Patent Number: 
Section: claims

1. An X-ray phase-contrast imaging (PCI) system, comprising:an X-ray source;a detector;a first grating disposed between the X-ray source and the detector; anda second grating disposed between the first grating and the detector,wherein the first grating is a quasi-periodical phase grating such that a period of the first grating varies across the first grating and changes equally in both lateral directions. 2. The system according to claim 1, wherein the second grating is an analyzer grating. 3. The system according to claim 1, wherein the detector is flat. 4. The system according to claim 3, wherein the detector is a flat detector array. 5. The system according to claim 1, wherein the second grating is flat. 6. The system according to claim 1, wherein the first grating is curved. 7. The system according to claim 6, wherein the first grating is a cylindrical grating or a spherical grating. 8. The system according to claim 1, wherein the detector is flat,wherein the second grating is flat, andwherein the first grating is a cylindrical grating or a spherical grating. 9. The system according to claim 1, further comprising a source grating disposed between the X-ray source and the first grating. 10. The system according to claim 9, wherein the source grating is a cylindrical grating or a spherical grating. 11. The system according to claim 1, wherein the period of the first grating varies the same way in both lateral directions as an angle is varied positively or negatively by the same amount from a point on the first grating where X-rays from the X-ray source are centered during imaging. 12. A method of performing X-ray phase-contrast imaging, comprising:providing the imaging system according to claim 1;positioning an object to be imaged between the X-ray source and the first grating; andimaging the object using the system. 13. The method according to claim 12, wherein the detector is flat,wherein the second grating is flat, andwherein the first grating is a cylindrical grating or a spherical grating. 14. The method according to claim 13, wherein the second grating is an analyzer grating. 15. The method according to claim 13, wherein the imaging system further comprises a source grating disposed between the X-ray source and the first grating,wherein the source grating is a cylindrical grating or a spherical grating,and wherein the object is positioned between the source grating and the first grating for imaging of the object. 16. The system according to claim 1, wherein the first grating is disposed closer to the detector than it is to the X-ray source such that the system is configured so the first grating is disposed between the detector and an object to be imaged.