CN1188554A - 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 calibration equipment of magnetic security thread

Background of invention

The present invention relates to the security thread that uses in a kind of securities such as paper substrate such as for example bank note and bankable bill etc., or rather, relate to a kind of device that detects security thread and definite security authenticity and kind by security thread.

Used some to be used for for example distinct methods of paper substrate securities authenticity such as bank note and bankable bill, cashier's check, security of verification in the prior art.These or other method can also be used for the characteristic of verification security, for example kind of bank note.Can discern the different characteristic of same big class security in this way.Yet it is the authenticity of verification security that the kind of verification bank note also can be understood as.

All known methods of calibration all are to depend on detection particular physical characteristics or the pattern relevant with security with measurement.Usually, characteristic body to be detected is to have a mind to join in the security as the part of security recognition system or false proof security check system in the manufacture process of securities.Usually design the type of the security feature thing that is used for determining being added to security relevantly with the device of distinguishing various security characteristics (indicating) with the physical characteristics of security feature thing according to the special characteristic of design in the security feature thing.A kind of functional characteristic of the best so just is provided in the security verification.

Method commonly used comprises the use magnetic ink, and it prints out predetermined pattern on the precalculated position on paper surface.Another kind method is that the plastic safety silk substrate that is coated with conduction and/or magnetic material predetermined pattern is partially or completely imbedded in the paper of bank note.Design then a kind of detecting device with the type of test material and in limited range the space distribution of test material on thread substrate.

Specifically, the magnetic material that formerly uses in field of securities strictly is limited to the magnetic material of comparison " firmly " (that is, having than high coercivity).Magnetic material can be that a part is printed on the lip-deep ink of security, also can other form introduce the security surface, or be coated on the security thread plastic of imbedding in the security.

These detections than hard magnetic material (and verification of security authenticity and/or its some characteristics) are normally by putting into magnetic field to the magnetic material, detect then that its remaining magnetization finishes.Can be when making security or this was added to magnetic field on the magnetic material before " reading " or detection of magnetized intensity by detection system in merchandise sales transaction or bank carry out the process of sorting to bank note.The example than hard magnetic material in above-mentioned field comprises magnetic, as ferrite, or the thin slice or the bar of crystal magnetic material, as nickel.(referring to U.S. patent 4183989).Magnetizing pattern can be write on the material, and can be read this pattern with read head.Read head can read direct current (DC) magnetization (for example Hall effect detection), or the mM disodium hydrogen phosphate that produces when utilizing bill to move by read head reads.In both cases, only measure netted remanent magnetization.This method need be used high-intensity magnetic field to magnetize the read head of detection usefulness in advance and improve its susceptibility.Its limitation is to make the detection behavior to the magnetic material occur in neighbouring (spaced far between read head and the magnetic material is much smaller than 1mm).The method example that this usefulness " firmly " magnetic material carries out the security verification sees EP0295229, WO92/08226, EP0319524, EP0204574, EP0428779, WO91/04549, GB2130414, WO91/10902, EP0413534 and U.S. patent 3870629.

Know, in the application aspect the security security, in eas field (for example, the commodity anti-theft in retail store environment detects), also used the magnetic material of " soft " (that is low magnetic coercivity) with respect to " firmly " magnetic material and they.Compare with hard magnetic material, soft magnetic material is easier to be magnetized on the more weak distance in adding magnetic field.A kind of typical application is included on the Retail commodity sticks on " label " or " mark ", and includes soft (for example, ferromagnetic) material attached to it on these " labels " or " mark ".If commodity are by legal purchase, the salesman of retail shop will take out commodity or the magnetic on the mark is changed so.If yet there is the people to attempt to steal commodity, the inquiry magnetic field that is applied to the retail shop exit so will project on the mark, will produce thus or launch the discernible signal with special properties.Can carry out audible alarm with these signals has thievery to take place to remind the people in the shop.

The application of these existing surveillances is included in the bigger space label object that has that is in basically on free position or the orientation is detected.The soft magnetic material that comprises label is the material of high magnetic permeability; Therefore, be easy to make this material to reach capacity over time by the alternating current (AC) that is applied in the magnetic field.Saturated magnetic material production nonlinear response magnetic field, this magnetic field comprises the harmonic frequency in the impressed field frequency.

The problem that exists in the known electric surveillance is that it need visit a very big space.Magnetic bodies commonly used for example key is that with the different of magnetic mark they have very low magnetic permeability.Therefore, common object will lack than the harmonic signal (with lower frequency) of high magnetic permeability object emission.Therefore, in order rightly high magnetic permeability soft magnetic material (indication of goods) and low magnetic permeability soft magnetic material (house key) to be made a distinction, must to detect higher hamonic wave and handle by the electronic article surveillance system.Yet problem is that the intrinsic signal energy that occurs in higher hamonic wave is than much less in the low-order harmonic.So, detection system must do more complicated.

In addition, in order clearly to discern multiple object, combine the electronic article surveillance system of limited quantity with several magnetic elements that separate.Each element produces slightly different responses to the access region on relatively more even in the detection system (ground, space) with reading to distinguish.In this way, when on label or tag, applying accurate evenly visit field, just can decipher so that the identity property of indicating label the multifrequency nature of response magnetic field.Can utilize frequency or magnetic intensity switching threshold to discern separable feature.In prior art, also adopted some to utilize high resolution " to read " means that method reed from antitheft feature is got space explanation data.This be because the required detector coil size in antitheft field much larger than the size of recognition feature (being label).

In the prior art about the example of electronic article surveillance system and parts thereof at EP0295028, WO88/09979, EP0611164, EP0352513, French Patent (FRP) instructions 763681 and U.S. patent 3665449,3747086, the existing description and explanation in 3790945,3292080,4074249 and 5005001.

Therefore, a fundamental purpose of the present invention be to the paper substrate securities that are embedded with security thread for example the authenticity and/or the kind of bank note or bankable bill carry out verification, described security thread has magnetic characteristic.

General objects of the present invention is to visit security thread that has field signal and authenticity and/or the kind of determining the paper substrate security according to the magnetic response signal that sends from security thread.

