WO1999045506A1

WO1999045506A1 - Verification system for an object of value or a security

Info

Publication number: WO1999045506A1
Application number: PCT/EP1998/004729
Authority: WO
Inventors: Ralf Paugstadt; Benedikt Ahlers; Roland Gutmann
Original assignee: Bundesdruckerei Gmbh
Priority date: 1998-03-02
Filing date: 1998-07-29
Publication date: 1999-09-10
Also published as: DE19808652A1; JP2002528781A; EP1060458A1

Abstract

Described is an object of value or a security, especially one which is provided with a verification system, whereby one or more security elements are arranged thereon or embedded therein and the security elements are incorporated into the printing ink and/or the substrate in the form of small quantities of contrasting, fluorescent or luminescent substances.

Description

Verification system for a valuable and security product

The invention relates to a verification system for a valuable and security product according to the preamble of claim 1, and a value and security product to be processed with the verification system.

Such a value and security product can e.g. B. be a banknote, an identification card and the like. According to the prior art, one or more security elements are arranged and / or embedded on this value and security product.

The invention is based on the general task that a quick, machine verification of security documents should be possible. So far, however, it has only been possible to ensure such machine verifications with a relatively long evaluation time. It is z. B. known to apply magnetic strips as security elements on the security product and then measure the magnetization. It is also known to apply holograms and similar structures to the security element and then to measure the presence of the hologram and its composition by detecting the diffraction of light. Furthermore, it is known to apply magnetic colors to the security document and to measure their magnetization or to apply a security thread to the value or security document and to record its conductivity, composition, printing and other features of the security thread.

In the case of optical machine verification of security documents, it has so far only been possible to process such security documents in a cycle time of approximately 20 milliseconds, which leads to an evaluation rate of 50 documents per second. Such a verification time is not suitable for the evaluation of a large number of documents.

In particular, it is known to use excitation of a fluorescent printing ink for the verification of value and security documents, the lighting of which is detected with a video camera (spatially resolved) or a photodiode (not spatially resolved).

The disadvantage of these known verification systems is, however, that they are relatively insensitive and that they do not ensure high spatial resolution with short switching times. The invention is therefore based on the object of developing a verification system for a value and security document of the type mentioned in such a way that an exceptional increase in sensitivity with a simultaneously high spatial resolution and at the same time a short switching time for the rapid optical detection of the security elements on the value and Security product should be given.

To achieve the object, the invention is characterized by the technical teaching of claim 1.

An essential feature of the invention is that by using the multi-channel amplifier (MCPV detector) it is now possible for the first time to be highly sensitive (the lowest concentrations of the security elements are sufficient) and highly resolved (the finest structures of the security elements can be recognized) extremely quickly (very many documents can be Unit of time can be verified or signals that follow the excitation pulse at a very short distance can be verified) lead to the verification of the value and safety product.

Another advantage of the multi-channel amplifier used is its compactness and the possibility to work in direct contact with the document. The microchannel plate replaces the imaging optics. There is thus the possibility that the image information can be read out electronically directly. This involves a complicated manufacturing technology, which makes it difficult to replicate.

With the technical teaching according to claim 1, a pattern-like security feature can thus be detected on the value and security document in the shortest possible time with high spatial resolution.

The spatial resolution of such a multi-channel amplifier is defined by the packing density of the channels used. The distance between the channels is in the range between 10 and 20 micrometers, so that very fine details of a security pattern can be measured on the value and security product.

In contrast to other known image sensors, a very short switching time is achieved by accelerating the electron avalanche in the channels with a high voltage, in addition to the high surface resolution. Therefore can Images of various very dimly glowing patterns can be taken very quickly in succession, or the luminance distribution can be measured during a precisely defined, very short time interval. For example, the emission of a substance can be measured with a multichannel image intensifier a few nanoseconds after the excitation of the substance with a nanosecond pulse. If the decay time of the emission of the substance is also in the range of a few nanoseconds, the detection of the substance is only possible with the detector according to the invention, because only this is able to separate the intense excitation and weak emission signals, which are extremely close in time, and spatially resolved to prove.

