EP2539155B1 - Marking device and method for marking valuable or security documents with high resolution - Google Patents

Description

The invention relates to a method for marking value or security documents and a marking device, which are designed for permanently marking a value or security document with the aid of laser light.

Security documents are those documents and objects that are protected by at least one security feature or security element against corruption and / or unauthorized copying. Security documents that embody a value are also referred to as value documents. Security documents include, for example, identity documents, driver's licenses or motor vehicle papers and documents of value, with value documents, for example banknotes, postage stamps or checks.

At least in some of the security documents or value documents, it is advantageous to be able to mark these permanently, preferably individually. Different methods are known from the prior art with which value and / or security documents can be marked individually. Historically, most value and security documents have been paper-based and, in particular, have been customized by means of printing techniques, modern security documents and value documents are often at least partially made from plastic materials. Modern identity cards and driver's licenses are joined together, for example, as lamination bodies comprising a plurality of plastic layers and optionally one or more paper layers.

For the permanent individual marking of plastics so-called laser marking methods have been developed in the prior art. For this purpose, the plastic layers, which consist for example of polycarbonate, special pigment substances at least in individual layers, which are to be marked later with a laser added. These do not affect transparency in the visible optical range or are not or barely perceptible to a user. If such a layer is irradiated with laser light of sufficient intensity, an increased absorption of the laser light occurs at the pigments. This makes it possible to use energy in the otherwise coupling transparent plastic, which then leads over the amount of energy deposited here to a local color, for example via heating and a partial carbonization of the plastic material. Depending on the amount of energy applied, a degree of blackening of the plastic can be set in a targeted manner. From individual local pixels, patterns, in particular grayscale images, lettering and other characters, can be permanently marked in the value or security document.

From the DE 100 11 486 A1 a card-shaped data carrier is known, consisting of at least one layer in which visually readable information in the form of a change in optical properties due to an irreversibly caused by a laser beam material change are introduced, the absorption capacity of this layer for at least one wavelength due to the laser radiation at least partially is reduced. In this process, original colored or opaque layers are "bleached" in terms of absorption.

From the DE 30 48 733 A1 For example, an identification card and a method for producing such an identification card with information applied are known in the form of patterns, for example letters, numbers and / or images. The identification card has layer areas of different colors arranged one above the other on at least one surface, which are at least partially interrupted by visually recognizable personalization data. It is envisaged that the information is displayed by the action of a controlled laser beam on one or more on a plastic carrier superimposed color layers. As a result of the laser irradiation, the color can be changed locally.

From the DE 696 05 788 T2 For example, there is known a method of producing an article having a colored mark by irradiating the surface of the article with laser light in the form of the mark, the article being comprised of a plastic composition containing at least three color-forming components in at least the area where the mark is applied which lose their color-forming ability under the influence of laser light selected and present in a concentration such that at each wavelength between 400 and 700 nm at least a portion of the amount of incident light is absorbed, one or more colors for the character be selected, the wavelength of the laser light in the sequence set to a value which depends on the selected color and the surface of the object is then irradiated with the laser light.

From the WO 01/28778 A2 is a method for applying colored characters on a data carrier, preferably made of plastic, known by means of a laser system, wherein in at least one surface layer and / or near-surface layer of the data carrier introduced latent pigments, which takes place by energetic excitation, a change in the absorption behavior of the for the character provided areas of the disk by laser irradiation, which is in the IR and / or visible range, energetically excited such that the same pigments color change takes place and that after the color change of the laser-irradiated latent pigments, not excited by laser irradiation latent pigments be energetically excited in such a way by irradiation with light waves in the UV wavelength range, that in the so-irradiated pigments colorlessness is brought about.

From the DE 100 53 264 A1 a method for writing data, in particular personalization data, on and / or in a data carrier by means of electromagnetic radiation is known, wherein the method any data carrier is provided on and / or in which at least one colorant is provided at least locally, and this colorant is irradiated by the electromagnetic radiation of at least one wavelength range, so that there is a change in the color of the colorant by bleaching in the region of the irradiation, wherein the color change can be determined by machine and / or by a human eye. This results in an increased security against counterfeiting and manipulation for the data carrier.

From the DE 199 55 383 A1 a method for applying colored information to an object is known, wherein the article has at least in a near-surface layer at least two different coloring particles that change the color of this layer under the influence of laser radiation, wherein the laser radiation is used with at least two different wavelengths, In order to change the color of this layer, the application of laser radiation to the object in the vector and / or raster method via a Zweikoordinatenstrahlablenkeinrichtung and a focusing device for focusing the laser radiation is applied to the layer of the object. At least one beam guiding means is provided for generating a first laser beam with the wavelength λ ₁ and at least one further laser beam having a wavelength λ ₂ , which is different from the wavelength of the first laser beam, to lead to the layer of the object via the two-coordinate beam deflection device and the focusing device. For the two-coordinate beam deflection device, an arrangement of two mutually perpendicular axes mounted deflecting mirror is proposed. A focusing is done by a fixed plan field optics. Since the light does not pass through the planar field optics on the optical axis, chromatic aberration effects occur in the focusing device. In particular, if differently colored laser light is used for marking, this requires a complex compensation.

