Micro-optical feature readable by concealed machine incorporated into lens layer.

Abstract

Micro-optic devices including micro-optic devices which include an optical spacer (110) having a first side and a second side, an icon layer (120) comprising a plurality of image icons of a first color disposed on the first side of the optical spacer, and a focusing layer (105) comprising a plurality of refractive focusing elements (107) disposed on the second side of the optical spacer. The plurality of refractive focusing elements project a synthetically magnified image of the plurality of image icons, and image icons of the first color project a component of the synthetically magnified image that is of the first color. Additionally, the refractive focusing elements are doped with a machine readable taggant which emits a characteristic signal at a first frequency in the ultraviolet spectrum.

Description

Micro-optical feature readable by concealed machine incorporated in lens layer. Technical field.

[0001] This disclosure relates to enhancing resistance to counterfeiting of secure documents, such as banknotes, passports and other documents, comprising surface-applied micro-optical security devices. More specifically, this disclosure relates to providing a machine-readable feature embedded within a lens layer of a micro-optical device to provide enhanced detectability and consistent signal strength on a machine reader. FUNDAMENTALS

[0002] Strengthening passports, banknotes and other documents (herein referred to as “security documents”) whose construction features include difficult-to-reproduce indications of document authenticity against counterfeiting remains a continuous source of technical challenges and opportunities for improvement in the field of security document design.More specifically, security document designers and designers of security features that are difficult to reproduce (e.g., to balance a range of competing technical and practical objectives, including, without limitation, optical performance requirements (e.g., that the system provides a clearly visible, bright, optically variable effect, thereby enhancing user engagement and visible evidence of authenticity), machine readability requirements (e.g., that the system has one or more latent features whose absence or presence can be reliably detected with specialized equipment), and manufacturing objectives (e.g., that systems that meet the optical performance and machine readability requirements can be produced using industry-standard machines).

[0003] Implementing machine readability and providing a clear synthetic image provides a specific example of the technical challenges. Petition 870250081056, dated 09 / 09 / 2025, page 37 / 60 2 / 18 presented by competing and often mutually exclusive design objectives. Many micro-optical devices that project a synthetic image by means of coordinated magnification of the content in an icon layer by means of an array of focusing elements (e.g., lenses or reflectors) utilize some variation on a three-layer structure with an icon layer comprising the bottom layer, an optical spacer (e.g., a section of transparent material of appropriate thickness to place the icon layer within the focal plane of a focusing layer), and the focusing layer.Typically, these micro-optical devices are attached to a substrate (e.g., a sheet of banknote paper) with the icon side facing down, so that the adhesive holding the device to the substrate is positioned on the underside (furthest from the focusing elements) of the icon layer, and the focusing layer is on the outer side (i.e., closer to the viewer) of the security document. When a machine-readable feature (“MR”) is provided in micro-optical systems constructed in this way, the norm is to incorporate the MR feature below the icon layer (e.g., in an opacifying “camouflage layer” of white or light-colored pigment) or, alternatively, to incorporate the MR feature material within or around the icon layer material.Such approaches, which bury the MR component below the spacer and focusing layer, trade optical performance for machine readability, whereby, while the MR component is situated at a point where it has little or no effect on the system's ability to project a synthetic image, the signal provided by the MR component may be attenuated or distorted as it passes back through the optical spacer and focusing layers on its way to the reading device outside the security document.

[0004] Alternatively, positioning the MR component in a higher layer of the safety device, such as in the focusing layer or optical spacer, generally improves machine readability, but may Petition 870250081056, dated 09 / 09 / 2025, pages 38 / 60 3 / 18 degrade optical performance, as many MR components are pigmented (and therefore may visibly interfere with the images projected by the system) or affect the focusing properties of the focusing layer (e.g., by changing the refractive indices of the lens material).

[0005] Although for many applications, such as very thin micro-optical devices (e.g., 50 microns thick or less) used as authenticity indicators on certain banknotes, signal attenuation is manageable, in other applications, such as thicker and cheaper-to-produce micro-optical security devices used in consumer products (e.g., difficult-to-reproduce authenticity indicators used on product labels for Swiss watches or French wines), the attenuation effect can be significantly more pronounced.

