MXPA01007401A

MXPA01007401A - Substrates for printing.

Info

Publication number: MXPA01007401A
Application number: MXPA01007401A
Authority: MX
Inventors: Robert George Stone
Original assignee: Bank Of England
Priority date: 1999-01-26
Filing date: 2000-01-20
Publication date: 2002-06-04
Also published as: GB9901522D0; EP1147495B1; ATE230510T1; JP2002536202A; AU3063100A; CA2357727A1; WO2000045344A1; EP1147495A1; GB2346110A; GB2346110B; GB0001165D0; DE60001098D1; HK1043417A1

Abstract

A substrate on which a security document is to be printed. Said substrate having physically formed therein identification features which are invisible to the eye but are repetitive so as to be detectable by computer based equipment reading a document printed on said substrate.

Description

Substrates for printing Field of the Invention This invention deals with substrates, mainly papers and in particular with a method for modifying the substrate to make it suitable for use in the printing of security documents.

Background of the Invention It is known to scan a printed document and convert the image into digital data for feeding into a computer. A copy of the original document can be printed using the digital data of the images using a laser injection or inkjet printer, and in this situation, the imaging device (usually a scanning device), a computer and a printer They act like a copier. The stored data can be edited or manipulated using a logical equipment for graphics so that the final print can be a very accurate reproduction of the original. In addition, the data can be transmitted for example through the Internet or by a Modem and a telephone line to a remote location, or stored for the REF: 131494 future use on a disk or other memory device, and this technology can be used for the forgery of security documents such as checks, bank notes, identification documents and the like.

Previous technique Methods for modifying document substrates are known so that genuine substrates can be identified and distinguished from counterfeit substrates. Typically these methods include marking the genuine substrate with materials which are fluorescent under ultra violet light rays, or which only emit light in some special region of the visible spectrum, or involve the addition of a special material such as magnetic materials or pigments. absorption of infrared rays, or the inclusion of large-scale water marking in a pictorial or bar-coded form on or within the substrate. All these methods require either a total alteration of the substrate (as in watermarking methods) or the inclusion of special materials that usually require special detectors to determine if the substrate of any document is genuine. Such methods tend to be expensive, usually the effects are easily visible to the naked eye, and it is not .. . . . »-w. * '' impossible to modify the paper and other substrates in a similar way, to confuse a verification process.

Objective of the Invention It is an object of the present invention to provide a special substrate on which security documents can be printed, having characteristics which will not be reproduced by a photocopier but which can be detected using a computer and another image formation system based on a data processor. However, the characteristics will not normally be reproduced by a copier or printer supplied with data signals from the images obtained from such an unprotected system, since it can be ordered that if the computer system or copier detects the characteristics it can therefore refuse to process the image.

BRIEF DESCRIPTION OF THE INVENTION In accordance with the present invention, a substrate on which a security document is to be printed comprises a plurality of identification features on the surface thereof, which when illuminated and images are formed by scanning produce data signals in the output of a photoelectric device, characterized in that: 1. the contrast between the identification characteristics and the rest of the surface of the substrate is such that the data signals of the images corresponding to the characteristics are substantially indistinguishable from the data signals of the images related to the rest of the substrate surface and / or the background noise signals at the output of the photoelectric device, and are therefore distinguishable by the eye; and 2. the characteristics are repeated in intervals over at least some of the surface area of the substrate, so that with validation the time or position signals related to each characteristic will carry at least one fixed relation to the signals related to another of the characteristics, so that a computational device supplied with the data signals of the images can be programmed to identify if the signals of the characteristics that carry at least one fixed relation are present in the data, to assist in the identification of the document with formed images. The characteristics can be repeated at regular intervals.