Regardless of the patent-based verification system, the development of a novel value and security product with security elements attached to it is claimed as inventive as a separate invention.

An essential feature of this further invention is that one or more security elements are now applied to the valuable and security product, which are achieved by adding the smallest amounts of contrast, fluorescent or luminizze substances to the printing ink and / or the substrate. Absorbing luminance distributions are thus created as a security element on the value and security product, which according to the invention can only be detected and evaluated with optical multi-channel amplifiers.

The essence of this further invention therefore lies in the fact that the smallest amounts of contrast, fluorescent or luminescent substances are used as security elements, which can only be detected by high-resolution and highly sensitive multichannel amplifiers. This is because there is the advantage that, due to the addition of the smallest amounts of substance to the security element, an evaluation is only possible with highly specialized devices (namely optical multi-channel amplifiers).

This has the advantage that the security feature itself is difficult to detect, because only very small amounts of contrast, fluorescent or luminescent substances are used as security elements, which substances can only be detected by specialized measuring instruments. In addition, because of the use of multi-channel optical amplifiers, there is the possibility that one can not only detect the presence of such a weakly concentrated security element, B. the areal distribution of this security element on the 4

Prove the product of value and security and / or keep the verification period so short compared to the period of the excitation that the verification is only possible with detectors with a correspondingly short reaction time.

Due to the extremely high sensitivity of optical multi-channel amplifiers, the concentrations of the phosphors or the contrasts can be kept so low that they are inaccessible to measurements with other detectors and to a visual inspection. Even if a spectral analysis of the document of value were carried out using highly sensitive photomultipliers, the chance of detecting the signal is slim, since the location of the phosphor is unknown. Should this location be hit accidentally, it is still almost impossible to measure the spatial distribution of the signal with a resolution comparable to multi-channel optical amplifiers. It is therefore almost impossible to adjust such a luminance distribution.

The high sensitivity of multi-channel optical amplifiers enables the detection of weak non-linear optical effects as a security feature.

The sharp wavelength selectivity of multi-channel optical amplifiers, which results from the physical properties of the photocathode, can advantageously be used to discriminate against background light.

The high spatial resolution of multi-channel optical amplifiers makes it possible to localize the position of dimly glowing particles with an accuracy of up to 20 μm. For example, the distribution of statically scattered fluorescence or luminescence particles can be measured and saved as an identification file on the same document. The authenticity is verified by comparing the identification data with the light pattern. Such a document is highly secure because it is extremely unlikely that a counterfeiter will be able to measure the distribution of the extremely faint particles. Even then, it is impossible to adjust the arrangement of, for example, approximately 100-10,000 illuminated dots. Such a system is particularly suitable for film composites, since the light distributions can be integrated into the film in a protected manner.

An additional dimension of counterfeit security is given by a system based on optical multi-channel amplifiers, in which the short switching times of such image intensifiers (typically nanoseconds) are used. For example, phosphors can be selected so that the excitation requires very high peak powers (ns laser or the like) and that the emission within Nanoseconds after the excitation and close to the excitation wavelength. An optical multi-channel amplifier is then triggered so that it opens at the end of the excitation pulse and maps the light distribution. Detectors that cannot be triggered with such exact gate times are saturated by the high excitation intensity even when trying to measure at the right wavelength and in the right place and cannot measure a signal.

Similarly, the optical multi-channel amplifier can be triggered by other excitation mechanisms (electric fields in the case of electroluminescence or the like).

The short switching time of optical multi-channel amplifiers can be used to verify value documents at a very high speed. Due to the short shutter speed of such an image intensifier, for example, an image can be recorded of every value document transported past the detector at high speed.

An optical multi-channel amplifier can also be used to check an entire stack of documents of value with an image recording by verifying a luminance distribution of the edges of the documents of value from the side of a stack.

Optical multi-channel amplifiers can be electronically read out directly via anode segments, grid anodes or charge measurements. Since the electronic processing and evaluation of image data is a dynamically developing field of technology, more and more powerful and faster image evaluation algorithms are available.

