SI9620063A - Verifier device for magnetic security thread - Google Patents

Abstract

A security thread (108) for use in a paper-based value document (104) includes a plastic substrate coated with one or more regions of 'soft' magnetic material. A device for verifying both the authenticity and the denomination of the document includes a coil (120) that is driven by an alternating current to provide a uniform magnetic field within a predetermined spatial region. As the document (104) passes in proximity of the drive coil (120), the applied magnetic field saturates the regions of magnetic material on the security thread (108). The magnetic regions provide a response magnetic field that is a non-linear response containing a component at the fundamental frequency and various harmonic frequency components. A receive coil (124) senses the response magnetic field. A signal processor connected to the receive coil (124) utilizes the response signals at the fundamental frequency and the harmonic frequencies to determine the denomination of the document (104).

Description

The present invention relates to security threads for securities with a basis of paper, such as banknotes and securities, and more specifically to a device for detecting security threads, and thus for determining the authenticity of a document.

According to the prior art, there are numerous approaches for verifying the authenticity of paper-based securities, such as securities and banknotes, bank checks, stock certificates, etc. These or other procedures may also be used to verify the characteristics of documents such as the value of banknotes. This way different properties of documents of the same general type can be verified. However, the verification of the value of paper money may also be interpreted as the verification of authenticity i.

All known approaches to verification are based on the detection and / or measurement of document specific physical properties or patterns. Typically, the property to be detected is intentionally added to the document during its creation as part of the document's recognition system or anti-counterfeiting verification system. The device used to validate the type of security feature that is added to the document, as well as the separation between different document features (as indicated by certain properties designed in the security property type), is usually designed together with the physical characteristics of the security property. This should ensure optimum functionality when verifying the document.

2General approaches include the use of magnetic ink, which is printed at predefined locations and in predefined patterns on the surface of the paper. Another approach is for the substrate of the plastic protective thread, which is covered with predetermined samples of conductive and / or magnetic materials, to be either partially or fully embedded in the paper for money. The detector is then designed to detect the material type and, to a limited extent, the spatial distribution of the material on the filament substrate.

More specifically, the use of magnetic materials according to the state of the art in the field of document protection consisted exclusively of relatively hard (that is, with high magnetic coercivity) magnetic materials. The magnetic material may be formed as part of an ink printed on the surface of a document, or may be applied to the surface of the document in some other form, or may be covered on a plastic substrate of a security thread embedded in the document.

The detection of these relatively solid magnetic materials (and thus the verification of the authenticity of the document and / or some of the resulting characteristics) is typically performed by exposing the material to a magnetic field and then detecting remanent magnetism. The magnetic field may be pressed against the magnetic material either at the time the document is produced or by the detection system itself immediately before reading or by detecting remanent magnetism; for example, during a commercial sales transaction or during bank sorting of banknotes. Examples of relatively rigid magnetic material in the aforementioned applications include magnetic dust, such as ferrites or thin sheets, or strips of blood-stabilized magnetic material a, such as nickel. (See U.S. Pat. No. 4183989.) Magnetization patterns e

3 easily written on materials and patterns can read reading heads, reading heads are capable of reading either one-way (D.C.) magnetization (such as Hall effect detection) or can use a time-varying magnetic field generated by the movement of a banknote past the reading head. In both cases, only pure remanent magnetism is measured. This approach requires the use of strong magnetic fields for pre-magnetisation and sensitive reading heads for detection. A limitation is the fact that the detection of the magnetic material must be carried out in close proximity (the distance between the reading head and the magnetic material is much less than 1 millimeter). Examples of access to these hard magnetic document verification materials are provided in EP 0295229, W0 92/08226, EP 0319524, EP 0204574, EP 0428779, W0 91/04549, GB 2130414, W0 91/10902, EP 0413534, and in US Patent 3870629 .

In contrast to hard magnetic materials and their use for document security, the use of relatively soft magnetic materials (i.e., low magnetic coercivity) in electronic item control (eg item theft in retail stores) is known. Compared to hard magnetic materials, soft magnetic materials are more easily magnetized from a distance with a relatively weak magnetic field pressed. A typical application includes a retail item that has a sticker or label made of a soft magnetic material (such as an iron magnetic material) that is attached to it. if the item is lawfully purchased, a store employee either removes the tag or causes it to change in its magnetic characteristics. However, if the item is attempted to steal, it reaches a magnetic field that is pressed in the outlet of the store, a designation which then issues or

4of characteristic, distinctive signals. These signals can be used for an audible alarm to alert store staff to try the theft.

These state-of-the-art applications include the detection of marked objects, essentially in any position or orientation, in a relatively large volume of space. The soft magnetic material contained in the marking has high magnetic permeability; thus, it is easily pushed into the saturation of a time-varying alternating (A.C.) pressed magnetic field. The saturated magnetic material, in response, gives non-linear magnetic fields containing higher harmonic frequencies relative to the frequency of the field pressed.

A problem with a known control system arises from the requirement to control a large space. Common magnetic objects, such as keys, are different from magnetic tags in that they have lower magnetic permeability. Thus, ordinary objects emit relatively less higher harmonic signals (at lower frequencies) than are emitted by a highly permeable object. In order to correctly distinguish highly permeable soft-magnetic material (for designation of objects) from low-permeable soft-magnetic material (house key), the electronic object monitoring system must detect and process higher harmonic frequencies. However, the problem is that much less energy is present in higher order harmonic frequencies than in lower order harmonic frequencies. Therefore, the detection system tends to become relatively complicated.

In addition, to achieve a plurality of distinctly recognizable objects, it contains a limited number of electronic control systems for articles of several discrete magnetic elements. Each element gives a slightly different response to the relatively uniform (spatially) query and read fields of the detection system. In this way, when a seemingly uniform query field is pressed on a label or tag, a plurality of response characteristics of the magnetic response field can be decoded to determine the identity of the label. Separate characteristics can be identified as frequency or as a threshold of magnetic intensity. According to the prior art, no known attempt has been made to obtain spatially resolvable data from anti-theft properties using high-resolution reading methods. This is because anti-theft applications require a detector coil of much larger characteristic dimensions, such as the size of a recognizable property (i.e., labels).

