Micro-optical security device with phase-aligned image layer - Patent Application 20070122997

Abstract

The micro-optical security device (105) includes a planar array (305) of microlenses configured to focus light along a plurality of focal paths (610) associated with viewing angles. The micro-optical security device further includes an icon layer stack (905) arranged along the plurality of focal paths. The icon layer stack includes a first icon layer (620) comprising a volume (613b) of curable material of a first color and a volume (637a) of substantially transparent material at a location outside the focal paths for a first viewing angle range. The icon layer stack also includes a second icon layer (640) comprising a volume (637a) of substantially transparent curable material at a location along the focal path for the first viewing angle range and a volume (637a) of a second color of curable material at a location along the focal path for a second viewing angle range.

Description

[Technical field]

[0001] The present disclosure relates to a system for enhancing the counterfeit resistance of security documents, and more particularly, to a micro-optical security device having phase-aligned image layers. [Background technology]

[0002] Depending on their configuration and incorporation into end products, micro-optical security devices with dynamic and difficult to replicate appearances can greatly improve the counterfeit resistance of security documents such as currency, passports, and other documents that require a reliable visual indicia of authenticity. The overall effectiveness of a particular micro-optical security device depends on several variables, including, but not limited to, the uniqueness of the visual effect produced by the device, the difficulty of replicating, and the ability to mass-produce the device. For example, a micro-optical security device that produces an unclear or visually uninteresting visual effect is unlikely to be noticed by most end users, and by implication, the absence of the device is likely to be similarly unnoticed by end users. In such cases, a counterfeit document without a proper micro-optical security device is more likely to circulate undetected than one in which the micro-optical security device produces a visual effect that is noticeable to end users through a combination of clarity and novelty. Similarly, the effectiveness of a micro-optical security device is improved when micro-optical security devices can be mass-produced, thereby lowering the cost and facilitating widespread adoption. Pushing the boundaries to achieve more distinctive visual effects that are beyond the reach of counterfeiters, yet can at the same time be mass-produced by legitimate parties, remains a source of technical challenges and opportunities for improvement in the field of micro-optical security device design. Summary of the Invention [Problem to be solved by the invention]

[0003] The present disclosure presents embodiments of a micro-optical security device having phase-aligned image layers. [Means for solving the problem]

[0004] In a first embodiment, the micro-optical security device includes a planar array of microlenses configured to focus light along a plurality of focal paths associated with a viewing angle of the micro-optical security device. The micro-optical security device further includes an icon layer stack disposed along the plurality of focal paths. The icon layer stack includes a first icon layer comprising a volume of a first color of hardened material at a location along the focal path at a first viewing angle range and a volume of a substantially transparent material at a location outside the focal path at the first viewing angle range. The icon layer stack also includes a second icon layer disposed below the first icon layer relative to the planar array of microlenses. The second icon layer further includes a volume of a substantially transparent material at a location along the focal path at a first viewing angle range and a volume of a second color of hardened material at a location along the focal path at a second viewing angle range. At least one of the first icon layer or the second icon layer includes a plurality of substantially transparent retaining structures.

[0005] In a second embodiment, the micro-optical security device includes a planar array of focusing elements configured to focus light along a plurality of focal paths associated with a viewing angle of the micro-optical security device. The micro-optical security device further includes an icon layer stack disposed along the plurality of focal paths. The icon layer stack includes an icon layer stack of a first color of directionally curable material associated with a first viewing angle range of the micro-optical security device. The icon layer stack includes a first icon layer having a volume of directionally curable material of a second color at a location along the focal path in a second viewing angle range. At least one of the first icon layer or the second icon layer includes a plurality of substantially transparent retention structures. And, the second viewing angle range does not occupy the same area as the first viewing angle range.

[0006] Other technical features will be readily apparent to those skilled in the art from the following drawings, descriptions and claims.

[0007] Before beginning the detailed description below, it may be convenient to provide definitions of certain words and phrases used throughout this patent document. The term "coupled" 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 one another. The terms "including" and "comprising," and their derivatives, mean an open-ended inclusion. The term "or" is inclusive and / or. The phrase "related to" and its derivatives mean including, contained within, interconnected with, containing, contained within, connected to, coupled to, communicable with, cooperate with, sandwiched between, juxtaposed with, adjacent to, coupled to, having, having a characteristic of, relating to, and the like. The phrase "at least one of," when used in conjunction with a list of items, means that different combinations of one or more of the listed items may be used, and only one item in the list may be required. For example, "at least one of A, B, and C" includes any of the combinations of A, B, C, A and B, A and C, B and C, and A, B, and C.

[0008] Definitions of other specific phrases are provided throughout this patent document, and those of skill in the art will understand that in many, if not most, cases such definitions apply to the prior and future uses of the words and phrases so defined.