From the DE 10 2006 014 367 A1 For example, a data carrier and a method for its production are known. The data carrier comprises a visually or machine recognizable marking in the form of a pattern of letters, numbers or pictures. In the method of manufacture, a data carrier with a data carrier substrate is provided and a marking layer is applied to the data carrier substrate. The marking is introduced into the marking layer by means of short laser pulses.

From the DE 10 2005 001 443 A1 For example, a security marker in a transparent polymer is known. The security mark includes a visually invisible diffraction structure inside a transparent polymer, which is produced by multiphoton absorption using ultrashort pulses of a femtosecond laser. The diffraction structure is generated in the volume of the polymer via refractive index changes. The extents of the refractive index change are in the submicrometer range. In addition, structures can be generated via multiphoton ablations, the extension of which also lies in the submicrometer range. A readout of the diffraction structure is done with low-power lasers and can be done in transmission or reflection.

The US 2010/0040836 A1 describes a system and method for marking transparent plastic with pulsed femtosecond, picosecond or nanosecond lasers.

The US 2005/0001419 A1 shows a method of color laser engraving a document having a surface layer and a plurality of sublayers. The sublayers include different colors and orientations of ink. A laser creates openings in the Surface layer to expose colored ink in one of the sub-layers. The various orientations of the colored ink include circular, linear and overlapping groupings of ink. The sublayers have repeating groupings.

In the marking methods known from the prior art, which are visually perceptible, it is necessary to dope the plastic material to be marked during the manufacturing process, to apply or incorporate paints or pigments, at least if no material removal from the surface of the security document is intended. In such marking methods, too, the pigments to be ablated are generally mixed with pigments or other additives which facilitate laser light absorption. In addition, in the state of the art The technique usually limits an achievable resolution with regard to the marking produced by the fact that the interaction between the laser light and the value or security document is based on thermal effects.

It is an object of the invention to provide an improved method and apparatus for permanently marking value or security documents that eliminate or reduce disadvantages of the prior art.

The object is achieved by a device with the features of claim 1 and a method with the features of claim 7. Advantageous embodiments of the invention will become apparent from the dependent claims.

Basic idea of the invention

The basic idea of the invention is to carry out the marking of the value and / or security document with laser light, which is generated by a short-pulse laser source. This means that the individual laser light pulses used for marking have a pulse duration of less than 100 picoseconds, preferably less than 10 picoseconds. An advantage of using short-pulse laser light is that intensity densities can be achieved with this light, which can also trigger non-linear optical interactions. This makes it possible, for example, to produce markings with a higher resolution, since thermal interaction processes, which are always associated with a dissipation of the heat into surrounding areas and cause a resolution limitation over it, can be avoided. Furthermore, it is also possible to mark materials which are not specially prepared for laser marking, for example via pigment additives or the like. Nonlinear effects are exploited here. This gives a greater material independence in the marking. Likewise, diffractive structures can be marked directly in documents. It should be emphasized that a visual impairment of areas adjacent to the introduced markings is omitted. Focusing of the laser light can be carried out particularly advantageously so that an interaction with material takes place only in focus. Thus, a precise introduction of markings perpendicular to a document surface possible. It is also possible to introduce markings one above the other, ie in different levels of a document. With such markings, patterns can be produced which are perceptible in a lateral view. For example, a height of a focused area is preferably about 50 μm. The low damage is also due to the fact that in non-linear processes, which have a quadratic dependence on the intensity (I ² dependence), an interaction outside of a focus drops very rapidly. Markings applied near the surface may be made tactile, ie be designed for tactile sensing.

definitions

A security element is a structural unit comprising at least one security feature. A security element can be an independent structural unit, which can be connected, for example glued, to a security document, which can also be a value document. It can also be an integral part of a security document. An example of the former is a so-called holopatch (a hologram patch, such as a hologram film portion) adhered to a bill, or a visa stickable to a security document. An example of the latter is a diffractive surface relief embossed in an identity document.

A security feature is a structure which can only be produced or reproduced with increased effort (not in comparison to simple copying) or not at all unauthorized, or makes a forgery or falsification visually and / or mechanically recognizable.

As security documents are merely exemplified called identity cards, passports, ID cards, access control cards, visas, tax stamps, tickets, driver's licenses, motor vehicle papers and documents of value, which include banknotes, checks, postage stamps and credit cards, and any smart cards and adhesive labels (eg for product security). Security documents, which also embody a value, are also referred to as value documents. A sharp distinction between these two terms is often not possible. A A credit card, for example, represents a security document protected by security features and security elements against counterfeiting and adulteration, which does not directly represent a value beyond the pure material value of the card, but makes it possible to dispose of large assets.

