Method and device for introducing a laser-etched security feature

Abstract

Device (100) for introducing a lasered security feature into a blank (200) of an identification, value or security document comprising a flat surface (202), comprising: - a holder (124) for receiving or fixing the position of the blank (200), - a laser source (102) for emitting a laser beam (104), - a lens arrangement (106) comprising at least one electromotively displaceable lens (108) and configured to shape the laser beam (104) emitted by the laser source (102), - a mirror arrangement (112) comprising at least one electromotively adjustable mirror (114) and configured to deflect the laser beam (104) emerging from the lens arrangement (106), - a further lens arrangement (118) for deflecting the laser beam (104) deflected by the adjustable mirror (114) such that the diffracted laser beam (104) impinges on the blank (200) substantially perpendicular to its surface (202), and - a control device (126) for controlling the displaceable lens (108) of the lens arrangement (106) and the adjustable mirror (114) of the mirror arrangement (112), wherein the control device (126) is arranged: a) to record and / or process reference values ​​(122) in the form of three-dimensional topographic data, b) to cause the mirror arrangement (112) to scan the blank (200) with the laser beam (104) in an area provided for the security feature and thereby to introduce the security feature by means of the laser beam (104), and c) adjusting the laser beam (104) in terms of its focal length or its diameter based on the reference values ​​as a function of its point of impact on the flat surface (202) while maintaining the distance between the surface (202) of the blank (200) and the further lens arrangement (118), the focus of the laser beam (104) then following a surface of the reference values ​​in the Z direction.

Description

[0001] The invention relates to a device and a method for introducing a laser-engraved security feature into a blank of an identification, value or security document having a planar surface. The invention also relates to a security feature and an identification, value or security document having such a feature.

[0002] Identification, valuables, or security documents serve to verify the identity of a person or thing or a claim, for example, to payment of money or to the release of a product or provision of a service. To do this, it must be ensured that the document cannot be imitated, forged, or falsified, or can only be done with considerable effort. The document therefore often contains security features that are extremely difficult or even practically impossible to imitate. For example, the document, like banknotes, is made of a material that is not readily available. Additionally or alternatively, security features can be formed by special inks, for example luminescent or optically variable inks, optical elements such as tilting images, kinegrams, lens or prism arrays, guilloches, mottled fibers, security threads, and others.Furthermore, it is often necessary that the identification, valuables or security documents are easy to produce and that they can be read by visually impaired people.

[0003] The publications DE 10 2012 219 249 A1 and US 2018 / 0 243 872 A1 describe devices for laser personalization of security elements. These devices have a laser and a focus adjustment device for varying the focal length. A flat-field optics system is also present. DE 10 2013 000 152 A1 describes a method for producing a security element for security papers, valuable documents, and other data carriers, which also uses a laser with a focus shifter.

[0004] Although many security features exist, many counterfeits of identification, valuables or security documents are still successful.

[0005] It is therefore the object of the present invention to provide a device, a method, a security feature and an identification, value and security document which have increased security against forgery.

[0006] This object is achieved by a device having the features of claim 1, by a method having the features of claim 9, by a security feature having the features of claim 14 and by an identification, value or security document having the features of claim 15. Advantageous embodiments with expedient further developments of the invention are specified in the dependent claims.

[0007] The device according to the invention comprises a holder for receiving or fixing the position of the blank. It further comprises a laser source for emitting a laser beam. A lens arrangement is also provided, which comprises at least one electromotively displaceable lens and is thus configured to shape the laser beam emitted by the laser source. A mirror arrangement is provided, which comprises at least one electromotively adjustable mirror and is thus configured to deflect the laser beam emerging from the lens arrangement. A further lens arrangement is provided, which serves to diffract or focus the laser beam deflected by the adjustable mirror, such that the diffracted or focused laser beam strikes the blank substantially perpendicular to its surface.The device comprises a control device for controlling the movable lens of the lens arrangement, preferably a combination of a convex and a concave lens, respectively, or vice versa, and the adjustable mirror of the mirror arrangement, wherein the control device is configured to:. a) Detect and / or process reference values in the form of three-dimensional topography data, b) Cause the mirror arrangement to scan the workpiece in an area provided for the security feature with the laser beam and introduce the security feature by means of the laser beam, and c) Adjust the laser beam with respect to its focal length or with respect to its diameter depending on its point of incidence on the flat surface based on the reference values, while maintaining the distance between the surface of the workpiece and the further lens arrangement.

