WO2011130804A1

WO2011130804A1 - System and method for establishing the integrity of items using laser induced breakdown spectroscopy

Info

Publication number: WO2011130804A1
Application number: PCT/AU2011/000471
Authority: WO
Inventors: Gerhard Frederick Swiegers; John Kraft; Gregory Peter Twemlow
Original assignee: Datatrace Dna Pty Limited
Priority date: 2010-04-23
Filing date: 2011-04-21
Publication date: 2011-10-27

Abstract

A method and system for establishing integrity of an item is provided. The method comprises the steps of: performing laser-induced breakdown spectroscopy on an item to obtain a first representative spectrum (510); comparing the first representative spectrum to a plurality of stored laser-induced breakdown spectra (520); and establishing integrity of the item based on the comparison (530). The plurality of stored laser-induced breakdown spectra preferably comprise a spectrum representative of an item comprising at least one predetermined element and a spectrum representative of an item that does not comprise the at least one predetermined element.

Description

System and method for establishing the integrity of items using laser induced breakdown spectroscopy

TECHNICAL FIELD

The present disclosure relates to a system and method for establishing the integrity of items, including the identification, tracking, and/or verification of such items, by using spark or breakdown spectroscopy to detect characteristic elements or mixtures of characteristic elements associated with the items. The elements may be naturally present within the items, or may be deliberately introduced into or onto the items, or may be contaminants in the items.

BACKGROUND

The counterfeiting of banknotes and other financial transaction documents as well as visas, passports, ID cards, and other official Government security documents has long been an active area of criminal activity. The security of personal identity documents, such as drivers' licenses and credit cards, is now assuming much greater relative importance because of the role counterfeit documents of this type play in organized money laundering activities and terrorist incidents - over 30% of which involve the use of false identities according to a 2004 UK Home Office report.

The counterfeiting of software, pharmaceuticals and brand name products is also a significantly growing area of organised crime. According to the International Chamber of Commerce Counterfeiting Intelligence Bureau, over 5% of world trade involves counterfeit products. The cost of this illegal activity amounts to more than US$350 billion annually and is growing.

To counteract this rapidly evolving threat, national and international organisations (e.g., governments and major brand owners) have turned to new technologies which enable establishment of integrity of items. Such establishment may involve: identifying (i.e., verifying the origin of), authenticating (i.e., verifying the authenticity of), and tracking the movements of items (i.e., following transportation of the items in distribution chains). However, the need for identification, tracking, and verification is not limited to the deterrence of counterfeiting and crime. There is also a growing need to follow the movements of materials used in manufacturing and the products that result therefrom. There is also interest in determining that items, such as food-grade items, are what they are claimed to be and testing such items for safety in real-time.

For example, materials used in industrial production processes need to be tracked for material control, inventory control (or stock control), process control, logistics control, quality control and pollution control. These measures may be used to ensure that the materials Used in production processes are available in the correct place, at the correct time, in the correct quantities, and are of the correct quality. Increasingly, materials are required to be properly accounted for in all aspects of manufacturing, from their acquisition and processing, to their use and disposal.

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It is often difficult to track industrial process materials. Such materials are typically standardised and are therefore indifferentiable, substitutable, interchangeable, and may be batch-processed in essentially identical form. The materials may be available in bulk and/or from a variety of sources. Examples of such materials include primary commodities, such as agricultural and mineral products, as well as processed commodities such as manufacturing materials, building materials and industrial chemicals. In practice, the low inherent visible identity of these materials often defeats attempts to accurately identify, verify, and track them. That is, their low inherent visible identity defeats attempts to establish their integrity.

In relation to verifying that items are what they are claimed to be, governments and consumers are becoming increasingly concerned about the security of the food supply chain. In recent years, national food substitution scandals have arisen and have resulted in serious damage to health and even the death of consumers. For example, consumers of high quality foods such as rare wines are becoming increasingly sceptical about whether they are actually buying the genuine product and have no simple way to determining the integrity of the item/s they are purchasing. Purchasers of fish and seafood products have concerns regarding possible contamination of such products with dangerous heavy metals. Similarly, these purchasers have no easy way of determining whether such products are safe to eat. In short, the integrity of products or items and the accurate labelling thereof has become an urgent matter for everyone involved in the edible product supply chain, from producer to consumer.

Public and private sector demand for unambiguous integrity of products and items (including industrial process and other materials) and the establishment thereof by way of identification, tracking, and/or verification, has been heightened by concerns about terrorist misuse of explosives and agrochemicals, quality and contamination of food/medicine/fuel/feed, illicit substitution of inferior materials, liability for defective products and built structures, price and availability of commodities, and pollution of the environment. Numerous methods have been proposed for the identification, tracking, and/or verification of items. A common approach for items such as banknotes, credit cards, and the like is to deliberately incorporate so-called 'security devices' in or upon the items. The security devices may be designed to be covert (and therefore difficult to locate without suitable detection means) or overt (and therefore comprised of materials that are difficult to forge or copy). Overt security devices are perhaps best exemplified by holograms that are widely used on high- value consumer goods such as CD's and DVD's, as well as certain banknotes, driver's licences, pharmaceuticals, and the like. A wide range of overt security devices are described in the book "Optical Document Security", edited by Rudolf L. van Renesse, Artech House Publishing, 1994. Numerous covert security devices are also available. For example, devices containing microscopically small visual markings may be incorporated within or attached to items of value. The markings can only be observed using strong magnification.

