METHOD OF PRODUCT AUTHENTIFICATION

The present invention relates to a method of object or product identification and an identification tag for use therewith.

Counterfeit products are a costly and damaging global problem. Internet trading has significantly added to this due to its extensive consumer reach, the often long distances between vendors and purchasers, and the ease of electronic purchase.

While it is difficult to put a precise figure on the 'market' for counterfeit goods it is without doubt in excess of €500 billion. The First Global Congress on Combating Counterfeiting in May 2004 suggested that the international trade in counterfeit products exceeds 6% of global trade. Added to this is the impact it has upon society and the global economy, including too the cost of policing the problem.

Counterfeiting is not anymore simply confined to classic examples such as imitation watches, fashion items and what might otherwise be described as luxury goods, damaging as these may be. It now extends to all manner of consumer goods, including items of food and drink, vehicle and aircraft spare parts, pharmaceuticals and medicines, cosmetics, works of art, CDs, DVDs, software and even fuels and fertilisers. Fashion items are a further area of considerable concern with brand damage being a significant component in this respect.

Accordingly, various uniquely identifiable tags have been used in order to combat counterfeiting. For instance, tags such as complicated labels, barcodes, holograms and RFID tags have all been utilised. However, previous tags have not eliminated counterfeiting due in part because the tags can all be copied by replication and/or can be removed from a genuine article and used in the counterfeit article.

However, a recent development in the field of automatic identification has used natural features of an item to produce or to create a "fingerprint" of the product. Natural feature identification covers a range of techniques for devising signals or signatures representative of a physical entity and suitable for identifying the entity. Thus the unique surface features of the entity are used in the identification process. There are several technologies used for natural surface identification involving an optical recording of the surface's micro structure. These technologies include Laser Surface Authentification (LSA) and Digitised Image Comparison

(DIC). Whilst it is envisaged that any natural feature identification process can be used, the invention will be herein described using, for example, the LSA technique, which is a special scanning process based on the laser speckle phenomenon.

LSA is discussed in detail in JDR Buchanan et al (2005) "Fingerprinting" Documents and Packaging, Nature, Vol. 436, 28 July 2005, the contents of which are hereby incorporated. As an overview however, a laser is used to irradiate a surface and the diffusely scattered light is recorded by a set of four photo detectors at various angles relative to the incident beam. The speckle pattern signals are processed and digitised to create a uniquely identifiable record of the surface component irradiated, much like a fingerprint. The surface characteristics cannot be generated artificially.

LSA can therefore be used to authenticate a product. For example a scan of the product or packaging is taken prior to the product leaving a manufacturer's plant and the scan is recorded on a database. At some point later in the supply chain, the product or packaging can be re-scanned and the scan compared to the original, master template. If the scan corresponds to the master, the product is authenticated as a genuine article and that it is not a fake.

The DIC technique exploits the derivation of surface images using popularly available image capture devices such as digital cameras and document image scanners, and the comparison of full images using frequency domain image processing procedures. Natural features within the item image are used to locate the area of interest from which the identification images are obtained. However, full image comparison of this kind introduces processing overheads due to the image sizes involved. These overheads have been partly resolved by the use of compression techniques.

Using natural feature identification as an authentification method for products provides a forgery-proof authentification method since the image is unique to the product and it is not possible to replicate the pattern.

However, natural feature identification, based upon surface or other constituent micro- features requires a feature set that (1 ) has sufficient degrees of freedom to allow identification signatures to be derived that exhibit to a high degree of statistical confidence that the item concerned is essentially unique and (2) stable with respect to time and measurement conditions, and thus allow consistent identification. Thus it will be appreciated that the signature produced is dependent on the location scanned. For instance, the same piece of paper will have a different micro structure and therefore a different speckle pattern in one area as compared to another. Moreover, if the area scanned changes in any way, requirement (2) is not met and consequently the master and reference scans cannot correspond.

