3 June 2014 Defocus-based quantitative phase imaging by coded illumination
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Abstract
The Transport of Intensity equation (TIE) solves for the complex field at a plane of interest using intensity measurements at multiple defocus planes. Patterning the illumination enables multiplexing at the source instead of the detector, enabling quantitative phase without any moving parts. A general theory is formulated here to describe the defocus coupling of the illumination and object fields, providing a joint framework for analyzing grating interferometry and defocus based phase imaging methods. We use the theory to devise a measurement scheme that isolates object phase gradients by combining defocus images for different illumination patterns, using sinusoidal illumination as an example. Since the phase image recovered corresponds to a first derivative of phase, it is expected to have better low frequency noise resilience than the traditional TIE, which measures the second derivative of phase. The method is validated in simulations, and subsequently in experiments using a spatial light modulator.
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Aamod Shanker, Lei Tian, Laura Waller, "Defocus-based quantitative phase imaging by coded illumination", Proc. SPIE 8949, Three-Dimensional and Multidimensional Microscopy: Image Acquisition and Processing XXI, 89490R (3 June 2014); doi: 10.1117/12.2039977; https://doi.org/10.1117/12.2039977
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