Another object of the present invention provides a kind of security thread, has " soft " magnetic material on its one or more zones, and this security thread is imbedded in the paper substrate securities usually fully; The present invention also provides a kind of device, and whether this device can verification magnetic filamentary material be the material of predefined type and determines such as features such as security types according to the space distribution of magnetic material.

Another object of the present invention provides a kind of contactless calibration equipment that can detect magnetic distribution of material state on the type of security thread and the security thread by visit magnetic field.

A further object of the present invention is AC magnetic field to be applied to by predetermined pattern from the noncontact source apply on the security thread of soft magnetic material, and detects the magnetic field that formed once more by security thread and determine to be embedded with one or more features of the security of security thread by detecting magnetic field.

Reading the following description in conjunction with the drawings will make above-mentioned or other purpose of the present invention and advantage become more obvious.

Summary of the invention

In order to overcome the shortcoming in the prior art and to reach above-mentioned each purpose, the applicant has invented the device that a kind of authenticity that can verification has the bank note of security thread can be checked its kind again, and described security thread integral body is formed by magnetic material.Preferably, security thread is made of thin rectangular plastic substrate, and its integral body is imbedded in the bank note.Have on one or two apparent surface of substrate by predetermined space distribution patterns deposition soft (that is, easy magnetization) magnetic material thereon, described predetermined pattern is used to represent for example kind of bank note.The bank note that can represent different size by the different spaces distribution patterns of magnetic material.

According to a first aspect of the present invention, the type of the soft magnetic material that security thread uses be by means of make the bank note that is embedded with security thread from coil that the ac signal which of preset frequency is connected near by determining.Drive coil has been set up an AC magnetism Driving Field, and this Driving Field is owing to the setting of drive coil size and position becomes field highly uniformly.The field intensity of driving magnetic field is enough to make the magnetic material on the security thread to reach capacity.Response field by the magnetic material production is non-linear, so harmonic component can occur.Measuring coil detects response magnetic field and various frequency components is converted to electric signal.These signals are carried out demodulation and find linearity homophase and quadrature (i.e. 90 degree phase shifts) amplitude components or fundamental signal (promptly, response signal component under the drive signal of same frequency), with the fundamental signal of third harmonic, thereby can determine type of material.For example, for the soft magnetic material of the particular type under the specific magnetic incentive condition, be well known that the amplitude of harmonic signal must be on a certain threshold value, the amplitude of first-harmonic must be lower than certain different threshold level simultaneously.And the ratio of the amplitude of third harmonic and first-harmonic must be within certain scope.This threshold value and scope are known and are unique for every kind of dissimilar soft magnetic material.

According to a second aspect of the present invention, the magnetic test coil that adopts in first aspect present invention is (that is the high polarization) of nonuniform space location with respect to security thread.Realize that this high polarization needs at least one size of coil to be far smaller than the total length of security thread, is preferably less than the length of the minimum magnetic regions of security thread.Be preferably in respect to the security thread height dimension be 45 the degree angles (that is, no matter the magnetic material on security thread in what characteristic appears, Driving Field all becomes miter angle with it) on apply the magnetic Driving Field.The advantage of this angle orientation is can to allow once a magnetic material district on the access security silk.For the space distribution that detects magnetic material district on the security thread provides suitable resolution, therefore can determine the kind of bank note thus.

With with the similar mode of first aspect present invention, the field signal that finally sends once more from the security thread is divided into first-harmonic and third-harmonic component, and checks that by means of signal processor homophase and quadrature component are to determine the kind of bank note.A kind of method of definite bank note kind is that the magnetic material space distribution signal on the security thread that expression is measured is stored in the storer and represents the method that the signal of the spatial distributed pattern of various effective kinds is compared with a plurality of.

Brief Description Of Drawings

Fig. 1 be have magnetic material and in the paper substrate securities as the skeleton view of the security thread of security feature thing;

Fig. 2 is the skeleton view of the variant embodiment of security thread shown in Fig. 1;

Fig. 3 is the planimetric map of another variant embodiment of security thread shown in Fig. 1 and Fig. 2;

Fig. 4 is arranged on the ferrite iron core and the drive coil of putting together with the bank note that comprises the security thread among Fig. 1-3 and the skeleton view of receiving coil, and described bank note is from driving and near the of receiving coil apparatus passed through;

Fig. 5 is the top view of driving shown in Fig. 4 and receiving coil deployment scenarios;

Fig. 6 is the end-view of driving shown in Fig. 4-5 and receiving coil deployment scenarios;

Fig. 7 is the another kind of deployment scenarios of drive coil and receiving coil;

Fig. 8 is the schematic block diagram of the circuit that is connected with receiving coil with drive coil shown in Fig. 4-7; With

Fig. 9 is the detailed maps of an interior described element of block scheme among Fig. 8.

DETAILED DESCRIPTION OF THE PREFERRED

At length contrast accompanying drawing, there is shown a kind of device that is used for the authenticity and/or the feature (for example kind) of verification paper substrate securities, generally represent this device among the figure with reference number 100.Device 100 is applicable to the security 104 that have security thread 108 things such as security feature such as grade, and these security comprise bank note or bankable bill etc.The plastic 112 that security thread 108 is imbedded in the bank note 104 by integral body constitutes.Be covered with the soft magnetic material 116 of predetermined pattern on the surface of substrate 112.During work, the security 104 that have security thread 108 are passed through near the of coil 120, be added with alternating current on the coil 120, so in the presumptive area around the drive coil 120, form magnetic field.Be provided with receiving coil 124 near drive coil, coil 124 links to each other with treatment circuit 128.When the security 104 that have security thread 108 from drive coil 120 neighbouring by the time, the magnetic field that applies makes the soft magnetic material 116 on the security thread substrate 112 saturated.Magnetic material on the security thread substrate is launched the nonlinear response field that comprises various frequency components again, and a kind of frequency component is the frequency component identical with the externally-applied magnetic field frequency, and another kind of frequency component is the harmonic component that is several times as much as the externally-applied magnetic field frequency.Receiving coil 124 detects the various frequencies of response magnetic field and produces corresponding electric signal.These electric signal are handled by pre-mode by circuit 128 so that finally determine the type of magnetic material 116 and the space distribution of magnetic material 116.In this way, the authenticity that device 100 can verification security 104 and determine the characteristics such as kind of security.