Examples of systems and their electronic control components for articles of prior art are described and illustrated in EP 0295028, WO 88/09979, EP 0611164, EP 0352513, French Patent Specification 763681, and in US Patents 3665449, 3747086, 3790945, 3292080, 4074249 and 5005001.

Accordingly, the first object of the present invention is to verify the authenticity and / or to determine the value of a paper-based document such as money or banknote paper having an embedded magnetic filament security thread.

It is a general object of the present invention to check a security thread with a magnetic field signal and to determine the authenticity and / or value of paper from a non-magnetic magnetic response signal.

It is a further object of the present invention to provide a security thread with one or more areas of soft magnetic material, wherein the thread is typically fully embedded in a paper-based document and provides a device that does both, verifies that the magnetic filament material is a predetermined type and detects the spatial distribution of the magnetic material, thereby determining the characteristic of the document, such as a value.

A second object of the present invention is to provide a non-contact verification device for detecting the type and distribution of magnetic material on a security thread using a query magnetic field.

It is a further object of the present invention to impose, from a non-contact source, an alternating magnetic field on a security thread covered with soft magnetic material with predetermined patterns, and detect a magnetic field re-emitted by a security thread, and determine one or more characteristics of the document from the detected field into whose security thread is embedded.

The foregoing and other objects and advantages of the present invention will become more apparent from the following description and from the accompanying drawings.

Content of the invention

In order to avoid the drawbacks of the prior art and to achieve the above objectives, the applicants have invented a device for verifying both the authenticity and value of the banknote, which has an integrated protective thread with magnetic materials. Preferably, the safety thread contains a thin rectangular plastic substrate that is completely embedded in the paper. To one or both

7On the opposite surface of the substrate may be applied soft magnetic material (i.e., lightweight to magnetize) in predetermined spatially distributed patterns, which are characteristic, for example, of the value of banknotes. Different banknote values may be indicated by different spatially distributed patterns of magnetic material.

According to a first aspect of the present invention, the type of soft magnetic material used in the security threads is determined by traveling a bank having an embedded security thread in the non-contact vicinity of the coil with a wire connected to an alternating frequency signal. The drive coil creates an alternating drive magnetic field, which is very uniform due to the location and size of the drive coil. The field strength of the driving magnetic field is sufficient to push the magnetic material on the shielding thread into saturation. The magnetic field response generated by the magnetic material is nonlinear and therefore contains higher harmonic frequency components. The detection coil detects the response magnetic field and converts the various frequency components into electrical signals. These signals are demodulated and investigated for the phase and 90 ° phase-shifted amplitudes of the components of both signals, linear or fundamental (that is, a response signal of the same frequency as the drive signal) and a third harmonic frequency relative to the fundamental signal, to determine the type of material. For example, for certain types of soft magnetic materials, under special conditions of magnetic excitation, it is known that the signal amplitude of the third harmonic frequency must be above a certain threshold, while at the same time the amplitude of the fundamental signal must be below a certain but different threshold. It must also be the ratio of the amplitudes of the third harmonic frequency and the fundamental frequency in a given range.

Thresholds and area are known and unique to each different type of soft magnetic material.

According to another aspect of the present invention, the detectable coil used in the first aspect of the present invention is of uneven spatial orientation (i.e., highly localized) relative to the thread. Such a high degree of localization is achieved by requiring that at least one dimension of the coil is much smaller than the overall length of the protective thread and is preferably smaller than the length of the smallest magnetic filament area. The magnetic drive field is preferably pressed at a 45 ° incline relative to the dimension of the height of the protective thread (that is, if there are any signs in the magnetic material on the protective thread, the drive field is pressed at a 45 ° angle). This angular orientation preferably allows only one magnetic region to be examined at a time in the security thread. This ensures the correct resolution for detecting the spatial distribution of magnetic material areas on the security thread, thus permitting the determination of banknote values.

In a similar manner to the first aspect of the present invention, the resulting magnetic field signals re-emitted by the shielding thread are broken down to the fundamental and third harmonic frequencies, and both phase and 90 ° phase-shifted components are signaled with a signal processor to determine value. One method of determining value is to compare the resultant signal characteristic of the detected spatial distribution of magnetic material on a security thread with a plurality of signals stored in memory and characterized by different valid spatial distribution patterns.

Brief description of the drawings

1 is a perspective view of a security thread to which a magnetic material is attached, which is mounted as a security feature within a value document with a paper base;

Figure 2 is a perspective view of an alternative embodiment of the security thread of Figure 1;

3 is a plan view of another alternative embodiment of the security thread of FIGS. 1 and 2;

Figure 4 is a perspective view of the drive coil and the receiving coil mounted on the ferrite core, together with a banknote containing the security thread of Figures 1-3 and traveling past the installation of the coil and receiving coil;

Figure 5 is a top view of the installation of the drive and receiving coils of Figure 4;

Figure 6 is a final view of the installation of the drive and receiving coils of Figure 4-5;

Figure 7 is an alternative arrangement of the drive and receiving coils;

8 is a schematic block diagram of an electronic circuit connected to both the drive and receiving coils of FIGS. and

Figure 9 is a more detailed schematic diagram of one of the components in the block diagram of Figure 8.

DETAILED DESCRIPTION OF THE INVENTION

Referring in detail to the drawings, the device for verifying the authenticity and / or characteristics (i.e. values) of value documents with a paper base on them is illustrated and generally designated by reference number 100. The device 100 is intended for use with document 104, such as a banknote or a security that has a security feature in the form of a security thread 108. The thread 108 contains a plastic substrate 112 that is fully embedded in the paper 104. On one surface of the substrate 112, soft magnetic material 116 is applied in predefined patterns. During operation, a document 104 containing a security thread 108 near the coil 120 travels through a wire through which an alternating current flows, creating a magnetic field in a predetermined region surrounding the drive coil 120. A receiving coil 124 is mounted near the drive coil. connected to the electronic processing circuit 128. When the document 104 with the security thread 108 travels past the drive coil 120, the pressed magnetic field pushes the soft magnetic material 116 on the substrate 112 of the security thread into saturation. Magnetic material emits a non-linear response field containing different frequency components on the security thread, one of the components being the same frequency as the magnetic field pressed, and the other frequencies are multiples of the frequency of the magnetic field pressed. The receiving coil 124 detects different frequencies of the response magnetic field and provides appropriate electrical signals. These electrical signals are processed by the electronic circuit 128 in a predetermined manner by definitively determining both, the type of magnetic material 116 and the spatial distribution of the magnetic material 116. In this way

11, the device 100 can authenticate the document 104 and also determine its characteristic such as value.

