WO2021013759A1

WO2021013759A1 - Method for evaluating volatile non-resistant anti-stokes luminescent substances on value documents

Info

Publication number: WO2021013759A1
Application number: PCT/EP2020/070373
Authority: WO
Inventors: Florian Peters; Andreas Deichsel
Original assignee: Bundesdruckerei Gmbh
Priority date: 2019-07-19
Filing date: 2020-07-17
Publication date: 2021-01-28
Also published as: EP3999356A1; DE102019210762A1

Abstract

The invention relates to a security element (2) with a pattern (110) made of pattern regions (120) as a security feature (100). The pattern regions (120) comprise at least one first pattern region (121, 121-x) and a second pattern region (122, 122-x), and the first pattern region (121, 121-x) and the second pattern region (122, 122-x) have an anti-Stokes luminescent substance (200) in a non-manipulated state of the security element (2), said luminescent substance exhibiting a luminescence in an anti-Stokes wavelength range when excited with a light signal (407) with a wavelength in an excitation wavelength range. The first pattern region (121, 121-x) and the second pattern region (122, 122-x) differ in that the content of anti-Stokes luminescent material (200) which can be removed from the security element (2) by manipulation is greater in the second pattern region (122, 122-x) than in the first pattern region (121, 121-x). The invention additionally relates to a verification method and a device for verifying such a security element (2), wherein an evaluation of the anti-Stokes luminescence is carried out via a respective communication attachment.

Description

Method for evaluating volatile, non-resistant Anti-Stokes luminescent substances on documents of value

The invention relates to a method for verifying security elements which comprise anti-Stokes luminescent substances, as well as a device for verifying such security elements and the security elements themselves.

From EP 1 241 242 A2, anti-Stokes phosphors for use in security documents are known. Such anti-Stokes fluorescent substances belong to the group of photoluminescent substances, which can be excited to emit electromagnetic luminescent radiation by being excited with electromagnetic radiation. Anti-Stokes phosphors absorb electromagnetic radiation of a wavelength which is referred to as the excitation wavelength, and emit at least part of the luminescence radiation at an anti-Stokes wavelength which is shorter than the excitation wavelength.

EP 1 241 242 A2 indicates that the rise times and / or fall times of the anti-Stokes luminescent light can be evaluated for an automatic detection of the anti-Stokes luminescent material. The rise times and / or fall times are characteristic of the various anti-Stokes phosphors. It is also known that the attack times of anti-Stokes phosphors are relatively long compared to many other luminescent materials and can be up to a few 100 ps.

Security documents are known from the prior art in which anti-Stokes luminescent substances are integrated into security features and an anti-Stokes luminescence and, if appropriate, their special characteristics are used as security features. In the simplest verification, it is only checked whether anti-Stokes luminescence can be detected.

In a further developed embodiment, for example, the rise time and / or fall time are evaluated and, on the basis of this evaluation, it is checked whether the checked security document contains the correct anti-Stokes luminescent substances for a genuine security document. Since, with increasing technical progress, forgers of security documents are put in a position to imitate increasingly complex security features and / or to reproduce, as these anti-Stokes luminescent substances are comprehensive security features, it is an endeavor of the security document manufacturers to use ever more complex security features which are nevertheless reliable should be verifiable. In addition, it is desirable to be able to detect manipulations of security elements.

In the case of stamps that are attached to documents or objects with an adhesive and are intended for single use, it is, for example, a problem that they can be detached and reused. Various measures can be taken to prevent this. Postage stamps are, for example, canceled by printing or stamping print information. When processing in sorting and / or cancellation machines, however, it can happen that individual postage stamps are not canceled. Furthermore, it is partly possible to remove the print information again. Detached postage stamps which have been manipulated by detachment from the originally transported mail item and / or by removal of the printing information used for cancellation are thus used again.

Other security elements, such as labels, Visa stamps, etc., which are applied to documents or objects for security purposes, can also be manipulated in a similar way and used without authorization.

The invention is based on the object of being able to recognize and / or prevent such manipulations.

Basic idea of the invention

The invention is based on the idea of creating a security element which comprises an anti-Stokes luminescent substance. A part of the anti-Stokes luminescent substance is applied to or integrated into the security element in such a way that this portion is removed from the security element during a manipulation process. Another part of the anti-Stokes luminescent substance is applied to the security element or integrated into the security element in such a way that it is manipulated in the event of a manipulation of the security element. elements is not removed. It is provided that the security element comprises a pattern formed from pattern areas as a security feature, the pattern areas comprising at least two types of pattern areas in each of which, preferably homogeneously, an anti-Stokes luminescent substance is applied and / or incorporated. The pattern areas differ in that a relative proportion of the anti-Stokes luminescent substance which can be removed from the corresponding pattern area during manipulation is greater for one type of pattern area than for the respective pattern areas of the other type. In the following, the pattern areas of the one type whose relative proportion of removable anti-Stokes luminescent substance is greater than that of the other type of pattern areas, without loss of generality, are referred to as second pattern areas and the pattern areas which have a smaller relative proportion have anti-Stokes luminescent substance removable during manipulation, referred to as first pattern areas. The relative proportion of the anti-Stokes luminescent substance that can be removed during the manipulation is the ratio of the anti-Stokes luminescent substance that can be removed during the manipulation to the total amount of the anti-Stokes luminescent substance in the corresponding pattern area before a manipulation, ie in the case of a real and intact Security element, defined. The portion of the anti-Stokes luminescent substance that can be removed during manipulation can be zero for one type of pattern. The security element thus comprises a pattern which, when evaluating the anti-Stokes luminescence, can be detected in the manipulated state, in the non-manipulated state or in both states as consisting of different pattern areas.

In order to be able to reliably verify such a security element, especially in situations in which the time available for the verification is tight, according to one aspect of the invention an excitation of the anti-Stokes luminescence in the pattern areas, a detection of the anti -Stokes luminescence and conversion into an output signal, the amplitude of which is a measure of the detected anti-Stokes luminescence light intensity, understood and evaluated as a communication process. This reduces the time required for an evaluation and increases the accuracy of the check for the presence of a specific anti-Stokes luminescent substance. This creates the possibility, on the one hand, of verifying whether the detected anti-Stokes luminescence originates from a certain, expected anti-Stokes luminescence substance, when the anti-Stokes luminescence is scanned or scanned, which is used in the patterns of real security elements. In this way, real security elements can thus be protected against forgeries in which an anti-Stokes luminescence security feature is formed, but this is not produced with the correct anti-Stokes luminescence substance. In addition, however, the possibility is also created to identify the different pattern areas either in the case of manipulated security elements, in the case of non-manipulated security elements or in both manipulated and non-manipulated security elements and to determine a manipulation of security elements based on information about the real pattern of a real security element, which are caused by a manipulation action, for example a detachment and reuse of the security element, on an originally genuine security element.

With a verification device which is designed to excite the anti-Stokes luminescence and to detect the anti-Stokes luminescent light and to carry out such a technical evaluation, it is possible to carry out a verification of these novel security elements.

In order to consider the verification process in terms of communication technology, the verification of the security feature with the anti-Stokes luminescence is initially divided into different sections. On the one hand, during the verification there is an excitation with electromagnetic radiation in an excitation wavelength range which can be in the infrared (IR), visible or ultraviolet (UV) wavelength range. This electro-magnetic radiation then causes a physical reaction of the security feature to be verified in the form of a luminescence response, ie an emission of anti-Stokes luminescence. This is recorded with a measuring device, which provides an output signal. It has proven advantageous to understand the luminescence response of the security feature, including the measuring apparatus, which detects the anti-Stokes luminescence and converts it into an output signal, as a signal transmission path and to model it using a characteristic function. This characteristic function, the shape of which is essentially dependent on the anti-Stokes luminescent substance, represents a system response to an optical standard excitation with electromagnetic radiation from the excitation wavelength range of the anti-Stokes luminescent substance placed on or in a pattern area In the characteristic function, all influences of the security feature as well as the measuring equipment and signal conversion up to the generated output signal are combined. collected. The characteristic function is thus preferably a system response, also called a standard system response, to a standardized stimulus. For example, the characteristic function describes the step response in the verification of an anti-Stokes luminescent substance in a real security feature, which occurs in the case of a sudden and otherwise constant excitation with predetermined excitation radiation in the measurement signal of the luminescence light intensity of the verification device used for the verification. In the practical case, an impulse response can also be used instead of a step response. This represents the response of the measurement signal to an excitation with an excitation radiation, the intensity of which can be specified by a function describing a pulse, e.g. B. a right corner function or a triangle function.

Such a characteristic function can be determined from measurements and / or numerical simulations.

It has been shown that based on the output signal detected by the measuring apparatus and the characteristic function it is possible to determine whether the output signal represents the response of the security feature expected for the excitation used and thus to verify whether it is at the place where the excitation was made is made, the fluorescent substance corresponding to the characteristic function is contained in the security feature or not.

