U.S. patent application number 12/635856 was filed with the patent office on 2010-04-15 for method and apparatus for inspection of security articles incorporating a diffractive optical projection element.
This patent application is currently assigned to Securency International Pty Ltd.. Invention is credited to James Hock Hai Chua, Paul Henson, Anthony Nardella, Gary Fairless Power, Patrick Swift.
Application Number | 20100091268 12/635856 |
Document ID | / |
Family ID | 34744198 |
Filed Date | 2010-04-15 |
United States Patent
Application |
20100091268 |
Kind Code |
A1 |
Power; Gary Fairless ; et
al. |
April 15, 2010 |
METHOD AND APPARATUS FOR INSPECTION OF SECURITY ARTICLES
INCORPORATING A DIFFRACTIVE OPTICAL PROJECTION ELEMENT
Abstract
A method and apparatus for inspection of a security article (10)
is provided in which a substantially collimated light beam (15)
from a point light source (14) is directed onto a diffractive
optical projection element (DOE) (11). The light beam is
transformed by the DOE (11) into a patterned beam (17) which is
reconstructed to form a projected image at a particular position in
space remote from the surface of the security article 910). An
optical detection device 916) is located at which the patterned
beam (17) is reconstructed to detect the projected image. The
inspection method and apparatus may be used in equipment for
handling, sorting, counting or otherwise processing security
articles, in particular security documents such as banknotes. The
apparatus may include a processor for generating a signal when the
absence or poor quality of a DOE is detected and which is used to
isolate or mark the security article.
Inventors: |
Power; Gary Fairless;
(Greenvale, AU) ; Swift; Patrick; (Lancefield,
AU) ; Hai Chua; James Hock; (Castlecrag, AU) ;
Nardella; Anthony; (Taylors Lake, AU) ; Henson;
Paul; (Craigieburn, AU) |
Correspondence
Address: |
ANDRUS, SCEALES, STARKE & SAWALL, LLP
100 EAST WISCONSIN AVENUE, SUITE 1100
MILWAUKEE
WI
53202
US
|
Assignee: |
Securency International Pty
Ltd.
Craigieburn
AU
|
Family ID: |
34744198 |
Appl. No.: |
12/635856 |
Filed: |
December 11, 2009 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
|
|
10585506 |
May 9, 2007 |
7652757 |
|
|
12635856 |
|
|
|
|
Current U.S.
Class: |
356/71 |
Current CPC
Class: |
G07D 7/0032
20170501 |
Class at
Publication: |
356/71 |
International
Class: |
G06K 9/74 20060101
G06K009/74 |
Foreign Application Data
Date |
Code |
Application Number |
Jan 9, 2004 |
AU |
2004900118 |
Jan 10, 2005 |
AU |
PCT/AU2005/000016 |
Claims
1-41. (canceled)
42. An apparatus for inspection of at least one security article
incorporating a diffractive optical projection element as a
security device, the diffractive optical projection element being
provided in a substantially transparent or translucent portion or
window in the security document, wherein the apparatus comprises: a
light source for directing a beam of light onto said diffractive
optical projection element in said transparent or translucent
portion or window, wherein the diffractive optical projection
element transforms the beam into a patterned beam of light that is
reconstructed at a particular position in space to form a projected
image; and at least one optical detection device located at the
position at which the patterned beam of light is reconstructed to
form the projected image.
43. An apparatus according to claim 42 wherein the light source is
arranged to direct a substantially collimated beam of light onto
the diffractive optical projection element.
44. An apparatus according to claim 42 wherein the light source is
a point light source.
45. An apparatus according to claim 44 wherein the light source is
any one of: a light emitting diode (LED); or a halogen light
source; or a laser.
46. An apparatus according to claim 42 wherein the optical
detection device is arranged to detect the amplitude of different
parts of the patterned light beam forming the projected image.
47. An apparatus according to claim 46 wherein the optical
detection device comprises one or more photodiodes.
