Note : Les descriptions sont présentées dans la langue officielle dans laquelle elles ont été soumises.
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METHODS FOR IDENTIFICATION AND VERIFICATION
REFERENCE TO RELATED APPLICATIONS
This application is a continuation-in-part application of U.S. Provisional
l0 Application Serial No. 60/157,573, the disclosure of which is incorporated
herein by
reference.
FIELD OF THE INVENTION
The present invention generally relates to apparatus and methods for
identification and verification. More particularly, the present invention
relates to
apparatus and methods for detecting an element or compound intrinsically
present-flr
extrinsically added-in an article or product by using X-ray fluorescence to
identify
and verify that article or product.
BACKGROUND OF THE INVENTION
There has been significant interest in apparatus and methods for identifying
2o and verifying various articles or products such as explosives, ammunition,
paint,
petroleum products, and documents. Known methods used to identify and verify
generally involve adding and detecting materials like code-bearing
microparticles,
bulk chemical substances, and radioactive substances. Other methods used for
identify and verify articles include those described in U.S. Patent Nos.
6,030,657,
6,024,200, 6,007,744, 6,005,915, 5,760,394, 5,474,937, 5,301,044, 5,208,630,
5,057,268, 4,862,143, 4,390,452, 4,363,965, and 4,045,676, the disclosures of
which
are incorporated herein by reference.
It is also known to apply materials to articles in order to track, for
example,
point of origin, authenticity, and their distribution. In one method, inks
which are
3o transparent in visible light are sometimes applied to materials and the
presence (or
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absence) of the ink is revealed by ultraviolet or infrared fluorescence. Other
methods
include implanting microscopic additives which can be detected optically.
However,
detecting these materials is primarily based on optical or photometric
measurements.
Unfortunately, many of the apparatus and methods for identifying and
verifying articles using such materials (called taggants) are unsatisfactory
for several
reasons. First, they are often difficult and time-consuming. In many
instances, a
sample of the article must be sent to an off site laboratory for analysis. In
other
instances, the apparatus are often expensive, large, and difficult to operate.
In yet
other instances, the taggant used is radioactive, causing serious health
concerns.
to The known apparatus and methods for identifcation and verification are also
unsatisfactory because they require a "line-of sight" analysis method. This
line of
sight requirement entails that the apparatus must be able to "see" the taggant
in order
to detect it. This can be detracting when it would be desirable to detect the
taggant
without having to see the taggant, e.g., such as when the taggant is located
in the
middle of large package with packaging and labels "covering" the taggant.
SUMMARY OF THE INVENTION
The present invention provides an apparatus and method in which one or more
taggants that are intrinsically located--~r extrinsically placed-in an article
or
product are detected by x-ray fluorescence analysis to identify or verify the
article or
2o its point of manufacture. The taggants are manufactured as part of the
article or the
taggant is placed into a coating, packaging, label, or otherwise embedded
within the
article for the purpose of later verifying the presence or absence of these
elements by
x-ray fluorescence to determine the unique elemental composition of the
taggant
within these articles.
By using x-ray fluorescence analysis, the apparatus and methods of the present
invention are simple and easy to use, as well as provide detection by a non
line-of
sight method to establish the origin of materials, point of manufacture,
authenticity,
verification, or product security. The present invention is extremely
advantageous
because it is difficult to replicate, simulate, alter, transpose, or tamper.
Further, it is
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easily recognizable by a user in either overt or covert form, verifiable by a
manufacturer or issuer, and is easily applicable to various forms of media in
the
articles.
BRIEF DESCRIPTION OF THE DRAWINGS
Figures 1, 2a, 2b, 3, 4a, 4b, and 5-7 are views of apparatus and methods for
identification and verification according to the present invention. Figures 1,
2a, 2b, 3,
4a, 4b, and 5-7 presented in conjunction with this description are views of
only
particular-rather than complete-portions of apparatus and methods for
identification and verification.
to DETAILED DESCRIPTION OF THE INVENTION
The following description provides specific details in order to provide a
thorough understanding of the present invention. The skilled artisan would
understand, however, that the present invention can be practiced without
employing
these specific details. Indeed, the present invention can be practiced by
modifying the
~s illustrated apparatus and method and can be used in conjunction with
apparatus and
techniques conventionally used in the industry.
