GB2283455A - Authenticating articles - Google Patents

Abstract

The authenticity of an article, e.g. a passport or bank note, is determined by passing light of a predetermined polarity through one or more layers 5 of a material, e.g. polymeric plastic, carried by the article. The passage of the light produces a light pattern which can be compared with an expected pattern. The pattern may be scanned and compared with the expected pattern in a memory. <IMAGE>

Description

TITLE: METHOD FOR AUTHENTIFYING OR CONFIRMING THE INTEGRITY OF A DOCUMENT OR OTHER THING AND ARTICLES FOR USE IN THE METHOD The invention relates to a method for authentifying or confirming the integrity of a document or other thing and to articles, notably to a method for establishing that a document or other thing is authentic and/or has not been tampered with and articles carrying a plastic sheet or the like which exhibits specific properties when inspected under polarised light.

BACKGROUND TO THE INVENTION: Many forms of document are used in everyday life and business which require to be valid or from a specific source for them to fulfil the purpose for which they are intended, for example a passport or a bearer bond. However, such documents are valuable and are often counterfeited or tampered with so that unauthorised persons may use them and gain the benefit of such use. For example, criminals often steal a passport and alter the photograph therein to make the passport suitable for their use or use by some other unauthorised person.

I have now devised a method by which documents or other things can be inspected so as to determine their authenticity and/or whether they have been tampered with.

SUMMARY OF THE INVENTION: Accordingly, the present invention provides a method for establishing the authenticity of a document or other thing and/or for determining whether the document or other thing has been tampered with, which method comprises: a. passing light of a predetermined polarity through a layer or a series of superimposed layers of a material carried by the document or other thing, which layer or layers affect the passage of polarised light therethrough so as to form a resultant light pattern; b. analyzing the resultant light pattern either against a record of the expected resultant light pattern, or by passage of the resultant light pattern through a known second polarised light affecting reference layer or layers of material so as to establish a combined light pattern; and c. establishing the identity or otherwise of the said resultant light pattern against the said record or establishing the identity or otherwise of the said combined light pattern against the expected pattern for such a combined light pattern.

The invention also provides documents or other things which carry one or more polarised light affecting materials thereon in a form which can be illuminated by polarised light to provide a resultant light pattern which can be verified against a reference identity of that light pattern or by passage through a reference second light affecting material to provide a combined light pattern which can be verified against a reference identity of that combined light pattern.

To aid understanding of the invention, one application thereof will now be described with respect to the accompanying drawings in which Figure 1 is a diagrammatic cross-section through a page of a passport; Figure 2 is a plan view of the page of Figure 1; Figure 3 shows the use of coded information on the page to identify the resultant light pattern which should be formed by the light affecting material carried by the page; and Figure 4 shows the use of a second reference layer of light affecting material to produce a known combined light pattern by passing the resultant light from the passport page through the reference layer.

DESCRIPTION OF THE PREFERRED EMBODIMENT: A passport page 1 carries a photograph 2 of the person to whom the passport has been issued. Normally, this is sealed in position upon the page by an overlying sheet of plastic 3. However, if the passport is stolen, the thief can often detach the overlying sheet 3, remove the photograph 2 and substitute another photograph so that the passport now appears to relate to a different person. In order to prevent this substitution of photographs, the page 1 of the passport for use in the method of the invention is formed with a portion through which polarised light can be directed, for example a cut out portion 4, adjacent the edge of the photograph 2. Located in register with cut out portion 4 is a strip 5 of plastic which rotates the plane of polarisation of polarised light passing through it and/or refracts the polarised light.The extent and direction of the rotation or refraction can either be known by forming the strip from material whose effect is known; or can be random by using materials whose effect is not known.

To verify the authenticity of the passport, light of a known plane of polarisation is passed through the strip 5 of plastic which causes the light to be affected to give a characteristic exit light pattern. The input light can be polarised in known manner by passing it through a material which rotates the plane of polarisation of the light, the initial filter, and the resultant output light pattern can be viewed through a second filter to give a characteristic visual light pattern. If desired, the verification can be carried out using an input light source which is of different polarisation to that initially used during manufacture of the strip in determining the pattern which the strip should give and the second filter used at the verification stage can compensate for this different polarisation so as to provide a further degree of security.

