| 摘要 |
PURPOSE: To provide an X-ray collimator for generating a fan beam with a uniform thickness whose angle is precisely controlled. CONSTITUTION: An X-ray collimator is formed of a series of longitudinal slots 41 having various widths and a rotatable mandrel 39 held by a high precision bearing 42. The beam width after collimation is controlled by rotating the mandrel 39 so that a right slot 41 is aligned with an X-ray beam 19 before collimation. The beam angle is corrected by rotating the mandrel 39 by a small angle so as to offset the outlet opening part of the slot 41. The inlet opening part 43 of each slot is set larger than the outlet opening part 45 so that the width of an X-ray fan beam 22 is never influenced by the regulation of the central line. An extremely small brake 80 of backlash holds the mandrel so as to prevent the perturbation torque when the collimator is in a right position. |