Furthermore, if there are a large number of master scans stored on a database it can take some time for a comparison to be made between the scan and each master. Moreover,

seeking a match in this manner can result in false positives and false negatives depending on the threshold criteria used to determine a match.

It is an object of the present invention to attempt to overcome at least one of the above or other disadvantages.

According to the present invention there is provided an arrangement and method as set forth in the appended claims and elsewhere in this specification. Other features of the invention will be apparent from the dependent claims, and the description which follows

In one aspect of the present invention there is provided a product authenticator arrangement that includes a scannable surface micro structure and marking means wherein the marking means is arrangeable, in use, to enable a master scan to be in the same region as a reference scan.

In the exemplary embodiments, the marking means may include a marking defining an end of a region to be scanned. The marking comprises a defined and non-naturally occurring mark. Thus the marking can be easily identified. The marking may have a different surface micro structure to the surface micro structure that is arranged, in use, to be scanned. The marking means may include a marking defining both ends of the region to be scanned, each marking having a different micro structural surface to the surface micro structure that is arranged, in use, to be scanned. The marking means may be arranged to align a scanner in at least two transverse directions. The marking means may include at least one marking having a different surface micro structure to the micro structure that is arranged, in use, to be scanned, the marking extending at an angle other than 0 ^° or 90 ^° to a line that a scanner is arranged, in use, to repeatedly scan. At least two markings may each have a different surface micro structure to the surface micro structure that is arranged, in use, to be scanned, each marking being spaced from each other and each extending at an angle other than 0 ^° or 90 ^° to a line that a scanner is arranged, in use, to scan. The two markings may be provided by the opposite edges of an area having a different surface micro structure to the surface micro structure that is arranged, in use, to be scanned. The at least two markings may be spaced from each other along a line that a scanner is arranged, in use, to scan by the surface micro structure of the product that is arranged, in use, to be scanned, each spaced marking having at least one edge that extends at an angle other than 0 ^° or 90 ^° to a line that a scanner is arranged, in use, to scan. At least one of the two spaced markings may have two edges spaced from each other in the direction that a scanner is arranged, in use, to scan with each spaced edge extending at an angle other than 0 ^° or 90 ^° to a line that a scanner is arranged, in use, to scan. Each spaced marking may include two edges spaced from each other in the

direction that a scanner is arranged, in use, to scan with each spaced edge extending at an angle other than 0 ^° or 90 ^° to a line that a scanner is arranged, in use, to scan.

In the exemplary embodiments, the natural feature identification reading is taken by a scanner. Preferably, there is a frame associated with the scanner, in which, in use, the frame assists in aligning and taking the reading scan. The scanner may be movable in at least one direction relative to the frame.

In the exemplary embodiments, the identification comprises comparing a master scan with a reference scan. The master and reference scans may comprise a number of scans over the window. Each scan may have a different trajectory. At least one of the master or reference scan may be a line scan. Both the master and the reference scans may be line scans. At least one of the master or reference scans may comprise an area that gives a reading of the micro surface structure in two transverse directions. Both the master and the reference scan may comprise areas that give readings of the micro surface structure in two transverse directions. Control means may be arranged, in use, to reorientate the reference scan relative to the master scan, if necessary, to affect a better match between the master and reference scan. Preferably the identification tag may include at least one machine readable indicator. Preferably the indicator may be arranged, when read, to give an indication of where in a store of scans the scan of the surface micro structure is located. The indicator may be a 2D code symbol or additionally or alternatively an RFID tag. The indicator may be arranged to give an indication of the precise location of where a stored scan of the surface micro structure is located. Alternatively, the indicator may be arranged, when read, to give an encoded image of the master scan.

The identification tag may be used in combination with a database, the database being arranged to store a scan of the surface micro structure, and means for comparing subsequent scan or scans of the same surface micro structure with the stored scan. Information means may be arranged to give information of comparisons that have been made. The information may comprise any one or more of the time of a comparison or comparisons, the location or locations from where the comparison was made or the number of comparisons made. Preferably, at least one of the scans may be arranged to be effected by optical means. The optical means may be a two-dimensional image capture device, such as a camera or optical sensor array. The same optical means may be arranged, in use, to make the master or reference scan and to read the indicator.