[0006] Therefore, optimizing both machine readability and image clarity in micro-optical systems that utilize a focusing layer remains a source of technical challenges and opportunities for improvement in the art. SUMMARY

[0007] The present disclosure illustrates embodiments of a wet-harvest resistant embossed safety device and methods for its manufacture.

[0008] In a first embodiment, a method includes providing an optical spacer having a first side and a second side, forming an icon layer comprising a plurality of first-color image icons on the first side of the optical spacer; and forming a focusing layer comprising a plurality of refractive focusing elements on the second side of the optical spacer, wherein the plurality of refractive focusing elements projects a synthetically enlarged image of the plurality of image icons, wherein the first-color image icons project a component of the synthetically enlarged image that is of the first color, and wherein the refractive focusing elements of the plurality of refractive focusing elements are doped with a marker readable by Petition 870250081056, dated 09 / 09 / 2025, pp. 39 / 60 4 / 18 machine that emits a characteristic signal at a first frequency in the ultraviolet spectrum.

[0009] In a second embodiment, micro-optical devices comprising an optical spacer having a first side and a second side, an icon layer comprising a plurality of first-color image icons arranged on the first side of the optical spacer, and a focusing layer comprising a plurality of refractive focusing elements arranged on the second side of the optical spacer. The plurality of refractive focusing elements projects a synthetically magnified image of the plurality of image icons, and the first-color image icons project a component of the synthetically magnified image that is of the first color. Furthermore, the refractive focusing elements are doped with a machine-readable marker that emits a characteristic signal at a first frequency in the ultraviolet spectrum.

[0010] Other technical characteristics may be readily apparent to a specialist in the field from the following figures, descriptions and claims.

[0011] Before proceeding with the DETAILED DESCRIPTION below, it may be advantageous to establish definitions of certain words and phrases used in this patent document. The term “coupling” and its derivatives refer to any direct or indirect communication between two or more elements, whether or not those elements are in physical contact with each other. The terms “include” and “comprise,” as well as their derivatives, mean inclusion without limitation. The term “or” is inclusive, meaning and / or. The expression “associated with,” as well as its derivatives, means to include, to be included in, to interconnect with, to contain, to be contained in, to connect to or with, to couple to or with, to be communicable with, to cooperate with, to intercalate, to juxtapose, to be close to, to be linked to or with, to have, to have a property of, to have a relationship with or with, or something similar. The phrase “at least one of,” when used with a list of items, means that different combinations of one or more listed items may be Petition 870250081056, dated 09 / 09 / 2025, pp. 40 / 60 5 / 18 are used, and only one item from the list may be required. For example, “at least one of: A, B, and C” includes any of the following combinations: A, B, and C; A and B; A and C; B and C; and A, B, and C.

[0012] Definitions for other specific words and phrases are provided throughout this patent document. Those with ordinary skill in the field should understand that, in many, if not most, cases, such definitions apply to both past and future uses of such defined words and phrases. BRIEF DESCRIPTION OF THE DRAWINGS

[0013] For a fuller understanding of the present disclosure and its features and advantages, reference will now be made to the following description, taken in conjunction with the accompanying figures, in which:

[0014] FIGURE 1 illustrates an example of a machine-readable micro-optical device according to various embodiments of this disclosure; and

[0015] FIGURE 2 illustrates the operations of an example method for making a device according to various embodiments of this disclosure. DETAILED DESCRIPTION

[0016] Figures 1 and 2, discussed below, and the various modalities used to describe the principles of this disclosure are for illustrative purposes only and should not be interpreted in any way as limiting the scope of the disclosure. Experts in the field will understand that the principles of this disclosure can be implemented in any appropriately organized safety document.

[0017] Although the present disclosure has been described in several embodiments, various changes and modifications may be suggested to one skilled in the art. This disclosure is intended to encompass such changes and modifications that fall within the scope of the appended claims.

