EP0078708A2
Expired / Lapsed
EP
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Apparatus for sorting sheets according to their patterns
Assignee: De la Rue Systems Ltd
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Filing: 1982-11-02
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Granted: —
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Expires: 2002-11-02
Abstract
Abstract Apparatus for sorting banknotes in accordance with the printed patterns on their surfaces comprises: an illumination source (S) for illuminating the banknote; scanning means (1), for example an array of photodetectors, for collecting light from a plurality of illuminated pixels of the pattern; means for moving the banknote relative to the scanning means; and an analogue-to-digital converter (6) responsive to signals from the scanning means representative of the intensity of light from each pixel, to produce intensity signals in digital form; a digital memory (7) for storing the digital signals; digital correlator means (8, 10) for correlating the stored signals with a preciously-stored set of signals representative of a set of standard patterns, the correlation being performed pixel by pixel; and sorting means, responsive to the result of the correlation to divert the banknote in accordance with the most likely match.
Inventors
- 👤 Stephen Gordon Emery
- 👤 Rick John Humble
Bibliographic Details
Application Number
—
Jurisdiction
EP
Data Source
google_patents
Last Synchronized
2026-11-02 08:57
CPC Classifications
G; G07; G07D; G07D7/00; G07D7/06; G07D7/12; G07D11/00; G07D11/50
Claims Analysis
Total Claims: 9
Claim 1
Independent Claim
182 words
Apparatus for scanning a sheet,of the kind including means (5) for illuminating the sheet, scanning means (1) for collecting light from illuminated pixels of a pattern on the sheet, and means for moving the sheet relative to the scanning means, and characterised by: an analogue-to-digital converter (6) responsive to signals from the scanning means representative of the intensity of light from each pixel, to produce intensity signals in digital form; means (9) for storing a plurality of sets of signals, each previously stored set of signals being representative of a different standard pattern; digital correlator means (4,7,8,10) for correlating the digital signals corresponding to the pattern on the sheet, pixel by pixel, with each of the stored sets of standard-pattern signals, the correlating means generating a correlation output signal for each correlation of the pattern on the sheet with a standard pattern; and sorting means, responsive to the correlation output signals, for diverting the sheet to a destination corresponding to a standard pattern only if the corresponding correlation output signal is higher than the correlation output signals for all other standard patterns.
Claim 2
Dependent Claim
182 words
Apparatus for scanning a sheet,of the kind including means (5) for illuminating the sheet, scanning means (1) for collecting light from illuminated pixels of a pattern on the sheet, and means for moving the sheet relative to the scanning means, and characterised by: an analogue-to-digital converter (6) responsive to signals from the scanning means representative of the intensity of light from each pixel, to produce intensity signals in digital form; means (9) for storing a plurality of sets of signals, each previously stored set of signals being representative of a different standard pattern; digital correlator means (4,7,8,10) for correlating the digital signals corresponding to the pattern on the sheet, pixel by pixel, with each of the stored sets of standard-pattern signals, the correlating means generating a correlation output signal for each correlation of the pattern on the sheet with a standard pattern; and sorting means, responsive to the correlation output signals, for diverting the sheet to a destination corresponding to a standard pattern only if the corresponding correlation output signal is higher than the correlation output signals for all other standard patterns.
Claim 3
Dependent Claim
53 words
Apparatus in accordance with claim 1, wherein the sorting means diverts the sheet to the destination corresponding to a standard pattern only if the difference between the correlation output signal for that pattern and the next highest value of the correlation output signals for the other patterns is greater than a predetermined threshold.
Claim 4
Dependent Claim
72 words
Apparatus in accordance with claim 1 or 2, in which a first stored standard pattern represents a pattern on one side of a sheet and a second stored standard pattern represents a pattern on the other side of the same sheet, the apparatus further including means for turning the sheet over if the correlation output signal for the second stored standard pattern is greater than that for the first stored standard pattern.
Claim 5
Dependent Claim
64 words
Apparatus in accordance with any preceding claim, wherein the digital correlator means produces a correlation output signal P, where: and in which: m is the total number of pixels of the patterns; i takes all values between 1 and m, y is the i th pixel of the standard, previosuly- stored pattern,and x is the i th pixel of the pattern on the sheet.
Claim 6
Dependent Claim
34 words
Apparatus in accordance with any one of claims 1 to 4, including means (4) responsive to a detector sensing the leading edge of a sheet for initiating the operation of the digital correlator means.
Claim 7
Dependent Claim
40 words
Apparatus in accordance with any one of claims 1 to 5, wherein the scanning means comprises a regular array of photodetectors (1) spaced in a direction perpendicular to the direction of motion of the sheet relative to the scanning means.
Claim 8
Dependent Claim
35 words
Apparatus in accordance with claim 6, including channel gain correction means (5) for applying corrections to the signals from one or more of the photodetectors to ensure a uniform response across the said regular array.
Claim 9
Dependent Claim
67 words
Apparatus in accordance with any preceding claim, wherein the analogue-to-digital converter (6) introduces a logarithmic correction, whereby the said signals from the scanning means are converted into digital signals, the level of each digital signal varying logarithmically with the corresponding level of the signal from the scanning means, such that the scale is expanded and therefore the contrast is increased for low levels of the scanning signals.
References Cited (Backward Citations)
US4288781A
Cited
EP0028089A2
Cited
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