System for inspecting the contents of a container

• US 20020097836A1
• Filed: 03/20/2002
• Published: 07/25/2002
• Est. Priority Date: 12/01/1998
• Status: Active Grant

• Current Assignee: American Science and Engineering Incorporated (OSI Systems Incorporated)
• Original Assignee: American Science and Engineering Incorporated (OSI Systems Incorporated)
• Inventors: Grodzins, Lee
• Granted Patent: US 6,542,574 B2
• Time in Patent Office: Days
• US Class Current: 378/57
• CPC Class Codes: G01N 23/20 by using diffraction of the radiation by the materials, e.g. for investigating crystal structure; by using scattering of the radiation by the materials, e.g. for investigating non-crystalline materials; by using reflection of the radiation by the materials
• 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: G21K 1/025 using multiple collimators, e.g. Bucky screens; other devices for eliminating undesired or dispersed radiation
• CPC Class Codes: H01J 35/153 Spot position control
• CPC Class Codes: H01J 35/30 by deflection of the cathode ray

Abstract

An apparatus and method for generating electronically steerable beams of sequential penetrating radiation. Charged particles from a source are formed into a beam and accelerated to a target. Electromagnetic radiation generated by the target is emitted with an angular distribution which is a function of the target thickness and the energy of the particles. A beam of particles is produced by allowing the radiation to exit from an apparatus through a collimator proximal to the target. The direction of the beam is determined by the point of radiation production and the corresponding array of transmission regions of the collimator.

Claims

1. An apparatus for generating sequential beams of penetrating electromagnetic radiation comprising:

a source for producing a beam of charged particles;

a target having a surface which receives the beam of charged particles and emits electromagnetic waves in response thereto;

an electromagnetic beam director that directs the beam of charged particles to a plurality of specified locations on the target;

an electromagnetic steering device disposed proximal to the target, the electromagnetic steering device directing the charged particles to strike the target at a substantially ninety degree angle to the surface of the target; and

a collimator, the collimator having an array of transmitting regions and being disposed proximal to the target such that electromagnetic waves emitted from the target pass through the collimator and emerge from the array of transmitting regions in a series of parallel beams.

2. An apparatus according to claim 1, further including a collimator selector for positioning a specified collimator chosen from a set of collimators proximal to the target.

3. An apparatus according to claim 1, wherein the collimator includes a linear array of apertures.

4. An apparatus according to claim 1, wherein the collimator includes an areal array of apertures.

5. An apparatus according to claim 1, wherein the collimator includes a plurality of linear arrays.

6. An apparatus according to claim 1, wherein the penetrating electromagnetic radiation includes x-rays.

7. An apparatus according to claim 1, wherein the collimator includes a plurality of apertures in an absorbing matrix.

8. An apparatus according to claim 7, wherein the absorbing matrix is lead.

9. An apparatus according to claim 1, wherein the collimator includes substantially parallel transmitting rods in an absorbing matrix.

10. An apparatus according to claim 9, wherein the rods are hollow tubes.

11. An apparatus according to claim 9, wherein the absorbing matrix is mercury.

12. An apparatus according claim 1, wherein the source for producing a beam of charged particles includes an electron gun.

13. An apparatus according to claim 1, wherein the source for producing a beam of charged particles includes an ion gun.

14. An apparatus according to claim 1, wherein the source for producing a beam of charged particles is a cathode ray tube.

15. An apparatus according to claim 1, wherein the source accelerated the beam of charged particles toward the target such that the charged particles attain relativistic energy.

16. An apparatus according to claim 1, wherein the collimator can be moved in a direction normal to the target in such a manner as to change the spatial resolution.

19. An apparatus according to claim 18, further including a collimator selector for positioning a specified collimator chosen from a set of collimators proximal to the target.

20. An apparatus according to claim 18, wherein the collimator includes a plurality of apertures in an absorbing matrix.

21. An apparatus according to claim 18, wherein the collimator includes substantially parallel transmitting rods in an absorbing matrix.

22. An apparatus according to claim 21, wherein the rods are hollow tubes.

23. An apparatus according to claim 18, wherein the source accelerated the beam of charged particles toward the target such that the charged particles attain relativistic energy.

24. An apparatus according to claim 18, further comprising an electromagnetic steering device disposed proximal to the target, the electromagnetic steering device directing the charged particles to strike the target at a substantially ninety degree angle tot he surface of the target.

26. A method according to claim 25, wherein the step of directing the particles includes steering the particles by mean of an electromagnet.

27. A method according to claim 25, wherein the step of directing the particles includes steering the particles by means of a permanent magnet.

28. A method according to claim 25, further comprising:

accelerating the charged particles toward the target such that they attain relativistic energy.

29. A method according to claim 25, wherein the source for producing charged particles includes an electron gun.

30. A method according to claim 25, wherein the source for producing charged particles includes an ion beam gun.

31. A method according to claim 25, wherein the collimator includes apertures in an absorbing matrix.

32. A method according to claim 31, wherein the absorbing matrix is lead.

33. A method according to claim 25, wherein the collimator includes substantially parallel transmitting rods in an absorbing matrix.