[0008] In this way, the already known laser-based marking processes can be enhanced with another parameter: the beam diameter that impinges on the blank. This also involves a shift in the focal point based on given reference values. The lens arrangement is used as a type of defocusing unit ("focus shifter") to achieve variable beam expansion and thus variable modulation of the laser beam, depending on reference values ​​that are provided, for example, by the grayscale itself, by a grayscale image, by a logo, or by another type of three-dimensional structure. The degree of defocusing or the degree of beam expansion is a measure of the line width introduced into the workpiece; or spot width, if the laser is a pulsed laser.Alternatively or additionally, the defocusing unit can be used to generate at least one variable beam divergence, as a result of which the object-side focus distance varies.

[0009] It has proven advantageous if the lens arrangement comprises a galvanometric motor for displacing the at least one displaceable lens, since this is characterized by its low inertia and thus by rapid adjustability.

[0010] In order to ensure that the laser beam hits the flat surface of the blank to be marked as perpendicular as possible, it has proven advantageous if the further lens arrangement comprises a plane field lens.

[0011] An equally reliable vertical alignment allows the design of another lens arrangement in the form of a telecentric F-Theta lens.

[0012] It has proven advantageous if the at least one adjustable mirror of the mirror arrangement is also adjustable by means of a galvanometric motor. This motor, too, is very responsive, allowing for fast, reliable, and precise deflection of the laser beam. The mirror arrangement can, for example, also comprise two different mirrors, with a first deflection mirror providing deflection in the X direction and a second adjustable mirror providing deflection in the Y direction. The adjustment of the laser beam in the Z direction, i.e., the adjustment of the actual focus of the laser beam in relation to the blank, is achieved by the lens arrangement with its movable lens.

[0013] Processing and counterfeit security are increased if an optical detection device is present to optically detect information already present on the blank, and if the control device is configured to use the optically detected information in the form of reference values ​​to adjust the laser beam. The blank can therefore already be provided with personalized information, such as a photograph, which then results in a corresponding data set in the form of reference values ​​to allow X / Y / Z mapping of the laser beam.

[0014] Preferably, this information is personal information, although it is useful if the extracted information concerns personal data of the (future) holder of the identification, valuables, or security document. Alternatively, the information extracted from the blank can also concern document-specific data of the identification, valuables, or security document to be created.

[0015] The advantages and advantageous effects explained in connection with the device according to the invention apply to the same extent to the method according to the invention, in particular because it is carried out with the device according to the invention.

[0016] The method according to the invention comprises in particular the following steps: - Providing or recording reference values ​​in the form of three-dimensional topography data and - Scanning the blank with the laser beam in an area intended for the security feature, wherein the laser beam is modulated in order to introduce the security feature using the reference values ​​with regard to the focal length or with regard to the diameter, while maintaining the distance between the further lens arrangement and the surface of the blank.

[0017] Here, too, the "defocusing unit" in the form of a lens arrangement with its adjustable lens is used to implement beam modulation, particularly with regard to the Z value. This results in a different Z characteristic for focusing the laser beam depending on the X and Y coordinates, i.e., depending on the point of impact of the laser beam on the flat surface of the blank. In this way, wider or narrower laser beams will impinge on the surface of the blank, depending on the previously stored reference values. The defocusing option allows for the implementation of another laser-applied security feature.

[0018] It is advantageous if a focal length of the laser beam specified by the reference values ​​is set for each point on the surface of the blank.

[0019] In order to further increase the security against forgery, it has proven advantageous if the reference values ​​are taken from further information contained on the identification, valuables or security document.

[0020] Preferably, this information is personal information, although it is useful if the extracted information concerns personal data of the (future) holder of the identification, valuables, or security document. Alternatively, the information extracted from the blank can also concern document-specific data of the identification, valuables, or security document to be created.

[0021] The advantages and advantageous effects explained in connection with the method according to the invention apply equally to a security feature according to the invention produced according to this method, as well as to an identification, value or security document according to the invention which is equipped with such a feature.

[0022] Examples of identification, valuables or security documents include a passport, identity card, driving license or other ID card or access control card, vehicle registration document, vehicle registration certificate, visa, check, other means of payment, in particular a banknote, check, bank, credit or cash payment card, customer card, health card, chip card, company ID card, proof of authorization, membership card or other ID document.

