1 September 2009 Real world objects: capturing using in-line digital holography, projecting using spatial light modulators
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Abstract
Digital holography is the process where an object's phase and intensity information is retrieved from intensity images obtained using a digital camera (CCD or CMOS sensor). Unlike off-axis holography, object information is not modulated onto carrier fringes, thus in-line digital holography makes optimum use of the recording device's sampling bandwidth resulting in higher resolution digital holograms. However, reconstructed images are obscured by the linear superposition of the unwanted out of focus twin images. In addition to this, speckle noise degrades overall quality of the reconstructed images. The speckle effect is an optical phenomenon arising when laser sources are used in digital holographic systems. Minimizing the effects due to speckle noise, removal of the twin image and using the full sampling bandwidth of the capture device, aids overall reconstructed image quality. Using interferometric techniques, it is possible to record whole field information about an object. Digital processing of the reconstructed holograms can remove or suppress the twin image while effects from speckle noise can also be reduced numerically. Machine vision techniques can then be applied to segment and distinguish objects of interest in the hologram. Coding the resulting phase information onto a spatial light modulator (SLM), real world, three dimensional images of objects can be reconstructed using the computer generated hologram.
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James P. Ryle, James P. Ryle, David S. Monaghan, David S. Monaghan, Susan McDonnell, Susan McDonnell, John T. Sheridan, John T. Sheridan, } "Real world objects: capturing using in-line digital holography, projecting using spatial light modulators", Proc. SPIE 7442, Optics and Photonics for Information Processing III, 74421B (1 September 2009); doi: 10.1117/12.826885; https://doi.org/10.1117/12.826885
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