Patent Number: 
Section: claims

1. 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; anda 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. 2. A collimator according to claim 1, wherein the second plate member and the fourth plate member are movable independently of each other. 3. A collimator according to claim 1, wherein the first plate members and the second plate member are constructed as a unitized combination, and the third plate members and the fourth plate member are also constructed as a unitized combination. 4. A collimator according to claim 3, wherein the unitized combination of the first plate members and the second plate member is subunitized for each of the first plate members and the second plate member, and the unitized combination of the third plate members and the fourth plate member is subunitized for each of the third plate members and the fourth plate member. 5. An X-ray irradiator comprising:an X-ray tube; anda collimator for collimating an X-ray generated from the X-ray tube;the 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; anda 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. 6. An X-ray irradiator according to claim 5, wherein the second plate member and the fourth plate member are movable independently of each other. 7. An X-ray irradiator according to claim 5, wherein the first plate members and the second plate member are constructed as a unitized combination, and the third plate members and the fourth plate member are also constructed as a unitized combination. 8. An X-ray irradiator according to claim 7, wherein the unitized combination of the first plate members and the second plate member is subunitized for each of the first plate members and the second plate member, and the unitized combination of the third plate members and the fourth plate member is subunitized for each of the third plate members and the fourth plate member. 9. An X-ray apparatus comprising:an X-ray tube;a collimator for collimating an X-ray generated from the X-ray tube and applying the collimated X-ray to an object to be radiographed; anda detector device for detecting the X-ray which has passed through the object to be radiographed,the 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; anda 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. 10. An X-ray apparatus according to claim 9, wherein the second plate member and the fourth plate member are movable independently of each other. 11. An X-ray apparatus according to claim 9, wherein the first plate members and the second plate member are constructed as a unitized combination, and the third plate members and the fourth plate member are also constructed as a unitized combination. 12. An X-ray apparatus according to claim 11, wherein the unitized combination of the first plate members and the second plate member is subunitized for each of the first plate members and the second plate member, and the unitized combination of the third plate members and the fourth plate member is subunitized for each of the third plate members and the fourth plate member.