The present invention relates to tomosynthesis. In order to further facilitate and improve the generation of three-dimensional image data, an X-ray imaging system (10) for calibration- free tomosynthesis is provided. The system comprises an imaging arrangement (12) with an X-ray detector unit (14) and an X-ray unit (16) comprising a plurality of X-ray sources (18). The system also comprises an image processing unit (20), an object receiving space (22), and a moving unit (24) for providing a relative movement between the imaging arrangement and an object of interest arranged at least partially in the object receiving space. The X-ray sources are provided in a known spatial relationship； the X-ray detector unit and the X-ray unit are also provided in a known spatial detector-sources- relationship. The moving unit provides a relative movement between the object of interest and the imaging arrangement in order to provide a plurality of system-to-object positions. The X-ray unit is configured to provide X-ray radiation to the object of interest from a plurality of different directions for each system-to-object position in order to provide a plurality of subsets of views with different viewing directions. The processing unit is configured to determine positions of the object in relation to the imaging arrangement based on the subsets of views, and to calculate a three-dimensional geometric position for each view of the subsets of views, and also to calculate a three-dimensional tomosynthesis reconstruction volume from the plurality of subsets of views.