L ___ JL ____ ± ______. - £ -i- < - i-l-Ai ?? i Each of the physical characteristics can be similar in character to each of the other features on the surface. Documents of the same type may be printed on a substrate having similar characteristics that have a similar fixed relationship on the surface of the substrate. Thus, for example, banknotes of a denomination may be printed on a substrate having characteristics of the surface of a particular type and one or more particular separations. The separation can be selected to be constant in one direction only or varied according to a special, known pattern. A regular or similar separation 15 can be selected for the characteristics in another direction that carry a spatial relationship, particularly in relation to the first direction, for example perpendicular to the first direction. In a preferred example, the features are ordered in a 2D array on the surface of the substrate. The existence of such characteristics on a surface of the substrate constitutes a primary coding of the substrate, which allows the substrates to be distinguished from the substrates that do not contain the ? iiOmánmrX * .. *. * * »...,, a _ ^ _ a__ - - .-» ..- M * St ?? i characteristics, or that are distinguished from each other depending on the selection of the characteristics. Secondary coding of a substrate can be achieved by introducing a variation in the matrix such as by omitting characteristics of particular positions in such a regular matrix. In this way, for example, you can omit every fourth characteristic along each third line. Preferably, security documents are encoded using both primary and secondary encodings. In addition or alternatively, secondary coding may be provided if the array is formed of features that have two distinctive features and, instead of omitting the features at specific positions within the array, the characteristics of a type are located in a set of positions in the matrix and the characteristics of the other type are located in other positions in the matrix. In this way, in a simple example, a set of features can be of generally circular shape, while the interleaved features that produce a secondary encoding can have a different easily distinguishable shape such as a rectangular or triangular shape. _a - to «-a ?? i -i-ai -? - a? -a- t,» J ... * ...... * _ ^ L1_ || _________ ?? j __ ^ _ M_JÍÍ¡H Since the coding of a substrate can be achieved by selecting the separation between the characteristics or selecting from the characteristics that have a specific particularity such as the form which can be identified in the data signals of the images related to it, and / or by the substitution of characteristics that have a first particularity in the selected points in a matrix that occurs regularly of such characteristics by other characteristics that have a second different particularity, and / or the omission of characteristics at particular points in a matrix, there is an almost infinite number of possible combinations and permutations available to encode the substrates of the security document. Therefore, the invention not only allows a reliable method for the identification of security documents, to easily detect counterfeits which are not printed on an appropriate substrate, but each individual type of security document such as banknotes of different denominations, checks originating from different banks, passports issued by different offices, and the like, if desired may be uniquely identified by a particular primary and / or secondary coding selected for the substrate on which they should be printed. , > .-. AJ.AA? * .-, ...... ^^^^^ mnu The techniques of image analysis to identify the presence of patterns that occur regularly and / or defects within the patterns that occur regularly and / or form (s) or other features visibly distinguishable from the features detectable in an image, are readily available and known, and by the use of high-speed processors such as DSPs and the like, the image data can be checked and verify or otherwise 10 to be explored virtually instantaneously as documents. Preferably, a physical feature is selected to encode the surface of a substrate to provide a primary encoding, which does not 15 will appear on the electrostatic image of a photocopier. This ensures that attempts to reproduce the original by photocopying will only produce a copy that contains the printed content of the document unless the substrate on which it is copied contains the 20 correct physical coding on the surface thereof. More preferably, if a secondary coding is present, any variation in the primary coding which constitutes the secondary coding is nevertheless capable of being distinguished to simple sight or captured by a photosensitive device used in a photocopier. Preferably, the coding of the physical characteristics is in the form of a repeating pattern. When the identification features are such that the appearance of the security document (for example a banknote) is not affected or aesthetically disturbed, since in the case of banknotes, the introduction of new bills provided on the substrate in accordance with the invention it is permissible that there are banknotes printed on an uncoded substrate, since if the general appearance of the documents is not changed with the naked eye, the old but nevertheless authentic notes which do not contain the coding of the Physical characteristics on the surface of the substrate provided by the invention will appear similar to banknotes printed on the coded substrate. Examples of coding of the physical characteristics of a substrate mentioned above comprise intaglio embossing without ink or embossing of the surface by means of glazing during the manufacture of the substrate. '- • -' "-" a * - "» * - Two or more different coding techniques can be combined on any substrate The invention is also found in the printing on the surface of a substrate on which it must be printed. a security document of indentations and / or notches according to a first pattern containing a second pattern encoded therein, to enable a security document printed on such a substrate to be identified by holding the data signals 10 of the images obtained from scanning the document in an appropriate mathematical algorithm to determine if the second pattern can be found in the data signals of the images related to the first pattern A pattern can be encoded to produce 15 multiple iterations of a code on the substrate The coded pattern may not extend over the entire surface of the substrate that forms each document but only over selected areas. s which are aligned with the printed, particular areas of the substrate, and in accordance with another aspect of the invention, the printed areas are selected to increase the detection of variation of the substrate surface during the scanning and conversion of the image into the data signals of the images. -? * ti &-? it * t? mf ° «mtem. ^ at-u *» ** a? -. ......,. .. ....-- .. s. ,. - .. . "..«. . . - -. ....