Despite the variety of techniques that are currently available to identify, verify, and track items to thereby establish their integrity, there is a need for alternative and better techniques. SUMMARY

An aspect of the present invention provides a method for establishing integrity of an item. The method comprises the steps of: performing laser-induced breakdown spectroscopy on an item to obtain a first representative spectrum; comparing the first representative spectrum to a plurality of stored laser-induced breakdown spectra; and establishing integrity of the item based on the comparison.

The plurality of stored laser-induced breakdown spectra preferably comprise a spectrum representative of an item comprising at least one predetermined element and a spectrum representative of an item that does not comprise the at least one predetermined element.

Another aspect of the present invention provides a method for establishing integrity of an item. The method comprises the steps of: performing laser-induced breakdown spectroscopy on a first item to obtain a first representative spectrum; performing laser-induced breakdown spectroscopy on a second item to obtain a second representative spectrum, wherein the second item is substantially identical to the first item except that the second item comprises at least one element not present in or on the first item; performing laser-induced breakdown spectroscopy on a sample item to obtain a third representative spectrum; processing the first, second and third representative spectra; and establishing integrity of the sample item based on whether the third representative spectrum correlates with the first representative spectrum or the second representative spectrum. The. at least one element may comprise a naturally occuring element within the second item and/or the method may comprise the further step of introducing the at least one chemical element into or onto the second item.

An alternative to the deliberate incorporation of security devices into or upon items is to find an inherent, natural distinguishing feature of an item, whose presence can be used to identify, verify, or track the item to thereby establish its integrity. For example, the paper used in. certain security documents is cotton-based and does not make use of wood pulp. As such, these documents display certain inherent, native physical characteristics associated with cotton but not with wood. These characteristics can be used to verify, to a particular level of certainty, the origin of the document. Similarly, unique trace elements present in foods such as rare wines can potentially be used to verify their authenticity, while the detection of trace amounts of dangerous contaminants can be used to identify safety hazards in foods, such as seafoods.

In general, finding a native characteristic of an item that is genuinely unique offers the most attractive possible 'security device'. There is then no need to deliberately include or attach a separate security device. Moreover, if the inherent characteristic is difficult to reproduce, it offers a relatively higher level of confidence to the verification process.

An alternative approach is to deliberately introduce a security device into or onto the item or combine a security device which is deliberately introduced into or onto teh item with a distinguishing native characteristic of the item. Confidence in the verification process may then established or increased by the combination of two techniques, as opposed to only a single technique.

BRIEF DESCRIPTION OF THE DRAWINGS

A small number of embodiments are described hereinafter by way of non-limiting examples and with reference to the accompanying drawings in which:

Figure 1 shows a laser-induced breakdown spectrum of a first item;

Figure 2 shows a laser-induced breakdown spectrum of a second item that contains a fixed, trace quantity of gold (Au);

Figure 3 shows a laser-induced breakdown spectrum of a third item that also contains a fixed, trace quantity of gold (Au), however, this quantity is a different quantity of gold to that contained in the second item;

Figure 4 shows two single emission lines belonging to iron (Fe), obtained using laser-induced breakdown spectroscopy on two separate items. Curve 'A' shows a line emission taken from a first item, whereas Curve 'B' shows a line emission taken from a second item that is visually indistinguishable from the first item;

Figure 5 shows a flow chart of a method. for establishing integrity of an item using laser-induced breakdown spectroscopy (LIBS) in accordance with an embodiment of the present invention; and

Figure 6 shows a flow chart of a method for establishing integrity of an item using laser-induced breakdown spectroscopy (LIBS) in accordance with another embodiment of the present invention.

OVERVIEW

The present disclosure includes embodiments of a system and method for establishing the integrity of items by identifying, tracking, verifying, or performing related functions upon the items. Single or multiple spark spectroscopy is used to determine the presence of:

• one or more distinctive chemical elements present in or upon the item;

· one or more elements present in distinctive quantities or ratios relative to each other, in or upon the item; and/or

• one or more distinctive elements present in distinctive quantities or ratios relative to each other, in or upon the item. The elements in question are present in or upon the item as a consequence of:

• natural or inherent presence in or on the item;

• deliberate and planned inclusion as a security device in or on the item; and/or

• contamination of the item, either deliberately or inadvertently. The disclosed embodiments may be used for identification, tracking, verification, and other functions that aim to establish the integrity of items, with the intention of deterring counterfeiting and crime, including false warranty and liability claims, as well as for purposes of material control, inventory control (stock control), process control, logistics control, quality control, pollution control, disposal control, and determining the accuracy of labelling of the item, and safety of the item.

The chemical elements in or upon the item are generally present in trace quantities (i.e., in the proportions of parts-per-million, or less). However, particularly in the case of contamination, the elements may be present in larger proportions.