[0018] FIGURE 1 illustrates an example of a machine-readable optical security device 100, which is incorporated into a security document 160, according to certain embodiments of this disclosure. Petition 870250081056, dated 09 / 09 / 2025, p. 41 / 60 6 / 18

[0019] Referring to the non-limiting example in FIGURE 1, the optical safety device 100 comprises a plurality of focusing elements 105 (including, for example, focusing element 107) and an arrangement of image icons 120 (including, for example, image icon 121). According to various embodiments, each focusing element of the plurality of focusing elements 105 has a footprint, in which one or more image icons of the arrangement of image icons 120 are positioned.Collectively, the focus elements of the plurality of focus elements 105 magnify portions of image icons 120 to produce a magnification effect (also called a “synthetically magnified image” or, more briefly, a “synthetic image”) in which the individually microscopic image icons are collectively magnified by the plurality of focus elements 105 to produce an image that reacts dynamically (e.g., appearing to move or change color) in response to changes in the viewing angle. Given the small scale and tight manufacturing tolerances of the constituent structures of the optical security device that provide the synthetic magnification effect, many malicious actors are unable to produce counterfeit versions of the optical security device 100. Consequently, the optical security device 100 is, in many cases, a reliable visual indication of the authenticity of a security document (e.g., security document 160).

[0020] According to certain embodiments, the plurality of focusing elements 105 comprises a planar array of micro-optical focusing elements. In some embodiments, the focusing elements of the plurality of focusing elements 105 comprise micro-optical refractive focusing elements (e.g., plano-convex lenses or GRIN). Refractive focusing elements of the plurality of focusing elements 105 are, in some embodiments, produced from photopolymerizable resins with refractive indices ranging from 1.35 to 1.7 and have diameters ranging from 5 μm to 200 μm. In several embodiments, the focusing elements of the plurality of focusing elements 105 comprise reflective focusing elements (e.g., very small concave mirrors). Petition 870250081056, dated 09 / 09 / 2025, p. 42 / 60 7 / 18 with diameters ranging from 5 μm to 50 μm. Although in this illustrative example, the focusing elements of the plurality of focusing elements 105 are shown as comprising circular plano-convex lenses, other refractive lens geometries, for example, lenticular lenses, are possible and are within the contemplated scope of this disclosure. Suitable materials for forming a plurality of focusing elements 105 include, without limitation, substantially transparent, colored or colorless polymers, such as acrylics, acrylated polyesters, acrylated urethanes, epoxies, polycarbonates, polypropylenes and the like. Various methods of providing the focusing element layer may include extrusion, radiation-cured casting, injection molding, reaction injection molding or reaction casting.

[0021] The focusing elements of the plurality of focusing elements 105 (both reflectors and refractive lenses) can be characterized by an F#, which can be adjusted as desired to modify the synthetic image and its optical effect. Suitable F-numbers, in view of the desired thickness of the security film or security device, can be adjusted to be less than 10, or in some modalities less than about 4, or in some modalities, less than 2 or 1. The synthetic image can also be modulated by the relative arrangements and alignments of the focusing element array to the image element array, and each array has respective repetition periods. The repetition periods of the respective arrays can be adjusted so that their ratios are equal to 1, slightly above or slightly below 1; although ratios substantially above and substantially below 1 are also contemplated.The base diameters (equivalent to the base widths for cylindrical lenses) of the focusing elements can also be adjusted as desired, and it is within the scope of this disclosure that these base diameters may have ranges of 200 pm to 500 pm; 50 pm to 200 pm; less than 50 pm (such as less than about 45 pm or ranging from about 10 pm to about 40 pm). The focusing elements can be further modified by adjusting the focal lengths so that... Petition 870250081056, dated 09 / 09 / 2025, pp. 43 / 60 8 / 18 focal lengths allow the image elements in the image element array to be viewed through the focal element and project a synthetic image. Focal lengths shorter than 50 pm are suitable, as are those shorter than 45 pm, ranging from about 10 pm to about 30 pm.

