare_initial_probes.m.

Initial theoretical probe

A theoretical probe is generated if p.model_probe = true; (line 141). The probe is generated in +core/ptycho_model_probe.m using the parameters in p.model.*. As p.beam_source (line 39) is set to 'electron', the probe is generated by following Eq.(2.10) of (1).

Mode decomposition

The initiated probe by +core/ptycho_model_probe.m is a ‘flat’ array of shape (Ndpx, Ndpx). The PSO example sets 8 probe modes by p.probe_modes = Nprobe; (line 164). The original flat probe is assigned to the first mode, and the rest are generated with the parameters p.mode_start_pow = 0.02;, p.mode_start = 'herm';, and p.ortho_probes = true;.

Hermite generation

The extra probes are generated using Hermite polynomials.

PtychoShelves (and fold_slice) supports multiple probes. Thus the actual probe saved in p has a shape of (Ndpx, Ndpx, PROBE_NUMBER, PROBE_MODES). However, the PSO example only uses one probe.

References