CA1132262A - Method and apparatus for evaluating notes - Google Patents
Method and apparatus for evaluating notesInfo
- Publication number
- CA1132262A CA1132262A CA338,500A CA338500A CA1132262A CA 1132262 A CA1132262 A CA 1132262A CA 338500 A CA338500 A CA 338500A CA 1132262 A CA1132262 A CA 1132262A
- Authority
- CA
- Canada
- Prior art keywords
- note
- rays
- notes
- evaluation
- counting
- Prior art date
- Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
- Expired
Links
Classifications
-
- G—PHYSICS
- G01—MEASURING; TESTING
- G01N—INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES
- G01N23/00—Investigating or analysing materials by the use of wave or particle radiation, e.g. X-rays or neutrons, not covered by groups G01N3/00 – G01N17/00, G01N21/00 or G01N22/00
- G01N23/22—Investigating or analysing materials by the use of wave or particle radiation, e.g. X-rays or neutrons, not covered by groups G01N3/00 – G01N17/00, G01N21/00 or G01N22/00 by measuring secondary emission from the material
- G01N23/223—Investigating or analysing materials by the use of wave or particle radiation, e.g. X-rays or neutrons, not covered by groups G01N3/00 – G01N17/00, G01N21/00 or G01N22/00 by measuring secondary emission from the material by irradiating the sample with X-rays or gamma-rays and by measuring X-ray fluorescence
-
- G—PHYSICS
- G01—MEASURING; TESTING
- G01N—INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES
- G01N2223/00—Investigating materials by wave or particle radiation
- G01N2223/07—Investigating materials by wave or particle radiation secondary emission
- G01N2223/076—X-ray fluorescence
Abstract
ABSTRACT OF THE DISCLOSURE
A marker element such as barium in the form of barium sulphate is incorporated in place of part of the filler in intaglio ink used in bank notes. To determine whether a bank note is valid, either in a note sorter or in a separate unit, part of the note is illuminated with X-rays and the resultant fluorescent X-rays are detected and counted.
Different note denominations can have different combinations of markers to produce different fluorescent X-ray energies, which can be detected and analyzed to control sorting of the notes into the respective denominations in a mechanical note sorter operating at high speed. This arrangement permits detection of worn notes and notes which are stuck together, as well as detecting counterfeit notes.
A marker element such as barium in the form of barium sulphate is incorporated in place of part of the filler in intaglio ink used in bank notes. To determine whether a bank note is valid, either in a note sorter or in a separate unit, part of the note is illuminated with X-rays and the resultant fluorescent X-rays are detected and counted.
Different note denominations can have different combinations of markers to produce different fluorescent X-ray energies, which can be detected and analyzed to control sorting of the notes into the respective denominations in a mechanical note sorter operating at high speed. This arrangement permits detection of worn notes and notes which are stuck together, as well as detecting counterfeit notes.
Description
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This invention reIates to t~e evaluation of notes, which term is used herein to e~hrace bank notes, bonds, and other security documents. The evaluation may be in respect of a note's validity and/or denomination.
Various methods and apparatus are known for identifying paper money and for determining the validity thereof. For example, U.S. Patent 2,950,799 to Timms describes apparatus for identifying paper money using ultra-violet light to measure the re-radiation and colour of a note, and U.S.
Patent 2,731,621 to Sontheimer describes a counterfeit detector using an optical scanner to produce electrical signals in accordance with the reflectivity of scanned portions of a document. Other methods using magnetic, acoustic, and mechanical means to evaluate notes are known for example from U.S. Patents 3,245,534, 3,208,974, 3,462,225 and 3,713,291.
These known methods and apparatus all suffer from various disadvantages. In particular, in machine sorting of bank notes it is desirable to be able automatically to recognize single note denominations, detect counterfei* notes, detect notes which through use should not be put back into circulation, and detect notes which are stuck together ("doubles"). Furthermore, these functions should desirably be achieved at a high sorting speed of for example 1200 notes per minute. All these features canno~ be achieved using known methods in a single apparatus in machine sorting of notes.
An object of this invention, therefore, is to provide a new and improved method of and apparatus for evaluating notes.
According to one aspect of this invention there is provided a methQd of evaluating a note, comprising the steps of illuminating at least a part of the note with X-rays, detecting X-rays fluorescing from the note, and counting the detected X-raysO The evaluation may be to determine the validity of the note, and/or it may be to determine the denomination of the note, in which case the counting step comprises establishing respec-tive counts for each of a plurality of different energy ranges ofdetected X-rays.
