A laser engraving apparatus (100) is calibrated using a number of predetermined calibration images (12). The calibration images (12) are engraved on a predefined substrate surface (14, 15) of a substrate (16) by varying only a single laser parameter. Based on measured colour values of the engraved calibration images, a relationship between said colour values and a predefined laser parameter value, for example, a predefined laser power, is established. This relationship is then used to generate a map for mapping a grayscale value of an input image to a grayscale value of an output image, which is then engraved on the substrate (16) while varying the same laser parameter that was varied during the calibration.

Personalizing a multipage security document by placing a laser-alterable ink layer on a personalization area of an edge of each of the sequence of pages. The method includes revealing a portion of the personalization area of each of the sequence of pages relative to a pages above said each of the sequence of pages such that the personalization portion of each two consecutive pages in said sequence of pages are located adjacent to one another thereby producing a two-dimensional multi-page personalization section, and creating a pattern on the two-dimensional multi-page personalization section by altering the inked personalization area in the revealed portion of each page of said sequence of pages by exposing said revealed portions to a laser, such that a pattern is visible when the revealed portions of a sequence of pages are viewed simultaneously.

A process of forming a non-optically detectable authentication marking (110), includes the step of: applying a marking at a surface of a diamond (200) using a focused ion beam (FIB) writing process so as to provide a non-optically detectable authentication marking (110) which is formed by alteration in the optical characteristics of a portion of the diamond material at the outer surface of the diamond to form a marked portion; wherein the marking is optically invisible, and wherein the marking is viewable by an imaging method which provides an observable contrast between the portion of the diamond having altered optical characteristics and the non-marked portion of the diamond. The marking process can assist in the prevention of the counterfeiting of precious articles, and be of assistance in the incident of theft. A marking, a diamond, a process of viewing a marking on a diamond are further disclosed.

A process of forming a non-optically detectable authentication marking (110), includes the step of: applying a marking at a surface of a diamond (200) using a focused ion beam (FIB) writing process so as to provide a non-optically detectable authentication marking (110) which is formed by alteration in the optical characteristics of a portion of the diamond material at the outer surface of the diamond to form a marked portion; wherein the marking is optically invisible, and wherein the marking is viewable by an imaging method which provides an observable contrast between the portion of the diamond having altered optical characteristics and the non-marked portion of the diamond. The marking process can assist in the prevention of the counterfeiting of precious articles, and be of assistance in the incident of theft. A marking, a diamond, a process of viewing a marking on a diamond are further disclosed.

Disclosed are optical devices suitable as security devices for document authentication, which comprise at least one two-dimensional array of elongate laser-modified tracks extending within a document substrate that have a distinct optical refractive index compared to the unmodified substrate, which can exhibit excellent diffractive effects. Also disclosed are the use of such devices for document authentication and methods for their production.

Disclosed are optical devices suitable as security devices for document authentication, which comprise at least one two-dimensional array of elongate laser-modified tracks extending within a document substrate that have a distinct optical refractive index compared to the unmodified substrate, which can exhibit excellent diffractive effects. Also disclosed are the use of such devices for document authentication and methods for their production.

A security element for securing security papers, value documents and other data carriers, includes a lens grid image with a lens grid of a plurality of micro lenses and a radiation-sensitive motif layer arranged at a distance from the lens grid. The radiation-sensitive motif layer includes, in one motif region, a multiplicity of transparency regions produced by the action of radiation. The radiation-sensitive motif layer has, at least in the motif region, a color partial layer and a contrast partial layer. The color partial layer includes chromophore effect pigments which appear to be colored against the background of the contrast partial layer and which appear to be transparent without a contrast layer.

A security element for securing security papers, value documents and other data carriers, includes a lens grid image with a lens grid of a plurality of micro lenses and a radiation-sensitive motif layer arranged at a distance from the lens grid. The radiation-sensitive motif layer includes, in one motif region, a multiplicity of transparency regions produced by the action of radiation. The radiation-sensitive motif layer has, at least in the motif region, a color partial layer and a contrast partial layer. The color partial layer includes chromophore effect pigments which appear to be colored against the background of the contrast partial layer and which appear to be transparent without a contrast layer.

A method is provided for producing banknotes, which include, in each case, at least one integrated circuit. The banknotes are produced from a sheet or from a material web in a production panel. In at least a plurality of these banknotes, or in each of these banknotes, an aperture is created through their substrate. In each case, an integrated circuit is arranged in the relevant aperture. In a first method step, each of the integrated circuits to be arranged in one of the apertures is arranged, with respect to the intended position in each of the banknotes that include an aperture, in the correct position on a band-shaped foil, and, in the second method step, each of these integrated circuits is transferred from this band-shaped foil onto the relevant banknote. Owing to this transfer carried out in the second method step, one integrated circuit in each case, is arranged in the aperture created in the banknotes.

A method is provided for producing banknotes, which include, in each case, at least one integrated circuit. The banknotes are produced from a sheet or from a material web in a production panel. In at least a plurality of these banknotes, or in each of these banknotes, an aperture is created through their substrate. In each case, an integrated circuit is arranged in the relevant aperture. In a first method step, each of the integrated circuits to be arranged in one of the apertures is arranged, with respect to the intended position in each of the banknotes that include an aperture, in the correct position on a band-shaped foil, and, in the second method step, each of these integrated circuits is transferred from this band-shaped foil onto the relevant banknote. Owing to this transfer carried out in the second method step, one integrated circuit in each case, is arranged in the aperture created in the banknotes.