GB2055327A - Identity document - Google Patents

Abstract

A document having an eye visible and magnetically distinctive pattern is comprised of a support bearing of a layer of magnetic material, the material and support being distinguishable from another by colour. The pattern is formed by engraving the layer so that the support is visible through the layer.

Description

tor for generating a signal wherever the said output signal exceeds a preset level, and counter means for indicating the number of signals so generated.

The arrangement may also comprise an optical reader means which is also arranged to read said predetermined region, and a further said means for deriving the characteristic sig nal from the output thereof.

The magnetic read head may be a flux rate of change head, or a flux detector (e.g. a magneto resistive head).

The arrangement may include two read heads for reading different predetermined re gions and for each read head a said means for deriving the characteristic signal from the out put thereof.

In order that the invention may be more readily understood specific embodiments thereof are now described by reference to the accompanying drawings of which, Figures la and ib respectively show the plan and crossectional views of the security document in accordance with one example of the present invention, Figure 2 shows a circuit arranged to derive a characteristic signal from the document of Fig. 1, and Figure 3 shows an alternative circuit for deriving a characteristic signal.

Although the invention is described by ref erence to specific examples it will be appreci ated that the invention is not limited to these particular examples, and other embodiments will be apparent to a person skilled in the art.

The document shown in Figs. 1 a and 1 b is formed of a layer, 13, of a magnetic material, on a support, 14, which is typically 250-750 microns thick and is formed of a plastics material such as polyvinyl chloride (PVC).

In one example the magnetic layer, 13, which is typically 10-40 microns thick, is formed of a dried dispersion of chromium dioxide particles (which are black) in a methyl methacrylate resin and this provides a good colour contrast with the support, which is typically white or has a light colour. In an alternative arrangement particles of y-ferric oxide are dispersed in a binder similar to that described above and, to improve the colour contrast, particles of carbon may also be in cluded in the dispersion. Other colour combi nations, however, may be preferred and, as will be apparent to a person skilled in the art, this may be achieved by an appropriate choice of pigments or dyes.

A visibly distinctive pattern, whih may be a portrait of the document holder, or his signa ture, is applied to the document using an engraving technique. Engraving arrangements are well known in the art (see for example BP. 1 393445) and typically a light sensor is used to detect light reflected from the object to be engraved. The output signals from the sensor are used to control the position and the SPECIFICATION Authentication of identity documents This invention relates to security documents, and especially to security documents having a visibly and magneticaily detectable pattern.

Security documents, such as bank and credit cards for example, often carry a coded number or coded data which provides information concerning the identity of the card holder. Especially in the case of certain identity documents, such as national identity cards, passports, etc., it is also customary to provide a photographic impression of the document holder When a low level security feature is provided, such as a recorded layer of a high coercivity material, for example, it may be possible for the holder to alter the code contained on the card so that he may fraudulently assume a false identity, even though the visual indication provided by the photograph is genuine.

It is an object of the present invention to provide an improved form of secure document.

According to one aspect of the invention there is provided a secure document having eye visible and magnetically distinctive patterns comprising, a support bear:ng a layer of a magnetic material, wherein the support and the magnetic material are distinguisnable from one another by colour, and the layer is engraved so that areas of the support are exposed to thereby form the said pattern.

The eye visibly distinctive pattern may take the form of a portrait or a signature.

The magnetic material may be, for example chromium dioxide or y-ferric oxide.

The layer may be structured so that the particles in spaced regions thereof are fixedly aligned along a first predetermined direction the particles in the remaining regions not being so aligned or being aligned along a substantially different predetermined direction.

There may be more than one magnetic layer.

According to another aspect of the invention there is provided a secure document system comprising, a secure document, as hereinbefore described, and an arrangement for producing a signal characteristic of part at least thereof, which arrangement comprises a magnetic read head, a means for transporting said document so that a predetermined region thereof causes the read head to generate an output signal, and means for deriving said characteristic signal from the output signal.

The means for deriving the characteristic signal may comprise means for integrating the output signal and for providing a signal representative of the integration.

The means for deriving the characteristic signal may alternatively comprise a compara depth of a rotating graver which systematically scans across the surface of the layer, 13, and cuts linear or dotted grooves or holes therein to expose the white support, 14, below. The tip of the graver is profiles, and typically has a conical or pyramidal shape, so that the greater the depth of the cut, the greater is the area of the support which is exposed. By suitably controlling the depth and separation of the grooves or holes a faithful reproduction of the original can be created and the degree of light and shade can be regulated as desired.

In the document of Fig. la the engraving is applied to the region, 11, and the grooves, 15, are shown (on an exaggerated scale) in the cross-sectional view of Fig. 1 b. In the present arrangement a line spacing of 5 lines/mm is used and the engraved region measures 22cm X 3cm. It will, however, be appreciated that other line spacings could be used.

In this way the engraving at the surface of the document provides a visibly distinctive pattern, which provides a visual verification of the identity of the document holder (a facial image or signature for example).