The present invention uses x-ray fluorescence analysis to detect at Ieast one
taggant which is intrinsically or extrinsicaliy present in the material of a
product or
article. With x-ray fluorescence (XRF) analysis, x-rays produced from electron
shifts
2o in the inner shells) of atoms of the taggants and, therefore, are not
effected by the
form (chemical bonding) of the article being analyzed. The x-rays emitted from
each
element bear a specific and unique spectral signature, allowing one to
determine
whether that specific taggant is present in the product or article.
Figures 1, 2a, and 2b represent how it is believed XRF generally operates. In
25 Figure l, primary gamma rays or x-rays 40 are irradiated on a sample of a
target
material 46 of article 42. Secondary x-rays 44 are emitted from that sample of
target
material 46
In Figures 2a and 2b, atom 48 of a taggant located within target material 46
has nucleus 50 surrounded by electrons 52 at discrete distances from nucleus
50
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(called electron shells). Each electron shell has a binding energy level equal
to the
amount of energy required to remove that electron from its corresponding
shell. The
innermost shell is the K shell, and has the highest binding energy level
associated with
it. Electron 54 is located within K shell 56.
Primary x-ray or gamma ray photon 40 impacting atom 48 has a given energy.
If that energy is greater than the binding energy level of K shell 56, the
energy of x-
ray photon 40 is absorbed by atom 48, and one of the electrons in K shell 56
(i.e.,
electron 54) is ejected. With a vacancy now in K shell 56 left by electron 54,
atom 48
is energetic and unstable. To become more stable, that vacancy in K shell 56
can be-
to and usually is-filled by an electron located in a shell with a lower
binding energy
level, such as L-shell electron 58 in L shell 60. As L-shell electron 58 fills
the vacancy
in K shell 56, atom 48 emits a secondary x-ray photon 44. The energy levels
(or
corresponding wavelengths) of such secondary x-ray photons are uniquely
characteristic to each taggant, allowing the presence or absence of any
specific taggant
to be determined.
The at least one taggant can be intrinsically or extrinsically present in the
product to be detected (the "target material'. When the taggant(s) is
intrinsically
present, it is a component (either as an element, compound, or other type of
composition) in at least one portion of that target material. When the
taggant(s) is
2o extrinsically present, it can be added, incorporated, or inserted into the
target material
as described below.
The at least one taggant employed in the present invention can be any suitable
taggant known in the art. See, for example, U.S. Patent Nos. 5,474,937,
5,760,394,
and 6,025,200, the disclosures of which are incorporated herein by reference.
Suitable
taggants include any element or compound which is capable of being detected
via
XRF. The type of elements that can be used as the taggant are theoretically
any of
those listed in the periodic table, but the lower energy emitted by electrons
in the
lower atomic-number elements could be a limiting factor. Such lower energies
can be
re-absorbed much easier into its own material matrix or, in some cases, into
the
3o ambient atmosphere (e.g, air). Further, different isotopes of an element,
as well as
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elements which "excite" only under certain conditions-such as specif c
temperature
ranges-could be employed as the taggant in the present invention. Example of
taggants that could be used in the present invention include any element with
an
atomic number ranging from 6 to 94. Preferably, rare earth metals are used as
the at
least one taggant in the present invention. More preferably, gadolinium (Gd)
or
yttrium (Y) is used as the at least one taggant in the present invention.
The type of taggant depends, among other things, on the target material in
which it is located. The target material can interfere with the XRF detection
because,
as described below, backscattering and peaks emitted by the composition of the
target
l0 material during XRF analysis can interfere with the taggant peaks. For
example, if
paper contained an As taggant and trace amounts of Pb existed in the paper,
the K-
ievel electrons of As and L-Ievel electrons of Pb could give confusing
readings during
XRF detection.
In one aspect of the invention, the type of taggant should be selected based
on
the ability of the taggant and/or the substance in which it is located (i.e.,
a coating) to
attach or bond to the target material. In many instances, the target material
will be
used, handled, and/or washed extensively. If the taggant (or the substance in
which is
located) is removed from the target material under such conditions, tagging
the target
material is of little value. For example, if a film or coating (e.g., ink)
containing a
taggant is applied to a target material (e.g., paper), the taggant and coating
should be
selected so that they will not be removed by the conditions to which the
target
material is periodically subjected (e.g., extensive contact with hands).
Preferably, the
coating andlor the taggant is selected in this aspect of the invention so that
it
chemically attaches or bonds to the target material, like paint attaches and
bonds with
a wall.
