| 摘要 |
An X-ray tube with an adjustable focal spot is provided wherein the focal-spot position can be moved along the anode and the focal-spot width can be changed by applying a small voltage to the cathode-bias cup. The cathode includes means integral with the cathode for deflecting the flow of electrons to selectable focal-spot areas on the anode in response to an external drive circuit. The cathode includes a filament for emitting electrons to impinge on the anode, and a cathode cup having first and second parts electrically insulated from each other. The filament is electrically insulated from at least one of the parts of the cathode cup. The electrical insulation between the first and second parts of the cathode cup can be provided by a gap therebetween. The device includes biasing means for applying a voltage between the filament and the cathode to control the size and position of the region of impingement of the electron beam on the anode. The anode can be rotatable with respect to the cathode.
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