In this invention two alternative arrangements are provided whereby a characteristic signal indicative of the document can be derived from a prearranged region at its engraved surface.

For this purpose a transport drive means is provided which is capable of moving the document through a unidirectional magnetic ing field and then over a magnetic read head so that a narrow track (qmm wide in this case) of the document is sensed. As the document passes over the read head a time varying signal is generated by the head which re.flects the variation in remanent magnetisation along the track which is caused by variation in the depth of the engraved surface (i.e. in regions where the deepest graver cuts have been made the remanent magnetisation is least and vice versa).

In one arrangement, shown in Fig. 2, the signals generated by the read head provide an input, I/P, to a comparator, 10, which is arranged to generate a pulse whenever the input signal exceeds a preset level, and these pulses are counted and the total dispiayed using a DVM, for example. The preset level may be adjusted at 11.

In an alternative arrangement, shown in Fig. 3, the input signals, I/P, from the read head are integrated at 103 for a preset period which is controlled by a timer, 101. In this example a period of 65mS is used which is sufficient to allow the engraved region to pass over the head for detection, but clearly the period can be adjusted to suit a particular size of document and a particular transport drive speed.

The first pulse received from the read head triggers the timer, 101, which causes the input to be connected to the integration circuit, 103, via a latch, 1 02. Subsequent triggering of the timer during the preset period is prevented by the latch, 104, which disconnects the timer from the input when the pulse effecting the closure of latch, 102, is generated.

In an alternative arrangement more than one read head can be used each being arranged to sense different tracks of the document and generate more than one characteristic signal. In yet another arrangement an optical sensor may also be used to provide an additional characteristic signal.

The characteristic signal or signals which are derived from a particular document depend not only on the form and position of the engraved image but also on the contrast achieved by the depth of the engraving, the exact thickness of the magnetic layer, the profile of the graver and the properties of the magnetic material used.

It is advantageous if random variations in these factors are introduced during the preparation of documents since this enhances their characterisation. Characterisation may be further enhanced if more than one track is scanned and in a particular example a vertical and horizontal track may be used. By this technique two characteristic signals are generated and these may be used individually to provide a verification feature, or alternatively the ratio of the signals may be used.

In yet another arrangement a plurality of tracks may be read and the charateristic signals derived therefrom may be applied to an algorithm so that a secure verification signal is generated.

Since the characteristic signal is determined by measurements on the engraved surface which is also used to provide a visibly distinctive and recognisable pattern, (a face or signature, for example) it is not possible to alter or tamper with the engraved surface to achieve a different characteristic signal without also detectably distorting the pattern, and vice-versa.

This provides a desirable security feature which is particularly useful in a situation in which a positive identification of the document holder is required, as in a passport or identity card, for example.

Claims (11)

1. A secure document having eye visible and magnetically distinctive patterns comprising a support bearing a layer of a magnetic material, wherein the support and the magnetic material are distinguishable from one another by colour, and the layer is engraved so that areas of the support are exposed to thereby form said patterns.

2. A secure document according to Claim 1 wherein the eye visibly distinctive pattern takes the form of a portrait or signature.

3. A secure document according to Claims 1 or 2 wherein the magnetic material is chromium dioxide or ferric oxide.

4. A secure document according to Claims 1 to 3 wherein particles of magnetic material in spaced regions of layer are fixedly aligned along a first predetermined direction and particles in the remaining regions are not so aligned or are aligned along a substantially different predetermined direction.

5. A secure document according to Claims 1 to 4 including more than one layer of magnetic material.

6. A secure document system comprising a secure document according to any one of Claims 1 to 5 and an arrangement for producing a signal characteristic of a part at least thereof, which arrangement comprises a magnetic read head, means for transporting said document so that a predetermined region thereof is capable of causing the read head to generate an output signal, and means for deriving said characteristic signal from the output signal.

7. A secure document system according to Claim 6 wherein the means for deriving the characteristic signal comprises means for integrating the said output signal and for providing a signal representative of the integration.

8. A secure document system according to Claim 6 wherein the means for deriving the characteristic signal is a comparator for generating a further signal whenever the said output signal exceeds a preset level, and counter means for indicating the number of signals so generated.

9. A secure document system according to Claims 6, 7 or 8 wherein the said arrangement also comprises an optical reader means capable of reading said predetermined region, and a further said means for deriving the characteristic signal from the output thereof.

1 0. A secure document system according to Claims 6 to 9 wherein the magnetic read head is a flux rate of change head or a flux detector.

11. A secure document system according to Claims 6 to 10 including two read heads for reading different predetermined regions and for each read head a said means for deriving the characteristic signal from the output thereof.

1 2. A secure document substantially as hereinbefore described by reference to and as illustrated in Figs. 1 a and 1 b of the drawings.

1 3. A secure document system substantially as hereinbefore described by reference to and as illustrated in the Figures of the drawings.