[0023] The ID, valuables, or security document is preferably in ID 1, ID 2, ID 3, or some other format, for example, in booklet form, similar to a passport-like item. The ID, valuables, or security product is generally a laminate of multiple document layers that are precisely bonded together under heat and increased pressure. These products should meet standardized requirements, for example, ISO 10373, ISO / IEC 7810, and ISO 14443.

[0024] Preferably, the product layers consist of a carrier material that is suitable for lamination. However, the identification, value or security document can preferably be formed from a polymer selected from a group comprising polycarbonate (PC), in particular bisphenol A polycarbonate or a polycarbonate formed with a geminal disubstituted bis-(hydroxyphenyl)-cycloalkane, polyethylene terephthalate (PET), derivatives thereof, such as glycol-modified PET (PETG), polyethylene naphthalate (PEN), polyvinyl chloride (PVC), polyvinyl butyral (PVB), polymethyl methacrylate (PMMA), polyimide (PI), polyvinyl alcohol (PVA), polystyrene (PS), polyvinylphenol (PVP), polypropylene (PP), polyethylene (PE), thermoplastic elastomers (TPE), in particular thermoplastic polyurethane (TPU), acrylonitrile-butadiene-styrene copolymer (ABS) and derivatives thereof, and / or paper and / or cardboard and / or glass and / or metal and / or ceramic.Furthermore, the product can also be made from several of these materials. It is preferably made of PC or PC / TPU / PC. The polymers can be either filled or unfilled. In the latter case, they are preferably transparent or translucent. If the polymers are filled, they are opaque. The above information refers both to films to be bonded together and to liquid formulations that are applied to a precursor, such as a protective or topcoat. The product is preferably made from three to twelve, preferably four to ten, films. The films can also carry printing layers. A laminate formed in this way can then be coated on one or both sides with the protective or topcoat or with a film. The film can, in particular, be a scratch-resistant film. Overlay layers formed in this way protect a security feature arranged underneath and / or impart the required abrasion resistance to the document.

[0025] The identification, valuables, or security document preferably has a PE carrier onto which the photopolymer film exposed with the hologram is applied. The photopolymer can, for example, be formed from a one-component monomer selected from benzoyl ether, acetophenone, benzoyl oxime, and acylphosphine. The photopolymer can also, for example, be based on a two-component system whose components are selected from benzophenone, xanthone, and quinone.

[0026] Further features, properties and advantages of the present invention will be described in more detail below on the basis of exemplary embodiments with reference to the attached figures. All features described hitherto and below are advantageous both individually and in any combination with one another. The exemplary embodiments described below are merely examples, which, however, do not limit the subject matter of the invention. In this regard: Fig. 1 a schematic illustration of the device for introducing a laser-engraved security feature into a blank of an identification, value or security document having a planar surface, Fig. 2 a schematically indicated beam expansion or defocusing of the laser, which is based on the reference values in the form of a reference image, both for a pulsed laser operation and for a laser operating in a continuous line, Fig. 3 one of the Fig. 2 corresponding representation of the beam expansion or defocusing of the laser, which is based on the reference values ​​in the form of gray levels, and Fig. 4 one of the Fig. 2 corresponding representation of the beam expansion or defocusing of the laser, which is based on the reference values ​​in the form of three-dimensional topography data.

[0027] In Fig. 1 shows a device 100 for incorporating a lasered security feature into a blank 200 of an identification, valuables, or security document comprising a flat surface 202. The device comprises a holder 124 for receiving the blank 200 or fixing it in position. The device also comprises a laser source 102 for emitting a laser beam 104. Furthermore, a lens arrangement 106 is provided, which in this case acts as a defocusing unit and comprises at least one electromotively displaceable lens 108. It is configured to shape the laser beam 104 emitted by the laser source 102. On the exit side, a mirror arrangement 112 is provided, which comprises at least one electromotively adjustable mirror and is thus configured to deflect the laser beam 104 emerging from the lens arrangement 106.In the present case, the mirror arrangement 112 also includes a plurality of adjustable mirrors 114, one of which is configured as a deflection mirror in the X direction and the other as a deflection mirror in the Y direction. Furthermore, a further lens arrangement 118 is provided for diffracting the laser beam 104 deflected by the adjustable mirror 114 such that the diffracted or deflected laser beam 104 impinges on the blank 200 substantially perpendicular to its surface 202. In the present case, the further lens arrangement 118 is formed by a flat-field lens, in particular by an F-theta lens 120.

