Body scanner with automated target recognition
This Invention is directed at the automated analysis of body scanner images. Body scanners are used in airports and other secured facilities to detect weapons, explosives, and other security threats hidden under persons' clothing. These devices use x-rays, millimeter waves and other radiant energy to produce an electronic image of the person's body and any concealed objects. Examination of these images by human analysts is slow, expensive, and subject to privacy concerns. The Invention provides automated analysis of body scanner images by recognizing that human anatomy is bilaterally symmetric to a high degree, while concealed objects are asymmetric. Digital techniques are used to separate the scanned image into its symmetric and asymmetric parts, thereby effectively separating anatomic from non-anatomic image features.
1. A method for performing automated target recognition on a body scanner image of a subject, comprising:
receiving by a digital computer, said body scanner image;
spatially warping, by the digital computer, the body scanner image to generate a warped electronic image by:
determining an outline of the body scanner image;
identifying symmetric fiducials on said outline, wherein a first fiducial and a corresponding second fiducial is symmetric about a vertical axis centered along said subject;
transforming the symmetric fiducials into symmetric quadrilateral pairs; and
warping the symmetric quadrilateral pairs based on coordinates of the symmetric quadrilateral pairs;
receiving by the digital computer, first data from a first location in said body scanner image corresponding to a first warped location in the warped electronic image;
receiving by the digital computer, second data from a second location in said body scanner image, the second location corresponding to a second warped location in the warped electronic image, said second location being bilaterally symmetric to said first location, and said second location being derived from the first location;
comparing, by the digital computer, one or more imaging characteristics exposed by said first data with one or more imaging characteristics exposed by said second data to detect a match;
upon determining that a match exists between the one or more imaging characteristics exposed by said first data and the one or more imaging characteristics exposed by said second data, identifying, by the digital computer, said first data as corresponding to human anatomy; and
outputting, from or in accordance with instructions from the digital computer, at least one of a visual and audible notification that a non-human anatomical element is present on or proximate to the subject's body upon a determination that no match between said first data and said second data exists.
2. The method of claim 1 wherein said first data is edge sharpness and said second data is edge sharpness.
3. The method of claim 2 wherein said comparing comprises dividing the first data edge sharpness and the second data edge sharpness.
4. The method of claim 2 wherein said first location is determined by a Canny edge detector.
5. The method of claim 1 wherein said first data comprises pixel brightness and said second data comprises pixel brightness.
6. An apparatus for the security screening of a person, comprising:
a body scanner, said body scanner producing an electronic image of said person;
a digital computer, said digital computer performing digital warping, the performance of digital warping comprising:
determining an outline of the electronic image;
identifying symmetric fiducials on said outline of the electronic image, wherein a first fiducial and a corresponding second fiducial is symmetric about a bilateral center of said outline of the electronic image;
transforming the symmetric fiducials into symmetric quadrilateral pairs; and
warping the symmetric quadrilateral pairs based on coordinates of the symmetric quadrilateral pairs to generate a warped electronic image; and
said digital computer detecting bilateral asymmetric regions in said warped electronic image based on symmetrical image information generated using data derived from the electronic image, the symmetrical image information being determined based on a match existing between one or more imaging characteristics exposed by the warped electronic image and the electronic image, the bilateral asymmetric regions being determined based on one or more imaging characteristics exposed by the warped electronic image not matching that of the electronic image; and
an annunciator, said annunciator presenting a representation of at least the bilateral asymmetric regions in response to the detection of said bilateral asymmetric regions.
7. The apparatus of claim 6 wherein said electronic image represents x-ray intensity.
8. The apparatus of claim 6 wherein said digital computer is contained within said body scanner, and said digital computer implements the scanning sequence of said body scanner.
9. The apparatus of claim 6 wherein said detecting bilateral asymmetric regions comprises calculation of image edge sharpness.
10. The apparatus of claim 7 wherein said annunciator is a visual display, said visual display comprising a generic human body graphic for positional reference.
11. A method for searching a person for concealed weapons, comprising:
scanning said person with a body scanner device, said scanning producing an electronic image of said person;
transmitting said electronic image to a digital computer;
determining, by said digital computer, the bilateral centerline of said person in said electronic image;
determining, by said digital computer, an outline of the electronic image;
identifying, by said digital computer, symmetrical fiducials on said outline of the electronic image, wherein a first fiducial and a corresponding second fiducial is symmetric about a vertical axis centered along said outline of the electronic image;
transforming, by said digital computer, the symmetrical fiducial into symmetric quadrilateral pairs;
warping, by said digital computer, the symmetric quadrilateral pairs based on coordinates of the symmetric quadrilateral pairs to generate a warped electronic image;
detecting, by said digital computer, features in said electronic image that are asymmetric with respect to said bilateral centerline using said warped electronic image, said electronic image comprising symmetrical image information based on a match existing between one or more imaging characteristics of said electronic image and warped electronic image; and
issuing, by the digital computer or by one or more alarming devices operatively connected to the digital computer, an alarm that a concealed weapon is present if an asymmetric feature is detected.
12. The method of claim 11 further comprising digital warping said electronic image to maximize bilateral symmetry.
13. The method of claim 11 wherein said determining the bilateral centerline comprises identifying an outline of said person's representation in said electronic image, and identifying fiducials on said outline.
14. The method of claim 11 wherein the detected features are image edges.
15. The method of claim 11 wherein said scanning comprises: illuminating said person with x-ray radiation, detecting x-rays that are backscattered from the body of said person, and detecting x-rays that are transmitted through the body of said person.
16. The method of claim 15 wherein the detected features are image edges.