Versatile x-ray beam scanner
View Patent ↗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 beam flux 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.
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 extent of the scan; and
c. a multi-aperture unit rotatable about a central axis in such a manner that beam flux incident on a target is the same per revolution for different fields of view of the beam on the target,
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, and
wherein the inner multi-aperture hoop includes rings of apertures spaced laterally along the hoop axis in such a manner that axial motion of the multi-aperture hoop places a ring of apertures in the beam that is collimated by a corresponding opening angle in the angle selector.
2. A scanning apparatus in accordance with claim 1 , further comprising a width collimator for collimating the width of the fan beam.
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 source axis is forward-offset relative to the central axis.
6. 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 extent of the scan:
c. a multi-aperture unit rotatable about a central axis in such a manner that beam flux incident on a target is the same per revolution for different fields of view of the beam on the target; and,
d. a width collimator for collimating the width of the fan beam,
wherein the width collimator includes a variable slot collimator, fixed during the course of scanning the beam, adapted to change the sweep angle of the beam, up to a specified maximum angle, and to change a central direction of the sweep.
7. A scanning apparatus in accordance with claim 1 , wherein the source of radiation is an x-ray tube.
8. 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.
9. A scanning apparatus in accordance with claim 1 , further comprising an enclosing conveyance for conveying the scanning apparatus past an inspection target.
10. A scanning apparatus in accordance with claim 1 , wherein the scanning apparatus is coupled to a platform.
11. 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.
12. A scanning apparatus in accordance with claim 1 , further comprising a filter disposed within the beam for changing the energy distribution of the beam.
13. A scanning apparatus in accordance with claim 1 , wherein the multi-aperture unit includes two nested, multi-aperture collimators.
14. 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.
15. A scanning apparatus in accordance with claim 1 , wherein the inner multi-aperture hoop includes rings of apertures spaced laterally along a hoop axis in such a manner that axial motion of the multi-aperture hoop places a ring of apertures in the beam that is collimated by a corresponding opening angle in a slot collimator.
16. A scanning apparatus in accordance with claim 1 , wherein the multi-aperture unit includes an outer multi-aperture hoop rotatable in registration with the inner multi-aperture hoop.
17. A scanning apparatus in accordance with claim 16 , wherein the outer multi-aperture hoop includes a plurality of apertures configured as horizontal slots in such a manner as to define a minimum vertical size of emitted pencil beams.
18. A scanning apparatus in accordance with claim 16 , wherein the inner multi-aperture hoop and the outer multi-aperture hoop are mechanically integral.
19. A scanning apparatus in accordance with claim 16 , further comprising a variable width collimator for defining a width of the beam that enters the outer multi-aperture hoop.
20. 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.
21. 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.
22. A scanning apparatus in accordance with claim 1 , wherein the multi-aperture unit includes substantially rectangular through-holes.