In the case where the strip is made from one or more materials whose effect on the rotation of polarisation of the input light is known is used, the strip can be made up from one layer or a number of superimposed layers to give one or more rotations of the plane of polarisation of the light as it passes through the strip. The complexity of the change in the plane of polarisation can be increased by forming the strip from layers of different materials which will rotate the plane of polarisation to different extents and/or in different directions. In addition or alternatively, some or all of the strips can be formed from short blocks or lengths of different materials and by mounting the blocks in one strip so that they are out of register with the blocks in the adjacent and/or other layers.In this way the input light beam passing through the layers of material can be split to follow a multiplicity of paths, with each path imposing a differing degree of overall rotation of the plane of polarisation to the light as shown in Figure 5. The complexity of the change can also be achieved by varying the angular orientation of the blocks with respect to the longitudinal axis of the strip so that the polarised light is progressively split up into a number of different light paths giving a complex pattern of rotation of the plane of the polarised light along the length of the strip. The extent of rotation can also be varied by varying the thickness of the strips or the component layers or blocks.

The effect of each layer of the strip or of each block used to make up a layer can be calculated from a knowledge of the effect of each such strip or block, so that the overall light pattern in the resultant light issuing from the strip can be accurately predicted. At the verification stage, the user will know what pattern is expected and verification of the authenticity of the passport is a matter of comparing the observed resultant light pattern with one held in a suitable record to verify whether the strip has been tampered with in any way. Alternatively, the resultant light pattern can be observed using a second, reference, polarising filter or a strip or sheet which has been made from selected layers or blocks, so as to produce a final combined output light pattern which has a specific form.

For example, the reference layer or layers could result in a characteristic light pattern in the form of the alphanumeric characters of a company name, a company logo, or a simple series of coloured bands, as in a bar code, or a uniform white or dark light. Such a characteristic light pattern can thus be readily identified at a glance by an operator or by electronic or electro-optic scanning of the light pattern to produce a specific digital or analogue output, for example from a CCD array or a scanning photocell. This output can then be compared with a record of that pattern in a suitable memory to verify that the strip and hence the passport carrying it are authentic.

Furthermore, the input light used at the verification stage need not have been polarised in the same manner as the input light used to establish the expected resultant light pattern from the strip during manufacture of the strip. The resultant light exiting from the strip can be viewed at the verification stage through a second polarising filter which compensates for the effect of the polarisation of the input light so that the expected result light pattern is produced for identification. Alternatively, the second polarising filter at the verification stage can impose a further effect on the exiting light so as to produce a yet further pattern which is known only to the user as a result of the selection he has made for the input and second polarising filters at the verification stage.In place of a second polarising filter, one or more further strips may be used to give a specific effect on the resultant light from the strip being verified, for example to display a company name visually.

The use of a second polarising filter or reference layer(s) to modify the resulting light pattern from the strip thus provides a further measure of security in that the nature of the second filter or reference layer(s) will be known to only a few people and unauthorised duplication thereof will be difficult.

However, it may not always be feasible to make the strips or sheets for present use from materials with known properties, for example due to limitations in the amount of such material which is available. It may therefore be desirable to make the strip or sheet from material(s) whose effect on the polarisation of light are not known; to establish at the location of manufacture of such a strip or sheet the overall effect which the fabricated strip or sheet has on the polarisation of the input light: and to apply a machine readable code which identifies the resultant light pattern so that the code can be read at the verification stage and the observed resultant light pattern compared with the pattern identified by that coding.

The strip can be made up randomly from the light affecting material which can have known or unknown properties, or can be made up in an order manner using materials whose effects on the polarisation of light passing through them are either not known or are randomly selected so that the resultant light pattern it produces cannot be predicted. In this case, the strip, comprising one or more layers optionally made from one or more blocks as described above, is observed under a standardised set of conditions as to the nature of the input polarised light and, where used, the nature of the second polarising screen through which the resultant light from the strip is observed. The resultant light pattern observed can then be analyzed by suitable electro-optic methods to produce a machine readable identification of the light pattern.That identification can then be encoded onto the strip in a machine readable form, for example by forming a laser readable series of pits on the strip as with a laser disc or by applying dots and/or bars of a machine readable substance, eg. a pigmented ink or a magnetic imprint. If desired, such an identification can be encrypted to prevent unauthorised access to the identification. The encryption can be carried out in a wide range of ways. Thus,for example, by encrypting the information itself, eg.by shuffling characters in a known order, by including instructions which alter the rotation of the input and/or output polarising filters or strips and/or the relative position of the output strip relative to the strip being verified or in some other way.At the verification stage, the strip is then scanned under the same conditions as were used to form the identification light pattern to produce an identification of the resultant light pattern observed, or under different conditions which give a known variation of the resultant light pattern. The observed pattern can then be compared with the pattern corresponding to the identification carried in the coded information on the strip. If the strip is authentic and has not been tampered with, the observed pattern identification and the coded identification will be identical.