[0022] In addition, the cured photocurable material (e.g., polyacrylate resin) from which a plurality of focusing elements 105 are formed may contain particles or molecules of a machine-readable marker or additive. As used in this disclosure, the term “machine-readable” encompasses materials or arrangements of materials that exhibit one or more properties that are latent to the human eye in daylight but become visibly apparent or detectable under conditions provided by a machine. Examples of machine-readability include, without limitation, upconversion (where a particle receives light energy at a first wavelength and emits light at a second wavelength that is shorter than the first wavelength). Other examples of machine-readable additives include magnetically readable compounds.

[0023] As shown in the illustrative example of FIGURE 1, the image icon array 120 comprises a set of image icons (including image icon 121), positioned at predetermined locations within the footprints of the focus elements of the plurality of focus elements 105. According to various embodiments, the individual image icons of the image icon array 120 comprise regions of photopolymerized material associated with the focal path of structured light (e.g., collimated UV light) passing through a plurality of focus elements 105 from a projection point associated with one or more predetermined ranges of viewing angles. In some embodiments, the individual image icons of the image icon array 120 are not provided within a structured image icon layer.As used in this disclosure, the term "structured image layer" encompasses a layer of material (e.g., a light-cured resin) that has been embossed or otherwise formed to emboss. Petition 870250081056, dated 09 / 09 / 2025, pp. 44 / 60 9 / 18 structures (e.g., recesses, pins, grooves, or tables) for positioning and retaining the image icon material. According to various embodiments, the individual image icons of the 120 image icon array are provided within a structured image layer, the structured image layer comprising one or more voids, tables, or pins, which act as retention structures to retain volumes of colored material at the micro and nanoscale. In some embodiments, the 120 image icon array comprises single-color icons. In other embodiments, the image icons of the 120 image icon array comprise two- or more-color icons.

[0024] Although not shown in FIGURE 1, in certain embodiments, the relief structures of the icon layer, rather than the contrasting interstitial material retained within the relief structures, may operate as image icons. In such embodiments, the relief material may be pigmented and semiopaque, and variations in the thickness of the relief structures may create points of contrast that may be projected through a plurality of focusing elements 105 to provide a synthetic image.

[0025] As shown in the illustrative example of FIGURE 1, in certain embodiments, the optical safety device 100 includes an optical spacer 110. According to various embodiments, the optical spacer 110 comprises a film of substantially transparent material that operates to position image icons of the image icon array 120 in or around the focal plane of the focus elements of the plurality of focus elements 105. In certain embodiments according to this disclosure, the optical spacer 110 comprises a fabrication substrate onto which one or more layers of photopolymerizable material may be applied, to form one or more image icon arrays 120 or plurality of focus elements 105.

[0026] According to various embodiments, the optical safety device 100 comprises one or more regions of photopolymerizable protective material that occupy the spaces between the image icons of the image icon arrangement. Petition 870250081056, dated 09 / 09 / 2025, pages 45 / 60 10 / 18 120. In some embodiments, the image icon array 120 is first formed (e.g., by selective curing and removal of liquid light-curing material in the optical spacer 110), and then a layer of transparent light-curing material is applied to fill spaces between the image icons of the image icon array 120 and then flood-cured to create a protective layer, which prevents the image icons from being moved from their positions within the footprints of the focus elements of the plurality of focus elements 105. In certain embodiments, the light-curing material used to form the image icon array 120 is a pigmented, ultraviolet (UV) curable polymer.

[0027] In some embodiments, the image icon arrangement 120 is fixed to a second substrate 130, which operates to protect and secure the image icon arrangement 120 and provide an interface for attaching the optical security device 100 to a substrate 150 as part of the security document 160. In some embodiments, the optical security device 100 is fixed to the substrate 150 during substrate manufacturing on a paper-making machine, such as a Fourdrinier machine. According to some embodiments, the optical security device 100 is fixed to the substrate 150 by an adhesive layer between the image icon arrangement 120 and an upper surface of the substrate 150.

