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US5341409A
Expired / Lapsed
US
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Method of generating X-ray images and device suitable for carrying out the method
Assignee: US Philips Corp
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Filing: 1993-02-22
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Granted: 1994-08-23
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Expires: 2013-02-22
Abstract
Abstract The invention relates to a method of generating X-ray images by means of a photoconductor which is provided on a conductive substrate and whose surface potential can be read by means of probes, and also relates to a device suitable for carrying out the method. In order to avoid image artefacts which could be caused by deviating sensitivities of the probes or by frequency-dependent distortions, after the charging of the photoconductor the substrate potential is varied during a test phase. Test data is generated which correspond to the spatial or temporal variation of the potential on the surface of the photoconductor; from this test data there is formed correction data which is stored in order to correct the image data of a subsequent X-ray exposure.
Inventors
- 👤 Norbert Conrads
- 👤 Walter Hillen
- 👤 Hanns-Ingo Maack
- 👤 Stephan Rupp
- 👤 Ingo Schafer
- 👤 Ulrich Schiebel
Bibliographic Details
Application Number
—
Jurisdiction
US
Data Source
google_patents
Last Synchronized
2026-11-09 01:06
CPC Classifications
G; G01; G01T; G01T1/00; G01T1/16; G01T1/26
Claims Analysis
Total Claims: 9
Claim 1
Independent Claim
150 words
A method of generating X-ray images by means of a photoconductor (1) which is provided on a conductive substrate (2) and whose surface potential can be read by means of probes (7), comprising: a) charging the photoconductor to a defined potential; b) varying the substrate potential and reading a potential variation (U) thus caused on the photoconductor surface; c) generating test data (T(x)) which corresponds to the spatial and/or temporal variation of the potential on the surface of the photoconductor; d) determining correction data (a, b, k(x)) which compensates for a deviation of the test data from its ideal value; e) storing the correction data; f) exposing said photoconductor to X-ray radiation; g) reading by means of said probes, as image data (B(x,y)), the surface potential for pixels on the surface of the photoconductor; and h) correcting the image data (B(x,y)) read by taking into account the stored correction data.
Claim 2
Independent Claim
150 words
A method of generating X-ray images by means of a photoconductor (1) which is provided on a conductive substrate (2) and whose surface potential can be read by means of probes (7), comprising: a) charging the photoconductor to a defined potential; b) varying the substrate potential and reading a potential variation (U) thus caused on the photoconductor surface; c) generating test data (T(x)) which corresponds to the spatial and/or temporal variation of the potential on the surface of the photoconductor; d) determining correction data (a, b, k(x)) which compensates for a deviation of the test data from its ideal value; e) storing the correction data; f) exposing said photoconductor to X-ray radiation; g) reading by means of said probes, as image data (B(x,y)), the surface potential for pixels on the surface of the photoconductor; and h) correcting the image data (B(x,y)) read by taking into account the stored correction data.
Claim 3
Dependent Claim
120 words
A method as claimed in claim 1, wherein: a) said varying the substrate potential is by a constant amount; b) said determining correction data comprises determining associated correction factors (k(x)) for pixels on at least a portion of the photoconductor surface in dependance on a quotient (T r /T(x)) of a reference value (T r ) being the same for all pixels and the test data (T(x)); and c) said correcting comprises applying associated correction factors (k(x)) derived from the determined correction factors to the image data (B(x,y)) read after an X-ray exposure so that there is obtained corrected image data (B c (x,y)) which is proportional to the image data (B(x,y)) and inversely proportional to the test data (T(x)).
Claim 4
Dependent Claim
50 words
A method as claimed in claim 2, wherein for each probe (7) correction factors k(x)) are determined for at least one line of an X-ray image and stored as said correction data, the image data (B(x,b)) of all lines being subjected to correction factors derived from the stored correction data.
Claim 5
Dependent Claim
51 words
A method as claimed in claim 3, characterized in that for each probe the correction factors (k 1 (x); k 2 (x)) are formed for two non-adjacent lines, the correction factors for the other lines of this probe being derived by interpolation from the correction factors (k(x)) of the two lines.
Claim 6
Dependent Claim
91 words
A method as claimed in claim 1, characterized in that after the charging the substrate potential is varied in a step-like manner by a constant amount filter coefficients (a, b) for a digital filtering operation being determined from the magnitude and the variation of the test data (T(x)) thus successively determined in time, the filter coefficients (a, b) being stored and, during a subsequent X-ray exposure, the image data (B(x,y)) of all lines read by the same probe being subjected to a filtering operation taking into account the stored filter coefficients.
Claim 7
Independent Claim
124 words
A device for generating X-ray images, comprising a photoconductor provided on a conductive substrate, a probe device for reading, as image data, a surface potential of the photoconductor, a charging device for charging the surface of the photoconductor, an image processing unit for reconstructing an X-ray image from the image data supplied by the probe device, means for varying a substrate potential by a constant amount so that test data is supplied by said probe device, means for generating correction factors from the supplied test data, a memory for storing correction factors derived from the test data, and an image processing unit for applying corrections derived from the stored correction factors to the image data of an X-ray image in order to reduce artifacts.
Claim 8
Independent Claim
124 words
A device for generating X-ray images, comprising a photoconductor provided on a conductive substrate, a probe device for reading, as image data, a surface potential of the photoconductor, a charging device for charging the surface of the photoconductor, an image processing unit for reconstructing an X-ray image from the image data supplied by the probe device, means for varying a substrate potential by a constant amount so that test data is supplied by said probe device, means for generating correction factors from the supplied test data, a memory for storing correction factors derived from the test data, and an image processing unit for applying corrections derived from the stored correction factors to the image data of an X-ray image in order to reduce artifacts.
Claim 9
Dependent Claim
52 words
A device as claimed in claim 6, characterized in that for each probe the memory stores correction factors for at least one line, of an X-ray image, there being provided means for deriving correction factors for pixels in other lines from the stored correction factors for pixels on the same surface line.
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USPTO Annuity & Maintenance Windows
| Annuity Stage | Window Opens | Payment Deadline | Surcharge Period Until | Estimated Fee | Status |
|---|---|---|---|---|---|
| 3.5 Years (Year 4) | 1997-08-22 | 1998-02-21 | 1998-08-23 | $2000.00 | Window Closed / Lapsed |
| 7.5 Years (Year 8) | 2001-08-22 | 2002-02-21 | 2002-08-23 | $3760.00 | Window Closed / Lapsed |
| 11.5 Years (Year 12) | 2005-08-22 | 2006-02-21 | 2006-08-23 | $7700.00 | Window Closed / Lapsed |