In one exemplary embodiment the marking means is provided by a label on a product. The label may include self adhesive. The label may be flexible. The label may be formed separately from the product and attached to the product. The label may be formed on the

product. The label may include at least one window through which, in use, the scanner can scan the surface micro structure region of the product. The window may be provided by a gap in the label. The label may include the at least one machine readable indicator. The product may comprise any one or more of currency, passports, identification documents, pharmaceutical goods, consumer goods, or software. The arrangement may be used to authenticate packaging of a product.

In an alternative exemplary embodiment, there is provided a flexible article identification arrangement comprising a tag secured to the flexible article, the tag having at least one window through which the article is arranged, in use, to be identified using natural feature identification techniques, the tag stabilising at least part of the flexible article in the region of the window. In this exemplary embodiment the identification tag is suitable for fabrics and other flexible fibrous materials. The identification tag may comprise a rigid label affixed to a flexible article to be identified. Alternatively, the label may be pliable. The label may be affixed to the flexible article by securing or fixing means. The fixing means may be in contact with at least part of the flexible article. The fixing means may be arranged to penetrate at least part of the flexible article. The fixing means may extend beyond the window. The fixing means may be transparent. The rigid label and securing means may combine to stabilise an area of the flexible fibrous substrate. The label includes a window. The stabilised area corresponds to an area visible through the window. Consequently, the identification tag stabilises the fabric such that a repeatable reading may be taken. Accordingly, the tag may stabilise the substrate over substantially the whole region of the window. The window may also act as a location identifier so that a natural feature identification reading of the stabilised area's microstructure can be taken for identification purposes. Because the window is fixed relative to the flexible substrates surface microstructure, the window also enables a master scan and a subsequent reference scan to be of precisely the same area.

Preferably the securing means comprises adhesive. The adhesive may solidify when applied. The adhesive fills the window defined in the label. The adhesive is transparent to the natural feature identification recording. The adhesive is located substantially under the area of the label. A further transparent protective layer may be applied over the label. The transparent protective layer is also transparent to the natural feature identification measurement and protects the label from damage.

The tag may define a window having at least one circular border. The tag may define two windows. One or both of the windows may have a circular border. Both circular windows may be concentric. The shape of the window may be such that no straight line passing through the window from a first side to a second side will have the same properties. The tag

may include a plurality of windows spaced from each other by a border that is not of uniform width between the windows.

The window provides a marking means. The marking means being arrangeable to enable a master scan to be in the same region as a reference scan.

Preferably, the rigid label comprises a distinctive shape, such as a 2 or 3-dimensional trade mark in order to increase the recognisability of the identification tag. The tag may include information means. The tag may be used in combination with a database for identification or anti-counterfitting purposes.

Preferably both exemplary embodiments include a timing structure. The timing structure controls or specifies the magnification required when the scan comprises an image.

According to a second aspect, there is provided a method of forming an identification tag. The method comprises forming an identification arrangement on a flexible article and comprises securing a tag to the article with the tag including a window through which the article is arranged, in use, to be identified by using natural feature identification techniques with the tag stabilising at least part of the flexible article in the region of the window. The method may comprise securing the tag to an article comprising fabric. The method may comprise securing the fibres of the fabric in position over at least part of the extent of the window. The method may comprise securing the fibres by causing adhesive to penetrate at least part of the fabric.

Preferably the identification tag is substantially as herein described. The method may comprises taking a master scan of a surface micro structure and subsequently taking a reference scan of the same region as the master scan using marking means. The method may comprise aligning a scanner in two orthogonal directions in relation to the surface micro structure, and the alignment may be effected using the marking means. It may comprise defining an end region of the surface micro structure using the marking means. The method may comprise reading an indicator associated with the product and using that reading to obtain an indication of where a stored scan of the surface micro structure is located. It may comprise scanning the surface micro structure of a product on the packaging of a product. The method may comprise storing information of the master scan and comparing information from the reference scan with the stored master scan thereby obtaining an identification of the authenticity of the product. The method may comprise reorientating the information from the reference scan relative to the master scan, if necessary, to effect a closer match between the scans.

