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30 August 2006 A method for superresolution in digital holography
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In this paper we concern ourselves with the subject of superresolution in Digital Holography (DH), i.e. increasing the resolution of DH system beyond its limit. The limiting factor regarding resolution in a DH system is the pixel size, which is equal to the smallest resolvable unit. By careful superposition of different digital holograms captured of the same 3-D object, we attempt to increase the resolution of the reconstructed image and equivalently to increase the range of angles of reconstruction. This is accomplished by rotating the input object wavefield either by rotation of the object (it is 2-D) or by rotation of a mirror that is placed between the object and the CCD. Rotating the input wavefield shifts the wavefield in the hologram plane in space and spatial frequency. Therefore, those parts of the hologram field that contained energy at too great an angle for recording and were therefore arranged to be adjacent to and not on the CCD will be shifted in space onto the CCD face and will also be shifted to a recordable angle. We outline a sub-pixel correlation technique to stitch the consecutive holograms together in both the space and spatial frequency domains. Multiple captures enable us to record a DH of large resolution and angle of reconstruction. Storage and reconstruction of the stitched hologram is also discussed and experimental results are given. The method may be applied with any existing form of DH. We use the Wigner Distribution Function to qualify and quantify the method.
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Bryan M. Hennelly, Thomas J. Naughton, John B. McDonald, Yann Frauel, and Bahram Javidi "A method for superresolution in digital holography", Proc. SPIE 6311, Optical Information Systems IV, 63110J (30 August 2006);

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