[0009] For a more complete understanding of the present disclosure, and the advantages thereof, reference is now made to the following description taken in conjunction with the accompanying drawings, in which like reference numerals represent like parts and in which: [Brief description of the drawings]

[0010] [Figure 1A]1 illustrates an example micro-optical security device according to various embodiments of the present disclosure and aspects of the operation of the micro-optical security device; [Figure 1B] 1 illustrates an example micro-optical security device according to various embodiments of the present disclosure and aspects of the operation of the micro-optical security device; [Figure 2A] By way of background, aspects of the technical challenges associated with achieving phase alignment in micro-optical security devices are presented. [Figure 2B] By way of background, aspects of the technical challenges associated with achieving phase alignment in micro-optical security devices are presented. [Figure 3A] 1 illustrates structural aspects of a micro-optical security device according to some embodiments of the present disclosure. [Figure 3B] 1 illustrates structural aspects of a micro-optical security device according to some embodiments of the present disclosure. [Figure 3C] 1 illustrates structural aspects of a micro-optical security device according to some embodiments of the present disclosure. [Figure 4A] 1 illustrates aspects of the contribution of stacked individual icon layers of a micro-optical security device in accordance with certain embodiments of the present disclosure. [Figure 4B] 1 illustrates aspects of the contribution of stacked individual icon layers of a micro-optical security device in accordance with certain embodiments of the present disclosure. [Figure 5A] 1 illustrates, from multiple perspectives, examples of how to form a surface mounted image icon according to some embodiments of the present disclosure. [Figure 5B] 1 illustrates, from multiple perspectives, examples of how to form a surface mounted image icon according to some embodiments of the present disclosure. [Figure 5C] 1 illustrates, from multiple perspectives, examples of how to form a surface mounted image icon according to some embodiments of the present disclosure. [Figure 6A] 1 illustrates structural aspects of a micro-optical security device according to various embodiments of the present disclosure. [Figure 6B]1 illustrates structural aspects of a micro-optical security device according to various embodiments of the present disclosure. [Figure 6C] 1 illustrates structural aspects of a micro-optical security device according to various embodiments of the present disclosure. [Figure 6D] 1 illustrates structural aspects of a micro-optical security device according to various embodiments of the present disclosure. [Figure 6E] 1 illustrates structural aspects of a micro-optical security device according to various embodiments of the present disclosure. [Figure 6F] 1 illustrates structural aspects of a micro-optical security device according to various embodiments of the present disclosure. [Figure 6G] 1 illustrates structural aspects of a micro-optical security device according to various embodiments of the present disclosure. [Figure 6H] 1 illustrates structural aspects of a micro-optical security device according to various embodiments of the present disclosure. [Figure 6I] 1 illustrates structural aspects of a micro-optical security device according to various embodiments of the present disclosure. [Figure 7] 1 illustrates structural aspects of a micro-optical security device according to certain embodiments of the present disclosure. [Figure 8A] 1 illustrates structural aspects of a micro-optical security device according to some embodiments of the present disclosure. [Figure 8B] 1 illustrates structural aspects of a micro-optical security device according to some embodiments of the present disclosure. [Figure 9] 1 illustrates structural aspects of a micro-optical security device according to various embodiments of the present disclosure. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0011] 1A-9 described below and the various embodiments used to illustrate the principles of the present disclosure are for illustrative purposes only and should not be construed as limiting the scope of the present disclosure. Those skilled in the art will appreciate that the principles of the present disclosure can be implemented in a variety of appropriately configured micro-optical security devices.

[0012] Although the present disclosure is described with various embodiments, various changes and modifications may be suggested to one skilled in the art. The present disclosure is intended to cover such changes and modifications that fall within the scope of the claims.

[0013] 1A and 1B show an example of a micro-optical security device according to certain embodiments of the present disclosure and aspects of the operation of the micro-optical security device.

[0014] 1A-1B, there is provided a first view 101 (shown in FIG. 1A) and a second view 151 (shown in FIG. 1B) of a security document 105 including a micro-optical security device 110. According to various embodiments, the security document 105 may be a passport, currency, an ID card, or any other visually significant document that has a trusted source of authenticity. 1A-1B, a micro-optical security device 110 includes a layer of focusing elements (e.g., microlenses) and an image stack including regions where two or more layers of image icons are phased. As used in this disclosure, the term "phased" in reference to icon structures within layers of a multi-layer icon stack encompasses properties such that colored icons of a first icon layer occupy positions in the first icon layer associated with a focal path of a first viewing angle range, colored icons of a second icon layer occupy positions in the second icon layer associated with a focal path of a second viewing angle range, colored icons of the first icon layer occupy positions in the first icon layer associated with a focal path outside the second viewing angle range, and colored icons of the second icon layer occupy positions in the second layer associated with a focal path outside the first viewing angle range. Specifically, when colored image icons are phased according to certain embodiments of the present disclosure, there is no crosstalk, i.e., colored image icons from two or more layers of the icon stack are simultaneously focused by the focusing elements in a given viewing angle range. Output The state in which the camera is placed is controlled almost entirely by a micro-optical security device. OutputIn accordance with certain embodiments of the present disclosure, controlling the occurrence of crosstalk between layers of image icons facilitates the creation of micro-optical security devices that are improved along at least three dimensions along which performance of the micro-optical security device is measured. Specifically, phasing between image icons can be used as a controllable design parameter to improve the accuracy of the micro-optical security device's ability to provide a first viewing angle range with a first phase alignment between the image icons. Output The multi-color composite image is then imaged over a second viewing angle range by a micro-optical security device. Output The transition between the icon layer and the composite image can be sharper, and embodiments according to the present disclosure can produce both a multi-color "flicker" effect, for example, where the composite image includes colored components that appear and disappear quickly, and an effect where the colored regions of the composite image move or change gradually. Incorporating a multi-color "flicker" effect in addition to a gradually evolving color effect can provide a composite image that is eye-catching and catches the viewer's attention. Furthermore, achieving phase alignment between the layers of the icon layer poses additional manufacturing challenges, and implicitly makes such devices more difficult to counterfeit by malicious actors. Third, certain embodiments according to the present disclosure can be manufactured using structured icon tooling (e.g., a mold for embossing retention structures into a layer of UV-curable polymer), and thus can now be manufactured in large quantities.