48. An apparatus according to claim 46 wherein the optical
detection device comprises a charge coupled device (CCD).
49. An apparatus according to claim 42 wherein the diffractive
optical projection element is provided in a substantially
transparent or translucent portion or window in the security
article, the light source is positioned on one side of a security
article and the detection means is positioned on the opposite side
of the security article such that the light passes through the
diffractive optical projection element so that the incident beam is
transformed into the patterned beam on the opposite side of the
document and projected onto the optical detection device.
50. An apparatus according to claim 42 wherein the diffractive
optical projection element is provided on an underlying reflective
surface, and the light source and optical detection device are
positioned on the same side of the security article such that the
optical detection device detects a reflected beam transformed by
the diffractive optical projection element into the patterned beam
and projected onto the optical detection device.
51. An apparatus according to claim 42 wherein the apparatus
includes a plurality of optical detection devices.
52. An apparatus according to claim 42 wherein the apparatus
includes a plurality of light sources for illuminating at least one
diffractive optical projection element.
53. An apparatus according to claim 52 wherein each of the light
sources causes a patterned beam to be diffracted at a slightly
different point on the optical detection device, creating multiple
signals at the optical detection device.
54. An apparatus according to claim 42 wherein the light source is
a moving light source which produces an incident light beam that
scans across the diffractive optical projection element to create
multiple signals at the optical detector.
55. An apparatus according to claim 42, further including a
processor for processing signals from the optical detection device,
and wherein the processor analyses multiple signals to
differentiate constructive diffraction produced by the diffractive
optical element from a random or diffuse scattering of light.
56. A method for inspection of at least one security article,
wherein the security article incorporates a diffractive optical
projection element as a security device, the diffractive optical
projection element being provided in a substantially transparent or
translucent portion or window in the security document, and wherein
the method comprises the steps of: directing a beam of light from a
light source onto said diffractive optical projection element, the
diffractive optical projection element provided in a substantially
transparent or translucent portion or window in the security
document transforms the beam into a patterned beam of light that is
reconstructed at a particular position in space to form a projected
image; and detecting the projected image with an optical detection
device located at the position at which the patterned beam of light
is reconstructed to form the projected image.
57. A method of processing or handling security articles comprising
a method for inspection in accordance with claim 56, wherein a
signal is generated when the absence or poor quality of a
diffractive optical projection element is detected in a security
article.
58. A method of processing or handling security articles as claimed
in claim 57 wherein the security article is isolated or marked when
the signal is generated by the optical device.
Description
[0001] This invention relates to security articles, such as
banknotes or other security documents, and is particularly
concerned with providing a method and an apparatus for inspecting a
security device or devices in one or more security articles.
[0002] As used herein, the term "security documents" includes
documents and tokens such as identity documents, value documents or
entrance documents, which in turn respectively include: passports,
visas, identity cards, drivers licences, and security entrance
cards, banknotes, shares, bonds, certificates, cheques, lottery
tickets, bank cards, charge cards and credit cards, and aeroplane
tickets, bus tickets, railroad tickets, and tickets to fun parks or
specific rides. These security documents or tokens typically
include some form of authenticity verification to guard against
copying and fraudulent alteration. It will, however, be appreciated
that this invention is applicable to other types of articles which
require authentication and/or protection against copying or theft.
Such articles, including security documents, are referred to
broadly as "security articles" in this specification.
[0003] A wide variety of security devices have been proposed for
use in security documents for verification of authenticity and to
make counterfeiting of the documents difficult. Some types of
security devices are low security devices, printed devices or
embossings, which are relatively inexpensive to produce in security
documents but which only provide a relatively low degree of
security. Other types of security devices are high security
devices, such as diffraction gratings or holograms. These can
provide a higher degree of security because they are more difficult
to counterfeit, but are more expensive to produce and so are
generally used in higher value security documents, such as $50 or
$100 banknotes, when high security devices are provided in
banknotes, it is desirable to detect their presence and quality in
the production process of the banknotes before the banknotes are
issued to the public. It is also desirable to provide apparatus for
inspecting a high security device in a single banknote.