In another aspect of the invention, the type of taggant can be selected based
on
the ability of the taggant and/or the substance in which it is located (i.e.,
a coating) to
be removed from the target material. In many instances, the purpose for which
the
target material is tagged will be temporary. After this purpose is completed,
the
taggant is no longer needed and can optionally be removed. For example, if an
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identifying film or coating containing a taggant is applied to a target
material, once
the target material has been identified, the identifying film of coating may
no longer
be needed and can be removed by suitable means. Preferably, the coating and/or
the
taggant is selected in this aspect of the invention so that it is removable by
mechanical
or chemical means.
The amount and concentration of the taggant in the target material can also
vary depending on the number of elements used and energy needed. The amount of
taggant employed in the present invention is determined by the minimum amount
needed for XRF detection. Additional amounts of taggant can be used as
described
1o below. The concentration of the taggant is at least about 1 part per
million (pprn), and
can range from about 1-100 ppm. Larger taggant amounts can be used, but for
economic reasons, a small amount is sufficient. Even lower taggant
concentrations
can be used (i.e, less than 1 ppm} as improved XRF devices and techniques
become
available.
The form of the taggant in the target material can also vary. The form can be
any compound (i.e., salt) or molecule-either small or large-containing the
element
that is added by itself or with other components. Indeed, the taggant can be
combined
with various components and/or additives to make a mixture and/or solution.
These
other components or additives can be selected for various purposes, e.g., to
modify the
XRF properties, to modify the ability to be inserted into an article/product,
to stabilize
the mixture or solution, or other purpose known in the chemical arts.
In one aspect of the invention, the at least one taggant is a combination or
plurality of taggants. A plurality of taggants could include more than one
taggant of
the same type, e.g., the same element or compound. A combination of taggants
could
also be more than one type of taggant, e.g., a different element or compound
in
different media. For example, a taggant dispersed in ink which has been placed
on
paper which also contains the same or different taggant. The plurality of
taggants
could also include a combination of at least one intrinsic and at least one
extrinsic
taggant.
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The at least one taggant incorporated in the target material can provide a
distinctive code. Such a code could be based on the number and types of
taggants
present or absent, an abundance ratio (i.e., concentrations) of the same or
different
taggants, the location of the taggants within the material {i.e., a barcode
made of a
series of taggants with a space, where the space could be part of the code),
the
presence of multiple types or forms of a single taggant, or a combination
thereof.
As one example of such a code, the present invention can include a system in
which the concentration of one taggant in a targeted material is controlled to
provide a
distinctive code. For example, for tagging ten commercially prepared batches
of
to carpeting, the taggant yttrium oxide can be used. Ten unique codes could
then be
created for these ten batches by preparing samples of the target material
containing
various concentrations (i.e., 10 ppm, 20 ppm, . .. 100 ppm) of that taggant.
The number of unique codes available with the use of just a single taggant
depends on the precision with which that concentration can be controlled and
measured in the sample. For example, if techniques allow concentrations in
about 10
ppm increments, 10 unique codes (i.e., 10 ppm, 20 ppm, ... 100 ppm) can
readily be
constructed from a single taggant for that concentration range. Additional
codes
could ,be created for larger concentration ranges, e.g., 100 codes of a
concentration
ranging from 10 ppm to 1000 ppm in 10 ppm increments. With the advent of
superior
concentration and detection techniques (e.g, for smaller increments), more
codes may
be constructed.
Further, the number of unique codes can be increased by adding additional
types and concentrations of the same or different taggants. A significant
increase in
the number of possible codes can be achieved by using more than one taggant in
creating the code. For example, the code can be expanded by adding another
taggant
with its own specific concentrations. The number of codes can be further
expanded
by adding a third taggant with its own specific concentrations. Additional
taggants
could be used to provide even more codes. This coding system depends on the
concentration increments of each of the taggants.
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The number of codes available in the coding system could also be increased by
varying the location of the taggant(s) within the material to be detected. For
example,
the detected material could be divided into any number of portions (i.e.,
quadrants)
with certain taggants {or codes) being placed in certain of those portions,
and
optionally not in others, to signify additional information during the XRF
analysis.