Referring to Figures 1-3, the security thread 108 preferably comprises a plastic substrate 112 with at least one security property utilizing a soft magnetic metal located on at least one surface of the substrate. However, it should be understood that this preferred embodiment of the protective thread is given explicitly by way of example only. Instead, the document may have a security-related feature, if desired, a tile or tablet or the like. Regardless of the actual protective property chosen, the common feature of each property is the type and spatial distribution of the magnetic material 116. In the case of protective thread 108, the plastic substrate is only the medium carrying the magnetic material 116.

A preferred embodiment of the security thread 108 comprises a plastic substrate 112 which has two security features: the first security feature optionally comprises a recurring pattern of soft magnetic metal; the second security feature contains magnetically and / or nonmagnetic metal-shaped signs 136. Optionally, the repeating pattern 132 of the first security feature comprises at least one soft-magnetic metal region 140 and at least one separation region 144, such regions being optionally in alternating sequences in sample 132 extending along the length of the plastic substrate 112. The separation area (s) 144 allow the metal regions 140 to act apparently magnetically independently of one another when the magnetic filament 108 is subjected to a magnetic query scheme, which will be described in further detail in accordance with the device 100 of the present invention. That is, the characteristics of the detectable region of the detectable region, if any, are not confused with the differences of the detectable signals generated by the metal regions 140.

The inspected magnetic metallic materials 116 for use with shielding threads 108 are soft magnetic metals having a low efficiency of less than 5000 amperes / meter (A / m) when measured with an AC magnetometer at frequencies of about 10 kHz ( kHz) to about 100kHz. Preferred soft magnetic metals have coercivities between about 50A / m and about 5000A / m, and more preferably between about 100A / m and about 2000A / m. These preferred soft-magnetic materials exhibit robustness and resistance to mechanical deformation. They also have a high intrinsic relative permeability of from about 200 to about 100,000. Metals reach saturation at low magnetic fields of less than 10,000A / m and have a sufficiently high magnetic nonlinearity to obtain measurable harmonic signals while investigating magnetic properties with a forced magnetic field with medium distance (that's 1 to 2mm).

Preferred soft-magnetic metals include amorphous metallic glass materials, such as, for example, amorphous alloys of soft-magnetic metals, which include alloys with a base of 1 ez / e 1 j and a cobalt / nickel base. Suitable cobalt / iron alloys are available from Vacuumschmeltze Gmbh, Postfach 2253, D-63412, Hanau ”, Germany under commercial designations: Vacuumschmeltze 6025 (66% cobalt (Co), 4% iron (Fe), 2% molybdenum (Mo ), 16% silicon (Si) and 12% boron (B)); Vacuumschmeltze 6030 (similar to Vacuumschmeltze 6025, about 70% Co, minor ingredients unknown); and Vacuumschmeltze 6006 (46% Co, 26% Ni, 4% Fe, 16%

-13Si and 8% B). Suitable iron / nickel base alloys are available from Aliied-Signal, Inc., Parsippany, NJ 07054 under the trade names: Allied Metglas 2714 and 2704. Such materials give an amorphous structure under certain application conditions.

There is no limit to the examined magnetic metals for use with another protective property of the safety thread and include both soft and hard magnetic metals. Non-magnetic metals examined for use on filaments include aluminum, nickel and silver, with aluminum being preferred.

In Figure 1, the pattern 132 of the security thread 108 comprises a magnetic metal region 140 and an adjacent separation region 144, in which both areas assume a rectangular shape. Metallic markings 136 are affixed to both, in the magnetic metal field 140 as magnetically metal shaped signs and in the punctuation area 144 as metallic marks. In Figure 2, sample 132 comprises three magnetic metal regions 140 of increasing thickness, providing regions with different magnetic strengths, among them are corresponding separating regions 144 which assume the configuration of the dollar sign. Separation areas 144 are located in and between each magnetic metal region 140. In other words, metal shaped signs that adopt the dollar sign are of the same size as the separation areas 144 and are intended to completely separate (in Figure 2) the metal regions 140. An expression of the same scope as used herein means that the subject areas 140, 144 and the signs have the same spatial boundaries.

In Figure 3, the magnetic metal region 140 is the first protective property and the second protective property of the same scope. For example, metal-shaped signs of a second protective property are magnetic metal signs that form a magnetic metal region (s) of the first protective property.

The plastic substrate 112 may be made of any transparent or translucent material, which is preferably a non-magnetic and non-conductive material. Such materials include polyester, regenerated cellulose, poly 1 to 1 ori and other plastic films, the preferred material being polyester. Such films remain intact during the paper-making process and preferably have a width in the range of about 0.5 millimeters (mm) to about 3.0mm.

As previously described, the optional repeating pattern 132 of the first protective property of the present invention comprises at least one soft-magnetic metal region 140 and at least one separating region 144, optionally in alternating sequences, in pattern 132 extending along part or the entire length of the plastic substrate 112. Other sequences examined include blocks of a plurality of magnetic metal regions 140 that use different amounts of magnetic metal and are separated by separating regions 144. Each metal region 140 contains different amounts of magnetic metal material. Where the separation regions 144 serve in a manner that allows the regions 140 to operate apparently magnetically independent of each other, the separation regions 144 may be in the form of an area without magnetic metal or may be in the form of an area with reduced magnetic metal content or surface coating in comparison with magnetic metal regions 140. The magnetic metal region (s) 140 and the separation region (s) 144 can assume any

15form or configuration.

