Versatile x-ray beam scanner

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.