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iL~L3;~i2 According to another aspect of the invention there is provided apparatus for evaluating a note, comprising means for receiving a note to be evaluated, an X-ray source arranged to illuminate at least a part of a note received in the receiv-ing means with X-rays, means for detecting X-rays fluorescing from a note received in the receiving means, means for counting the detected X-rays, and means responsive to the counting means for providing an evaluation signal for the note. For determin-ing note validity the means fo:r providing an evaluation signal may comprise means for displaying a count established by the counting means during a predetermined period. For determining note denomination the counting means may comprise a respective counter for counting detected X-rays in each of a plurality of different energy ranges.
Conveniently the means for providing an evaluation signal comprises means for producing a control signal for determining a destination of the note, and the apparatus includes means for supplying the note from the receiving means to said destination.
In accordance with a further aspect this invention provides a method of machine sorting notes, comprising the steps of supplying notes to an evaluation zone, illuminating at least a part of each note in the evaluation zone with X-rays, detecting X-rays fluorescing from each note in the evaluation zone, counting the detected X-rays to evaluate each note, and supplying each note from the evaluation zone to a destination which is dependent upon the evaluation o the note.
According to yet another aspect this invention provides apparatus for sorting notes, comprising means for supplying notes to be sorted consecutively to an evaluation zone, an X-ray source arranged to illuminate at least a part of a note in the evaluation zone with X-rays, means for detecting X-rays fluorescing from a note in the evaluation zone, means for counting the detected X-rays to provide an evaluation signal for the note in the evaluation zone, and means respon-sive to the evaluation signal for supplying each note from the evaluation zone to a destination which is dependent upon the evaluation signal of the note~
.
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The invention is based on the recognition that X-ray fluorescence may be conveniently used ~o provide an accurate and thorough evaluation of notes, such as bank notes, at high speed. Such notes are printed with intaglio ink into which can be incorporated marker elements which when illuminated with X-rays produce characteristic fluorescent X rays at specific energies. The numbers and energies o such fluorescent X-rays are detected and quantitativeIy measured. For example, three such markers can be used seIectively and 2ither individually or in different combinations to provide each of seven different note denominations with a respective marker identification.
On illuminating such a marked note with X-rays, the fluorescent X-rays in each of three different energ~ ranges corresponding to the three markers can be detected and counted to ascertain the denomination of the note. This can be achieved at high speed in a mechanical note-sorter. If the count(s) do not reach specific lower limits, this indicates a low level of the marker(s) corresponding to a note which is counterfeit or worn so that it should not be put back into circulation. If the count(s) exceed specific upper limits, this indicates a high level of the marker(s) corresponding to two notes which are stuck together. Such notes can then be separated from the remaining notes for individual assessment.
The markers conveniently comprise heavier elements of the periodic table from strontium to bismuth. For example, such a marker can be barium in the form of barium sulphate, or tin in the form of tin oxide, or lead as lead sulphate which is incorporated into the intaglio ink used in printing the notes in place of part of the filler which is a conventional con-stituent of intaglio inks. The marker(s) may constitute, forexample, 30~ of the intaglio ink, and is preferably in excess of 10%, more preferably 20%, so that it can readily be detected.
Naturally ~ther markers, compatible with the other constituents and the requirements of the intaglio ink, may be used, and different numbers and combinations of markers may be provided as desired. For example, more than three different markers could be used to provide identification of a greater number of note denominations, or only a single marker could "
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be used to distinguish genuine Erom counterfeit notes without distinguishing between different note denominations. For certain denominations, existing notes already contain small but detectable amounts of a suitable element in the intaglio ink and the presence or absence of this element can be used as a test for the validity of the notes of these denominations.
Such markers, introdl~ced into the intaglio ink as stable insoluble compounds, have distinct advantages compared with ultraviolet-excLted f~oro~?hors previously used in notes, in particular in t~at they are much more permanent and less costl~. rnstead of being introduced into the intaglio ink, the markers could alternatïvely be incorporated into the paper of the notes.
According to yet another aspect of this invention there is provided a note, such as a bank note, comprising at least one stable and insoluble compound of an element in the periodic table from strontium to bismuth. The compound is preferably incorporated into intaglio ink with which the note is printed.