When taggants include elements or compounds that may be found in the target
material or in the environment to which the target material may be exposed,
taggant
contamination may occur and possibly render the taggant code difficult to
read. For
example, if the taggant comprising yttrium oxide is located in carpet as the
targeted
to material, it is possible that additional amounts of the taggant(s) could be
present in the
targeted material as a result of environmental contamination, an internal
chemical
reaction, or other contamination. If this contamination occurs, there will be
a change
in the concentration of that taggant in the target material. Subsequent
measurement of
this taggant could yield a value corresponding to an incorrect code.
is In such an instance, it is difficult to determine what amount of the
taggant
present in the targeted material is "contamination" as opposed to taggant
present
before contamination. This problem can be solved in target materials for which
contamination might be suspected by using a backup (i.e., duplicate or
otherwise) or
secondary system, such as a backup or secondary taggant(s), backup or
secondary
2o code, or backup or secondary location. See, for example, the description in
U.S.
Patent No. 5,760,394, the disclosure of which is incorporated herein by
reference. If
desired, more than one such backup or secondary system can be used. The backup
or
secondary system can also be used for other purposes, e.g., to verify the
original
coding system.
25 Any suitable target material can be employed in the present invention.
Suitable target materials include those which intrinsically contain the
desired
taggant(s) or in which the desired taggant(s) can be incorporated. Because XRF
detection measures changes in the inner shells) of the taggant, it will not be
significantly modified by chemical reactions which normally occur in the outer
shells.
3o Thus, it is possible to tag chemicals and have the taggant code be carried
in any
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product manufactured with those chemicals. Target materials should be
comprised of
a material in which XRF detection is easy, e.g., little chance of background
contamination, taggant deterioration, taggant destruction, contamination, or
other
deteriorating condition.
Example of suitable target materials include: paper products like documents,
currency, or tickets; solid products Iike jewelry, carpets, packaging (films,
labels, and
adhesives}, metals, rubbers (tires), woods, or plastics (credit cards); liquid
products
like lubricating fluids, resins, sprays, paints, oils, inks; hazardous wastes;
drugs or
pharmaceuticals; gaseous products; or combinations or hybrids of these
materials.
Additionally, suitable target materials-such as paper documents, drugs, or
counterfeit manufactured items-include those that will be subsequently
changed.
For example, a target material that is suspected might be destroyed could be
tagged
with elements known to be present in the residue from the destruction. Since
the
taggant is not usually changed by the chemical process in destruction, a
connection
between the target material and its residue could be established after
destruction.
Preferably, the target material of the present invention is carpeting and
carpet
products.
The target materials containing the at least one taggant can be used for a
wide
number of applications. For example, tagging paints would allows any article
coated
2o with that paint to be identified. In another example, tagging paper and ink
used in the
paper (or applied to the paper} can be used to establish the authenticity of
documents
and currency. In yet another example, many manufactured items prone to
counterfeiting or theft could benefit from tagging. Tagged threads in clothing
could
be used to encode information about the date, time, and place of manufacture.
Tagging the bulk materials used in the manufacture of such items as compact
disks,
computer disks, video tapes, audio tapes, electronic circuits, and other items
would be
useful in tracing and prosecuting theft and counterfeiting cases involving
these items.
In the present invention, the at least one taggant can be incorporated into
the
target material in any suitable form. Suitable forms include those which place
that
3o taggant in the target material with little to no damage (either chemical or
physical) to
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the target material. See, for example, the description in U.S. Patent Nos.
5,208,630,
5,760,394, and 6,030,657; the disclosures of which are incorporated herein by
reference. Other suitable forms include using materials containing the taggant
such
as particulates like microparticles; solvents; coatings and films; adhesives;
sprays; or a
5 hybrid or combination of these methods. In any of these forms, the at least
one
taggant can be incorporated by itself or with another agent.
The at least one taggant can be incorporated in the target material using any
suitable technique. Many existing tagging techniques involve the use of
microparticles containing the elements, or compounds or compositions of the
to elements, comprising the at least one taggant. Additionally, particles can
be
manufactured wherein smaller particles, or compounds or compositions of the
elements, containing the taggant. Such particles could be made of magnetic or
fluorescent materials to facilitate collection; refractory materials to
enhance particle
survival in an explosion; or chemically inert materials to enhance particle
survival in a
chemical reaction. Indeed, such particles could be made of non-durable,
soluble, or
reactive materials to enhance taggant dispersal in a fluid, aerosol, or powder
system.
