Accession Number : ADA227728


Title :   Shift-Invariant Image Reconstruction of Speckle-Degraded Images Using Bispectrum Estimation


Descriptive Note : Master's thesis,


Corporate Author : AIR FORCE INST OF TECH WRIGHT-PATTERSON AFB OH


Personal Author(s) : Wear, Steven M


Full Text : https://apps.dtic.mil/dtic/tr/fulltext/u2/a227728.pdf


Report Date : May 1990


Pagination or Media Count : 157


Abstract : Coherent speckle noise as a multiplicative noise process that has a negative exponential probability density function. Using a homomorphic transformation, this speckle noise is converted to a signal-independent, additive process. The speckled images are randomly jittered from frame-to-frame against a uniform background to simulate image motion and/or platform jitter. Multiple images are logarithmically transformed and ensemble averaged in the bispectral domain. The bispectrum ignores this image motion so no blurring results from the ensemble averaging. Object Fourier magnitude and phase information are also retained in the bispectrum so that the resultant image can be uniquely reconstructed. This value is then exponentiated to complete the image reconstruction process. Since speckle masks the resolution of details in the noisy image and effectively destroys the object structure within the image, it is seen that image reconstruction using bispectrum estimation results in images that regain their object structure. Both one-dimensional and two- dimensional images were tested using separate bispectral signal reconstruction algorithms for each. (RH)


Descriptors :   *MULTIPLICATION FACTOR , *SPECULAR REFLECTION , *NOISE , IMAGES , ADDITIVES , MASKS , MOTION , COHERENCE , TWO DIMENSIONAL , BACKGROUND


Subject Categories : Radiofrequency Wave Propagation


Distribution Statement : APPROVED FOR PUBLIC RELEASE