With this method it is possible to make the excitation variable and to carry out measurements without a completely steady and stable state. For example, information can be transmitted in the form of symbols.

In the following, a symbol is intended to denote a single character unit for transmitting information content. A symbol has a specific symbol shape. In particular, a symbol is to be understood here in the sense of communications technology, a transmission unit for transmitting data sending symbols over a transmission channel and a receiving unit recognizing these symbols and reconstructing the transmitted data.

If the characteristic function is known, it is now possible, for example, to control the excitation via an input signal in which information in the form of symbols len are stored or coded. A symbol is defined via a function of the envelope of the intensity of the electromagnetic excitation radiation in the time domain, ie via a function which indicates the intensity of the electromagnetic excitation radiation as a function of time. During verification it can now be checked whether symbols can be recognized in the output signal or the signal received after the evaluation. It will not be necessary in every case to determine the sequence of symbols yourself. Even knowledge of the symbol shape is sufficient to be able to determine whether a symbol sequence is contained in the evaluated output signal. This alone is sufficient to achieve an improved signal-to-noise ratio compared to the classic measurement methods in the prior art and thus to significantly increase the selectivity in the verification as well as a verification speed and a spatial resolution capability of the verification.

Definitions

Luminescence is the physical property of a substance to show an emission of electromagnetic radiation after being stimulated. The electromagnetic radiation generated during luminescence is also referred to as luminescence radiation or luminescence light. The wavelengths of the luminescence radiation can be in the infrared wavelength range, in the visible wavelength range and / or in the UV wavelength range.

If the excitation of the luminescence takes place by means of light in the infrared wavelength range, visible wavelength range or in the UV wavelength range, the luminescence is also referred to as photoluminescence. As a rule, the wavelength of the luminescent light is greater than the wavelength of the excitation light which is used to excite the luminescent substance.

However, physical processes in a luminescent substance are also possible which lead to the luminescent light having a shorter wavelength than the excitation light used for excitation. Such luminescence is referred to as anti-Stokes luminescence or also as up-conversion luminescence or upconversion for short, since the energy of an emitted anti-Stokes luminescence photon is higher than the energy of the photons of the excitation light. A pattern is an arrangement of pattern areas, which are also referred to as pattern elements, relative to one another in space. The pattern areas can have the same properties or be different from one another. Pattern areas can, for example, be areas that have a certain property. Shapes and arrangement of areas, which show a certain anti-Stokes luminescence, for example when excited with an excitation wavelength, on a surface of a security feature define, for example, a pattern. A pattern that shows up in the investigation of the anti-Stokes luminescence consists of pattern areas or pattern elements, which are flat areas that are based on the anti-Stokes luminescence in the non-manipulated state, in the manipulated state, or both Differentiate between states. A pattern area comprises a contiguous area, the same anti-Stokes luminescence being observable at every location in the area. A surface that has the same observable / measurable properties with regard to the anti-Stokes luminescence in all locations in both the unmanipulated and the manipulated state has no pattern in the sense of what is described here. A pattern must therefore have at least two pattern areas or pattern elements that have a measurable property for the anti-Stokes luminescence described here in one of the two or both states, ie in the unmanipulated state, in the manipulated state or in both states , must distinguish.

Genuine security features always have at least two different pattern areas, each of which shows an anti-Stokes luminescence in the non-manipulated state, but whose anti-Stokes luminescence is different in at least one of the two states. Patterns can have more pattern areas than the at least two pattern areas. Their anti-Stokes luminescence can match that of one of the at least two pattern areas or also be different from their anti-Stokes luminescence. Likewise, in some embodiments, areas may also exist that do not have anti-Stokes luminescence.

Anti-Stokes luminescent substances are different in the sense of the invention described here if the luminescence intensities of the anti-Stokes luminescent substances integrated over a given anti-Stokes luminescence wavelength range have different time behavior with the same excitation. The anti-Stokes luminescence of a pattern area differs from the anti-Stokes luminescence of another pattern area if the luminescence shows a deviating time behavior or if the luminescence intensities are different for the same excitation, i.e. by a definable value, for example by more than 20 %, more than 50%, more than 200% or more than 500% (each based on the Intensi ity of the area with the lower luminescence intensity).

The fact that an anti-Stokes luminescent substance can be removed during manipulation means that it can be removed from the substrate or another physical unit that forms the security element during an action, for example detaching the security element from an object, e.g. a postage stamp from a letter , is removed without the substrate or the other physical unit being neither removed nor reduced in its dimensions (except for a change in layer thickness of the layer in which the anti-Stokes luminescent substance is applied). As a rule, the manipulation will not be detectable by visual inspection by a human observer or by an image recognition evaluation of a pictorial image recorded in the visible wavelength range. An anti-Stokes luminescent substance can be removed, for example, because the preparation with which the anti-Stokes luminescent substance is applied to or integrated into the security element, or the resulting layer, in a fluid that is used to detach the security element , is detachable or has a low abrasion resistance or shows a low stability to the action of heat and, for example, when exposed to heat, shows a tendency to transition into the gaseous or liquid phase, ie tends to evaporate or sublimate, the anti-Stokes luminescent substance with the preparation or the resulting layer is removed or escapes from it. An anti-Stokes luminescent substance cannot be removed, for example, if the preparation with which the anti-Stokes luminescent substance is applied to or integrated into the security element, or the resulting layer has a high level of stability with respect to the environmental influences during manipulation, For example, abrasion-resistant, non-detachable and heat-resistant, in each case at least to the extent that occurs in the event of a manipulation which otherwise does not impair the security element or does not noticeably impair it. It is essential for the invention that the anti-Stokes luminescent substance is introduced into a sample area in such a way that it is removed due to the environmental influences occurring during the manipulation and is not removed in another sample area due to the same environmental influences. A characteristic function of an anti-Stokes luminescent substance indicates the functional relationship between a predetermined standardized excitation of the anti-Stokes luminescent substance in a real security feature and a measurement signal generated during verification in a verification device. If an anti-Stokes luminescence in an area of a security element is determined not only by an anti-Stokes luminescent substance, but also by a combination of anti-Stokes luminescent substances, this combination of luminescent substances can also be assigned a characteristic function accordingly indicates the functional relationship between the specified standardized excitation of the combination of the anti-Stokes luminescent substances in a real security feature and a measurement signal during the verification in the verification device.

Preferred Embodiments

In particular, a method for verifying security elements is created which comprises a pattern formed from pattern areas as a security feature, the pattern areas at least

one or more first pattern areas and

comprise one or more second pattern areas,

an anti-Stokes luminescent substance being present both in the one or more first pattern areas and in the one or more second pattern areas in a non-manipulated state of the security element, the anti-Stokes luminescent substance when excited with a light signal whose wavelength or wavelengths lie in an excitation wavelength range shows anti-Stokes luminescence in an anti-Stokes wavelength range,

wherein the one or more second pattern areas differ from the one or more first pattern areas in that a relative proportion of the anti-Stokes luminescent substance, which can be removed from the corresponding pattern area during manipulation, is used for the second pattern area or the second several pattern areas is larger than for the respective first pattern area or the respective several first pattern areas,

comprehensive the steps:

Generating a light signal which is intensity-modulated over time according to an input signal, the wavelength or wavelengths of which are in the excitation wavelength range and Irradiating the light signal into a limited illumination area;

Providing one of the security elements;

Moving the one of the security elements relative to the illuminated area so that the illuminated area sweeps over different of the at least two pattern areas of the graphic pattern of the security element over time;

iterative detection of luminescent light in the anti-Stokes wavelength range and conversion into an output signal which represents an intensity of the detected luminescent light,

Transforming the output signal by means of at least one provided characteristic function by an evaluation device into a transformed output signal, evaluating the transformed output signal taking into account at least one input signal information item of the input signal for the

Deriving recognition decisions for the anti-Stokes luminescent substance by the evaluation device,

Deriving a verification decision based on the detection decisions and

Output of the verification decision by the evaluation device.

One advantage over the embodiments in the prior art is that a much more rapid decision can be made about the existence or non-existence of an anti-Stokes luminescent substance in the currently illuminated area or the area that was illuminated shortly before.

A device for verifying security elements with a pattern formed from pattern areas as a security feature, wherein the pattern areas comprise an anti-Stokes luminescent substance, comprises:

a control device for generating an input signal,

an excitation source for generating a light signal intensity-modulated in terms of time according to the input signal, the wavelength or wavelengths of which are in the excitation wavelength range, and for irradiating the light signal into a limited lighting area,

a scanning device coupled to the control device for relative movement of the one of the security elements and the illuminated area, so that the illuminated area sweeps over different of the at least two pattern areas of the graphic pattern of the security element over time; a detection device for iteratively detecting luminescent light in the anti-Stokes wavelength range and converting it into an output signal which represents an intensity of the detected luminescent light,

and an evaluation device which comprises a transformation module for transforming the output signal by means of at least one provided characteristic function into a transformed output signal and is designed to derive recognition decisions for the anti-Stokes luminescent substance when evaluating the transformed output signal taking into account at least one input signal information of the input signal and for Deriving a verification decision based on the detection decisions and

an output device for outputting the verification decision of the evaluation device.