[0028] In certain embodiments according to this disclosure, the optical safety device 100 comprises a sealing layer 140. According to certain embodiments, the sealing layer 140 comprises a thin layer (e.g., 2 μm to 50 μm thick) of substantially transparent material that interfaces on a lower surface with focusing elements of the plurality of focusing elements 105 and comprises an upper surface with less variation in curvature (e.g., being smooth or having a surface whose local undulations are of a radius of curvature greater than the focusing elements) than the plurality of focusing elements 105. According to various embodiments, the upper surface of the sealing layer 140 is Petition 870250081056, dated 09 / 09 / 2025, pp. 46 / 60 11 / 18 formed from a thermoplastic material that can be ultrasonically welded to a surface comprising a cellulosic material.

[0029] As shown in the non-limiting example of FIGURE 1, in certain embodiments, the optical security device 100 can be attached to the substrate 150 to form a security document 160. According to various embodiments, the substrate 150 comprises a sheet of material with at least one surface comprising cellulosic material, such as wood pulp, cotton fiber, flax fiber, sisal fiber, hemp fiber, abaca fiber, kozo fiber, mitsumata fiber, bamboo fiber, or kenaf fiber. In some embodiments, the substrate 150 is a blend of cotton and flax fibers, such as those used in US banknotes. For example, the substrate 150 may be made of a fiber blend containing between 65-80% cotton fibers and between 20-35% flax fibers. In some forms, the relative proportions of cotton and linen fibers may be such that the substrate contains 65-100% cotton fibers and between 0 and 35% linen fibers.

[0030] Although FIGURE 1 provides an example of an optical security device 100 according to various embodiments, the present disclosure is not so limited. Other optical security devices comprising at least one surface with a thermoplastic polymer and including micro- and nanoscale optical structures that are difficult to reproduce (e.g., holograms, devices providing thin-film effects, devices producing diffraction-based optical effects) that have machine-readable features embedded that do not affect the optical properties of transparent layers above the icon layer are within the contemplated scope of this disclosure. Furthermore, certain embodiments according to this disclosure may include structures not explicitly shown in FIGURE 1, such as a contrast layer or “camouflage” of opacifying material applied to enhance the contrast of the icon layer 120.In some forms, the contrasting material may be a thin layer of white or colored pigment. Petition 870250081056, dated 09 / 09 / 2025, pp. 47 / 60 12 / 18 clear. Alternatively, the contrast layer can be a layer of a reflective material, such as aluminum, zinc, or copper.

[0031] FIGURE 2 describes operations of an example method for creating a machine-readable micro-optical security device according to various embodiments of this disclosure. It should be noted that the operations described with reference to FIGURE 2 do not necessarily need to be performed in the order described and that, depending on the manufacturing process used, certain operations may be omitted or performed in a different sequence. As an illustrative example, in a thin micro-optical spacer system, the steps related to providing an optical spacer may be omitted. As a further illustrative example, icon structures may be formed by means of directional curing, wherein a curing light is passed through the focusing element layer on one side of the device to form icon structures comprising regions of pigmented and cured material on an opposite side of the device.

[0032] Referring to the illustrative example in FIGURE 2, in operation 205, an icon layer (e.g., icon layer 120 in FIGURE 1) is formed on one side of an optical spacer (e.g., optical spacer 110 in FIGURE 1). In certain embodiments, the icon layer is formed by casting cure, in which an initial smooth layer of radiation-curable resin, transparent or substantially colorless (e.g., a polyacrylate) is placed on the optical spacer in a uniform thickness (such as with a Mayer rod) and then engraved with one or more tools with a relief pattern that defines a set of retention structures for colored material in the resin layer. This initial layer of uncured relief material is then radiation-cured (e.g., by flooding the relief material with ultraviolet light or another form of radiation to cause the resin to cure and crosslink).In some embodiments, uncured pigmented photocurable material of a first color is subsequently applied to at least part of the micro-optical structure so that the uncured material fills the gaps. Petition 870250081056, dated 09 / 09 / 2025, pp. 48 / 60 13 / 18 retention structures formed by the stamping tool. The uncured, photocurable pigmented material of the first color is then exposed to curing radiation (e.g., ultraviolet light), and the excess uncured pigmented material is removed from the retention structures. Depending on whether multiple colors are being used in the icon layer, multiple iterations of filling and curing pigmented materials may be performed. Furthermore, in some embodiments, the pigmented material may be applied and cured zonally, with only parts of the device receiving the pigmented material and curing light. According to some embodiments, this approach can produce rigorously registered multicolor patterns of icon structures while avoiding the image degradation associated with lamination, which causes the uncured pigmented material to “smudge” the icon layer.