[0015] When the security document 105 is oriented such that the surface of the document occupies values ​​within a first viewing angle range Θ1→Θ2 of the coordinate system 115, as shown in the first view 101, the icon structure and light gathering elements of the micro-optical security device 110 generate a first two-color composite image 120 that includes a pair of ellipses of a first color within a polygonal field of a contrasting second color. OutputAs shown in the example of Figures 1A-1B, the observer tilts the security document 105 through a first viewing angle range Θ1 → Θ2 until it enters a second viewing angle range Θ2 → Θ3 shown in second view 151. In this example, as the document moves from the first viewing angle range to the second viewing angle range, the pair of ellipses is "intercepted" and the micro-optical system produces a second composite image, which in this illustrative example is a polygonal field of a contrasting second color, as shown in second view 151. Output Thus, the micro-optical system according to various embodiments of the present disclosure provides a sharp transition from one composite image to another as the device moves across a range of viewing angles.

[0016] 1A-1B provide an example of a transition from a two-color composite image to a monochromatic composite image, embodiments according to the present disclosure are not so limited and additional embodiments including more colors and viewing angle ranges are possible and within the intended scope of the present disclosure. Additionally, embodiments in which the colored icons in multiple layers of the icon layer stack are the same color (creating an interesting motion effect as the focusing element transitions from focusing on an icon at a first depth to focusing on an icon at a second depth) are possible and within the intended scope of the present disclosure.

[0017] 2A-2B provide background to aspects of the technical challenges associated with achieving phase alignment in micro-optical security devices.

[0018] In the illustrative example of Figures 2A-B, a first view 201 (shown in Figure 2A) and a second view 251 (shown in Figure 2B) of a micro-optical cell 200 are shown. A micro-optical security device includes a plurality (typically millions or more) of micro-optical cells. At a basic level, a micro-optical cell includes a focusing element and one or more icon structures within the focal area (also called the "footprint") of the focusing element. In the illustrative example of Figures 2A-B, the micro-optical cell 200 includes a focusing element 205, which in this example is a plano-convex microlens. Other focusing elements are possible, including but not limited to reflective focusing elements (i.e., very small curved mirrors) and gradient index ("GRIN") lenses.

[0019] In this example, the micro-optical cell 200 further includes an image icon layer 210, which includes a holding structure (e.g., holding structure 211) in which an icon 213 of a colored material can be formed. The icon 213 is projected to the viewer by the light collecting element 205. Output The angle Θa at which the icon is focused depends on its position within the footprint of the focusing element 205 (indicated by left and right boundaries 217a and 217b). As shown in relation to a second view 251, a small shift (movement) 253 in the position of the icon relative to the footprint of the focusing element 205 causes the icon 213 to appear to the viewer. Output The angle Θ b This will lead to change. When mass manufactured, there will generally inevitably be some variation in the alignment of the retaining structures of the graphical icon layer 210 relative to the footprints of the focusing elements. In certain real-world applications, the variation in alignment between the focusing elements can be on the order of the pitch of the lenses in the lens array.

[0020] In the context of a micro-optical security device having a single image icon layer, variations in the alignment of the image icon layer with respect to the light collection elements may result in a particular composite image appearing to an observer. OutputThis can be apparent to the end user as variations in the range of angles at which a particular composite image is displayed. In many applications utilizing a single icon layer, this variation in the viewing angle at which a particular composite image is displayed is not a problem, or at most a minor inconvenience, in that the user must "play" with the security document to find the viewing angle at which a particular composite image is displayed. In the context of a micro-optical security device in which two or more icon layers are stacked, the aforementioned alignment variations translate into variations in the extent to which the colored icons of the icon layers are aligned with one another. These variations in alignment between the icon layers can result in the colored icons being displayed by the micro-optical security device over a changing range of viewing angles. Output For example, the micro-optical system may be used to generate a first composite image 120 as described with reference to the non-limiting example of FIGS. 1A-1B. Output Instead of a sharp switch from the first composite image 155 to the second composite image 155, components of the first and second composite images are simultaneously displayed over an intermediate angular range. Output Depending on the extent and nature of the layer alignment problems, Output The resulting image may have a gradual color-changing effect (as opposed to a defined "on-off" or "flicker" effect), a blending of two or more colors, or different colors on different icon layers that are angled relative to each other. Output This can manifest itself in a variety of ways as a visual cacophony of sounds.

