Minimum-entropy autofocus for three-dimensional SAR imaging

The image focus quality of multiple-pass 3D SAR imagery strongly depends on the accuracy of the between-pass coherent image alignment. We present a method for forming a 3D SAR image from multiple coherently aligned 2D SAR images collected at different viewing geometries, where the joint coherent alignment is performed by directly optimizing the 3D SAR image entropy. Image entropy based focusing is inherently data-adaptive and imposes only minimal assumptions about the SAR imagery such as it having a non-Gaussian distribution, as opposed to interferometric based methods which typically rely on the assumption of one or a few bright scatterers per resolution cell. We will show examples of coherently aligning and focusing 3D SAR imagery using both simulated as well as measured multiple-pass SAR imagery.

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