The chemical elements in or upon the item may include one or more elements that are rare, scarce, or uncommon. The rare, scarce, or uncommon quality of the elements may be used to determine with a high degree of confidence whether two or more products or items are related to each other and/or whether the products are correctly labelled and safe. For example, the safety of seafood may be verified by the absence or very low presence of common contaminant elements such as mercury and arsenic, which are normally not present in food, or are normally present only at very low levels.

Multiple chemical elements in or upon the item may be present in fixed ratios and quantities to each other, such that the spark spectroscopy yields a spectroscopic profile which is highly distinctive, rare, or uncommon. The ratios and quantities may then be used to determine whether two or more products or items are related to each other, including whether they are related to each other by dilution, adulteration, or by other similar modification. The chemical elements, particularly in the case of contamination, may be present in non-distinctive combinations. The spark or breakdown spectroscopy is preferably carried out Using a laser- induced breakdown spectrometer, which provides real-time, essentially instantaneous analyses. The laser-induced breakdown spectrometer performs single- or multiple-shot measurements. In the case where multiple shots are used, the multiple shots may be fired in a co-linear or "cross-fire" arrangement, where the purpose of at least one of the shots is one of the following: (i) to clear ambient dust or debris; (ii) to ablate away the surface of the item and sample materials from under the surface; (iii) to advantageously steer or tailor a plume from an earlier shot; or (iv) to re-energize the plume from an earlier shot. The laser-induced breakdown spectrometer may use microwave energy to maintain and energize the plasma that derives from a laser shot. The laser-induced breakdown spectrometer may be configured to yield a microscopic ablation crater, which is defined as being less than 120 micrometers in diameter; this is below the size that can be perceived by the human eye. That is, the laser-induced breakdown spectrometer may be configured to perform microscopic laser-induced breakdown spectroscopy.

The spark or breakdown spectroscopy may be carried out using a portable and mobile facility or system deployed as a fee-for-service model to enable any part of a supply chain to establish the integrity of a material, mineral, foodstuff, and the like by identifying, verifying, and/or tracking the item or product, or performing any other function aimed at establishing the integrity of the item or product. The system may further include computer ^"software executable by an associated computer system, which may be portable, or by an attached computer chip to track, identify or verify items. In this way the system may be automated to track, identify or verify items and thereby establish their integrity.

In some embodiments, data from the spark or breakdown spectroscopy is subjected to automated discriminant generation (i.e., "machine-learning") techniques for data analysis, for example, the use of neural networks or equivalent statistical methods: The ability to program a "machine-learning" algorithm into the data analysis protocol employed is particularly advantageous in cases where there are substantial variations in the behaviour of spatially proximate samples under laser ablation, such as can occur in items having distinctive natural or inherent mixtures of elements (e_^g., certain mineral formations or agricultural products).

Where trace amounts of the chemical elements are physically and/or chemically incorporated into or upon an item, this will typically, but not exclusively, be in quantities of more than 1 part per billion and less than 10% by mass, this being dependent on the item in question. The trace amounts of the chemical elements may include a plurality of chemical elements having distinctive and mutually different emission wavelengths. The presence or absence of the mutually different emission wavelengths may be used to uniquely identify the item.

In some embodiments, the spark or breakdown spectroscopy analyses may be performed at a distance from the target item using a stand-off technique. The stand-off technique can be used to perform a raster-scan of a location of interest. The x,y,z information from such a raster scan can be used to create maps of structure and small and large scale homogeneity.

In some embodiments, the precise location of each spatial position of each spark spectroscopy analysis may be automatically logged, without the need for human intervention, using GPS (Global Position Satellite technology), Differentia] GPS, triangulated radio- or other waves (e.g., using a IR Wii system), laser-positioning, or other automated positional techniques, to thereby create an accurate and an absolute record of each time the device is used for establishing the integrity of items, including the identification, tracking, or verification of items.

In some embodiments, the spark or breakdown spectroscopy can be combined with other analytical techniques to improve the confidence of the tracking, verification, or identification, including but not limited to: „

(a) laser-induced fluorescence;

(b) laser-induced Raman spectrometry to determine structure, including the organics present;

(c) the use of polarization information to determine crystal structure; and

(d) the use of hyperspectral imaging to capture raster or other scanning data and/or also as a means to measure inhomogeneity.

In some embodiments, spark or breakdown spectroscopy may be combined with other imaging and light-capture techniques to improve the confidence of the verification, tracking or identification. Examples of imaging and light-capture devices that can be used in such embodiments include:

(a) miniature spectrometers;

(b) solid state custom spectrometers tuned to specific emission lines;

(c) solid-state spectrometer devices coated with patterned filters to exclude all wavelengths other than those of interest. Such devices may involve an imaging chip, such as a Charge-Coupled Device (CCD) or similar chip, overlaid with a patterned filter in such a manner that each pixel on the chip is limited to receiving light which has been filtered to transmit only a particular wavelength or narrow range of wavelengths, and where the transmitted wavelength(s) differ from pixel to pixel; or

(d) Hyperspectral imaging devices, including modified digital cameras capable of measuring not only the presence and intensity of spectral lines of interest, but also their spatial position within the field of view. Such devices can, for example, be used to rapidly analyse ores and or waste where the ore and waste is inherently inhomogeneous. Such techniques can vastly increase the spatial sampling frequency of the method and/or the rate at which a very high spatial sampling frequency can be attained.