[0004] WO 99/37488 discloses a security document and method in
which a diffractive optical projection element is provided within a
transparent portion or window in the document, The diffractive
optical projection element transforms a collimated beam of light,
e.g. from a point light source or laser, into a patterned beam of a
selected design. In the method of verifying the authenticity of the
security document described in WO 99/37488, the patterned beam is
projected onto a viewing surface, e.g. by folding the security
document so that another part of the document laterally spaced from
the window acts as the viewing surface. In another embodiment, the
security document of WO 99/37488 may include a second transparent
portion or window which can act as a pseudo point light source when
the security document is folded.
[0005] In each embodiment described in WO 99/37488, the
authenticity of the security document incorporating the diffractive
optical projection element is verified visually by a person viewing
the patterned beam when it impinges upon a viewing surface.
However, this visual viewing method is not very suitable for
inspecting the presence or quality of diffractive optical elements
in banknotes or sheets of banknotes in equipment such as printing
equipment, note sorting equipment or other equipment used in
processing banknotes or the like.
[0006] According to one aspect of the invention, there is provided
a method for inspection of at least one security article, wherein
the security article incorporates a diffractive optical projection
element as a security device, and wherein the method comprises the
steps of:
[0007] directing a beam of light from a light source onto said
diffractive optical projection element which transforms the beam
into a patterned beam of light, that is reconstructed at a
particular position in space to form a projected image; and
[0008] detecting the projected image with at least one optical
detection device located at a position at which the patterned beam
of light is reconstructed to form the projected image.
[0009] The "diffractive optical projection element" used in the
invention is a diffractive microstructure which comprises an array
of cells each designed to transform the phase of a coherent
illuminating beam by a specified amount. The diffracted wavefronts
transformed by the individual cells form a patterned beam of light
and interfere in a particular reconstruction plane remote from the
plane of the diffractive optical element thereby forming the
projected image in the reconstruction plane. Therefore, the
location of the optical detection device substantially in the
reconstruction plane of the diffractive optical projection element
is important in the present invention. This requires knowledge of
the particular diffractive optical projection element to be
detected in order to set up the apparatus for inspection.
[0010] According to a second aspect of the invention, there is
provided an apparatus for inspection of at least one security
article incorporating a diffractive optical projection element as a
security device, wherein the apparatus comprises:
[0011] a light source for directing a beam of light onto said
diffractive optical projection element which transforms the beam
into a patterned beam of light that is reconstructed at a
particular position in space to form a projected image; and
[0012] at least one optical detection device located at the
position at which the patterned beam of light is reconstructed to
form the projected image.
[0013] The light source is preferably arranged to direct a
substantially collimated beam of light onto the diffractive optical
projection element. The light source is preferably a point light
source, such as a light emitting diode (LED), a halogen light
source or a laser (solid state or otherwise). It will, however, be
appreciated that other types of point light sources may be
used.
[0014] The optical detection device is preferably arranged to
detect the amplitude of different parts of the patterned light beam
forming the projected image. The optical detection device may
comprise one or more photodiodes, e.g. an array of photodiodes, or
a charge couple device (CCD), such as a line CCD or a matrix
CCD.
[0015] In one preferred embodiment, the diffractive optical
projection element is provided in a substantially transparent or
translucent portion or window in a security document, the light
source is positioned on one side of the security document and the
optical detection device is positioned on the opposite side of the
security document. Thus light passes through the diffractive
optical projection element and the incident light beam is
transformed into the patterned beam on the opposite side of the
document and projected onto the optical detection device.
[0016] In an alternative embodiment, the diffractive optical
projection element may overlie a reflective surface, such as a
metallic layer or coating of the security article. In this case,
the light source and the detection means may be provided on the
same side of the security article with the optical detection device
detecting a reflected beam transformed by the diffractive optical
projection element into the patterned beam and projected onto the
detection means.