[0021] Figures 3A, 3B, and 3C show examples of micro-optical security devices and security documents having phase-aligned image layers according to various embodiments of the present disclosure, and for convenience, structures common to one or more of Figures 3A-C are numbered the same.

[0022] Referring to the non-limiting example of FIG. 3A, a micro-optical shield according to various embodiments of the present disclosure. An example of a security device 301 is shown in the figure.

[0023] Referring to the non-limiting example of FIG. 3A, the micro-optical security device 301 includes, at a basic level, a planar array of light collection elements 305 (including, for example, light collection element 307) and an icon layer stack 308 with a first icon layer 320 (including, for example, image icon 321) and a second image icon layer 323 (including, for example, image icon 324). According to various embodiments, each light collection element of the planar array of light collection elements 305 has a footprint. Furthermore, the planar array of light collection elements includes one or more cells in which one or more image icons of the first icon layer 320 or the second image icon layer 323 array are disposed. Furthermore, the icon layer stack 308 includes at least one region in which the colored image icons of the first icon layer 320 and the colored image icons of the second image icon layer 323 are phase-aligned. In certain embodiments, the locations of the pictorial icons (e.g., pictorial icon 321 or 324) correspond to locations in a holding structure of a substantially transparent material, such as a UV-curable resin, that is embossed and then cured to form a pictorial icon layer having structures, such as voids, posts, or mesas, onto which a colorant material can be selectively deposited. According to some embodiments, the individual focusing elements of the planar array of focusing elements 305 are arranged with one or more local repeat periods. The term "local repeat period" as used in this disclosure encompasses expressions related to how frequently a particular feature of a layer of the micro-optical security device 301 repeats within an area of ​​interest. As an example, the focusing elements of the planar array of focusing elements 305 may have a local repeat period of 50 lenses per mm in one area of ​​the system and 49 lenses per mm in a different portion. Similarly, the colored icons in the first icon layer 320 may have a local repeat period of, for example, 51 icons per mm in one portion of the micro-optical security device 301 and 49.5 icons per mm in a different area of ​​the micro-optical security device 301. By varying the ratio of the local repeat period of the light collecting elements to the icon structure, the light collecting elements can OutputThe appearance of the composite image of the colored icon structure can be adjusted. For example, the apparent location of the composite image relative to the plane of the micro-optical security device 301 can be altered by the ratio of the local repeat period of the light collection elements to the local repeat period of the icon structure, making the composite image appear to float above or lie below the plane of the micro-optical security device 301 (sometimes referred to as a "deep" or "super deep" effect). Similarly, in certain embodiments, the ratio of the local repeat period of the light collection elements to the local repeat period of the colored icon structure can itself be locally altered to give the composite image a more three-dimensional appearance.

[0024] According to certain embodiments, the plurality of focusing elements 305 comprises a planar array of micro-optic focusing elements. In some embodiments, the focusing elements of the planar array of focusing elements 305 comprise micro-optic refractive focusing elements (e.g., plano-convex lenses or GRIN microlenses) having lens surfaces that provide a curved interface between regions of different refractive indices (e.g., polymer lens material and air). The refractive focusing elements of the planar array of focusing elements 305 are fabricated from a photocurable resin having a refractive index in the range of 1.35-2.05 in some embodiments and have diameters in the range of 5 μm-200 μm. In various embodiments, the focusing elements of the planar array of focusing elements 305 comprise reflective focusing elements (e.g., very small concave mirrors) with diameters ranging from 5 μm-50 μm. In this illustrative example, the focusing elements of the planar array of focusing elements 305 are shown as comprising circular plano-convex lenses, although other refractive lens shapes, such as lenticular lenses, are possible and within the contemplation of the present disclosure.

[0025] As shown in the illustrative example of FIG. 3A, the first layer of image icons 320 includes image icons (including image icons 321) located at positions within the footprint of the focusing elements of the planar array of focusing elements 305 associated with a range of directional curing angles. The first icon layer 320 includes a set of image icons. According to various embodiments, each image icon in the first icon layer 320 includes an area of ​​directionally cured material in some or all of the space defined by the retaining structures of the structured image icon layer formed from a substantially transparent material. As used in this disclosure, the term "structured image layer" encompasses a layer of substantially transparent material (e.g., a photocurable resin) that is embossed or otherwise formed to include structures (e.g., recesses, posts, grooves, or mesas) for positioning and retaining image icon material.

[0026] As shown in the illustrative example of FIG. 3A, in certain embodiments, the micro-optical system 301 includes an optical spacer 310. According to various implementations, the optical spacer 310 includes a film of a substantially transparent material that functions to position one or more of the arrays of image icons of the icon layer stack 308 in or around the focal plane of the light-collecting elements of the planar array of light-collecting elements 305. In certain embodiments according to the present disclosure, the optical spacer 310 includes a fabrication substrate on which one or more layers of a photocurable material can be applied, embossed, and flood cured to form a support structure. In certain embodiments, the photocurable material used to form the first icon layer 320 is an ultraviolet (UV) curable pigmented polymer. In various embodiments according to the present disclosure, the optical spacer 310 includes an applied intermediate layer of a transparent UV-curable polymer (e.g., a polymer used to fabricate the light-collecting elements of the planar array of light-collecting elements 305) between the light-collecting elements and the icon layer stack 308.

