Thursday, September 27, 2012

Alternating Direction Methods for Classical and Ptychographic Phase Retrieval

Stefano just sent me the following:

Hi Igor,
I'd like to bring your attention to some references on phase retrieval, I hope you enjoy the links:
a presentation by Filipe Maia on Multi-GPU Real-Time Ptychographic X-ray Image Reconstruction at
some diffraction data is available here :
see also this (By Filipe Maia):
Thanks Stefano .Here are the two papers:

Abstract. In this paper, we show how augmented Lagrangian alternating direction method (ADM) can be used to solve both the classical and ptychographic phase retrieval problems. We point out the connection between ADM and projection algorithms such as the hybrid input-output (HIO) algorithm, and compare its performance against standard algorithms for phase retrieval on a number of test images. Our computational experiments show that ADM appears to be less sensitive to the choice of relaxation parameters, and it usually outperforms the existing techniques for both the classical and ptychographic phase retrieval problems.

Ptychography is a popular technique to achieve diffraction limited resolution images of a two or three dimensional sample using high frame rate detectors. We introduce a relaxation of common projection algorithms to account for instabilities given by intensity and background fluctuations, position errors, or poor calibration using multiplexing illumination. This relaxation introduces an additional phasing optimization at every step that enhances the convergence rate of common projection algorithms. Numerical tests exhibit the exact recovery of the object and the noise when there is high redundancy in the data.

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Anonymous said...

Is the source code available ?

Anonymous said...

Is the source code available for download ?

Igor said...

Ask Stephano directly. If it is available, please let me know.