The invention will be further understood from the following description by way of example of embodiments thereof with reference to the accompanying drawings, in which:
~Fig. 1 schematically illustrates parts of apparatus for sorting bank notes embodying the present invention;
Fig. 2 schematically illustrates in cross-section a compact arrangement of an X-ray source and detector; and Fig. 3 schematically illustrates a block diagram of detection and counting circuitry which may be employed in the apparatus of Eig. 1.
* Referring to Fig. 1, which illustrates parts of a Crosfield 9300 type mechanical bank note sorter together with apparatus provided in accordance with an embodiment of the invention, bank notes 1, 2,each of any one of, for example, seven different denominati,ons are fed by means of spools 3,4 along a path indicated by arrows 5. The notes are thus fed consecutively through an evaluation zone, in which the note 2 *Trade Mark :
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is located as illustrated in Fig. 1, wh:ich is backed -by a backing plate 6. The presence of a note in the evaluation zone is detected by means of two optical sensors 7, each of which for example comprises a light source and an optical detector.
An X-ray source 8 surrounded by a collimator shield assembly 9 emits X-rays along a path indicated by broken lines 10 to illuminate at least a part of the bank note -4a-~ ' ' ' ,' .: ~ .
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This invention reIates to t~e evaluation of notes, which term is used herein to e~hrace bank notes, bonds, and other security documents. The evaluation may be in respect of a note's validity and/or denomination.
Various methods and apparatus are known for identifying paper money and for determining the validity thereof. For example, U.S. Patent 2,950,799 to Timms describes apparatus for identifying paper money using ultra-violet light to measure the re-radiation and colour of a note, and U.S.
Patent 2,731,621 to Sontheimer describes a counterfeit detector using an optical scanner to produce electrical signals in accordance with the reflectivity of scanned portions of a document. Other methods using magnetic, acoustic, and mechanical means to evaluate notes are known for example from U.S. Patents 3,245,534, 3,208,974, 3,462,225 and 3,713,291.
These known methods and apparatus all suffer from various disadvantages. In particular, in machine sorting of bank notes it is desirable to be able automatically to recognize single note denominations, detect counterfei* notes, detect notes which through use should not be put back into circulation, and detect notes which are stuck together ("doubles"). Furthermore, these functions should desirably be achieved at a high sorting speed of for example 1200 notes per minute. All these features canno~ be achieved using known methods in a single apparatus in machine sorting of notes.
An object of this invention, therefore, is to provide a new and improved method of and apparatus for evaluating notes.
According to one aspect of this invention there is provided a methQd of evaluating a note, comprising the steps of illuminating at least a part of the note with X-rays, detecting X-rays fluorescing from the note, and counting the detected X-raysO The evaluation may be to determine the validity of the note, and/or it may be to determine the denomination of the note, in which case the counting step comprises establishing respec-tive counts for each of a plurality of different energy ranges ofdetected X-rays.
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..
. ~ `; .. .
iL~L3;~i2 According to another aspect of the invention there is provided apparatus for evaluating a note, comprising means for receiving a note to be evaluated, an X-ray source arranged to illuminate at least a part of a note received in the receiv-ing means with X-rays, means for detecting X-rays fluorescing from a note received in the receiving means, means for counting the detected X-rays, and means responsive to the counting means for providing an evaluation signal for the note. For determin-ing note validity the means fo:r providing an evaluation signal may comprise means for displaying a count established by the counting means during a predetermined period. For determining note denomination the counting means may comprise a respective counter for counting detected X-rays in each of a plurality of different energy ranges.
Conveniently the means for providing an evaluation signal comprises means for producing a control signal for determining a destination of the note, and the apparatus includes means for supplying the note from the receiving means to said destination.
In accordance with a further aspect this invention provides a method of machine sorting notes, comprising the steps of supplying notes to an evaluation zone, illuminating at least a part of each note in the evaluation zone with X-rays, detecting X-rays fluorescing from each note in the evaluation zone, counting the detected X-rays to evaluate each note, and supplying each note from the evaluation zone to a destination which is dependent upon the evaluation o the note.
According to yet another aspect this invention provides apparatus for sorting notes, comprising means for supplying notes to be sorted consecutively to an evaluation zone, an X-ray source arranged to illuminate at least a part of a note in the evaluation zone with X-rays, means for detecting X-rays fluorescing from a note in the evaluation zone, means for counting the detected X-rays to provide an evaluation signal for the note in the evaluation zone, and means respon-sive to the evaluation signal for supplying each note from the evaluation zone to a destination which is dependent upon the evaluation signal of the note~
.