[0027] In certain embodiments according to the present disclosure, the micro-optical security device 301 comprises a sealing layer 340. In certain embodiments, the sealing layer 340 comprises a thin (e.g., 2 μm to 50 μm thick) layer of a substantially transparent material that interfaces with the focusing elements of the planar array of focusing elements 305 at its lower surface, and includes an upper surface that has less variation in curvature than the planar array of focusing elements 305 (e.g., by being smooth or having a surface with a larger radius of curvature of localized relief than the focusing elements).

[0028] As shown in the non-limiting example of FIG. 3A, in certain embodiments, the micro-optical security device 301 can be attached to a substrate 350, for example by an adhesive layer 330, to form a security document 360 (e.g., security document 105 of FIGS. 1A-1B). According to various embodiments, the substrate 350 can be a sheet of paper money or a polymeric substrate. According to some embodiments, the substrate 350 is a thin flexible sheet of biaxially oriented polypropylene (BOPP), a polymeric film. In various embodiments, the substrate 350 is a piece of synthetic paper material, such as Teslin®. According to some embodiments, the substrate 350 is a piece of polymeric card material, such as a polyethylene terephthalate (PET) blank of the type suitable for making credit cards and driver's licenses. In certain embodiments, the substrate 350 comprises the surface of a product, such as a bottle, a security document, or a high-value item, such as a smartphone or computer.

[0029] FIG. 3A shows an example of a micro-optical security device 301 formed in a structured graphic icon layer in which both the first graphic icon layer 320 and the second graphic icon layer 323 are constructed from a substantially transparent material, although embodiments according to the present disclosure are not so limited. While the technology for creating tools that emboss thin layers of photocurable material to create retention structures is mature and integrated with tools for mass producing micro-optical security devices, other techniques for creating graphic icons are possible and can be used in connection with the structured icon layer of a micro-optical security device having a phased icon layer according to various embodiments of the present disclosure. For example, in certain embodiments according to the present disclosure, digital tooling methods can be used to create either the array of graphic icons or the second array of graphic icons. The digital tooling used in the present disclosure is a method for creating a micro-optical security device having a phased icon layer. The present disclosure also encompasses a method of fabricating a component structure (e.g., a graphical icon or a light collecting element) of a security device by defining control logic for an electronic tool (e.g., a G-code file for a printer) used to form and place the component structure. As will be described in more detail with reference to the illustrative examples of Figures 5 and 8 of the present disclosure, according to certain embodiments, the graphical icons of either the first or second array of graphical icons can be fabricated as surface mount icons using digital tooling.

[0030] As a further example of digital tooling according to various embodiments of the present disclosure, one or more digitally controlled UV projectors can project patterns of ultraviolet light (e.g., as projected by a micro-optical security device). Output A mask file (corresponding to all or a portion of a composite image to be produced) can be projected onto a layer of uncured clear or colored photocurable material to produce a surface mount image icon. In certain embodiments, one or more UV projectors project patterned ultraviolet light through a layer of focusing elements. Output In various embodiments, instead of a digitally controlled UV projector, a pattern of UV light can be projected onto the uncured material by a rastered UV laser beam.

[0031] Referring to the non-limiting example of Figure 3B, in this particular example, the first graphic icon layer 320 has the same structure as Figure 3A, where the graphic icons are formed as areas of colored material disposed within spaces defined by retaining structures, which in this particular example comprise a layer of embossed and cured polymeric layer. According to a particular embodiment, the retaining structures in the first icon layer 320 are filled with a first colored light-curable liquid material and then directionally cured, whereby some of the light-curable material is cured to a solid state, while another portion of the light-curable material remains in a liquid state and can be removed from the retaining structures, such as by washing.

[0032] The term "directional curing" as used in this disclosure encompasses projecting structured or semi-structured light (e.g., collimated light) in a pattern based on the composite image provided by the micro-optical security device from a light source (or multiple light sources) located at a position associated with the intended viewing angle range of the composite image toward elements of the array of focusing elements such that the light is focused by the focusing elements on uncured material occupying a position in the image icon layer associated with the viewing angle. In other words, as explained, for example, through the illustrative examples of Figures 6A-6I of this disclosure, uncured material along the focal path of light from a light source associated with the viewing angle range and focused by the focusing elements of the array of focusing elements (e.g., the planar array of focusing elements 305 of Figure 3A) is cured, whereas uncured material at a position outside the focal path of the directional curing light focused by the focusing elements remains uncured.

[0033] According to certain embodiments, after the first color of uncured material is washed from the holding structure, further iterations of directionally curable material of other colors, or directionally curable material associated with different viewing angles, are performed. In the illustrative example of FIG. 3B, the final step in the formation of the first icon layer 320 is to fill the open spaces (e.g., areas not occupied by cured colored material) with a nearly transparent photocurable material that is little or completely invisible, at least to the human eye. According to certain embodiments, the layer of nearly transparent material can be detected using imaging equipment such as an electron microscope.

