1. An imaging apparatus for imaging an object, the imaging apparatus comprising: a projection data providing unit for providing energy projection data values, the energy projection data values being energy-dependent and corresponding to rays, which have been emitted by a radiation source and which have traversed the object and a beam shaper placed between the radiation source and the object, a reconstruction unit for reconstructing an image of the object based on the provided energy projection data values, wherein the reconstruction unit is adapted to: determine component projection data values, corresponding to the rays after having traversed the object and to a component of the object, by combining weighted base functions based on the provided energy projection data values and a component projection data value corresponding to a ray modeled as a combination of weighted base functions, wherein said weighted base function depends on a product of a first intermediate base function and a second intermediate based function, wherein said first intermediate base function depends on the energy projection data values and said second intermediate base function depends on the length of the respective ray within the beam shaper, reconstruct an image of the object based on the determined component projection data values.