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28 August 2010 3D pupil plane imaging of opaque targets
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Correlography is a technique that allows image formation from non-imaged speckle patterns via their relationship to the autocorrelation of the scene. Algorithms designed to form images from this type of data represent a particular type of phase retrieval algorithm since the autocorrelation function is related to the Fourier magnitude of the scene but not the Fourier phase. Methods for forming 2-D images from far field intensity measurements have been explored previously, but no 3-D methods have been put forward for forming range images of a scene from this kind of measurement. Farfield intensity measurements are attractive large focusing optics are not required to form images. Pupil plane intensity imaging is also attractive due to the fact that the effects of atmospheric turbulence close to the imaging system are mitigated by the cancelation of phase errors in the intensity operation. This paper suggests a method for obtaining 3-D images of a scene through the use of successive 2-D pupil plane intensity measurements sampled with an APD (Avalanche Photo-Diode) array. The 2-D array samples the returning pulse from a laser at a fast enough rate to avoid aliasing of the pulse shape in time. The spatial pattern received by the array allows the Autocorrelation of the scene to be determined as a function of time. The temporal autocorrelation function contains range information to each point in the scene illuminated by the pulsed laser. The proposed algorithm uses a model for the LADAR pulse and its relation to the autocorrelation of the scene as a function of time to estimate the range to every point in the reconstructed scene assuming that all surfaces are opaque (meaning a second return from the same point in the scene is not anticipated). The method is demonstrated using a computer simulation.
© (2010) COPYRIGHT Society of Photo-Optical Instrumentation Engineers (SPIE). Downloading of the abstract is permitted for personal use only.
Stephen C. Cain "3D pupil plane imaging of opaque targets", Proc. SPIE 7818, Adaptive Coded Aperture Imaging, Non-Imaging, and Unconventional Imaging Sensor Systems II, 78180W (28 August 2010);

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