Furthermore, a security element is created with a pattern formed from pattern areas as a security feature,

the pattern areas at least

comprise a first pattern area and a second pattern area

wherein the first pattern area and the second pattern area in a non-manipulated state of the security element have an anti-Stokes luminescent substance which, when excited by a light signal with a wavelength or wavelengths in an excitation wavelength range, exhibits luminescence in an anti-Stokes wavelength range,

wherein the first and the second pattern area differ in that a proportion of the anti-Stokes luminescent substance which can be removed from the security element in the event of manipulation is greater in the second pattern area than in the first pattern area. The proportion of the anti-Stokes luminescent substance is related to the total amount in the respective pattern area of a security element that has not been manipulated.

One embodiment of the security element provides that the surface concentrations of the anti-Stokes luminescent substance in the first pattern area and in the second pattern area are the same in the non-manipulated state. In this way, it can be established during verification that the overall pattern formed from the first pattern area and the second pattern area or one or more first pattern areas and one or more second pattern areas has the expected anti-Stokes luminescence at all positions in the unmanipulated state of the security element shows, ie the existence of the expected anti-Stokes luminescent substance is detected. In this case, the pattern in the non-manipulated state is a surface which uniformly has a homogeneous anti-Stokes luminescence.

If a security element is manipulated, for example a postage stamp is removed, in the second pattern area of which the anti-Stokes luminescent substance is applied by means of a water-soluble or vapor-soluble preparation, the anti-Stokes luminescent substance is at least partially or completely removed in the second pattern area (s) away.

If, in the manipulated state, the anti-Stokes luminescent substance is then completely removed in the one or more second sample areas, for example, the absence, i.e. the non-existence, of the anti-Stokes luminescent substance is determined in this area or these areas during the verification. Manipulation can be recognized by this.

Patterns which, when manipulated, the anti-Stokes luminescent substance in the second pattern area is completely removed, preferably comprise a sequence of pattern areas of the type: first pattern area - second pattern area - first pattern area. Manipulations on such security elements can be scanned during the verification independently of the orientation, that is to say in two opposite directions, without this impairing the detection reliability. Manipulations can thus be detected very reliably.

In the case of security elements whose pattern only consists of the sequence of the first pattern area - second pattern area or the sequence of the second pattern area - first pattern area - second pattern area, manipulations can also be detected if the extent of the area in which the correct anti-Stokes luminescence is detected , is evaluated with and compared with specifications for a real security element.

One embodiment therefore provides that the evaluation involves creating a detection pattern based on the recognition decisions derived in chronological order, taking into account the movement of the illuminated area relative to the security element, and deriving the verification decision based on a comparison of the detection pattern with a specified authenticity or forgery pattern respectively. The verification reliability is further increased, as is “hiding” of the feature in embodiments in which the method of verification provides that the deriving of the recognition decisions involves establishing the existence and determining and ascertaining a correct (ie expected) anti-Stokes protection. Luminescent substance assignable luminescence intensity includes, which is a measure of the amount of the expected, ie the correct, anti-Stokes luminescent substance in the illuminated area.

During the evaluation, the recorded output signal is usually normalized. If the concentration of the anti-Stokes luminescent substance changes from one sample area to the next, ie for example from a first sample area to a second sample area or vice versa, this is noticeable in the evaluation because the normalization requires an adjustment or at least would be advantageous . This is comparable to changing the measuring range on a measuring device when a size of the measured signal changes significantly in order to ensure optimal measurement value acquisition.

With such an embodiment, patterns can also be very reliably verified in which all pattern areas have the anti-Stokes luminescent substance both in the manipulation and in the non-manipulated state or in which the manipulation does not have the entire removable portion of the anti-Stokes -Luminescent substance is removed. However, in at least one state, the concentrations of the anti-Stokes luminescent substance differ in the various pattern areas. Without a precise analysis, however, this is often not recognizable, since the anti-Stokes luminescence can be observed / measured over the entire surface in every state in the first and second pattern areas of the pattern when excited. Thus the security feature is hidden from here.

One embodiment of the security element therefore provides that the anti-Stokes luminescent substance of the second pattern area cannot be completely removed during manipulation.

In order to be able to reliably detect the different areas of the security element that show different anti-Stokes luminescence, during the illumination When the security element passes over the security element, it has proven to be advantageous to generate the time-intensity-modulated light signal according to the input signal in such a way that the intensity of the light signal is modulated according to a recurring light excitation intensity pattern. The input signal thus repeatedly specifies the same light excitation intensity pattern. Information that is recurrently contained in the recurring light excitation intensity pattern can be used to identify whether this information about the triggered anti-Stokes luminescence has been transferred into the output signal during the verification. If this is the case, the correct anti-Stokes luminescent substance is present in the corresponding area.

A light excitation intensity pattern reflects the intensity of the excitation light over the course of the light excitation. In the context described here, a light excitation intensity pattern is assigned to an information unit, which is also referred to as a symbol. The light signal, which is modulated according to a light excitation intensity pattern and which is used for excitation, thus represents a symbol. If the light signal is iteratively modulated with the same light excitation intensity pattern, the same information is transmitted multiple times via the security element to the evaluation device.

In order to obtain a robust evaluation, it is provided in one embodiment that the light signal used for the excitation is temporally modulated in such a way that symbols are transmitted iteratively.

The evaluation is simplified if the symbols transmitted iteratively have the same symbol shape.

In order to minimize symbol interference in the sense of message transmission by means of modulation of the light signal, it is preferably provided that the symbols each include an excitation component and a non-excitation component. In the non-excitation component, which is also referred to as the pause component, the light signal has no intensity or an intensity that is not suitable for stimulating anti-Stokes luminescence. By providing the non-excitation component, intersymbol interference is significantly minimized in the evaluation. Embodiments have proven to be advantageous in which the excitation component consists of a linear increase in intensity and a subsequent linear decrease in intensity. Preferably the intensity increases from zero and the intensity decreases to zero.

The excitation component can thus preferably be described by a triangular signal. The light intensity initially increases linearly up to a maximum value and then decreases linearly again. The linear gradients are preferably the same in terms of amount for rise and fall, but have different signs. The excitation component thus represents two sides of an isosceles triangle.

In order to achieve a high level of reliability in the pattern recognition, it is advantageous to transmit several symbols while the illuminated area sweeps over, i.e. scans, a pattern area. In order to enable a reliable identification of the different areas, it is seen in one embodiment that the modulation of the light signal is coordinated with a movement speed of one of the security elements relative to the illuminated area and an extension of the illuminated area along the direction of movement of the security element according to several, preferably 2 to 10, more preferably 3 to 7, symbols (light excitation intensity patterns) following one another in time in the time span in which a point of one of the security elements moves through the excitation area or in which the excitation area is a point of one of the security elements over strokes.

One embodiment therefore provides that the relative movement of the illuminated area and the security element at one speed and the modulation of the light signals taking into account an extension of the pattern areas parallel to the relative direction of movement are coordinated so that the anti-Stokes luminescent substance during the Relative movement of the illuminated area over the respective pattern area is stimulated with a minimum number of symbols modulated on the light signal, the minimum number being greater than 2.

The minimum number of symbols is preferably greater than or equal to 5.

The anti-Stokes luminescence is preferably detected at a frequency that is a factor of 20, preferably a factor of 100 or more, greater than a symbol is the frequency with which symbols are modulated onto the light signal. This enables sufficient resolution of the transmitted symbol shape to ensure reliable anti-Stokes luminescent substance detection.

Advantageous embodiments of the security element provide that the pattern comprises several first pattern areas that are identical to the one first pattern area and / or several second pattern areas that are similar to the one second pattern area.

In particular, patterns can be formed in which the anti-Stokes luminescent substance concentration fluctuates alternately between the first and second pattern areas at least in one of the states.

The pattern area which is first illuminated in time is preferably a first pattern area in which at least a large proportion of the anti-Stokes luminescent substance cannot be removed, in particular cannot be removed, applied or introduced. This creates the possibility of first setting an appropriate standardization for the verification process in the evaluation and / or an excitation intensity of the light signal, in which an optimal evaluation is possible. If the luminescence intensity is too low, an intensity of the light signal can be increased.

For this it is advantageous if several symbols are transmitted via the anti-Stokes luminescent substance of a pattern area while this is being scanned.