Where the shape (that is, the size and thickness) of the magnetic metal regions determines the magnetic response, both through the influence of a certain permeability phenomenon and the effect on the magnetic coercivity with thickness, it is preferred that each magnetic metal region 140 has a thickness in the range of about 0. 01 to about 10 microns and more preferably a thickness of from about 0.10 to about 0.50 microns. It is also preferred that each magnetic metal region 140 has a length along the side edge of the plastic substrate 112 in the range of about 0.1mm to about 5mm. Magnetic metal regions 140 having the dimensions listed above are expected to exhibit the form of a conditional value of magnetic permeability in the preferred range of 200 to 10000. Such high permeability allows the magnetic metal to easily reach saturation in weak magnetic fields, moreover, saturation which generated in individual fields provides a further means of authentication.

Another security property of thread 108 may be a separate and / or equally public security property and cover magnetic and / or non-magnetic metallic shaped markings 136, such as a metal font or a transparent font defined by metal borders. In detail, magnetic metallic signs or transparent font may form part of any magnetic metal region 140 and punctuation area 144 and / or may form a separating area (s) 144. On the other hand, magnetic metal signs or magnetic metal script 136 may form a magnetic metal region ( areas) 140 and / or part of each separation area 144. Likewise, non-magnetic metal signs or non-magnetic metal-shaped marks 136 may form part of the separation area (s) 144. In a preferred embodiment, where security thread 108 is embedded in security paper 104, they can create marks 136 an expression or phrase that is not easily distinguishable in reflective lighting but becomes readable to the person viewing it in translucent lighting. The apparatus 100 of the present invention, which will be described in detail below, verifies only the first protective property (i.e., magnetic metal regions) and not the other protective properties (i.e., marks).

The first and second protective properties can be formed by applying metal 116 to a plastic substrate 112 by any of a number of processes, including, but not limited to, selective metallization by electrically deposited, direct hot printing on the substrate, or the use of a mask or template in a vacuum metallizer , and processes containing metallization, followed by selective demetallization with chemical etching, laser stripping and the like.

Methods containing metallization followed by selective demetallization are preferred. A. The metallization or deposition processes examined include the ejection of, for example, planar magnetron bursts, from electron beam or thermal radiation and electrolytic chemical deposition in addition to organic metal pyrolysis of vapors. A preferred metallization or deposition technique is selection.

Discharge is a process of physical vapor deposition that takes place in a vacuum chamber, where gas ions (such as argon) are accelerated by an electrical potential difference of sufficient strength to eject atoms from the target. The broken atoms travel through the partial

17 Vacuum until they enter the surface (for example, plastic substrate 112) on which they can condense and form a coating. The target used in the ejection process (for example, an alloy capable of forming amorphous metal glass) is prepared by spraying plasma from the melt. The applied material should not be shattered after application.

Selective demetallization techniques examined are techniques where the applied material is selectively removed from the target surface. As mentioned above, these techniques include chemical etching and laser removal. Grinding and lifting away are also included. The lifting technique uses selective removal of the applied material by selective adhesive application followed by removal of the adhesive on the support. Preferred techniques are chemical etching and laser removal.

Chemical etching can be performed by selectively printing a protective layer, followed by chemical etching using a suitable etching agent such as ferric chloride or a mixture of fluoric hydrogen saliva / nitric acid.

In order to achieve different thicknesses at magnetic metal regions 140, as shown in Figure 2, a technique for etching the entire thickness of the metal layer (s) may also be used, including an etching technique that only partially removes the initial thickness of the applied material. .

Laser removal can be performed with reduced laser power, whereby the soft-magnetic metal of the present invention crystallizes from an amorphous state when heated to temperatures from about 350 ° to 400 ° C. The resulting morphological fracture is typical

18Cause the material is split and crushed. Accordingly, the need for power is reduced compared to the need inherent in laser removal of vacuum-applied aluminum.

In addition to the above, conventional thermal contact printheads reaching temperatures of about 350 ^e C to about 450 ° C and resolution (dpi) up to about 300 dpi (2.54 cm) can also be used to control recrystallization a of the material used, thereby causing material to be removed or etched.

Protective thread 108 may include, in addition to magnetic metals, additional layers or coatings. The additional layers or coatings examined include plastic protective outer layers to make the thread less susceptible to chemical influences, and reflective metal layers and camouflage coatings designed to make the thread less visible under reflective light when the thread is embedded into protected paper, such as banknotes. Glue layers are also included to allow the thread to be embedded in or on a secure document.

Once a composite sheet containing the protective properties is prepared as described above, the sheet can be cut into the safety threads using conventional techniques or split into a large number of tiles by a suitable matrix cutting process.

Security thread 108 may be introduced into security securities 104, such as securities, during their manufacture. For example, if the thread 108 is in the form of a tile, it can be pressed (optionally with adhesive) on the surface of the partially cured paper

-19 tape, resulting in the surface mounting of such tiles. On the other hand, it has a protective property in the form of a security thread 108, a substrate 112, which is covered with a magnetic material 116 and can be incorporated into wet paper fibers as long as the fibers are still flexible and do not harden, as claimed in US patent 4534398. This results in that thread 108 is fully embedded in fabricated paper. Thread 108 can also be inserted into a cylindrical mold of a paper-making machine, a cylindrical dyeing tub, or similar known machines, resulting in the partial embedding of thread 108 into the body of the fabricated paper (i.e., the threaded window paper). Additionally, thread 108 can be mounted on the surface of the secured papers or, inter alia, after finishing.

Referring now to Figure 4, it illustrates a banknote or security 104 having a security thread 108 fully embedded therein, which travels past the drive coil 120 and the receiving coil 124 (typically no more than ten (10) millimeters from receiving coils 124 and, if possible, from the coil 120). The arrow head 148 in FIG. 4 shows that the banknote 104 is scanned in the narrow edge direction with respect to the long dimensions of the windings 120, 124 (i.e., the shorter edge 152 of the paper 104 is the leading edge in the scan direction). The security thread 108 is embedded in document 104 such that the height of the marks 136 is coaxial with the paper feed direction.

The drive coil 120 comprises a first coil of wire wound around a soft magnetic sintered ferrite core 156. The receiving coil 124 is embedded in a piece 160 of insulating material (Figure 6) and contains a single coil (i.e., a single winding) of wire. Figures 4-6 illustrate the spatial arrangement of the two coils 120, 124 with respect to the ferrite core 156.