With reference to Fig. 1-3, in a preferred embodiment, security thread 108 comprises plastic 112, has at least one security feature thing on the plastic 112, and this security feature thing has adopted and has been positioned at least one lip-deep soft magnetic metal of substrate.Yet, should be noted that the preferred embodiment of this security thread only is for example.Can also adopt other substitute that combines with security if necessary, these substitutes comprise disk or thin slice, or analog.No matter selected the security feature thing of what type, the common feature of each characteristic body is the type and the space distribution of magnetic material 116.Under the situation of silk 108 safe in utilization, plastic 112 only is made of " carrier " that carry magnetic material 116.

The preferred embodiment of security thread 108 comprises that 112: the first security feature things of plastic that have two kinds of security feature things comprise the alternative soft magnetic metal pattern 132 that repeats; The second security feature thing comprises the mark 136 that is formed by magnetic and/or nonmagnetic metal.The selectivity repeat patterns 132 of the first security feature thing comprises at least one soft magnetic metal district 140 and at least one cut section 144, and wherein these zones are selectively pressed alternating sequence and formed the pattern 132 that extends along plastic 112 length directions.Cut section 144 makes metal area 140 form the magnetic standard to each other independently when security thread 108 is subjected to the magnetic field visit, and this will be that example is elaborated with device 100 of the present invention below.That is to say, but the detected characteristics of cut section does not influence the detectable signal poor (if any) that metal area 140 produces.

As the magnetic metal material 116 of security thread 108 be when with the interchange magnetometer when about 10 kilo hertzs (kHz) measure under the frequency of about 100kHz coercive force less than the low-coercivity soft magnetic metal of 5000 peace/rice (A/m).The coercive force that preferred soft magnetic material is had is between about 50A/m and about 5000A/m, and is preferred between about 100A/m and about 2000A/m.These preferred soft magnetic metals demonstrate it has enough toughness and elasticity to mechanically deform.They also have very high relative magnetic conductivity, and its scope is from about 200-about 100,000.Metal is being lower than approximately 10, and the downfield of 000A/m is issued to saturated, and forms non-linear magnetic force scope, and this scope can provide the harmonic signal that can measure during even as big as the magnetic characteristic of the magnetic field detection intermediate range (being 1-2mm) that applies using.

Preferred soft magnetic material comprises the amorphousmetal glass material, amorphous alloy soft magnetic metal for example, and these amorphous alloy soft magnetic metals comprise cobalt/ferrous alloy, iron/nickel-base alloy, and cobalt/nickel-base alloy.Suitable cobalt/ferrous alloy can be from German Hanau (mailbox 2253, D-63412) vacuum fusion (Vacuumschmelze) company limited has bought, its trade mark is by name: Vacuumschmelze6025 (66% cobalt (Co), 4% iron (Fe), 20% molybdenum (Mo), 16% silicon (Si) and 12% boron (B)); Vacuumschmelze6030 (being similar to Vacuumschmelze6025, the 70%Co that has an appointment, micro-unknown component); And Vacuumschmelze6006 (46% (Co), 26%Ni, 4%Fe, 16%Si and 8%B).Suitable iron/nickel-base alloy composition can (Parsippany NJ07054) have bought, and its trade mark is by name: Allied Metglas2714t2704 from Allied-Signal company.These materials form non-crystal structure under certain mode of deposition.

The magnetic metal that is suitable as the security thread second security feature thing had not only comprised but also had been not limited to soft, hard magnetic metal.The nonmagnetic metal that is adapted at using on the security thread comprises aluminium, nickel and silver, and preferential metal is an aluminium.

In Fig. 1, the pattern 132 of security thread 108 comprises that magnetic metal district 140 and adjacent 144, two zones of cut section all adopt rectangular shape.The mark 136 that forms by metal in magnetic metal district 140 as the magnetic metal mark and in cut section 144 as metal marker.In Fig. 2, thus pattern 132 by thickness increase forms three magnetic metal districts 140 with different magnetic intensities zone and between these zones and profile be that a dollar corresponding cut section that indicates constitutes.Cut section 144 is between each magnetic metal district 140.In other words, form by metal and adopt dollar the mark of sign profile and cut section 144 co-extension also to play complete isolated metallic regions 140 (see figure 2)s.The meaning of term " co-extension " is that main region 140,144 has identical space boundary with mark as used herein.

In Fig. 3, the magnetic metal zone 140 of the first security feature thing and the second security feature thing is a co-extension.For example, the mark of the second security feature thing that is formed by metal is the magnetic metal mark, and it constitutes the magnetic metal district of the first security feature thing.

Can manufacture plastic 112, the preferably non magnetic and non-conducting material of these materials with any transparent or translucent material.This material comprises polyester, regenerated cellulose, Polyvinylchloride and other plastic sheeting, and preferable material is a polyester.These films keep in touch in paper-making process and the width range of these films is preferably from about 0.5 millimeter (mm)-Yue 3.0 millimeters (mm).

As mentioned above, the pattern 132 that optionally repeats the first security feature thing comprises at least one soft magnetic material district 140 and at least one cut section 144, and these two zones are along optionally occurring by the order that replaces in the pattern 132 that extends on the part of plastic 112 or the whole length.Other possible order comprises polylith magnetic metal district 140, and these magnetic metal districts adopt a large amount of magnetic metals and separated by cut section 144.Each metal area 140 all is made of the magnetic metal material of difference amount.The effect of cut section 144 is that to make metal area 140 form magnetic to each other accurate independent, and cut section 144 can take the form of nonmagnetic metal area or employing to make the form of this district's magnetic metal content or surface coverage lower than magnetic metal district.Magnetic metal district 140 and cut section 144 can adopt Any shape or profile.

Under the influence of the magnetic conduction effect of determining by shape and be subjected under the thickness effect of magnetic coercive force effect, when the magnetic response determined with the shape (for example size and thickness) in magnetic metal district from the magnetic metal district, the thickness range in preferred each magnetic metal district 140 is from about 0.01-about 10 microns, and more preferably its thickness is from about 0.10-about 0.50 micron.Also preferred each magnetic metal district 140 is from the about 5mm of about 0.1mm-along the length range on plastic 112 widthwise edge edges.Adopt the magnetic metal zone 140 of above-mentioned reference dimension should provide with the magnetic permeability of being determined by shape and be worth accordingly, the preferable range of this value is 200-10,000.This high permeability can make magnetic metal easily reach capacity in low-intensity magnetic field.What produce in particular field in addition, saturatedly provides further basis for the verification authenticity.