If, after a normalization and excitation intensity have been selected, a transition to another pattern area that differs from this occurs, the occurring change in intensity can be reliably recognized, e.g. from the need for a normalization adjustment or the need to adjust the excitation intensity of the light signal. Here, too, it is advantageous if several symbols are transmitted while a pattern area is being scanned with the illuminated area.

In one embodiment of the security element, the surface concentrations of the anti-Stokes luminescent substance in the first pattern area and in the second pattern area, which cannot be removed, are the same. In the manipulated state, there is then a uniform luminescence in the first pattern areas and the second pattern areas to observe. In the non-manipulated state, however, the surface concentration of the anti-Stokes luminescent substance is greater in the second pattern area or areas than in the first pattern area or areas.

The area concentrations are preferably selected in such a way that in the non-manipulated state the area concentrations differ from one another by a factor of 2 or more. Thus, the intensity of the anti-Stokes luminescence increases sharply at the transition from the first pattern area to a second pattern area, unless an excitation intensity is adjusted. For example, the measuring device can become saturated, i.e. a preferably linear range can be exceeded in which the output signal generated is a measure of the anti-Stokes luminescence detected. In this case, the occurrence of saturation can be used to identify the second areas. As a rule, however, the detection of the specific anti-Stokes luminescent substance is limited or impossible in the saturation, so that the intensity of the light signal is adjusted in order to check its “identity”. For this purpose, as stated above, it is checked whether one or more symbols are transmitted in the output signal as expected after an excitation intensity adjustment.

This light signal adaptation can be done proactively, i. H. before saturation of the measuring device is expected to occur. The excitation intensity can thus be adapted to an expected pattern of the security element to be verified.

Particularly preferred are embodiments in which the surface concentrations of the anti-Stokes luminescent substance in the first pattern area and in the second pattern area are neither the same in the non-manipulated state nor in the manipulated state, so that both in the non-manipulated state and in the manipulated state the different pattern areas can be detected using the anti-Stokes luminescence. For example, the anti-Stokes luminescent substance is exclusively applied or incorporated in the first pattern areas in a non-removable manner. The proportion of non-removable anti-Stokes luminescent substance in the second pattern area, however, is significantly lower or zero. The removable applied or introduced portion is, however, selected in the second pattern area, for example, so that the surface concentration of the anti-Stokes luminescent substance in the non-manipulated state in the second pattern area is significantly greater than in the first pattern area. This relationship is then reversed in the manipulated state. A security element is preferably designed such that there is a detection direction with respect to which the first and second pattern areas alternate in the pattern and the first and the last of the pattern areas along the detection direction are either a first pattern area or a second pattern area.

One embodiment provides that, in the non-manipulated state of the security element, there are no areas within the pattern between the pattern areas that do not have the anti-Stokes luminescent substance. In this way, an expansion of the entire pattern can be automatically recognized, at least in the non-manipulated state.

In a preferred embodiment, security features are designed in such a way that the graphic pattern recognizable during an evaluation of the anti-Stokes luminescence in the anti-Stokes luminescence wavelength range cannot be recognized by a human observer when excited with electromagnetic radiation in the excitation wavelength range, because, for example, in addition to the anti-Stokes luminescence, a “normal” photoluminescence occurs in the area of the pattern.

“Normal” photoluminescence occurs, for example, when the anti-Stokes luminescent substance shows a “normal” photoluminescence in addition to the anti-Stokes luminescence. Furthermore, a luminescent substance can be applied or brought over the pattern areas, which when the anti-Stokes luminescence is excited in the wavelength range whose wavelength is greater than that of the anti-Stokes luminescence, “normal” photo luminescence, which preferably shows a higher intensity in the human perceptible wavelength range or over the entire emission wavelength range, including the anti-Stokes luminescence wavelength range, so that the intensity differences of the pattern due to the luminescence of the anti-Stokes luminescent substance of the security element neither in the non-manipulated nor in the manipulated State are perceptible, that is, the luminescence of the anti-Stokes luminescent substance is preferably at least one or more orders of magnitude smaller than the luminescence of the other luminescent substance.

In order to evaluate the anti-Stokes luminescence through such "normal" luminescence or other light emissions outside the anti-Stokes luminescence Not to be disturbed in the wavelength range, one embodiment provides that the luminescent light emitted by the security feature is filtered in a wavelength-selective manner. A verification device has a filter for this purpose. Particularly preferably an edge filter is used which attenuates light emitted by the security feature with a wavelength which is greater than a largest wavelength of the Anti-Stokes wavelength range by one, preferably several orders of magnitude and most preferably completely in intensity.

In one embodiment it is provided that the at least two areas of the graphic's pattern when excited with the same light signal in the excitation wavelength range for the anti-Stokes luminescence each show a luminescence in the visible wavelength range, which produce the same color impression for a human observer.

When the light signal provided for the verification is irradiated to excite the anti-Stokes luminescence, the graphic pattern is thus hidden from the viewer. He can indeed recognize that a luminescence security feature is present, but not that this has a graphic pattern which can be detected if the luminescence is only evaluated in the anti-Stokes luminescence wavelength range.

Embodiments are also possible in which the extent of the illuminated area along the direction of movement of the security element is smaller than an extent of the security element along the direction of movement.

The iterative detection of the anti-Stokes luminescence is preferably carried out at time intervals which are at least one order of magnitude, more preferably at least two orders of magnitude smaller than a duration of the excitation component of the light excitation intensity pattern.

The invention is explained in more detail below with reference to a drawing. Here show: Fig. 1 is a schematic representation of an embodiment of a device for verifying a security element on a value or security document;

FIG. 2 shows a schematic plan view of a security element according to FIG. 1;

3a shows a graphic representation of an area concentration of an anti-Stokes luminescent substance along an x direction of a security element in the non-manipulated state;

3b shows a graphic representation of an area concentration of an anti-Stokes luminescent substance along an x direction of a security element in the manipulated state;

4a shows a schematic representation of a security element;

4b shows a schematic graphic representation of the surface concentration of the anti-Stokes luminescent substance versus an expansion of the pattern of a security element along a spatial direction in the non-manipulated state;

4c shows a schematic graphic representation of the surface concentration of the anti-Stokes luminescent substance versus an expansion of the pattern of a security element along a spatial direction in the manipulated state;

4d shows a schematic representation of an intensity of the input signal for stimulating the modulation of the light signal plotted against time;

4e, in simplified form, a graphical representation of an intensity of the light signal used for excitation, plotted against time;

4f shows a greatly simplified representation of the recorded anti-Stokes

Luminescence light intensity for a security element in the non-manipulated state plotted against time; FIG. 4g shows a greatly simplified graphic representation of the normalization value determined for the recorded anti-Stokes luminescence light intensity according to FIG. 4f plotted against time; FIG.

4h shows a schematic representation of an input signal, only the maximum amplitude of the transmitted symbols being plotted for simplification;

FIG. 4i shows a greatly simplified representation of the anti-Stokes luminescence light intensity for an unmanipulated security element during the excitation according to the input signal according to FIG. 4h; and

4j shows a greatly simplified representation of the anti-Stokes luminescence light intensity for a manipulated security element when excited according to the input signal according to FIG. 4h.

1 shows a schematic representation of an embodiment of the device 1 for verifying a security element 2 having anti-Stokes luminescence on a value or security document 3. The device 1 comprises an excitation device 4, a detection device 5 and an evaluation device 6.

The excitation device 4 comprises a light source 401, which is preferably designed as a laser. The excitation device 4 generates a light signal 407.

The value or security document 3 is arranged on a transport device 7.

The transport device 7 moves the value or security document 3 on which the security element 2 is located, preferably along a spatial direction 91. The movement is preferably carried out at a constant speed in one direction of movement.

Alternatively or in addition to the transport device 7, a relative movement of the illuminated area relative to the security element 2 can take place via a deflection unit 119, for example an adjustable, controllable mirror or the like. A control device 17 controls the transport device 7 and the excitation device 4 and, if necessary, such a deflection unit 119, which in some embodiments completely replaces the transport device. The excitation device 4 is designed to generate a light signal 407 and to use this to illuminate an illumination area 71 on the value or security document 3 or the security element 2 located thereon. The illuminated area 71 is preferably designed as a narrow strip or rectangular area which is larger than the security element 2 transversely to the spatial direction 91 transversely to the spatial direction 91 along which the value or security document 3 and thus also the security element 2 are moved This ensures that the full security element is detected in each case.

However, embodiments are also possible in which an extension of the illumination area 71 transversely to the spatial direction 91 is smaller than the extension of the safety element 2 transversely to the spatial direction.

The excitation device 4 is thus arranged relative to the transport device 7 in such a way that the light signal 407 generated by the excitation device 4 with the generated illumination area 71 sweeps over or scans the security element 2 when the value or security document 3 is moved. In other embodiments, the relative movement between the illuminated area 71 and the security element 2 can be brought about or only brought about by the optical deflection unit 119. The transport device 7 and / or the deflection unit 119 form a scanning device 138 which effects the scanning of the security element 2 with the illuminated area 71.

