X-ray computed tomography (CT) system for detecting thin objects

• US 5,905,806 A
• Filed: 05/12/1997
• Issued: 05/18/1999
• Est. Priority Date: 10/20/1994
• Status: Expired due to Term

• Current Assignee: L-3 Communications Security & Detection Systems, Inc. (Leidos Holdings, Inc.)
• Original Assignee: L-3 Communications Corporation (L3Harris Technologies, Inc.)
• Inventors: Eberhard, Jeffrey Wayne, Hsiao, Meng-Ling
• Primary Examiner(s): Johns, Andrew W.
• Application Number:
  US08/854,349
• Time in Patent Office: 736 Days
• Field of Search: 382/100, 382/131, 382/154, 378/4, 378/20, 378/57, 378/62, 250/390.01, 250/390.04, 250/390.06
• US Class Current: 382/100
• CPC Class Codes: G01N 2223/419 computed tomograph
• CPC Class Codes: G01N 23/046 using tomography, e.g. computed tomography [CT]
• CPC Class Codes: G01V 5/226 using tomography

Abstract

A technique to ascertain the presence or absence of an object in a three-dimensional volume, such as explosives in the side walls of luggage. The technique involves radiation scanning the three-dimensional volume to determine a property of each of a plurality of voxels representing the three-dimensional volume and to identify voxels having similar values of the property to identify a contiguous group of voxels having the similar values. Then, the contiguous group of voxels is identified as containing the object if a characteristic (such as mass and/or volume) of the contiguous group has a predetermined value.

Claims

1. A method of detecting an explosive comprising the steps of:

(a) scanning a three-dimensional volume to determine the density of each of a plurality of voxels representing the three-dimensional volume;

(b) connecting and labeling voxels of the plurality of voxels which have similar densities using an evaluation process wherein, for a given voxel, voxels in the same plane as the given voxel, and in planes above and below the given voxel, are compared to said given voxel for contiguity;

(c) determining at least one of the volume and the mass of each contiguous region of voxels having similar densities; and

(d) comparing at least one of the volume and the mass of each contiguous region having similar densities to at least one threshold and identifying each region which exceeds a threshold as a region potentially containing an explosive.

2. A method as set forth in claim 1, wherein in said evaluation process differences between a property of said given voxel and a property of voxels in said planes above and below said given voxel are employed to evaluate contiguity.

3. A method to ascertain the presence of an explosive in a three-dimensional volume represented by a plurality of voxels, wherein the explosive is smaller in at least one dimension than a linear dimension of the voxels, the method comprising the steps of:

(a) radiation scanning the three-dimensional volume to determine a property of each of a plurality of voxels representing the three-dimensional volume;

(b) identifying voxels having similar values of said property to identify a contiguous group of voxels having said similar values using a contiguity evaluation process wherein, for a given voxel, voxels in the same plane as the given voxel, and in planes above and below the given voxel, are compared to said given voxel for contiguity; and

(c) identifying said contiguous group of voxels as potentially containing said explosive if a characteristic of said contiguous group has a predetermined value.

4. A method to ascertain the presence of a delamination in a composite material in a three-dimensional volume represented by a plurality of voxels, wherein the delamination in the composite material is smaller in at least one dimension than a linear dimension of the voxels, the method comprising the steps of:

(a) radiation scanning the three-dimensional volume to determine a property of each of a plurality of voxels representing the three-dimensional volume;

(b) identifying voxels having similar values of said property to identify a contiguous group of voxels having said similar values using a contiguity evaluation process wherein, for a given voxel, voxels in the same plane as the given voxel, and in planes above and below the given voxel, are compared to said given voxel for contiguity; and

(c) identifying said contiguous group of voxels as potentially containing said delamination in the composite material if a characteristic of said contiguous group has a predetermined value.

