Papers by Keyword: Phase Retrieval

Abstract: The reconstruction quality of in-line holography suffers from the superposition of twin images, which blurs the details and degrades the quality of the object wavefront reconstruction. We present an iterative reconstruction method to eliminate twin image and truthfully retrieve the object wavefront. This algorithm has a better elimination effect and more rapid rate of convergence than other phase retrieval methods. An experimental setup was built with dual cameras recording the holograms simultaneously, thus this technique can be employed for investigating fast dynamic phenomina. The effectiveness of the proposed method is validated using different samples.

Abstract: Phase retrieval from fringe patterns is a primary procedure in fringe projection profilometry. Only accurate phase values result in three dimensions with certain accuracy. Phase shifting method plus temporal phase unwrapping approach provides not only the unwrapped absolute phase, but also the modulation map, background map, root mean square errors of least squares fitting, and phase relationship between two neighboring pixels, which can be used for the identification of phase invalidity. A practical phase retrieval frame work is presented to accurately calculate the absolute phase within reliable regions only, with which those unavailable phase points can be automatically identified with thresholds selection and criterion testing and then removed or interpolated according to applications. Experimental results show practical feasibility of the proposed framework.

Abstract: A novel algorithm and experiment using phase retrieval to test aspheric mirror without auxiliary optical elements has been developed. To test aspheric mirror without auxiliary optical elements, a new algorithm has been invented to overcome the calculation difficulty due to the significant departure of aspheric surface from a sphere. In this algorithm, the aspheric surface is fitted into several annular ellipse sub-apertures, and each sub-aperture aberration can be retrieved the same as ball mirror testing. The whole aspheric surface can be retrieved by stitching all the subapertures together. An experiment has been carried out to test the validity of this algorithm.