A pulsed laser is a laser that, in contrast to a continuous wave or CW laser that continuously emits laser light, emits laser light in temporally limited portions called pulses. As a short pulse laser is understood here a laser that generates light pulses whose pulse duration is less than 100 picoseconds. The literature also speaks in part of ultrashort laser pulses, with no uniform definition for this. Ultrashort pulses are pulses whose pulse duration is less than 10 picoseconds.

An optical fiber is a fiber made of a transparent material, at the interface of which total reflection can cause conduction of light in the interior of the fiber.

A fiber laser is a laser whose active medium in which light-induced emission of electromagnetic radiation occurs is an optical fiber.

A pattern typically consists of a multiplicity of juxtaposed pattern units or pixel dots. The pattern units or pixels of a pattern are associated with each other and arranged laterally in a defined manner, typically in one or two dimensions, and give the overall view of a representation, such as a picture, a symbol, a logo, a lettering (letters, numbers, alphanumeric characters) or a code (eg a barcode). An individualization pattern is a pattern that is used for individualization.

Individualizing is a pattern when it is unique to a person or an object or a group of persons or objects from a largest set of persons or objects. For example, a code individualizing a group of persons within the total population of a country is the city of residence. An individualizing for a person code, for example, the number of the identity card or passport photo. One for a group of bills within the total amount of bills individualizing code is the value. Individualizing for a banknote is the serial number. Non-individualizing is a pattern that is identical for all elements of an entity. For bills this is for example a coat of arms, which is printed on all banknotes.

Preferred embodiments

In particular, a marking device for value or security documents is proposed which comprises at least one laser light source and a light guide device which is coupled to the laser light source so that light of the laser light source can be positioned controlled on a value or security document, wherein the laser light source is a short pulse laser source Laser pulses with a pulse duration of less than 100 picoseconds, preferably less than 10 picoseconds produced. Particularly noteworthy is that the short laser pulses interact via non-linear optical effects with material of the value or security document to be marked. Here, a change in color, for example, a blackening in different shades of gray, of transparent plastic materials is possible. A doping with color pigments, which is necessary in the prior art in order to make the films "laserable", is no longer necessary. Thus, visual impairments by the additives necessary for this no longer necessarily occur. A preferred method for permanently marking a value or security document thus comprises the steps of generating laser light and guiding the laser light by means of a light-guiding device so that laser light emerging from the light-guiding device is positioned on the security or security document and locally marks the security or security document , wherein the laser light is generated in the form of laser light pulses with a pulse duration of less than 100 picoseconds, preferably less than 10 picoseconds.

According to the invention markings are generated in the register in different levels in the document. In one embodiment, at least a part of the markings are arranged one above the other perpendicular to the surface of the security document.

Markers that are marked in different planes parallel to the surface of the value or security document in the value or security document can be used, for example, to display different information for different viewing directions by the markings of the different levels completely or partially in the different viewing directions cover. Furthermore, different layers, from which the value or security document is optionally joined together, can be linked to one another in terms of information technology. Individual layers can thus be exchanged or falsified only with difficulty without changing the overall information provided by the three-dimensionally introduced marking.

Particularly advantageous short laser pulses with pulse durations in the range less than 100 picoseconds, preferably in the range of 100 Fermtosekunden to 10 picoseconds, generate with a fiber laser. Compared with other solid state lasers fiber lasers have the advantage that they can be constructed very compact and have a high electro-optical efficiency. In addition, fiber lasers much more modest in terms of adjustment and handling than most known solid-state lasers.

An advantage of using short laser pulses with pulse durations of less than 100 picoseconds, preferably less than 10 picoseconds, is that a very precise spatial confinement of the interaction zone between the laser light and the material of the asset or security document is achievable when non-linear optical interaction effects can be used to form the label. A preferred embodiment of the method therefore provides that the marking is triggered via a non-linear optical effect in the value or security document.

In one embodiment, it is provided that the light-guiding device comprises a relative to the value and / or security document movably mounted optical fiber, which is coupled to at least one drive means so that the light via a movement of an exit surface of the optical fiber in a positioning plane relative to the value - And / or security document can be positioned laterally on the value or security document. The light of the laser light source is thus guided by means of an optical fiber, and a positioning of the light on the value or security document to be marked takes place by moving the exit surface of the optical fiber relative to the value or security document. Compared to the prior art, there is the advantage that the light used for the marking with a suitable orientation of the positioning plane relative to a surface of the security document, preferably parallel thereto, in each case at the same angle, preferably perpendicular, to the value and / or security document incident and beyond a path length of the traveled light path is equal regardless of the illuminated lateral position on the security and / or security document. This makes it possible to focus the light used more strongly and yet to use an identical focus extension at the marking at all lateral positions of the value or security document. Problems that are known due to a slightly different direction of irradiation in the guide devices of the prior art, can thus be avoided.

