Aperture synthesis in phase retrieval using a volume-speckle field.
ABSTRACT The resolution of the reconstructed wave by a phase-retrieval method using a volume-speckle field depends on the aperture defined by the size of the CCD array. The use of a larger aperture is introduced by measuring the speckle field at two different positions in the transverse plane and stitching the measurements together. Improvements in the quality of reconstructions are demonstrated experimentally and by computer simulations. Undesirable effects of camera tilt on the quality of reconstructions from synthetic aperture intensity measurements are experimentally observed and corrected.
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ABSTRACT: An innovative setup for the speckle-based phase retrieval method is proposed. In the conventional setup, a plane wave illuminates the test object and the transmitted wavefront is incident on a diffuser aperture generating a speckle field. The sampled speckle intensities at axially displaced planes are input into a phase retrieval algorithm based on a wave propagation equation. In the new setup, the arrangement of the diffuser and the object is reversed. A plane wave incident on the diffuser generates a speckle field which, in turn, is used to illuminate the object. The transmitted wavefront is then directed to the camera sensor. The advantage of the proposed setup is the increased resolution since the limiting aperture is the full area of the sensor.Journal of The European Optical Society-rapid Publications - J EUR OPT SOC-RAPID PUBL. 01/2009;
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ABSTRACT: We demonstrate the effectiveness of the nonlocal means (NLM) filter for speckle denoising in digital holography. The speckle noise adapted version of the NLM filter is compared with other common speckle denoising filters and is found to give better visual and quantitative results.Applied Optics 01/2013; 52(1):A195-200. · 1.69 Impact Factor
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ABSTRACT: Recently proposed lensless object scanning holography (LOSH) [Opt. Express20, 9382 (2012)] is a fully lensless method capable of improving the image quality in digital Fourier holography applied to one-dimensional (1D) reflective objects and it involves a very simplified experimental setup. LOSH is based on the recording and digital postprocessing of a set of digital lensless Fourier transform holograms, which finally results in a synthetic image with improved resolution, field-of-view (FOV), signal-to-noise ratio (SNR), and depth of field. In this paper, LOSH is extended to the cases of two-dimensional (2D) mirror-like and 1D diffuse-based objects. For 2D mirror-like objects, the experimental results show an impressive image quality improvement over a factor of 3 in FOV, SNR, and resolution, as good as that obtained for the 1D case but in two dimensions. For 1D diffuse-based objects, in general the speckle affects the image resolution, which will not be only a function of the aperture size. In this case, increasing the aperture produces a decrease of the speckle size. Moreover, due to the overlapping of speckles between successive images, different types of digital processing can be applied to obtain the final synthetic image: fully incoherent, fully coherent, and partially coherent. The last, arising from the incoherent sum of several independent sets of coherently added images, provides the best improvement in the resolution. Experimental results for both types of objects are presented.Applied Optics 09/2013; 52(25):6390-6400. · 1.69 Impact Factor