When the target material is a liquid article like paints or inks, or
adhesives, or
has a liquid component, the at least one taggant can be incorporated as an
element or
compound in solution with the liquid. Thus, the at least one taggant can be
incorporated in elemental or compound form either in solution or suspension in
the
target material. The at least one taggant could also be dissolved or suspended
in a
solvent used in making the target material so that when that solvent
evaporates, the
residue left behind would contain the at least one taggant.
The taggant can be inserted into the target material of an article either
during
or after the article (or a part thereof) has been manufactured. The taggant
can be
manufactured as a component of the article or as part of a component of the
article.
During manufacture, the at least one taggant can also be incorporated into
another
material which comprises part of the target material. Indeed, the at least one
taggant
could also be an element or compound of the target material itself. The
taggant can be
3o incorporated into any location (including surfaces) of the article. Two
(and three)
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dimensional shapes and patterns of the at least one taggant can be constructed
using
any desired combination of types and numbers of taggants.
The at least one taggant could also be incorporated after manufacture of the
target material of the article. The taggant can be implanted into the article
or
deposited as a coating or film on the article. Additionally, the at least one
taggant
could be incorporated into the already formed target material as a dopant.
As a coating or film, the at least one taggant could be physically or
chemically
deposited by itself. The at least one taggant could also be incorporated as
one
ingredient (or contaminant) of another material (such as a mixture or
solution) which
1o forms a coating or film. In this aspect of the invention, the at least one
taggant can be
incorporated as an element or compound in solution (or suspension) with a
liquid
which is applied, such as by spraying, to the article. For example, the at
Least one
taggant could be dissolved or suspended in a solvent so that when that solvent
evaporates after being applied to the article, the residue left behind would
contain the
1 s at least one taggant.
As apparent from the description above, the present invention has the ability
to
easily tag small batches of target materials with a code unique to that batch.
This can
be done manually or in an automated system where each batch (or select
batches) of
the target material receives a different code. For example, 1000 (or 100)
compact
20 discs could be manufacture and each could be tagged with a code of a number
from 1
to 1000 (or 1 to 100). Economic and processing considerations, however, might
limit
the minimum size of each batch and the number of batches which could be
tagged.
As described above, any product or article as the target material can have at
least one extrinsic or intrinsic taggant located therein. For example, the
target material
25 of the present invention is carpeting and carpet products. Carpets
generally comprise
both a yarn and a backing. The yarn may be tufted or locked into the backing
in a
variety of ways, each affecting the texture and durability of the carpet. The
yarn may
comprise different types of materials, usually fibers; with differing types of
twists and
shapes to change the look of the carpet. The fibers can be made of nylon,
30 polypropylene, polyester, acrylic, wool, or a combination thereof. Carpet
components
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and their method of manufacture are known in the art. See, for example, U.S.
Patent
No. 6,030,685, the disclosure of which is incorporated herein by reference.
The at least one taggant of the present invention could be incorporated into
the
yarn or backing of the carpet in any suitable manner. For example, the at
least one
taggant could be incorporated into the fiber materials when they are made. In
another
example, the at least one taggant could be incorporated into a separate fiber
material
which could then be combined with a yarn (not containing any taggant) during
the
twisting process. In yet another example, the at least one taggant could be
incorporated into the backing as it is made.
The at least one taggant could also be incorporated as a coating or film on
the
yarn or backing of the carpet. For example, after manufacture of the yarn or
the
backing, but before they are assembled together, the at least taggant could be
coated
on the yarn and/or the backing. In another example, carpeting is often sprayed
with a
protective coating to make them easier to clean and the at least one taggant
could be
incorporated into that protective coating. In yet another example, carpeting
could be
dipped into a protective coating containing the at least one taggant and then
allowed to
dry, leaving the protective coating containing the taggant as a film on the
carpet.
Preferably, the film containing the taggant is chemically attached or bonded
to the
fiber and/or yarn of the carpet so that the film is not easily removed from
the carpet
when it is cleaned by steaming or washing.
The at least one taggant could be incorporated into carpet products with each
batch of carpet having its own code. The taggant could be introduced into the
yarn
fiber by injecting a solid (i.e., microparticle) or liquid (e.g., solvent)
containing the at
least one taggant into the bulk material of the fiber (i.e., nylon) before
that bulk
material is made into a fiber. When the nylon is made into fibers and then
twisted
into yarn, the yarn will contain the at least one taggant. Assuming two
taggants will
be used, a number of automated reservoirs having varying concentrations of the
two
taggants could be included in the assembly line process. Each reservoir would
contain
the distinctive mix of taggant concentrations, e.g., 5/5, 5/10, 5/15,...10/5,
10110,
10/15, ... 95185, 95/90, 95195. As the sample of the bulk material for the
yarn fiber
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passes through the assembly line, it would receive the taggants from the
desired
reservoir. Thus, each yarn manufactured from such material would receive a
unique
combination of taggants for its code.
