System for detecting photocopied or laser-printed documents
First Claim
1. A system for determining whether a document has been created by photocopying or laser printing, the system comprising:
- a detector that detects microdots of toner or other substances employed in photocopying and laser printing on the surface of a document; and
an output device that, in response to detection by the detector of microdots of toner or other substances employed in photocopying and laser printing on the surface of a document, outputs an indication that the document has been created by photocopying or laser printing.
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Abstract
A system for distinguishing photocopied or laser-printed documents from original documents produced by offset printing, handwriting, or typewriting. The system scans a document at low-resolution and at high-resolution to produce a low-resolution and a high-resolution matrix representation of the presence or absence of ink or toner at discrete locations on the surface of the document. Printed regions detected by the system at low-resolution are used to mask regions of the high-resolution matrix representation from the analysis. The remaining unmasked regions of the high-resolution matrix representation are analyzed by the system to detect discrete microdots uniformly distributed within those regions. The presence of microdots on the surface of the document indicates that the document was produced as a photocopied or a laser-printed duplicate.
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Citations
25 Claims
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1. A system for determining whether a document has been created by photocopying or laser printing, the system comprising:
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a detector that detects microdots of toner or other substances employed in photocopying and laser printing on the surface of a document; and
an output device that, in response to detection by the detector of microdots of toner or other substances employed in photocopying and laser printing on the surface of a document, outputs an indication that the document has been created by photocopying or laser printing. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8)
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9. A system for determining whether a document on which one or more images have been created has been printed by photocopying or laser printing, the system comprising:
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a scanning device that scans a portion the document at low resolution to produce a low-resolution scan and that scans the blank areas of the document at high resolution to produce a high-resolution scan; and
a computing device that analyzes the low-resolution scan to identify blank areas of the document on which the one or more of the images have not been created and that analyzes the high-resolution scan to detect microdots of toner or other substances employed in photocopying and laser printing. - View Dependent Claims (10, 11, 12, 13, 15, 16, 17, 18, 19)
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14. A system for determining whether a document was produced by photocopying or laser-printing, the system comprising:
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a scanning device that scans an area of the document for the presence of substances, such as ink and toner, that differ in reflectivity from a background reflectivity of the document at a resolution sufficient to detect microdots characteristic of photocopied or laser-printed documents;
a computing device that analyzes an area of the scanned area to count the number of microdots within the analyzed area, that computes a value based on the number of microdots counted, and that compares the computed value to a threshold value; and
an output to which the computing device outputs an indication that the document was produced by photocopying or laser-printing when the computed value exceeds the threshold value and to which the computing device outputs an indication that the document was not produced by photocopying or laser-printing when the computed value is equal to or less than the threshold value.
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20. A system for detecting small discreet microdots of ink, toner, and other substances employed in photocopying and laser printing on the surface of a document, the system comprising:
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a scanning device that scans a portion the document at low resolution to produce a low-resolution matrix, each cell of the low-resolution matrix corresponding to a discrete low-resolution region on the surface of the document and having a value that indicates whether a photocopying or laser printing substance was detected on that region of the document, the discrete low-resolution region on the surface sufficiently large, and the threshold for substance detection sufficiently high, that a presence of a number of microdots within a discrete low-resolution region otherwise free of photocopying or laser printing substances is not detected, the scanning device also scanning the portion the document at high resolution to produce a high-resolution matrix, each cell of the high-resolution matrix corresponding to a discrete high-resolution region on the surface of the document smaller than a discrete low-resolution region corresponding to a low-resolution matrix cell and having a value that indicates whether a photocopying or laser printing substance was detected on the high-resolution region of the document, a high-resolution region sufficiently small, and the threshold for substance detection sufficiently low, that a presence of a number of microdots within a discrete high-resolution region otherwise free of photocopying or laser printing substances is detected; and
a computing device that compares the low-resolution matrix to the high-resolution matrix in order to detect indications of microdots. - View Dependent Claims (21, 22, 23, 24, 25)
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Specification