According to a third aspect there is provided a method of identifying a flexible article comprising forming an identification arrangement substantially in accordance with the second aspect and thereafter taking a master identification of the natural features of the stabilised flexible article in the region of the window, and subsequently comparing a reference identification of the natural features in order to determine the genuineness of the article. The method may comprise recording information containing a reference to the position of the master identification within a database. The reference may be combined into an indicator.

The method may comprise illuminating the area with a light source. The method may comprise illuminating the area in various illumination modes. The method may comprise digitally altering the image.

According to a fourth embodiment there is provided an authentification method comprising taking an optical image of an area's surface microstructure and deriving a signature of that image wherein the signature comprises two or more components and wherein each component corresponds to a pixel intensity of a region along a trajectory across the image.

Preferably each region corresponds to one pixel. Alternatively, each region corresponds to a group of pixels. The group of pixels may define a cluster of pixels. The pixel intensity of the cluster of pixels is an average of the intensity of each pixel in the cluster.

Preferably, the method comprises using a tag substantially as herein described to define the area's surface. The method may comprise storing the derived signature in a database. The location of the derived signature may be incorporated into an indicator that is attached to the surface. The indicator may be attached substantially in accordance with the previous aspects. The method may comprise taking a subsequent reference signature. The method may comprise comparing the reference signature to the signature stored in the database in order to authenticate the product. The method may comprise reading the indicator in order to determine the location of the stored signature in order to aid the comparison. The method may comprise forming an identification tag or identifying a flexible article substantially in accordance with the second and third aspects.

Preferably the signature may comprise more than 10 or more than 100 or more than 500 or more than 1000 components, selected to define the uniqueness of the signature within a set of signatures.

Preferably the location of each component may be spaced one pixel away from the previous component. Alternatively, each component may be spaced a plurality of pixels away from the

previous components. Each pixel area or cluster may cover a variety of different intensities. Preferably each component corresponds to the average intensity of a cluster of pixels.

Preferably the trajectory's path across the image is from one side to the other. The trajectory may comprise a linear trajectory. The trajectory may comprise a non-linear trajectory. The signature may comprise components from a number of trajectories. The trajectory's path may be stored and recalled by the indicator. The indicator may be read in order to determine the trajectory's path for the reference reading.

Advantageously, each component comprising the signature corresponds to the relative pixel density differences between two positions along the trajectory.

The method may comprise illuminating the area with a light source. The method may comprise illuminating the area in various illumination modes. The method may comprise digitally altering the image.

The present invention can be put into practice in various ways, however, several embodiments will now be described, by way of example, and with reference to the accompanying drawings, in which:

Figure 1 is a top view of an identification tag.

Figure 2 is a top view of an alternative identification tag.

Figure 2b is a side view of Figure 2.

Figure 3 is a view of a window structure for use on the identification tag.

Figure 4 is a top view of another identification tag.

Figure 5 is a top view of an alternative identification tag.

Figure 6 is a pictorial view of a magnified optical image.

Figure 7 is a pictorial representation of an optical image.

Figure 8 is a schematic representation of various scan trajectories.

Figure 9 is a schematic representation of a signature trajectory set.

Figure 10 is a pictorial representation of a cluster sequencing along a trajectory.

Figures 11-13 are a top view of alternative identification tags respectively.

As shown in Figure 1 , an identification tag 10 comprises a label 12 affixed to a flexible substrate 14. The identification tag 10 is preferably rigid but it may also be pliable providing the flexible substrate is not changeable once the tag is applied and providing also that the reading is able to be taken of the same area. For ease of understanding the label is described below as being rigid. Alternatively or additionally the pliable layer or rigidity may be effected by the adhesive. Suitably, the flexible substrate is a flexible consumer article such as a garment and the rigid label is a disc of metal or plastic.

