Device for calibrating an x-ray system, x-ray apparatus and method for calibrating an x-ray apparatus

A device for calibrating an X-ray system with an X-ray source and an X-ray detector, the calibration device comprising a set of at least two X-ray absorptive elements (“elements”), each of the elements extending in a longitudinal and in a lateral direction, wherein the device is configured to enable adjustment of a position of each of the elements along a closed curve in a plane that extends transverse to the lateral direction and in parallel to the longitudinal direction so that the elements in each of a first and a second subset of the set of the elements are positioned with their longitudinal directions aligned in an alignment direction transverse to the curve so as to correspond to each of an aligned configuration of a number of absorptive elements, and wherein a first total length in the longitudinal direction of the elements of the first subset is different from a second total length in the longitudinal direction of the elements of the second subset, and the adjustment of the positions of the aligned configurations allows for causing each of their aligned directions to successively become coincident with a radiation beam path that extends between the X-ray source and the X-ray detector.