[0033] In some embodiments, instead of filling the negative spaces (i.e., pits) created in the icon layer by the emboss tool with pigmented material, the pigmented material can be applied to the positive regions (i.e., tables) formed by the emboss tool and then cured. In such embodiments, the step of thinning the icon layer as part of operation 205 can be avoided.

[0034] As shown in FIGURE 2, in operation 210, the uncured resin for the focusing element assembly (e.g., focusing element assembly 105 in FIGURE 1) is doped with one or more compounds that provide machine readability and, at the same time, can be supplied in concentrations that do not affect the native optical properties of the material used to form the focusing element assembly and, at the same time, provide a reliable machine response. According to various embodiments, a volume of uncured acrylate resin is doped with an up-convert marker (e.g., Honeywell Corporation's Lumilux MRG-100) at a concentration of 0.1 to 0.6% of the total mixture weight. As used in this disclosure, the term “up-convert” refers to Petition 870250081056, dated 09 / 09 / 2025, pages 49 / 60 14 / 18 chemicals that absorb light energy in a first frequency range and emit light energy in a second, higher frequency range. In the case of Lumilux, this up-converter absorbs light in the infrared portion of the EV spectrum and emits light in the ultraviolet portion of the spectrum. According to certain embodiments, the machine-readable marker is provided as a suspension within the radiation-curable lens material and is kept suspended within the uncured lens material by the addition of a surfactant at the time the lens material is doped with the machine-readable compound.

[0035] Qualified technicians will recognize that Lumilux comprises only one non-limiting example of a machine-readable additive that may be supplied to uncured lens material in accordance with various embodiments of this disclosure. Other additives, such as strontium-aluminum-based pigments, may also be used in similar concentrations to dope uncured lens material with similar results.

[0036] Referring to the illustrative example in FIGURE 2, in operation 215, the focusing element layer (e.g., focusing layer 105 in FIGURE 1) is formed. According to various embodiments, the focusing layer is formed by applying a layer of the uncured lens material created in operation 210 (e.g., spreading a layer of consistent thickness with a Mayer rod) across an opposite side of the optical substrate from the side with the icon layer and etching the uncured material to create a relief structure that provides a curved interface between the lens material and a different refractive index (RI) material. In some embodiments, the different refractive index material is air, and the relief structure forms a plurality of convex lenses. In some embodiments, the different refractive index material is a sealing layer (e.g., sealing layer 140 in FIGURE 1).In applications where the sealing layer has a higher IR than the lenses, the uncured lens material can be embossed to create a... Petition 870250081056, dated 09 / 09 / 2025, pages 50 / 60 15 / 18 plurality of concave lenses.

[0037] In some embodiments, after stamping, the uncured and doped lens material is bathed in actinic radiation (e.g., ultraviolet light) to initiate curing and crosslinking of the resin. Depending on the design and if a sealing layer is specified in the design, an additional layer of transparent material may be applied over the lenses.

[0038] According to various embodiments, operations 205-215 produce a micro-optical security device that has a machine-readable characteristic signal that is detectable both on quality control equipment, which normally emits a pass / fail signal, and on production equipment, such as that used by the US Bureau of Engraving, which emits a qualitative measurement of the signal intensity, with a range of intermediate values ​​indicating pass and the upper (i.e., saturated signal) and lower ends of the response curve indicating failure or over-doping.

