Patent ID: 7206383

Claim:
A collimator comprising: a pair of first plate members having X-ray absorbability, being movable symmetrically with each other in a direction parallel to surfaces thereof, and defining an X-ray passing aperture by a spacing between respective end faces opposed to each other; a second plate member spaced from the first plate members in a direction perpendicular to the surfaces of the first plate members, having X-ray absorbability, and being movable in a direction parallel to a surface thereof and parallel to the moving direction of the first plate members; a pair of third plate members spaced from the first plate members and the second plate member in a direction perpendicular to the surfaces of the first plate members and the second plate member, having X-ray absorbability, being movable symmetrically with each other in a direction parallel to surfaces thereof and perpendicular to the moving direction of the first plate members, and defining an X-ray passing aperture by a spacing between respective end faces opposed to each other; and a fourth plate member spaced from the first plate members, the second plate member, and the third plate members in a direction perpendicular to the surfaces of the first plate members, the second plate member, and the third plate members, having X-ray absorbability, and being movable in a direction parallel to a surface thereof and parallel to the moving direction of the third plate members.