18 June 2007 Phase retrieval using a random amplitude mask for wavefront sensing
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3D imaging of wavefronts for the characterization of an object with which it interacts is an interesting and challenging problem. Wavefront sensing or the measurement of the deviations from an ideal wavefront yields valuable information of the object under study such as refractive index distribution, density distribution and temperature profile. Traditional phase reconstruction methods like holography involves a complicated setup and procedure and methods based on the Shack-Hartmann sensor have poor spatial resolution. In this study, an alternative wavefront sensor based on a phase retrieval method and a random amplitude mask is proposed. The main advantages of the proposed wavefront sensor are high resolution in the order of a few microns, accurate and fast-convergent phase reconstruction and a simple setup. The principles of the technique and the algorithm of the phase retrieval method are described in detail. The functions of the main components of the proposed sensor which include a mask, an imaging sensor and a computerized phase retrieval algorithm are also discussed. The dependences of the accuracy of the phase reconstructions on the number of intensity recordings and iterations are investigated. It was observed that about 16 intensity recordings and 5-7 iterations are sufficient to obtain a convergence between the calculated phase and the true phase. An initial random guess phase was also found to result in a faster rate of convergence as compared to an initial constant guess phase. Experimental implementation the proposed wavefront sensor is demonstrated.
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Arun Anand, Arun Anand, Giancarlo Pedrini, Giancarlo Pedrini, Wolfgang Osten, Wolfgang Osten, Percival Almoro, Percival Almoro, } "Phase retrieval using a random amplitude mask for wavefront sensing", Proc. SPIE 6617, Modeling Aspects in Optical Metrology, 66170J (18 June 2007); doi: 10.1117/12.725874; https://doi.org/10.1117/12.725874

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