In a further embodiment it is provided that the security and / or security document is movably mounted relative to the optical fiber. Construction and use are analogous to that of the moving optical fiber.

In a further embodiment it is provided that both the light guide device comprises a relative to the security and / or security document movably mounted optical fiber as well as the security and / or security document is movable relative to the optical fiber. It is particularly preferred that the security and / or security document is movable along a transport direction and that the optical fiber is movable in a direction orthogonal to the transport direction, parallel to the surface of the security and / or security document to be personalized.

To achieve a high resolution in the marking, a good focus is advantageous. For this purpose, a focusing optics can be used. It is preferred, a focusing optics, if used, to couple with the respective exit surface of the optical fiber. This means that the focusing optics is moved by means of the drive device together with the exit surface of the optical fiber. The advantage is that the light path through the focusing optics is the same in each case, regardless of the position on or in the value or security document that is being marked.

In a preferred method, the position of the focus in the document is varied. This means that the focus position along a normal to a plane surface of the document or a plan idealized surface of the value or security document, if this has a surface relief or other unevenness, at the same lateral position or at different lateral positions on the value or security document is varied. Thus, markings are made in different levels of the value or security document. These can be arranged one above the other or laterally offset, in each case arranged relative to the surface of the preferably card-shaped value or security document.

Different implementations are possible to specifically set a focus position in the value or security document.

In one embodiment, the focusing is done by means of the Kerr effect. In this case, the focal length of the material of the focusing lens changes due to the non-linear interaction of the electromagnetic radiation with the material of the lens. The focal length of the lens is inversely proportional to the intensity of the electromagnetic radiation in a Gaussian radiation profile.

In an embodiment in which the light guide is performed by means of an optical fiber, it is provided that in addition to the movement in the positioning plane, which is usually oriented parallel to a surface of a plane security document, a movement of the exit surface of the optical fiber is possible to vary a light path between the exit surface and a surface of the document. This can be used to vary a focus position within the value or security document. For example, in one embodiment, such a path change may be achieved by having the exit surface, from which the light is guided linearly on the document surface, in addition to the movement in the positioning plane, which is parallel to the surface of the security document Positioning level or the surface of the value or security document is movable.

For example, in other embodiments, where the exit surface is moved together with imaging and / or focusing optics in the positioning plane to position the emergent light laterally on the surface of the asset or security document, a change in the light path may occur in some embodiments, for example be achieved that the exit surface of the optical waveguide in addition relative to elements of the imaging and / or focusing optics, such as a deflection mirror, in the positioning plane is relatively movable. Thus, on the one hand, a positioning laterally on the document via a movement of the exit surface together with the imaging and / or focusing optics is possible and additionally by a relative movement of the exit surface relative to the imaging and / or focusing optics in the positioning plane a change in the focus position perpendicular to Surface of the value or security document possible.

In a further embodiment, the focusing optics consists of a piezoelectric material. By applying tension, the material can be deformed and thus the focal length of the material can be adjusted.

In a preferred embodiment, the laser light source is integrated in the optical fiber. As a result, any coupling losses are reduced in the coupling into the fiber. Thus, a compact and simple construction is possible. Compared with solid-state lasers, for example Ti: sapphire lasers, fiber laser systems do not require expensive cooling and achieve a high electro-optical efficiency. Furthermore, laser light of different wavelengths can be generated by parametric tuning with the same hardware. This is effective with fiber lasers.

In order to enable a faster marking of the value or security document is provided in a development of the invention that the light guide device comprises at least one further movable, preferably even more movable movably mounted optical fibers. This makes it possible, at the same time at several points or at the same time with different wavelengths of light to attach a mark on the security or security document or bring in the value or security document. If different wavelengths of light are used, then each optical fiber can have one to the corresponding wavelength of light be fitted adjusted focusing optics. It should be noted that with pulse durations of more than 10 ps it is still possible to speak of a defined wavelength. At pulse lengths shorter than 10 ps, the spread due to the Heisenberg uncertainty principle is significant. For example, the blur at a pulse of 10 ps is about 0.41 meV, which corresponds to about 0.12 nm at a wavelength of 620 nm (2 eV). At pulse durations of 10 fs, the blur is about 0.41 eV, which means at a wavelength of 620 nm (2 eV) that the bandwidth is at least 125 nm.

In a preferred embodiment of the invention, the exit surface of the at least one optical fiber is positionable relative to the at least one further optical fiber or optionally relative to the plurality of exit surfaces of the plurality of optical fibers in the positioning plane. Particularly preferably, the plurality of optical fibers or their exit surfaces are individually driven in the positioning plane and can be positioned relative to one another. It goes without saying for the person skilled in the art that there are mechanical residual actions since the optical fibers can not penetrate one another and thus can not be arranged at one and the same position at the same time.