1~32'~6;~
The invention is based on the recognition that X-ray fluorescence may be conveniently used ~o provide an accurate and thorough evaluation of notes, such as bank notes, at high speed. Such notes are printed with intaglio ink into which can be incorporated marker elements which when illuminated with X-rays produce characteristic fluorescent X rays at specific energies. The numbers and energies o such fluorescent X-rays are detected and quantitativeIy measured. For example, three such markers can be used seIectively and 2ither individually or in different combinations to provide each of seven different note denominations with a respective marker identification.
On illuminating such a marked note with X-rays, the fluorescent X-rays in each of three different energ~ ranges corresponding to the three markers can be detected and counted to ascertain the denomination of the note. This can be achieved at high speed in a mechanical note-sorter. If the count(s) do not reach specific lower limits, this indicates a low level of the marker(s) corresponding to a note which is counterfeit or worn so that it should not be put back into circulation. If the count(s) exceed specific upper limits, this indicates a high level of the marker(s) corresponding to two notes which are stuck together. Such notes can then be separated from the remaining notes for individual assessment.
The markers conveniently comprise heavier elements of the periodic table from strontium to bismuth. For example, such a marker can be barium in the form of barium sulphate, or tin in the form of tin oxide, or lead as lead sulphate which is incorporated into the intaglio ink used in printing the notes in place of part of the filler which is a conventional con-stituent of intaglio inks. The marker(s) may constitute, forexample, 30~ of the intaglio ink, and is preferably in excess of 10%, more preferably 20%, so that it can readily be detected.
Naturally ~ther markers, compatible with the other constituents and the requirements of the intaglio ink, may be used, and different numbers and combinations of markers may be provided as desired. For example, more than three different markers could be used to provide identification of a greater number of note denominations, or only a single marker could "
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be used to distinguish genuine Erom counterfeit notes without distinguishing between different note denominations. For certain denominations, existing notes already contain small but detectable amounts of a suitable element in the intaglio ink and the presence or absence of this element can be used as a test for the validity of the notes of these denominations.
Such markers, introdl~ced into the intaglio ink as stable insoluble compounds, have distinct advantages compared with ultraviolet-excLted f~oro~?hors previously used in notes, in particular in t~at they are much more permanent and less costl~. rnstead of being introduced into the intaglio ink, the markers could alternatïvely be incorporated into the paper of the notes.
According to yet another aspect of this invention there is provided a note, such as a bank note, comprising at least one stable and insoluble compound of an element in the periodic table from strontium to bismuth. The compound is preferably incorporated into intaglio ink with which the note is printed.
The invention will be further understood from the following description by way of example of embodiments thereof with reference to the accompanying drawings, in which:
~Fig. 1 schematically illustrates parts of apparatus for sorting bank notes embodying the present invention;
Fig. 2 schematically illustrates in cross-section a compact arrangement of an X-ray source and detector; and Fig. 3 schematically illustrates a block diagram of detection and counting circuitry which may be employed in the apparatus of Eig. 1.
* Referring to Fig. 1, which illustrates parts of a Crosfield 9300 type mechanical bank note sorter together with apparatus provided in accordance with an embodiment of the invention, bank notes 1, 2,each of any one of, for example, seven different denominati,ons are fed by means of spools 3,4 along a path indicated by arrows 5. The notes are thus fed consecutively through an evaluation zone, in which the note 2 *Trade Mark :
~3Z~
is located as illustrated in Fig. 1, wh:ich is backed -by a backing plate 6. The presence of a note in the evaluation zone is detected by means of two optical sensors 7, each of which for example comprises a light source and an optical detector.
An X-ray source 8 surrounded by a collimator shield assembly 9 emits X-rays along a path indicated by broken lines 10 to illuminate at least a part of the bank note -4a-~ ' ' ' ,' .: ~ .
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2 in the evaluation zone. A ~ail-sa~e shutter mechanism comprising a shutter 11 which in use is xetracted by , energisation of a solenoid 12 serves to cover the collimator shield assem~ly opening when, for example, a cover (not shown) over this part of the sorter is opened.
The X-ray source may be an X-ray tube or a radioactive X-ray source. The radioactive X-ray source is preferable, as it is more compact and less expensiVe. More preferably is an americium-241 source emitting 60 keV X-rays and having a half-life of 458 years.
