Automatic threat detection based on illumination by penetrating radiant energy

• US 5,179,581 A
• Filed: 06/04/1991
• Issued: 01/12/1993
• Est. Priority Date: 09/13/1989
• Status: Expired due to Term

• Current Assignee: American Science and Engineering Incorporated (OSI Systems Incorporated)
• Original Assignee: American Science and Engineering Incorporated (OSI Systems Incorporated)
• Inventors: Annis, Martin
• Primary Examiner(s): Howell, Janice A.
• Assistant Examiner(s): CHU, KIM KWOK
• Application Number:
  US07/710,046
• Time in Patent Office: 588 Days
• Field of Search: 378/56, 378/57, 378/86, 378/87, 378/88, 378/99, 378/901, 358/111, 382/16, 382/18, 382/41, 382/51, 250/442.1, 250/472.1
• US Class Current: 378/57
• CPC Class Codes: G01N 23/203 Measuring back scattering
• CPC Class Codes: G01V 5/22 Active interrogation, i.e. by irradiating objects or goods using external radiation sources, e.g. using gamma rays or cosmic rays
• CPC Class Codes: G01V 5/222 measuring scattered radiation

Abstract

Automatic threat detection in association with imaging which relies on a backscatter detector and illumination by a flying spot source of penetrating radiation. The digital backscatter image is processed to produce a histogram. The histogram is compared to a predetermined threat characteristic and an alarm is sounded if the histogram exceeds the threat characteristic. The threat characteristic is derived in an empirical fashion and automatically modified based on sensing selected parameters associated with the scanning. Operator control over the threat characteristic is also implemented. The flying spot source is also associated with a transmit detector to produce a transmit image. The transmit image is also processed against predetermined parameters for threat assessment. The predetermined parameters are also operator variable.

Claims

1. An improved imaging system comprising:

an illumination source comprising a flying spot of penetrating radiation;

conveying means for transporting an object to be inspected through an inspection field swept by said flying spot of penetrating radiation;

first radiation detecting means located to detect radiation passing through said object as the object is transported through said inspection field for developing a sequence of transmit signals representative of a sequence of transmitted radiation;

processing means responsive to said sequence of transmit signals for determining whether or not said object is suitable for manual inspection, said processing means including;

distribution means responsive to said sequence of transmit signals for determining transmit signal intensity distribution;

means for comparing said transmit signal intensity distribution to a reference characteristic at each of a plurality of signal intensities; and

alarm means for generating an alarm only if said transmit signal intensity distribution exceeds said reference characteristic for an intensity for which said characteristic is defined.

2. An improved imaging system as recited in claim 1 in which said distribution means includes means for producing a histogram.

3. An improved imaging system as recited in claim 2 in which said means for producing a histogram produces a cumulative histogram representing, for a given intensity, a number of transmit signals of intensity greater than said given intensity.

4. An improved imaging system as recited in claim 1 further comprising operator controlled means for changing said reference characteristic.

5. An improved imaging system for detecting concealed threats based on imaging by penetrating radiation comprising:

an illumination source comprising a flying spot of penetrating radiation;

conveying means for transporting an object to be inspected through an inspection field swept by said flying spot of penetrating radiation;

first radiation detecting means, located between said illumination source and said conveying means, for detecting radiation scattered by an object transported through said inspection field and for developing a sequence of scatter signals representative of a sequence of scattered radiation;

second radiation detecting means, located across said conveying means from said illumination source for detecting radiation transmitted by an object transported through said inspection field and for developing a sequence of transmit signals representative of a sequence of transmitted radiation;

processing means responsive to said sequence of scatter signals and to said sequence of transmit signals for determining whether or not said object poses a threat, said processing means including;

transmit signal processing means including distribution means responsive to said sequence of transmit signals for determining transmit signal intensity distribution;

means for comparing said transmit signal intensity distribution to a reference characteristic at each of a plurality of signal intensities to determine if said transmit signal intensity distribution exceeds said reference characteristic;

scatter signal processing means for processing said scatter signals against a scatter threat criterion; and

alarm means enabled if either said transmit signal intensity distribution exceeds said reference characteristic or said scatter processing means determines said scanned object meets said scatter threat criterion.

6. An improved imaging system for detecting concealed threats based on imaging by penetrating radiation as recited in claim 5 wherein said scatter processing means includes:

scatter distribution means responsive to said sequence of scatter signals for determining scatter signal intensity distribution;

means for comparing said scatter signal intensity distribution to a threat characteristic at each of a plurality of signal intensities; and

means for enabling said alarm means if said scatter signal intensity distribution exceeds said threat characteristic for an intensity for which said characteristic is defined.

7. An improved imaging system for detecting concealed threats based on imaging by penetrating radiation as recited in claim 6 which further includes operator controlled means to change at least one of said reference characteristic or said threat characteristic.

8. A threat detecting system as recited in any of claims 5-7 which further includes means for generating an image based on said transmit signals and a further image based on said scatter signals.

9. An improved method of imaging comprising the steps of:

illuminating an inspection field with a flying spot of penetrating radiation;

transporting an object to be inspected through said inspection field;

detecting radiation passing through said object as the object is transported through said inspection field and developing a sequence of transmit signals representative of a sequence of transmitted radiation;

determining whether or not said object is suitable for manual inspection, including the steps of;

determining transmit signal intensity distribution from said sequence of transmit signals;

comparing said transmit signal intensity distribution to a reference characteristic at each of a plurality of signal intensities; and

generating an alarm only if said transmit signal intensity distribution exceeds said reference characteristic for an intensity for which said characteristic is defined.

10. A method of identifying a concealed threat using penetrating radiant energy comprising the steps of:

(a) scanning an object with a flying spot of penetrating radiant energy;

(b1) developing scatter signals representative of radiant energy scattered by said object in response to the scanning of step (a);

(b2) developing transmit signals representative of radiant energy transmitted by said object in response to the scanning of step (a);

(c1) producing an intensity distribution of said scatter signals developed in step (b1);

(c2) producing an intensity distribution of said transmit signals developed in step (b2);

(d1) comparing said intensity distributions of step (c1) to a threat characteristic defined for plural intensities;

(d2) comparing said intensity distributions of step (c2) to a reference characteristic defined for plural intensities

(e) enabling an alarm when either (1) said comparing step (d1) indicates that said scatter intensity distribution exceeds said threat characteristic for at least one intensity for which said threat characteristic is defined, or (2) said comparing step (d2) indicates that said transmit intensity distribution exceeds said reference characteristic for at least one intensity for which said reference characteristic is defined.

11. A method as recited in claim 10 which includes the further steps of storing said threat characteristic and varying said stored threat characteristic prior to effecting said comparison of step (d1).

12. The method of any of claims 10-11 which includes the further steps of:

(f) producing transmit and scatter images from said transmit and scatter signals, respectively; and

(g) selectively flashing portions of said images when said alarm is enabled.