| 摘要 |
A SAR image auto-focus method uses statistics extracted from the image data to develop a phase pure hyperbolic correction function. The method processes an uncorrected azimuth line vector selected from an unfocused array into a corrected azimuth line vector. The method includes forming a bright spot list based on the selected uncorrected azimuth line vector where the bright spot list has at least one bright spot entry. Then, the uncorrected azimuth line vector is unpacked into an uncorrected segment set that has a first uncorrected segment corresponding to a first bright spot entry in the bright spot list. Then, the first uncorrected segment is processed into a first corrected segment based on an average phase slope corresponding to the first bright spot entry, the first corrected segment is packed into the corrected azimuth line vector, and the process repeated for all bright spots. The step of processing the first uncorrected segment into a first corrected segment includes processing the first uncorrected segment through a Fourier transform into an uncorrected spectrum vector, correcting the uncorrected spectrum vector to form a corrected spectrum vector, processing the corrected spectrum vector through an inverse Fourier transform into the first corrected segment. The step of correcting the uncorrected spectrum vector includes computing phase gradient phi dot(f) at each frequency f in the uncorrected spectrum vector based on: phi dot(f)=Im {G(f).+574 G'(f)}/(2 pi |G(f)|2),then computing the average phase slope by averaging the phase gradient determined at each frequency in the uncorrected spectrum vector. Then a correction function vector corresponding to the average phase slope is generated, and the uncorrected spectrum vector is multiplied by the correction function vector, element by element, to form the corrected spectrum vector.
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