Method, x-ray tube and imaging system for adjusting the position of the x-ray tube focus

A method for adjusting a position of a focus in an x-ray tube, comprising the steps of:

• emitting an x-ray beam from an x-ray tube by emitting an electron beam from a cathode in the x-ray tube that strikes an anode in the x-ray tube at a current focus position from which the x-ray beam is emitted, said current focus position deviating from a target focus position on the anode due to an interfering magnetic field;
• gating said x-ray beam with a diaphragm comprised of diaphragm plates having diaphragm edges, to produce a gated x-ray beam;
• detecting x-rays in said gated x-ray beam with an x-ray detector;
• in an imaging computer, generating an x-ray image from the x-rays detected by said detector, said x-ray image including said diaphragm plates;
• and
• in a processor, automatically determining a deviation of said current focus position in the x-ray tube from the target focus position in the x-ray tube by determining a deviation value by evaluating respective positions of the edges of said diaphragm plates in said x-ray image;
• and
• automatically electronically correcting said current focus position by reducing the deviation of said current focus position from said target focus position dependent on said deviation value.