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US 4,752,944 AGranted
Method and apparatus for producing an X-ray image by means of a photoconductor
AssigneeU.S. Philips Corporation
InventorsNorbert Conrads, Walter Hillen, Peter J. Quadflieg, Ulrich Schiebel
Life of this patent
Estimating the term…
Abstract
A method and apparatus for producing an X-ray exposure by means of a photoconductor. Photoconductor defect locations which appear as artefacts in the X-ray image are eliminated by subtracting a compensated dark discharge image from the X-ray image.
Claims4
In a method for producing an X-ray image with an X-ray converting photoconductor which comprises the steps of:
- first uniformly electrically charging the photoconductor;
- then exposing the photoconductor to X-rays to locally discharge the photoconductor as a function of the local intensity of X-radiation;
- then scanning the surface of the photoconductor to measure the local charge density distribution on said surface and using said distribution to produce an X-ray image, the improvement comprising:
- separately producing a correction image by first uniformly electrically charging said photoconductor and then scanning the surface to measure the local charge density distribution in the absence of exposure to X-rays;
- multiplying the local values of the charge density in the correction image by a correction factor K(V) which decreases in direct proportion to the charge density at defect-free points in the X-ray exposure image, the value of said correction factor being determined by exposing said photoconductor to varying X-ray doses to produce different charge densities.
2 more elements
Apparatus for producing an X-ray image comprising:
- an X-ray responsive photoconductor having a surface;
- means for uniformly placing an electric charge on said photoconductor surface;
- scanning means for determining the local distribution of charge on said surface;
- means for exposing said surface to X-rays;
- a first memory for storing a representation of the local charge distribution on said surface after exposure to X-rays;
- a second memory for recording a charge distribution from said surface in the absence of exposure to X-rays;
- table look-up means for storing values of correction factors, K(V), which are proportional to local charge density values in the first memory;
- and
- means for multiplying the values stored in the second memory by the values of the correction factor stored in the table look-up means and subtracting the multiplied values from the values stored in the first memory means to yield an X-ray image which is corrected to compensate for local defects in the photoconductor surface.
6 more elements
Dependencies are inferred from the claim text.