Image Number 13 for United States Patent #5805098.
The method and system quickly and simultaneously generate multi-resolution and high-resolution imagery from projection data obtained, e.g., through synthetic aperture radar, magnetic resonance imaging, x-ray CAT scans, seismic imaging, sonar imaging, and acoustic imaging. The backprojector technique is modified by a quadtree decomposition of the image area. The sensor elements are grouped into subapertures, and an image is formed in each subaperture by backprojection. The subapertures are grouped into larger subapertures and an image is formed in each of the larger subapertures by backprojection. This operation is repeated until a single large subaperture is defined which covers the entire antenna array. In this way, common additions are factored, computed once and reused many times. A set of N projections can produce an N.times.N image through O(N.sup.2 log N) operations.