Poster Abstract for AIP Congress 2002 - AOS Interest Group Stream
Adrian P. MANCUSO, and Keith A. NUGENT
Optics Group
School of Physics
The University of Melbourne
3010
Phone: +61 3 8344 7186
Fax:+61 3 9347 4783
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Improved Resolution Phase Imaging Using a Hybrid TIE/Oversampling Method
The problem of imaging objects according to their refractive (phase) properties, as opposed to their absorption is one that has been investigated in a variety of ways, not least because of the range of practical applications such as phase tomography. One such method involves solving a differential equation known as the Transport of Intensity Equation (TIE)[1] , and another involves oversampling the diffraction pattern of an object which allows an iterative reconstruction of the phase.[2]
TIE phase retrieval has been successfully demonstrated across a range of applications and radiations1,[3],[4]. Significantly, it provides a solution to the phase problem from a series of intensity images alone, but at present the resolution of the phase image produced is limited by the imaging system used. The oversampling method has the advantage of being able to provide a higher resolution output than the TIE method, but due to the iterative nature of this method convergence and stability issues currently limit the applicability of this solution.
This work demonstrates a simple method that aims to overcome the limitations of the two methods above by hybridising the benefits of each. Imaging and diffraction data can be readily collected with minor modifcations to experiemental apparatus. By utilising the information contained in the lower resolution TIE image a significant constraint can be applied to the iterative method. The goal is to use this low spatial frequency information to better constrain the solution space of the oversampling algorithm and recover higher resolution phase images.
Simulated results will be presented along with, if possible, their comparison with experiment.
[1] K. A. Nugent, T. E. Gureyev, D. Cookson, D. Paganin, and Z. Barnea, Phys. Rev. Lett. 77, 2961 (1996)
[2] J. Miao, D. Sayre, and H. N. Chapman, J. Opt. Soc. Am. A, 15, 1662 (1998)
[3] B. E. Allman, P. J. McMahon, K. A. Nugent, D. Paganin, D. L. Jacobson, M. Arif, and S. A. Werner, Nature (London) 408, 158 (2000)
[4] K. A. Nugent, D. Paganin and T. E. Gureyev, Physics Today, 54 No. 8, 27 (2001)