Prof Justin Dauwels, Ultrafast noise-resilient phase reconstruction from intensity images @13:30 @ C700

Dear All,

Structural Cellular Biology Unit (Skoglund) would like to invite you to the Seminar by Professor Justin Dauwels.

[SEMINAR 2]

Date: Tuesday, June 30, 2015
Time: 13:30 – 14:30
Venue: Seminar Room C700, Lab 3
Speaker: Professor Justin Dauwels
Affiliation: Nanyang Technological University, Singapore

Title: Ultrafast noise-resilient phase reconstruction from intensity images.

Abstract:

Quantitative phase imaging has applications in biology and surface metrology, since objectsof interest often do not absorb light but cause measurable phase delays. Phase cannot be directly measuredby a camera, and so phase objects are invisiblein an in focus imagingsystem because they are transparent. Phase can be recoveredfrom a series of images taken with variouscomplex transfer functions. Methods that use intensityimages measured through focus are especiallyinteresting because they have the advantage of a simple experimental setup and wide applicability. The stack of defocused intensity images can be obtainedin an imaging system with an axial motion stage, which represents a typical microscope.
We propose a novel low-complexity recursive filter to efficiently  recover quantitative phase from a series of noisy intensity images taken through focus. We first transform the wave propagation equation and nonlinear observation model (intensity measurement) into a complex augmented state space model. From the state space model, we derive a sparse augmented complex extended Kalman filter (ACEKF) to infer the complex  optical  field  (amplitude  and  phase),  and  find  that  it  converges  under  mild conditions. The proposed method is efficient, robust and recursive, and may be feasible for real-time phase recovery applications with high resolution images.
We have also extended this method to phase retrieval from a stack of through-focus intensity images taken with a microscope employing partially coherent illumination of any arbitrary source shape (coherence) in Köhler geometry.  We recover not only the quantitative phase and amplitude distributions of the sample under partially coherent illumination, but also an estimate of the unknown source shape itself. Our algorithm uses a Kalman filtering approach which is fast, accurate and robust to noise. We validate the method experimentally with a commercial microscope having varying condenser aperture shapes.  The method is experimentally simple and the algorithm is general for all wave-field imaging, so should find use in optical, X-ray and other phase imaging systems.  This is joint work with Jingshan Zhong, Dr. Lei Tian, and Dr. Laura Waller from UC Berkeley.
Bio:

Justin DAUWELS is an Assistant Professor with School of Electrical & Electronic Engineering at Nanyang Technological University (NTU). He is also the Deputy Director of ST Engineering-NTU Corporate Lab and the Director of Neuroengineering Program at the School of EEE. His research interests are in Bayesian statistics, iterative signal processing, machine learning and computational neuroscience. Prior  to  joining  NTU,  Justin  was  a  research  scientist  during  2008-2010  in  the Stochastic Systems Group (SSG) at the Massachusetts Institute of Technology, led by Prof. Alan Willsky. He received postdoctoral training during 2006-2007 under the guidance of Prof. Shun-ichi Amari and Prof. Andrzej Cichocki at the RIKEN Brain Science Institute in Wako-shi, Japan. He obtained  his  PhD  degree  in  electrical  engineering  from  the  Swiss  Polytechnical  Institute  of Technology (ETH) in Zurich in December 2005. The research of his lab has been featured by BBC Click/World News, Singapore Straits Times, national TV, and various other media. Outcomes include  real-time  algorithms  for  large-scale  urban  traffic  prediction;  real-time  algorithms  for analysing human social behaviour; real-time noise-resilient algorithms for phase imaging; novel data analytics for biomedical signals; tools for large-scale modelling of extreme events.

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Hope to see many of you at the Seminar.

Best Regards,
Structural Cellular Biology Unit (Skoglund)