DETAILED DESCRIPTION

Embodiments described herein include a method and system for real-time analysis using spark or breakdown spectroscopy of elemental compositions in or upon items to perform tracking, verification, authentication, and/or other similar functions related to establishing the integrity of the items. The embodiments described herein preferably achieve the above functionality by detecting characteristic trace elements or combinations of characteristic trace elements, which are naturally present within the items, which have been deliberately introduced into, or onto the items in a designed way, or which are contaminants that should not be present in or on the items.

Embodiments described herein may be useful for the deterrence of counterfeiting and crime, including false warranty and liability claims, as well as for purposes of material control, inventory control (or stock control), process control, logistics control, quality control, pollution control, disposal control, and determining the accuracy of the labelling on the item, and the safety of the item.

EXAMPLE 1 : Establishing the integrity of an item by precise measurement of the trace element spectral fingerprint present.

Figure 1 shows representative laser-induced breakdown spectra 110, 120 of two items which are visually indistinguishable to the naked eye. The spectrum 110 relating to the first item is in the foreground and is black in colour, whereas the spectrum 120 relating to the second item is in the background and is grey in colour. A comparison of the laser-induced breakdown spectral fingerprint of the first item (foreground spectrum) and of the second item (background spectrum) highlights significant differences. The differences unambiguously indicate that the first and second items are different and are not of the same origin. These differences can be used for identification, tracking, verification, and other purposes that aim to establish the integrity of the items with the intention of deterrence of counterfeiting and crime, including false warranty and liability claims, as well as for purposes of material control, inventory control (or stock control), process control, logistics control, quality control, pollution control, disposal control, and determining the accuracy of labelling of the item, and safety of the item.

As can be seen from Figure 1, a characteristic collection of elements exists in the spectrum 120 relating to the second item and these yield a highly distinctive spectral fingerprint arising from the application of spark spectroscopy. This fingerprint may be used to establish the integrity of the item, that is, to unambiguously track or to establish the origin, identity, authenticity, and/or other characteristics of the second item. Alternatively, the fingerprint may be used to verify the lack of integrity, lack of authenticity or the incorrect origin or identity of the first item.

The laser-induced breakdown spectrum of an item may be exceedingly complex, so that differences in the spectra of two different items are not readily apparent to the human eye, or they may appear ambiguous to the human eye. That is, while the spectra shown in Figure 1 are clearly and unequivocally different to the human eye, this may not always be the case. Peaks that are expected may not be present, whereas other new and unexplained peaks may appear. This may arise because the laser spark technique, being a high energy process, can change what is being sampled during the actual sampling process. That is, the spectrum obtained may be changed during its measurement. Such cases can be highly confusing and it may not be possible to rationally distinguish one item from another based on a visual analysis of their relative spectra. In such situations, it may be necessary to use , mathematical correlation techniques or machine-learning techniques to distinguish the spectra of two items and show that they are different. An application of such techniques is described in the particle board embodiment described hereinafter.

EXAMPLE 2: Establishing the integrity of an item by precise measurement of the spectral emission of a single, unusual or scarce trace element present.

Figure 2 shows representative laser-induced breakdown spectra 210, 220 of two items which are visually indistinguishable to the naked eye. The spectrum 210 of the first item contains a fixed, trace quantity of gold (Au). The spectrum 220 of the second item does not contain the same trace quantity of gold (Au) as the first item.

A comparison of the laser-induced breakdown spectral fingerprint of the first item (black foreground spectrum) and of the second item (grey background spectrum) shows a substantial difference in the quantity of trace gold (Au) present in the items. The first item contains very substantially more trace gold (Au) than the second item. These differences indicate, unambiguously, that the first and second items are different and do not have the same origin. The differences can be used for identification, tracking, verification, and other purposes with the aim of establishing the integrity of the items with the intention of deterrence of counterfeiting and crime, including false warranty and liability claims, as well as for the purposes of material control, inventory control (or stock control), process control, logistics control, quality control, pollution control, disposal control, and determining the accuracy of labelling of the item, and safety of the item.

The laser-induced breakdown spectrum of an item may be exceedingly complex, so that differences in the spectra of two different items are not readily apparent to the human eye, or they may appear ambiguous to the human eye. That is, while the spectra shown in Figure 2 are clearly and unequivocally different to the human eye, this may not always be the case. Peaks that are expected may not be present, whereas other new and unexplained peaks may appear. This may arise because the laser spark technique, being a high energy process, can change what is being sampled during the actual sampling process. That is, the spectrum obtained may be changed during its measurement. Such cases can be highly confusing and it may not be possible to rationally distinguish one item from another based on a visual analysis of their relative spectra. In such situations, it may be necessary to use mathematical correlation techniques or machine-learning techniques to distinguish the spectra of two items and show that they are different. An application of such techniques is described in the particle board embodiment described hereinafter.