34. A method according to claim 33, wherein the rods include hollow tubes.

35. A method according to claim 33, wherein the absorbing matrix is mercury.

36. A method according to claim 25, further comprising adjusting a distance between the target and collimator such that spatial resolution is varied.

37. A method according to claim 25, wherein the dimensions of the particle beam scan and slew rate of the particle scan are under the direct control of the operator.

17. An apparatus for providing a seamless scan of an object, the apparatus comprising:

at least two multiplexed generators of sequential beams of penetrating electromagnetic radiation, each generator comprising;

a source for producing a beam of charged particles;

a target having a surface which receives the beam of charged particles and emits electromagnetic waves in response thereto;

an electromagnetic beam director that directs the beam of charged particles to a plurality of specified locations on the target;

an electromagnetic steering device disposed proximal to the target, the electromagnetic steering device directing the charged particles to strike the target at a substantially ninety degree angle to the surface of the target; and

a collimator, the collimator having an array of transmitting regions and being disposed proximal to the target such that electromagnetic waves emitted from the target pass through the collimator and emerge from the array of transmitting regions in a series of parallel beams.

18. An apparatus for generating penetrating electromagnetic radiation of variable beam opening comprising:

a source for producing a beam of charged particles;

a target having a surface which receives the beam of charged particles and emits electromagnetic waves in response thereto;

an electromagnetic beam director that directs the beam of charged particles to the plurality of specified locations on the target; and

at least one collimator, the collimator being movable in a direction normal to the target in such a manner as to change the spatial resolution.

25. A method for generating sequential beams of penetrating electromagnetic radiation comprising:

providing a source for producing charged particles;

directing the particles to a plurality of specified locations on a target having a surface to produce radiation;

steering the charged particles such that they hit the target at a substantially ninety degree angle to the surface of the target; and

collimating the radiation.

38. In a system of the kind employing penetrating radiation for characterizing an object concealed by a concealing surface, an improvement consisting of an apparatus for generating sequential beams of penetrating radiation comprising:

a source for producing a beam of charged particles;

a target having a surface which receives the beam of charged particles and emits electromagnetic waves in response thereto;

a electromagnetic beam director that directs the beam of charged particles to a plurality of specified locations on the target;

a electromagnetic steering device disposed proximal to the target, the electromagnetic steering device directing the charged particles to strike the target at a substantially ninety degree angle to the surface of the target; and

a collimator, the collimator having an array of transmitting regions and being disposed proximal to the target such that electromagnetic waves emitted from the target pass through the collimator and emerge from the array of transmitting regions in a series of parallel beams.

39. In a system of the kind employing penetrating radiation for characterizing an object concealed by a concealing surface, an improvement consisting of an apparatus for generating penetrating radiation of variable beam opening comprising:

a source for producing a beam of charged particles;

a target having a surface which receives the beam of charged particles and emits electromagnetic waves in response thereto;

an electromagnetic beam director that directs the beam of charged particles to the plurality of specified locations on the target; and

at least one collimator being movable in a direction normal to the target in such a manner as to change the spatial resolution.

40. A method for varying the spatial resolution of an imaging system, the method comprising:

providing a source for producing charged particles and a collimator;

directing the particles to a plurality of specified locations on a target to produce penetrating electromagnetic radiation; and

adjusting a distance between the target and the collimator.

41. A system for inspecting the contents of containers comprising:

a first source for emitting sequential beams of penetrating electromagnetic radiation from a target in a first set of directions;

a conveyor for moving the container relative to the first source;

a second source of penetrating electromagnetic radiation directed in a direction substantially opposite to the first set of directions;

a first detector for detecting radiation emitted by the first source and generating a first signal;

a second detector for detecting radiation emitted by the second source and generating a second signal; and

a controller for characterizing the contents of the container based at least on the first and second signals.

42. A system according to claim 41, wherein at least one of the first and second detectors is a scatter detector.

43. A system according to claim 41, wherein at least one of the first and second detectors is a transmission detector.

44. A method of producing a continuous x-ray image, the method comprising:

generating sequential beams of penetrating electromagnetic radiation from at least two x-ray sources, the x-ray sources each comprising;

a source for producing a beam of charged particles;

a target having a surface which receives the beam of charged particles and emits electromagnetic waves in response thereto;

an electromagnetic beam director that directs the beam of charged particles to a plurality of specified locations on the target;

an electromagnetic steering device disposed proximal to the target, the electromagnetic steering device directing the charged particles to strike the target at a substantially ninety degree angle to the surface of the target; and

a collimator, the collimator having an array of transmitting regions and being disposed proximal to the target such that electromagnetic waves emitted from the target pass through the collimator and emerge from the array of transmitting regions in a series of parallel beams.