[en] (1) The unit, with the aid of a pickup X-ray beam and an X-ray detector, operates on local absorption differences in an object, characterized by an X-ray source that is equipped with an anode traction plate which has, at least in one direction a large width and with an electron beam deflection unit for the distribution of an electron stream over the anode plate in order to impinge an X-ray beam on the test object. (2) A unit, following claim 1, characterised by an X-ray beam from each traction position being collimated towards the same detector to permit on-line reading. (3) A unit, following claims 1 and 2, that, from several traction positions for each electron beam pick-up a number of parallel X-ray beams may be collimated. (G.C.)