After the at least one taggant is extrinsically or intrinsically present in
the
target material(s), the taggant(s) is detected to identify or verify the
target material
using XRF analysis as illustrated in Figure 1. Primary x-rays 40 are used to
excite a
sample of the target material 46, and the secondary x-rays 44 that are emitted
by the
sample are detected and analyzed.
As shown in Figure 3, the x-rays which are detected have various energies,
e.g., there is a broad band of scattered x-rays with energies less than and
greater than
those of the exciting atom. Figure 3 illustrates this spectrum for paper as
the target
material. Within this broad band, there are peaks due to the excitation of the
taggant(s)
in the sample. The ratio of the intensity of the radiation in any peak to the
intensity of
the background at the same energy (known as the peak-to-background ratio) is a
measure of the concentration of the element which has characteristic X-rays at
the
energy of that peak, e.g., the taggant.
In one aspect of the detection method of the present invention, at least one
target material believing to contain known concentrations of the taggant(s) of
interest
is selected. The XRF analysis is performed on that target material (or a
sample
thereof) using a detection device or apparatus containing an x-ray radiation
source
("source"), x-ray radiation detector ("detector"), support means, analyzer
means, and
calibration means.
One aspect of the detection device of the present invention is illustrated in
Figure 4a. In this Figure, the detection apparatus 25 has an ordinary x-ray
2s fluorescence spectrometer capable of detecting elements present in a
coating, package
or material. X-rays 29 from a source (e.g., either x-ray tube or radioactive
isotope) 24
impinge on a sample 11 which absorbs the radiation and emits x-rays 31 to an x-
ray
detector 21 and analyzer 23 capable of energy or wavelength discrimination.
This is
accomplished by using a commercially available x-ray spectrometer such as an
Edax
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DX-95 or a MAP-4 portable analyzer, commercially available from Edax Ine.,
Mahwah, New Jersey. Part of analyzer 23 includes a computerized system 27.
Another aspect of the detection apparatus of the present invention is
illustrated
in Figure 4b. In this Figure, the detection apparatus 25 has an instrument
housing 15
which contains the various components. Gamma rays or x-rays 30 from a source
(e.g., either x-ray tube or radioactive isotope) 20 are optionally focused by
aperture 10
to impinge on a sample 11. Sample 11 contains the at least one taggant which
absorbs
the radiation and emits x-rays 31 to an x-ray detector 21. Optionally,
analyzing means
can be incorporated within housing 15.
1o The present invention, however, is not limited to the detection apparatus
depicted in Figures 4a and 4b. Any suitable source, or plurality of sources,
known in
the art can be used as the source in the detection device of the present. See,
for
example, U.S. Patent Nos. 4,862,143, 4,045,676, and 6,005,915, the disclosures
of
which are incorporated herein by reference. During the XRF detection process,
the
source bombards the taggant with a high energy beam. The beam may be an
electron
beam or electromagnetic radiation such as X-rays or gamma rays. The source,
therefore, may be any material which emits such high energy beams. Typically,
these
have been x-ray emitting devices such as x-ray tubes or radioactive sources.
To target, the beam can be focused and directed properly by any suitable
means such as an orifice or an aperture. The configuration (size, length,
diameter...)
of the beam should be controlled, as known in the art, to obtain the desired
XRF
detection. The power (or energy level) of the source should also be
controlled, as
known in the art, to obtain the desired XRF detection.
The sources) can be shielded and emit radiation in a space limited by the
shape of the shield. Thus, the presence, configuration, and the material used
for
shielding the source should be controlled for consistent XRF detection. Any
suitable
material and configuration for that shield known in the art can be employed in
the
present invention. Preferably, any high-density materials used as the material
for the
shield, e.g, tungsten or brass.
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Any suitable detector, or plurality of detectors, known in the art can be used
as
the detector in the detection device of the present invention. See, for
example, U.S.
