WO2004013735A2 - Structured magnetic pattern anti-counterfeiting system - Google Patents

Abstract

A system and associated method provide a marking of material to be applied to goods. In one embodiment, magnetic material is applied in a predetermined pattern. An accumulation of magnetic material in one orientation across the structured pattern may provide an automatically sensible value. Magnetically readable material may be provided as a predetermined, repeatable pattern, where the magnetic material is applied to a surface with a resolution in a range of at least 10,000 to 100 dots per inch.

Description

STRUCTURED MAGNETIC PATTERN ANTI-COUNTERFEITING SYSTEM

CROSS-REFERENCE TO RELATED APPLICATION(S)

This application claims the benefit of U.S. Provisional Patent Application Nos. 60/401 ,404 filed August 5, 2002, and 60/466,271 filed April 28, 2003, respectively (Attorney Docket Nos. 31936.8001 US and 39136.8001 US1 ).

BACKGROUND

Prior magnetic security and data encoding systems include MICR (Magnetic Ink Character Recognition) systems, magnetic bar codes, "macro-noise" and remanent noise systems, and "Flying Null" magnetic barcode systems. "Macro- noise" is noise caused by nonuniformities in the substrate and in the distribution of magnetic properties within the magnetic medium, and is often characterized by repeatably random variations on a spatial scale on the order of several microns or greater. "Flying Null" is the name of a British company and the company's technology. The Flying Null technology uses a soft magnetic medium coated in a pattern on a plastic film substrate, and reads the pattern by moving the null magnetic field region between two opposed magnetic poles across the medium and detecting the resulting switching of the magnetization of the medium as the null moves over it.

U.S. Patent No. USO4,806,740 by Gold, et al., describes a magnetic anticounterfeit system using a long stripe of magnetic medium printed on a document. Nonuniformities in the magnetic medium due to scratches, substrate nonuniformities, or intentional nonuniform deposition of the magnetic medium provide a "repeatably sensible" random pattern. A standard magnetic read head scans the stripe to extract a "repeatably sensible random" signal: a signal that is always the same every time the stripe is read, but is uncontrolled and for all practical purposes random and distinct for every such stripe. The "repeatably sensible random" signal is effectively a unique fingerprint for every stripe and can be used in conjunction with a database or encrypted description to confirm the validity of a document.

[31936-8001 -WOOOOO/app as filed.doc] 8/4/03 U.S. Patent No. USO4,985,614 by Pease, et al., describes a system very similar to Gold's, with an improvement consisting of a prerecorded electrical signal recorded on the magnetic medium to enhance the detectability of the varying characteristics of the medium.

The systems described in U.S. Patent No. USO5,920,628 and related patents USO5,428,683, USO5,546,462, and USO5,365,586 by Indeck et al. are very similar to Gold's system, except that Indeck's technique uses "remanent noise" in a magnetic medium, which noise is independent of macroscopic nonuniformities in the magnetic medium such as clustering of particles, substrate nonuniformities or scratches. Remanent noise as defined by Indeck is solely due to the size, shape and orientation of magnetic particles in the medium. Like Gold's technique, Indeck's technique makes use of "repeatably sensible" noise, but whereas Gold's technique depends on nonuniformities having a spatial scale substantially larger than the size of the magnetic particles in the medium, Indeck's technique depends on nonuniformities having a spatial scale essentially equal to the size of the magnetic particles in the medium.

BRIEF DESCRIPTION OF THE DRAWINGS

Figure 1 is a suitable "MagDot" or binary magnetic pixel array.

Figure 2 is a MagDot consisting of a single column of magnetic pixels.

Figure 3 is a response of a magnetic read head to an isolated column of magnetic pixels such as the MagDot in Figure 2.

Figure 4 is a computerized image of an enlarged microphotograph of an actual printed MagDot.

Figure 5 is a gray-scale MagDot (halftone magnetic pixel array).

Figure 6a is a MagDot with distinct columns separated by gaps.

Figure 6b is a plot of the vertical density function of the MagDot represented in Figure 6a.

Figure 7 is a signal due to the MagDot of Figure 1.

Figure 8 is a signal due to the MagDot of Figure 6a.

Figures 9a, 9b, and 9c are a MICR character "3" and two MagDots designed to produce a signal that mimics the signal from the MICR character "3".

Figure 10a is a vector graphic version of a MagDot.

[31936-8001 /SL032160.064] -2- 8/4/03 Figure 10b is a halftone version of a MagDot.

Figure 11 is a diagram of a process for authenticating a document.

Figure 12 is a MagDot applied to the back of a holographic hot stamping foil.

Figure 13 is a diagram of a process for decoding a MagDot to extract encoded information.

Figure 14 is a document bearing a MagDot.

Figure 15a is a MagDot having independent information encoded in two orthogonal directions.

Figure 15b is a plot of the vertical density function of the MagDot of Figure 15a.

Figure 15c is a plot of the horizontal density function of the MagDot of Figure 15a.

Figure 16 is a representation of a process for reading a MagDot having independent information encoded in two orthogonal directions.

Figure 17 is an apparatus for reading a MagDot multiple times using a read head having multiple orientations.

Figure 18 is a diagram of a MagDot reader system which may include read heads in addition to a MagDot read head.

Figure 19 is a diagram of a MagDot security system that employs random or custom fonts that mimic MICR fonts.

Figure 20 is a tamper-evident seal comprising a substrate with patterned adhesion properties, a layer of magnetic material, and an overlayer with patterned adhesion properties.

Figure 21 is a tamper-evident seal comprising a substrate having spatially varying magnetic properties, a non-resealable adhesive layer, and an irreversibly stretchable overlayer.

Figure 22 is a hot-stamping die bearing bumps for applying a MagDot in the form of a magnetic material patch having an array of pits.

Sizes of various depicted elements are not necessarily drawn to scale and these various elements may be arbitrarily enlarged to improve legibility.