Electrostatically focused image intensifiers can electronically control the magnification factor of the image.

Multi-channel optical amplifiers can convert electron, ion and X-rays directly into an enhanced visible image without a photocathode. Particularly interesting embodiments result from evaluating weak contrasts in the X-ray range.

The image field of a few square centimeters corresponds to the typical dimensions of a security feature. In the simplest case, the multi-channel optical amplifier can be brought into contact with the document to be verified with the photocathode without the need for imaging optics. 6

Optical multi-channel amplifiers are compact, have low power consumption and are wear-free.

The manufacture of multi-channel optical amplifiers is an extremely complicated process. If such multi-channel amplifiers are developed in a special design, for example, these special sensors can be easily protected against access by counterfeiters. In addition, in many embodiments of the invention, a forger would not even benefit from the original sensor, since the security feature cannot be adjusted (statistically distributed fluorescent grains, etc.).

Optical multi-channel amplifiers can also be used to detect characteristics of already existing documents of value, or to measure properties of substances that reveal a document of value as a forgery (wrong papers, colors, etc.).

In summary, the advantages of the present invention can be summarized as follows by using multi-channel optical amplifiers.

Optical multi-channel amplifiers are ideally suited as sensors for weak luminous distributions on value documents due to the following properties:

1) extremely high sensitivity (up to the detection of individual photons)

2) extremely high spatial resolution (up to 10,000 dpi)

3) extremely short switching times (in the range of nanoseconds)

4) Wavelength selectivity by choosing a suitable photocathode and due to the work function of the photo effect ("daylight-blind" sensors)

5) Direct detection of electron, ion and X-rays possible

6) the sensor surface corresponds to the characteristic dimensions of a security feature (a few cm ² )

7) the image section can be enlarged electronically

8) The luminance distribution can be read out and evaluated electronically without intermediate steps

9) small size and low power consumption

10) a complicated sensor manufacturing technology that only a few companies have mastered

11) Good suitability for use as a "black box" sensor (self-destruction if the box is manipulated, for example by destroying the vacuum seal or by high voltage). Such multi-channel optical amplifiers are also referred to below with the term MCPBV.

Their applications in connection with a valuable and security product and this in turn in connection with a weakly dimensioned security element can be summarized as follows:

MCPBV detect very weak luminance distributions that arise across the surface of the value document, varying absorption, transmission, reflection, diffraction, scattering, emission of the other effects. Due to the high sensitivity of MCPBV, even the lowest concentrations of contrast or phosphors, weak reflections, diffraction orders or the like are sufficient for reliable verification.

The concentration of the contrast or luminescent materials or the reflecting, absorbing or diffractive surfaces (security feature) can be kept so low that the luminances generated cannot be detected by other sensors. Weak intensities of nonlinear optical effects can be used as a security feature (multi-stage excitation processes such as two-photon absorption or the like make the detection of the security feature more difficult).

The very weak luminance distributions contain code or personalization information. Only MCPBV can read such information, since no other detector type has a comparably high spatial resolution and sensitivity.

MCPBV are synchronized with the excitation process so that they can distinguish a weak measurement signal from a strong excitation pulse. Other detectors cannot detect such a signal. Simple synchronization with multi-step excitations is possible.

Only parts of a value document (side edges of a stack) are used for the verification. The short shutter speeds of MCPBV enable verification of up to a few hundred value documents / sec.

Daylight "blind" MCPBV are brought into contact with the document of value. Very good suppression of background light, no imaging optics required (handheld device). 8th

MCPBV evaluate X-ray contrasts. High sensitivity and spatial resolution, no photographic emulsions required.

MCPBV special designs with special photocathodes, channel cross sections or other parameters are used in verification devices (example: a line-shaped MCPBV). Due to the difficult manufacturing technology, such detectors are not accessible to counterfeiters (therefore the information contained in one line cannot be read by counterfeiters).

Another advantage of the invention is that a large number of documents per second can be verified due to the short detection time, and up to 2000 documents per second can be evaluated automatically.