[0039] As noted elsewhere in this disclosure, by doping the top layers (i.e., the lens layer) of the micro-optical system with an optically neutral, machine-readable compound, certain embodiments according to the present disclosure provide the technical benefit of providing reliable machine readability in thicker micro-optical devices (e.g., greater than 70 microns total thickness) than can be achieved by applying the machine-readable component in a camouflage layer beneath the icon layer.

[0040] Examples of micro-optical devices according to certain embodiments of the disclosure include micro-optical devices comprising an optical spacer having a first side and a second side, an icon layer comprising a plurality of image icons of a first color arranged on the first side of the optical spacer, and a focusing layer comprising a plurality of refractive focusing elements arranged on the second side of the optical spacer. The plurality of Petition 870250081056, dated 09 / 09 / 2025, pages 51 / 60 16 / 18 refractive focusing elements project a synthetically enlarged image of the plurality of image icons, and the first-color image icons project a component of the synthetically enlarged image that is of the first color. Furthermore, the refractive focusing elements are doped with a machine-readable marker that emits a characteristic signal at a first frequency in the ultraviolet spectrum.

[0041] Examples of micro-optical devices according to certain embodiments of this disclosure include micro-optical devices in which the machine-readable marker is a phosphorescent up-converter that absorbs light energy at a second frequency in the infrared spectrum.

[0042] Examples of micro-optical devices according to certain embodiments of this disclosure include micro-optical devices in which the machine-readable marker is a strontium aluminate-based pigment.

[0043] Examples of micro-optical devices according to certain embodiments of this disclosure include micro-optical devices in which the machine-readable marker is provided as a suspension in a radiation-curable polymer.

[0044] Examples of micro-optical devices according to certain embodiments of this disclosure include micro-optical devices in which the machine marker is provided at a concentration between 0.1 and 0.6% by weight of a mixture of marker and radiation-curable polymer.

[0045] Examples of micro-optical devices according to certain embodiments of this disclosure include micro-optical devices comprising a surfactant for keeping the machine-readable marker suspended before curing.

[0046] Examples of micro-optical devices according to certain embodiments of this disclosure include micro-optical devices where the device does not comprise a background coating applied to the icon layer.

[0047] Examples of micro-optical devices according to certain Petition 870250081056, dated 09 / 09 / 2025, pp. 52 / 60 17 / 18 embodiments of this disclosure include micro-optical devices in which the micro-optical safety device has a thickness of 75 microns or greater.

[0048] Examples of methods for making micro-optical devices according to various embodiments of this disclosure include methods comprising providing an optical spacer having a first side and a second side, forming an icon layer comprising a plurality of image icons of a first color on the first side of the optical spacer; and forming a focusing layer comprising a plurality of refractive focusing elements on the second side of the optical spacer, wherein the plurality of refractive focusing elements projects a synthetically enlarged image of the plurality of image icons, wherein the image icons of the first color project a component of the synthetically enlarged image that is of the first color, and wherein the refractive focusing elements of the plurality of refractive focusing elements are doped with a machine-readable marker that emits a characteristic signal at a first frequency in the ultraviolet spectrum.

[0049] Examples of methods for making micro-optical devices according to certain embodiments of this disclosure include methods in which the machine-readable marker is an up-converter that absorbs light energy at a second frequency in the infrared spectrum.

[0050] Examples of methods for making micro-optical devices according to various embodiments of this disclosure include methods in which the machine-readable marker is a strontium aluminate-based pigment.

[0051] Examples of methods for making micro-optical devices according to various embodiments of this disclosure include methods in which the machine-readable marker is provided as a suspension in a radiation-curable polymer.

[0052] Examples of methods for making micro-optical devices according to various embodiments of this disclosure include methods in which the marker Petition 870250081056, dated 09 / 09 / 2025, pp. 53 / 60 18 / 18 per machine is supplied in a concentration between 0.1 and 0.6% by weight of a mixture of marker and radiation-curable polymer.