[0017] In accordance with the invention the apparatus may be
incorporated into a wide variety of equipment for printing,
sorting, counting, handling or otherwise processing security
documents. For example, a light source and associated detection
means may be provided for inspecting individual banknotes in a note
counter or note sorter. The apparatus may include a plurality of
optical detection devices, for instance when a sheet containing a
plurality of banknotes each containing diffractive optical
projection elements is required to be inspected, e.g. during the
printing of a sheet of banknotes.
[0018] The apparatus preferably includes a processor for processing
signals from the optical detection device.
[0019] According to a third aspect of the invention there is
provided equipment for sorting, handling or otherwise processing
security articles comprising inspection apparatus in accordance
with the second aspect of the invention and article processing
means for subsequently processing the security articles according
to signals from the optical detection device. For example, if the
detection device identifies a faulty security article, it may emit
a signal rejecting the faulty article so that the article can be
marked for rejection and/or rejected from the security article
processing equipment.
[0020] According to a fourth aspect of the invention, there is
provided equipment for sorting, handling, counting or otherwise
processing security documents, the equipment including:
[0021] a detector for detecting the presence of a security
document;
[0022] a window locator for locating a window in the security
document incorporating a diffractive optical element;
[0023] a light source for directing a beam of light through said
diffractive optical projection element in said window whereby the
diffractive optical projection element produces a patterned beam of
light which forms a projected image;
[0024] an optical detection device located at a position at which
the patterned beam of light is reconstructed to form the projected
image;
[0025] a processor for processing and analysing signals from the
optical detection device; and
[0026] a document processing means for processing the security
documents according to the signals from the optical detection
device.
[0027] According to a fifth aspect of the invention, there is
provided a method of processing or handling security articles
comprising a method for inspection in accordance with the first
aspect of the invention, wherein a signal is generated by the
optical device when it detects the absence or poor quality of a
diffractive optical projection element in a security article, and
isolating or marking the security article.
[0028] In a further embodiment, a plurality of light sources may be
provided for illuminating at least one diffractive optical
projection element. Each of the light sources may cause a patterned
beam to be diffracted at a slightly different point on the optical
detection device, creating multiple signals on the same detector.
By integrating these signals and sampling the signal over a period
of time, it is possible to differentiate constructive diffraction
produced by the diffractive optical projection element from a
random or diffuse scattering of light, such as that caused by a
scratch or a surface imperfection, or light transmitted through a
standard diffraction grating or hologram. It is also envisaged that
a moving light source which produces an incident light beam that
scans across the diffractive optical projection element could be
used to create multiple signals at the optical detector.
[0029] Preferred embodiments of the present invention will now be
described, by way of example only, with reference to the
accompanying drawings, in which:
[0030] FIG. 1 is a schematic drawing of apparatus for inspecting a
security document incorporating a diffractive optical projection
element;
[0031] FIG. 2 is a schematic drawing of apparatus for inspecting a
modified security document;
[0032] FIG. 3 is a block diagram of sorting equipment incorporating
the inspection apparatus of FIG. 1 or FIG. 2; and
[0033] FIG. 4 is a schematic flow chart of a method of sorting
documents using the equipment of FIG. 3.
[0034] FIG. 1 shows apparatus for inspection of a security document
10 incorporating a diffractive optical projection element (DOE) 11
provided in a transparent portion or window 12 of the document 10.
The apparatus comprises a point light source 14 which directs an
incident beam of substantially collimated light 15 onto the DOE 11,
and detection means in the form of an optical detection device
16.