The security element 2 comprises a pattern 110 as a security feature 100. The pattern 110 comprises a plurality of pattern areas 120. The pattern areas 120 include at least two different types of pattern areas. One type of pattern area is hereinafter referred to as first pattern area 121 and the other type of pattern area is referred to as second pattern area 122. The assignment of the ordinal numbers first and second is arbitrary. In the area of both the first pattern areas 121 and the second pattern areas 122, an anti-Stokes luminescent substance 200 is applied on or into the security element. In this case, the anti-Stokes luminescent substance 200 is applied or incorporated in the pattern areas 120 in each case based on the corresponding one of the pattern areas 120, preferably distributed homogeneously.

The anti-Stokes luminescent substance 200 is applied or incorporated in or onto the pattern areas 120 in two different ways. At least some of the Anti-Stokes Luminescent substance 200 is applied or introduced into second pattern regions 122 in such a way that this portion is removed when the security element 2 is manipulated. For example, the portion of the anti-Stokes luminescent substance 200 that can be removed during the manipulation is applied, preferably printed, to the security element 2 in the second pattern areas 122 by means of a water-soluble preparation. The anti-Stokes luminescent substance 200 with a non-removable, in particular non-detachable, preparation is applied to the first pattern areas 121. The anti-Stokes luminescent substance 200 applied with the non-releasable preparation is not removed from the security element 2 in the event of a manipulation.

The anti-Stokes luminescent substance 200 is shown in each case by hatching. Hatching from bottom left to top right indicates that the anti-Stokes luminescent substance 200 cannot be removed during manipulation, e.g. B. is applied or brought in with a non-soluble preparation. On the other hand, hatching from top left to bottom right can be removed during manipulation, e.g. B. applied or introduced with a releasable preparation. For better illustration, the first pattern area 121 are marked with an “I” and the second pattern area 122 with an “II” in FIG. 1.

Various configurations of the first pattern areas 121 and the second pattern areas 122 are possible in order to form a pattern 110. At least a portion of the anti-Stokes luminescent substance 200 can be applied both to the first pattern areas 121 and to the second pattern areas 122 with a non-removable, in particular non-detachable, preparation. Likewise, a portion of the anti-Stokes luminescent substance 200 can also be applied both to the first pattern areas 121 and to the second pattern areas 122 with a removable, in particular detachable, preparation. What is decisive, however, is that a relative proportion of the can be removed from the pattern area 120 when the security element 2 is manipulated, based on the total amount of anti-Stokes luminescent substance 200 in the non-manipulated state for a type of the pattern areas 120, here without limitation The generality of the second pattern areas 122 is always greater than for the other type of the pattern areas 120, here always the first pattern areas 121.

This ensures that the surface concentrations, ie the amount of anti-Stokes luminescent substance 200 per area of a pattern area 120, the first pattern areas 121 and the second pattern areas 122, at least in the non-manipulated Merten or in the manipulated state, preferably both in the non-manipulated and manipulated state.

In Fig. 2 is a schematic plan view of the security element 2 of FIG. 1 is provided. The first pattern areas 121 have hatching that runs obliquely from the bottom left to the top right. The second pattern area 122 has hatching that runs obliquely from top left to bottom right.

In the following, it is initially assumed that the first pattern areas 121 have a surface concentration of 100 in any units of the anti-Stokes luminescent substance 200 and that this is completely applied with a non-removable, in particular non-removable, preparation. The second pattern areas 122, of which the pattern 110 in the embodiment according to FIGS. 1 and 2 has only one, have an area concentration of 500 in the arbitrary units in the non-manipulated state. Furthermore, it is assumed that the anti-Stokes luminescent substance 200 applied in the second pattern area 122 is applied with a removable, in particular detachable, preparation, so that it is removed when the security element 2 is manipulated.

A direction of movement 93, along which the security element 2 moves through an illumination area 71 assumed to be stationary, is also indicated in FIG. 2.

In FIG. 3 a, the surface concentration 95 in the arbitrary units is shown in a graph compared to the location along a longitudinal direction 111 of the security element 2 in the non-manipulated state. The area portions hatched under the graph also indicate via their hatching whether and with what proportion of the anti-Stokes luminescent substance 200 is applied with a non-removable, in particular non-detachable, preparation (hatching from bottom left to top right) or with a Removable, in particular releasable, preparation is applied (hatching from top left to bottom right).

In Fig. 3b the security element according to Fig. 3a is shown in the manipulated state.

It can be seen that the portion of the removable anti-Stokes luminescent substance is completely removed (solid line) or at least almost removed (dashed line). The light signal 407, which is generated by means of the excitation device 4, excites the anti-Stokes luminescent substance 200 in the lighting area 71 during the verification in the security element 2. The wavelength of the excitation light of the light signal 407 lies in an excitation wavelength range. The excitation of the anti-Stokes luminescent substance 200 leads to the fact that it emits luminescent light in an anti-Stokes luminescence wavelength range. The wavelengths of the anti-Stokes luminescence wavelength range are shorter than the wavelengths of the excitation wavelength range.

The anti-Stokes luminescent light 9 of the luminescent light 8 emitted by the excited security feature 100 of the security element 2 is detected by the detection device 5. The detection device 5 can, for example, be a spectrometer with a downstream CCD line which allows time-resolved detection for a corresponding part of the electromagnetic spectrum. It is also possible to capture the anti-Stokes luminescent light 9 by means of a photodiode 55 in a time-resolved manner. The detection device 5 derives an output signal 11 from the detected anti-Stokes luminescent light 9 and forwards this to the evaluation device 6. Another time-resolved and intensity-resolved transmitter detector can also be used.

The anti-Stokes luminescent light 9 can be in the visible wavelength range, in the UV wavelength range or in the IR wavelength range. Furthermore, it is possible that in addition to the anti-Stokes luminescence in the security element 2 during the excitation with the light signal 407, a “normal” photoluminescence occurs whose luminescence wavelengths are greater than the wavelengths of the excitation light of the light signal 407.

In order to avoid interference from luminescent light of the “normal” photoluminescence or also from scattered excitation light of the light signal 407, a filter 85 is provided in some embodiments, which blocks wavelengths that are greater than the wavelengths of the anti-Stokes wavelength range. This luminescent light of the “normal” photoluminescence 81 is prevented by means of the filter 85 from reaching the detection device 5. The security element 2 located on the value or security document 3 is thus excited to anti-Stokes luminescence by means of one of the light signal 407, the intensity of which is controlled by a predetermined input signal 27. The predetermined input signal 27 thus defines the intensity of the light signal 407 which changes over time, for example via a modulation device 10.

In particular, after the intensity of the anti-Stokes luminescent light 9 has been detected, an analog-digital conversion can be provided in an A / D converter 118 so that an output signal 11 of the detection device 5 can be provided in digital form, for example as a data stream. The analog / digital conversion can also only take place in the evaluation device 6.

The evaluation device 6 transforms the output signal 11 in a transformation module 13 by means of a characteristic function 12 into a transformed output signal 14. Such a transformation can in particular be an unfolding of the output signal 11 with the characteristic function 12.

The transformed output signal 14 is forwarded to a demodulator module 15 and demodulated there. Here, input signal information 16 of light signal 407 or input signal 27 is taken into account. Such input signal information 16 is, for example, a symbol form of symbols which are used to generate the input signal 27 or the light signal 407. The demodulation can, for example, be carried out using a matched filter which is matched to the symbol shape.

It is then determined in a recognition module 116 whether the detected anti-Stokes luminescent light 9 was emitted by the expected anti-Stokes luminescent substance or not. If, for example, it can be determined that the transformed signal is similar to a signal in which symbols are transmitted, for example if a signal-to-noise ratio is determined above a threshold value, the anti-Stokes luminescent substance is used for the area for which the evaluation is current is made, recognized as real or as expected anti-Stokes luminescent substance. The existence of the correct anti-Stokes luminescent substance 200 can thus be determined. This decision as to whether the correct anti-Stokes luminescent substance was recognized or not is a recognition decision 18 or a component of a recognition decision 18. As will be explained below, there are different ways in which the existence of the correct anti-Stokes luminescent substance can be recognized.

Since the value or security document 3 moves together with the security element 2 relative to the illuminated area 71, it is determined in a chronological sequence for different locations on the security element 2 whether the correct anti-Stokes luminescent substance 200 is present in the security element.

On the basis of these recognition decisions 18, which in simple embodiments only include the existence decisions, it can be determined whether the pattern 110 formed from the first and second pattern areas 121, 122 corresponds to the expected pattern of a non-manipulated security element or the expected pattern of a manipulated security element.