The subject matter of the present invention results not only from the subject matter of the individual patent claims, but also from the combination of the individual patent claims with one another.

All of the information and features disclosed in the documents, including the summary, in particular the spatial design shown in the drawings are claimed to be essential to the invention, insofar as they are new to the prior art, individually or in combination.

In the following, the invention will be explained in more detail with reference to drawings showing several possible embodiments. Here, from the drawings and their description, further features and advantages of the invention which are essential to the invention emerge.

Show it:

Figure 1: top view of a value and security product in a first embodiment;

Figure 2: Schematic side view of the verification device;

FIG. 3: shows a section through a microchannel image intensifier;

Figure 4: The enlargement of a channel from one Microchannel image intensifier with representation of the excitation mechanisms in the microchannel plate;

Figure 5: The comparison of excitation pulse and response pulse in the verification of the security document;

Figure 6: The top view of a security document with

Meeting even higher security requirements

Figure 7: Another embodiment compared to

Figure 3 in the formation of a microchannel image intensifier.

In FIG. 1, various security elements 2, 3 are arranged on a document of value 1, their arrangement being possible in any manner. In addition, one or more security strips 6 and / or one or more graphic elements (patterns) 7 can be arranged.

Such a security element 2,3 can, for. B. consist of an areal distribution of several pixels 4,5, which form the security element 2,3 in a desired or random distribution.

The document of value 1 can be a bank note, an identification card or the like, wherein the said security elements 2, 3 or the security strip 6 and the graphic elements 7 can both be embedded in the document of value 1 and can also be applied to the document of value itself.

A novel evaluation of such security elements for the verification of the value document 1 will now be described in more detail.

For this purpose, according to the invention, a so-called microchannel image intensifier 8 is used, as is shown schematically in FIG. 2. It is important here that the security elements 2, 3, 6 attached to the document of value 1 emit a weak signal upon excitation, which signal is fed to the microchannel image intensifier 8 in the direction of the arrows 11-13, so that this weak signal can be evaluated by highly specialized evaluation devices . In this case, the specified security elements 2, 3, 6 are excited by an excitation source 9, which for example irradiates the value document 1 in the direction of the arrow 10. 10

Of course, the type and arrangement of the excitation source 9 in relation to the value document 1 is variable within free limits. The excitation source 9 can in this case be arranged on the side of the document of value, it can also be arranged on the side of the microchannel image intensifier and be directed in the same direction towards the document of value 1 as, conversely, the signals from the document of value 1 are fed to the microchannel image intensifier 8; the excitation source can, however, also be arranged below the value document and radiate through it.

Various excitation mechanisms come into question as excitation sources 9, such as e.g. B. the excitation by electron beams, by laser beams, by light, by X-rays, by ionizing radiation, by magnetic alternating fields and the like. More.

Thermal excitation (IR rays) can also be considered, as can excitation by UV rays.

Weak intensities transmitted by a security product can also be detected in transmitted light.

The security elements consist of the smallest amounts of contrast, fluorescent or luminescent substances, which are either arranged in the printing ink itself or are present in the substrate.

In addition, other excitation mechanisms can be used, such as. B. extremely difficult to detect bio- and chemiluminizing systems or fluorescence-labeled special chemicals.

The basic structure of a microchannel image intensifier is explained in more detail with reference to FIG.

A window coated with a photocathode is arranged in an evacuated housing 14, the photocathode 15 being arranged in the housing 14 for drawing reasons. A stream of light quanta 19 strikes this photocathode 15 in the direction of the arrow 18, which eject electrons 35 from the photocathode 15 and are accelerated onto the microchannel plate 16 in the direction of the arrow 36. The structure of the microchannel plate 16 is explained in more detail in FIG. 4. It essentially consists of an empty channel 20, on the inner walls 22, 23 of which the electrons appear in the direction of the arrow 21 and are passed on in a zigzag fashion 1 1, whereby secondary electrons are triggered from the coating of the inner walls 22, 23, which then emerge from the microchannel 20 in the form of an electron avalanche 24 and are accelerated in the direction of the fluorescent screen 17. On this fluorescent screen 17, the electron current is converted into a corresponding luminance distribution and further evaluated. As an evaluation device z. B. a CCD in question; the electron current can also be evaluated directly without the presence of a fluorescent screen 17.