20 The use of the ferrite core 156 together with the drive coil 120 permits the pressed magnetic field generated by the drive coil to launch it into predetermined spatial positions that give good uniformity and strength to the pressed magnetic field. Ferrite core 156 also permits the use of smaller electric currents than those required by air coils to provide a magnetic field. Thus, battery-powered devices reduce power consumption. It also permits the use of ferrite core 156 so that the windings of the drive coil can be located away from the query or pressed magnetic field (more specifically, they may be located away from the windings of the receiving coil). This makes it possible to reduce the coupling due to the stressed capacitance between the drive and receiver circuits, as described below. Also, the capacitive assembly is reduced if the number of wrappers in the receiving coil 124 is relatively low. The preferred embodiment only uses a single coil coil. Alternatively, more than one receiving coil 124 may be used.

The drive coil 120 and the receiving coil 124 of FIGS. 4-6 are located only on one side of the banknote 104. It should be understood that the installation is shown by way of example only. One-sided application and detection may be required where ergonomic or feed or space constraints outweigh the potential benefits of bilateral winding installation 120, 124. Bilateral installations where propulsion and receiving coils on either side may be used instead ( is on opposite sides of the banknote). Bilateral arrangement of coils generally permits greater separation between the drive and receiving coils 120, 124, thereby minimizing the capacitive assembly of magnetic fields, which is due to the stressed capacitance. Likewise, bilateral coil placement generally gives the resulting magnetic field strength of the response magnetic field, which is less sensitive to the spatial placement of document 104 inside the slot in the receiving coil 124, and which is generated by the magnetic metal regions 140 of the protective thread 108. Alternatively, the drive coil 120 may be mounted on one side of the paper 104, while the receiving coil 124 may be mounted on the other side of the paper.

Also, Figures 4-6 illustrate the placement of the drive / receiving coil at an angle of, for example, 45® with respect to the length dimension of the security thread inside the banknote. Again, this is shown explicitly as an example only. Such an angle allows the thread 108 to be examined so that each of its magnetic regions 140 is examined only one at a time, which is achieved by the installation of drive / receiving coils. However, this 45® ratio also allows the pressed magnetic field to be partially oriented in a rectangular direction relative to the thread.

Referring now to Figure 7, it illustrates the bilateral installation of air propulsion and receiving coils 120, 124. This arrangement provides a highly uniformly pressed magnetic field on the security thread 108 of the banknote 104. Generally, the strength and direction of the magnetic field pressed have a strong influence on the relative amplitudes of any resulting higher harmonic signals within the response magnetic field generated by the magnetic fields 140 of the security thread 108. Thus, it is generally required that the pressed magnetic field be relatively uniform across any

-22spatial position in which a note can be 104 positional wound. For example, the pressed magnetic field should be relatively even across any slot in the detection head in which the banknote may be shaken due to the transport device mechanism (not shown) used to move the banknote relative to the drive and receiving coils 120, 124. Further , as can be seen from Figure 7, the main planes of the drive and receiving coils 120, 124 are at right angles. This prevents any direct assembly of magnetic fields between the coils.

The arrow head 164 in FIG. 7 shows the direction of travel of the banknote relative to the coils 120, 124. Likewise, not shown in FIG. 7, in the embodiment given as an example, the banknote 104 is oriented relative to the coils 120, 124 so that the width dimension is or edge 168 of the paper (Figure 4) the leading dimension of the trip. Also, although not shown in FIG. 7, the protective thread 108 is oriented at an angle of 45 'with respect to the length dimension of the drive and receiving coils 120, 124. This is for the same reasons as given above with respect to the ferrite core 156 and the placement of the coils. Further and most importantly in reading the spatial distributions of the magnetic regions 140 of the security thread 108, the narrow dimensions of the receiving coil 124 of Figure 7 (i.e., the distance between two parallel strands of wire of either the upper or lower receiving coil with a single sheath) are shorter than the shortest the length of any magnetic field 140 of the security thread 108. This allows individual and discrete magnetic field signals to be obtained from the receiving coil, with each signal received containing information about a magnetic characteristic of only one of the corresponding magnetic fields 140. The resulting information is used in determining specific characteristics of the document 104, as indicated by the spatial distribution of the magnetic regions 140 on the substrate 112 of the security thread. For example, when a document 104 is a security or a note, a defining characteristic is a value. The determination of value is described in more detail in what follows.

Referring now to FIG. 8, a schematic block diagram of the electronic circuit 128 is shown, which is an interface between the various coil actuators received / received, some of which are described above in FIGS. 4-7. Both the drive coil 120 and the receiving coil 124 have adaptive transformers 172, 176 which reduce the effect of the capacitive assembly relative to the inductive assembly. Likewise, the impedance of the adaptive transformer 172 used in conjunction with the drive coil 120 may reduce the applied voltage for the drive coil. Further, but not shown, a capacitor can be connected to the receiving coil to create a resonant circuit. The use of a resonant circuit improves the signal-to-noise ratio and the projected ratio of the tuned frequency to the non-tuned frequency when detecting this single harmonic frequency. However, if the electronic circuit 128 is used to detect more than one harmonic frequency, the resonant circuit is less useful and the capacitor is not generally used.

The electronic circuit 128 also includes a frequency generator 180, which typically generates different signals at specific frequencies. The frequency generator 180 provides a pair of AC (signal) signals on the signal bus 184 to the switch and amplifier stage 188. The frequency generator 180 may comprise individual components arranged in a well-known manner to generate signals for amplifier 188. On the other hand, the frequency generator 180 may, it contains a digital application specific integrated circuit (ASIC) if desired.

The two drive signals provided by the frequency generator 180 are described in detail below. These two signals are amplified by amplifier stage 188, then fed to isolation transformer 192 and then to filter and tuning block 196. The filter may comprise an LC bandpass filter that allows only frequencies within a certain range to be fed to transformer 172 to equalize impedances and then to drive coils 120 in order to reduce the amount of harmonic components in the signal to be fed to the drive coil 120.