[0028] The adjustment of the lens arrangement 106, in particular its movable lens 108, is realized in this case by a galvanometric motor 110. The rotation of the at least one adjustable mirror 114 of the mirror arrangement 112 is also realized by a galvanometric motor 116. The F-theta lens 120 is stationary relative to the blank 200.

[0029] A control device 126 is also provided for controlling the movable lens 108 of the lens arrangement 106 and the adjustable mirror 114 of the mirror arrangement 112. This control device 126 is configured to detect and / or process reference values ​​122. It is also configured to cause the mirror arrangement 112 to scan the blank 200 with the laser beam 104 in an area provided for the security feature, thereby incorporating the security feature using the laser beam 104. It also causes the laser beam 104 to be adjusted in terms of its focal length or diameter based on the reference values, depending on its point of impact on the flat surface 202, while maintaining the distance between the surface 202 of the blank 200 and the further lens arrangement 118, in particular the F-Theta lens 120.In this way, the focus of the laser beam “wanders” along the Z values ​​of the reference values ​​122, resulting in a different beam expansion or a different beam diameter on the flat surface 202 of the laser beam, and allowing an individualized lasered security feature to be introduced into the blank 200.

[0030] For additional customization, an optionally shown optical detection device 128 is also provided to optically detect information already present on the blank 200, wherein the control device 126 is also configured to use the optically detected information in the form of reference values ​​122 to adjust the laser beam 104.

[0031] During processing of the blank 200, a focal length (Z) of the laser beam 104, predetermined by the reference values, is thus specified for each point (X, Y) on the surface 202 of the blank 200. The reference values ​​are extracted from further information contained on the identification, valuables, or security document with the aid of the optical detection device 128. The extracted information can, for example, be personal data of the (future) owner of the identification, valuables, or security document. The information extracted from the blank 200 can alternatively or additionally also be document-specific information.

[0032] In Fig. Figure 2 shows, purely by way of example, the beam expansion or defocusing of a laser beam 104, which is based on the reference values ​​122 in the form of a reference image. The stronger the gray value or the color, the greater the characteristic in the Z direction, i.e., the change in the focal length of the laser beam. This results in larger beam diameters, which introduce the security feature on the flat surface 202 at a given distance from the F-theta lens 120. The laser can be a pulsed laser, with the use of a picosecond or femtosecond laser being advantageous because these cause a low heat input into the material of the blank 200. In the illustration shown, the use of a pulsed laser is reflected in individual circles, which can also overlap and which have a different diameter depending on the Z value of the reference values ​​122.If a continuous wave laser is used, a line is produced, which is also illustrated and whose line width varies depending on the reference values ​​122.

[0033] In Fig. Figure 3 illustrates the beam expansion as a function of existing gray levels, with a darker gray tone resulting in a greater focal length of the laser beam 104 than a lighter one. Thus, each gray tone is assigned its own focal length, which also allows the different beam diameters at the point of impact on the workpiece to be recognized as a security feature in the blank 200.

[0034] Finally, Fig.4 also also illustrates that three-dimensional topography data can also be used as reference values 122, in which case the focus of the laser beam 104 follows the surface of the reference values in the Z direction. Using these three-dimensional topography data as reference values 122 also enables more complex security features to be realized. It is also possible to provide a different linkage, which does not necessarily have to be proportional. For this purpose, for example, a non-linear linkage in the sense of a gamma gradation or an inversion is considered.

[0035] As a result, the present invention is thus characterized by an increased forgery security of the security features and opens up new processing variants. An identity document, value document or security document produced with such a security feature is also more forgery-proof.

[0036] It should also be noted that the energy of the applied laser pulses does not necessarily have to be constant. It may be the case that the desired material interaction fails to occur with large incident beam diameters because the quotient of "energy per area" (= fluence), or the irradiance "power per area," decreases with the square of the diameter of the incident beam and may no longer be sufficient (threshold fluence). For Gaussian beams, the diameter of the interaction can therefore decrease with increasing beam diameter, contrary to expectations. Therefore, in a further variant of the described method, it is possible to implement active tracking of the pulse energy in order to ensure that the energetic interaction between the material and the incident laser beam remains largely constant. This implementation can take the form of parameterizable fluence compensation.

