Covert Surveillance Using Multi-Modality Sensing

Abstract

The present specification discloses a covert mobile inspection vehicle with a backscatter X-ray scanning system that has an X-ray source and detectors for obtaining a radiographic image of an object outside the vehicle. The system is configured to also simultaneously detect passive radiation. The systems preferably include at least one sensor for determining a distance from at least one of the detectors to points on the surface of the object being scanned, a processor for processing the obtained radiographic image by using the determined distance of the object to obtain an atomic number of each material contained in the object, and one or more sensors to obtain surveillance data from a predefined area surrounding the vehicle.

We claim: 
     
         1 . A system for detecting concealed threats in an object by simultaneously performing active and passive radiation detection, the system comprising:
 an X-ray source with a modulating device to produce a pencil beam of radiation for scanning the object, said modulating device capable of blocking the pencil beam at regular intervals;   a detector module for detecting both radiation backscattered by the object when scanned with the pencil beam of radiation and passive radiation emitted from threats within said object when the pencil beam of radiation is blocked, wherein said detector module comprises at least one detector; and   a controller to measure backscattered radiation only when the x-ray pencil beam is on, and to measure only passive radiation when the x-ray pencil beam is blocked.   
     
     
         2 . The system of  claim 1  wherein the detector module comprises a detector array, wherein said detector array is capable of detecting both backscattered x-rays and passive radiation. 
     
     
         3 . The system of  claim 1  wherein the passive radiation detector is at least one of a gamma ray detector, a neutron detector, or a gamma-neutron detector. 
     
     
         4 . The system of  claim 3  wherein said neutron detector is used to passively measure neutrons simultaneously with backscatter radiation and passive gamma rays. 
     
     
         5 . The system of  claim 1  wherein the modulating device comprises a disc with at least one pinhole. 
     
     
         6 . The system of  claim 1  wherein the modulating device comprises a cylindrical chopper with at least one helical slit. 
     
     
         7 . The system of  claim 1  wherein the modulating device is rotated to produce a pencil beam that is blocked at regular intervals and wherein said system does not illuminate the object with radiation when the pencil beam is blocked. 
     
     
         8 . A system for detecting concealed threats in an object by simultaneously performing active and passive radiation detection, the system comprising:
 an X-ray source with a modulating device to produce a pencil beam of radiation for scanning the object;   a controller for switching the X-ray source on and off at regular intervals; and   a detector module comprising an X-ray detector for detecting radiation backscattered by the object when scanned with the pencil beam, and a passive radiation detector for detecting radiation emitted from threats inside said object when the pencil beam is switched off.   
     
     
         9 . The system of  claim 8  further comprising control electronics to measure backscattered radiation only when the beam is on, and to measure only passive radiation when the x-ray pencil beam is off. 
     
     
         10 . The system of  claim 8  wherein the detector module comprises a detector capable of detecting both backscattered x-rays and passive radiation. 
     
     
         11 . The system of  claim 8  wherein the passive radiation detector is at least one of a gamma ray detector, a neutron detector, or a gamma-neutron detector. 
     
     
         12 . The system of  claim 8  wherein the X-ray source is switched on and off at least once in a time period determined by a rotational frequency of the X-ray source, on the order of less than 1% of the rotational time. 
     
     
         13 . A method for detecting concealed threats in an object by simultaneously performing active and passive radiation detection, the method comprising:
 modulating an X-ray source to produce a pencil beam of radiation for scanning the object, such that the pencil beam is blocked at regular intervals; and   detecting radiation backscattered by the object when scanned with the pencil beam, and detecting passive radiation emitted from threats inside said object when the pencil beam is blocked.   
     
     
         14 . The method of  claim 13  wherein radiation is detected by using a dual-purpose detector adapted to detect both backscattered x-rays and passive radiation. 
     
     
         15 . The method of  claim 13  wherein the passive radiation is detected using a separate passive radiation detector that is at least one of a gamma ray detector, a neutron detector, or a combined gamma-neutron detector. 
     
     
         16 . The method of  claim 13  wherein said neutron detector passively measures neutrons simultaneously with backscatter radiation and passive gamma rays. 
     
     
         17 . The method of  claim 13  wherein only backscattered radiation is measured when the x-ray pencil beam is on, and only passive radiation is measured when the beam is blocked. 
     
     
         18 . The method of  claim 13  wherein the beam is modulated using a modulating device that comprises a disc with at least one pinhole. 
     
     
         19 . The method of  claim 13  wherein the beam is modulated using a modulating device that comprises a cylindrical chopper with helical slits. 
     
     
         20 . The method of  claim 13  wherein the modulating device is rotated to produce a pencil beam and is adapted to block said pencil beam at regular intervals.