The present invention relates to differential phase-contrast imaging of an object. For increasing spatial resolution of an X-ray imaging system (2) the size of a detector pixel element (8) may be considered a limiting factor. Accordingly, it may be beneficial to increase the resolution of an apparatus (38) for phase-contrast imaging without further reducing the area of an individual pixel element (8). Accordingly, an apparatus (38) for phase-contrast imaging with improved sampling is provided, comprising an X-ray source (4), a first grating element G1 (24), a second grating element G2 (26) and an X-ray detector element (6) comprising a plurality of detector pixel elements (8), each detector pixel element (8) having a pixel area A. An object to be imagined (14) is arrangeable between the X-ray source (4) and the X-ray detector element (6). The first grating element G1 (24) as well as the second grating element G2 (26) are arrangeable between the X-ray source (4) and the X-ray detector element (6). The X-ray source (4), the first grating element G1 (24), the second grating element G2 (26) and the X-ray detector (6) are operatively coupled for acquisition of a phase-contrast image of the object (14). At least one of the first grating element G1 (24) and the second grating element G2 (26) comprise a first area A1 having a first grating pitch p1 and a second area A2 having a second grating pitch p2 different from the first grating pitch.