In the non-manipulated state of the security element 2, an anti-Stokes luminescence 9 of the correct anti-Stokes luminescent substance 200 is determined over the entire security element 2. If, on the other hand, the security element 2, which is a postage stamp, for example, has already been detached from a value or security document, here for example another letter, and stuck onto the value or security document 3 in the form of a letter, then the anti Stokes luminescent substance 200 in the area of the second pattern area 122 was removed, so that the existence of the anti-Stokes luminescent substance 200 is recognized during the verification as long as the illuminated area sweeps over a first pattern area 121-1. Then, while the illuminated area 71 sweeps over the second pattern area 122, it is determined that the anti-Stokes luminescent substance 200 is not present. As soon as the illuminated area 71 sweeps over the further first pattern area 121-2, an anti-Stokes luminescence of the correct anti-Stokes luminescent substance 200 is determined again. In this way, a manipulated security element 2 can be reliably distinguished from a non-manipulated security element 2. If the correct anti-Stokes luminescent substance 200 is missing in an area, which is a pattern area 120, the security element 2 has been manipulated. The verification decision 19 can thus be derived from the recognition decisions 18.

In addition, forgeries of the security element 2 can also be recognized, in which the anti-Stokes luminescence 9 is caused by another anti-Stokes luminescent substance caused. Although anti-Stokes luminescence occurs, the transformed output signal 14 cannot then be correctly demodulated.

Via the evaluation device, for example, access barriers, such as a lock, a barrier, etc., or sorting machine 21, in which, for example, letters with manipulated postage stamps are selected, can be controlled. This can take place via an output device 20, which can also output the verification result as a data record or display it visually on a display device.

For example, a triangular pulse followed by a constant component, which is preferably zero, can be used as the symbol form to code the input signal.

It is noted that knowledge of the symbol shape allows demodulation of the transformed output signal and reconstruction of the encoded information to be carried out.

It is important to note that the information encoded with the symbol or symbols to be transmitted does not necessarily have to be determined and evaluated. In some embodiments, it is sufficient to use a knowledge of the symbol shape in order to determine that the symbol transmission by the anti-Stokes luminescent substance used corresponds to the transmission by a “real” anti-Stokes luminescent substance.

For example, the identification decision 18 can then be derived by determining the signal-to-noise ratio in the transformed output signal 14. For example, the existence of the anti-Stokes luminescent substance is determined when a certain threshold value of the signal-to-noise ratio is reached or exceeded.

Another alternative method for demodulation is, for example, the use of an “Integrate and Dump” filter. Here, a discrete input signal is cumulatively added up for a specific number of samples or for a specified time window for each step (“integrate”). After the specified number of samples has elapsed, the sum is reset to zero ("dump") and the cumulative totalizing is started again. The information encoded in the excitation can then be recovered, for example by means of threshold value recognition. This verse drive can usually be used if a symbol shape of the excitation has a simple triangular pulse shape.

Another alternative and preferred method uses a Kalman filter which determines the system response at each point in time of the scanned luminescence signal and then determines the system response despite the noise. A so-called extended Kalman filter is preferably used, i.e. a non-linear Kalman filter. Here it is very important to fully record the above-mentioned measuring chain, since the actual input function of the Kalman filter is the excitation signal of the anti-Stokes luminescent substance. The system response of the system, consisting of the excitation unit, security element and detection device, can only be recorded if the excitation signal is correctly known.

The advantage of the method and the device is that small non-linearities due to the integration and longer acquisition times, especially when using the Kalman filter, hardly influence the evaluation and, in contrast to the prior art, spectral shifts in the frequency range of the output signal are no longer combined lead to major errors in evaluation and verification. Furthermore, the DC component of the output signal does not have to be considered separately. Another advantage is that the phase position no longer necessarily has to be recognized (a so-called phase recovery is not necessary). Furthermore, the maximum possible signal-to-noise ratio is achieved.

In a particularly advantageous embodiment, it is provided in particular that the luminescent effect of the security feature is modeled as a linear time-invariant system (LTI) that is linear for a short time. That is to say, it is primarily assumed that an anti-Stokes luminescence has both the property of linearity with respect to the excitation and is independent of time shifts. This simplifies the transformation equations and thus enables particularly efficient further processing of the output signal.

In particular, it is provided in an advantageous embodiment that when evaluating to derive the recognition decision 18 in the evaluation device, a correlation of the transformed output signal 14 with at least a part of the input signal 27 is carried out, with the anti-Stokes luminescence having Si Security feature (100) is found to be genuine if a correlation function reaches or exceeds a predetermined threshold value at a predetermined point in time or in a predetermined time range. A cross-correlation of the transformed output signal 14 with at least part of the input signal 27 is thus carried out. This part of the input signal can in particular be a symbol shape used in the input signal.

Furthermore, it can also be provided that the threshold value has to be exceeded for several predetermined times or several predetermined time ranges so that the anti-Stokes luminescent substance is found to be genuine and recognized. If, on the other hand, the specified threshold value or if the specified threshold values are not exceeded, the anti-Stokes luminescent substance is found to be incorrect.

The characteristic function can in particular be derived from a reference security feature that is known to be genuine. Therefore, in one embodiment it is provided that the characteristic function is determined by means of a calibration measurement, a reference safety feature having anti-Stokes luminescence being excited and its luminescence as a reference output signal being detected and evaluated. In order to derive the characteristic function, a calibration measurement is carried out which (like the verification process itself) excites the reference security feature by means of a predetermined input signal by means of a light signal from the excitation device, acquires a luminescence emitted by the reference security feature and converts the recorded luminescence comprises a reference output signal by the detection device. The characteristic function is then derived from the reference output signal and the specified input signal.

In particular, a further advantageous embodiment provides for the characteristic function to be the inverse of a transfer function of the reference security feature having anti-Stokes luminescence, the anti-Stokes luminescence effect of the security feature and the reference security feature being understood as a linear time-invariant system .

As a rule, the inverse of the transfer functions cannot be determined analytically. In a further advantageous embodiment it is therefore provided that the Inverse of the transfer function is calculated using numerical methods. This can be done, for example, using the Matlab function “fmincon ()” (for example in Matlab® Version 2016a, a software from The MathWorks, Inc. in Natick, Massachusetts, USA).

In particular when using a Kalman filter, normalization can be carried out during the evaluation. This normalization depends, among other things, on the recorded intensity of the anti-Stokes luminescence. The evaluation of this information can therefore be included in the recognition decision 18. In addition to determining the existence or non-existence of the correct anti-Stokes luminescent substance 200 in the examined scanning area / illuminated area 71 and the associated pattern area 120, the intensity of the detected anti-Stokes luminescence 9 is also evaluated. The intensity assigned to a pattern area 120 in this way is set in relation to the anti-Stokes luminescence intensities determined for other pattern areas 120 in order to be able to derive a pattern 110.

This will be described in more detail below.

A security element 2 with a pattern 110 is shown schematically in FIG. 4a. The pattern 110 comprises a first pattern area 121-1, a second pattern area 122-1, and a further first pattern area 121-2.

Trailing digits of the form "- x" are used to count pattern areas 120 of a type, where x is a natural number. The first sample area 121-1 arranged on the left is thus marked with “-1” and differs from the further first sample area “121-2” with the subsequent designation “-2”. Otherwise, the first pattern areas 121-1, 121-2 are formed identically with regard to the anti-Stokes luminescent substance 200 applied. This means that the area concentration of the anti-Stokes luminescent substance 200 in the first pattern area 121-1 and 121-2 is identical. Furthermore, the type of application is the same, ie the portions that are applied with a non-removable preparation and the portions that are applied with a removable preparation are also identical for both pattern areas 121-1, 121-2. In the example shown, the entire anti-Stokes luminescent substance 200, which is applied in the first pattern area 121, 121-1, 121-2, is applied with a non-removable, in particular non-removable, preparation. The surface concentration is 100 arbitrary units.

The anti-Stokes luminescent substance 200 with a surface concentration of 500 arbitrary units is applied completely to the second pattern area 122, 122-1 with a removable, in particular detachable, preparation. In FIG. 4b, the surface concentration 95 is plotted against an extension of the pattern along an x direction 92.

The first pattern area 121-1 extends from X0 to X1, the second pattern area 122-1 extends from X1 to X2 and the further first pattern area 121-2 extends from X2 to X3.

The x-direction 92 and the corresponding positions X0, X1, X2, X3 are drawn accordingly in FIG. 4a. Hatching under the function graph, which indicates the area concentration 95 of the anti-Stokes luminescent substance 200 compared to the position in the pattern 110, indicate the proportions with non-removable preparation (hatching from top left to bottom right) or with removable preparation (Hatching from bottom left to top right) are applied or incorporated.

A direction of movement 93, along which the security element 2 moves through an illumination area 71 assumed to be stationary, is also indicated in FIG. 4a and, for reasons of illustrating the invention in connection with the further, following figures, is "opposite" to the illustration in FIG. 1 and 2 chosen.