Patent Nos. 4,862,143, 4,045,676, and 6,005,915, the disclosures of which are
incorporated herein by reference. Any type of material capable of detecting
the
photons omitted by the taggant may be used. Silicon and CZT (cadmium-zinc-
telluride) detectors have been conventionally used, but others such as
proportional
counters, germanium detectors, or mercuric iodide crystals can be used.
Several aspects of the detector should be controlled to obtain the desired XRF
detection. First, the geometry between the detector and the target material
should be
to controlled. The XRF detection also depend on the presence, configuration,
and
material-such as tungsten and beryllium used as a window to allow x-rays
photons
to strike the detector. The age of the detector, voltage, humidity, variations
in
exposure, and temperature can also impact the XRF detection and, therefore,
these
conditions should be controlled.
The analyzer means sorts the radiation detected by the detector into one or
more energy bands and measures its intensity. Thus, any analyzer means
performing
this function could be used in the present invention. The analyzer means can
be a
multi-channel analyzer for measurements of the detected radiation in the
characteristic
band and any other bands necessary to compute the value of the characteristic
radiation as distinct from the scattered or background radiation. See, for
example,
U.S. Patent Nos. 4,862,143, 4,045,676, and 6,005,915, the disclosures of which
are
incorporated herein by reference.
The XRF also depends on the resolution of the x-rays. Background and other
noise must be filtered from the x-rays for proper measurement, e.g., the
signals must
2s be separated into the proper number of channels and excess noise removed.
The
resolution can be improved by cooling the detector using a thermoelectric
cooler-
such as a nitrogen or a pettier cooler-andJor by filtering. Another way to
improve
this resolution is to use pre-amplifiers.
The support means supports the source and detector in predetermined positions
relatively to a sample of the target material to be irradiated. Thus, any
support means
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performing this function could be used in the present invention. In one
example, the
support means comprises two housings, where the source and detector are
mounted in
a first housing which is connected by a flexible cable to a second housing in
which the
analyzer means is positioned as illustrated in Figure 4a. If desired, the
first housing
may then be adapted to be hand-held. In another example, the source and
detector as
well as the other components of the detection device are mounted in a single
housing
as illustrated in Figure 4b.
The calibration means are used to calibrate the detection apparatus, thus
insuring accuracy of the XRF analysis. In this calibration, the various
parameters
1o which could be modified and effect the measurement are isolated and
calibrated. For
example, the geometrical conditions or arrangements can be isolated and
calibrated.
In another example, the material matrix are isolated and calibrated.
Preferably,
internal (in situ) calibration during detection is employed as the calibration
means in
the present invention. Components, such as tungsten shielding, are already
present to
internally calibrate during the XRF analysis. Other methods, such as
fluorescence
peak or Compton backscattering, could be used for internal calibration in the
present
invention.
Analyzer means, which includes a computerized system 27, is coupled to,
receives, and processes the output signals produced by detector 21. The energy
range
of interest, which includes the energy levels of the secondary x-ray photons
44
emitted by the taggant(s), is divided into several energy subranges.
Computerized
system 27 maintains counts of the number of X-ray photons detected within each
subrange using specific software programs, such as those to analyze the
detection and
x-ray interaction and to analyze backscatter data. After the desired exposure
time,
computerized system 27 with display menus stops receiving and processing
output
signals and produces a graph of the counts associated with each subrange.
Figure 5 is a representative graph of the counts associated with each
subrange.
This graph is essentially a histogram representing the frequency distribution
of the
energy levels Ei, E2, and E3 of the detected x-ray photons. Peaks in the
frequency
3o distribution (i.e., relatively high numbers of counts) occur at energy
levels of scattered
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primary x-ray photons as well as the secondary x-ray photons from the
taggant(s). A
primary x-ray photon incident upon a target material may be absorbed or
scattered.
The desired secondary x-ray photons are emitted only when the primary x-ray
photons
are absorbed. The scattered primary x-ray photons which reach the detector of
the
system create an unwanted background intensity level. Accordingly, the
sensitivity of
XRF analysis is dependent on the background intensity level, and the
sensitivity of
XRF detection may be improved by reducing the amount of scattered primary x-
ray
photons reaching the detector. The peak occurring at energy levels of
scattered
primary x-ray photons is basically ignored, while the other peaks-those
occurring at
to E1, E2, and E3-are used to identify the at least one taggant present in the
target
material.