The redundancy created by the multiple iterations can be used for benefit since the large number of similar iterations increases the detectability of the code by increasing the effective signal to the noise ratio. This in combination with the selection of particular regions of the printed areas of the final document in which iterations are located, facilitates the detection by a data processor of the presence of a pattern otherwise substantially invisible in the data signals derived from the scan. For a document identification system to work, the coding of documents must be able to be read, for example, when scanning documents and generating data signals from images which can be handled by a computer, or when using a device. of image formation or signal analysis specialist that performs this function. The invention is also found in a security document substrate adapted to be identifiable as such by having detectable surface characteristics therein, the features making identification possible as mentioned above.

The invention is also found in a security document when printed on a substrate as mentioned above. A primary application of the invention is found in the treatment of the surface of a substrate as mentioned above for use in the production of security documents to inhibit or degrade the reproduction of such security documents using a scanning process which converts the image into data signals of the images to control a printing process, in which a second control is introduced if the coding of the surface is detected by holding the data signals of the images to an appropriate algorithm, the second control which serves to degrade or inhibit the printing process to prevent the reproduction of the original document, or a reproduction of good quality thereof. A second application of the invention is found in a method of document verification by scanning the document and converting the optical information into electrical signals using a photosensitive device and in which, for recognition purposes, a data processor is programmed. to look for one or more encodings of the surface, the information in the electrical signals, which if they are detected in the data of the images obtained from the image formation and the scanning of the document, will generate a confirmation signal, validating the document, and vice versa. In this way, the invention also provides a document scanning device based on a computer which can be used to validate a document by checking that one or more patterns of one or more features are present in the document. In this way, for example, banknote authentication devices can be provided at a relatively low cost to be associated with the boxes in stores, banks and post offices, so that in the transaction points, the banknotes of Bank offered by the public can be verified before they are accepted. In the case of a value ticket, it may be of additional interest to determine what denomination it is, and if more than one organization of origin is involved, it may also be advantageous to determine which organization issued the ticket. The equipment for the verification of documents based on a computer of this type can be used as accepting devices of tickets, can be used in ticket exchangers and can be used to make it possible for blind people to discover which banknotes they have in their possession. possession.