In the example shown in Figures 4a and 4b, the anti-Stokes luminescent substance 200 is in each of the pattern areas 120, i.e. H. in the first pattern areas 121-1, 121-2 and the second pattern area 122-1, each either completely non-removable or completely removable.

4c accordingly shows the surface concentrations 95 of the pattern 110 applied against the X direction 92 of the security element 2 in the manipulated state. The one originally in the second pattern area 122-1 with a removable, for example detachable, preparation applied anti-Stokes luminescent substance 200 is completely or almost completely (shown in dashed lines) removed in the manipulated state.

During the verification, a light signal 407 is used for excitation. This is intensity-modulated. The intensity is modulated according to an input signal 27. This input signal 27, which is shown schematically in FIG. 4d, is divided into individual recurring sections 28, each of the sections 28 representing a symbol 29. A single symbol 29 includes an excitation component 30 and a pause portion 31. In the example shown, these are of the same length in time. The pause portion 31 is preferably selected in such a way that intersymbol interference when the symbols are transmitted via the transmission channel, including the security element 2 and parts of the verification device, is avoided or at least kept low. The excitation component 30 is generally a triangular pulse which comprises a linearly rising component 30A and a linearly falling component 30B, which are of equal length in time and whose rise has an opposite sign.

During the excitation component 30, the amplitude of the input signal 27 increases from 0 to a maximum amplitude 35 and falls back to zero.

Other symbol shapes can also be used for stimulation. Triangular excitation components, however, have proven to be very favorable.

The functional structure of the light signal 407, which is used for excitation, is similar to that of the input signal 27, since the light signal 407 is modulated according to the input signal 27 with regard to its intensity. To simplify the representation, the maximum value of the amplitude (the maximum amplitude 35) of a symbol, which is represented in the input signal 27 or which is modulated on the light signal, is used below as the amplitude of the input signal 27 or amplitude of the light signal 407, which is used to excite the security element, used for a simplified representation. If an excitation takes place with a light signal 407, in which symbols with the same maximum amplitude 35 of the excitation component 30 are encoded via the modulation iteratively successively in time, the amplitude of the light signal 407 is shown as a constant value in the simplified representation the maximum amplitude of the excitation component 30 of the respective symbols corresponds. If an intensity of the light signal 407 is increased, this is synonymous with the fact that a maximum amplitude of the symbols which are encoded in the light signal 407 is increased accordingly.

In Fig. 4e, an intensity of the light signal 407 used for excitation is plotted against time. As mentioned above, the intensity is indicated in each case by the maximum amplitude 35 of the excitation component of the symbols transmitted for this graphic representation. An intensity curve reflecting the symbol shape is not shown for the sake of simplicity. The points in time TXO to TX3 are shown in the graphic, which correspond to the points in time at which the positions XO to X3 correspondingly pass through the illuminated area 71.

In FIG. 4f, the anti-Stokes luminescence intensity 96 detected without adapting the light signal of the excitation is shown greatly simplified for an intact, unmanipulated security element, neglecting transient processes, intensity fluctuations due to the modulation, intersymbol interference or the like. In FIG. 4g, an associated normalization value 97 determined on the basis of the recorded intensities is indicated, which would normalize a received symbol to a unit intensity given the corresponding recorded intensity of the anti-Stokes luminescent light. It is always assumed here that the security element 2 scans areas of the pattern areas 120 of the same size through the illuminated area 71. If an area concentration of anti-Stokes luminescent substance 200 in the illuminated area 71 of the swept pattern area 121 is, for example, a value of 100 in any units, after the luminescence generated has been detected and developed with the characteristic function assigned to the anti-Stokes luminescent substance 200 , and a corresponding demodulation, a normalization value 97 of, for example, 50 in arbitrary units is defined as the value by which the total intensity of the symbol must be divided in order to normalize a received symbol to a normal intensity. If the area concentration then increases, for example because at a later point in time the second pattern area 122 with an area concentration of 500 in any area concentration units anti-Stokes luminescent substance 200 is located in the illuminated area 71, the luminescence generated increases and, above it, an intensity or an intensity Area below the curve that the symbol describes. In order to normalize this area to the unit area, ie to bring the intensity to the normal intensity, a normalization value 97 of 250 in any normalization units is now necessary, for example. It thus shows that the intensity of the received demodulated signal or a normalization value in the evaluation are in each case a measure of the combination of the surface concentration of the anti-Stokes luminescent substance 200 and the excitation intensity of the light signal 407.

This is because an increase in the intensity of the light signal 407 likewise leads to an increase in the intensity of the anti-Stokes luminescent light that is produced. This makes it possible to use the transmitted intensity in order to use the time sequence, taking into account the relative movement of security element 2 and illumination area 71 or light signal 407, pattern areas 120 along spatial direction 91, which is parallel to movement direction 93 of the security element through the illumination area the normalization intensity 97 to identify.

In addition, the evaluation also provides a statement as to whether the correct anti-Stokes luminescent substance 200 is actually present in the corresponding pattern area. If this is not the case, there is no correct symbol transmission, so that it is not possible to determine the normalization value either. Depending on the evaluation method used, the anti-Stokes luminescence intensity can be determined with a finer or coarser time resolution and the existence of the correct, i.e. expected, anti-Stokes luminescent substance and its surface concentration can be determined here with a finer or coarser spatial resolution. This can then also be used to structure the security element 2 in various pattern areas 120 and the pattern 110 formed therefrom, e.g. B. via a comparison with default data or other expert knowledge about correct, intact and manipulated Si cherheitselemente 2 can be identified.

It is also possible for the intensity to rise so sharply as a result of a change in the surface concentration that a measurement range is exceeded in which a linear intensity detection of the detection device 5 is possible. In this case, the detection device 5 is referred to as saturation. In the saturated state, correct determination via the evaluation based on the characteristic function is no longer possible in such a way as to determine whether or not the correct anti-Stokes luminescent substance 200 is present in the corresponding area of the security element. It is therefore advantageous to dynamically adapt the intensity of the light signal 407 by adapting the input signal so that the luminescence intensity achieved also returns to the linear measurement range of the detection device. In order to reliably check pattern areas also with regard to the presence of the correct anti-Stokes luminescent substance 200, it is advantageous if a plurality of symbols is transmitted in the light signal while the illuminated area 71 sweeps over a pattern area 120. A preferred minimum number is 5 symbols.

As soon as the first symbol is transmitted, in which the detection device 5 is saturated by the luminescent light of the anti-Stokes luminescence 9, the intensity of the light signal 407 for the subsequent symbol transmitted can often be reduced by the correct amount in terms of intensity, since a period of time between reaching the upper threshold of the linear measuring range and falling below this threshold again is a rough measure of the maximum intensity of the anti-Stokes luminescence achieved during the excitation. This applies at least if the intersymbol interference is not too great. It should be noted that the excitation, even if the graphic representation does not show this, always fluctuates between zero and the maximum symbol intensity shown.

If the intersymbol interference is extremely strong, then a plurality of transmitted symbols is required for the correct lowering of the excitation intensity. Depending on the intersymbol interference that occurs and the symbol transmission rate used via the light signal 407 and the relative speed used between the light signal 407 and the security element 2, a coordination can be found that enables a reliable and correct evaluation of the individual pattern areas 120 of the security element 2.

In Fig. 4h, 4i and 4j the input signal 27 (Fig. 4h), which is identical to the light signal 407 except for a factor and other units, as well as the greatly simplified anti-Stokes luminescence light intensities 96 for an unmanipulated security element ( 4i) and a manipulated security element (FIG. 4j) are shown schematically for the case in which the maximum amplitude 35 in the input signal 27 is adapted to the expected increase in intensity for the intact, non-manipulated security element in the time range between TX1 and TX2. The input signal is again only shown in a simplified manner using the maximum amplitude of the symbols transmitted. The actual modulation of the input signal 27 and the light signal 407 resulting therefrom are not shown. The maximum amplitude 35 is in this time range between TX1 and TX2 lowered to 1/5 of the original value of the maximum amplitude 35 in the time range between TXO and TX1. In the time range between TX2 and TX3, the maximum amplitude 35 is raised again to the original value.

In the non-manipulated state, the anti-Stokes luminescent light intensity 96 is constant throughout the measurement. In the manipulated state, the anti-Stokes luminescent light intensity 96 falls to 0 when the anti-Stokes luminescent substance is completely removed and is significantly reduced when it is partially removed.

It goes without saying for a person skilled in the art that only exemplary embodiments for patterns and possible surface concentrations are shown by way of example.