Fluorescent X-rays from the bank note 2 pass along a path indicated by broken lines 13 to an X-ray detector 14, which detects the fluorescent X-rays and emits consequent electrical signals to electronic equipment generally referenced 15 and more fully described below with reference to Fig. 3.
A detector 14 such as an intrinsic germanium detector operates at a temperature of -217C which is maintained by continuously cooling the detector 14 with li~uid nitrogen contained in a dewar flask 16.
Fig. 1 illustrates the arrangement of X-ray source 8 and detector 14 only schematically and for purposes of explanation. In practice, it is desirable that the paths 10 and 13 of the X-rays be as short as possible, in order to confine the X-rays and reduce backscatter radiation detected by the detector. Fig. 2 illustrates a preferred compact arrangement of the X-ray source 8 and detector 14 in relation to a note 2 in the evaluation zone.
Referring to Fig. 2, the X-ray source 8 is an annulus of Am-241, and the collimator shield assembly 9 is an annulus within which the sourc~ 8 is located and which has,an ~nnular opening 17 through which the X-rays are emitted along the path 10. A central part 18 of the assembly 9 is open to the rear to allow the X-rays to illuminate a part of the note 2 in the evaluation zone, which in this case is directly behind the assembly 9 and is backed by the lead plate 6. Fluorescent X-rays , ,: : . :
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from the note 2 pass through the central part 18 of the assembly 9 and out through the open front thereof to the detector 14. A lead plate l9 ha~ing an aperture 20 therein through which the fluorescent X-rays pass along the path 13 may constitute or form part of the shutter 11 in Fig. 1.
In the arrangement of Fig. 2, the detector 14 is preferably an intrinsic germanium detector - Ge(INT)- having ; a circular detection area of 50 mm. diameter, providing a detection area of about 2000 mm.2, with a depletion depth of 10 mm., operated at a temperature of -217C to which it is cooled by liquid nitrogen as described with reference to Fig. 1. Such a detector has a usable energy range of 3 to 1000 keV with a resolution of about 500 eV at 30 keV, a dead time of about 0.5~us, and good gain and sensitivity stabiliky.
Accordingly, such a detector is well suited to the purpose of detecting X-rays fluoresced by markers in bank notes, to determine their denomination and validity, passing through a mechanical sorter or counter at high speed.
Other preferred X-ray detectors are the lithium drifted germanium detector (GeLi) and the lithium drifted silicon detector lSiLi) both of which operate at -217C. In addition other forms of X-ray detectors may be used, for example, those operable at room temperature and having the desired usable energy ranges, resolution, and response times.
The markers which are incorporated into the intaglio ink or paper of the bank notes 1, 2 may be selected from a large number of elements, using stable and insoluble compounds of these elements. Among the elements which may be used are the following elements with the following character-istic fluorescent X-ray energies:-`iB
,; .
- :. . i , .. . .
;: ' ~ , ~ ~:
:: . ~ -2~2 Symbol Element X-ray ene~ (keV) Ag Silver 22.
Cd Cadmium 23.2 In Indium 24.2 Sn Tin 25.3 Sb Antimony 26.4 Ba Barium 32.2 La Lanthanum 33.4 Ce Cerium 34.7 1~ Nd Neodymium 37.4 For example, if three different markers are used individually and in various combinations to distinguish between seven different denominations of bank notes, the markers could conveniently comprise Tin, Barium, and lead respectively to provide distinct fluorescent X-ray energies of 25.3, 32.2, and 15.5 keV respectively which are easily resolved by the detector 14 and are well distinguished from X-rays produced as backscatter radiation, for example X-rays from the shielding.
Such backscatter radiation can be further distinguished and removed by providing a copper or zinc transmission filter between the evaluation zone and the detector 14.
Fig. 3 illustrates in block diagrammatic form electronic circuitry provided in accordance with an embodiment of the invention as discussed above. Referring to Fig. 3, the electrical signals produced by the X-ray detector 14 are amplified in a pre-amplifier 21 and are conducted via a pulse shaper and base line level restorer 22 to a high speed analogue-to-digital converter 23. When a bank note 2 is present in the evaluation zone as illustrated in Fig. 1 the optical detector 24 in Fig. 3, corresponding to the sensors 7 in Fig. 1, emits a signal which is conducted via a logic start circuit 25 to initiate conversion operations of the converter 230 The resultant digital values are compared with digital values present on lines 26 corresponding to limits of channels, which comprise energy ranges of , , ~ .