Description of the different coding techniques The treatment of the surface of a substrate according to the invention includes any technique which results in the lighter or darker regions being visible on the surface of a treated sheet of the substrate when it is illuminated for scanning. Either or both of the primary and secondary encodings may be in the form of a repeating pattern which are distinguishable under appropriate illumination to provide a detectable content in the digital signals obtained by the scan. (1) Embossed In a first technique that includes the invention, the substrate can be embossed during its manufacture. In this way, it is customary in the manufacture of paper or plastic sheets to make the material smooth enough for printing by passing it through a high pressure contact line between two "• '" "- steel rollers, a process known as satin. By forming one or both of these rollers with indentations, a paper or plastic substrate forced therebetween will be formed with a pattern of embossing that corresponds to the indentations. By adequately encoding embossed features, the substrate will be encoded as required by the invention, and can be detected by adequate illumination and converted to digital data signals by a scanning device for analysis by a data processor. (2) Surface treatment of papers with lacquer Where a paper material or plastic substrate has a resin or lacquer or other material mixed thereto to provide a smooth surface for printing, a surface-coded structure can be formed such that the current surface of the substrate is sufficiently smooth to accept the printing ink 20 to make it possible for a security document to be printed therein, but at the same time it contains a fine pattern of less smooth regions, which may be less responsive to the printing ink. 25 (3) Impregnation The surface can also be modified by a technique in which selected regions of a substrate describe a pattern of repetition by being impregnated with a fluid such as a resin, or lacquer, such that the particularities of optical absorption or reflectance or optical density of the The substrate is altered sufficiently as between the impregnated and non-impregnated areas to be discernible under the incident light as during the scan for digitization. (4) Laser beam treatment The surface of the substrate can be etched by a laser beam, to produce cavities or notches in the surface to be printed (or pending printing). This technique by itself leads to the production of very fine patterns on the surface of the substrate and since a laser beam can be very precisely modulated, this can be used to introduce depth modulation in any such notches or cavities as well as or instead of the edge or thickness of the separation modulation. > - »1«, 1 i li ... - r j¡gjb ^^. ^. ^ T? ití ^? A ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^? ? l? Í áá ^? Á? (5) Water marking Watermarks alter the thickness and / or texture of a substrate, the variations that may and / or may become visible under the incident light and may be used to form the primary and / or secondary coding of the invention. These can be formed in two ways. In the method for making the Fourdrinier paper, the wet paper is embossed using an embossing roller when it is being formed, to fix a mark on the paper corresponding to the embossing due to that. By forming the embossing in a suitable pattern of repetition which extends over the area of the fabric, in this way the paper can be coded with the pattern of watermarks. A second technique to form a watermark uses the commonly called cylinder-matrix method. In this method the watermark is formed by a cylindrical wire mesh in which "matrices" are printed in the form of images. During the manufacture of the paper, the fibers increase to a greater or lesser degree in the matrices of the mesh and where the thickness of the paper is greater, this gives a darker effect when it observes in transmission that the regions which are thinner and for so that they seem clearer when they are observed in transmission. Without * gi | ? < However, where any type of watermark is only visible in the incident light this can be used to provide the background coding required by the invention. According to the invention, any water marking technique can be used to apply a pattern on the surface of a substrate, especially a paper substrate, which is virtually imperceptible to the naked eye, but which will appear as a low contrast pattern. when it is attached to the incident light as where a document is ordered for scanning and digitization. The techniques so far described provide a substrate encoded on the surface which can be subsequently printed to form a security document. However, some of the coding techniques, for example embossing, may be applied after something or all of the printing of the document has occurred. For example, embossing can be applied after a title, or other text, or personal data for example in the case of an ID document has been printed on a smooth substrate and a coding of the surface formed as a step post-printing ______________________________ -. * -_- - ---- - - - • •,. .. *, ** ** & Coding by embossing can be achieved while printing at least some regions of a document. In this way, the coding of the surface can be imparted to the document by notching printing commonly referred to as "without ink", or notching printing with colorless ink.In such method, an image is printed using a plate containing areas engraved, some of which are filled with ink and some of which are left empty in the case of 10 print in cut without ink. The engraved plate, inked as appropriate, is pressed under high pressure against the substrate to cause the ink to be transferred to the substrate. The substrate can be embossed with the engraved image, under the applied pressure, 15 with parts of the surface of the substrate that are printed, and others only embossed.

Brief Description of the Drawings 20 Figure 1 shows a substrate of a banknote physically formed with the characteristics of the bar code in practice not discernible to the naked eye; Figure 2 shows an image of a banknote printed on the substrate; Figure 3 is a flow diagram of the process for embossing the characteristics of the bar code on the substrate; Figures 4 and 5 show images of the banknote revealed by a computer code extraction routine; and Figure 6 is a flow diagram of a possible deflection routine.

Description of the Modality Production The process for physically forming in this case embossing, identification features on a substrate of a banknote (or other security document), will be clear from Figure 3 without further description. The resulting substrate is shown in Figure 1, except that in practice the identification features, in this case a repetitive bar code pattern, would be invisible to the naked eye.

The banknote is conventionally printed on the substrate and the result is shown in Figure 4. Since in practice the identification characteristics are invisible to the naked eye, they are not aesthetically disturbing and do not affect the design freedom of the user. Banknote image. It should be noted that the design of the banknote can be printed either before or after the identification features are physically formed in this case by embossing (Figure 3).