[31936-8001 /SL032160.064] -3- 8/4/03 DETAILED DESCRIPTION

The invention will now be described with respect to various embodiments. The following description provides specific details for a thorough understanding of, and enabling description for, these embodiments of the invention. However, one skilled in the art will understand that the invention may be practiced without these details. In other instances, well-known structures and functions have not been shown or described in detail to avoid unnecessarily obscuring the description of the embodiments of the invention.

The terminology used in the description presented below is intended to be interpreted in its broadest reasonable manner, even though it is being used in conjunction with a detailed description of certain specific embodiments of the invention. Certain terms may even be emphasized below; however, any terminology intended to be interpreted in any restricted manner will be overtly and specifically defined as such in this Detailed Description section.

Unless described otherwise herein, the blocks and features depicted in the Figures are well known or described in detail in the above cross-referenced provisional patent applications. Indeed, the detailed description provided herein is explicitly disclosed in the provisional patent application; additional material regarding aspects of the invention will be recognized by those skilled in the relevant art as being inherent in the detailed description provided in such provisional patent applications, or well known to those skilled in the relevant art.

In an embodiment of the present invention disclosed herein, a non-random process is used to deposit magnetic material in an intricate, repeatable pattern. For example, a laser printer is used to print a high-resolution array of pixels using a magnetic toner, and the array of pixels is designed using an algorithm such that the pixel pattern encodes a particular character string or represents a pseudo-random number string. A standard magnetic read head such as a MICR read head is used to scan the pattern. A pattern of this type is herein generally referred to by the term, "MagDot". Indeed, the term "MagDot" refers to any structured magnetic pattern disclosed herein, and equivalents and alternatives thereof.

The anticounterfeit effectiveness of embodiments of the present invention is due to at least three facts: 1 ) the fact that every printing press or laser printer prints

[31936-8001 /SL032160.064] -4- 8/4/03 a high-resolution pattern slightly differently, 2) the fact that photocopiers cannot accurately copy patterns that have a resolution close to or finer than their resolution limit, and 3) the fact that the disclosed pattern can encode predetermined information that cannot be copied by ordinary magnetic recording techniques. Even though the magnetic material pattern of this embodiment of the present invention is repeatable on a particular laser printer using a particular kind of paper and a particular type of magnetic toner, it is effectively non-copyable otherwise.

In both Indeck's and Gold's systems, noted above, the anticounterfeit effectiveness depends on the extreme difficulty of copying small-scale patterns generated by an uncontrolled, random process. However, in Gold's system the pattern resides in the spatially varying particle density in a magnetic medium, whereas in Indeck's system the pattern resides in the varying characteristics of individual particles and in their spatially varying average orientation. No information is recorded in the patterns, though the patterns are individually distinguishable.

In disclosed embodiments of the invention, a laser printer with magnetic toner, such as an HP-1100 Laserjet with MICR toner, is used to print a high- resolution binary pixel pattern on a document. For example, the document may be an event ticket as illustrated in Figure 14. The document may contain, for example, a graphic design 1422, a date 1420, a substrate 1424, variable information 1426 and 1428, a barcode 1432 and a MagDot 1430. An example of an appropriate binary pixel pattern is illustrated in Figure 1. The pattern 110 illustrated in Figure 1 is a filled rectangle 1/8 inch square. It has a solid line boundary 105 one pixel wide, and a pattern of black and white pixels e.g. 100 serving as the fill pattern. The pixel resolution is 600 dots per inch. The number of black pixels in each column and row varies according to a predetermined algorithm. For the purposes of this description, the number of black pixels in a column will be referred to as the vertical density of that column, and the ordered list of vertical densities corresponding to an ordered list of the columns will be referred to as the vertical density function.

When the magnetic read head from a standard check reader using a vertically oriented gap is used to read the pattern, a signal is produced that corresponds approximately to a convolution of the vertical density function with the impulse response function of the read head and associated electronics. For example, a single isolated vertical column of pixels as illustrated in Figure 2

[31936-8001 /SL032160.064] -5- 8/4/03 produces a pair of spikes as illustrated in Figure 3: a positive spike 305 corresponding to the leading edge of the column, and a negative spike 330 corresponding to the trailing edge of the column, separated by a space 325 having an interval 320. (The x-axis 335 represents distance, while the y-axis 330 represents intensity or magnitude.) The height of the spikes corresponds to the vertical density of the column. If there is remanent noise due to the magnetic particles in the medium, or "macro" noise due to variations in magnetic medium density, it should appear in the form of repeatably readable fine structure 330 in the region between the two spikes. However, on a paper substrate it is very difficult to read remanent noise repeatably due to the flexibility of the paper fibers. Accordingly, remnant noise and noise due to uncontrolled irregularities and nonuniformities in the magnetic medium may be ignored or filtered out and discarded, and only the portion of the signal due to predetermined patterns of magnetic material in the MagDot used.

A reader for MagDots can have the general structure diagrammed in Figure 18. A magnet 1800 magnetizes the magnetic medium in the MagDot 1802, as the certificate 1804 bearing the MagDot passes under the magnetic read head 1806. When the MagDot subsequently passes under the read head 1806, an analog signal 1808 is generated. This signal may be amplified by amplifier 1830 and passed to an A/D convertor 1810, and optionally to a MICR processor 1812 as well. The A/D convertor digitizes the analog signal 1808 for subsequent processing by signal processor 1812, to form an ordered list of numbers called a "vector"1832. The signal processor 1812 can have any of several different alternative forms, such as a serial processor with CPU and memory, or such as a parallel processor such as a gate array or a high-speed DSP. Whatever its structure, the signal processor 1812 may perform any of several functions on the vector 1810, including correlation, vector distance measurement, comparison with a set of vectors stored in memory 1814, Fourier transformation, and/or filtering. By comparing the signal vector 1810 with pre-recorded vectors stored in memory within the reader or at a remote location, the reader may determine which pre-recorded vector the signal vector is most similar to, and determine that the signal vector is for practical purposes identical to the pre-recorded vector if the degree of similarity is high enough. Alternatively, the processor may compare the vector with shorter vectors to decode

[31936-8001 /SL.032160.064] -6- 8/4/03 the signal vector. For example, the signal vector may be a string of shorter vectors, with each shorter vector selected from an alphabet of short vectors. Decoding the signal vector then amounts to determining which of the alphabet vectors is most similar to each such shorter vector in the signal vector string, and listing a representation of those alphabet vectors.