As will be appreciated, variation of the structure of the strip and the materials from which it is made enables a wide range of resultant light patterns to be produced. By the use of different input light sources, second polarising filters and/or reference strips to further modify the output light from the strip at the verification stage, many possible combinations of combined output light patterns can be achieved to give a wide range of individual security options to a user which can be tailor made to his specific requirements.

The strip which affects the light passing through it can be made from a wide range of materials which affect the plane of polarised light passing through them. Many such materials are known, for example crystalline materials.

However, we have found that many plastics, for example cellulose derivatives, polyesters, eg.

polyethyleneterephthalates, polyakylenes, polcarbonates, polyvinylic resins, etc. possess this property by virtue of the stresses imposed on the plastic during its processing into sheet or strip form or during thermal processing of the plastic. Thus calendared, extruded or blow moulded sheet plastic will have a typical light rotation pattern which will vary from process to process and from material to material. We have found that this pattern is remarkably consistent throughout a given batch of material produced in a given way. However, the light pattern characteristics will vary from batch to batch and with different processing conditions. Thus, it is possible to produce a batch of material having a given light rotation pattern, which can then be used to fabricate a number of strips and reference strips for a given end use with a known light rotation effect as described above.However, repetition of the sheet manufacturing process will give a marginally different light rotation pattern, even where the same materials are used.

For this reason, it is preferred to use the random fabrication method for producing the strips as described above, since there is no limit to the amount of such strip material which can be produced and variations in the material do not prevent its use with materials having different rotation properties.

For convenience, the invention will be described hereinafter in terms of the production and use of a strip made up from a number of randomly orientated blocks of a PVC or other sheet plastic which has been formed by blow moulding or calendaring, the sheets being obtained from different batches of material and processed under similar but not identical conditions. Such strips will have a totally unpredictable effect on the rotation of polarised light passing through them. The effect of a given strip can be identified by a suitable scanning process to provide the identification codings as described above. These are applied to the edge of the strip or as an over-print upon the top layer of the strip as machine readable dots and/or bars.These can be read when the strip is scanned at the point of verification to provide the reference identification against which the observed light pattern is compared.

The strip 5 can be an axially elongated length of the multilayer material or can be of any other suitable shape. For example, the whole page 1 of the passport can be overlaid with a sheet 3 of the light rotating material. However, it is preferred to minimise the size of the strip 5 for cost reasons and to locate the strip 5 where any tampering with the photograph 2 or other crucial information carried by the passport is most likely to be attempted. For example, the strip 5 can overlie an edge of the photograph 2 so that the photograph 2 cannot be disturbed without removing the strip 5. In this way, if any attempt is made to replace or alter the photograph 2, the strip 5 will be damaged, for example by being removed and replaced by some other plastic strip and/or by causing separation of one or more of the layers of the strip 5.If desired, the strip 5 can be formed with lines of weakness or other features, such as delaminations, which are disturbed if the strip 5 is moved and which will materially affect the light rotation pattern caused by the strip 5.

The strip 5 can thus be used to identify a passport as having been issued by a given authority in a given batch and/or to expose any tampering with the passport which will be evidenced by a change in the light pattern produced by the strip.

The strip need not be one which is scanned by passing polarised light through it. For example, the strip 5 may be laid over a reflective surface on the passport page 1 and the rotation pattern of the reflected light through the strip 5 observed.

The method of the invention finds widespread use wherever the authenticity of a document must be verified, for example to establish that a passport or a bearer bond is authentic and not a forgery. Typical of such fields of use are bank notes where the strip could replace the metal foil insert currently use; cheques where the strip could form part of the signature line upon which a user must imprint his signature, in which case it may be desirable to incorporate a layer or layers of material beneath the strip which duplicates the signature so that removal of the ink impression of the signature on the strip by chemical means which do not affect the strip will be frustrated by the presence of the signature visible on the duplicating material under the strip; to identify spare parts as being those made by the original manufacturer and not counterfeit manufacture; to validate tickets for transport, entry to sports events; credit, access control and/or identification cards; etc.

The invention also finds widespread use where it is desired to detect when a document or other thing has been tampered with. Thus, where the strip is used to carry the signature of a cheque user, this reduces the risk of alteration of the signature since this will affect the underlying strip.

