Versatile x-ray beam scanner

• US 9,052,271 B2
• Filed: 04/13/2012
• Issued: 06/09/2015
• Est. Priority Date: 10/27/2010
• Status: Expired due to Fees

• Current Assignee: American Science and Engineering Incorporated (OSI Systems Incorporated)
• Original Assignee: American Science and Engineering Incorporated (OSI Systems Incorporated)
• Inventors: Grodzins, Lee, Schubert, Jeffrey R., Al-Kofahi, Omar, Rothschild, Peter J.
• Primary Examiner(s): Midkiff, Anastasia
• Application Number:
  US13/446,548
• Publication Number:
  US 20120269319A1
• Time in Patent Office: 1,152 Days
• Field of Search: 378 10- 15, 378/57, 378/62, 378/91, 378/98.6, 378/119, 378/121, 378/140, 378145-151, 378156-160, 378/193, 378/204, 378/210, 250/505.1, 250/506.1, 250/507.1, 250/522.1, 359/641, 359232-236
• US Class Current: 1/1
• CPC Class Codes: A61B 6/06 Diaphragms
• CPC Class Codes: G01N 23/203 Measuring back scattering
• CPC Class Codes: G02B 26/10 Scanning systems
• CPC Class Codes: G02B 27/30 Collimators
• CPC Class Codes: G21K 1/02 using diaphragms, collimators
• CPC Class Codes: G21K 1/04 using variable diaphragms, shutters, choppers

Abstract

Apparatus for interrupting and/or scanning a beam of penetrating radiation, such as for purposes of inspecting contents of a container. A source, such as an x-ray tube, generates a fan beam of radiation effectively emanating from a source axis, with the width of the fan beam collimated by a width collimator, such as a clamshell collimator. An angular collimator, stationary during the course of scanning, limits the extent of the scan, and a multi-aperture unit, such as a hoop, or a nested pair of hoops, is rotated about a central axis, and structured in such a manner that the total beam fluence incident on a target is conserved for different fields of view of the beam on the target. The central axis of hoop rotation need not coincide with the source axis.

Claims

1. A scanning apparatus for scanning a beam in a single dimensional scan, the apparatus comprising:

a. a source of radiation for generating a fan beam of radiation effectively emanating from a source axis and characterized by a width;

b. an angle selector, stationary during the course of scanning, for limiting the angular extent of the scan; and

c. a multi-aperture unit rotatable about a central axis in such a manner that beam fluence incident on a target is the same per revolution for different fields of view of the beam on the target.

2. A scanning apparatus in accordance with claim 1, wherein the multi-aperture unit includes rings of apertures spaced laterally along the central axis in such a manner that relative axial motion of the multi-aperture unit, relative to the x-ray beam plane, places a ring of apertures in the beam that is collimated by a corresponding opening angle in the angle selector.

3. A scanning apparatus in accordance with claim 1, wherein the angle selector includes a slot of continuously variable opening.

4. A scanning apparatus in accordance with claim 1, wherein the central axis is substantially coincident with the source axis.

5. A scanning apparatus in accordance with claim 1, wherein the multi-aperture unit includes rectangular slots.

6. A scanning apparatus in accordance with claim 1, wherein the source axis is forward-offset relative to the central axis.

7. A scanning apparatus in accordance with claim 1, further comprising a collimator for limiting at least one of a width of the beam and an angular extent of the scan.

8. A scanning apparatus in accordance with claim 7, wherein the collimator is a width collimator.

9. A scanning apparatus in accordance with claim 8, wherein the collimator is an inner collimator.

10. A scanning apparatus in accordance with claim 8, wherein the collimator is an outer collimator.

11. A scanning apparatus in accordance with claim 1, wherein the angle selector includes a plurality of discrete slots.

12. A scanning apparatus in accordance with claim 10, wherein the angle selector includes a shutter position.

13. A scanning apparatus in accordance with claim 1, wherein the source of radiation is an x-ray tube.

14. A scanning apparatus in accordance with claim 1, wherein the source of radiation is of a type generating a fan beam exceeding 60°

in opening angle.

15. A scanning apparatus in accordance with claim 1, further comprising an enclosing conveyance for conveying the scanning apparatus past an inspection target.

16. A scanning apparatus in accordance with claim 1, wherein the scanning apparatus is coupled to a platform.

17. A scanning apparatus in accordance with claim 1, wherein the scanning apparatus is coupled to a platform in conjunction with at least one further scanning apparatus.

18. A scanning apparatus in accordance with claim 1, further comprising a filter disposed within the beam for changing the energy distribution of the beam.

19. A scanning apparatus in accordance with claim 18, wherein the filter is disposed on a filter tube adapted for selective insertion of a plurality of filters.

20. A scanning apparatus in accordance with claim 18, wherein the filter tube includes a beam shutter.

21. A scanning apparatus in accordance with claim 1, wherein the multi-aperture unit includes two nested, multi-aperture collimators.

22. A scanning apparatus in accordance with claim 1, wherein the multi-aperture unit includes an inner multi-aperture hoop characterized by a hoop axis, the inner multi-aperture hoop made of material opaque to the beam.

23. A scanning apparatus in accordance with claim 21, wherein the inner multi-aperture unit includes rings of apertures spaced laterally along the hoop axis in such a manner that relative axial motion of the inner multi-aperture unit, relative to the beam plane, places a ring of apertures in the beam that is collimated by a corresponding opening angle in the angle selector.

24. A scanning apparatus in accordance with claim 1, wherein the multi-aperture unit includes an outer multi-aperture hoop rotatable in registration with an inner multi-aperture hoop.

25. A scanning apparatus in accordance with claim 23, wherein the outer multi-aperture hoop includes a plurality of apertures configured as horizontal slots in such a manner as to define a minimum size of emitted pencil beams along a sweep direction of the beams.

26. A scanning apparatus in accordance with claim 23, wherein the inner multi-aperture hoop and the outer multi-aperture hoop are mechanically integral.

27. A scanning apparatus in accordance with claim 23, further comprising an outer variable width collimator for defining a width of the beam that enters or exits the outer multi-aperture hoop.

28. A scanning apparatus in accordance with claim 1, wherein radiation is emitted through a plurality of apertures at different angles with respect to the target, such that pencil beams of penetrating radiation sweep in alternation through the target in such a manner as to provide a stereoscopic view of an interior volume of the target.

29. A scanning apparatus in accordance with claim 1, further comprising a rotation assembly adapted to provide for rotation of the source of radiation about the source axis.

30. A scanning apparatus in accordance with claim 1, wherein the multi-aperture unit includes substantially rectangular through-holes.

31. A method for inspecting an object based on the transmission of x-rays through an object, the method comprising:

a. generating a fan beam of radiation;

b. collimating the width of the fan beam with a collimator that is stationary during the course of a scan of the object, the scan characterized by an extent;

c. limiting the extent of the scan with an angle selector; and

d. varying a field of view of the beam on the object by means of a multi-aperture unit rotatable about a central axis in such a manner that the resulting beam fluence on the target is the same per revolution for all selected scan angles.