Figure 13 shows an example of a process or routine for decoding a MagDot, which may be represented in software. In general, aspects of the invention described herein may be stored or distributed on computer-readable media, including magnetic and optically readable and removable computer disks, hardwired or preprogrammed in chips (e.g., EEPROM semiconductor chips), as well as distributed electronically over the Internet or over other networks (including wireless networks). Those skilled in the relevant art will recognize that portions of the invention may reside on a server computer or a network of server computers, while other portions reside on a client computer or a network of client computers. Data structures and transmission of data particular to aspects of the invention are also encompassed within the scope of the invention. In general, while hardware platforms, such as the disclosed printers and readers, are described herein, aspects of the invention are equally applicable to any data processing device such as a computer, or even nodes on a network having corresponding resource locators to identify such nodes.

Figure 13 illustrates a process for decoding a structured MagDot in which information is encoded in the pixel structure of the MagDot. The process comprises reading the MagDot pattern from a document, deconvolving the resulting signal using a reader impulse response function, then comparing segments of the deconvolved signal to a library of structured MagDot signals. Deconvolution is not necessary, but it can be used to normalize the signal when it may be read by readers having different impulse response functions.

MagDots can be applied to documents in conjunction with barcodes, MICR codes, holograms, fluorescent markings, and practically any other security features. Accordingly, in addition to reading the MagDot, the reader can include one or more other feature readers 1834 such as MICR decoder, a bar code read head, fluorescent taggant reader, hologram reader, RFID tag reader, two-dimensional imager (e.g., CCD or CMOS image sensor), and so forth.

[31936-8001 /SL032160.064] -7- 8/4/03 The kinds of documents to which MagDots can be applied include paper and plastic currency, postage stamps, prescription pads, drivers licenses, shipping documents, title certificates, gift certificates, passports, credit cards, labels, hang tags, event tickets, stock certificates, checks, money orders, authenticity certificates, coupons, product packaging, copyrighted products, packages, boxes, envelopes, pouches, seals, tokens, coins, access passes, green cards, ID cards, removable memories, and the like. Indeed, MagDots can be applied to any surface at all (not necessarily two dimensional documents or objects) and can be read as long as the substrate on which they are applied does not have magnetic properties that prevent proper functioning of a magnetic read head.

A MagDot may be used in an encryption system to provide, for example, a private or public encryption key or to store encrypted or scrambled information. The predetermined distribution of magnetic particles produced by a printing process may be selected, for example, to represent specific information such as a serial number, or it may be selected to represent an effectively random number.

The MagDot pattern shown in Figure 1 produces a signal 700 having representative leading and trailing edges 720 and 740, and mid portions 710 and 730, as shown in Figure 7, when read using a high-resolution magnetic read head, although the detailed structure of the signal depends on the characteristics (e.g., impulse response) of the read head and its associated electronics. Typically, a narrower gap in the read head results in sharper, narrower spikes in Figure 3 and a more highly resolved signal.

At a pixel resolution of 600 dpi, the characteristic frequencies correspond to a spatial size of at least 1/1200 inch, or about 21 microns and larger. Magnetic toner particles, on the other hand, have a size in the range of 0.1 micron to 1 micron. Thus, "remanent noise" due to the size, shape and variable properties of the individual toner particles has little effect on the shape of the signal that characterizes the MagDot pattern.

It is also evident that the detailed shape of the signal in Figure 3 depends on the nature of the surface on which the pattern is printed, and on the interactions between the magnetic toner and the surface. For example, although the pattern in Figure 1 is sharply defined in a computer artwork program such as Adobe Illustrator and appears on a computer screen as indicated in Figure 1 , the pattern has a

[31936-8001 /SL032160.064] -8- 8/4/03 substantially different appearance (e.g., as shown in Figure 4) when printed on relatively rough paper. The MagDot represented by the mottled rectangular area in Figure 4 is in practice often only about 1/8 inch wide. Nonetheless, the same pattern of Figure 1 printed multiple times on the same paper produces a sufficiently repeatable signal that the printed patterns are easily recognized by a magnetic reader as representing the same ideal pattern. Nonetheless, if the MagDot patterns are printed at a resolution close to the limiting resolution of a laser printer, it is extremely difficult to make a passable copy of the MagDot pattern from a sample such as that of Figure 4.

Because a magnetic reader such as a check reader detects variations in the magnetic structure of a medium, and because the amplitude of the detected signal depends on the distance between the read head and the magnetic medium, one way to create a MagDot is to create a pattern of indentations or bumps on a smooth surface and then to apply a substantially uniform coating of magnetic medium over the surface. Alternatively, the indentations or bumps can be created at the same time that the coating is applied. For example, a magnetic stripe foil may be applied by hot stamping onto a smooth plastic surface, using a hot stamping die 2200 such as that illustrated in Figure 22 that has indentations or bumps 2215 in its surface 2210. The resulting MagDot has a structure corresponding to the pattern of indentations or bumps, and the structure will be nearly the same for every MagDot using that hot stamping die. Different dies could of course produce different patterns, as well as a die having automatically adjustable bumps to automatically vary resulting indentations in a surface or foil. Indeed, any form of impact printing may be employed with magnetic foil or magnetic inks in this manner to produce MagDots.

The identity of a document may thus be determined by reading a MagDot pattern that has previously been printed on the document. The MagDot may then be read and compared to a previously recorded representation of the MagDot signal stored in a database or printed on the document. In Figure 11 , a procedure for authenticating a document using a MagDot and a reader is illustrated, from which software may be created.