The second security feature thing of security thread 108 can be the common security characteristic body that extends that separate and/or common, it comprise magnetic and/nonmagnetic metal mark 136, for example metallicity thing or the transparent feature thing of determining by metal boundary.Specifically, the part that mark that magnetic metal forms or transparent feature thing can constitute each magnetic metal district 140 and cut section 144, and/or form cut section 144.On the other hand, magnetic metal mark or magnetic metal characteristic body 136 can form the part of magnetic metal district 140 and/or each cut section 144.And the mark 136 that nonmagnetic metal mark or nonmagnetic metal form can constitute the part of cut section 144.In a preferred embodiment, when being embedded with security thread 108 in bank note 104, the speech or the phrase that are provided with on the mark 136 can not be offered an explanation rapidly in reflected light, but then can be clear that by the public in transmitted light.So 100 verifications of the device of the present invention that will describe in detail hereinafter, the first security feature thing (that is magnetic metal district) and the not verification second security feature thing (that is mark).

The first and second security feature things can form by depositing magnetic metal material 116 with any method in the several different methods on plastic 112, described method includes but not limited to following method, these methods comprise by the electro-deposition direct heat and print on the substrate or use the method that mask in the vacuum metallizing device or template carry out selective metallization and carry out metallized method by chemical etching, laser ablation etc. after selectivity disappears metallization.

It is preferred carrying out metallized method after selectivity disappears metallization.The metallization that can consider or deposition technique also comprise sputter except the organic metal steam pyrolysis, for example, and planar magnetron sputter, electron beam or thermal evaporation/distillation, and electrochemical deposition.Preferred metallization or deposition technique are sputters.

Sputter is the process of carrying out the physics evaporation deposition in vacuum chamber, penetrates atom from target after wherein making gas iron (for example argon) quicken to cross an electric potential difference with enough power.The atom that penetrates clashes into a surface (for example, plastic 112) after passing one section vacuum, and atom condenses the formation coating from the teeth outwards.Can consider by manufacturing the target (for example, a kind of alloy can form the metallic glass of noncrystal shape) that uses the sputter procedure from the plasma of molten state injection and after deposition, need not annealing the material of deposition.

The metallization technology that disappears that can consider is the technology of optionally removing deposition materials from target surface.As mentioned above, these technology comprise chemical etching and laser ablation.Technology is ground and moved to other technology that comprises in addition.The technology of moving refers to the technology of optionally removing deposition materials after the bonding agent on removing carrier by optionally applying bonding agent.Chemical etching and laser ablation are preferred.

After for example iron chloride or hydrofluorite/nitrate mixture carry out chemical etching with suitable etchant, just can carry out chemical etching by printed resistor optionally.

In order to obtain having shown in Fig. 2 the magnetic metal district 140 of different-thickness, can the etching technique of only removing the plated metal original thickness partly with on the entire depth of depositing metal layers, carry out etched technology and be used in combination.

Can carry out ablation down at lower laser, because when the temperature that soft magnetic metal of the present invention is heated to about 350-400 ℃, they will crystallize into noncrystalline state.Final tissue disruption can make material become thin slice and chip usually.And, to compare with the needs in the laser-induced thermal etching of vacuum deposited aluminum, its requirement to energy has reduced.

Except above-mentioned, this print head can also use traditional thermo-contact print head to drive the crystallization again of target material and carry out thus that material removes or etching, because can reach the resolution of about 450 ℃ temperature of about 350-and the about 300dots of per inch (dpi).

Security thread 108 can comprise extra play or the coat except magnetic metal.Admissible extra play or coat comprise that the plastics protection that can make security thread avoid chemical erosion is outer and can make in security thread being imbedded safe bank note such as bankable bill the time security thread under reflected light unconspicuous reflective metal layer with cover up layer.Can also comprise the tack coat of being convenient to make security thread combination in default free securities or on it.

If make the compounded plate that comprises the security feature thing by the method that describes in detail above, can be cut into security thread to compounded plate or utilize suitable mold pressing operation handlebar compounded plate to be divided into a plurality of disks with traditional technology so.

Can be when making safe bank note security thread 108 be incorporated in the safe bank note 104 such as bankable bill.For example, if security thread 108 is disk shapes, can press it (also can select bonding) so, thereby finish the mounted on surface of these disks on the scraps of paper surface of local stiffening.On the other hand, if the shape of security feature thing is when comprising the security thread 108 of the substrate 112 that is coated with magnetic material 116, can put it in the wet paper fiber of not reinforcing and can be crooked according to the instruction of U.S. patent 4534398.Security thread 108 is imbedded in the paper fully.Can also send into the paper machine, cylindricality tubbiness machine of cylindricality pattern to security thread 108 or similarly in the known machines, so that security thread 108 imbedded partly (bank note that promptly has window formula security thread) in the bank note main body of making.In addition, can also install to security thread 108 on the surface of safe bank note during manufacture or afterwards.

With reference to Fig. 4, it shows a kind ofly imbeds wherein bank note or bankable bill 104 fully with security thread 108, this bill is neighbouring by (common distance from receiving coil 124 is not more than 10mm from drive coil 120 and reception or magnetic test coil 124, if possible, also should keep this distance with drive coil 120).Arrow 148 expressions among Fig. 4 scan (that is to say the minor face 152 of bank note 104 are leading edges of direction of scanning) to bank note with respect to the length dimension of coil 120,124 on " narrow limit " direction.Because security thread 108 is imbedded in the security 104, so the height dimension of mark 136 is coaxial with the throughput direction of paper.

Drive coil 120 comprises lead is wrapped in first coil 156 that constitutes on the ferrite iron core of soft magnetism sintering.Receiving coil 124 is imbedded in the insulating material 160 (Fig. 6), and this coil is made of the coil (promptly only around a circle) of solid conductor.Fig. 4-6 shows two coils, 120,124 locus with respect to ferrite iron core 156.

