Shielding an imaging array from x-ray noise

Abstract

An electronic imaging sensor, which has an improved immunity to noise caused by unwanted x-rays, images an object by collecting charge carriers produced in the sensor when the object is exposed to x-rays. One or more shielding areas are formed proximate the sensor to capture or sweep away any undesirable charge carriers generated by the unwanted x-rays. The shielding areas extend deeper beneath the surface of the sensor than the depth at which the desired charge carriers corresponding to the object being imaged is collected. The shielding areas capture charge carriers formed by the unwanted x-rays, which penetrate into the sensor to a greater depth than the depth at which the desired charge carriers are collected. In this way, the undesirable charge carriers are captured near the region where they are generated and before they migrate towards the surface where they can be collected and manifest as noise in the resulting image of the object.

1 .- 8 . (canceled) 
   
   
       9 . A radiation detector, comprising:
 a photoconductive portion that generates charge carriers when irradiated with x-rays;   a semiconductor substrate incorporating dopants of a first conductivity type;   a sensing region positioned at a first depth below a surface of the substrate to collect the charge carriers generated in the photoconductive portion;   a shielding portion formed in the substrate and incorporating dopants of a second conductivity type, wherein a shielding junction located at an interface between the shielding portion and the substrate and positioned at a second depth that is deeper below the surface of the substrate than the first depth collects charge carriers generated in the substrate by stray x-rays that pass through the photoconductive portion into the substrate.   
   
   
       10 . A radiation detector according to  claim 9 , further comprising a plurality of shielding portions arranged around the sensing region. 
   
   
       11 . A radiation detector according to  claim 9 , wherein the photoconductive portion is comprised of selenium, lead iodide or mercuric iodide. 
   
   
       12 . A radiation detector according to  claim 9 , wherein the depth of the shielding junction correlates substantially with a penetration depth of the stray x-rays in the substrate. 
   
   
       13 . A radiation detector according to  claim 9 , wherein the radiation detector is incorporated in a dental imaging device. 
   
   
       14 . A radiation detector according to  claim 9 , wherein the radiation detector is incorporated in a medical imaging device. 
   
   
       15 . (canceled) 
   
   
       16 . A radiation detector, comprising:
 photoconductor means for generating charge carriers when irradiated with x-rays;   semiconductor substrate means incorporating dopants of a first conductivity type;   sensing means for collecting the charge carriers generated by the photoconductor means, wherein the sensing means is positioned at a first depth below a surface of the substrate means;   shielding means for collecting charge carriers generated in the substrate means by stray x-rays that pass through the photoconductor means into the substrate means, wherein the shielding means incorporates dopants of a second conductivity type and is formed in the substrate means such that an interface between the shielding means and the substrate means is positioned at a second depth that is deeper below the surface of the substrate than the first depth.