In an alternative embodiment, the pixel pattern of Figure 5 uses halftone grey-scale pixels. The resulting signal has all the same characteristics as those

[31936-8001 /SL032160.064] -9- 8/4/03 indicated in Figure 8, which shows representative portions 620, 630, 640, 650 and 660. Using halftone pixels, however, significantly increases the difficulty of accurately copying the MagDot pattern by methods such as photocopying or scanning and printing.

In order to maximize the repeatability of the printed pattern and the consequent sharpness of the signal, it is desirable to use a photographic-quality paper so that the printed pixels are all distinct. It is noteworthy that if the pixels (610, Figure 6a) are distinct and sized such that the columns have gaps between them as indicated in Figure 6a, the vertical density function and the corresponding signal have a significantly periodic nature as shown in Figure 6b, due to the regular spacing of the pixel columns whose vertical density is, e.g., shown in Figure 6b. The periodic nature in this case can be used to provide a timing signal to correct for any variations in reading speed, or to correct for variations in column spacing, or it may be ignored. A solid vertical border 600 provides sharp leading and trailing spikes in the signal, whereas a solid horizontal border 605 only provides a small leading and trailing spike.

If the MagDot pattern of Figure 1 is rotated 90 degrees and read again, it produces as indicated in Figure 15 an entirely different signal from that of Figure 7 because there is no correlation between the number of pixels in a row (horizontal density) and the number of pixels in a column (vertical density). Therefore, the signals derived from reading a MagDot in two orthogonal directions are uncorrelated and unrelated.

Since the pixel pattern is easily predetermined, it is possible to make MagDots whose vertical density functions are identical but whose horizontal density functions are different, such as is indicated in Figure 15. Thus, for example, it is possible to use the vertical density function to correspond to a given application sub-category, and different horizontal density functions to correspond to different documents within that application sub-category. So, if the magnetic pixels in any column in Figure 6a were redistributed vertically, the signal read by a vertical read head would be unchanged but the signal read after rotating the MagDot by 90 degrees would be different according to how the pixels had been rearranged.

Figure 16 illustrates the steps by which is it possible to extract independent horizontal and vertical information from a MagDot. The MagDot is read in two

[31936-8001 /SL032160.064] -10- 8/4/03 different orientations, and then the signals obtained by the two readings are compared to expected signals.

In some cases it is beneficial to hide a MagDot to provide a covert anti- counterfeit feature on a document. Experiments have shown that the MagDot signal can be read through a 25-micron polyester film overlaminate, through an opaque aluminized holographic hot stamping foil, or through opaque non-magnetic ink. Thus, is possible to hide a MagDot behind an overlaminate, a region of hot stamping foil, or a region of non-magnetic ink. In Figure 12 a holographic hot stamping foil is illustrated, with a polyester substrate 1200, release coat 1210, embossed holographic layer 1215, adhesion interlayer 1220, MagDots 1225, and heat activated adhesive 1230. Preferably, the MagDot is read after overlamination, coating, overprinting or any other process that could change the structure of the MagDot. Additionally, other information may be recorded before any obscuring overlamination. For example, the overlamination may prohibit visual light inspection (such as by a person), but a bar code or other information may be recorded in infrared ink so that the bar code may be automatically read through the overlamination with a suitable reader.

Another embodiment of the invention uses MagDots deliberately constructed to produce signals that mimic standard MICR characters or other characters, such as bar codes or other machine-readable symbols. Because a standard check reader in effect reads the vertical density function of a MICR character, any pixel pattern that has the same vertical density function as a MICR character will be decoded by a standard check reader as that MICR character. Figure 9a, 9b and 9c illustrates different magnetic ink patterns that produce signals identical to the signal from a MICR character "3". In Figure 9a is a standard MICR "3". In Figure 9b, all pixels have been dropped non-overlapping to the bottom of the pattern so that the number of pixels in each column is the same as in the "3" of Figure 9a, but there are no gaps between pixels in any column. That is, horizontal bars 900, 905 are stacked directly onto the bottom bar to form bar 920. In Figure 9c, the number of pixels in each column are the same as the number of pixels in the corresponding columns in Figure 9a, but the gaps between them have been randomized. Features 935, 940, 945 and 950 do not correlate directly to any of the features 900, 905, 910, 915 or 920. All of these patterns will produce identical signals to a MICR "3".

[31936-8001/SL032160.064] -1 1- 8/4/03 One way to use this embodiment is to use an automatic random font generator to construct custom fonts for different customers. Each customer has their own font in that case, but every font reads the same in a MICR reader. By reading one of the characters at a right angle to the ordinary direction, a "fingerprint" signal may be extracted that uniquely identifies the font. This embodiment is not limited to mimicking MICR characters. In fact, a two-dimensional bar code reader or a bar code reader that illuminates a document with a thin vertical line of light that moves horizontally, or moves the line relative to the document (a raster scanner) can optically measure the vertical pixel density function of a character in such a random font, and the pixel density function signal can then be processed in the same way that a MagDot signal or MICR signal would be processed.

Figure 19 illustrates one possible process for using random magnetic fonts as security markings. A service provider generates the random fonts and distributes the fonts to customers in an electronic form such a computer program or a look-up table. The customer uses the fonts to print identifying symbols on secure documents, and distributes the documents to end users. At the point of use, the symbols are read as MagDots and interpreted by looking them up in a database.