Ferrite iron core is used in combination the externally-applied magnetic field that can encourage by the drive coil generation with drive coil 120, thereby makes externally-applied magnetic field have homogeneity and intensity preferably on predetermined locus.Iron body oxygen iron core 156 can also with than air iron-core coil more less current form externally-applied magnetic field.Therefore for battery-operated device, can realize lower energy loss.And, use ferrite iron core 156 can also make drive coil keep separating (or rather, keeping separating) with access region or magnetic field with receiving coil.The driving circuit that will describe below can reducing like this and the coupling of the stray capacitance between the receiving circuit.If the number of turns of receiving coil 124 is fewer, can also reduce capacitive coupling.Preferred embodiment only adopts one-turn coil.In addition, also can use a plurality of receiving coils 124.

Drive coil 120 shown in Fig. 4-6 and receiving coil 124 only are arranged on the side of the bank note 104 that provides.Obviously, this layout is exemplary.Under the situation of not considering coil 120, the 124 potential advantages that bilateral is arranged, for to ergonomical or consideration restriction or that be subjected to situations such as space constraint of being powered can adopt one-sided detection.On the contrary, can be driving and receiving coil is arranged under the situation of both sides (that is two of bank note opposite sides) and can adopts the bilateral layout.Double sided coil is arranged usually can form bigger interval between driving and receiving coil 120,124, so the stray capacitance coupling in the magnetic field seldom takes place.And double sided coil arranges that the response magnetic field that can produce by the magnetic metal district 140 by security thread 108 usually forms final magnetic field intensity, and 108 pairs of security 104 of described security thread locus in the gap between receiving coil 124 is insensitive.In addition, drive coil 120 can be positioned on the side of bank note 104, and receiving coil 124 can be positioned on the opposite side of bank note.

In addition, the driving/receiving coil apparatus shown in Fig. 4-6 is arranged to certain angle with respect to the security thread in the bank note, for example miter angle.And this only is exemplary.This angular relationship makes the magnetic area 140 of driving/receiving coil apparatus on once can only access security silk 108.Yet, the angular relationships of 45 degree also make externally-applied magnetic field can with the not exclusively vertical direction of security thread on locate.

With reference to Fig. 7, wherein show the bilateral air magnetic core arrangement of driving and receiving coil 120,124.This device can form externally-applied magnetic field extremely uniformly to the security thread 108 of the bank note 140 that provided.Usually, the respective magnitudes of any harmonic signal all has very big influence in the intensity of externally-applied magnetic field and direction the response magnetic field that the magnetic area 140 by security thread 108 is produced.Therefore, require externally-applied magnetic field more equably by any position that can make bank note 104 location usually.For example, externally-applied magnetic field should be able to pass through any detection head gap more equably, in this gap owing to be used to make bank note with respect to driving and the mechanical influence of the conveyer (not shown) that receiving coil 120,124 moves may make bank note produce certain shake.In addition, as from seeing Fig. 7, drive vertical mutually with the principal plane of receiving coil 120,124.So just, avoided the magnetic field between the coil to form direct coupling.

Arrow 164 expression bank note among Fig. 7 are with respect to the direction of transfer of coil 120,124.Though in Fig. 7, do not illustrate, in one exemplary embodiment, bank note 104 and coil the 120, the 124th, directly relative, thus make the width dimensions of bank note or the guiding size that edge 168 (Fig. 4) conduct transmits.In addition, though do not illustrate in Fig. 7, the orientation of security thread 108 becomes miter angle with the length of driving and receiving coil 120,124 to size.This and above-mentioned with respect to FERRITE CORE and coil device angle for the same reason.In addition, the most important thing is, with regard to the space distribution of magnetic area 140 on reading security thread 108, the narrow dimension of receiving coil shown in Fig. 7 124 (that is the distance between two of individual pen receiving coil top or bottom parallel lines part) is less than the shortest length of any magnetic area 140 on the security thread 108.Can obtain single and field signal independently from receiving coil like this, each signal that is wherein obtained only comprises the corresponding information of some magnetic characteristics with magnetic metal district 140.Use final information when determining the concrete feature of security 104, it is to represent by the space distribution of the magnetic area on the security thread substrate 112 140.For example, when security 104 were bank note or bankable bill, definite feature was a kind.Species detection will describe in detail below.

Referring now to Fig. 8, it shows the schematic block diagram of the circuit 128 that is connected with above-mentioned each driving/receiving coil apparatus, and some part wherein is described in Fig. 4-7.Drive coil 120 and receiving coil 124 all have corresponding impedance-matching transformer 172,176, and transformer can reduce and the relevant capacity coupled influence of induction coupling.And, impedance-matching transformer 172 is used in combination with drive coil 120 can also reduces the voltage of delivering to drive coil.In addition, though do not illustrate, receiving coil 120 can have a capacitor that is attached thereto so that set up a resonant circuit.Use resonant circuit can improve the ratio of signal to noise ratio (S/N ratio) and tuned frequency and the nonresonant frequency that in the detection of this single harmonic component frequency, will reject.Yet if detect more than one harmonic frequency with circuit 128, so, tuned circuit has not just had much good and has not used capacitor usually yet.

Circuit 128 also is included in the frequency synthesizer 180 that produces unlike signal under the characteristic frequency.Frequency synthesizer 180 is carried a pair of exchange (AC) signal to conversion with buffering amplifier stage 188 by signal bus 184.Frequency synthesizer 180 can be by also carrying the resolution element of signals to constitute to amplifier 188 by the known manner setting.On the other hand, if necessary, frequency synthesizer 180 can be made of digital special IC (ASIC).

Two drive signals that provided by frequency synthesizer 180 will describe in detail below.These two signals are delivered to separation after amplifier stage 188 amplifies transformer 192 enters filtering and tuning part 196 then.Wave filter can be made of the LC bandpass filter, and it only allows frequency in the particular range to enter impedance-matching transformer 172 and drive coil 120 so that reduce harmonic content in the signal waveform that enters drive coil 120.

