| 摘要 |
The present disclosure provides a collimator having slits of varied widths, wherein each slit includes a curved side profile having a common axis of curvature for providing a cross-section of an emitted beam of energy with a substantially uniform width when the common axis of curvature of the slit intersects a focal spot of a source of the beam. The collimator is curved about a rotation axis substantially normal to the common axis of curvature, such that rotating the collimator about the rotation axis will sequentially position the slits to collimate the emitted beam. An assembly for selecting one of the collimator slits includes a selection motor having a rotatable shaft, and a gear mechanism coupling the motor shaft to the collimator for rotating the collimator about its rotation axis to select a slit. Preferably, resilient material is seated in a circumferential groove of at least one gear of the gear mechanism for absorbing shock. Another assembly includes an alignment motor having a rotatable shaft, a cam fixed to the motor shaft for rotation therewith, and a follower rotatably and slidingly received on the motor shaft and operatively contacting the cam for linear movement of the follower along the shaft upon rotation of the cam. The collimator is operatively arranged with the follower for movement of the collimator in a direction parallel to the shaft of the motor upon movement of the follower. The assembly is useful in realigning the collimator with a shifting focal spot of a beam source.
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