Patent Number: 048903124
Section: summary

The invention relates to a piezoelectric attenuation tongue system for slit radiography equipment comprising a number of tongues placed next to each other which are each firmly mounted by one end on a carrier. From Dutch Patent Application No. 8,400,845, now U.S. Pat. No. 4,675,893 slit radiography equipment is known which is provided with controllable attenuation elements placed next to each other which each act in combination with a section of a diaphragm slit in order to influence locally the x-ray beam transmitted or to be transmitted during operation through the diaphragm slit. The U.S. Patent No. describes various embodiments of assemblies of attenuation elements, and one of the embodiments described therein consists of a number of tongues of piezoelectric material placed next to each other. The piezoelectric tongues are firmly mounted by one end on a carrier, while the other end can be moved under the influence of electrical control signals, which are fed to each piezoelectric tongue during operation, to a greater or lesser degree into the x-ray beam transmitted or to be transmitted through the diaphragm slit in order to attenuate said beam locally to a greater or lesser degree. A drawback of the known assembly of piezoelectric attenuation tongues is that during the assembly each tongue has to be separately adjusted both in relation to the distance from the adjacent tongues and in relation to the direction with respect to the x-ray beam to be influenced. In order to make such an adjustment possible, special facilities are necessary for each tongue on the carrier and/or the tongue and/or the fixing means for the mounting of the tongue on the carrier. Moreover, the adjustment is itself very time-consuming and therefore expensive. Despite accurate adjustment it is also very difficult, if not impossible, to make the gap between adjacent tongues very small. Said gap must, however, preferably be as small as possible in order to prevent, as much as possible, unattenuated x-ray radiation being transmitted through the slit between two adjacent tongues, which radiation could give rise to strips in the final radiograph. The need therefore exists for an improved attenuation tongue system to which the abovenamed drawbacks do not apply or apply to a lesser extent. The object of the invention is to meet this need. For this purpose, a piezoelectric attenuation tongue system of the type described above is characterized according to the invention in that the separate tongues each form a single whole with a base of piezoelectric material and are obtained by slitting a plate of piezoelectric material from a first edge of the edges, leaving free a strip along a second edge situated opposite the first edge, which strip forms the base.