EXAMPLE 3: Establishing the integrity of an item by precise measurement of the spectral emission of a single unusual or scarce trace element present to determine dilution, adulteration, or a similar modification. Figure 3 shows a representative laser-induced breakdown spectrum 310 of a third item which is visually indistinguishable to the naked eye from the first and second items whose spectra 210, 220 are shown in Figure 2. The third item also contains a fixed, trace quantity of gold (Au), but this is once again a different quantity of gold to that in the first and second items represented in Figure 2. However, the laser-induced breakdown spectral fingerprint 310 of the third item shows that it contains a significantly different quantity of trace gold (Au) (as indicated by the height of the gold peak at 460.75 nm in Figure 3) compared to the items whose spectra 210, 220 are shown in Figure 2. Thus, the item having the spectrum 310 has a different origin and identity to the first and second items having the spectra 210, 220, respectively. This difference can be used for identification, tracking, verification, and other purposes that aim to establish the integrity of the items with the intention of deterrence of counterfeiting and crime, including false warranty and liability claims, as well as for the purposes of material control, inventory control (or stock control), process control, logistics control, quality control, pollution control, disposal control, and determining the accuracy of labelling of the item, and safety of the item.

Moreover, if the first item (corresponding to spectrum 210 of Figure 2) originates from an adulteration or dilution of the third item corresponding to spectrum 310 of Figure 3), the approximate extent of that adulteration or dilution may be determined from a comparison of the absolute quantities of gold present in the first and third items (i.e., a comparison of the difference in the gold peaks in the respective spectra).

EXAMPLE 4: Establishing the integrity of an item by precise measurement of the spectral emission of multiple trace elements present to determine dilution, adulteration, or a similar modification.

Figure 4 shows representative laser-induced breakdown spectra 410, 430 of the spectral line originating in iron (Fe) for the first and third items (corresponding to the spectra 210 and 310 of Figures 2 and 3, respectively). These items are visually indistinguishable to the naked eye. However, as described in relation to the spectrum 310 of Figure 3, a comparison of the laser-induced breakdown spectral fingerprints show that they contain different absolute quantities of trace gold (Au) and that they therefore have a different origin. This was confirmed by examination of the laser- induced breakdown spectral lines 410, 430 belonging to iron (Fe) in each of the first and third items. The one item contained a significantly different trace quantity of iron relative to the other item. The fact that iron was present in each of the items raised the' possibility that one may have been an adulteration of the other. However, the spectral data indicates that the relative proportion of iron in the two items is completely different to the relative proportion of gold in the two items. If the one item was an adulteration of the other, then this could not be the case. Thus, the two items have different and unrelated origins.

The difference in the trace metals (laser-induced breakdown spectra) consequently enables conclusions to be drawn regarding the origin, identity, distribution chain, and authenticity of the items for purposes of deterrence of counterfeiting and crime, including false warranty and liability claims, as well as for material control, inventory control (or stock control), process control, logistics control, quality control, pollution control, disposal control, and determining the accuracy of labelling of the item, and safety of the item.

EXAMPLE 5: Establishing the integrity of food items by precise measurement of the spectral emission of multiple trace elements present to confirm food safety .

A consumer suspects that a rare wine they have purchased is not what they have paid for. A laser-induced breakdown spectrum of the rare wine displays a spectral fingerprint that does not match the registered and previously collected spectral fingerprint of the authentic rare wine. In this way, the lack of integrity of the purchased wine is established. An analysis of the elemental content of dangerous heavy-metal contaminants such as arsenic and lead confirm that the purchased wine is nevertheless safe in this respect - elements associated with dangerous poisons are not present.

EXAMPLE 6: Using correlation techniques or machine-learning techniques to distinguish doped and undoped particle board samples.

Particle board is widel used as a decorative or functional material in furniture, cupboards, bookcases, desks, benchtops, and in other applications. Particle board is typically laminated with a decorative sheeting material comprising resin-infused paper. The sheeting material typically comprises at least two layers: a structural layer and a decorative layer. The decorative layer is typically called the 'Deco' layer and is usually finished with decorative prints, colours, surface treatments and the like. The structural layer is called the 'Kraft ' layer after the type of cardboard used.

In order to demonstrate distinguishing of "authorized" and "non-authorized" particle board and thereby identify the manufacturer of the particle board and establish the integrity of the materials, a series of particle board samples were manufactured as "doped" and "control" samples. The "doped" samples contained 1000 ppm of a common metal sulphate in the resin in the Kraft layer. The "control" samples were not doped in this manner.

The samples, both doped and undoped (control), were then analysed using a standard' Laser-Induced Breakdown Spectrometer (LIBS) system supplied by Ocean Optics of 830 Douglas Avenue, Florida 34698, United States of America.

For the purposes of this experiment, several samples of particle board marked as "doped" or "undoped" were provided by a particle board manufacturer. Additionally, a range of numbered samples was provided without indication as to whether they were doped or undoped. The numbered samples comprised a diverse series of other samples, some of which had been manufactured to contain the dopant and others of which contained no dopant. The manufacturer was aware of which of the numbered samples were doped, but the LIBS system operator was given no indication as to which of the numbered samples were doped and which were undoped. The LIBS system operator was asked to distinguish the doped from the undoped materials in the numbered samples.