Detection 15 There are several ways in which computer-based equipment can detect the identification characteristics mentioned above and two of these methods are described below. The document encoded when it is scanned in 20 a computer, it is converted to a digital format. This typically means that the image is analyzed in red, green and blue channels for each element or pixel of the image. The color of the image element is assigned a value in each of these channels on a scale from 0 to 255 (8 25 bits) typically such that a full intensity is -i nwlT i I llt r i 11. lf -..... ^^^ jJaagjaaaaaaaaiaaalaaaaiiiat = assigned to the value 255 and? without color 'the value 0. In this way, the bright white will be represented by all three channels that have the value 255 and black by a zero intensity has a value of 0. 5 When a real image, such as that of the printed bank note, is scanned in the system, most of the values of the pixels will be in a central region between, say, 230 for the paper background and 40 for the darker print. The pixels related to 10 Embossed coding will be affected by the darkening of relief embossing caused by illumination in the detection device. These will generally be within a band close to the values of the paper background. 15 For example, assume that embossing is shallow so shadows are weak and mainly within a band of gray scale values 20 relative to that of the paper background. It is a simple theme for a computer program 20 restore all values between a value just below that of the paper (in this example, 228), and the background of the values related to the coding band (in this example, say 210) to a value of 10, or even zero, (almost black) and restore all other values between 210 and 0 in this example to 230 (in other words the same color as the background of the paper). This procedure has the effect of eliminating all printed design features except coding and those very weak characteristics associated with the design, which are usually very few in number since they can not be easily seen and therefore would not be included in the design. the design for aesthetic reasons. The same embossed coding by this procedure would now be converted to black (see Figure 4) so that it can be read by a program specially designed to recognize the encoding. As a simple subject, if the encoding were a series of alphanumeric characters such as letters and numbers, an optical character recognition program could be used to read the data and determine if it was likely to be a known code. Alternatively, more sophisticated image detection techniques could be used, especially if the coding were of a more complex type such as that used in digital watermarking for example. In some cases, it may be preferred in order to show the coding only (Figure 5). Alternatively, embossed coding could be extracted using a contrast enhancement routine which is commonly known as "equalization". This is shown in Figure 6. This type of routine sets the maximum value of the pixels in each channel or 255 and the minimum value to 0 and then attempts to 5 uniformly redistribute the values of the pixels intervening between the two. This has the effect of increasing the difference between the values of the pixels near the bottom of the paper and in this way those related to the code so that these are more 10 easy to recognize in a program of image recognition or routine. This method has the disadvantage that other design features not related to the code are still present and need to be ignored by the recognition routine. 15 However, more sophisticated routines can be used which recognize complex coding patterns such as those used by high-level codes in complex images and patterns.

It is noted that in relation to this date, the best method known by the applicant to carry out the aforementioned invention is that which is clear from the present description of the invention.

