An X-ray device and a supplementary system are provided for interferometric X-ray imaging of a patient on the X-ray device in order to generate projective absorption recordings. An emitter-detector system includes a focus-forming X-ray tube and a digital flat-panel detector having a multiplicity of pixel-generating detector elements. A computer system has a program memory. A mobile grating attachment includes a first interferometric X-ray grating, a second interferometric X-ray grating disposed at a distance from the first X-ray grating in the radiation direction, and a displacement device for displacing the second X-ray grating in the plane of the second X-ray grating in steps over at least one detector element.