In one embodiment of the invention, the number of optical fibers is selected such that upon a relative movement of the entirety of the optical fibers along a spatial direction, the entire value or security document or at least one strip of the security or security document can be marked with a two-dimensional / three-dimensional pattern. In this case, the optical fibers can be arranged rigidly relative to one another along a line or any other arrangement.

In one embodiment, it is provided that an optical modifying element is coupled or integrated with the at least one optical fiber, via which the decoupled light can be modified in terms of its frequency and / or intensity. This is particularly advantageous when the light guide device comprises a plurality of further optical fibers. These then preferably also each have an optical modifying element associated with the fiber.

Since the light energy generated by a laser light source is generally sufficient to mark the document at several points at the same time, in one embodiment it is provided that the light from the one laser light source is directed into the at least one laser light source Optical fiber and the at least one further or optionally a plurality of further optical fibers is coupled. Even with such an embodiment, it is advantageous if the individual optical fibers are each assigned an optical change element. It is understood that embodiments are also advantageous, which comprise a plurality of laser light sources whose light is coupled in each case in one or more of the several further optical waveguides.

If a plurality of optical fibers are present, the focus position within the value or security document along a normal to the surface of the security or value document can be set individually for the latter in one embodiment. This can be targeted markings in different levels or layers, from which the value or security document is joined, are introduced. Preferably, this is controlled possible.

The features of the method according to the invention have the same advantages as the corresponding features of the marking device according to the invention.

Fig. 1

eine schematische Darstellung einer Markierungsvorrichtung für Wert- oder Sicherheitsdokumente;

Fig. 2

eine weitere Ausführungsform einer Markierungsvorrichtung;

Fig. 3

noch eine andere Ausführungsform einer Markierungsvorrichtung;

Fig. 4

eine schematische Darstellung einer Anordnung von Austrittsflächen von Lichtleitfasern relativ zu einem zu markierenden Wert- und/oder Sicherheitsdokument;

Fig. 5a, 5b

eine Abbildungs- und Fokussieroptik zum Variieren in Fokuslänge;

Fig. 6

eine schematische Darstellung eines Strahlprofils im Fokus; und

Fig. 7

eine schematische Darstellung eines Wert- oder Sicherheitsdokuments, bei dem Markierungen in unterschiedliche Ebenen eingebracht sind.

The invention will be explained in more detail with reference to preferred embodiments with reference to a drawing. Hereby show:

Fig. 1

a schematic representation of a marking device for value or security documents;

Fig. 2

another embodiment of a marking device;

Fig. 3

yet another embodiment of a marking device;

Fig. 4

a schematic representation of an arrangement of exit surfaces of optical fibers relative to a value and / or security document to be marked;

Fig. 5a, 5b

an imaging and focusing optics for varying focal length;

Fig. 6

a schematic representation of a beam profile in focus; and

Fig. 7

a schematic representation of a value or security document, are introduced in the markers in different levels.

In Fig. 1 schematically a marking device 1 for permanently marking a value or security document 2 is shown. The value document 2 is arranged on a holder 3. This can be supplied to the value or security document 2 by means of a transport device 4 and / or removed from it. In some embodiments, it is possible that the transport device 4 forms the holder 3. The person skilled in various devices for transporting value or security documents are known. In general, the marking of the value or security document 2 is carried out after this is completed except for the mark still to be attached. However, it is also possible to make the marking before the value or security document 2 is completely finished, for example, before it is separated from a sheet or a strip.

The marking device 1 comprises a laser light source 5. The laser light source 5 is designed to generate laser light 6. The laser light source 5 is a pulsed light source. For example, it may be a solid-state laser, eg a Ti: sapphire laser. In order to mark the value or security document 2, the laser light 6 has to be positioned in a targeted manner on the value or security document 2, ie on its surface 7 or in the interior of the value or security document 2. For this purpose, a light guide device 8 is provided. In the embodiment described here, the light-guiding device 8 comprises an optical fiber 9, into which the laser light 6 is coupled. An exit surface 10 of the optical fiber 9 is moved in a positioning plane 11. The positioning plane 11 is formed parallel to the surface 7 of the value or security document 2 in a preferred embodiment. In order to be able to move or position the exit surface 10 in the positioning plane 11, the optical fiber 9 is coupled to a drive device 12. The drive device 12 comprises in the illustrated embodiment an X-axis actuator 13, a Y-axis actuator 14 and a Z-axis actuator 15. These are connected and aligned so that the X-axis actuator movement of the exit surface 10 of the optical fiber 9 parallel to a X-axis 16, the Y-axis actuator 14 parallel to a Y-axis 17 and the Z-axis actuator 15 parallel to a Z-axis 18 causes. It should be noted that a movement parallel to the Z-axis causes a change of the positioning plane 11. About the drive means 12, it is thus possible, a position of a focal point 19 of the exit surface 10 exiting laser light 6 'along a normal to the surface 7 of the value or security document 2 to position. By contrast, a movement of the exit surface 10 in the positioning plane 11 effects a lateral alignment and positioning of the laser light 6 'emerging from the exit surface 10 or the focal point 19 formed thereof. It should be noted that other embodiments may have and use differently configured light guiding devices

