US 5,805,098 AGranted

Method and system for forming image by backprojection

AssigneeThe United States of America as represented by the Secretary of the Army

InventorJohn W. McCorkle

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Abstract

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.

Claims29

Dependent claims

A method of forming an image within a region, the method comprising:

(a) providing an array of sensor elements;
(b) taking data within the region over a time interval with the array of sensor elements;
(c) defining a plurality of subapertures, each of which corresponds to one of the sensor elements in the array;
(d) for each of the subapertures, forming subaperture image data by performing backprojection on the data taken with the sensor elements corresponding to said each of the plurality of subapertures;
(e) defining a plurality of further subapertures, each of which corresponds to a subplurality of the plurality of subapertures;
(f) for each of the plurality of further subapertures, forming further subaperture image data by performing backprojection on the subaperture image data formed for the subapertures corresponding to said each of the plurality of further subapertures as though each of the subapertures were a single sensor element;
(g) defining successively larger further subapertures and forming further subaperture image data for the successively larger further subapertures by repeating steps (e) and (f) until a single further subaperture corresponding to all of the sensor elements in the array is formed;
(h) forming the image in accordance with the subaperture image data for the single further subaperture;
and
(i) outputting the image to a display device.

7 more elements

A system for of forming an image within a region, the system comprising:

(a) an array of sensor elements for taking data within the region over a time interval;
(b) backpropagation means, receiving the data, for:
(i) defining a plurality of subapertures, each of which corresponds to a plurality of the sensor elements in the array;
(ii) for each of the subapertures, forming subaperture image data by performing backprojection on the data taken with the sensor elements corresponding to said each of the plurality of subapertures;
(iii) defining a plurality of further subapertures, each of which corresponds to a subplurality of the plurality of subapertures;
(iv) for each of the plurality of further subapertures, forming further subaperture image data by performing backprojection on the subaperture image data formed for the subapertures corresponding to said each of the plurality of further subapertures as though each of the subapertures were a single sensor element;
(v) forming successively larger further subapertures and forming further subaperture image data for the successively larger further subapertures by repeating operations (iii) and (iv) until a single further subaperture corresponding to all of the sensor elements in the array is formed;
(vi) forming the image in accordance with the subaperture image data for the single further subaperture;
and
(c) a display device for displaying the image.

7 more elements

Dependencies are inferred from the claim text.