To do this, the LIBS system operator cut the doped samples, undoped controls, and the numbered samples to expose the Kraft layer. No other sample preparation was carried out. During the LIBS analysis, the samples were suspended under the laser using a pedestal to ensure that LIBS data could only be collected from the high pressure laminate or free air. The composition of the air was known to be completely free of the dopant elements.

High pressure laminate has a stratified nature. The dopants were introduced into specific (epoxy) layers within the raw high pressure laminate during early stages of ^• manufacture. It was anticipated however, that during later manufacturing processes, the dopants could potentially migrate and or diffuse from their original location, thus making location and/or collection of the dopant signal and/or determining its presence or absence, potentially complex. It was therefore decided to generate a library consisting of multiple correlation models for both the doped and the undoped control samples. The library would furthermore contain models for each of the levels within the high pressure laminate doped samples and the undoped control samples. Each element of the library for both the doped and the undoped control samples would therefore represent data collected from specific strata and or data integrated over a number of strata.

The LIBS system:

· samples an exceedingly small volume (a layer) of material;

• ablates away material with each shot thereby exposing fresh material; and

• when used as a series of shots in the same (x,y) location, has the effect of drilling a hole through the material

Accordingly, spectra were collected from the exposed Kraft layer by firing 1 , 5, 15, or 30 laser shots at the surface. The surface moved lower with each shot and it was found that 30 shots was more than sufficient to make a hole right through the high pressure laminate and generate a plasma in the free air gap underneath.

In experiments comprising more than one shot, a spectrum was collected for each shot and the data thus obtained was stacked (averaged) into a single spectrum. Each stacked set of data was then named according to its sample type, sample number, and shot composition, and saved as a single spectrum in a correlation library within the LIBS software package supplied by Ocean Optics.

The LIBS spectra obtained for all of the doped, undoped, and numbered samples, were exceedingly complex - far too complex for simple comparisons using the human eye. Even at the level of comparing single peaks, the data was not clear-cut and unequivocal.

Mathematical cross-correlations were therefore performed between the various sets of stored data. That is, a mathematical comparison was made, using the Ocean Optics software, of how well one set of spectral data matched the other sets of spectral data. A perfect correlation, in which the two spectra matched perfectly, yielded a correlation factor of 1. A correlation factor of 0 corresponded, in theory at least, to a complete and total mismatch between the two spectra. In practice, experiments show that a correlation factor of ca. 0.85 - 1.00 indicates a good match, while a correlation of 0.60 - 0.85 indicates a poor match.

When the spectra collected from the numbered samples were compared with each other, they were found to reside in two distinct groups, one of which correlated closely with the spectra associated with the doped samples, and the other of which correlated closely with the spectra associated with the undoped control samples.

That is, the spectra from the numbered samples were found to either:

(1) correlate well with the spectra from the doped samples (0.83 - 0.92 correlation factor range) and poorly to the undoped samples (0.72 - 0.78 correlation factor range), or

(2) correlate well with the undoped control samples. (0.90 - 0.98 correlation factor range), and poorly with the doped samples (0.67 - 0.81 correlation factor range).

The greater the number of laser shots used, the better the correlation was found to be. Thus, in the case of 30 shots, the good correlations fell within the range 0.92 - 0.98, while the poor correlations fell within the range 0.78 - 0.82. That is, the groupings became significantly narrower and more distinctive as more laser shots were used in the analysis. Based on these correlations, the numbered samples were correctly identified as either doped or undoped.

To check the accuracy of this technique, the LIBS prediction was then compared to the actual situation for each of the numbered samples. This showed that the LIBS-based correlation techniques yielded 100% accuracy for all samples subjected to 5 laser shots or more. That is, the correlation techniques produced no errors whatsoever over a large multiplicity of numbered samples. On each occasion a single laser shot for was used for sampling, the technique yielded 93% accuracy.

The foregoing observations and results demonstrate that it is possible to distinguish materials with extremely complex LIBS spectra from each other. To further improve upon this technique, a ranking system was devised according to the number of positive correlations obtained for a particular sample that was checked multiple times at different locations. The result was that the more often a positive correlation was obtained, the greater the confidence there was in the outcome. Various mathematical functions which combine these "confidence rankings" with the correlation factors may be created to still further improve upon the above technique. Furthermore, the entire sampling process described above, including the correlations and rankings, may be automated for accurate, high-throughput analysis.

EXAMPLE 7: Using correlation techniques or machine-learning techniques to establish the integrity of wood preservative solutions.

Freshly-cut lumber must typically be treated with liquid wood preservatives before use. The process involves placing the lumber in a vacuum chamber and, after evacuating the chamber, back-filling the chamber with a wood preservative solution that then penetrates the pores of the wood. This process is typically carried out several times to ensure thorough treatment. If the wood is not thoroughly treated, then it will have a reduced lifetime in an external environment. A key problem for manufacturers of wood preservative solutions is liability and warranty claims, where their preservatives are claimed to have been faulty causing wood to have displayed a short lifetime. The manufacturer has no way of knowing: (i) whether their particular preservative has been employed, and (ii) whether the preservative has been applied to the lumber correctly.

