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.

[1]  Michael T. Orchard,et al.  A fast direct Fourier-based algorithm for subpixel registration of images , 2001, IEEE Trans. Geosci. Remote. Sens..

[2]  Robert A. Weisenseel,et al.  Surface models to constrain three-dimensional sparse SAR reconstruction , 2009, Defense + Commercial Sensing.

[3]  Randolph L. Moses,et al.  SAR imaging from partial-aperture data with frequency-band omissions , 2005, SPIE Defense + Commercial Sensing.

[4]  Manuel Guizar-Sicairos,et al.  Efficient subpixel image registration algorithms. , 2008, Optics letters.

[5]  Thomas J. Kragh,et al.  Monotonic Iterative Algorithms for SAR Image Restoration , 2006, 2006 International Conference on Image Processing.

[6]  S. Quegan,et al.  Understanding Synthetic Aperture Radar Images , 1998 .

[7]  J. Kolman.  PACE: an autofocus algorithm for SAR , 2005, IEEE International Radar Conference, 2005..

[8]  J J Miller,et al.  Aberration correction by maximizing generalized sharpness metrics. , 2003, Journal of the Optical Society of America. A, Optics, image science, and vision.

[9]  Forest Lee-Elkin.  Autofocus for 3D imaging , 2008, SPIE Defense + Commercial Sensing.

[10]  Gianfranco Fornaro,et al.  Three-dimensional multipass SAR focusing: experiments with long-term spaceborne data , 2005, IEEE Transactions on Geoscience and Remote Sensing.

[11]  Thomas M. Cover,et al.  Elements of Information Theory , 2005 .

[12]  Kostas Papathanassiou,et al.  First demonstration of airborne SAR tomography using multibaseline L-band data , 1999, IEEE 1999 International Geoscience and Remote Sensing Symposium. IGARSS'99 (Cat. No.99CH36293).

[13]  Charles V. Jakowatz,et al.  Spotlight-Mode Synthetic Aperture Radar: A Signal Processing Approach , 1996 .

[14]  LeRoy A. Gorham,et al.  A challenge problem for 2D/3D imaging of targets from a volumetric data set in an urban environment , 2007, SPIE Defense + Commercial Sensing.

[15]  J R Fienup,et al.  Synthetic-aperture radar autofocus by maximizing sharpness. , 2000, Optics letters.

[16]  A. F. Yegulalp.  Analysis of SAR Image Formation Equations for Stationary and Moving Targets , 2002 .

[17]  C.V. Jakowatz,et al.  Three-dimensional tomographic imaging for foliage penetration using multiple-pass spotlight-mode SAR , 2001, Conference Record of Thirty-Fifth Asilomar Conference on Signals, Systems and Computers (Cat.No.01CH37256).

[18]  Minh N. Do,et al.  SAR Image Autofocus By Sharpness Optimization: A Theoretical Study , 2007, IEEE Transactions on Image Processing.