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fluorescent X-rays to be detected and counted, in digital comparators 27, to produce for each channel pulses correspond-ing to detected X-rays within ~he respective energy range.
These pulses are counted ~or the respective channels in counters 28 to which count limit signals are applied via lines 29, the count limit signals corresponding to lower and upper counts which define limited count ranges corresponding to valid notes -of the respective denominations. Outputs ~rom the counters 28 are conducted to control logic circuitry 30 which produceA on lines 31 control signals which serve to control the destination in the sorting machine to which each evaluated bank note is routed in known manner. The count limits can be determined empirically for example by recording individual counts for a large number of valid notes of the same denomination and calculating the mean count and standard deviation.
The specific embodiment of khe invention described above is obviously only one of many different ways in which the present invention may be implemented, and numerous modifica-tions, variations, and adaptations may be made thereto without departing from the scope of the invention.
For example, different markers and combinations-thereof may be used, and other suitable X-ray source may be provided. The arrangement of the X-ray source and detector may be changed, and in particular diff~rent collimator shield assemblies may be utilized. The X-rays may be used to illuminate all of the bank notes or only parts thereof, and the markers may correspondingly be provided either throughout the notes or only in specific parts thereof, either in the paper or in the intaglio ink. The backing plate 6 could be dispensed wi~h or arranged differently to reduce backscatter radiation, and different arrangements could be provided for detecting the presence of a bank note in the evaluation zone.
Furthermore, although the invention has been particularly described as being applied to a high speed bank note sorting or counting machine, this need not necessarily be the case. In a simple form, the invention could consist of a small unit for ~, . . .
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verifying the validity of notes, such a unit comprising a holder for the note, an X-ray source, a detector for detecting X-rays fluorescing-from the note, and counting circuitry for counting the fluorescent X-rays. Such A unit could include a display for displaying the counted X-rays, or simply an indicator light providing a go/no-go indication of note validity. Obviously such a un:it could be xelatively simple as it would not have to vperate at high speed or determine note denominations.
In addition, whilst the invention has been described in relation to bank notes, it is of course equally applicable to other security documents, such as bonds.
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The X-ray source may be an X-ray tube or a radioactive X-ray source. The radioactive X-ray source is preferable, as it is more compact and less expensiVe. More preferably is an americium-241 source emitting 60 keV X-rays and having a half-life of 458 years.
Fluorescent X-rays from the bank note 2 pass along a path indicated by broken lines 13 to an X-ray detector 14, which detects the fluorescent X-rays and emits consequent electrical signals to electronic equipment generally referenced 15 and more fully described below with reference to Fig. 3.
A detector 14 such as an intrinsic germanium detector operates at a temperature of -217C which is maintained by continuously cooling the detector 14 with li~uid nitrogen contained in a dewar flask 16.
Fig. 1 illustrates the arrangement of X-ray source 8 and detector 14 only schematically and for purposes of explanation. In practice, it is desirable that the paths 10 and 13 of the X-rays be as short as possible, in order to confine the X-rays and reduce backscatter radiation detected by the detector. Fig. 2 illustrates a preferred compact arrangement of the X-ray source 8 and detector 14 in relation to a note 2 in the evaluation zone.
Referring to Fig. 2, the X-ray source 8 is an annulus of Am-241, and the collimator shield assembly 9 is an annulus within which the sourc~ 8 is located and which has,an ~nnular opening 17 through which the X-rays are emitted along the path 10. A central part 18 of the assembly 9 is open to the rear to allow the X-rays to illuminate a part of the note 2 in the evaluation zone, which in this case is directly behind the assembly 9 and is backed by the lead plate 6. Fluorescent X-rays , ,: : . :
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. . ~ :
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from the note 2 pass through the central part 18 of the assembly 9 and out through the open front thereof to the detector 14. A lead plate l9 ha~ing an aperture 20 therein through which the fluorescent X-rays pass along the path 13 may constitute or form part of the shutter 11 in Fig. 1.
In the arrangement of Fig. 2, the detector 14 is preferably an intrinsic germanium detector - Ge(INT)- having ; a circular detection area of 50 mm. diameter, providing a detection area of about 2000 mm.2, with a depletion depth of 10 mm., operated at a temperature of -217C to which it is cooled by liquid nitrogen as described with reference to Fig. 1. Such a detector has a usable energy range of 3 to 1000 keV with a resolution of about 500 eV at 30 keV, a dead time of about 0.5~us, and good gain and sensitivity stabiliky.