The frequency generator also provides a plurality of signals on the signal bus 200 to the synchronous detector stage 204. The synchronous detector stage 204, shown in more detail in FIG. 9, contains a plurality (i.e. 4) of identical mixing stages 208 signals and 4-pole low band active filters 212 Each mixing stage may contain a commercially available Model DG411. In the example given, the frequency generator on the bus 200 provides the first signal, which is an alternating frequency signal of 40kHz. The second signal on bus 200 also has a frequency of 40kHz, but is phase shifted by 90® relative to the basic sophisticated signal obtained by the first mixing stage 208. The frequency generator 180 also provides a signal with a frequency of 120kHz having the same phase as the base signal . This, the third signal, has a frequency that is three times that of the base signal and is also coherent with the 40kHz base signal. Finally, the generator 180 provides a fourth signal, which is also at a frequency of 120kHz and is phase shifted 90® by ~ 25 ~ to a 120kHz phase signal. These four signals from the frequency generator 180 on the bus 200 are fed to the respective mixing stages 208 and filters 212 within the synchronous detector 204.

Also, each mixing stage 208 is supplied as a separate input response signal on signal bus 216, which is coupled to a plurality of corresponding low noise amplifiers 220. Each amplifier may comprise a commercially available Model AD826. Also included within the low noise amplifier stage 220 are the corresponding high impedance low noise amplifiers, each of which may contain Model AD797. The inputs of these amplifiers 220 are connected to signals from the receiving coil 124, which came from the corresponding transformer 176 to adjust the impedances.

Each mixing stage 208 inside the synchronous detector 204 operates by eliminating, by means of a known demodulation scheme, signal information magnetically detected by the receiving coil 124 from the frequency of the pressed signal to the drive coil 120. The individual outputs of the four mixing stages 208 are then present at individual signaling coils. lines containing a signal bus 224 that is connected to the analog-to-digital converter 228. The digitized output from the analog-to-digital converter is fed to the signal processor 232, which may contain a known microprocessor circuit. The signal processor, described in detail below, works by determining the validity of a document traveling past the drive coil 120 and the receiving coil 124 from data, if any, read from the magnetic metal regions 140 of the security thread 108. Finally, the output signal from the signal processor 232 may lead, for example, to a display or money sorting device 236 or to other types of user systems.

During operation, the frequency generator 180 provides two signals on the bus 184 to the amplification stage 188. These are rectangular AC signals of 40kHz frequency. The first rectangular signal has a phase shift of +120 'with respect to 40kHz, a phase signal given by a frequency generator 180 to the synchronous detector 204. The second rectangular signal with a frequency of 40kHz delivered to the amplifier stage 188 has a phase delay of -120 * relative to The 40kHz phase signal provided by the generator 180 to the synchronous detector 204. Although by chance only, the use of these two rectangular phase signals, which are 120 ° phase shifted, ensures a reduction in the price of the components used in the electronic circuit 128 without affecting the quality. Since the normal rectangular signal contains a plurality of third harmonic frequency components, the likelihood of unwanted shaking assemblies of such harmonic components from the drive coil 120 to the receiving coil 124 is eliminated by combining two signals to obtain a pseudo-rectangular signal pressed on the drive coil 120, and is free from the content of the third harmonic component.

A rectangular 40kHz signal is pressed on the drive coil 120 to create an alternately pressed magnetic field that is very uniform due to the physical construction of the drive coil 120 described above with respect to the embodiments of Figures 4-7. The frequency of the drive signals pressed on the drive coil 120 has an exemplary value of 40kHz here. However, the preferred range is between 500Hz and 500kHz and the most preferred range is 10kHz to about 100kHz. At the lower ones

-27frequencies, the signal amplitude is low, so that the achievable signal-to-noise ratio is one of the limits for frequency. The frequency must also be high enough that each distinguished magnetic metal region 140 of the protective thread 108 is measured during at least a few periods of the pressed magnetic field. For example, for fast sorting machines used in banks, the typical feed rate is 10 meters per second, which dictates a frequency of at least 10kHz, and preferably about 40-50kHz. On the other hand, with increasing frequency, the apparent magnetic coercivity tends to increase for most materials. The apparent coercivity should be low enough to push the magnetic material into the saturated magnetic field. Otherwise, the desired high degree of nonlinearity in the response magnetic field does not occur. Coercivity and the driving magnetic field must be reasonably low in order to maintain sufficient difference from conventional magnetic materials such as house keys. In the preferred embodiments described herein, the apparent coercivity of magnetic metal regions 140 is between 500 and 750 amperes per meter and the amplitude of the drive field is about 1000 amperes per meter.

In operation, when the offered banknote 104 with protective thread 108 travels past the non-contact proximity of the drive coil 120 and the receiving coil 124 (preferably within a distance of less than ten (10) millimeters), the pressed alternating magnetic field of frequency 40kHz pushes into saturation the magnetic metal regions 140 protective threads. These magnetic metallic regions then in turn emit a response magnetic field containing different frequency components because the metallic regions 140 are saturated due to the magnetic field being pressed. That is, the response magnetic field generated by the magnetic metallic regions 140 contains a fundamental component at a fundamental frequency of 40kHz.

The response magnetic field also contains different frequency components of harmonic frequencies or multiples of the fundamental frequency. The electronic circuit 128 of the present invention is in a preferred embodiment designed to detect a third harmonic frequency (i.e., 120kHz) relative to a fundamental frequency of 40kHz. The third harmonic frequency is a relatively low-order harmonic component, which is preferable because lower-order harmonic frequencies typically generate more signal energy than higher-order harmonic frequencies. Oddly numbered harmonic components are also preferred because they are generated more than even numbered harmonic components due to the absence of any significant DC magnetic field. However, it should be understood that any harmonic component can be used in a device similar to the device 100 of the present invention. However, the use of a third harmonic component, as described herein in a preferred embodiment, provides a significant advantage in signal-to-noise ratio compared to the use of relatively higher-order harmonic components.