Yet another embodiment uses the structure of a MagDot to encode information in the form of a vertical density function. In the simplest case, the pixel number in each column corresponds directly to a decimal value. In Figure 15, two independent density; functions are read in orthogonal directions from a single MagDot. In principle, it should be possible to read as many binary bits as there are pixels in a MagDot, though in practice it is difficult. If maximum data retrieval is desired, then the MagDot can be read at N different gap orientations or scan directions, then the individual pixel values can be calculated using standard linear algebra methods. Figure 17 shows one possible way to implement a reader whose gap orientation can be varied for multiple reads of a MagDot. In Figure 17 the read head 1735 mounted on wheel 1730, driven by a stepping motor 1715 via drive chain 1725 reads the MagDot 1710 on a document 1705 that is moved through a guide slot 1745. The MagDot can be read multiple times with the stepping motor 1715 rotated to a different orientation each time. If the effective resolution of the read head across the MagDot is N pixels, and if N scan readings are taken at different orientations of the read head, then sufficient information is acquired to provide a set

[31936-8001 /SL032160.064] -12- 8/4/03 of N² equations in N² unknowns because each scan produces the information for N equations. That is, each resolvable element of the signal in a scan amounts to a sum of the signals from each pixel in a column of magnetic pixels, and with each different orientation of the read head the set of pixels forming a column is different. The directions of motion of the document 1755 are represented by double arrow 1700. Directions of motion of the drive chain 1725 are represented by double arrow 1720.

It is intended that the scope of the following claims should be interpreted broadly to include substitution of equivalent steps, substances, components, and methods. For example, any kind of magnetic medium that can be applied to a surface in a predetermined pattern may be used to make MagDots. Ion-implantation printing, laser printing, photocopiers with magnetic toners (xerography), foil transfer printing, flexo printing, any form of ink jet employing magnetic ink, any form of thermo printing employing magnetic ink, as well as any electrophotography printing techniques (including direct and indirect non-optical electrophotography), any impact printing techniques (including dot matrix, daisy wheel, and the link), gravure printing and offset printing are among the printing processes that can apply magnetic media, but there are a large number of other processes with the potential of applying magnetic media such as selectively patterned thermal evaporation, sputtered magnetic coatings with patterned laser ablation, any of the various other semiconductor fabrication techniques, as well as silk screening. Any magnetic reading head can be used, including standard commercial check readers, mag stripe readers, magnetic tape readers and the read heads used on hard disk drives and floppy disk drives. (The term "mag" is generally used as shorthand for "magnetic") More exotic reading methods may be used as well, such as magneto- optic methods, magnetic scanning probe microscopes, or "Flying Null™" type readers.

The orientation of the gap in a magnetic reading head relative to a MagDot is preferably consistent in order to get consistent readings of the MagDot pattern, but need not be vertical. Similarly, the columns need not be vertical and the rows need not be horizontal, and the gap need not be parallel to the columns nor perpendicular to the rows. The pixels can be any shape, and they can have any spacing or size.

[31936-8001 /SL032160.064] -13- 8/4/03 However, the vertical density varies in the horizontal direction so that there is a nontrivial vertical density function detectable by the reader.

When the MagDot signal is read by moving a MagDot relative to a magnetic read head, any speed variations in the motion will distort the signal and result in ambiguities when two such signals are compared, because the precise timing of features in the signal will be only approximately known. A separate timing signal on magnetic media may be provided as a way to remove those ambiguities. One embodiment of the present invention uses a MagDot whose vertical density function is modulated with a constant spatial period, such as by printing the MagDot as a set of vertical columns of magnetic ink pixels, in which the columns are evenly spaced but of varying vertical density. A MagDot made this way is illustrated in Figure 6, and the signal resulting from the MagDot is illustrated in Figure 8. The signal has an easily observable, distinct periodicity corresponding to the spacing of the columns in the MagDot. The resulting MagDot signal will have an easily detected periodicity, but any two MagDots made the same way will nonetheless produce signals with slight differences. The periodicity of the signal can be used as a timing signal, while the variations between signals can be used to distinguish between nominally identical MagDots. This technique greatly simplifies the use of a hand- swipe reader for Mag Dot-protected cards or other documents. The periodicity in a MagDot made this way can be detected optically or magnetically, but magnetic detection is preferred.

Note that the timing signal does not need to be periodic. If a series of MagDots are printed as illustrated in Figure 6, all having the same particular distribution of pixels, their MagDot signals will all have the same general shape. Small-scale variations between the individual MagDots can be detected by matching the large-scale components of the MagDot signals to normalize the timing between them, and then measuring the small-scale (high-frequency) differences between the normalized signals.

Any change in the detailed structure of a MagDot is easily detectable if the change is on a physical scale such that the spatial frequency change is within the spatial frequency band detected and analyzed by the MagDot reader. Accordingly, in a further embodiment, a MagDot may be used to create a tamper-evident seal or label as indicated in Figure 20. A magnetic material 2000 is applied to a substrate

[31936-8001 /SL032160.064] -14- 8/4/03 2005. An adhesive film 2010 is applied over the magnetic material. Either the substrate 2000 or the adhesive film 2010 has a spatially varying adhesion characteristic, so that when the adhesive film is peeled off of the substrate, some of the magnetic material is removed with the adhesive film and some remains on the substrate. It is extremely difficult to replace the adhesive film on the substrate so that the original structure of the magnetic medium layer is restored; so removal and replacement are easily detected.

An alternative tamper-evident seal as illustrated in Figure 21 employs a substrate 2100 with its own spatially varying magnetic characteristics 2105. An overlayer 2110 bearing magnetic material patterns 2115 is applied over the substrate and the magnetic signal is read and recorded. If the overlayer is removed and re-applied, it is virtually impossible to re-apply it in exactly the same position. Because the MagDot pattern detected by the reader will be a composite of the magnetic pattern of the MagDot and the spatially varying magnetic characteric of the underlying substrate, the removal and replacement of the seal can be detected easily by the change in the MagDot pattern.

In either of the MagDot seals described above, it is advantageous to make the peel-off layer of an elastic, easily deformable material such as polyethylene or PVC so that it is very difficult to peel off the layer without permanently distorting it.

