Patent Number: 
Section: description

FIG. 1 shows an inventive system 1 composed of a radiation pick-up device 2 and a control device 3 that controls the operation thereof. The radiation pick-up device 2 is arranged in a housing 4 (which is not shown in detail). Since the sides of the housing 4 are relatively large in area, they can be provided with stabilization elements 4a, to assist in withstanding the high forces acting on the walls of the housing 4. The device 2 has a substrate 5 at the beam entry side identified with the arrow, for example in the form of a glass carrier, on which a scintillator layer 6 is applied, for example, in the form of Csl needles. This is followed by a conductive electrode layer 7 of, for example, ITO (indium tin oxide) or SnO2. This electrode layer 7 should be as thin as possible (in the range of a few 100 xc3x85) in order to avoid stray effects. A charge layer 8, preferably of amorphous silicon, is applied on this electrode layer 7. X-ray quanta incident thereon initially penetrate through the substrate 5 and subsequently penetrate into the scintillator 6 wherein conversion into visible light occurs. This light subsequently penetrates the extremely thin electrode layer and is incident on the charge layer 8. Dependent on the intensity of the penetrating light, charges are generated in the charge layer 8. These charges are read out by an electron beam with a following read-out device. This read-out device has a cooperating cathode 9 followed by a of linear cathodes 10 which can, for example, be coated tungsten wires. These linear cathodes 10 serve as electron beam sources. Further, vertically converging electrodes 11, 12 are provided, as are vertically deflecting electrodes 13. Further, an electron beam control electrode 14 as well as a horizontally converging electrode 15 and a horizontally deflecting electrode 16 are provided. The read-out device also has an electrode 17 that accelerates the electron beam, and a retarding electrode 18. In the illustrated example, the linear cathodes 10 extend horizontally and enable the generation of an electron beam having a linear horizontal expanse. Of course, more than the four electrodes 10 that are shown can be provided, dependent on the size of the panel. The cooperating electrodes 9 serve the purpose of generating a potential gradient with the vertically converging electrodes 11 in order to prevent the generation of electron beams from cathodes 10 other than the cathode driven for the emission of the electron beam. Each vertically converging electrode 11 and 12 is plate-shaped and has a of oblong slots 19, each slot lying opposite a linear cathode 10. Each of the electron beams emitted by the cathodes 10 passes through a slot 19, causing the beam to converge vertically. The vertically deflecting electrodes 13 are allocated to the respective slots 19 and are composed of upper and lower conductor 20 between which an insulator 21 is provided. When a voltage is applied between two conductors 20 lying opposite one another in two different electrodes 13, then an electron beam that passes therethrough is deflected. The electron beam control electrode 14 is composed of a number of individual electrodes that each have an oblong slot 22. An electron beam can pass only through the slot of a correspondingly driven electron beam control electrode. An electron beam that passes through is employed for reading out the signals of a number of horizontally arranged pixels, for example ten pixels, i.e. distributions of electrical potential on the charge layer 8. After the ten pixels adjacent to this currently driven electrode are read out, then the electron beam control electrode skips ahead to the next driven electrode. The horizontally converging electrode 15 is likewise plate-shaped and has a number of individual slots 23 that are respectively positioned opposite the slots 22. This electrode 15 causes the electron beam to be contracted horizontally to form a thin ray corresponding to the size of a pixel or to a distribution of potential. The horizontally deflecting electrode 16 also has the shape of a conductive plate that is composed of individual plate segments. When a voltage is applied between two neighboring plate segments, then the electron beam can be horizontally deflected, and the allocated pixels or distributions of potential, for example ten pixels, are horizontally scanned. The acceleration electrodes 17 also are plate-shaped here and serve the purpose of accelerating the electron beam. The retarding electrode 18 has the shape of a grid conductor with numerous grid openings and serves the purpose of retarding the electron beam immediately before the charge layer 8 and of guiding the electron beam such that it strikes the charge layer at the correct angle. As shown, a high-voltage V is applied to the electrode layer 7, the amplitude thereof being controlled via the control device 3. As a result, a high-voltage is also present across the charge layer 8. This induces an avalanche effect in the charge layer 8, dependent on the amplitude of the high-voltage that is applied as well as on the number of electrons that are generated in the quanta-to-photon. By variation of the high-voltage V, the gain via the charge layer 8 can be set, so that switching can be carried out in a simple way between different operating modes that need different gains. This can ensue very quickly, particularly by using reset light 24 serving the purpose of exposing the charge layer 8. This reset light 24 can be operated, for example, in a pulsed manner by the control device 3 and causes the potential at the free surface of the charge layer 8 to be stabilized. The reset light 24 is mainly utilized for stabilizing the potential and thus for setting a desired potential when the following image exposure was previously preceded by an image exposure having low radiation dose, and thus a high gain. FIG. 2 shows the enlarged excerpt II from FIG. 1 in the form of a schematic diagram, showing the substrate 15, for example in the form of a glass plate, onto which the scintillator 6 is applied. An intermediate carrier 25 is in turn applied on the scintillator 6, for example in the form of the glass plate. An intermediate carrier 25, for example in the form of a glass film, is in turn applied thereon, the electrode layer 7, preferably being printed on the intermediate carrier 25, for in the form of the ITO electrode. The electrode layer 7 can be composed of a number of parallel, preferably vertically arranged, electrode stripes 7a (see FIG. 4). Finally, the charge layer 8 is applied onto the electrode layer 7. As shown, the high-voltage V is applied to the electrode layer 7. FIG. 3 is a schematic diagram of a second embodiment of an inventive system 26. The structure at the beam entry side (substrate, scintillator, electrode layer, charge layer) is the same as in the previously described embodiment, however, a different readout device is employed in the embodiment of FIG. 3. In this read-out device, a micro-structured electron emitter cathode 27 is provided as a flat emitter device, this being shown in the form of a schematic diagram. Any micro-structured emitter cathode that allows a targeted, punctiform emission of the electrons can be utilized, for example in the form of nano-tubes or micro-tips. Here, as well, the emitted electron beam is shaped by corresponding electrodes (not shown) and strikes the charge layer for the readout, a potential due to the high-voltage V at the electrode layer also being present across the charge layer. Although modifications and changes may be suggested by those skilled in the art, it is the intention of the inventor to embody within the patent warranted hereon all changes and modifications as reasonably and properly come within the scope of his contribution to the art.