Patent Number: 
Section: claims

1. A method of producing a diffraction grating with a phase imaging apparatus comprising a first diffraction grating for forming a periodic pattern from X-rays emitted from an X-ray source and a second diffraction grating for interfering with the periodic pattern of the first diffraction grating, the second diffraction grating including a plurality of unit diffraction gratings, comprising:generating a moire by interfering between a plurality of unit diffraction gratings of the second diffraction grating and the periodic pattern formed by the first diffraction gratin; andaligning at least one of the plurality of unit diffraction gratings with respect to another of the plurality of unit diffraction gratings by relatively rotating the at least one of the plurality of unit diffraction gratings with respect to the another unit diffraction grating of the plurality of unit diffraction gratings based on a status of the moire generated. 2. The method of producing a diffraction grating as recited in claim 1, whereinthe plurality of unit diffraction gratings includes a first unit diffraction grating and a second unit diffraction grating, andrelatively rotating the at least one of the plurality of unit diffraction gratings includes aligning extending directions of the first unit diffraction grating and the second unit diffraction grating by relatively rotating the first unit diffraction grating with respect to the second unit diffraction grating based on a period of a first moire generated by the first unit diffraction grating and the periodic pattern and a period of a second moire generated by the second unit diffraction grating and the periodic pattern. 3. The method of producing a diffraction grating as recited in claim 2, further comprising fixing the first unit diffraction grating with respect to a substrate of the second diffraction grating,wherein relatively rotating the first unit diffraction grating with respect to the second unit diffraction grating includes aligning extending directions of absorption portions of the first unit diffraction grating and the second unit diffraction grating by relatively rotating the second unit diffraction grating with respect to the substrate with the first unit diffraction grating fixed to the substrate; andwherein the method further comprises fixing the second unit diffraction grating with respect to the substrate with the extending directions of the absorption portions of the first unit diffraction grating and the second unit diffraction grating aligned. 4. The method of producing a diffraction grating as recited in claim 3,wherein relatively rotating the first unit diffraction grating with respect to the second unit diffraction grating comprises rotating the second unit diffraction grating in a state in which the substrate of the second diffraction grating and the first unit diffraction grating are fixed. 5. The method of producing a diffraction grating as recited in claim 3,wherein relatively rotating the first unit diffraction grating with respect to the second unit diffraction grating comprises rotating the substrate and the first unit diffraction grating together in a state in which the second unit diffraction grating is fixed. 6. The method of producing a diffraction grating as recited in claim 3, wherein the plurality of unit diffraction gratings further includes a third unit diffraction grating and the method further comprises:with the first and second unit diffraction gratings fixed to the substrate, relatively rotating the third unit diffraction grating with respect to the first unit diffraction grating and the second unit diffraction grating in a state in which the first unit diffraction grating and the second unit diffraction grating are fixed to the substrate; andfixing the third unit diffraction grating with respect to the substrate after relatively rotating the third unit diffraction grating so that the extending directions of the absorption portions of the first, second and third unit diffraction gratings are aligned with the first, second and third unit diffraction gratings fixed with respect to the substrate. 7. The method of claim 1, wherein the second diffraction grating is an absorption grating. 8. The method of claim 1, wherein the second diffraction grating is a phase grating. 9. The method of claim 2, wherein the second diffraction grating is an absorption grating. 10. The method of claim 2, wherein the second diffraction grating is a phase grating. 11. The method of claim 2, further comprising fixing the first unit diffraction grating and the second unit diffraction grating to a substrate of the second diffraction grating so that absorption portions of the first unit diffraction grating and the second unit diffraction grating extend in a first direction with respect to the substrate. 12. The method of claim 11, wherein the first unit diffraction grating and the second unit diffraction grating are adjacent to each other in the first direction on the substrate. 13. The method of claim 11, wherein the first unit diffraction grating and the second unit diffraction grating are adjacent to each other in a second direction that is perpendicular to the first direction on the substrate. 14. The method of claim 11, wherein the first unit diffraction grating and the second unit diffraction grating are neither adjacent to each other in the first direction on the substrate nor adjacent to each other in a second direction that is perpendicular to the first direction on the substrate. 15. The method of claim 2, wherein relatively rotating the first unit diffraction grating with respect to the second unit diffraction grating comprises matching the periods of the first and second moires by adjusting at least one of the periods of the first and second moires. 16. The method of claim 2, wherein relatively rotating the first unit diffraction grating with respect to the second unit diffraction grating comprises relatively rotating at least one of the first unit diffraction grating and the second unit diffraction grating with respect to the periodic pattern. 17. The method of claim 16, further comprising generating a self-image as the periodic pattern by irradiating X-rays onto the first grating. 18. The method of claim 17, further comprising arranging the first unit diffraction grating and the second unit diffraction grating on a substrate of the second diffraction grating that is spaced a predetermined distance away from the first grating.