[0035] In one preferred embodiment, the security document 10 may be
formed from an at least partially transparent substrate having one
or more opacifying layers or coatings applied to at least one face
of the substrate. The transparent portion or window 12 of the
security document 10 may be formed by applying the opacifying
layers or coatings to the substrate in such a manner that the
substrate 12 is substantially free of opacifying layers or coatings
in the region of the transparent portion or window 12. The
transparent substrate may be formed from a transparent polymeric
material, such as polyethylene (PE), polypropylene (PP) or
polyethylene terephthalate (PET). In the case of a banknote, the
substrate is preferably formed from at least one biaxially oriented
polymeric film. The substrate may comprise a single film of
polymeric material. Alternatively, the substrate may comprise a
laminate of two or more layers of transparent biaxially oriented
polymeric film.
[0036] It will, however, be appreciated that the present invention
is equally applicable to security documents formed from paper or
other partially or fully opaque material. In this case, an aperture
may be formed in the paper or other material and a patch of
transparent polymeric material inserted into or applied over the
aperture to form the transparent portion or window 12.
[0037] The opacifying layers may comprise one or more of a variety
of opacifying inks which can be used in the printing of banknotes
or other security documents. For example, the layers of opacifying
ink may comprise pigmented coatings comprising a pigment, such as
titanium dioxide, dispersed within a binder or carrier of
cross-linkable polymeric material.
[0038] The diffractive optical projection element 11 acts to
transform the incident light beam 15 from the point light source 14
as the beam passes through the at least partially transparent
portion 12 of the security document (the window created through the
security document) into a patterned beam 17 of selected design. The
diffractive optical projection element is of the type which acts to
generate the patterned beam 17 by diffraction of the light beam 10.
One example of such a device is a diffractive optical projection
element or diffuser made by Mems Optical, Inc. in accordance with
WO 98/32590. Such devices are complicated surface micro relief
structures similar to diffraction gratings. Whilst the optical
transformation of the incident light beam 15 to the patterned beam
17 is based on the optical principle of diffraction, the
mathematics of the structure of such devices is specifically
designed in each case to produce a distinct optical transformation
in order to produce a desired patterned image which is
reconstructed at a particular point in space away from the security
document 10, Each diffractive optical projection element 11 can be
dependent on the wavelength of the light beam used.
[0039] The point light source 14 for producing the incident beam 15
may comprise an LED, a halogen light source, a laser or other light
source for producing a beam of substantially collimated light which
is directed on the DOE 11.
[0040] The optical detection device 16 is positioned at the
particular point in space at which the patterned beam 17 forms the
patterned image projected by the DOE 11.
[0041] The various points in space of the image projected by the
DOE 11 are determined by the special focal coordinates created by a
sinusoidal grating which constitutes the DOE 11 and the positions
of the light source 14 and detector 16 relative to the DOE 11.
[0042] The presence of the patterned image projected by the DOE 11
is determined by the amplitude of the response of the detector 16
at particular points in space where the detector is located. For
this purpose, the detector may comprise an array of photo-diodes
18, or a charge couple device (CCD) such as a line CCD or a matrix
CCD.
[0043] FIG. 2 shows a modified embodiment which is similar to FIG.
1 and corresponding reference numerals have been applied to
corresponding parts. The security document 20 in FIG. 2 differs
from that of FIG. 1 in that the transparent portion or window 12
incorporates a reflective surface 21 underneath the diffractive
optical projection element (DOE) 11. The reflective surface may be
provided by a metallic layer 22 provided within the window 12 or by
a metallised coating applied to a surface of the transparent
portion forming the window 12 before the DOE 11 is applied over the
reflective surface 21.
[0044] The apparatus of FIG. 2 also differs from that of FIG. 1
insofar as the point light source 24 and the optical detector 26
are located on the same side of the security document 20. The light
source 24 is arranged to direct a substantially collimated incident
beam 15 onto the window 12 at an acute angle to the perpendicular
to the surface of the security document 20 so that the incident
beam 15 is reflected back from the reflective surface 21 of the
metallic layer 22 onto the DOE 11. The reflected beam passes
through the DOE 11 and is transformed by the DOE 11 into a
patterned beam 17 in similar manner to the embodiment of FIG.
1.
