Background: In hard X-ray phase imaging using interferometry, the spatial resolution is limited by the pixel size of\ndigital sensors, inhibiting its use in magnifying observation of a sample.\nMethods: To solve this problem, we describe a digital phase contrast microscope that uses Zernikeâ��s phase contrast\nmethod with a hard X-ray Gabor holography associated with numerical processing and spatial frequency domain filtering\ntechniques. The hologram is reconstructed by a collimated beam in a computer. The hologram intensity distributions\nitself become the reconstructed wavefronts. For this transformation, the Rayleigh- Sommerfeld diffraction formula is used.\nResults: The hard X-ray wavelength 0.1259 nm (an energy of 9.85 keV) was employed at the SPring-8 facility. We\nsucceeded in obtaining high-resolution images by a CCD sensor with a pixel size of 3.14 �¼m, even while bound by the\nneed to satisfy the sampling theorem and by the CCD pixel size. The test samples used here were polystyrene beads of 8\n�¼m, and human HeLa cells.\nConclusions: We thus proved that the resolution 0.951 �¼m smaller than the pixel size of CCD (3.14 �¼m) was achieved by\nthe proposed reconstruction techniques and coherent image processing in the computer, suggesting even higher\nresolutions by adopting greater numerical apertures.
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