[en] An X-ray collimator is described for use in computerized axial tomography apparatus which includes a plurality of substantially parallel X-ray absorbing laminae disposed in the plane of a wedge-shaped X-ray beam. The length and position of each lamina with respect to a divergent X-ray source is chosen to maximize the ratio of X-ray flux impinging upon a detector array to flux falling within the collimator's penumbra, outside the detector array. A single set of moveable jaws may be disposed at the collimator exit for adjustment of the beam thickness. (Auth.)