[0037] It is possible to dispense with an f-theta lens and create the flat field by deflecting the pre-focused beam. In this case, the inverse function of the normally spherical focal area is interpolated onto the focus shifter. In this case, the object types mentioned can be understood as an offset to the spherical correction matrix, with otherwise identical functionality. LIST OF REFERENCE SYMBOLS 100 Device for inserting a lasered security feature 102 Laser source 104 laser beam 106 lens arrangement 108 movable lens 110 Motor (lens arrangement) 112 Mirror arrangement 114 adjustable mirror 116 Motor (mirror arrangement) 118 additional lens arrangements 120 F-Theta lens / F-Theta lens 122 reference values 124 bracket 126 Control device 128 optical detection device (e.g. camera) 200 Blank ID, valuables or security document 202 Surface

Claims

[1] Device (100) for introducing a lasered security feature into a blank (200) of an identification, value or security document comprising a flat surface (202), comprising: - a holder (124) for receiving or fixing the position of the blank (200), - a laser source (102) for emitting a laser beam (104), - a lens arrangement (106) comprising at least one electromotively displaceable lens (108) and configured to shape the laser beam (104) emitted by the laser source (102), - a mirror arrangement (112) comprising at least one electromotively adjustable mirror (114) and configured to deflect the laser beam (104) emerging from the lens arrangement (106), - a further lens arrangement (118) for deflecting the laser beam (104) deflected by the adjustable mirror (114) such that the diffracted laser beam (104) impinges on the blank (200) substantially perpendicular to its surface (202), and - a control device (126) for controlling the displaceable lens (108) of the lens arrangement (106) and the adjustable mirror (114) of the mirror arrangement (112), wherein the control device (126) is arranged: (a) to record and / or process reference values (122) in the form of three-dimensional topographic data, b) to cause the mirror arrangement (112) to scan the blank (200) with the laser beam (104) in an area provided for the security feature and thereby to introduce the security feature by means of the laser beam (104), and c) adjusting the laser beam (104) as a function of its point of impact on the flat surface (202) with regard to its focal length or with regard to its diameter using the reference values while maintaining the distance between the surface (202) of the blank (200) and the further lens arrangement (118), the focus of the laser beam (104) then following a surface of the reference values in the Z direction. [2] Device (100) according to claim 1, characterized by that the lens arrangement (106) comprises a galvanometric motor (110) for displacing the at least one displaceable lens (108). [3] Device (100) according to claim 1 or 2, characterized by that the further lens arrangement (118) comprises a plano-field lens. [4] Device (100) according to one of claims 1 to 3, characterized by that the further lens arrangement (118) is a telecentric F-theta lens (120). [5] Device (100) according to one of claims 1 to 4, characterized by that the at least one adjustable mirror (114) is adjustable with a galvanometric motor (116). [6] Device (100) according to one of claims 1 to 5, characterized by that an optical detection device (128) is provided in order to optically detect information present on the blank (200), and that the control device (126) is arranged to use the optically detected information in the form of reference values (122) for adjusting the laser beam (104). [7] Device (100) according to claim 6, characterized by that the information extracted concerns personal data of a holder of the identification, valuables or security document. [8] Device (100) according to claim 6, characterized by that the information extracted concerns document-specific data of the identification, valuables or security document to be created. [9] Method for introducing a lasered security feature into a blank (200) of an identification, value or security document comprising a flat surface (202) with a device (100) according to one of claims 1 to 8, comprising the steps: - Providing or collecting reference values in the form of three-dimensional topography data, and - scanning the blank (200) with the laser beam (104) in an area provided for the security feature, wherein the laser beam (104) is modulated in order to introduce the security feature on the basis of the reference values with regard to the focal length or with regard to the diameter while maintaining the distance between the further lens arrangement (118) and the surface (202) of the blank (200), wherein the focus of the laser beam (104) then follows a surface of the reference values in the Z direction. [10] Method according to claim 9, characterized bythat for each point (X, Y) on the surface (202) of the blank (200) a focal length (Z) of the laser beam (104) predetermined by the reference values is set. [11] Method according to claim 9 or 10, characterized by that the reference values are taken from further information contained on the identification, valuables or security document. [12] Method according to claim 11, characterized by that the information extracted concerns personal data of the holder of the identification, valuables or security document. [13] Method according to claim 11, characterized by that the information extracted concerns document-specific data of the identification, valuables or security document to be created. [14] Security feature for an identification, valuable or security document, produced by the method according to one of claims 9 to 13. [15] Identification, value or security document with a security feature according to claim 14.

Images