Patent Number: 
Section: claims

1. A phase-contrast x-ray imaging device, comprising:an x-ray source for generating an x-radiation field;an x-ray detector having a one-dimensional or two-dimensional arrangement of pixels; anda phase-contrast differential amplifier disposed between said x-ray source and said x-ray detector and configured to amplify spatial phase differences in the x-radiation field during operation;said phase-contrast differential amplifier having two diffraction gratings which, when viewed in a radiation incidence direction, are arranged one behind another; and wherein each said diffraction grating includes:a transverse surface to be aligned substantially at right angles to the radiation incidence direction and being spanned by an x-axis and a y-axis perpendicular thereto; anda plurality of diffraction ridges made of an optically comparatively thin base material arranged in alternation with optically denser interspaces;said diffraction ridges being formed to subdivide the transverse surface into elongate diffraction strips that extend in each case in a y-direction and that are arranged next to one another in parallel rows in an x-direction, wherein adjacent diffraction strips are different from one another in that they are always aligned to different focuses in terms of the diffraction properties of a grating material arranged in each case in a vicinity of said diffraction strip or diffract in different directions. 2. The phase-contrast x-ray imaging device according to claim 1, wherein said phase-contrast differential amplifier is configured such that unaffected x-radiation experiences a uniform phase shift due to said phase-contrast differential amplifier irrespective of an entry position of the unaffected x-radiation at said phase-contrast differential amplifier. 3. The phase-contrast x-ray imaging device according to claim 1, wherein said two diffraction gratings of said phase-contrast differential amplifier are two identical diffraction gratings. 4. The phase-contrast x-ray imaging device according to claim 1, wherein said diffraction ridges are formed to extend diagonally at least in sections within the transverse surface, wherein lateral faces of at least one said diffraction ridge which delimit said diffraction ridge in the x-direction in each case extend across a plurality of said diffraction strips. 5. The phase-contrast x-ray imaging device according to claim 1, wherein said diffraction ridges are formed as oblique prisms inclined in the y-direction, and having a base surface and a top surface that lie in the end faces of said diffraction grating that are parallel to the transverse surface. 6. The phase-contrast x-ray imaging device according to claim 5, wherein:said diffraction ridges are arranged such that in each diffraction strip there results a material structure repeating itself with a y-period length in the y-direction; andsaid diffraction ridges are inclined in the y-direction such that a top surface of each diffraction ridge opposite the base surface is offset with respect to the base surface by a whole number of period lengths. 7. The phase-contrast x-ray imaging device according to claim 6, wherein the top surface of each diffraction ridge opposite the base surface is offset with respect to the base surface by precisely one period length. 8. The phase-contrast x-ray imaging device according to claim 1, wherein each said diffraction ridge adjoins the interspaces arranged between said diffraction ridges with two lateral faces in each case, wherein said lateral faces are composed of active subareas having a comparatively strong diffraction effect in the x-direction alternating with passive subareas having a small or neglectable diffraction effect in the x-direction. 9. The phase-contrast x-ray imaging device according to claim 8, wherein each active or passive subarea extends across a whole number of diffraction strips in the x-direction. 10. The phase-contrast x-ray imaging device according to claim 1, which comprises an object support for accommodating an examination object disposed between said x-ray source and said phase-contrast differential amplifier. 11. The phase-contrast x-ray imaging device according to claim 1, which further comprises an analysis grating arranged between said phase-contrast differential amplifier and said x-ray detector. 12. The phase-contrast x-ray imaging device according to claim 1, which further comprises a coherence grating arranged between said x-ray source and said phase-contrast differential amplifier. 13. The phase-contrast x-ray imaging device according to claim 1, which further comprises an additional diffraction grating arranged between said phase-contrast differential amplifier and said x-ray detector.