[0034] Referring to the non-limiting example of FIG. 3B, according to certain embodiments, an icon (e.g., surface mounted icon 326), i.e., a volume of hardened colored material of second icon layer 328, can be formed on the surface of first icon layer 320 by at least two methods described herein.

[0035] According to certain embodiments, one method of creating surface mounted icons on the surface of the first icon layer 320 involves first creating a set of retaining structures, such as by embossing a layer of photocurable polymer and then flood curing, to form the first icon layer 320. In various embodiments, in a second step, the retaining structures are further filled with uncured substantially clear photocurable material, the excess is doctor bladed off the retaining structures, and the material in the retaining structures is directionally cured using a pattern of directional curing light associated with a first viewing angle range to create an area in the first icon layer 320 of cured substantially clear material associated with the first viewing angle range. The uncured substantially clear photocurable material is then washed from the retaining structures, and the still available retaining structures are filled or coated with uncured photocurable material of a first color, the excess is doctor bladed off the retaining structures, and the remaining material is flood cured to complete the first icon layer 320 with a substantially flat outer surface distal to the planar array of light focusing elements 305. According to certain embodiments, similar to the second step of forming the first icon layer 320, a second color of uncured photocurable material is applied to the exterior surface and directionally cured using light associated with the first viewing angle range. Following directional curing, the second color of uncured photocurable material is washed from the exterior surface, leaving the surface mounted icons of the second icon layer 328 on the exterior surface of the first icon layer.

[0036] According to certain embodiments, another method of forming the second icon layer 328 of a surface mounted image icon includes creating the first icon layer 320 as described above and applying a layer of uncured photocurable material of a second color. The uncured photocurable material of the second color is directionally cured using patterned light at angles complementary to the first range of angles at which the material of the first color was cured. In this manner, a composite image of the colored material of the first color is projected through a light concentrating element. Output and a composite image of the second colored material is projected through the light collecting element. Output The separation between the angular ranges that are captured can be controlled.

[0037] FIG. 3C illustrates an example of a micro-optical security device 301 according to various embodiments of the present disclosure.

[0038] In addition to the illustrative example of FIG. 3B showing an example of a micro-optical security device according to the present disclosure in which a graphical icon layer including surface mounted icons is distal to an array of focusing elements relative to another graphical icon including a plurality of substantially transparent retaining structures, FIG. 3C shows an example of a micro-optical security device 301 in which a layer of surface mounted graphical icons is proximal to an array of focusing elements relative to an icon layer including substantially transparent retaining structures.

[0039] Referring to the non-limiting example of FIG. 3C, the first icon layer 327 includes a plurality of surface mounted image icons (including surface mounted image icon 329) formed on the optical spacer 310 by directionally curing a layer of uncured pigmented material of a first color with a pattern of light associated with a first composite image from a structured light source arranged to provide light over a first viewing angle range. In this illustrative example, following directional curing, the uncured material of the first color is removed, and optionally a subsequent set of surface mounted icons associated with a different color or different viewing angle is formed with directionally cured material of the first color or other colors. The uncured pigmented material is removed from the surface of the optical spacer 310, and a layer of substantially transparent material is applied to fill the spaces between the surface mounted image icons and form a flat surface on which the second image icon layer 323 can be formed as an image icon layer including a retaining structure. According to various embodiments, the layer of substantially transparent material is applied such that the substantially transparent material of the first icon layer 327 is integrated with the retaining structures of the second image icon layer 323.

[0040] In some embodiments, the support structures of the second graphical icon layer 323 are filled with uncured photocurable material of a second color, which is then doctored to remove excess uncured material. The uncured photocurable material of the second color is then applied to the support structures of the second graphical icon layer 323 by applying a pattern of light associated with the first viewing angle range. to wash away any uncured material of the second color. Depending on the number of layers specified for the icon layer stack 308, in some embodiments, the process for manufacturing the icon layer stack 308 can end here without further filling / curing steps.

[0041] 4A and 4B illustrate aspects of the contribution of stacked icon layers in a micro-optical security device (e.g., micro-optical security device 110 of FIGS. 1A-1B) according to various embodiments of the present disclosure. A micro-optical security device according to various embodiments of the present disclosure includes an icon layer stack. The icon layer stack is magnified by an array of focusing elements to produce a composite image. Output This composite image provides distinctive and eye-catching optical effects, including but not limited to multi-color composite images, with tightly controlled viewing angle ranges that each layer of the icon layer stack contributes to the composite image provided by the micro-optical security device. As noted elsewhere herein, micro-optical security devices according to some embodiments of the present disclosure include an icon stack having phase-aligned image icon layers.

[0042] Referring to the illustrative example of FIGS. 4A-4B, the image captured by the system over a first viewing angle range (Θ1→Θ2) and a second viewing angle range (Θ2→Θ3) is Output 3A) and a second image icon layer (e.g., second icon layer 328 in FIG. 3B) to the composite image. For ease of cross-reference, in the example of FIG. 4, the micro-optical security device presents the image to the observer. Output The resulting composite image corresponds to the composite image shown in the illustrative example of Figures 1A-1B. That is, when viewed at angles within a first viewing angle range, the micro-optical device displays a pair of ellipses of a first color on a background of a second color. OutputIn this non-limiting example, due to the phase alignment between the icons of the first image icon layer including the image icons of the first color and the icons of the second image icon layer including the image icons of the second color, the viewing angle transitions from the first viewing angle range to the second viewing angle range and the colored ellipse "switches off" and is replaced with the composite image of the second color.