[0045] The detector 26, which may also comprise an array of
photo-diodes 18 or a line or matrix CCD, is disposed at a position
relative to the security document 20 to receive the patterned beam
17 which also travels from the DOE 11 at an acute angle to the
perpendicular to the surface of the security document 20
corresponding to the angle of the incident beam 16. Otherwise, the
detector 26 functions in exactly the same manner as the detector of
FIG. 1 by determining the amplitude of different parts of the
reconstructed projected image formed by the patterned beam 17 at
particular points in space where the photo-diodes 18 are
located.
[0046] In an alternative embodiment similar to FIG. 2, the light
source 24 is arranged to direct the substantially collimated
incident beam at an acute angle onto the DOE 11 which transforms
the beam into a patterned beam 17 that is reflected by the
reflective surface 22 and projected onto the detector 26 located at
the particular position in space where the projected image is
reconstructed by the patterned beam 17. It is also possible that
the DOE could be viewed in reflection without an underlying
metallic surface using the reflectivity of the polymer surface,
[0047] FIGS. 3 and 4 illustrate sorting equipment and a method of
sorting security documents utilizing the inspection apparatus of
FIG. 1 or FIG. 2.
[0048] The sorting equipment of FIG. 3 comprises an edge detector
30 for detecting the presence of a security document, such as a
banknote, or a sheet of banknotes, a window locator 32 for locating
a window 12 in a security document incorporating a DOE 11, an
optical detector 16, 26 in the form of a CCD or photo-diode array
for inspecting a patterned beam 17 from the DOE 11, a processor 34
for processing and analysing signals from the optical detector 16,
26, a barcode printer 36 and a document sorter 38 for sorting the
security documents according to the signals from the optical
detector 16, 26.
[0049] The method of operation of the sorting equipment of FIG. 3
is illustrated by the flow chart of FIG. 4. When a security
document, e.g. a banknote, or a sheet of banknotes enters the
sorting equipment, the edge detector 30 detects the presence of a
banknote, or a sheet of notes, by detecting the edge of the note or
sheet (Step 40). When the window locator 32 locates a window in the
note or sheet (Step 42), e.g. by means of a time gated output from
the processor 34, the light source (14, 24) and the CCD or
photodiodes of the optical detector 16, 26 of the inspection
apparatus are activated (Step 44).
[0050] The optical detector 16, 26 then performs its inspection of
the security document and produces output signals that are input to
the processor 34 which analyses the signals (Step 46). The
processor 34 may comprise a process logic controller (PLC) or a
microprocessor, such as a PIC chip, and can not only determine
whether a DOE 11 is present in the window of the document, but can
also determine the quality of the DOE by its inspection of the
projected image formed by the patterned beam 17 from the DOE.
[0051] From its signal analysis, the processor (PLC) 34 determines
whether or not the banknote should be accepted or rejected (Step
48), and outputs either an accept signal (Step 50) or a reject
signal (Step 52). The output signals from the processor 34 are
input to the barcode printer 36 which prints either an accept code
(Step 54) or a reject code (Step 56) on the banknote or sheet of
banknotes, The banknote or sheet of banknotes are then fed to the
sorter 38 which sorts the documents (Step 58) by sending those
marked with an accept code (54) to a delivery stack and by sending
those marked with a reject code (56) to a reject stack.
[0052] The method and apparatus of the present invention therefore
provides an efficient way of automatically inspecting security
articles, such as banknotes, which incorporate diffractive optical
projection elements (DOEs) as high security devices.
[0053] The inspection method and apparatus may be used in a wide
variety of equipment, such as printing equipment, note counting or
sorting equipment or any other equipment used in the printing,
handling or processing of security documents or other security
articles.
[0054] It will be appreciated that various modifications and
alterations may be made to the embodiments described above without
departing from the cope and spirit of the present invention. For
example, the inspection apparatus of FIG. 1 or 2 may be used to
inspect other types of security articles having either a DOE
provided in a transparent portion or window or a DOE provided on a
reflective surface of the security article, 20.
* * * * *