Patent EP0070621A2 successfully refreshed from Google Patents.
EP0070621A2
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EP
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Method and apparatus for inspecting sheets for flaws
Assignee: De la Rue Systems Ltd
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Filing: 1982-06-16
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Granted: —
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Expires: 2002-06-16
Abstract
Abstract @ Apparatus for detecting missing areas or folded corners in sheets, for example banknotes (14), is disclosed. Figure 1 shows a banknote (14) being scanned in a strip along one edge of the banknote. A strip light source (12) and a strip sensor (16) are disposed on opposite faces of the banknote which is caused to move perpendicularly to the light path between the source and sensor, and perpendicularly to the plane of the drawing. A photometer (18) responds to the total amount of light transmitted through the edge strip of the banknote (14) as the banknote is scanned. A filter (20) may be inter posed in the light path to improve the sensitivity of the apparatus. The total amount of transmitted light detected by the photometer (18) is integrated over a period of the scan during which the intensity differs substantially from the mean level for an unflawed portion of the banknote. Integration is thus performed only over missing or folded areas of the banknote. It may also be limited to only the leading and trailing portions of the edge strip of the banknote, corresponding to the corners of the note. In order to compensate for the passage of a skewed banknote passing through the apparatus, integration is inhibited over the said period whenever the intensity waveform from the photometer (18) is steeper than a predetermined gradient.
Inventors
- 👤 Barry John Curl
Bibliographic Details
Application Number
—
Jurisdiction
EP
Data Source
google_patents
Last Synchronized
2026-11-09 08:46
CPC Classifications
G; G07; G07D; G07D7/00; G07D7/181; G07D7/185; G01; G01N; G01N21/00; G01N21/84; G01N21/88; G01N21/89; G01N21/8901; G07D7/183
Claims Analysis
Total Claims: 15
Claim 1
Independent Claim
127 words
A method of determining the size of a missing or folded area of a sheet, comprising causing relative movement between the sheet and sensing station having a strip light source (12) on one side of the sheet (14) and a strip sensor (16), aligned with the strip light source, on the other side of the sheet, the relative movement being perpendicular to the direction of the strip light source and strip sensor; and characterised by the steps of detecting any difference between the sensor output (Figure 1B) and the output level of the sensor (mean level, Figure 1B) in the presence of an unflawed portion of the sheet, and integrating (h, Figure 5) the said difference with respect to time over a given period (g, Figure 5).
Claim 2
Independent Claim
127 words
A method of determining the size of a missing or folded area of a sheet, comprising causing relative movement between the sheet and sensing station having a strip light source (12) on one side of the sheet (14) and a strip sensor (16), aligned with the strip light source, on the other side of the sheet, the relative movement being perpendicular to the direction of the strip light source and strip sensor; and characterised by the steps of detecting any difference between the sensor output (Figure 1B) and the output level of the sensor (mean level, Figure 1B) in the presence of an unflawed portion of the sheet, and integrating (h, Figure 5) the said difference with respect to time over a given period (g, Figure 5).
Claim 3
Dependent Claim
47 words
A method in accordance with claim 1, wherein the given period of integration (a to c, and d to e, Figure 4) is the period during which the actual output level differs substantially from the mean level (c to d) for the unflawed remainder of the sheet.
Claim 4
Dependent Claim
31 words
A method in accordance with claim 1, wherein the given period of integration is a predetermined time corresponding to the passage of a predetermined length of sheet from the leading edge.
Claim 5
Dependent Claim
31 words
A method in accordance with claim 1, wherein the given period of integration is a predetermined time corresponding to the passage of a predetermined length of sheet preceding the trailing edge.
Claim 6
Dependent Claim
32 words
A method in accordance with claim 3, wherein the given period of integration additionally includes a predetermined time corresponding to the passage of a predetermined length of sheet preceding the trailing edge.
Claim 7
Dependent Claim
29 words
A method in accordance with claim 2, wherein the mean level is obtained by integrating the sensor output while the sheet is scanned and dividing by the scanning time.
Claim 8
Dependent Claim
70 words
A method in accordance with claim 1, wherein differences between the sensor output for a leading end of the sheet and the ouput level of the sensor in an unflawed portion of the sheet are detected by delaying (b, Figure 5) a waveform corresponding to the sensor output (a) and then effecting a retrospective comparison (d) of the value of this delayed waveform with the actual value of the waveform.
Claim 9
Dependent Claim
31 words
A method in accordance with claim 7, wherein the said output level of the sensor in an unflawed portion of the sheet is a mean level taken over the unflawed portion.
Claim 10
Dependent Claim
69 words
A method in accordance with claim 1, 7 or 8, wherein differences between the sensor output for a trailing end of the sheet and a mean output level of the sensor in an unflawed portion of the sheet are detected by holding (c, Figure 5) a sample of the mean output level for comparison with the sensor output level for the portion of the sheet preceding the trailing edge.
Claim 11
Independent Claim
34 words
A method according to any preceding claim, wherein waveform portions (a to b; e to f; Figure 5) having more than a predetermined slope are ignored, so as to compensate for a skewed sheet.
Claim 12
Dependent Claim
109 words
Apparatus for determining the size of a missing or folded area of a sheet, comprising a sensing station having a strip light source (12) and a strip sensor (16) aligned with the strip light source, means for conveying the sheet (14) between the strip light source and the strip sensor, and characterised by an electronic circuit for detecting any difference between an output (Figure lB) from the strip sensor and the output level of the sensor (mean level, Figure 1B) in the presence of an unflawed portion of the sheet, and integrating (h, Figure 5) the said difference with respect to time over a given period (g, Figure 5).
Claim 13
Dependent Claim
109 words
Apparatus for determining the size of a missing or folded area of a sheet, comprising a sensing station having a strip light source (12) and a strip sensor (16) aligned with the strip light source, means for conveying the sheet (14) between the strip light source and the strip sensor, and characterised by an electronic circuit for detecting any difference between an output (Figure lB) from the strip sensor and the output level of the sensor (mean level, Figure 1B) in the presence of an unflawed portion of the sheet, and integrating (h, Figure 5) the said difference with respect to time over a given period (g, Figure 5).
Claim 14
Dependent Claim
39 words
Apparatus in accordance with claim 11, wherein a filter (20) is placed in the light path between the strip light source and the strip sensor, in order to increase the sensitivity of detection of a missing or folded area.
Claim 15
Dependent Claim
56 words
Apparatus in accordance with claim 11 or 12, wherein the strip light source and the strip sensor respectively comprise a light source and a plurality of fibre optics having their output ends arranged to form an illuminating strip, and a sensor having a plurality of fibre optics with their input ends arranged to form sensing strips.
References Cited (Backward Citations)
No citation records indexed.
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