The rigid label 12 includes a window 16 formed therethrough. The window allows a natural surface identification reading to be taken of the exposed area of the flexible substrate under the window. Thus the window is transparent to the reading and in the embodiments is shown as an aperture in the rigid label 12.

The rigid label 12 is affixed to the flexible substrate 14 such that it stabilises the flexible substrate exposed by the window. As shown in Figure 2b, adhesive 18 is used. The adhesive is applied under the rigid label in order to adhere it to the flexible substrate. The adhesive fills the window 16 and may also penetrate part of the substrate when the substrate is a fabric.

Accordingly the adhesive 18 stabilises the flexible substrate's fibres, and particularly, the flexible substrates fibres under the window. Because the adhesive 18 fills the window 16, the adhesive is also transparent to the natural surface identification reading. By "adhesive" any material that at least is able to fix the surface fibres in position is included.

Additionally, the adhesive may itself contain randomly suspended fibres or inclusions that are reflective or otherwise reactive to light or other electromagnetic sources and capable of being stabilised on hardening of the adhesive and providing a natural feature signature when scanned.

Referring back to Figure 1 , the identification tag 10 is formed by securing the rigid label to a suitable portion of the flexible substrate. At a suitable point in the production/distribution/supply chain a master natural feature identification scan is then taken. The master scan records details of the position of the master scan relative to the window's 16 boundary. This master scan is recorded on a database or may be stored and encrypted within a secondary data carrier on or in the label. The master scan may also be securely

incorporated within a hand-held reader or other reader device to enable applications where connectivity to a more remote database may be considered unreliable.

At a later time, when the genuineness of the flexible substrate is to be read, a reference scan is taken. The reference scan uses the relationship between the master scan and the window's boundary to ensure that the exact same area is scanned. Because the identification tag stabilises the flexible substrate, repeatable and/or reproducible readings may be taken.

Once the reference seen has been taken, it can be checked against the master scan. If the two correspond the product is known to be genuine. The check is performed in a secure manner within a host system containing the database. As the reference scan needs to only be compared with the master scan contained within the location in the database given by the indicator, the comparison can be completed in reduced proceeding time as the complete database does not have to be searched. This one-to-one comparison avoids the problems of false positive or false negative results that are characteristic of database searches to achieve a match. The tolerance levels of the comparison may be increased or reduced as desired.

A transparent covering layer 19 may be applied over the label 12 in order to protect it from scratches and other hermetic degradation.

As shown in Figure 2a, the rigid label 12 includes an indicator comprising readable information. Here, the indicator is shown as a readable 2D code 20 and a Radio Frequency Identification Tag (RFID Tag) 22. It will be appreciated that the indicator could comprise a 2D code or RFID tag on their own or could comprise other machine readable data carriers or media. The indicator (20, 22) carries code to indicate which natural feature identification technique is being used, the location of the master scan and code to indicate any processing or other features that have to be applied in processing to obtain identification 'signatures'. The location comprises the precise location of the master scan in a database or other memory device.

The 2D code 20 may be printed on to the label as is well known in the art. The 2D code may contain 'signature' location data. Other bar code or 2D code symbols may be printed on the label to carry other non-location data. The 2D code 20 is read in a well known manner such as a 2D code scanner or image capture device. The RFID tag is readable in any well- known manner and contains a code relating to the position of a master scan within a relevant database.

Accordingly, when the reference scan in being taken, the location of the master scan within the database can also be read from the indicator carrying the location code, such as the

RFID tag 22. The reference scan is then checked against this master scan. If the two correspond the product is known to be genuine. The check is performed in a secure manner within the host system containing the database. As the reference scan needs to only be compared to the location in the database given by the indicator, the comparison can be completed in reduced processing time as the complete database does not have to be searched. The tolerance levels of the comparison may be increased or reduced, as desired.