The various frequency components of the response magnetic field generated by the magnetic metal regions 140 of the security thread 108 are detected by the receiving coil 124 and finally reach the stage 204 of the synchronous detector. The amplitude or magnitude of each of the four signals described above is demodulated by a synchronous detector and digitized by an analog-to-digital converter 228 and sent to the signal processor 232. These four signals consist of phase and 90 ° phase shifted 40kHz baseband signals, together with phase and for 90 'phase shifted third harmonic frequency signals of 120kHz. The signal processor operates to determine, in accordance with one aspect of the apparatus 100 of the present invention, the type of magnetic material 116 contained in the magnetic filament material 140 areas 140. In an exemplary embodiment, the signal processor 232 determines a series of magnetic material regions 140 by comparing the signal amplitude of the third harmonic frequency relative to the fundamental frequency with a certain level stored in memory associated with the signal processor 232. The amplitude of the sophisticated component of the signal of the third harmonic frequency relative to the fundamental frequency indicates the use of valid magnetic material in magnetic metallic regions 140 if the amplitude of this signal above a certain threshold, which is a known value corresponding to the type of magnetic material 116. This ensures that a highly non-linear magnetic material 116 is present on the security thread 108.

The second component of the test contains a comparison of the amplitude of the phase frequency component of the fundamental frequency with a predetermined threshold. Again, the threshold is known and unique to the type of magnetic material used 116. Conditions apply when the amplitude of the fundamental frequency component is below a certain level. This test ensures that no excess magnetic material is present on the surface of the protective thread due to the attempt to falsify a nonlinear characteristic on the counterfeit banknote 104. The third test performed by the signal processor 232 is to compare the amplitude ratio of the sophisticated third harmonic component with the amplitude of the sophisticated fundamental frequency with the range of values , which are stored in memory associated with the signal processor 232. This test ensures that the correct degree of nonlinear versus linear behavior is present. Most conventional magnetic materials used by counterfeiters will have a very low level in this third test. On the other hand, genuine soft magnetic materials 116 used for the magnetic metal regions 140 of the protective thread 108 will generate a higher level of ratio in this test. This ratio is typically determined experimentally by experimentation with the use of special measuring equipment and depends on the specific magnetic materials used and their quantity and configuration.

The signal processor may then indicate the results of these tests by providing relevant information on the banknote display or sorter 236. As a further test of the validity in the magnetic metal regions 140 of the magnetic material 116 used, the security thread 108, the device 100 of the present invention can use the amplitude for 90 "phase-shifted signal components of either the fundamental frequency component or the third harmonic component to determine the magnetic coercivity of the material 116. Specifically, the signal processor 232 may takes the arcustangens of the amplitude ratio by 90 ° of the phase shifted component against the sofas component, either at the fundamental frequency or at the third harmonic frequency. The resulting calculated value for the arcustangens of this ratio can be compared with the expected values for different types of magnetic materials 116. A magnetic material with low coercivity will have a relatively low phase shift, as shown by the 90 ° phase rotation component. On the other hand, magnetic material 116 with high magnetic coercivity will have a relatively high phase rotation, as shown by the 90 ° phase rotation component. Similarly, signal processor 232 may provide the results of this comparison to a money-sorting display or apparatus 236 or to a device of any kind that shows a confirmed / invalid status for the offered banknote 104.

31 In addition to verifying the validity of the offered banknote 104 by verifying the type of magnetic material 116 used for the magnetic metal regions 140 of the security thread, the apparatus 100 of the present invention may also determine the characteristic of document 104. For example, if document 104 is a security or a banknote, a value may be determined banknote with a view to distinguishing between different types of documents within a common general group of documents. The apparatus 100 of the present invention can operate by distinguishing between these types of documents by detecting the spatial distribution of the magnetic material 116 of the security thread 108. This is partially achieved by using the drive coil 120 and the receiving coil 124, which provides relatively strong and very uniformly pressed magnetic fields. Likewise, because of its physical dimensions, the receiving coil 124 can also detect a response magnetic field from magnetic metal regions 140 in a highly localized pattern.

As detailed above with reference to Figures 4-7, the receiving coil 124 has a distance between two parallel strands of wire that is smaller than the smallest magnetic metal region 140 on the guard thread. For use with a protective thread with generally rectangular magnetic metallic regions 140 (as in FIG. 1), it is preferred that the driving magnetic field is pressed as far as possible in a rectangular direction with respect to the dimension of mark height 136 on the filaments. In this way, the driving magnetic field is pressed on each magnetic metal region 140 apparently independently. This gives more easily separable high-contrast pattern signatures in the resulting signals processed by the signal processor 232. if instead the pressed magnetic field runs parallel to the length of the protective thread, then the pressed magnetic field covers more than one magnetic metal region, resulting in an assembly across the magnetic field between the regions 140. This causes to some extent a blurred signal pattern. As described above, the magnetic field is pressed at a 45 ° angle, which results in viewing only one area 140 at a time, but also allows the pressed magnetic field to extend partially perpendicular to the regions 140.

Therefore, as an alternative to the 45 ° installation shown in FIG. 4, the installation of the drive coil 120 and the receiving coil 124 may be oriented relative to the banknote 104 so that the wide edge 168 of the paper is a leading edge in the direction of scanning the banknote relative to the coils 120, 124. In this situation, the two longer coil dimensions 120, 124 are oriented vertically with respect to the thread length dimension 108.

Regardless of the configuration of the drive coil 120 and the receiving coil 124, the device 100 of the present invention operates by detecting the value of the banknote 104 by detecting the magnetic material 116 used within each region of the security thread 108. The signal processor 232 may then use the data collected from each magnetic coil. metal region 140, in many different ways to determine the value of banknote 104. For example, signal processor 232 may take a time average of only some or all of the data associated with each magnetic metal region. This information for each area may be as described above, i.e., determined by a three-part test to determine the type of magnetic material 116 present in area 140. Alternatively, the signal processor 232 may inspect the amplitude peaks demodulated h

-33signals and uses data to determine value. A third alternative would be to use it for the first time when a certain amount of data appears above a certain threshold. Once a value has been determined by any method chosen, this value can also serve to indicate the validity of a banknote 104.

In another preferred embodiment, the signal processor 232 uses a spatial comparison technique of the sample to determine the value of the banknote 104. The method used by the signal processor 232 is to compare the resultant data (i.e., demodulated h by phase and 90 ° phase shifted signals for both, for the base and / or third harmonic component) with stored signal templates. It is also possible to combine the two signals (i.e., the phase and 90 ° phase shifted components) to obtain the full amplitude at each frequency used in the comparison. These templates represent the expected signal corresponding to the corresponding portion of each of the different possible patterns within the security group 104. if the value pattern is repeated several times within a single banknote, then it may be a template for a single repetition period or even for any number of repetition periods. To help distinguish between templates, each template has two numbers that are associated with it (i.e., the template threshold and the normalized template factor), and which are selected by the experimental procedure.

