Radiation imaging system and method for detecting positional deviation

A radiation imaging system comprising:

• a first grating for passing radiation emitted from a radiation source and producing a first fringe image;
• an intensity modulator for applying intensity modulation to the first fringe image and producing a second fringe image in each of plural relative positions out of phase with one another with respect to a periodic pattern of the first fringe image;
• a radiation image detector for detecting the second fringe image;
• an image processor for producing a phase contrast image of an object disposed between the radiation source and the radiation image detector based on a plurality of the second fringe images detected by the radiation image detector;
• and
• a positional deviation detector for detecting a positional deviation between the first grating and the intensity modulator, the positional deviation detector obtaining an intensity modulation signal from the plural second fringe images on a pixel-by-pixel basis, and evaluating the positional deviation based on a characteristic value of the intensity modulation signal.