Still referring to Figure 2a, the window is shown as comprising a plurality of apertures 26. Suitably, three apertures 26 are provided. The apertures 26 are separated by areas 28 of the rigid label 12 having truncated sides (i.e. a trapezoid section).

After applying the label 12 where the flexible substrate 14 is known to be genuine, a scan is taken of the natural micro structure of the surface of the substrate 14. For instance, a laser scanner of a LSA apparatus is arranged in position relative to the window 16 using positional markers 30. The markers 30 comprise cross-hair markings or other structures on the label. The markers 30 enable the scanner to be precisely aligned to the label. For instance the scanner may include a frame with registration marks or apertures or other location structures that enable the scanner to be placed repeatedly over the same area. Additionally, the scanner may be movably mounted within the frame such that fine alignment can be completed automatically by the laser or other optical means registering with the markers 14 or truncated portion or both. Alternatively, the location of the markers can be identified by marking means comprising other sensing means.

Using an LSA authentication arrangement, once located, a scan or reading of the speckle pattern generated by the laser reflecting off the surface of the product or packaging can be taken and recorded. The scan includes the details of the truncated portion 28 and records its location relative to the reading. This master scan is stored in a database in a position relating to the code given by the RFID tag. Scan features arising from the window's boundary can be used to uniquely link the label to the item or product to which the label is attached.

When the product is required to be checked for authenticity, an LSA reference scan can be taken of the surface micro structure. Again, the scanner is correctly located relative to the windows using the positional markers. Where the natural surface identification method is such that only a discrete line of the window is recorded, for instance, LSA, the reference scan is referred to and the size of the truncated portion recalled so that the exact relocation of the laser can be achieved (as below). Alternatively, if the natural surface recognition is such that the entire window is scanned, the fine alignment can be completed by aligning the truncated portions of the reference and master scan during the comparison. The truncated portion

therefore allows the reference scan to be correctly aligned to the master scan before a comparison is made.

Referring to Figure 3, the precise alignment using the truncated portions is achievable because the distance between the two truncated portions is known. This allows the master scan and reference scan to be aligned in a rotational aspect because the required thickness of each of the two truncated portions will only be possible when the scan line is along the X-X line. In this instance the reference markers 30 may be optional. I

X^ = (X ₂ - X ₁ ) Z l

X ₂ -X ₁ = d _Xl + / _mn + 3χ _j = / _mn + 2dx _{

3x _j = y _l tanθ is fixed and forθ = 45°

dx _{l = yi}

X ₃ - X ₂ =L^ - TZx _x

Therefore -. (X ₂ - X ₁ ) + (X ₃ - X ₂ ) = (/ _mn + 23X ₁ ) + (L _1113x - 23X ₁ )

= K 'mm ^~ " ^~ ^max For all orthogonal scan lines.

The comparison between the reference and master scans can be completed automatically, for instance by a computer program. If the scans match, the product is genuine. If the scans do not match the operator can be alerted to the fact that the product appears to have been corrupted or is a counterfeit. Additionally the database may record the times or locations or instances of any references made to the particular master scan. An operator may therefore, for example, know that the product appears to have been sold before.

When applied to flexible packaging, the label may be located over a seal, for instance, so that if the packaging has been opened, the label is damaged or removed. The applied label may also incorporate anti-tamper features that will ensure that the label is damaged and/or un- scannable if attempts are made to remove it.

If counterfeiters attempt to replicate the label on a different or counterfeit product or packaging, or if an attempt is made to take a 'genuine' or used label and apply it to a counterfeit product or packaging, the surface micro structure of the surface underneath the

window will no longer correspond to the master scan. That is because it is not possible to realign the label in exactly the same location on a substrate that the label has been removed from or to apply the label to a different product: in either case the scanned structure will be different from the master.

Referring to Figure 4, a second embodiment of an identification tag 10 is shown, the tag is substantially as herein described. However, here the window through the rigid label 12 is circular. The markers 30 are formed by the boundary of the window.