Besides the parameters described above, at least two other parameters must be
controlled during the process of XRF detection. First, the media (such as air)
through
which the gamma rays (and x-rays) must travel also impacts the XRF. Therefore,
the
' different types of media must be considered when performing the XRF
analysis.
Second, the methods used to interpret and analyze the x-rays depend, in large
part, on
the algorithms and software used. Thus, methods must be adopted to employ
software
and algorithms that will consistently perform the XRF detection.
These two parameters, plus those described above, must be carefully
accounted for and controlled to obtain accurate measurements. In one aspect of
the
intention, these parameters could be varied and controlled to another provide
a distinct
code. For example, using a specific source and a specific detector with a
specific
measuring geometry and a specific algorithm could provide one distinct code.
Changing the source, detector, geometry, or algorithm could provide a whole
new set
of distinct codes.
Figure 6 illustrates a preferred apparatus and detection method according to
the present invention. in this Figure, detection apparatus 25 is capable of
detecting at
least one taggant present in target material 10, such as a sample of carpet.
Detection
apparatus 25 is a portable device which can be small enough to be hand-held.
Detection apparatus 25 contains all the components discussed above (i.e.,
source,
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detector, analyzer means, and calibration means) in a single housing, thus
allowing
the portability and smaller size.
The present invention is not limited to any specific XRF analysis. Any type of
XRF, such as total reflection x-ray fluorescence {TXRF), can be employed in
the
present invention.
In one aspect of the invention, the apparatus and method used identify an
article once it has been tagged. The ability to invisibly tag an article and
read the tag,
especially through a non line of sight method, would provide an invaluable
asset in
any industry which authenticates, verifies, tracks, labels, or distributes
goods of any
l0 kind. Indeed, having an invisible taggant(s) could further prevent copying
and
counterfeiting of goods. In another aspect of the invention, the apparatus and
method
of the present invention could be used for these same purposes, but for those
products
which have the desired taggant already located therein. Thus, the present
inventions
could analyze liquid flows for contaminant particles or pinpoint via 3-D
analysis the
exact location of a contaminants) in an article.
The following non-limiting examples illustrate the present invention.
Example 1
A sample of carpet was purchased and cut to a size of 4 inches by 4 inches. 1
liter of a commercially-available protective liquid was also purchased.
A taggant solution was then prepared by mixing 1 liter of distilled water with
162.7 grams of yttrium oxide until a homogenous mixture was obtained. The
concentration of the taggant in the taggant solution was 14 wt%.
0.054 milliliters of the taggant solution and 4.5 milliliters of protective
liquid
were then mixed together until a homogenous mixture of a "tagged" protective
liquid
was obtained. The concentration of the yttrium oxide in the tagged protective
liquid
was 0.014 wt%. The tagged protective liquid was then diluted with 1 liter of
distilled
water.
The tagged protective liquid was then coated onto the carpet sample by
soaking. The carpet sample was wrung out and dried until the liquid portion of
the
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tagged protective liquid was evaporated, leaving the yttrium oxide as a
component of
a film on the yarn and backing of the carpet. The concentration of the yttrium
oxide
in the carpet was about 8 ppm.
Example 2
The tagged carpet sample from Example 1 was analyzed for the presence of
the taggant. A portable, hand-held detection apparatus similar to that
illustrated in
Figure 6 was used to detect the presence of the taggant using XRF analysis.
The detection apparatus contained several components. A trigger actuated
tungsten shutter block containing an americium 241 gamma ray point source and
a
1o silicon pin x-ray detector were located within the front of the instrument.
Circuit
boards, necessary for acquiring and processing the data from the detector were
located
within the rest of the housing. The instrument had a red and a green light to
indicate
whether the carpet was tagged or not and a read out to inform the user that
the carpet
was tagged or not. A keypad on the top of the instrument allowed the user to
turn the
electronics of the instrument on and off, while a key operated lock on the
side of the
instrument kept the user from inadvertently opening the shutter block,
exposing the
radioactive source.
This detection apparatus was used for an XRF analysis on the tagged sample
of carpet. The result of the XRF analysis for the tagged sample is reported in
Figure
7. The peaks indicating the presence of the yttrium oxide taggant in Figure 7
are
labeled.
Having described the preferred aspects of the present invention, it is
understood that the invention defined by the appended claims is not to be
limited by
particular details set forth in the above description, as many apparent
variations
thereof are possible without departing from the spirit or scope thereof.