Accordingly, such a detector is well suited to the purpose of detecting X-rays fluoresced by markers in bank notes, to determine their denomination and validity, passing through a mechanical sorter or counter at high speed.
Other preferred X-ray detectors are the lithium drifted germanium detector (GeLi) and the lithium drifted silicon detector lSiLi) both of which operate at -217C. In addition other forms of X-ray detectors may be used, for example, those operable at room temperature and having the desired usable energy ranges, resolution, and response times.
The markers which are incorporated into the intaglio ink or paper of the bank notes 1, 2 may be selected from a large number of elements, using stable and insoluble compounds of these elements. Among the elements which may be used are the following elements with the following character-istic fluorescent X-ray energies:-`iB
,; .
- :. . i , .. . .
;: ' ~ , ~ ~:
:: . ~ -2~2 Symbol Element X-ray ene~ (keV) Ag Silver 22.
Cd Cadmium 23.2 In Indium 24.2 Sn Tin 25.3 Sb Antimony 26.4 Ba Barium 32.2 La Lanthanum 33.4 Ce Cerium 34.7 1~ Nd Neodymium 37.4 For example, if three different markers are used individually and in various combinations to distinguish between seven different denominations of bank notes, the markers could conveniently comprise Tin, Barium, and lead respectively to provide distinct fluorescent X-ray energies of 25.3, 32.2, and 15.5 keV respectively which are easily resolved by the detector 14 and are well distinguished from X-rays produced as backscatter radiation, for example X-rays from the shielding.
Such backscatter radiation can be further distinguished and removed by providing a copper or zinc transmission filter between the evaluation zone and the detector 14.
Fig. 3 illustrates in block diagrammatic form electronic circuitry provided in accordance with an embodiment of the invention as discussed above. Referring to Fig. 3, the electrical signals produced by the X-ray detector 14 are amplified in a pre-amplifier 21 and are conducted via a pulse shaper and base line level restorer 22 to a high speed analogue-to-digital converter 23. When a bank note 2 is present in the evaluation zone as illustrated in Fig. 1 the optical detector 24 in Fig. 3, corresponding to the sensors 7 in Fig. 1, emits a signal which is conducted via a logic start circuit 25 to initiate conversion operations of the converter 230 The resultant digital values are compared with digital values present on lines 26 corresponding to limits of channels, which comprise energy ranges of , , ~ .
. , ,.: .
:. ,. ,..................... ',"' -.
6~
fluorescent X-rays to be detected and counted, in digital comparators 27, to produce for each channel pulses correspond-ing to detected X-rays within ~he respective energy range.
These pulses are counted ~or the respective channels in counters 28 to which count limit signals are applied via lines 29, the count limit signals corresponding to lower and upper counts which define limited count ranges corresponding to valid notes -of the respective denominations. Outputs ~rom the counters 28 are conducted to control logic circuitry 30 which produceA on lines 31 control signals which serve to control the destination in the sorting machine to which each evaluated bank note is routed in known manner. The count limits can be determined empirically for example by recording individual counts for a large number of valid notes of the same denomination and calculating the mean count and standard deviation.
The specific embodiment of khe invention described above is obviously only one of many different ways in which the present invention may be implemented, and numerous modifica-tions, variations, and adaptations may be made thereto without departing from the scope of the invention.
For example, different markers and combinations-thereof may be used, and other suitable X-ray source may be provided. The arrangement of the X-ray source and detector may be changed, and in particular diff~rent collimator shield assemblies may be utilized. The X-rays may be used to illuminate all of the bank notes or only parts thereof, and the markers may correspondingly be provided either throughout the notes or only in specific parts thereof, either in the paper or in the intaglio ink. The backing plate 6 could be dispensed wi~h or arranged differently to reduce backscatter radiation, and different arrangements could be provided for detecting the presence of a bank note in the evaluation zone.
Furthermore, although the invention has been particularly described as being applied to a high speed bank note sorting or counting machine, this need not necessarily be the case. In a simple form, the invention could consist of a small unit for ~, . . .