Although the foregoing description of the embodiments of the invention has described the MagDot patterns in terms of pixels, in fact the patterns need not be pixellated. Any predetermined, controllable pattern of magnetic material may be used, such as the vector graphic pattern in Figure 10a. Thus, the pattern may be composed of complex regions, lines, curves, and shapes 1000, 1020 without identifiable pixels. Similarly, the MagDot patterns may be formed in continuous gray scales or in discrete gray scale steps or in binary black-and-white regions. For example, one way to make a MagDot pattern is to render a photograph as a halftone image laser-printed using magnetic toner as indicated in Figure 10b. Another way to make a MagDot pattern is to apply an edge-enhancing filter to a photograph (or process a photographic or digital or video image any other way), and render it as a gray scale or black-and-white image. In any MagDot, it is preferred (though not necessary) to have boundaries 1010, such as boundaries on both left and right sides, to simplify the process of detecting and locating a MagDot on a document.

[31936-8001 /SL032160.064] -15- 8/4/03 The large number of pixels and the corresponding high vertical pixel density on a boundary produces a large spike that is easy to distinguish from the rest of a MagDot and from the background noise.

In order to conceal or obscure a MagDot, other techniques than covering, overlaminating or broad overprinting may be used including filling some of the white regions in the pattern with non-magnetic ink, or overprinting with random or unrelated nonmagnetic ink patterns. Similarly, a hot stamping or cold foil with a magnetic medium coated on the back may be applied in a predetermined pattern to form a MagDot; and the MagDot pattern may be concealed by applying the magnetic medium in a predetermined pattern onto the hot stamping foil. A marking in the form of a pattern of magnetic ink on the back of a hot stamping foil, with the foil applied to a document in a pattern substantially unrelated to the ink pattern, provides an anticounterfeit marking that is particularly difficult to copy.

The term "magnetic material" refers to any kind of magnetically detectable material, including ferromagnetic materials, paramagnetic materials, "soft" magnetic materials and "hard" magnetic materials. Further, the term "magnetic material" includes any material that is magnetized before or after fabrication; for example, a MagDot may be fabricated of a ferromagnetic material, but not be magnetized until some later time, such as after the MagDot has been applied to an object.

Unless the context clearly requires otherwise, throughout the description and the claims, the words "comprise," "comprising," and the like are to be construed in an inclusive sense as opposed to an exclusive or exhaustive sense; that is to say, in the sense of "including, but not limited to." Words using the singular or plural number also include the plural or singular number respectively. Additionally, the words "herein," "above," "below" and words of similar import, when used in this application, shall refer to this application as a whole and not to any particular portions of this application. The word "or" in reference to a list of two or more items, that word covers all of the following interpretations of the word: any of the items in the list, all of the items in the list and any combination of the items in the list. The word "user" refers to a human being or an automatic data processing system that makes use of information or of a system. Similarly, the terms "equipment", "comparator", "reader", and "verifier subsystem" refer to any material system

[31936-8001 /SL032160.064] -16- 8/4/03 capable of performing a corresponding function, including electronics, machinery, individual human beings, optical systems, or any combination of them.

The above detailed descriptions of embodiments of the invention are not intended to be exhaustive or to limit the invention to the precise form disclosed above. While specific embodiments of, and examples for, the invention are described above for illustrative purposes, various equivalent modifications are possible within the scope of the invention, as those skilled in the relevant art will recognize. For example, while steps are presented in a given order, alternative embodiments may perform routines having steps in a different order. The teachings of the invention provided herein can be applied to other systems, not necessarily the depicted system described herein. These and other changes can be made to the invention in light of the detailed description.

The elements and acts of the various embodiments described above can be combined to provide further embodiments. All of the above U.S. patents and applications and other references are incorporated herein by reference. Aspects of the invention can be modified, if necessary, to employ the systems, functions and concepts of the various references described above to provide yet further embodiments of the invention. These and other changes can be made to the invention in light of the above detailed description.

These and other changes can be made to the invention in light of the above detailed description. While the above description details certain embodiments of the invention and describes the best mode contemplated, no matter how detailed the above appears in text, the invention can be practiced in many ways. Details of the structured magnetic pattern may vary considerably in its implementation details, while still be encompassed by the invention disclosed herein. As noted above, particular terminology used when describing certain features or aspects of the invention should not be taken to imply that the terminology is being re-defined herein to be restricted to any specific characteristics, features or aspects of the invention with which that terminology is associated. In general, the terms used in the following claims should not be construed to limit the invention to the specific embodiments disclosed in the specification, unless the above Detailed Description section explicitly defines such terms. Accordingly, the actual scope of the invention

[31936-8001 /SL032160.064] -17- 8/4/03 encompasses not only the disclosed embodiments, but also all equivalent ways of practicing or implementing the invention under the claims

While certain aspects of the invention are presented below in certain claim forms, the inventors contemplate the various aspects of the invention in any number of claim forms. For example, while only one aspect of the invention is recited as embodied in a computer-readable medium, other aspects may likewise be embodied in a computer-readable medium. Accordingly, the inventors reserve the right to add additional claims after filing the application to pursue such additional claim forms for other aspects of the invention.

[31936-8001 /SL032160.064] -18- 8/4/03

Claims

CLAIMSI/We claim:

1. An anti-counterfeit system for use with a document, the system comprising: a magnetically readable marking consisting of a predetermined, repeatable pattern of magnetic material applied to a surface of the document, wherein the magnetically readable marking comprises: a resolution of less than about 10,000 dots per inch, a resolution of greater than about 100 dots per inch, and rows and columns of pixels of magnetic material, wherein the pixels are arranged to provide a predetermined vertical density function; a reader configured to derive a first signal from the marking on the surface by reading the marking in a first direction with respect to the surface, wherein the derived first signal at least corresponds to the predetermined vertical density function, and a comparator configured to compare the derived first signal to a pre-recorded representation of the signal and provide an indication of a degree of similarity between the pre-recorded representation and a representation of the derived first signal.

2. The anti-counterfeit system of claim 1 , wherein the reader is further configured to derive at least a second signal from the marking on the surface by reading the marking in a second direction that differs from the first direction, and wherein the comparator is further configured to compare the derived first and second signals to pre-recorded representation of the first and a second signal and provide an indication of the degree of similarity between the prerecorded representations and representations of the derived signals.

