Patent Number: 
Section: claims

1. An X-ray radiography system for differential phase contrast imaging of an object under investigation by phase stepping, comprising:an X-ray emitter for generating electron ray beams;an X-ray image detector with pixels arranged in a matrix; anda diffraction or phase grating,wherein the X-ray emitter comprises an X-ray tube,wherein the X-ray tube comprises a cathode and an anode, andwherein the X-ray tube further comprises focusing electronics,wherein the electron ray beams emitted from the cathode are influenced by the focusing electronics to produce a first set of linear-shaped electron fan beams and a second set of further refined linear-shaped electron fan beams,wherein the second set of the further refined linear-shaped electron fan beams are incident on the anode, andwherein a spacing between lines of the first set of the linear-shaped electron fan beams and the second set of the further refined linear-shaped electron fan beams is changed by actuation of the focusing electronics. 2. The X-ray radiography system as claimed in claim 1, wherein the diffraction or phase grating is arranged between the object and the X-ray image detector, and wherein an analyzer grating is associated with the diffraction or phase grating. 3. The X-ray radiography system as claimed in claim 1, further comprising a magnetic deflection device which varies points of incidence of the second set of the further refined linear-shaped electron fan beams on the anode. 4. The X-ray radiography system as claimed in claim 1, wherein the spacing between the lines of the first set of the linear-shaped electron fan beams and the second set of the further refined linear-shaped electron fan beams is dimensioned in such a way that it satisfies Lau condition, a constructive overlaying of an interference pattern at a site of an image plane. 5. The X-ray radiography system as claimed in claim 1, wherein the lines of the second set of the further refined linear-shaped electron fan beams are moved perpendicularly to a direction of the lines.