To overcome this issue, a wood preservative company can, for example, dissolve 1000 ppm of a soluble zinc salt (e.g., zinc sulphate) in their wood preservative solution prior to supply to customers. Alternatively, lOOOppm of bismuth can be added to the wood preservative solution. Bismuth is the only heavy metal that is highly toxic to microbes but non-toxic to humans. Bismuth also has a distinctive LIBS spectrum and therefore provides a quick and simple way to establish the presence of bismuth in treated timber.

Upon receiving claims of faulty wood preservative solutions, the manufacturer can then use LIBS with application of correlation techniques (as described hereinbefore) to determine whether: (1) their particular wood preservative has been used at all, and (2) whether their wood preservative has been correctly applied (e.g., is the zinc or bismuth signature present everywhere in the wood sample or only on the outside?).

As described hereinbefore, untreated samples of similar wood ("control samples") are correctly treated with the wood preservative solution (thus providing "doped samples"). LIBS spectra of the control and doped samples may be obtained and correlation library may be generated in the LIBS software, as described hereinbefore in relation to the particle board example. Samples which are the subject of liability/warranty claims may then be subjected to LIBS analysis. The resulting data typically forms two major groupings, one of which contains the wood preservative in the required quantities and another, which is more similar to the untreated controls. In this way, it may be evaluated whether wood has been treated and, if so, how well the wood has been treated.

EXAMPLE 8: Using correlation techniques or machine-learning techniques to establish the integrity of banknotes and/or security documents.

Banknotes, stock and bond certificates, credit cards, passports, bills of lading, and many other legal documents must all be reliably authentic in order to be useful. Such "security documents" are perhaps the oldest and most established of pedigrees for anti- counterfeiting innovations that extend back several hundred years. Typically the banknote and security document anti-counterfeiting measures exploit: (i) a plethora of document security features; and (ii) continually updating and changing the security features in use.

Embodiments of the present invention are ideally suited to verifying the authenticity/integrity of banknotes and other security documents by employing a method that relies on the fingerprints that are generated by LIBS spectra, which are:

· Exceedingly complex; 14,000 spectral channels is typical;

• Not necessarily simple to analyse mathematically; and

• Virtually impossible to replicate by using trial and error.

As noted previously, LIBS laser pulses generate a plasma (i.e., a state whereby materials are reduced to their elemental compositions). This is, however, a simplification because the high-energy state of the plasma allows for the production of transient species. All of the elements, their ions and the transient states have their own electronic configurations and they all can interact with each other and the substrate from which they originated. The plasma, including the transient states, can furthermore interact with the atmosphere in which the plasma exists.

Thus, LIBS spectra are characterized by extreme complexity deriving from the plasma. This complexity has hitherto arguably prevented the ready and everyday use of laser spark spectroscopy for elemental analysis (as opposed to material fingerprinting, which is taught in this specification). Such complexity can ensure that any would be counterfeiter seeking to replicate an unauthorized document would be faced with a monumentally complex task due to the complex response of a security document subjected to a laser spark spectroscopy-based authentication process.

Not only would the elemental constituents, and the structure of the security document material affect the LIBS signal, but the material properties such as material strength, surface habit, and the like would also affect the character of the signal.

In addition, LIBS ablates a small volume of material with each shot. Hence, a multi-shot train in the same nominal (x, y) location has the effect of drilling through and accumulating information from different strata within the material. However, the security document may be sampled at various depths and locations, and the resulting spectra may be compared to spectra that are known to be authentic.

In addition to the above-noted complexity, the user is also able to apply "tagging" materials into the composition of the document substrate, inks that have been used in the manufacture of the document; and/or security structures that have been used in the manufacture of the document such as security threads and the like.

An embodiment in which a banknote substrate material is doped with a taggant for the purposes of later validating its authenticity using laser spark spectroscopy will now be described.

The banknote substrate material composed of laminated polymer is doped with 1000 ppm zinc sulphate in one layer and 1000 ppm iron sulphate in altogether another layer. The banknote is then printed with inks that have been doped with 1000 ppm of copper sulphate.

The banknote is subsequently profiled using LIBS at 1 , 5, 15 and 20 shots and the spectra recorded to be used as models. One or a number of such profiles can be made in various locations on the banknote.

A banknote of unknown authenticity is then analysed using LIBS with the same shot patterns. Each shot is then compared to its known to be authentic counterpart using correlation and machine methods as described hereinbefore. Figures 5 and 6 relate to methods for establishing integrity of an item using Laser- Induced Breakdown Spectroscopy in accordance with embodiments of the present invention.

Figure 5 shows a flow chart of a method for establishing integrity of an item. Referring to Figure 5, a laser-induced breakdown spectroscopy is performed on an item to obtain a first representative spectrum at step 510. At step 520, the first representative spectrum is compared to a plurality of stored laser-induced breakdown spectra and, at step 530, integrity of the item is established based on the outcome of the comparison.