[31936-8001 /SL032160.064] -19- 8/4/03

3. An article of manufacture, comprising: a magnetically readable marking consisting of a predetermined, repeatable pattern of magnetic material applied to a surface with a resolution in a range of 10,000 to 100 dots per inch.

4. The article of manufacture of claim 3 wherein the marking includes rows and columns of pixels of magnetic material, the pixels being arranged to provide a predetermined vertical density function.

5. The article of manufacture of claim 3 wherein the marking includes a predetermined vertical density function corresponding to encoded information, and wherein a surface includes a predetermined pattern of indentations that receive magnetic material to provide the magnetically readable marking, or magnetic material may be applied to a surface via impact printing to provide the magnetically readable marking.

6. The article of manufacture of claim 3 wherein the marking includes a pattern derived from an original image or sound.

7. The article of manufacture of claim 3 wherein the marking includes encoded information that is encrypted.

8. A security system for use with documents, the system comprising: an alphabet of magnetic pixel patterns, each pattern representing one corresponding magnetic ink character recognition (MICR) character and having a substantially similar vertical pixel density function to that one MICR character, but having a horizontal pixel density function substantially uncorrelated to that one MICR character, wherein one or more of the magnetic pixel patterns may be printed on a document using the alphabet, and a reader configured to:

[31936-8001/SL032160.064] -20- 8/4/03 read magnetic signals produced from the one or more pixel patterns, and interpret the alphabet of magnetic pixel patterns as standard MICR characters.

9. The security system of claim 8, wherein the one or more magnetic pixel patterns printed on a document are visually obscured wherein optical analysis and photocopying is inhibited, and wherein the reader further includes a MICR reader.

10. The security system of claim 8, wherein the reader is further configured to: decode the one or more magnetic pixel patterns by reading the vertical density functions of the random character designs in the markings and comparing them to the vertical density functions of characters in a predetermined font; and convey the decoded marking information to a user.

11. A security marking method comprising: providing a set of character patterns, each character pattern comprising an arrangement of pixels wherein an accumulation of pixels in one orientation across the character pattern provides a substantially similar value to an accumulation of pixels in the one orientation across other character patterns in the set of character patterns, and wherein an accumulation of pixels in another orientation across the character pattern provides a value substantially similar to that of a corresponding character of another set of characters; and applying a sequence of characters from the set of character patterns to an object in an optically or magnetically readable form.

[31936-8001/SL032160.064] -21- 8/4/03

12. A document security system, comprising: a set of fonts of character designs, each character design comprising an effectively random pattern of pixels such that a vertical density function of each of the random pixel patterns is substantially similar to a vertical density function of a corresponding character of a predetermined other font, wherein a subset of fonts from the set of fonts are allocated to different users, printing equipment for applying markings incorporating characters from the subset of fonts to objects, and a reader configured to read the markings from the objects and interpret the characters from the selected fonts as characters from the predetermined other font according to vertical density functions of the read markings.

13. The system of claim 12, wherein the reader if further configured to identify, track, trace, or inventory the objects.

14. A system for associating information with objects whereby the information may be automatically discemable, the system comprising: a set of characters, wherein each character of the set has a vertical pixel density function equivalent to a vertical pixel density function of a corresponding character of a predetermined other font, and wherein the set of characters further has a visual appearance selected to have effectively no human-discemable resemblance to a visual appearance of the corresponding character of the predetermined other font.

15. The system of claim 14, further comprising: an object having at least one surface bearing at least one character selected from the set of characters, applied in a form that allows automatic optical or magnetic reading of the vertical density function of the at least one character.

[31936-8001 /SL032160.064] -22- 8/4/03

16. The system of claim 14, further comprising at least one reader subsystem having a reading portion coupled to a verifier portion, wherein the reading portion is configured to read vertical pixel density functions of characters selected from the set of characters, and wherein the verifier portion includes a memory for storing a set of vertical pixel density functions of known characters from a predetermined set of fonts, and wherein the verifier portion is configured to compare the read vertical pixel density functions to the stored set of vertical pixel density functions of known characters and provide an output representing the comparison.

17. The system of claim 16 wherein each character in the set of characters further includes a differing horizontal pixel density function, and wherein the reader portion is further configured to read horizontal density functions of characters selected from the set of characters, and wherein the memory stores a set of horizontal pixel density functions of known characters, and wherein the verifier portion is configured to compare the read horizontal pixel density functions to the stored set of horizontal pixel density functions.

18. An anti-counterfeit marking comprising: a predetermined pattern of magnetizable particles applied to a substrate, the pattern forming a vertical or horizontal distribution having a predetermined overall shape, wherein the overall shape provides a timing reference for a reader wherein the reader, when reading the predetermined pattern and measuring the vertical or horizontal distribution, detects and compensates for reading distortions, and wherein the predetermined pattern of magnetizable particles and the predetermined overall shape are configured to permit the reader to compare a reading of the predetermined pattern with a later reading of the same predetermined pattern or a reading of a substantially similar

[31936-8001/SL032160.064] -23- 8/4/03 predetermined pattern, despite detected differences in the readings between the predetermined pattern and the same predetermined pattern or the substantially similar predetermined pattern.

19. The anti-counterfeit marking of claim 18 wherein the predetermined pattern of magnetizable particles is a halftone pattern of pixels, and wherein the pixels have a vertical or horizontal distribution of columns having gaps formed between columns, wherein the columns and gaps at least help provide the timing reference for the reader.

20. The anti-counterfeit marking of claim 18 wherein the predetermined pattern of magnetizable particles are modulated with a substantially constant spatial period to at least help provide the timing reference for the reader.