The signal processor 232 can complete the determination of values using the procedure written in the program. Initially, the signal processor may summarize a subset of the detected signal for the same physical length of the magnetic material sample on the security thread as represented by the template. That is, the length of the sample is

34determined by a fixed time duration determined from the known fixed velocity of banknotes traveling past the drive and receiving coils 120, 124. Instead, if the banknote velocity is not fixed (e.g., the banknote is manually moved relative to coils 120, 124 ), then velocity measurement and velocity compensation are required via 1 inarizations e, for example, obtained from determining the edge of a banknote of one or more optical sensors (not shown).

Next, the signal processor 232 calibrates the summary of the signal subset so that its average amplitude matches that of the template, the template is then subtracted from the calibrated summary signals, and the squares of the resulting curve values are summed and divided by the number of points to obtain the error result for that subset. summary by template. A smaller error score means a better match. The signal processor 232 then supplies a similar error rate for each possible subset of the detected signal against each of the templates and retains only the minimum error rate for each pattern (i.e., the error pattern achievement). This process of testing each possible set can be considered as scrolling the template along the entire length of the measured signal to find a match.

The signal processor then subtracts each achievement of the template errors from the corresponding template threshold and sorts the result according to the template normalization factor, if none of the obtained results is greater than zero, no matching occurs. Otherwise, a match occurs with the pattern against which the signal reached the highest reach. In order to further increase the level of discernment or the ability of the signal processor 232 to distinguish between different values of money, several (eg 3) templates of different lengths for each value may be used.

35The average achievement of a three-stencil template is used to finalize the value match. For example, the three templates differ in that they contain spatially raised elements of the sample. Alternatively, they may represent the degree of physical range of the trait pattern. The choice of a set of templates depends on the expected types of distortion of the physical pattern on the protective property due to use or manufacture.

It will be apparent to those skilled in the art that obvious modifications can be made without departing from the spirit of the invention. Accordingly, in order to determine the scope of the invention, it is necessary to refer to the appended claims more than the above specifications.

The invention is hereby described and the claims follow.

Claims (17)

PATENT APPLICATIONS An apparatus for verifying the authenticity of a document to which a security thread is associated, the security thread comprising one or more areas of magnetic material and each area having one or more predefined magnetic characteristics including coercivity not exceeding 5000 amperes per meter and a relative permeability between about 200 and 10,000, characterized in that it contains: a. propellants for providing a depressed magnetic field as an alternating field of a predetermined fundamental frequency within a predetermined spatial region through which the document travels, wherein propellants comprise means for ensuring that the depressed magnetic field is saturated in at least one or more magnetic regions material; b. receiving means for detecting the response of the magnetic field within a predetermined spatial region through which the document travels at a distance not exceeding ten millimeters from the portion of the receiving means for detecting the magnetic field, and for providing one or more detected signals characteristic of the corresponding one or more response characteristics of the magnetic field; and c. signal processing means that respond to detected signals to determine at least one or more predetermined magnetic characteristics of each area of magnetic material in order to verify the authenticity of the document. A device according to claim 1, characterized in that one or more predetermined magnetic characteristics of at least one or more areas of the magnetic material includes a type of magnetic material. Apparatus according to claim 2, characterized in that the response magnetic field is an alternating magnetic field and, in the presence of a protective thread in a predetermined spatial region, the response magnetic field is a predetermined fundamental frequency of the pressed magnetic field and one or more higher harmonic frequencies than a predetermined certain basic frequencies. Device according to claim 3, characterized in that one or more of the detected signals is characteristic of a predetermined fundamental frequency and of one or more higher harmonic frequencies than a predetermined fundamental frequency, wherein the signal processing means comprises means for determining the type magnetic material in response to one or more detected gals. Device according to claim 4, characterized in that the signal processing means comprise means for determining the type of magnetic material by comparing the detected signal characteristic of the third harmonic frequency with the first predetermined threshold, by comparing the detected fundamental frequency signal with the second predetermined threshold and by comparing the ratio of the detected signal characteristic of the third harmonic frequency to the detected signal characteristic of the fundamental frequency with a predetermined range of values. Apparatus according to claim 3, characterized in that the receiving means comprise means for providing at least one of the detected signals as an actual phase signal, which is characteristic of the phase of the response magnetic field with respect to the pressed magnetic field of a predetermined fundamental frequency. Apparatus according to claim 6, characterized in that the signal processing means comprise means for determining the type of magnetic material by comparing the actual phase signal with the reference phase signal, wherein the actual phase signal is characteristic of the magnetic coercivity of the magnetic material and the reference signal is characteristic of the expected value of the magnetic coercivity of a magnetic material. Apparatus according to claim 1, characterized in that the receiving means comprise means for providing at least one of the one or more detected signals for each of the one or more areas of the magnetic material, wherein the signal processing means comprise means that respond to the detected signals to determine the characteristics of the document to determine the authenticity of the document. Device according to claim 8, characterized in that the document characteristic is the document value. Apparatus according to claim 9, characterized in that the signal processing means comprise means for determining the value of the document by comparing the detected signals with one or more stored signals characteristic of the desired document value. Device according to claim 2, characterized in that the predetermined base frequency is between about 500 hertz and 500 39kilohertzi. Apparatus according to claim 1, characterized in that the propulsion means comprise a first coil of wire and that the receiving means comprise a second coil of wire. Apparatus according to claim 12, characterized in that the second coil of wire has a width less than the length of any one or more areas of the magnetic material of the protective thread. Apparatus according to claim 12, characterized in that the first coil of wire and the second coil of wire are both spaced on one side of the document. Apparatus according to claim 12, characterized in that the first coil of wire and the second coil of wire are both spatially positioned on both sides of the document. Device according to claim 12, characterized in that the first coil of wire is wound on the core. Device according to claim 16, characterized in that the core is made of ferrite material. Apparatus according to claim 12, characterized in that the first coil of wire and the second coil of wire are spatially positioned on opposite sides of the document.