Claims

CLAIMS Having described the invention as above, the content of the following claims is claimed as property: 1. A substrate on which a security document must be printed comprising a plurality of identification features on the surface thereof, which when it is illuminated and images are formed by scanning, producing data signals of the images in the output of a photoelectric device, characterized in that: (i) the contrast between the identification characteristics and the rest of the surface of the substrate is such that the data signals of the images corresponding to the characteristics are substantially indistinguishable from the data signals of the images related to the rest of the surface, the substrate and / or the background noise signals at the output of the photoelectric device and are therefore indistinguishable by the eye; Y (ii) the characteristics are repeated in intervals over at least some of the surface area of the substrate, so that with validation the time or position of the signals i < -___ ii -___-? ? Mttll-lf || aiÉÍ - iá-Í-_i M ^ MM_á | Éaaaa ___ t__fÍ related to each characteristic will have at least one fixed relation with the signals related to another characteristic, so a computational device supplied with the signals of The data of the images can be programmed to identify if the signals of the characteristics that carry at least one fixed relation are present in the data, to help in the identification of the document with formed images.
2. A substrate according to claim 10, characterized in that the identification characteristics are repeated at regular intervals.
3. A substrate according to claim 1 or claim 2, characterized in that each of the identification features is 15 similar in character to each of the other features on the surface.
4. A method according to any of claims 1 to 3, characterized in that the separation of the identification characteristics is such 20 which is constant in a single or varied direction according to a known, special pattern and similar or different regular separations are selected for characteristics in other directions that carry a spatial relationship, particularly in relation to the first 25 direction, for example perpendicular to one direction. - '^ M-- - "--- ..__.., ...... .._" .. * m * A ~ ~ - M? - * * »• ... .
5. A substrate according to any of claims 1 to 4, characterized in that the characteristics are arranged in a 2D matrix on the surface of the substrate.
6. A substrate according to claim 5, characterized in that it has a secondary coding comprising a variation introduced in the matrix, such as by omitting the characteristics of particular positions in such regular matrix.
7. A substrate according to claim 5, characterized in that the matrix comprises characteristics that have two distinctive types of characteristics, the characteristics of one type are located in a set of positions in the matrix and the characteristics of the other type are located in other positions within the matrix.
8. A substrate according to any of claims 1 to 7, characterized in that the coding characteristic encoded on the surface provides a primary coding which will not appear on the electrostatic image of a photocopier
9. A substrate according to claim 8 , characterized in that the coding of ja »- * • > - * - - * - - - '- • * - "- -> - *« * --- «- - ... .. ~ ii •' i lrltlMiÉtt the identification characteristics is in the form of a pattern of repetition
10. A substrate according to claim 8 or claim 9, characterized in that the coding of the identification features comprises a gravure embossing without ink or an embossing of the surface by means of glazing during the manufacture of the substrate.
11. A substrate according to any one of claims 1 to 10, characterized in that two or more different coding techniques are combined in the substrate.
12. A substrate according to claim 11, characterized in that the identification characteristics are printed on the surface of a substrate on which a security document must be printed, comprising indentations and / or notches according to a first pattern that contains a second pattern encoded therein, to enable a security document printed on such a substrate to be identified by holding the data signals of the images obtained from scanning the document to an appropriate mathematical algorithm to determine whether the second pattern is You can find in the data signals of the images related to the first pattern.
13. A substrate according to any of claims 1 to 12, characterized in that the pattern is coded to produce multiple iterations of a code in the substrate.
14. A substrate according to any of claims 1 to 13, characterized in that the coded pattern extends over selected areas which are aligned with the particular printed areas of the substrate.
15. A substrate according to claim 14, characterized in that the printing areas are such as to increase the detection of the variation of the surface of the substrate during the scanning and conversion of the image into data signals of the images.
16. A substrate treated on the surface according to any of claims 1 to 15, characterized in that it has any lighter or darker region visible on the surface of a treated sheet of the substrate when it is illuminated for scanning, but not visible to the eye.
17. A substrate according to claim 16, characterized in that the characteristics . ^ g_ of identification are embossed during its manufacture.
18. A substrate according to claim 16, characterized in that it comprises a paper or plastic material mixed with a resin or lacquer or other material to provide a smooth surface for printing, and a surface-coded structure such that the surface The actual is sufficiently smooth to accept the printing ink to make it possible for a security document to be printed thereon, but at the same time it contains a fine pattern of less smooth regions, which are less responsive to the printing ink.
19. A substrate according to claim 16, characterized in that the selected regions describe a pattern of repetition identification when impregnated with a fluid such as a resin, or lacquer, such that the particularities of optical absorption or reflectance or optical density of the substrate are sufficiently altered as between the impregnated and non-impregnated areas to be discernible under incident light.
20. A substrate according to claim 16, characterized in that the surface is etched by a laser beam, to produce cavities or MftitirTHr l i 't i t t 1 - T • *' - - ~ »"> notches on the surface to be printed (or pending printing)
21. A substrate according to claim 16, characterized in that it comprises the 5 water marking to vary the thickness and / or texture of a substrate, the variations that can become visible under incident light and form the primary and / or secondary coding.
22. A substrate of the security document, characterized in that it is adapted to be unidentifiable as such by having the identification characteristics detectable therein, in accordance with claims 1 to 21, to enable identification as mentioned above.
23. A security document characterized in that it is printed on a substrate according to any of claims 1 to 22.
24. A method of verification of a security document according to claim 22 and the 20 claim 23, characterized in that in a first verification step a scanning process is employed to convert the image of the substrate surface of the document into data signals of the images to control a printing process, and when the 25 surface coding, a second step is introduced ^^^^ & j | fiÉ ^ ji ^ ^ verification by holding the data signals of the images to an appropriate algorithm, the second verification step, if missing, serves to degrade or inhibit the printing process to prevent the reproduction of the document, or at least a reproduction of good quality thereof.
25. A method of verifying whether a document is a security document, characterized in that a scanning process converts the image into data signals of the images for the subsequent control of a printing process and if the document is verified as a document of security, the subsequent printing process is degraded or inhibited to prevent reproduction of good quality of the document being reproduced. - J * * ***