Hand-held contraband detector

• US 5,068,883 A
• Filed: 05/11/1990
• Issued: 11/26/1991
• Est. Priority Date: 05/11/1990
• Status: Expired due to Term

• Current Assignee: Science Applications International Corporation
• Original Assignee: Science Applications International Corporation
• Inventors: deLesdernier, David L., DeHaan, Daniel
• Primary Examiner(s): Westin, Edward P.
• Assistant Examiner(s): WONG, DON KITSUN
• Application Number:
  US07/522,274
• Time in Patent Office: 564 Days
• Field of Search: 378/88, 378/198, 378/197, 378/86, 378/87, 378/83, 250/496.1, 250/497.1, 250/498.1
• US Class Current: 378/86
• CPC Class Codes: G01N 23/203 Measuring back scattering
• CPC Class Codes: G01V 5/222 measuring scattered radiation

Abstract

A light-weight hand-held contraband detection system (10) includes two different sources (74) of low energy gamma rays. Each gamma ray source selectively emits gamma rays at a different energy level, which gamma rays are directed to a specific volume (30) of an object, e.g. a vehicle, being searched. The hand-held detection system also includes a gamma ray detector (42) coupled to a visual indicator (14), which indicator visually indicates the relative number of back-scattered gamma rays reflected back from the object being searched. Back scattering of the emitted gamma rays occurs in differing degrees depending upon the density and contents of the particular volume of the object receiving the gamma rays. Certain changes in density reflect the possibility that contraband, such as drugs, may be concealed in the object being searched. In use, the system is gripped in a hand of the user and passed over the surface of the object being searched. A mechanical latch (80, 82, 90, 92, 94) allows a user to use the system without having to continually press a thumb switch (22). The indicator (14) on the device is detachable from the housing, but remains electrically connected to the housing through an umbilical cord. One embodiment of the detection system also includes audible alarm means (54, 59) for providing an audible indication to the user of the relative number of backscattered gamma rays.

Claims

1. A portable contraband detection system for detecting contraband concealed within an object, said detection system comprising:

gamma ray generating means for generating low energy gamma rays, said gamma ray generating means being located within a shielded housing having a collimator opening, said gamma ray generating means including means for generating gamma rays having a plurality of prescribed energies;

shutter means for selectively directing said low energy gamma rays through said collimator opening or into said shielded housing, said shutter means including a shutter assembly having a closed position wherein said gamma rays are absorbed into said shielded housing, and an open position wherein said gamma rays are directed through said collimator opening, said shutter assembly comprising;

a shaft passing through said shielded housing,

a drum mounted for rotation about its longitudinal axis on said shaft,

means for receiving a plurality of radioactive sources within said drum, each of said radioactive sources having a prescribed energy, each radioactive source being contained in a housing having an open end and a closed end, said closed end being held in said drum so as to be near the longitudinal axis of said drum, said open end being near a circumferencial surface of said drum,

means for selectively rotating said drum 180°

, said open position corresponding to positioning said drum such that the open end of each of said radioactive source housings is the closest possible distance to said collimator opening, and said closed position corresponding to rotating said drum 180°

from said open position such that the open end of each of said radioactive source housings in the farthest possible distance from said collimator opening;

gamma ray detection means for detecting backscattered gamma rays from a source external to said shielded housing;

processing means for monitoring the number of backscattered gamma rays detected by said detecting means and displaying a count signal detecting means and displaying a count signal representative thereof;

means for detecting any significant change in said count signal as said low energy gamma rays are selectively directed towards adjacent prescribed volumes of said object, the number of backscattered gamma rays noticeably changing if one of said adjacent prescribed volumes contains contraband;

whereby contraband within one of said prescribed volumes may be detected by monitoring changes in said count signal.

2. The portable contraband detection system as set forth in claim 1 wherein said processing means includes alarm means for automatically determining when said count signal exceeds a prescribed threshold.

3. The portable contraband detection system as set forth in claim 2 wherein said prescribed threshold comprises a reference count obtained from holding said collimator opening adjacent a reference volume of said object.

4. The portable contraband detection system as set forth in claim 3 wherein said alarm means is for further generating an audible alarm signal in response to determining that said count signal exceeds said reference count by a prescribed amount.

5. The portable contraband detection system as set forth in claim 2 wherein said means for displaying said count signal includes a visual indicator mounted within a display head electrically coupled to said processing means, said display head being selectively adjustable to enable said displayed count signal to be more readily visible.

6. The portable contraband detection system as set forth in claim 5 wherein said display head is selectively detachable from a housing wherein said processing means, shutter means, and gamma ray generating means are located.

7. The portable contraband detection system as set forth in claim 1 wherein said plurality of radioactive sources received in said drum include a source of americium 241 and a source of barium 133.

8. The portable contraband detection system as set forth in claim 7 wherein said means for selectively rotating said drum is controlled by application of a manual force to a lever coupled to said shaft.

9. The portable contraband detection system as set forth in claim 8 wherein said shutter assembly further includes mechanical biasing means for forcing said drum to rotate to the closed position of said shutter assembly absent the application of said manual force to said lever.

10. The portable contraband detection system as set forth in claim 9 wherein said shutter assembly further includes latch means for selectively locking said drum so that said shutter assembly is locked in its open position.