General image processing systems can be used for this.

Such an excitation in connection with the response pulse is shown in FIG. It is shown that an excitation pulse 25 of extremely short duration strikes the value document in the range of a few nanoseconds and excites the security element 2, 3, 6 arranged thereon, which responds with a corresponding response pulse 26, with a time delay by -Δt.

In Figure 5 it can be seen that a relatively short evaluation time 27 is also only available in the nanosecond range, which has the advantage that the security against forgery of such a value and security document is significantly improved because there are only a few devices in the Are able to carry out a verification within such a short evaluation time 27.

Most detectors that are known to date are otherwise unable to distinguish between the signal of the excitation pulse 25 and the signal of the response pulse 26, i. H. carry out the verification within the evaluation time 27.

The verification method according to the invention therefore consists in exciting with an extremely short excitation pulse 25 in the nanosecond range. If a longer excitation pulse is used, then the response pulse that arises later disappears in the excitation pulse 25 and an evaluation can no longer take place.

The verification method also consists in using an excitation source 9 which is capable of generating such a short excitation pulse and, moreover, a verification unit (microchannel image intensifier 8) which is able to carry out the verification within the short evaluation time 27 that follows . FIG. 6 shows a further embodiment of a document of value which takes even higher security requirements into account.

There are a number of security elements 2, 3 arranged on a coded area 28, which is delimited by register marks 30. B. be brought to light by excitation. The coordinates of the luminous and possibly also self-luminous safety elements are now determined with the previously described evaluation unit. In addition to the coordinates (position determination) of the security elements, other properties of these security elements can of course also be read out on the value document 1, such as, for example, B. their individual specific luminance, their distribution on the document, their color, their dimensions and other properties more.

The properties read out are z. B. inscribed in a readout field 29, which is also located on the document of value 1.

To verify the value document 1, the value document to be verified is now excited with the excitation source 9 and the properties of the security elements 2, 3 are read out in the coded area 28 and compared with the information stored in the readout field 29. In this way, a document of value with high security against forgery can be created, which can be quickly verified.

The security against forgery is further increased if there are a large number of security elements 2, 3 which are distributed in a certain distribution on the coded areas 28.

For the rest, this also results in the possibility that only certain documents of value are coded in a precisely prescribed coding, in order to distinguish them from other, external, similar documents of value, in order, for. B. encode banknotes that were paid for a kidnapping and are then to be recognized later.

It should also be pointed out that the presence of an excitation source 9 is not important, the safety elements 2, 3, 6 mentioned can also be designed to be self-illuminating. Such an emission can e.g. B. done in that the security elements 2,3,6 are designed as self-radiating sources. 13

FIG. 7 shows a further possibility of excitation by means of a further embodiment for verification, the excitation being carried out by an ionizing radiation source 31. Radiation density barriers 34 are arranged on the document of value 1 in any number and arrangement, which only allow the x-rays 32 impinging on the document of value to pass in a certain area 37 in the direction of the arrow 38, while the other areas are shielded by the barriers 34. In this way, the emission radiation specific to the document of value 1 reaches the microchannel plate 16, which is arranged in a housing together with the fluorescent screen 17.

In the event that an electron radiation source is selected instead of the ionizing radiation source 31, the same explanations apply in FIG. 7, except that the housing 33 also includes the value document 1 and - in order to bring the value document 1 into the housing - it is provided that this Housing is flushed with an inert gas.

In this way it is possible to quickly enter the value documents 1 in the housing and bring them out again.

The inert gas serves to enable the electron to be transported in the housing.

Nonlinear optical effects in connection with the novel method are described below.