2~6~
verifying the validity of notes, such a unit comprising a holder for the note, an X-ray source, a detector for detecting X-rays fluorescing-from the note, and counting circuitry for counting the fluorescent X-rays. Such A unit could include a display for displaying the counted X-rays, or simply an indicator light providing a go/no-go indication of note validity. Obviously such a un:it could be xelatively simple as it would not have to vperate at high speed or determine note denominations.
In addition, whilst the invention has been described in relation to bank notes, it is of course equally applicable to other security documents, such as bonds.
B
.~ ~ . - . ~ . ..
.... .
, . . . . . .
Claims (9)
1. Apparatus for evaluating a note marked with at least one compound which when illuminated with X-rays produces characteristic fluorescent X-rays of specific energy, compris-ing means for receiving a note to be evaluated, an X-ray source arranged to illuminate with X-rays at least a part of a note received in the receiving means, means for detect-ing fluorescent X-rays emitted from a note received in the receiving means, means for counting the detected X-rays, and means responsive to the counting means for providing an evaluation signal for the note.
2. Apparatus as claimed in claim 1, wherein the means for providing an evaluation signal comprises means for dis-playing a count established by the counting means during a predetermined period.
3. Apparatus as claimed in claim 1, wherein the counting means comprises a respective counter for counting detected X-rays in each of a plurality of different energy ranges.
4. Apparatus as claimed in claim 1 wherein the means for providing an evaluation signal comprises means for producing a control signal for determining a destination of the note.
5. An apparatus as claimed in Claim 1 wherein said note is a bank note.
6. A method of machine sorting for validation notes marked with at least one compound which when illuminated with X-rays produces characteristic fluorescent X-rays of specific energy, and chosen from heavy elements of the periodic table from strontium to bismuth comprising the steps of supplying notes to an evaluation zone, illuminat-ing at least a part of each note in the evaluation zone with X-rays detecting fluorescent X-rays emitted from each note in the evaluation zone, counting the detected X-rays to evaluate each note, and supplying each note from the evaluation zone to a destination which is dependent upon the evaluation of the note.
7. A method as claimed in claim 6 wherein said note is a bank note.
8. Apparatus for sorting notes marked with at least one compound which when illuminated with X-rays produces characteristic fluorescent X-rays of specific energy, comprising means for supplying notes to be sorted consecutively to an evaluation zone, an X-ray source arranged to illuminate at least a part of a note in the evaluation zone with X-rays, means for detecting fluorescent X-rays emitted from a note in the evaluation zone, means for counting the detected X-rays to provide an evaluation signal for the note in the evaluation zone, and means responsive to the evaluation signal for supplying each note from the evaluation zone to a destination which is depend-ent upon the evaluation signal of the note.
9. Apparatus as claimed in claim 8, wherein the counting means comprises a respective counter for counting detected X-rays in each of a plurality of different energy ranges.
Priority Applications (2)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CA338,500A CA1132262A (en) | 1979-10-26 | 1979-10-26 | Method and apparatus for evaluating notes |
| GB8031532A GB2062221B (en) | 1979-10-26 | 1980-09-30 | Evaluating notes by x-ray fluorecence |
Applications Claiming Priority (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CA338,500A CA1132262A (en) | 1979-10-26 | 1979-10-26 | Method and apparatus for evaluating notes |
Publications (1)
| Publication Number | Publication Date |
|---|---|
| CA1132262A true CA1132262A (en) | 1982-09-21 |
Family
ID=4115438
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CA338,500A Expired CA1132262A (en) | 1979-10-26 | 1979-10-26 | Method and apparatus for evaluating notes |
Country Status (2)
| Country | Link |
|---|---|
| CA (1) | CA1132262A (en) |
| GB (1) | GB2062221B (en) |
Families Citing this family (3)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| BG44997A1 (en) * | 1986-06-17 | 1989-03-15 | Jasen S Stamenov | |
| GB201004024D0 (en) * | 2010-03-11 | 2010-04-28 | Durham Scient Crystals Ltd | Method and system for the identification and authentication of objects |
| EP3278091B1 (en) * | 2015-04-02 | 2022-07-20 | Soreq Nuclear Research Center | System and method for reading x-ray-fluorescence marking |
-
1979
- 1979-10-26 CA CA338,500A patent/CA1132262A/en not_active Expired
-
1980
- 1980-09-30 GB GB8031532A patent/GB2062221B/en not_active Expired
Also Published As
| Publication number | Publication date |
|---|---|
| GB2062221B (en) | 1983-11-23 |
| GB2062221A (en) | 1981-05-20 |
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