The identification tag 10 herein described may include graphics and human readable text printed on its surface. The external shape of the rigid label 10 may also be complex in order to aid the recognisability of the identification tag 10. For instance the appearance of the tags 10 such as the exterior shape or the shape of the window may comprise a 2 or 3 - dimensional trade mark.

The method and apparatus herein described provides flexible substrates with an anti- counterfeiting solution that is fast and reliable. Accordingly, the identification of areas that may otherwise change due to freedom of fibres or other surface structures to move is enabled. Whilst it may be used with other anti-counterfeiting measures, the fact that it is not possible to accurately replicate the natural surface micro structure and because of the relationship between the marks and the surface micro structure, a very strong anti-counterfeiting solution is provided even on its own.

Figure 5 shows a further embodiment of an identification tag 10. The tag 10 comprises a label 40. The label 40 is capable of being attached to a product or packaging of product in such a way that any attempt to remove the label results in the degradation of the label's structure. The label 40 may have graphics and human readable text printed on its surface, for instance to relay product information or for advertising. As herein described, the label 40 include windows 16, and indicators 20 and 21 in order that a natural surface identification of the area under the window may be made.

In a further embodiment, the label 40 is printed or otherwise formed directly on to the product/packaging. For instance the window may be formed by areas of no-printing or areas of printing in different colours such that the scanner or image capture device can still detect the windows and therefore locate the correct position of the scan.

Accordingly, the identification tag 10 and label 40 herein described provides rigid and flexible product and packaging with an anti-counterfeiting solution. It will be appreciated that the uses extend to almost any product for example the products may include: passports, ID,

pharmaceutical goods, consumer goods, cigarettes, software. Moreover, the products may include any physical object such as for example, documents and currency that may be the target for counterfeiting.

The identification tag 10 has been described herein having an indicator that gives a location of a master scan within a database in order to allow a one-to-one comparison to be made. However, it will be appreciated that additionally or alternatively the indicator may comprises data relating directly to the master scan. For instance, the indicator may comprise an image/encoded image of the master scan so that a one-to-one comparison can be made between the reference scan and the master scan.

Whilst the above, exemplary tag embodiments have been described using LSA, it will be appreciated that the tags would be suitable for use with other natural feature identification techniques such as magnetic means and other field or energy sources may be used to derive a signature. For instance, the tags may be used with a DIC technique. Here the tags provide a fixed window which defines the area from which the signature is derived. For example, Figure 6 and 7 show a portion of the area enclosed by window 16 of Figure 1 and Figure 5. Accordingly, the DIC technique takes a digital image of the window and compares this to a master image. Following known DIC techniques the full image of the window is compared. Whilst it is known to use compression techniques to reduce the size of the images, full image comparison still involves large image sizes. Accordingly an improved method is detailed further below.

Using an optical system, which comprises an optical sensory array made up of a multiplicity of optical sensor elements, for example a digital camera or similar apparatus, the window area 16 of the tag 10 is identified. As discussed herein, the window assists in achieving accurate relocation of the digital camera. Once located a magnified, high definition digital image 50 of the region defined by the window is taken (Figure 6). The magnification and resolution of the image 50 needs to be sufficient to distinguish surface microstructures as shown in Figure 6.

A white light or controlled wavelength illumination source, such as a blue light, light- emitting diode array, may be used to allow various illumination modes to be defined.

Once the magnified image 50 has been obtained, the image is pixelised, and a grid of pixels 52 forming a trajectory across the image is defined. As shown in Figure 7, rather than storing and subsequently comparing the full pixel data, a unique signature is defined based on a scan trajectory 54 followed across the image. The signature is based on the pixels data

within the scan trajectory. In this way the signature is stored and used for comparison, which reduces the data size and therefore comparison speed.

