Free-hand scanning and imaging
First Claim
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1. A wideband synthetic aperture radar (SAR) imaging system, comprising:
- a probe having an aperture through which a signal is transmitted incident to an object located in a medium of interest remotely from the probe and through which a plurality of nonuniformly sampled reflected signals from the object are received by the probe as the probe moves in a measurement plane located a predetermined distance from the object;
a memory for storing measurement data representative of the reflected signals collected by the probe;
a processor for executing a plurality of computer-executable instructions for a SAR-based reconstruction algorithm, said instructions comprising;
instructions for performing a spectral estimation based on the measurement data;
instructions for transforming a frequency component of the spectral estimation as a function of the medium of interest;
instructions for obtaining an intermediate three-dimensional SAR image from the transformed spectral estimation data using Fourier transforms;
instructions for segmenting the intermediate three-dimensional SAR image into a plurality of segments in an image domain, wherein each segment includes a spatial bandwidth of a plurality of spatial bandwidths of the intermediate three-dimensional SAR image;
instructions for transforming each of the plurality of segments from the image domain to a measurement domain, wherein each of the plurality of segments is represented as partial data;
instructions for performing an optimization operation on each of the plurality of segments based on a comparison between the partial data thereof and the measurement data;
instructions for recombining the plurality of segments to produce a final three-dimensional SAR image; and
a display responsive to the processor for presenting the final three-dimensional SAR image to a user.
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Abstract
Wideband synthetic aperture radar (SAR) imaging. A probe transmits a signal through its aperture incident to an object located in a medium of interest remotely from the probe. The probe receives through the aperture a plurality of nonuniformly sampled reflected signals from the object as the probe moves in a measurement plane located a predetermined distance from the object. A processor executes a SAR-based reconstruction algorithm to generate an image.
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Citations
23 Claims
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1. A wideband synthetic aperture radar (SAR) imaging system, comprising:
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a probe having an aperture through which a signal is transmitted incident to an object located in a medium of interest remotely from the probe and through which a plurality of nonuniformly sampled reflected signals from the object are received by the probe as the probe moves in a measurement plane located a predetermined distance from the object; a memory for storing measurement data representative of the reflected signals collected by the probe; a processor for executing a plurality of computer-executable instructions for a SAR-based reconstruction algorithm, said instructions comprising; instructions for performing a spectral estimation based on the measurement data; instructions for transforming a frequency component of the spectral estimation as a function of the medium of interest; instructions for obtaining an intermediate three-dimensional SAR image from the transformed spectral estimation data using Fourier transforms; instructions for segmenting the intermediate three-dimensional SAR image into a plurality of segments in an image domain, wherein each segment includes a spatial bandwidth of a plurality of spatial bandwidths of the intermediate three-dimensional SAR image; instructions for transforming each of the plurality of segments from the image domain to a measurement domain, wherein each of the plurality of segments is represented as partial data; instructions for performing an optimization operation on each of the plurality of segments based on a comparison between the partial data thereof and the measurement data; instructions for recombining the plurality of segments to produce a final three-dimensional SAR image; and a display responsive to the processor for presenting the final three-dimensional SAR image to a user. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9, 10, 11)
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12. A method of generating a three dimensional image of a specimen under test (SUT) comprising:
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transmitting, via a probe, a signal within a predetermined operating bandwidth; tracking nonuniform two-dimensional movement of the probe within a measurement plane remote from the SUT; receiving, via the probe, signals reflected from the SUT during the movement of the probe; storing reflection coefficient data based on the reflected signals as distributed measurement positions within the measurement plane by recording the signals at discrete frequencies throughout the operating bandwidth; processing the stored data into a wide band, synthetic aperture image by implementing a synthetic aperture radar (SAR) algorithm; displaying the image to a user in real-time; further processing the image to perform an optimization objective, wherein the optimization includes reducing the error between components derived from a SAR-based transform and an R-SAR-based transform; and further displaying the optimized image to the user. - View Dependent Claims (13, 14, 15, 16, 17, 18, 23)
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19. A wideband synthetic aperture radar (SAR) imaging system, comprising:
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a signal source for generating a signal with a predetermined operating bandwidth; a transceiver antenna coupled to the signal source, the antenna having an aperture through which the signal is transmitted incident to an object located in a medium and through which a plurality of nonuniformly sampled reflected signals from the object are received by the antenna as the antenna moves nonuniformly in a plane located a predetermined distance from the object; a memory for storing signal data, the signal data comprising nonuniformly sampled reflected signals collected at the aperture; a processor executing a plurality of computer-executable instructions for a real-time, post-processing, reconstruction algorithm comprising; instructions for estimating a two-dimensional spatial spectrum based on the signal data to provide a uniformly sampled spectrum; instructions for estimating the uniformly sampled spectrum to remove or minimize image artifacts; instructions for reconstructing uniformly sampled data from nonuniformly sampled data to remove or minimize image artifacts; instructions for forming a SAR image of the object from the estimated uniform spectrum; instructions for dividing the reconstructed SAR image into a plurality of segments; instructions for applying a R-SAR transform to each of the segments; instructions for filtering and reconstructing the data for each of the segments and summing each of the filtered segments to create reconstructed data; instructions for applying a SAR transform to the reconstructed data to create a three-dimensional SAR image; and a display for presenting the three-dimensional SAR image to a user. - View Dependent Claims (20, 21, 22)
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Specification