Frequency synthesizer also provides a plurality of signals by signal bus 200 to synchronous detection level 204.Illustrate in greater detail synchronous detection level 204 among Fig. 9, it comprises signal mixer 208 and 4 utmost point low-pass active filters 212 that a plurality of (for example 4) are identical.Each mixer all is made of the Model DG411 that can buy on market.In one exemplary embodiment, first signal that provides by bus 200 of frequency synthesizer 180 is that frequency is the AC signal of 40kHz.Secondary signal frequency on the bus 200 also is 40kHz, but has produced 90 phase shifts (promptly being in " quadrature " phase relation) of spending with respect to " first-harmonic " in-phase signal of delivering in first mixer 208.Frequency synthesizer 180 also provides the signal of 120kHz, and this signal has identical phase relation with fundamental signal.The frequency of the 3rd signal is three times in the frequency of fundamental signal, and with the fundamental signal homophase of 40kHz.At last, frequency synthesizer 180 provides the 4th signal of 120kHz, " homophase " signal of this signal and 120kHz phase relation that is orthogonal.Delivering to signal on the bus 200 to these four from frequency synthesizer 180 delivers in the respective mixer 208 and wave filter 212 synchronizing indicator 204.

Send into the corresponding signal on the signal bus 216 of also having of mixer 208 as independent input signal, bus 216 is connected with a plurality of corresponding low noise amplifiers 220.Each amplifier is made of the Model AD826 that can buy on market.Also comprise the high impedance low noise amplifier in low noise amplifier stage 220, these amplifiers are made of Model AD797.The input signal that enters these amplifiers 220 is the signal of carrying by corresponding impedance-matching transformer 176 from receiving coil 124.

Utilize each mixer 208 in the known demodulator circuit control synchronizing indicator 204 just can from the signal frequency of delivering to drive coil 120, extract the magnetic signal information that records by receiving coil 124.Each signal of output from four mixed class 208 is delivered in each signal wire that constitutes signal bus 224, and described signal bus 224 links to each other with analog to digital converter 228.Delivering to signal processor 232 from the digital signal of analog to digital converter output, signal processor is made of known micro-processor interface circuit.As hereinafter will describing in detail, the effect of signal processor is to judge near the authenticity of the security that pass through drive coil 120 and the receiving coil 124 according to the data (if any) that from the magnetic metal district 140 of security thread 108 " reading " gets.At last, can will for example send into from the signal of signal processor 232 output " master " system of a display device or bank note sorter 236 or other type.

In operation, frequency synthesizer 180 provides two kinds of signals by bus 184 to amplifier stage 188.These signals are AC signals of 40kHz, and are square-wave signals.First square-wave signal has+the 120 leading phase shifts of spending with respect to the 40kHz in-phase signal that is offered synchronizing indicator 204 by frequency synthesizer.40kHz second square-wave signal of delivering to amplifier stage 188 has the lagging phase angle of-120 degree with respect to the 40kHz in-phase signal that is offered synchronizing indicator 204 by compositor 108.Though only be exemplary, with two kind of 120 anti-phase square-wave signal of degree can be in not influencing the situation decline low circuit of performance the cost of used element.Because the quadrature square wave comprises a plurality of third harmonic frequencies components, so 124 produce the chance of intercoupling by two kinds of signal combination being got up just can eliminate this harmonic wave from drive coil 120 to receiving coil, thereby under the situation that does not comprise any third harmonic component, obtain imposing on the quasi-square wave signal of drive coil 120.

Practical structures by the top drive coil of describing with reference to the described exemplary embodiment of Fig. 4-7 120 exchanges externally-applied magnetic field extremely uniformly by the square-wave signal of 40kHz being added to just can set up on the drive coil 120.The exemplary value that is added to the driving signal frequency on the drive coil 120 is 40kHz.Yet preferred frequency range is between 500hz and 500kHz, and preferred scope is 10kHz-100kHz.Under low frequency, signal amplitude is lower, and ratio content is a limited frequency so effective telecommunications is made an uproar.This frequency also must be enough height so that each that can measure security thread 108 in several at least cycles of externally-applied magnetic field waits to differentiate magnetic metal district 140.For example, for the high speed bank note separator that uses in bank, the frequency of 10 meters transporting velocity representative p.s. is 10kHz at least usually, preferably about 40-50kHz.On the other hand, along with the increase of driving frequency, the apparent coercive force of magnetic material also increases for most of materials.The apparent coercive force should be enough low, so that make magnetic material be tending towards saturated under the effect of externally-applied magnetic field.In other words, desired height is non-linear in response magnetic field will can not occur.The value of coercive force and driving magnetic field must be suitably low with common magnetic material, for example the house key keeps enough difference.In the described in this article preferred embodiment, the apparent coercive force in magnetic material district 140 500 and 750A/m between, and the Driving Field amplitude is about 1000A/m.

When the bank note 104 that has security thread 108 contactlessly passed through from neighbouring (preferably on the distance less than 10mm) of drive coil 120 and receiving coil 124, frequency was that the AC magnetic field that adds of 40khz reaches capacity security thread magnetic metal district 140 in operation.Because the magnetic field that zone 140 is added is saturated, so these magnetic metal districts 140 will form the response magnetic field that comprises the different frequency component again.That is to say that the response magnetic field that is produced by magnetic metal district 140 comprises the fundametal compoment that frequency is 40kHz.Response magnetic field also comprises the different frequency component of harmonic wave or a plurality of fundamental components.In a preferred embodiment of the invention, also designed circuit 128, its third harmonic frequencies that is used to detect the 40kHz fundamental frequency (that is, 120kHz).Third harmonic is represented the harmonic wave of lower grade, because the inferior grade harmonic wave produces bigger signal energy than high-grade harmonic wave usually, so at this preferred inferior grade harmonic wave.And preferred odd harmonic, because they always produce prior to even harmonic under the situation without any enough direct currents (DC) magnetic field.Yet, should be noted that, in the device similar 100, can use any harmonic wave to the present invention.But as described in a preferred embodiment, use third harmonic that enough signal to noise ratio (S/N ratio)s can be provided, so it is better than using more high-grade harmonic wave.