[0043] As shown in FIGS. 4A-4B, when the micro-optical security device is viewed through a first viewing angle range (Θ1→Θ2), the light collecting elements of the device focus the area of ​​the first icon layer that contains a directional volume of hardenable material of a first color such that the area in which the first icon layer is visible in the composite image contributes a first ellipse 401a and a second ellipse 401b. Output According to some embodiments, uncured material of a first color in a first icon layer is directionally cured in a pattern associated with the ellipses 401a and 401b, and uncured substantially transparent material of a second icon layer is also directionally cured in a pattern associated with the ellipses 401a and 401b to exclude the second color pigmented material from the focal path associated with the first viewing angle range and ensure that corresponding regions 403a and 403b of the second icon layer do not cross-talk or otherwise interfere with the regions of the first icon layer that give rise to the ellipses 401a and 401b.

[0044] Similarly, for a second viewing angle range (Θ2→Θ3), in certain embodiments, an uncured, substantially transparent material is applied to a first layer and directionally cured from a light source associated with the second viewing angle range, thereby allowing the material to be illuminated by the micro-optical security device in the second viewing angle range. Output The second viewing angle range ensures that there is no contribution 405 of the first icon layer to the resulting composite image, i.e., in some embodiments, there is no colored material in the first icon layer at a location associated with the focal path of light entering and exiting the micro-optical security device along angles associated with the second viewing angle range.

[0045] Further, for a second viewing angle range (Θ2→Θ3), in various embodiments according to the present invention, a volume of uncured material of a second color is directionally cured with structured light provided by a light source associated with the second viewing angle range. Thus, in the second viewing angle range, the second image icon layer: A composite image 407 having components drawn only from the second image icon layer Output do.

[0046] Although FIGS. 4A-4B have been described with reference to a micro-optical security device that provides a single "flicker" effect created by directionally curing a first color of colorant material in a layer of an icon layer stack and directionally curing an uncolorant material in a second icon layer in the same viewing angle range, embodiments according to the present disclosure are not so limited. For example, in certain embodiments, techniques for controlling the phase matching of the icon layers and the viewing angle at which the colorant material in each layer of the image icon stack contributes to the composite can be applied to create various effects. For example, in certain embodiments, a portion of the composite image can exhibit a phase matching in which one color is "cut off" as soon as the viewing angle moves outside of the first viewing angle range, as described with reference to FIG. 4, while a different portion of the composite image can exhibit a slight phase shift in which the color changes with viewing angle. Furthermore, in certain embodiments, a phase matching between the colorant material of the first image icon layer and the colorant material of the second image icon layer can be achieved by directionally curing the uncured material of the second image icon layer in a viewing angle range that is complementary to the first viewing angle range used to directionally cure the colorant material of the first image icon layer, as described with reference to FIG. 3B.

[0047] 5A-5C illustrate multiple views of forming surface mounted graphic icons on cells of a micro-optical security device according to certain embodiments of the present disclosure.

[0048] To form a surface-mounted graphical icon in certain embodiments according to the present disclosure, structured light is projected onto the lens surface of the focusing elements of the planar array of focusing elements from a projection angle corresponding to a predetermined viewing angle range, and the structured light is focused by the focusing elements of the planar array of focusing elements onto an area of ​​uncured photocurable material that is within the footprint of the focusing elements of the planar array of focusing elements. The uncured photocurable material is then removed (e.g., using a spray wash) or chemically inactivated such that only the cured areas of the photocurable material are visible through the focusing elements at the predetermined viewing angle range. In this manner, a cured volume of colored material (e.g., a graphical icon) or substantially transparent material (e.g., to exclude colored material from locations that would interfere with the contribution of a colored icon in another layer of the icon layer stack) can be formed on the surface of the micro-optical security device.

[0049] 5A-5C, there are provided a side ( FIG. 5C ), bottom ( FIG. 5A ), and perspective ( FIG. 5B ) view of a refractive focusing element 501 disposed on a portion of an optical spacer 503. In this illustrative example, the lens surface 510 of the focusing element 501 defines a curved boundary between regions of different refractive index (e.g., a polymer having an index of refraction greater than 1 and air), which curved boundary directs curing light to a location within the footprint of the lens where the curing light cures a volume of a first color photocurable material to form a surface mounted image icon 521.

[0050] According to certain embodiments, the light collection element 501 is affixed to the optical spacer 503 and has a fixed relationship with respect to a surface of the optical spacer 503. In certain embodiments, the fixed relationship between the light collection element 501 and the surface of the optical spacer 503 is achieved by applying a layer of photocurable material to the optical spacer 503, embossing the layer of photocurable material to form a lens surface, and curing the material in situ. In some embodiments, the fixed relationship between the light collection element 501 and the surface of the optical spacer 503 is achieved by forming both the light collection element 501 and the optical spacer from a common layer of photocurable material and curing the formed layer to create an integrated light collection element-optical spacer combination.

