| 摘要 |
A collimator for an X-ray examination apparatus has a plurality of diaphragm plates adjustable relative to each other in pairs for defining a cone of radiation having a variable rectangular cross-section, and has a plurality of additional diaphragm plates mounted for pivotal movement into the four corner regions of the radiation cone for defining an approximately circular radiation cone of variable diameter. Each additional diaphragm plate has a substantially triangular plan shape and are movable by respective parallelogram linkages with one edge facing the radiation cone, the edge facing the radiation cone being alignable perpendicularly to the angle bisector of the respective corner in which the additional diaphragm plate is located. The additional diaphragms are respectively pivotable substantially radially in the direction of the axis of symmetry of the collimator.
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