Patent Number: 060693614
Section: summary

FIELD OF THE INVENTION The invention relates generally to the field of X-Ray sensors and in particular to increasing the resolution of digital X-Ray sensors. BACKGROUND OF THE INVENTION U.S. Pat. No. 5,391,879 to Tran et al. discloses a radiation detector which includes an array 16 of pixelized sensors 15 and an overlying array 12 of phosphor pixels 11 with a fiber optic network in between (elements 17 and 17 in FIG. 1). See Col. 1, lines 10-23. This reference discloses one layer of sensor elements rather than a pair of sensor arrays on either side of a phosphor layer. Therefore, this device suffers from loss of efficiency due to loss of a portion of the light emanating from the phosphor layer in a direction away from the pixelized sensors. U.S. Pat. No. 5,220,170 to Cox et al. discloses an X-ray imaging system and a solid state detector used therewith. FIG. 16 shows a scintilator positioned between two layers, one containing a sensor element and another containing preprocessors. See Col. 1, lines 25-30. From the foregoing discussion, it should be apparent that the prior art devices suffer from a loss in resolution because the spaces between adjacent pixels are not active as detectors. The present invention is directed to overcoming one or more of the problems set forth. SUMMARY OF THE INVENTION A solid-state X-ray detector for use in a digital X-Ray imaging system wherein a detector employs a phosphorescent layer to convert x-radiation to visible light and have the visible light detected by an image sensing device. The preferred embodiment employs silicon charge coupled devices (CCDs) "sandwiched" face-to-face with a phosphor screen or phosphor layer between them to enhance overall sensitivity of the device to X-rays. X-rays normally would pass through a CCD device and not be efficiently detected. X-rays striking the phosphor layer in this detector will generate visible light which will then be efficiently detected by the surrounding CCDs (FIG. 1). In a related embodiment, the two CCDs are offset relative to one another so that the pixels of one cover the spaces between the pixels of the other, thereby increasing the resolution of the device. In a multiple sensor array embodiment, the sensor arrays can be placed next to, and offset from, each other to further increase the resolution, or allow additional predetermined bandwidths to be captured, or both. In a further related embodiment, the phosphorescent screen is combined with an opaque mask containing holes corresponding to the positions of the pixels in the CCDs. This improves image quality by preventing light resulting from an X-ray striking the screen in a particular location from "bleeding" and exposing adjacent pixels. One screen is placed on each side of the phosphorescent layer with holes aligned with the corresponding CCD. Or, alternatively, the screen is affixed directly to the CCD prior to assembly of the device, or "spots" of phosphor material are applied directly to the CCDs over each pixel to substitute for the screen. Briefly summarized, one aspect of this invention will provide the means of capturing high-resolution X-Ray images onto sensors including a solid state X-ray detector comprising: a plurality of pixellated array sensors each sensitive to a bandwidth selected for that sensor; a phosphorescent layer applied to at least one of the sensors and aligned with the pixels of that sensor, the phosphorescent layer being sensitive to X-rays and emitting light in response to X-rays within the bandwidth of the sensor to which it is applied. These and other aspects, objects, features, and advantages of the present invention will be more clearly understood and appreciated from a review of the following detailed description of the preferred embodiments and appended claims, and by reference to the accompanying drawings. Advantageous Effect Of The Invention The present invention offers the following advantages: 1) enhanced efficiency of X-Ray detection by summing the response of multiple layers of pixels surrounding a phosphor layer; 2) increased resolution resulting from multiple sensor arrays positioned to overlap spaces between pixels; 3) the possibility of generating images from multiple X-Ray bandwidths simultaneously.