Similarly, the strip could be used to protect the amount entered on the cheque or on other documents, such as bearer bonds and the like. The invention also finds use on containers for food stuffs or medicaments or in sealed containers where the lid or other closure of the container can be sealed with a ribbon or sleeve formed from the light rotating material. If the sleeve or ribbon is distorted it will affect the light pattern produced and tampering can be detected.

The invention has been described above in terms of a layer or layers which have been made wholly from a light affecting material. However, it is within the scope of the present invention to form the strip from a base material which has particles of another light affecting material scattered, in a random or ordered pattern therein or thereon. The particles will have an effect on the rotation of polarisation of light passing through them as if they were randomly located and orientated blocks as described above.

Alternatively, zones or patterns of localised stress or working can be introduced into the strip, for example by calendaring the strip or sheet with a knobbled roller or by embossing the sheet, to produce a sheet having a uniform background to a specific stress or other pattern which can be scanned as described above to expose that pattern at the verification stage. The invention is thus not to be limited as to the method by which the areas having differential effects on light passing through them are to be introduced into the strips or sheets.

The resultant light exiting from the strips can be viewed from one position. However, the exposed surface of the strip may become scratched with use and it may be desirable to view the exiting light pattern from a number of directions in the verification stage and to average the output from such multiple scanning of the strip to produce a resultant image which is less susceptible to the effects of scratches.

The strip may carry other information, for example machine readable information as conventionally used on credit cards and the like to identify the person presenting the card and details of his account, etc. The strip may also carry features which indicate the extent of usage of the strip and/or the date of issue of the card, for example part of the surface of the card can carry magnetic information which is progressively erased at each use until all that information has been erased, indicating that the card is no longer valid. Such information can also be erased by a laser or other means.

Claims (12)

CLAIMS:

1. A method for establishing the authenticity of a document or other article and/or for determining whether the document or other article has been tampered with, which method comprises: a. passing an input light of a predetermined polarity through a layer or a series of superimposed layers of a material carried by the document or other article, which layer or layers affect the passage of polarised light therethrough, so as to form a resultant light pattern; b. comparing the resultant light pattern against a record of the expected resultant light pattern; and c. establishing the identity or otherwise of the said observed resultant light pattern against the said record.

2. A method as claimed in claim 1, characterised in that the said resultant light from said layer(s) is passed through a reference layer or layers of material affecting the polarisation of light in a known manner so as to produce a final light pattern; and establishing the identity or otherwise of the said observed final light pattern against the expected pattern for such a final light pattern.

3. A method as claimed in either of claims 1 or 2, characterised in that at least one of said layers is formed from a series of shorter strips of light affecting material.

4. A method as claimed in claim 3, characterised in that the light affecting properties of at least one of said shorter strips differs from the light affecting properties of at least one other of said shorter strips in the same or another layer.

5. A method as claimed in either of claims 3 or 4, characterised in that the orientation of the material in at least one of said shorter strips differs with respect to the material in at least one other of said shorter strips.

6. A method as claimed in any one of the preceding claims, characterised in that the said shorter strips in one of said layers are out of register with the said shorter strips in another layer whereby light passing through one of said shorter strips passes through two or more of said shorter strips in another layer.

7. A method as claimed in any one of the preceding claims, characterised in that the light affecting material causes rotation of the plane of polarisation of light passing through it.

8. A method as claimed in any one of the preceding claims, characterised in that the light affecting material is a polymeric material which has been subjected to stress.

9. A method as claimed in any one of the preceding claims, characterised in that the resultant light issuing from said layer(s) exhibits a characteristic banded pattern and this pattern is compared to the expected pattern from an authentic sample of said layer(s).

10. A method as claimed in claim 9, characterised in that the resultant light issuing from said layer(s) is observed through a polarising filter to obtain a final light pattern which is then compared to the expected pattern from an authentic sample of said layer(s).

11. A method as claimed in any one of the preceding claims, characterised in that the said layer(s) are formed from randomly selected light affecting materials and/or are constructed from random sizes, orientations or thicknesses of shorter strips of light affecting material, and the said layer(s) or article carrying them is provided with a machine readable coding which identifies the resultant light pattern which such layer(s) produce; and the resultant light pattern observed is compared with the resultant light pattern which such coding identifies.

12. A document or other article which carries one or more layers of at least one polarised light affecting material thereon in a form which can be illuminated by polarised light to provide a resultant light pattern which can be verified against a reference light pattern from an authentic sample of said layer(s) or by passage through a reference layer or layers of material affecting the polarisation of light in a known manner so as to produce a final light pattern and establishing the identity or otherwise of the said final light pattern against the expected pattern for such a final light pattern.