Referring to Figure 8, the scan trajectory may be a linear path from one side of the window 16 to the other. Alternatively, the scan trajectory 54 may be a non-linear path across the window 16. Whilst single trajectories require reduced processing capability and reduced identification speed, the anti counter-fitting and reliability of the recognition process can be improved by deriving a number of scan trajectories 54 for each window 16. The number of different scan trajectories would form a signature trajectory set as shown in Figure 9, wherein a signature trajectory set comprising four trajectories is shown.

The path of each scan trajectory 54 can be fixed relative to the boundary of the window 16 to allow repeated scans to be taken along the same trajectory. The repeatability or reproducibility can be enhanced by including reference features (not shown) within the window. Moreover, the indicators 20, 21 formed on the tags 10 may include information as to the location and path of the scan trajectory 54 or signature trajectory set. The trajectories may, for example, be functionally specified by mathematical expression or pixel co-ordinate changes.

Referring back to Figure 7, the scan trajectory 54 may be defined by a moving pixel cluster 56. Here a pixel cluster 56 is a group of pixels 56. The average of the cluster 56 intensity is derived and digitalised to determine a value component of the signature. The next component of the signature is derived by taking the average value of the next pixel cluster location of the same size and configuration. The configuration may be one pixel or a chosen number of pixel positions on from the last cluster value, as shown in Figure 10. The process is repeated along the trajectory 54 chosen for the signature derivation with the values derived being used to derive the digital sequence for the signature.

As herein described, a comparison between a master signature and a reference signature can determine whether the product is genuine. A variety of threshold criteria may be applied to the signatures to determine acceptance or rejection of signatures. Moreover, images may be filtered or otherwise processed to enhance the natural features without removing the form and position of the natural features. For instance, the images may be filtered in order to accommodate differences in the illumination levels between reference and master scans.

In an alternative embodiment, the signature is comprised of components identifying the relative differences in cluster intensities between each cluster location along the scan

trajectory. In this way, differences in illumination and corresponding reflection profiles can be accommodated.

To improve the identification method, a protective transparent layer may be placed across the window 16. Here, the depth of focus can be adjusted to allow focussing upon the items surface defined by the window. Thus the protection layer prevents the surface from becoming scratched or damaged that would otherwise change the derived signature. In the event that any areas of the surface defined by the window become damaged or compromised, fragment analysis and associated threshold criteria may be used to determine a match. The fragment analysis would be facilitated by window and trajectory definition.

Advantageously, the method does not use full image comparison and is therefore less demanding in terms of the size of the digital signature derived. Further more the choice of pixel cluster size and shape can be specified to meet the various reflective properties of various micro surface features characterised by different objects and their surface conditions in order to achieve usable signatures.

It will be appreciated that this method requires the authentification process to accommodate differing reflection patterns associated with different surface structures imaged under differing lighting conditions. Accordingly, as shown in Figures 11-13, the method may include using labels or tags 10 as herein described, including a timing structure 24 that can be used to control or specify the magnification required to achieve repeatable scans. The timing structure 24 comprises alternative light and dark markings. In figures 11 and 13 the timing structure 24 is a linear structure. In figure 12, the timing structure 24 is circular.

Attention is directed to all papers and documents which are filed concurrently with or previous to this specification in connection with this application and which are open to public inspection with this specification, and the contents of all such papers and documents are incorporated herein by reference.

All of the features disclosed in this specification (including any accompanying claims, abstract and drawings), and/or all of the steps of any method or process so disclosed, may be combined in any combination, except combinations where at least some of such features and/or steps are mutually exclusive.

Each feature disclosed in this specification (including any accompanying claims, abstract and drawings) may be replaced by alternative features serving the same, equivalent or similar purpose, unless expressly stated otherwise. Thus, unless expressly stated

otherwise, each feature disclosed is one example only of a generic series of equivalent or similar features.

The invention is not restricted to the details of the foregoing embodiment(s). The invention extends to any novel one, or any novel combination, of the features disclosed in this specification (including any accompanying claims, abstract and drawings), or to any novel one, or any novel combination, of the steps of any method or process so disclosed.