Interrupted-fan-beam imaging
OwnerSteven W. Smithinventor
Life of this patent
Estimating the term…
Abstract
Interrupted-Fan-Beam imaging is a method of producing back-scatter x-ray images from conventional line scan systems, such as those used for luggage and cargo inspection. Since back-scatter and transmission images are formed from different physical principles, the use of both images provides a more thorough security inspection. A mathematical relation relates the signal-to-noise ratio to the spatial resolution in an Interrupted-Fan-Beam image. When used in conjunction with typical operating values of x-ray systems, such as flux level and number of pixels, this relation provides the performance level of the Interrupted-Fan-Beam technique.
Claims19
An imaging system for inspecting a target object, comprising:
- an x-ray source for producing a fan beam of x-rays directed toward the target object along a scan line of a plurality of scan lines;
- a fan beam stop comprising at least one radial arm having an arm width extending from a rotating axis to intersect the fan beam, the radial arm interrupting a portion of the fan beam as the at least one radial arm rotates through the fan beam;
- a transmission x-ray detector positioned in the scan line of the fan beam for producing a transmission signal representative of a portion of the target object intersecting the scan line;
- an inspection surface positioned between the x-ray source and the transmission x-ray detector for moving the target object through the fan beam;
- at least one back-scatter detector positioned within a detection range of the inspection surface for receiving x-rays scattered from the objects and for producing a back-scatter signal representative of the intensity of the x-rays scattered from the objects, wherein the spatial resolution along the scan line is obtained by the radial arm interruption of the fan beam, and wherein each interrupted portion of the fan beam defines a pixel of the back-scatter signal;
- and
- a processing means for producing a back-scatter image from the back-scatter signal and a transmission image from the transmission signal to produce an image of the objects.
An x-ray detector system for producing images of target item, the system comprising:
- an x-ray source for producing a fan beam of x-rays, the fan beam of x-rays having a fan beam width;
- a means for passing the target item through the fan beam of x-rays;
- at least one large area x-ray collector positioned proximate to the target item for detecting x-rays scattered from the target item and for producing a back-scatter signal representative of the intensity of the scattered x-rays, the back-scatter signal comprising a baseline portion;
- and
- a rotating beam-stop positioned between the x-ray source and the transporting means, the rotating beam-stop comprising at least one radial arm for blocking a portion of the fan beam as the at least one radial arm rotates through the fan beam width;
- wherein the rotating beam-stop creates a depression in the baseline portion indicating the presence of the target item.
A method for scanning a target object to produce an image, comprising the steps of:
- generating a fan-beam of x-rays having a fan-beam width, the fan-beam producing a scan line;
- blocking a sequence of equal portions of the fan-beam across the fan-beam width, each equal portion defining a pixel;
- moving the target object through the fan-beam, the target object intersecting the fan-beam along the scan line;
- collecting back-scatter x-rays that are scattered from the target object;
- generating a backscatter image signal from the collected back-scatter x-rays, comprising the steps of:
- establishing a baseline value representative of the total number of x-rays scattered anywhere along the scan line;
- and
- indicating a lowering of the baseline value resulting from the blocking of the fan-beam when the pixel is aligned with the target object.
A method for inspecting an object, the method comprising the steps of:
- producing a fan beam of a plurality of x-rays along a scan line during a scanning cycle;
- directing the fan beam towards the object wherein the object absorbs, transmits, or scatters at least some of the plurality of x-rays;
- interrupting sequential portions of the fan beam utilizing a rotating fan beam stop having at least one radial arm, the radial arm having a width for blocking a subset of the plurality of x-rays;
- synchronizing the rotation of the fan beam stop with the scanning cycle;
- collecting the transmitted x-rays of the plurality of x-rays and producing a transmission signal representative of the object during the scanning cycle;
- collecting the back-scattered x-rays of the plurality of x-rays and producing a back-scatter signal representative of the intensity of the x-rays;
- and
- establishing a spatial resolution of the back-scatter signal based upon the blocked subset of the plurality of x-rays.
Dependencies are inferred from the claim text.