Patent Number: 
Section: claims

1. An x-ray apparatus which includes an X-ray source for producing X-rays, an X-ray detector for detecting the X-rays, a filter which is arranged between the X-ray source and the X-ray detector, which filter includes a plurality of tubular filter elements having a longitudinal direction z and a circumference, the X-ray apparatus also including an electrical device which is provided with at least one power supply source for controlling the individual filter elements, wherein each filter element is constructed with an internal volume for receiving a liquid filling having electrically conductive and X-ray absorbing properties, and wherein each filter element displays an X-ray absorptivity which is dependent on the quantity of X-ray absorbing liquid present in the internal volume,  wherein each filter element includes a first electrode for applying a first electric potential to a wall of the filter element, and a second electrode for applying a second electric potential to the internal volume of the filter element,  wherein the X-ray absorptivity of each filter element is adjustable by step-wise control of a level of the X-ray absorbing liquid in the longitudinal direction z of the filter element, and  wherein the first electrode includes a series of electrode segments which extend at least over a part of the circumference of the filter element and succeed one another in the longitudinal direction z of the filter element, and said directly successive electrode segments are electrically insulated from one another and individually controllable by the electrical device. 2. A filter for use in the X-ray apparatus as set forth in  claim 1 , wherein the electrode segments are subdivided into at least two sub-groups, each sub-group including at least two not directly successive electrode segments, the electrode segments in each sub-group being electrically interconnected. claim 1 3. The filter as set forth in  claim 2 , wherein the electrode segments bear even sequence numbers in the series and the electrode segments bear odd sequence numbers in the series constitute respective sub-groups, the electrical device being provided with switches for controlling said sub-groups. claim 2 4. A filter for use in the X-ray apparatus as set forth in  claim 1 , wherein each electrode segment is connected to the electrical device via a respective connection. claim 1 5. A filter for use in the X-ray apparatus as set forth in  claim 1 , wherein facing edges of directly successive electrode segments are provided with meshing teeth. claim 1