In some embodiments, it is provided that an imaging and / or focusing optics 20 is coupled to the exit surface 10 of the optical fiber 9. This is moved with the exit surface 10 of the optical fiber. In some embodiments, the exit surface 10 of the optical fiber is configured so that the exiting laser light 6 'is focused and no or supplemental focusing optics are necessary. About the introduced at the respective position in the value or security document amount of energy, which can be varied for example via a pulse intensity or a number of introduced at the same position light pulses, the type of marking, for example, a blackening in terms of a gray level, regulated. Via the drive device 12 it is possible to make a marking vectorially (but broken down into individual pixels (marking points)) or in a grid.

A distance 27 of the positioning plane 11 from the surface 7 or the value or security document 2 need not be varied in many applications in the marking. Thus, a positioning device 8 comprising only an X-axis actuator 13 and a Y-axis actuator 14 is sufficient. It is understood by those skilled in the art that for the positioning of the exit surface 10 of the optical fiber 9 in the positioning plane 11, a set of actuators can be used, which cause no movements parallel to the coordinate axes, but in cooperation are able, the exit surface 10th in the positioning plane 11 laterally flat at different locations to position.

It goes without saying for the person skilled in the art that the light exit surface 10 in the positioning plane 11 need not be positionable in all embodiments so that all points on the surface of the document can be illuminated with the exiting laser light 6 '. The laser light only needs to be positionable at those positions on the asset or security document at which markings are to be made. Is only a limited range of value or Security document provided for a mark, as well as an adapted to this area positioning range 26, in which the exit surface 10 of the optical fiber 9 is positioned.

In order to control the light intensity, or even a wavelength of light, in some embodiments, a modifying element is integrated with or coupled to the optical fiber 9. The modification element 21 can be designed, for example, as an electro-optical or acousto-optical modulator or switch. Thus, independently of the pulse energy provided by the laser, the amount of energy supplied locally and, for example, a blackening in gray levels can be controlled individually.

The individual components of the marking device are controlled by a controller 22, so that the marking is carried out automatically. The controller 22 is only supplied with data containing the pattern for the mark, so that the corresponding areas of the value or security document 2 are irradiated with a corresponding laser light intensity to effect the corresponding marking in the value or security document 2.

The embodiment according to Fig. 1 is characterized in that the laser light 6 is generated as a pulsed laser light with short pulse durations of less than 100 ps, preferably less than 10 ps. As a result, an exploitation of non-linear optical effects for introducing the markings on or in the value or security document is possible.

By using the optical fiber 9 for guiding the laser light 6 'on or into the value or security document 2, a path length 27 between the light guiding device 8 and the value or security document 2 can be kept small. This can be selected in the range from contact to a few cm, preferably 0.2 to 10 mm. This makes it possible to form the beam guide strongly divergent and to focus sharply. Both transverse to the beam direction (propagation direction) as well as along the beam direction thus a very narrow focus can be achieved.

With a suitably chosen intensity and suitably selected beam profile, a non-linear interaction is achieved only in a "core region" of the beam of the laser light in focus. As a result, an even closer to the geometric light focusing light focusing is achieved. As a result, an improved resolution during marking can be achieved both laterally (transversely to the direction of irradiation of the laser light 6 'and also longitudinally, that is to say in the direction of propagation of the laser light 6'.) For example, micro writing with a character size in the range of a few micrometers can be realized.

In Fig. 6 a so-called beam profile 61 in focus is shown schematically. A light intensity l is plotted against the position r transversely to the propagation direction (z direction in FIG Fig. 1 ). (r, for example, becomes parallel to the x-axis according to Fig. 1 chosen.) It is assumed here that a beam profile 61 of the laser light 6 '(acc Fig. 1 ) in focus 19 (after Fig. 1 ) has a Gaussian profile. Since nonlinear interactions depend on the square I ² 62 of the intensity I of the laser light, that is to say a so-called I ² dependence, with suitably chosen pulse intensity, the nonlinear interaction takes place only in the core region 63 of the steel profile, in which the square I ² 62 the intensity I of the beam profile 61 exceeds a threshold value 64. As a result, the focal extent of the marking is determined by an extension 65 of the core region 63 and not by the extent 66 of the focus 19 of the laser light 6 ', which corresponds to the extent of the beam profile 61.