The plurality of stored laser-induced breakdown spectra may comprise a spectrum representative of an item comprising at least one predetermined element and a spectrum representative of an item that does not comprise the at least one predetermined element. The comparing step may comprise performing a mathematical correlation of the spectra. Integrity of the item may be established if the first representative spectrum correlates to the spectrum representative of an item comprising at least one predetermined element. The at least one predetermined element may comprise a plurality of predetermined elements. The at least one predetermined element may ^• comprise a chemical element. The at least one predetermined element may comprise a predetermined quantity of the at least one element. The at least one predetermined element may comprise a predetermined quantity of the at least one element. The at least one predetermined element may comprise a naturally occuring element within the item. The method may comprise the further step of introducing the predetermined element into or onto the item.

Figure 6 shows a flow chart of a method for establishing integrity of an item. Referring to Figure 6, laser-induced breakdown spectroscopy is performed on a first item to obtain a first representative spectrum at step 610. At step 620, laser-induced breakdown spectroscopy is performed on a second item to obtain a second representative spectrum. T second item is substantially identical to the first item except that the second item comprises at least one element not present in or on the first item. At step 630, laser-induced breakdown spectroscopy is performed on a sample item to obtain a third representative spectrum. The first, second and third representative spectra are processed at step 640 and, at step 650, integrity of the sample item is established based on whether the third representative spectrum correlates with the first representative spectrum or the second representative spectrum.

The processing step may identify at least one chemical element that is present in or on the unknown item and not present in or on the first item. The processing step may identify at least a threshold quantity of at least one element present in or on the unknown item. The processing step may identify a threshold ratio of quantities of a plurality of elements present in or on the unknown item, relative to each other. The at least one chemical element may comprise a plurality of chemical elements. The at least one element may comprise a naturally occuring element within the second item. The at least one element may comprise contamination within the second item. The method may comprise the further step of introducing the at least one chemical element into or onto the second item.

It will be appreciated that the embodiments described hereinbefore are intended to serve only as examples or embodiments, and that many other embodiments are possible within the spirit and the scope of the present invention.

For example, numerous building products such as cement, concrete, paint, glass, etc. that may be subject to fraudulent liability/warranty claims can be gainfully marked and tested using embodiments of the present invention. For example, cement, concrete, paint, and even glass can be marked with various metal ions and then tested using the correlation techniques described hereinbefore. A convenient marker is 1000 ppm zinc sulphate. This material may be added to the cement/concrete, paint, glass or other building items and can then, at any stage in the future, be detected and verified using the correlation or other techniques described hereinbefore.

Furthermore, many manufactured items (e.g., polymer car parts) can also be viably marked by doping the parts with, for example, 1000 ppm of zinc. Confirmation of the presence of the zinc can then be achieved by using the LIBS techniques described hereinbefore to establish integrity of the items.

Claims

1. A method for establishing integrity of an item, said method comprising the steps of

performing laser-induced breakdown spectroscopy on an item to obtain a first representative spectrum;

comparing said first representative spectrum to a plurality of stored laser-induced breakdown spectra; and

establishing integrity of said item based on said comparison.

2. The method of claim 1, wherein said plurality of stored laser-induced breakdown spectra comprise a spectrum representative of an item comprising at least one predetermined element and a spectrum representative of an item that does not comprise said at least one predetermined element.

3. The method of claim 1 or claim 2, wherein said comparing step comprises performing a mathematical correlation of said spectra.

4. The method of claim 3, wherein integrity of said item is established if said first representative spectrum correlates to said spectrum representative of an item comprising at least one predetermined element

5. The method of claim 4, wherein said at least one predetermined element comprises a plurality of predetermined elements.

6. The method of claim 4, wherein said at least one predetermined element comprises a chemical element.

7. The method of claim 2, wherein said at least one predetermined element comprises a predetermined quantity of said at least one element.

8. The method of claim 2, wherein said at least one predetermined element comprises a predetermined quantity of said at least one element.

9. The method of claim 2, wherein said at least one predetermined element comprises a naturally occuring element within said item.

10. The method of claim 2, comprising the further step of introducing said predetermined element into or onto said item.

1 1. A method for establishing integrity of an item, said method comprising the steps of:

performing laser-induced breakdown spectroscopy oh a first item to obtain a first representative spectrum;

performing laser-induced breakdown spectroscopy on a second item to obtain a second representative spectrum, wherein said second item is substantially identical to said first item except that said second item comprises at least one element not present in or on said first item;

performing laser-induced breakdown spectroscopy on a sample item to obtain a third representative spectrum;

processing said first, second and third representative spectra; and

establishing integrity of said sample item based on whether said third representative spectrum correlates with said first representative spectrum or said second representative spectrum.

12. The method of claim 11 , wherein said processing step identifies at least one chemical element that is present in or on said sample item and not present in or on said first item.

13. The method of claim 11, wherein said processing step identifies at least a threshold quantity of at least one element present in or on said sample item.

14. The method of claim 11, wherein said processing step identifies a threshold ratio of quantities of a plurality of elements present in or on said sample item, relative to each other.

15. The method of claim 12, wherein said at least one chemical element comprises a plurality of chemical elements.

16. The method of claim 11, wherein said at least one element comprises a naturally occuring element within said second item.

17. The method of claim 11, wherein said at least one element comprises contamination within said second item.

18. The method of claim 12, comprising the further step of introducing said at least one chemical element into or onto said second item.