Such a suggestion exists, for. B. in that excitation with a first frequency, but that the security elements 2, 3, 6 emit in a different frequency range and this secondary radiation is then evaluated by the microchannel image intensifier according to the invention.

Such nonlinear effects are generally very weak and are therefore particularly suitable for evaluation in the microchannel image intensifier according to the invention.

For this purpose, it can even be provided that the primary beam is filtered off or is not visible to the photocathode by a suitable design. So only the nonlinear optical signal is evaluated. DRAWING LEGEND

1. Value document

2. Security element

3. Security element

4th pixel

5th pixel

6. Security strips

7. graphic elements (samples)

8. Microchannel image intensifier

9. Source of inspiration

10. Direction of arrow

11. Arrow direction

12. Direction of arrow

13. Direction of arrow

14. evacuated housing

15. Photocathode

16. Microchannel plate

17.Luminescent screen

18. Arrow direction

19.Light quant

20th channel

21. Arrow direction

22. Interior

23. Interior

24. Electronic avalanche

25. Excitation pulse

26th response impulse

27. Evaluation time

28. Coded area

29. Selection field

30. Register mark

31. Radiation source

32. X-rays

33. Housing

34th barrier

35. Electron

36. Arrow direction

37th area

38. Direction of the arrow

Claims

15 patent claims

1. Verification system for a value and security product, on which one or more security elements are arranged, which consist of weakly emitting, patterned and excitable substances with defined spectral properties, the emission of which is made visible with an optical imaging device, characterized in that the optical imaging device is a multi-channel amplifier (MCBV).

2. Verification system according to claim 1, characterized in that the multi-channel amplifier has a spatial resolution due to the packing density of the channels (20), which is in the range between about 10 and 20 microns.

3. Verification system according to claim 2, characterized in that the input of an electronic camera is arranged at the output of the multi-channel amplifier.

4. Verification system according to claim 3, characterized in that with an image field of the value and security document to be verified of 1 - 3 qcm, the output of the multi-channel amplifier is directly connected to the photocathode of the electronic camera in a light-conducting connection.

5. Value and security product, in particular with verification system according to one of claims 1-4, on which one or more security elements are arranged and / or embedded, characterized in that the security elements (2, 3) as an admixture of the smallest amounts of contrast, Fluorescent or luminescent substances are formed in the printing ink and / or the substrate.

6. Value and security product according to claim 5, characterized in that a certain areal distribution of the security elements (2,3) is provided.

7. Value and security product according to claim 5 or 6, characterized in that a reference surface (28) is provided which is delimited by one or more register marks (30). 16

8. value and security product according to claim 7, characterized in that in addition a read-out field (29) is present in which a checksum is stored for the reference surface (28).

9. Value and security product according to one of the preceding claims, characterized in that the security elements are designed as external luminous, needing excitation markings.

10. Value and security product according to claim 9, characterized in that the security elements (2,3) have an extremely short response time.

11. Value and security product according to claim 9 or 10, characterized in that the security elements (2,3) require a high excitation energy.

12. Value and security product according to one of claims 9 to 11, characterized in that the security elements (2,3) emit an extremely short response signal.

13. Value and security product according to one of claims 9 to 12, characterized in that the response signal is in a different frequency range than the excitation signal.

14. Value and security product according to one of the preceding claims, characterized in that at least one of the security elements (2, 3) is attached to the edge or on an edge of the value document (1).

15. A method for evaluating and testing a value and security product according to one of the preceding claims, characterized by the use of an optical multi-channel amplifier.

16. The method according to claim 15, characterized in that a parallel evaluation and testing of several valuable and security products (1) takes place simultaneously.

17. The method according to claim 15 or 16, characterized in that the optical multi-channel amplifier has a sensor surface which is adapted to 3 in the characteristic dimensions of a security element.

18. The method according to any one of claims 15 to 17, characterized in that the optical multi-channel amplifier has a high sensitivity, high resolution and short switching times.

19. The method according to any one of claims 1 to 18, characterized in that an adjustment of the optical multi-channel amplifier to a certain wavelength is provided by selection of a suitable photocathode.