Ptychographical algorithm of the parallel scheme

Phychography is an important technique in the quantitative phase imaging research domain, which employs the illuminating probes to scan the specimen in an overlapped requirement, and the reconstruction is conducted by using the ptychographic iterative engine. But the contradiction between the imaging efficiency and quality has become a bottleneck for its wide applications. In this paper, we start with the fundamental principle of the iterative algorithms for ptychographical imaging, and propose two parallel schemes based on CPU and GPU, besides the influences of the specimen size, the number of blocks and illuminating beams on the speedup of the two schemes are investigated via simulation experiment. The result shows that the complex amplitude of the specimen can be correctly reconstructed, meanwhile, the speed is significantly improved, which reduces the time consumed by one order of magnitude. This improvement solves the above contradiction, so that we can expect to achieve quasi-real-time imaging. The experimental data also indicate that 1) in optimal partition, parallel speedup is related to the size of the specimen, bigger size is corresponding to more obvious acceleration; 2) the same specimen under different partitions will speed up to different extents, which is closely related to the experimental hardware, however the number of illuminating beams has no significant effect on the speedup.