List of reference symbols

1 device

2 security element

3 Security Document

4 excitation device

5 detection device

6 Evaluation device

7 T ransport facility

8 luminescent light

9 Anti-Stokes luminescence

10 modulation device

1 1 output signal

12 function

13 T ransformationsmodul

14 output signal

15 demodulator module

16 Input signal information

17 Control device

18 detection decisions

19 Verification Decision

20 Output device

21 sorting machine

27 input signal

28 sections

29 symbol

30 stimulus component

30A increasing proportion

30B declining portion

31 Break component (non-excitation component) 35 Maximum amplitude

55 photodiode

71 Footprint

81 photoluminescence

85 filters Spatial direction

x direction

Direction of movement

Verification direction

Area concentration (function graph of)

Anti-Stokes luminescent light intensity

Security feature

template

Longitudinal direction

Detection module

A / D converter

(optical) deflection unit

Pattern areas

, 121-x first pattern area

, 122-x second pattern area

Scanning device

Anti-Stokes luminescent substance

Light source

Light signal

Claims

1. Method for verifying security elements (2),

wherein a security element (2) comprises a pattern (110) formed from pattern areas (120) as a security feature (100),

wherein the pattern areas (120) at least

one or more first pattern areas (121, 121-x) and

comprise one or more second pattern areas (122, 122-x),

wherein both in the one or more first pattern areas (121, 121-x) and in the one or more second pattern areas (122, 122-x) in a non-manipulated state of the security element (2) one and the same Anti-Stokes luminescent substance (200) is present,

wherein the anti-Stokes luminescent substance (200) when excited with a light signal whose wavelength or wavelengths are in a range of excitation wavelengths, an anti-Stokes luminescence in an anti-Stokes wavelength range shows,

wherein the one or more second pattern areas (122, 122-x) differ from the one or more first pattern areas (121, 121-x) in that a relative proportion of the anti-Stokes luminescent substance (200), the can be removed from the corresponding pattern area (120) during manipulation, is larger for the pattern area or the plurality of second pattern areas (122, 122-x) than for the respective first pattern area (121, 121-x) or the respective plurality of first pattern areas ( 121, 121-x) is

comprehensive the steps:

Generating a light signal (407) which is time-modulated in intensity according to an input signal (27), the wavelength or wavelengths of which are in the excitation wavelength range and irradiating the light signal (407) into a limited lighting area (71);

Providing one of the security elements (2);

Moving the one of the security elements (2) relative to the illuminated area (71) so that the illuminated area over time sweeps over different of the at least two pattern areas (120) of the graphic pattern (110) of the security element (2);

iterative detection of luminescent light in the anti-Stokes wavelength range and conversion into an output signal (11) which shows an intensity of the detected air represents minescent light,

Transforming the output signal (11) by means of at least one characteristic function (12) provided for an expected anti-Stokes luminescent substance (200) by an evaluation device (6) into a transformed output signal (14),

Evaluation of the transformed output signal (14) taking into account at least one input signal information item (16) of the input signal (27) for

Deriving recognition decisions (18) for the anti-Stokes luminescent substance (200) by the evaluation device (6),

Deriving a verification decision based on the recognition decisions (18) and

Output of the verification decision (19) by the evaluation device (6).

2. The method according to claim 1, characterized in that deriving the recognition decisions comprises establishing the existence of the expected anti-Stokes luminescent substance (200) and a luminescence intensity that can be assigned to the expected anti-Stokes luminescent substance, which is a measure of the amount of expected anti-Stokes luminescent substance (200) in the illuminated area.

3. The method according to claim 1 or 2, characterized in that the evaluation comprises creating a detection pattern on the basis of the temporally derived recognition decisions taking into account the movement of the Ausleuchtbe rich (71) relative to the security element (2) and deriving the verification fication decision (19) is based on a comparison with a predetermined authenticity or forgery pattern.

4. The method according to any one of the preceding claims, characterized in that the light signal (407) is temporally modulated so that iteratively symbols (29) are transmitted.

5. The method according to claim 4, characterized in that the iteratively transmitted symbols (29) have the same symbol shape.

6. The method according to claim 3 or 4, characterized in that the symbols (29) each comprise an excitation component (30) and a non-excitation component (31).

7. The method according to claim 5, characterized in that the excitation component (30) consists of a linear increase in intensity and a subsequent linear decrease in intensity, the increases in the increase in intensity and decrease in intensity being equal in terms of amount.

8. The method according to any one of the preceding claims, characterized in that the relative movement of the illumination area (71) and the security element (2) at a speed and the modulation of the light signal (407) taking into account an expansion of the pattern areas (120) parallel to the relative direction of movement (93) are coordinated so that the anti-Stokes luminescent substance (200) is excited during the relative movement of the Ausleuchtbe rich over the respective pattern area with a minimum number of symbols modulated on the light signal, the minimum number being greater than two is.

9. The method according to claim 8, characterized in that the minimum number of symbols (29) is greater than or equal to five.

10. The method according to any one of the preceding claims 4 to 9, characterized

shows that the detection takes place at a frequency which is a factor of 20, preferably a factor of 100 or more, greater than a symbol modulation frequency with which symbols are modulated onto the light signal (407).

11. Device (1) for verifying security elements (2) with a pattern (110) formed from pattern areas (120) as a security feature (100), the pattern areas (120) comprising an anti-Stokes luminescent substance (200), wherein the device (1) comprises:

a control device (17) for generating an input signal (27),

an excitation device (4) for generating a light signal (407) which is time-modulated according to the input signal (27) and whose wavelength or wavelengths lie in the excitation wavelength range, and for irradiating the light signal (407) into a limited illumination area (71),

a scanning device (138) coupled to the control device (17) for moving the one of the security elements (2) relative to the illuminated area (71), see above that the illuminated area (71) over time passes over different of the at least two pattern areas (120) of the graphic pattern (110) of the security element (2);

a detection device (5) for iteratively detecting luminescent light (8) in the anti-Stokes wavelength range and converting it into an output signal (11) which represents an intensity of the detected luminescent light,

and an evaluation device (6) which comprises and is designed to transform the output signal (11) into a transformed output signal (14) by means of at least one provided characteristic function (12) when evaluating the transformed output signal (14) taking into account at least one input signal information (16) of the input signal (27) to derive recognition decisions (18) for the anti-Stokes luminescent substance (200) and to derive a verification decision (19) based on the recognition decisions (18) and

an output device (20) for outputting the verification decision (19) of the evaluation device (6).

12. Security element (2) with a pattern (110) formed from pattern areas (120) as a security feature (100),

wherein the pattern areas (120) at least

comprise a first pattern area (121, 121-x) and a second pattern area (122, 122-x),

wherein the first pattern area (121, 121-x) and the second pattern area (122, 122-x) in a non-manipulated state of the security element (2) have an anti-Stokes luminescent substance (200), which when excited with a light signal (407) with wavelengths in an excitation wavelength range shows a luminescence in an anti-Stokes wavelength range,

wherein the first pattern area (121, 121-x) and the second pattern area (122, 122-x) differ in that a portion of the anti-Stokes luminescent substance (200) which can be removed from the security element (2) when manipulated is larger in the second pattern area (122, 122-x) than in the first pattern area (121, 121-x).

13. The security element (2) according to claim 12, characterized in that the pattern (110) has a plurality of first pattern areas (121-1) that are similar to the first Pattern areas (121-x) and / or a plurality of second pattern areas (122-x) which are similar to the one second pattern area (122-1).

14. Security element (2) according to one of claims 12 or 13, characterized in that the surface concentrations of the anti-Stokes luminescent substance (200) in the first pattern area (121) and in the second pattern area (122) are the same in the non-manipulated state are.

15. Security element (2) according to one of claims 12 to 13, characterized in that the surface concentrations of the anti-Stokes luminescent substance (200) in the first pattern area and in the second pattern area, which are not removable, are the same.

16. Security element (2) according to one of claims 12 to 15, characterized in that the surface concentrations of the anti-Stokes luminescent substance (200) in the first pattern area (121) and in the second pattern area (122) are unequal in the non-manipulated state and the areal concentrations of the anti-Stokes luminescent substance (200) that are removable in the first pattern area

(121) and in the second pattern area (122) are also unequal.

17. The security element (2) according to one of claims 12 to 16, characterized in that the anti-Stokes luminescent substance (200) of the second pattern area (122) cannot be completely removed during manipulation.

18. Security element (2) according to one of claims 13 to 17, characterized in that a detection direction (94) exists with respect to which the first pattern areas (121) and second pattern areas (122) alternate in the pattern and the first and the last pattern area (120) along the detection direction (94) either a first pattern area (121) or a second pattern area

(122) are.

19. The security element (2) according to any one of claims 13 to 17, characterized in that the pattern (110) comprises one or more pattern areas (120) which are different from the first pattern area (121) and the second pattern area (122) , and the anti-Stokes luminescent substance (200).

20. Security element (2) according to one of claims 12 to 19, characterized in that in the non-manipulated state of the security element (2) within the pattern (110) between the pattern areas (120) there are no areas which the anti-Stokes- Do not have luminescent substance (200).