The different frequency component of the response magnetic field that is produced by the magnetic metal district 140 of security thread 108 is detected by receiving coil 124, and finally delivers to synchronous detection level 204.The amplitude of each signal or size are carried out demodulation and are carried out digitized processing by analog to digital converter 228 by synchronizing indicator in above-mentioned four kinds of signals, then signal are sent into signal processor 232.These four kinds of signals comprise that fundamental frequency is homophase and the orthogonal signal of 40kHz, also have the homophase and the orthogonal signal of 120kHz third harmonic frequencies.According to an aspect of device 100 of the present invention, the effect of signal processor is a type of judging the magnetic material in the magnetic material district 140 that constitutes security thread 108.At one for example among the embodiment of type, signal processor 232 compares the type of judging magnetic material district 140 to the amplitude of the harmonic signal of fundamental frequency with certain threshold level level in being stored in the storer that links to each other with signal processor 232.When signal amplitude is higher than certain threshold level, in the fundamental frequency in the harmonic signal amplitude of in-phase component represent in the magnetic metal district 140 effective magnetic material 116 of using, described threshold value is and the corresponding given value of the type of magnetic material 116.So just, can guarantee to have extremely strong nonlinear material is present on the security thread 108.

The detection of second component comprises homophase fundamental component and predetermined threshold value is compared.And threshold value is known and is unique to the type of used magnetic material 116.When being lower than the specific threshold level, the amplitude of fundamental component just has condition for validity.This detection has been guaranteed excessive magnetic material can not occur on the surface of security thread when attempting to forge nonlinear characteristic in counterfeit money 104.The 3rd detection of being finished by signal processor 232 is that the ratio of homophase third-harmonic component and homophase fundamental frequency amplitude and the value range that is stored in the storer are compared, and described storer is connected with signal processor 232.This detection can be guaranteed to occur non-linear to linear OK range.The most general magnetic material that the adulterator uses in the third detects has very low level ratio.On the other hand, magnetic metal district 140 used real " soft " magnetic materials 116 of security thread 108 produce higher level ratio under the third testing conditions.This ratio determines by test and error with special measuring equipment that normally it depends on used concrete magnetic material and their quantity and profile.

Signal processor is by providing appropriate information just can indicate the result of detection to display or bill sorter 236 then.As the another kind of means of magnetic material 116 life types that use in the magnetic metal district 140 of detecting security thread 108, device 100 of the present invention can utilize the quadrature signal component of fundamental component or third-harmonic component to evaluate the magnetic coercive force of material 116.Specifically, signal processor 232 can be taken at the circular arc tangential line that the quadrature component under fundamental frequency or the third harmonic rate is compared with the in-phase component amplitude.The resulting value of the circular arc tangential line of ratio calculated is compared with the expectation value of different magnetic materials 116.Shown in quadrature component, the magnetic material of low-coercivity has smaller phase-shift phase.On the other hand, shown in quadrature component, the magnetic material 116 of high-coercive force has bigger phase shift.Use similar method, by signal processor 232 result is relatively delivered in the device of display or bill sorter 236 or any other type, so that indicate especially bank note 104 " qualified/defective ".

Except come verification especially the authenticity of bank note 104 by the type of the magnetic material 116 that uses in the magnetic metal district 140 of verification security thread, device 100 of the present invention can also be judged the characteristic of security 104.For example, if security 104 are bank note or bankable bill,, can determine the kind of bank note so by identification dissimilar in the identical securities.Device 100 of the present invention can be distinguished different security by the space distribution of the magnetic material 116 of detection security thread 108.To a certain extent, this finishes by drive coil 120 and receiving coil 124, and they can form more intense and externally-applied magnetic field extremely uniformly.In addition, the physical size of receiving coil 124 has determined it can detect response magnetic field from magnetic metal district 140 in having pinpoint pattern.

As above-mentioned with reference to Fig. 4-7 described, the distance between two coil parallel lines of receiving coil 124 is less than the minimum length in magnetic metal district 140 on the safety line.With regard to using the security thread (Fig. 1) have the magnetic metal district 140 that is generally rectangle, preferably applying driving magnetic field as far as possible with on the perpendicular direction of the height dimension of the mark 136 of security thread.By this means, available similar independent mode is applied to magnetic drive in each magnetic metal district 140.In the final signal of handling by signal processor 232, can produce more segregative high-contrast pattern " mark " like this.On the contrary, if externally-applied magnetic field is parallel to the length of security thread, externally-applied magnetic field will cover more than a magnetic metal district so, thereby produce the magnetic field coupling between zone 140.This will make signal graph thicken in some scope.Therefore, as mentioned above, externally-applied magnetic field is miter angle, and this makes once only visits a zone 140, and makes externally-applied magnetic field not exclusively perpendicular to zone 140.

Therefore, a kind of modification of arranging as 45 degree shown in Figure 4, the broadside 168 that can be designed so that bank note to drive coil 120 and receiving coil 124 with respect to bank note 104 on respect to 120,124 pairs of directions that bank note scans of coil as leading edge.In this case, the long limit size orientation of coil 120,124 is all perpendicular with the long limit size of security thread 108.

No matter which type of profile drive coil 120 and receiving coil 124 adopt, device 100 of the present invention can be measured the kind of bank note 104 by the type of the magnetic material 116 of use in each zone 140 of detecting security thread 108.Then, signal processor 232 utilizes the data of collecting from each magnetic metal district 140 with different modes to adopt the kind of determining bank note 104.For example, signal processor 232 can be got the time average of relevant with each magnetic metal district some or all data.Can utilize for three steps detected the type of determining above-mentioned each regional data and then judging the magnetic material 116 that occurs in the zone 140.In a modified example, signal processor 232 can be sought the peak value in the restituted signal amplitude and utilize the data of kind in measuring.The 3rd modified example is to utilize the fixed data amount that is higher than the certain threshold level level that at first occurs.In case determined kind by any method, this kind also can be used to refer to the authenticity of bank note 104 so.