21. A tamper-evident article of manufacture that may be applied to a substrate, the article of manufacture comprising: a predetermined pattern of magnetic material positioned relative to a surface of the substrate, wherein the pattern of magnetic material has a spatially varying and detectable magnetic characteristic; a film over-layer positioned over the surface, and wherein the pattern of magnetic material is positioned therebetween; and a spatially varying adhesive layer; wherein a contact surface of at least the substrate or the film over-layer receives the spatially varying adhesive layer, and wherein the contact surface is near the pattern of magnetic material, and wherein the predetermined pattern of magnetic material, the film over-layer, and the spatially varying adhesive layer cooperate to form a tamper- evident article, wherein the predetermined pattern of magnetic material, the film over-layer, and the spatially varying adhesive layer are configured so that if the film over-layer is removed from the substrate, only a portion of the magnetic material adheres to the film

[31936-8001 /SL032160.064] -24- 8/4/03 over-layer, while another portion of the magnetic material remains with the substrate.

22. The tamper-evident article of manufacture of claim 21 wherein the spatially varying and detectable magnetic characteristic of the predetermined pattern of magnetic material is detected and recorded after assembly of the tamper- evident article.

23. The tamper-evident article of manufacture of claim 21 wherein the film over-layer is of an elastic material.

24. A device for reading an article, comprising: reader means for reading a magnetic tag, wherein the magnetic tag has magnetic material distributed on a substrate in a substantially predetermined way and on a scale smaller than 1/10 millimeter, memory means for storing signals; comparison means, coupled to the reader means and the memory means, for comparing a signal read from the magnetic tag by the read head means to a signal stored in the memory means; and reporting means, coupled to the comparison means, for reporting a result provided by the comparison means.

25. The device of claim 24, further comprising: an optical image means, a magnetic number reader means, or a bar code reader means, for respectively reading an optically readable number, a magnetically readable number, or a one- or two-dimensional barcode provided with the magnetic tag.

26. A printer system for producing an article of manufacture, the printer system comprising: a print module configured to apply magnetic material to a surface of an object, wherein the magnetic material is distributed on a substrate in a

[31936-8001 /SL032160.064] -25- 8/4/03 substantially predetermined way and on a scale smaller than 1/10 millimeter; a magnetic read head; a character read head for reading an automatically readable symbol that encodes alphanumeric data; a transport subsystem to provide relative motion between the magnetic and character read heads and the substrate; and a signal processing subsystem coupled to the magnetic and character read heads and configured to: convert an analog signal from the magnetic read head into a digital representation of the analog signal, generate a representation of the encoded alphanumeric data from the automatically readable symbol, and store the digital representation in a memory along with the representation of the encoded alphanumeric data.

27. The printer system of claim 26 wherein the automatically readable symbol is a bar code symbol and the character read head is a bar code read head, and wherein the memory is located remotely from the printer system, but coupled in electronic communication therewith.

28. The printer system of claim 26 wherein the symbol read head is a magnetic ink character recognition read head, and the memory is physically associated with the object.

29. A computer-readable medium whose contents cause at least one reader device to perform a method to measure 2-dimensional distribution of magnetic properties of a magnetic material distributed on at least a portion of a surface, comprising: gathering signals from the magnetic material by scanning a number N of different orientations relative to a distribution of the magnetic material in order to obtain an equivalent of N² equations, wherein the magnetic

[31936-8001/SL032160.064] -26- 8/4/03 material is provided on the portion of the surface as an array of pixels, and wherein N² is a number of pixels of 2-dimentional resolution desired; and performing a computation equivalent to solving the N² equations to determine a value of each pixel.

30. The computer-readable medium of claim 29 wherein the computer- readable medium is a memory of the reader device, and wherein the reader device includes a scanning portion having a magnetic read head with a gap comparable to a linear resolution desired for a measurement of the magnetic material.

31. The computer-readable medium of claim 29 wherein the computer- readable medium is a logical node in a computer network receiving the contents.

32. The computer-readable medium of claim 29 wherein the computer- readable medium is a computer-readable disk.

33. The computer-readable medium of claim 29 wherein the computer- readable medium is a data transmission medium carrying a generated data signal containing the contents.

34. A security marking method comprising: providing at least one structured pattern of magnetic material, wherein the structured pattern comprises a predetermined arrangement of shapes, and wherein an accumulation of magnetic material in one orientation across the structured pattern provides an automatically sensible value; applying the at least one structured pattern of magnetic material relative to a surface of an object; reading the at least one structured pattern of magnetic material; producing a signal representing the reading of the at least one structured pattern of magnetic material; and

[31936-8001 /SL032160.064] -27- 8/4/03 storing at least a representation of the produced signal in a location remote from the object.

35. The method of claim 34, further comprising: automatically reading additional data associated with the object, therein the additional data is encoded in a radio frequency identification (RFID) tag, a hologram reader, or a fluorescent tag.

36. The method of claim 34 wherein the predetermined arrangement of shapes includes a vector graphic or regions of lines and shapes.

37. The method of claim 34 wherein the predetermined arrangement of shapes includes an arrangement of pixels.

38. The method of claim 34 wherein the applying includes laser printing the at least one structured pattern of magnetic material with magnetic toner onto the surface of the object.

39. The method of claim 34 wherein the predetermined arrangement of shapes represents a digital monochrome photograph processed by way of an edge enhancing filter.

40. The method of claim 34 wherein the predetermined arrangement of shapes includes boundary edges of magnetic material to define an extent of the predetermined arrangement of shapes.

41. The method of claim 34, further comprising: visually concealing the predetermined arrangement of shapes by printing at least blank spaces between the predetermined arrangement of shapes with a matching color, non-magnetic ink, or printing the predetermined arrangement of shapes with a color that is substantially similar to a color of the surface of the object.

[31936-8001 /SL032160.064] -28- 8/4/03

42. The method of claim 34, further comprising: magnetizing the at least one structured pattern of magnetic material after the applying.

43. The method of claim 34 wherein the storing includes storing the produced signal in a location physically associated with the object.

[31936-8001/SL032160.064] -29- 8/4/03