Due to the possibility of a very good focus along the propagation direction (z-direction in Fig. 1 ) of the laser light 6 ', it is possible via a variation of the focus position, for example via a variation of the distance 27 between the exit surface 10 of the optical fiber 9 and the security document 2 or its surface 7, high resolution markers in different Mark levels. It is assumed here that the planes are oriented parallel to the surface 7. For example, in the case of card-shaped security documents having an extent of 500 μm to 1000 μm perpendicular to the surface 7, it is possible to mark a plurality of separate markings 71 ', 71 "in the register along a surface normal 72 to the surface 7 For example, the markings 71 in the different planes 73-79, but laterally offset relative to the surface 7 of the document or document 2, may be arranged in the same, as in FIG Fig. 7 is shown schematically. The vertically one above the other arranged separately formed markings 71 ', 71 "can be marked by the same surface 7 and arranged for example above the opaque plane 77.

In addition to a marking by causing discoloration in the value or security document, other material changes can be brought about, for example, causes a scattering or diffraction of light in the ultraviolet and / or visible and / or infrared wavelength range.

In Fig. 2 a further embodiment of a marking device 1 is shown schematically. Technically equivalent features are provided with identical reference numerals. The illustrated embodiment differs from that according to Fig. 1 in that the light-guiding device 8 in this embodiment comprises two optical fibers 9, 9 '. These are correspondingly respectively coupled to a drive device 8 or 8 ', which analogously to the drive device 8 according to Fig. 1 are formed. This embodiment offers the advantage that the value or security document 2 can be marked simultaneously or quasi simultaneously at several locations.

The laser light source 5 is shown schematically in this embodiment as a fiber laser 23 with a seed laser 24 and an amplifier ring 25. It will be understood by those skilled in the art that another laser light source may be used with this embodiment. Likewise, a fiber laser 23 as a laser light source 5 in the embodiment according to Fig. 1 be used.

The emerging from the laser light source 5 light 6 is either a beam splitter (not shown) divided and coupled into the optical fiber 9, 9 'simultaneously or alternately coupled via an electro-optical or electro-acoustic switch in the optical fibers 9, 9'. Since the mechanical movement speed of the exit surfaces 10, 10 'via the drive means 8, 8' are usually limited, can at a suitable selected repetition rate of the laser light 6, 6 'even at maximum movement speed of the exit surfaces 10, 10' is a mark of the value or Security document 2 take place, even if every second laser pulse in the other optical fiber 9, 9 'is coupled. In this case, marking is still considered to be simultaneous or quasi-simultaneous.

In Fig. 3 a further embodiment of a marking device 1 is shown schematically. In this embodiment, two laser light sources 5, 5 'are provided. This makes it possible in a simple manner, at different locations with different repetition rates, wavelengths, etc. to introduce markers on or in the value or security document 2.

In Fig. 4 schematically the exit surfaces 10 of another embodiment of a marking device are shown schematically, in which a plurality of optical fibers 9 are coupled to each other via a drive means together relative to the value or security document 2 movable. In such an embodiment, large-area markings can be accomplished in a short time. Also in this embodiment, each of the optical fiber 9 is preferably coupled to a modifying element (not shown) so that the respective coupled-in laser light intensity and / or laser frequency can be controlled via each optical fiber 9. Compared with the use of solid-state lasers, such as, for example, Ti: sapphire lasers, a fiber laser system can be used to achieve higher electro-optical efficiencies. Thus, the required energy can be significantly reduced. The entire structure can be made much more compact, so that fitting into a production line or plant is much easier. In addition, as fiber laser systems require less maintenance and installation effort, laser marking systems can also be deployed remotely.

In Fig. 5a and 5b an embodiment is shown in which a focus positioning, ie a positioning of the focal point parallel to the Z-axis, analogous to the geometry of Fig. 1 is described. The embodiment comprises an imaging and focusing optics 20, which comprises a focusing lens 31 and a deflection mirror 32. In addition, a focusing actuator 33 is provided. About this, a relative movement between the deflecting mirror 32 and the exit surface 10 of the optical fiber 9 can be effected. This changes the focus position along the Z-axis. Overall, the imaging and focusing device 20 will be moved together with the exit surface 10 of the optical fiber in the positioning plane 11, which coincides with the XY plane, to laterally position the laser light 6 'on the value or security document. In addition, a movement of the light exit surface 10 in the positioning plane 11 is effected via the Fokussieraktor 33, but only the distance changed to the deflecting mirror 32 and this the focus position perpendicular to the positioning plane.

