1. A method for non-iterative focus adjustment in a computed tomography apparatus comprising at least one x-ray tube with a springing focus on an anode of the x-ray tube, said springing focus changing position on the anode in one dimension at a focus jump frequency, said x-ray tube being rotatable around a system axis, and a multi-line detector disposed opposite said x-ray tube to detect x-ray radiation therefrom, said multi-line detector comprising a plurality of detector elements each operating with a detector sampling frequency equal to said focus jump frequency, said method comprising the steps of: placing a spherical x-ray absorber in a path of x-rays emitted by said x-ray tube and acquiring at least three sinograms of said spherical absorber with said multi-line detector while said focus is alternating positions in said one dimension on said anode, with different parameters for said respective positions and with different phases between said detector sampling frequency and said focus springing frequency; and from said at least three sinograms, automatically electronically calculating a position of a center ray of said x-ray radiation emitted by said x-ray tube dependent on a movement direction of the focus, and from said position automatically electronically determining the phase between the detector sampling frequency and the focus springing frequency and adjusting said phase dependent thereon.