In a further advantageous embodiment, signal processor 232 usefulness space diagram matching techniques are judged the especially kind of bank note 104.The method that signal processor 232 uses is that the signal " model " of data that the obtain homophase and the orthogonal signal of first-harmonic and/or third-harmonic component demodulation (that is, to) with storage compared.Can also combine two kinds of signals (that is, homophase and quadrature component) and obtain all amplitudes of each frequency in comparison, use.These models are represented a wanted signal, and this signal is corresponding with the suitable part of each in the various types of patterns that may occur in safety bank note 104.If such pattern occurs several times in the bank note signal that is provided repeatedly, this model can repeat the monocycle so, or repeats repeatedly repeatedly.For model is discerned, each model all has two correlations (that is, model threshold value and model typical coefficient), and these values are selected by handling experiment and error amount.

Signal processor 232 can be finished kind by the executive routine in the software and determine.During beginning, signal processor extracts on the security thread of representing with model the detection signal subclass of magnetic material pattern in the equal length section.That is to say, according to given set time length and bank note from drive and receiving coil 120,124 near by the time fixed speed just can determine the length of pattern.In other words, if bank note speed is unfixing (for example, bank note is with respect to coil the 120, the 124th, " manual operations "), so just need measure and carry out velocity compensation speed by linearization, for example, with one or more optical sensor (not shown) and according to the situation that the bank note edge is blocked it is determined.

Demarcate so that the amplitude of its average amplitude and model is mated by the signal subclass of 232 pairs of extractions of signal processor then.Subsequently model is aimed at the extraction signal that will demarcate, thereby and obtain the subclass that extracts error " branch " with the square value addition of the waveform values that obtains with divided by counting with respect to model.Error divides that the bright matching degree of novel is high more more.The subclass that signal processor 232 may occur with respect to the measuring-signal relative with each model can obtain similar error branch, and only keeps the least error branch (that is, " model error branch ") that obtains at each model.Can think that detecting each possible aggregation process is that total length slip model along measuring-signal is so that seek coupling.

Signal processor divides each model error to be compared and by the model typical coefficient result is demarcated with suitable model threshold value.If neither one is greater than zero in the score value that obtains, then proof is not mated.Otherwise,, so then form coupling if the model aligning is obtained the signal of maximum score value.In order further to increase the identification level or to improve the ability that signal processor 232 is discerned various bank note, can use a plurality of (for example 3) model of different length to every kind of bank note.Use the average model score value of three kinds of models at the kind time-like of selecting final coupling.The difference of three models is that for example, they represent the pattern elements of spatial movement.In addition, the degree that they can the actual elongation of presentation graphs pattern characteristics thing.The selection of cam group depend in the use or make in the desired type of actual pattern modification on the characteristic body.

For a person skilled in the art obviously, under the situation that does not break away from the present invention's design, can make various improvement to the present invention.And, should determine protection scope of the present invention according to affiliated claim rather than instructions.

Claims (18)

1. be used for the device that verification has the security authenticity of security thread, wherein security thread comprises one or more magnetic materials district, each magnetic material district has one or more predetermined magnetic characteristics, these characteristics comprise that coercive force is not more than 5000A/m, relative permeability is 200 and 10, between 000, described device comprises:

A. in the predetermined space zone that security pass through, form the drive unit of externally-applied magnetic field, described magnetic field is the AC magnetic field with predetermined fundamental frequency, and described drive unit comprises the device of the state that is used to form externally-applied magnetic field so that at least one zone in one or more magnetic materials district reaches capacity;

B. in the predetermined space zone that security pass through, detect response magnetic field and the receiving trap of one or more detection signals is provided, security by the time and the distance of the magnetic field detection of receiving trap part be not more than 10mm, described detection signal is represented one or more individual features of response magnetic field; With

C. signal processing apparatus, its response are used for determining the detection signal of one or more at least one feature of determined magnetic feature in each magnetic material district and the authenticity of verification security.

2. device according to claim 1, one or more determined magnetic features at least one zone comprise the type of magnetic material in wherein one or more magnetic material districts.

3. device according to claim 2, wherein response magnetic field is an AC magnetic field, and wherein when security thread occurring in prescribed space area, the frequency of response magnetic field is the one or many harmonic frequency of the predetermined fundamental frequency and the predetermined fundamental frequency of externally-applied magnetic field.

4. device according to claim 3, wherein one or more detection signals represent the one or many harmonic wave of the fundamental frequency be scheduled to and predetermined fundamental frequency and wherein signal processing apparatus comprise the device that is used for determining the magnetic material type according to one or more detection signals.

5. device according to claim 4, wherein signal processing apparatus comprises that the detection signal and first predetermined threshold by representing third harmonic frequencies compare, detection signal and second predetermined threshold of expression fundamental frequency compared and will represent the detection signal of third harmonic frequencies and represent that the ratio of the detection signal of fundamental frequency compares with the preset range of this ratio with the device of definite magnetic material type.

6. device according to claim 3, wherein receiving trap comprises that the externally-applied magnetic field with respect to predetermined fundamental frequency produces the device of at least one detection signal, said signal is the actual phase signal of expression response magnetic field phase place.

7. device according to claim 6, wherein signal processing apparatus comprises the device of determining the magnetic material type by the actual phase signal is compared with reference phase signal, wherein the magnetic coercive force of actual phase signal indication magnetic material and wherein reference signal represent the coercitive expectation value of magnetic material magnetic.

8. device according to claim 1, wherein receiving trap is included as the device that each zone in one or more zones of magnetic material provides at least one signal in one or more detection signals, and signal processing apparatus comprises the device of judging the security authenticity according to the detection signal of determining the security feature.

9. device according to claim 8, wherein the feature of security is kinds of security.

10. device according to claim 9, wherein signal processing apparatus comprises by detection signal and one or more storage signals of the required security type of expression being compared to determine the device of security type.

11. device according to claim 2, wherein Yu Ding fundamental frequency is the frequency of scope between 500Hz and 500kHz.

12. device according to claim 1, wherein drive unit comprise first coil and wherein receiving trap comprise second coil.

13. device according to claim 12, wherein the width of second coil is less than any one regional length in one or more magnetic materials district on the security thread.

14. device according to claim 12 wherein carries out space orientation to first coil and second coil on a side of security.

15. device according to claim 12 wherein carries out space orientation to first coil and second coil on the both sides of security.

16. device according to claim 12, wherein first coil is on iron core.

17. device according to claim 16, wherein iron core is a Ferrite Material.

18. device according to claim 12, wherein first coil and second coil space are positioned on the opposite side of security.

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