System for signal processing and related method. Interferometric projection data is reconstructed into one or more images of the spatial distribution of the physical attributes of the object being imaged. The interferometric projection data is derived from the signals collected by the X-ray detector (D), which are detected by the X-ray radiation from the interferometer and the object to be imaged (OB) It was caused after interaction. The interferometer (IF) has a reference phase. The reconstructor (RECON) reconstructs the image by fitting the data to the signal model by adapting the fitting variable. Wherein the fitting variable comprises i) one or more imaging variables for the one or more images and ii) one or more imaging variables plus a dedicated phase variable for fluctuation of the reference phase including.