5. A method to ascertain the presence of an object in a three-dimensional volume represented by a plurality of voxels, wherein the object is smaller in at least one dimension than a linear dimension of the voxels, the method comprising the steps of:

(a) radiation scanning the three-dimensional volume to determine a property of each of a plurality of voxels representing the three-dimensional volume;

(b) identifying voxels having similar values of said property to identify a contiguous group of voxels having said similar values using a contiguity evaluation process wherein, for a given voxel, voxels in the same plane as the given voxel, and in planes above and below the given voxel, are compared to said given voxel for contiguity; and

(c) identifying said contiguous group of voxels as potentially containing said object if a characteristic of said contiguous group has a predetermined value, wherein said three-dimensional volume includes luggage contents.

6. An apparatus to ascertain the presence of an explosive in a three-dimensional volume represented by a plurality of voxels, wherein the explosive is smaller in at least one dimension than a linear dimension of the voxels, the apparatus comprising:

(a) a scanner to scan the three-dimensional volume; and

(b) a processor which includes

(1) a contiguity identification module to determine a property of each of a plurality of voxels representing the three-dimensional volume and to identify voxels having similar values of said property to identify a contiguous group of voxels having said similar values using a contiguity evaluation process wherein, for a given voxel, voxels in the same plane as the given voxel, and in planes above and below the given voxel, are compared to said given voxel for contiguity; and

(2) an explosive identification module to identify said contiguous group of voxels as potentially containing said explosive if a characteristic of said contiguous group has a predetermined value.

7. An apparatus to ascertain the presence of a delamination in a composite material in a three-dimensional volume represented by a plurality of voxels, wherein the delamination in the composite material is smaller in at least one dimension than a linear dimension of the voxels, the apparatus comprising:

(a) a scanner to scan the three-dimensional volume; and

(b) a processor which includes

(1) a contiguity identification module to determine a property of each of a plurality of voxels representing the three-dimensional volume and to identify voxels having similar values of said property to identify a contiguous group of voxels having said similar values using a contiguity evaluation process wherein, for a given voxel, voxels in the same plane as the given voxel, and in planes above and below the given voxel, are compared to said given voxel for contiguity; and

(2) an identification module to identify said contiguous group of voxels as potentially containing said delamination in the composite material if a characteristic of said contiguous group has a predetermined value.

8. An apparatus to ascertain the presence of an object in a three-dimensional volume represented by a plurality of voxels, wherein the object is smaller in at least one dimension than a linear dimension of the voxels, the apparatus comprising:

(a) a scanner to scan the three-dimensional volume; and

(b) a processor which includes

(1) a contiguity identification module to determine a property of each of a plurality of voxels representing the three-dimensional volume and to identify voxels having similar values of said property to identify a contiguous group of voxels having said similar values using a contiguity evaluation process wherein, for a given voxel, voxels in the same plane as the given voxel, and in planes above and below the given voxel, are compared to said given voxel for contiguity; and

(2) an object identification module to identify said contiguous group of voxels as potentially containing said object if a characteristic of said contiguous group has a predetermined value, wherein said three-dimensional volume includes luggage contents.

9. A method to ascertain the presence of an explosive in a three-dimensional volume represented by a plurality of voxels, the method comprising the steps of:

(a) radiation scanning the three-dimensional volume to determine a property of each of a plurality of voxels representing the three-dimensional volume;

(b) identifying voxels having similar values of said property to identify a contiguous group of voxels having said similar values using a contiguity evaluation process wherein, for a given voxel, voxels in the same plane as the given voxel, and in planes above and below the given voxel, are compared to said given voxel for contiguity; and

(c) identifying said contiguous group of voxels as potentially containing said explosive based on a characteristic of said contiguous group.

10. An apparatus to ascertain the presence of an explosive in a three-dimensional volume represented by a plurality of voxels, the apparatus comprising:

(a) a scanner to scan the three-dimensional volume; and

(b) a processor which includes

(1) a contiguity identification module to determine a property of each of a plurality of voxels representing the three-dimensional volume and to identify voxels having similar values of said property to identify a contiguous group of voxels having said similar values using a contiguity evaluation process wherein, for a given voxel, voxels in the same plane as the given voxel, and in planes above and below the given voxel, are compared to said given voxel for contiguity; and

(2) an explosive identification module to identify said contiguous group of voxels as potentially containing said explosive based on a characteristic of said contiguous group.