Note: Descriptions are shown in the official language in which they were submitted.
~ ~Z'~6~
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.
-- 1 --
B ~
. .. . . .
..
. ~ `; .. .
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
- 3 -
"
:. . i ~
226~Z:
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-
~ ' ' '
,' .: ~ .
1~3Z26Z
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
-- 5 --
,
,: : . :
: ::
. . ~ :
1~3~;~6~
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
.~ ~ . - . ~ . ..
.... .
, . . . . . .