[0053] Examples of methods for making micro-optical devices according to various embodiments of this disclosure include methods further comprising a surfactant to keep the machine-readable marker suspended before curing.

[0054] Examples of methods for making micro-optical devices according to various embodiments of this disclosure include methods in which the device does not comprise a background coating applied to the icon layer.

[0055] Examples of methods for making micro-optical devices according to various embodiments of this disclosure include methods in which the micro-optical safety device has a thickness of 75 microns or greater.

[0056] Although the present disclosure has been described in several embodiments, various changes and modifications may be suggested to one skilled in the art. This disclosure is intended to encompass such changes and modifications that fall within the scope of the appended claims.

Claims

1. Micro-optical safety device, characterized in that it comprises: an optical spacer (110) having a first side and a second side; an icon layer (120) comprising a plurality of first-color image icons arranged on the first side of the optical spacer; and a focusing layer (105) comprising a plurality of refractive focusing elements (107) arranged on the second side of the optical spacer, wherein the plurality of refractive focusing elements project a synthetically enlarged image of the plurality of image icons, wherein first-color image icons project a component of the synthetically enlarged image that is of the first color, and wherein refractive focusing elements of the plurality of refractive focusing elements are doped with a machine-readable marker that emits a characteristic signal at a first frequency in the ultraviolet spectrum.

2. Micro-optical security device, according to claim 1, characterized in that the machine-readable marker is a phosphorescent up-converter that absorbs light energy at a second frequency in the infrared spectrum.

3. Micro-optical security device, according to claim 1, characterized in that the machine-readable marker is a strontium aluminate-based pigment.

4. Micro-optical security device, according to claim 1, characterized in that the machine-readable marker is provided as a suspension in a radiation-curable polymer.

5. Micro-optical security device, according to claim 4, characterized in that the machine-readable marker Petition 870250081056, dated 09 / 09 / 2025, page 55 / 60 2 / 3 is provided in a concentration of 0.1 to 0.6% by weight of a mixture of marker and radiation-curable polymer.

6. Micro-optical safety device, according to claim 4, characterized in that it further comprises a surfactant for keeping the machine-readable marker suspended before curing.

7. Micro-optical security device, according to claim 1, characterized in that the device does not comprise a background coating applied to the icon layer.

8. Micro-optical safety device, according to claim 1, characterized in that the micro-optical safety device has a thickness of 75 microns or greater.

9. Method for making a micro-optical security device, the method characterized in that it comprises: providing an optical spacer having a first side and a second side; forming an icon layer (205) comprising a plurality of image icons of a first color on the first side of the optical spacer; and forming a focusing layer (210, 215) comprising a plurality of refractive focusing elements on the second side of the optical spacer, wherein the plurality of refractive focusing elements project a synthetically enlarged image of the plurality of image icons, wherein the image icons of the first color project a component of the synthetically enlarged image that is of the first color, and wherein the refractive focusing elements of the plurality of refractive focusing elements are doped with a machine-readable marker that emits a characteristic signal at a first frequency in the ultraviolet spectrum.

10. Method according to claim 9, characterized in that the machine-readable marker is a phosphorescent up-converter that absorbs light energy at a second frequency in the infrared spectrum. Petition 870250081056, dated 09 / 09 / 2025, page 56 / 60 3 / 3 11. Method according to claim 9, characterized in that the machine-readable marker is a strontium aluminate-based pigment.

12. Method according to claim 9, characterized in that the machine-readable marker is provided as a suspension in a radiation-curable polymer.

13. Method according to claim 12, characterized in that the machine-readable marker is provided in a concentration of 0.1 to 0.6% by weight of a mixture of marker and radiation-curable polymer.

14. Method according to claim 12, characterized in that it further comprises adding a surfactant to keep the machine-readable marker suspended before curing.

15. Method according to claim 9, characterized in that the device does not comprise a background coating applied to the icon layer.

16. Method according to claim 9, characterized in that the micro-optical safety device has a thickness of 75 microns or greater.

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