6 September 2017 Modeling coherence propagation in a homogenizing light pipe for speckle mitigation
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A homogenizing light pipe provides an avenue of altering the spatial coherence properties of a laser source for the purpose of reducing speckle in an active imaging scenario. In this study, an efficient coherent mode decomposition was used to characterize the effect of a light pipe on the coherence properties of an input beam. The waveguide was found to reduce the global degree of coherence of the input beam in a manner which made the beam more suitable as an illuminator for speckle free imaging. The beam exiting the waveguide was found to contain a banded mutual coherence function due to the strong presence of symmetry within the setup. A formula for predicting the speckle contrast in the presence of these bands is proposed in the paper and appears to show great agreement with simulated results. The efficient propagation method and speckle contrast formula presented in the paper should be useful in designing an optimal active illumination source for reducing speckle.
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Robert A. Raynor, Robert A. Raynor, Mark F. Spencer, Mark F. Spencer, Trevor D. Moore, Trevor D. Moore, "Modeling coherence propagation in a homogenizing light pipe for speckle mitigation", Proc. SPIE 10410, Unconventional and Indirect Imaging, Image Reconstruction, and Wavefront Sensing 2017, 104100X (6 September 2017); doi: 10.1117/12.2274641; https://doi.org/10.1117/12.2274641

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