LIST OF REFERENCE NUMBERS

1

marking

2

Value or security document

3

bracket

4

transport device

5

Laser light source

6, 6 '

laser light

7

surface

8, 8 '

Lighting device

9, 9 '

optical fiber

10, 10 '

exit area

11

positioning level

12, 12 '

driving means

13, 13 '

X-Achsenaktor

14, 14 '

Y Achsenaktor

15, 15 '

Z-Achsenaktor

16

X axis

17

Y-axis

18

Z-axis

19

focus point

20

Imaging and / or focusing optics

21

changing element

22

control

23

fiber laser

24

Seed laser

25

amplifier ring

26

positioning

27

distance

31

lens

32

deflecting

33

Fokussieraktor

61

beam profile

62

Square of intensity (I ² )

63

core area

64

threshold

65

Extension of the core area

66

Extent of focus

71

marks

72

surface normal

73-79

levels

Claims (15)

1. Marking device (1) for valuable or security documents, comprising at least
   one laser light source (5),
   one light guiding device, which is coupled to the laser light source, such that laser light (6) from the laser light source can be positioned in a controlled manner on a valuable or security document (2),
   the laser light source (5) is a short-pulse laser source, which generates the laser pulses with a pulse duration of less than 100 ps, characterized in that a focus position perpendicular to the surface (7) of the valuable or security document (2) is variable in the valuable or security document (2), in order to produce in the valuable or security document (2) markings (71) in the register in different planes (72-78).
2. Marking device (1) according to claim 1, characterized in that the laser light source (5) comprises a fibre laser (23).
3. Marking device (1) according to claim 1 or 2, characterized in that the light guiding device (8) comprises an optical fibre (9) mounted movably relative to the valuable or security document (2), said optical fibre being coupled to at least one drive unit (12) in such a way that the laser light (6') can be positioned by means of a movement of an exit surface (10) of the optical fibre (9) in a positioning plane (11) laterally on the valuable or security document (2).
4. Marking device (1) according to claim 3, characterized in that the exit surface (10) of the at least one optical fibre (9) can be moved relative to the surface (17) of the valuable or security document (2) in such a way that a focus position (19) of the laser light (6') is variable in the interior of the valuable or security document (2).
5. Marking device (1) according to any one of claims 1 to 3, characterized in that the laser light (6) has a Gauss-shaped beam profile and a focusing lens which causes the focusing by means of the Kerr effect, wherein the focal width of the material of the focusing lenses changes due to the non-linear reciprocal effect of the electromagnetic radiation with the material of the lenses inversely proportional to the intensity of the electromagnetic radiation.
6. Marking device (1) according to any one of claims 1 to 5, characterized in that the focus position perpendicular to the surface (7) of the valuable or security document (2) is variable in the valuable or security document (2), in order to mark at least two markings (71), formed separately from one another, perpendicular to the surface (7) of the valuable or security document (2) above one another through the same surface (7) into the valuable or security document (2).
7. Method for the permanent marking of a valuable or security document (2) comprising the steps of:

   generating a laser light (6) and

   guiding the laser light (6) by means of a light guiding device (8), such that laser light (6') emerging from the light guiding device is positioned on the value or security document, and

   the valuable or security document (2) is marked locally, and

   laser light (6) is generated in the form of laser light pulses with a pulse duration of less than 100 ps,

   characterized in that

   a focus position (19) of the laser light (6') is varied in the interior of the valuable or security document (2), in order to produce markings (71) in the valuable or security document (2) in the register in different planes (72-78).
8. Method according to claim 7, characterized in that the laser light (6) is guided by means of an optical fibre (9) and a positioning of the laser light (6') on the valuable or security document (2) which is to be marked takes place by way of a movement of an exit surface (10) of the optical fibre (9) relative to the valuable or security document (2).
9. Method according to claim 7 or 8, characterized in that the laser light (6) is generated by means of a fibre laser (23).
10. Method according to any one of claims 7 to 9, characterized in that the markings (71) formed in the register in different planes (71) are marked by way of a colour change in the valuable or security document.
11. Method according to any one of claims 7 to 10, characterized in that the marking (71) is actuated by means of a non-linear optical effect in the valuable or security document (2).
12. Method according to any one of claims 7 to 11, characterized in that at least two markings (71) formed separately from one another are marked perpendicular to the surface (7) of the valuable or security documents (2) above one another through the same surface (7) into the valuable or security document (2).
13. Method according to any one of claims 7 to 12, characterized in that markings (71) are introduced as diffracted and/or scattered structures into the interior of the valuable or security document (2).
14. Method according to claim 13, characterized in that, by means of the laser lights (6), a local modification of the refractive index of a material of the valuable or security document (2) is caused, in order to introduce the diffracted and/or scattered structure.
15. Method according to any one of claims 7 to 14, characterized in that the laser light (6) is generated with a Gauss-shaped radiation profile and a focusing lens causes the focusing by means of the Kerr effect, wherein, due to the non-linear reciprocal effect of the electromagnetic radiation with the material of the lenses, the focal width of the material of the focusing lenses changes inversely proportionally to the intensity of the electromagnetic radiation.

Images