[0051] The light-collecting element 501 collects an image icon by using the light-collecting element 501. Output 5, the light collecting element 501 may focus light with sufficient sharpness to achieve a desired focal length. 5A-5C, footprint 505 can be a three-dimensional area of ​​space such that icons of multiple layers of an icon layer stack can occupy space within footprint 505. In some embodiments, footprint 505 is coextensive with the perimeter of focusing element 501. In some implementations, footprint 505 is smaller than the perimeter of focusing element 501. In certain embodiments, footprint 505 represents an area larger than the perimeter of focusing element 501.

[0052] As shown in the illustrative examples of FIGS. 5A-5C, structured light (e.g., collimated light, light from a projector, or light passed through other arrays of focusing elements) associated with a composite image such as the cells shown in FIGS. 5A-5C is shown as Θ c5. The light is projected onto the lens surface of the light collection element 501 at an angle (or range of angles) associated with a predetermined viewing angle, shown as . The lens action of the light collection element 501 focuses the incident light along a focal path 520 within the footprint 505. By applying a layer of uncured photocurable pigmented (or substantially transparent photocurable) material to the bottom surface of the optical spacer 503 prior to application of structured light to the system, the portions of the photocurable material in the focal path 520 are cured by subsequent application of structured light, while the portions of the photocurable material outside the focal path 520 remain uncured and can be removed. Thus, a surface mounted image icon 521 can be formed on the surface within the footprint 505 of the light collection element 501.

[0053] Figures 6A-6I illustrate aspects of the structure of a micro-optical security device according to various embodiments of the present disclosure, and for ease of cross-referencing, elements common to two or more of Figures 6A-6I are similarly numbered.

[0054] Referring to the non-limiting example of FIG. 6A, a section of a planar array 601 of focusing elements of a micro-optical security device according to certain embodiments of the present disclosure is shown in the figure. In some embodiments as shown in the figure, the focusing elements of the planar array 601 of focusing elements are plano-convex microlenses. In some embodiments, the focusing elements of the planar array 601 of focusing elements are reflective focusing elements or different refractive structures (e.g., GRIN lenses). As shown in the figure, the focusing elements of the section of the planar array 601 of focusing elements have a local repeat period P1, which corresponds to the distance at which a pattern of similarly sized focusing elements is repeated in the section of the planar array 601 of focusing elements shown in the figure.

[0055] In a particular embodiment, the angle Θ a , or Θ aLight projected onto the planar array of focusing elements 601 over a range of viewing angles including is focused by the components of the planar array of focusing elements 603 and passes along multiple focal paths 610 (including, for example, focal path 611) through the optical spacer 605 and subsequent layers (e.g., the icon layer stack) of the micro-optical security device.

[0056] According to certain embodiments, the micro-optical security device includes an optical spacer 605 comprising a sheet of a substantially transparent material, such as a polyethylene or polyester film, on which the light focusing elements and icon layer stack (e.g., icon layer stack 308 of FIG. 3A) can be formed. According to some embodiments, the optical spacer 605 includes an intermediate layer of a substantially transparent photocurable polymer that is used to create other structures of the micro-optical security device, such as the planar array of light focusing elements 601. In various embodiments according to the present disclosure, the optical spacer 605 includes a section of biaxially oriented polypropylene (BOPP), polycarbonate, polyvinyl chloride (PVC), or polyethylene terephthalate (PET) film.

[0057] FIG. 6B illustrates a configuration of a micro-optical security device in accordance with certain embodiments of the present disclosure. 6B illustrates an embodiment of the micro-optical security device. Referring to the illustrative example of FIG. 6B, the figure shows an initial step in the creation of a first icon layer of an icon layer stack (e.g., icon layer stack 308 of FIG. 3A). According to a particular embodiment, a plurality of retention structures 607 are formed on the underside of an optical spacer 605. In this illustrative example, the plurality of retention structures 607 comprises a set of reliefs or recesses (shown in the figure as dotted fill) formed in a layer of substantially transparent material. As shown, the plurality of retention structures 607 have a local repeat period P2 in the section of the micro-optical security device shown in FIG. 6B. In a particular embodiment according to the invention, the first icon layer OutputThe local repeat period P2 of the support structures of a first icon layer of the icon layer stack varies across the icon layers such that components of the resulting composite image appear at different heights relative to the physical surface of the micro-optical security device.

[0058] According to some embodiments, a plurality of retention structures 607 are filled with uncured photocurable material 609 of a first color.

[0059] FIG. 6C illustrates aspects of the structure of a micro-optical security device according to certain embodiments of the present disclosure.

[0060] Referring to the non-limiting example of FIG. 6C, the first image icon layer of the image icon stack Output Structured light associated with components of a composite image to be formed is projected at the planar array of focusing elements 601 and passes through the optical spacer 605, the plurality of holding structures 607, and the volume of uncured photocurable material of the first color 609. As shown in this non-limiting example, the focal path of the light passing through the optical spacer 605 does not encompass all of the volume of uncured photocurable material of the first color. For example, a first portion 613a of the first color photocurable material 609 in the first holding structure 608 is outside the focal path 611, while a second portion 613b is within the focal path 611. According to some embodiments, the first portion 613a is not cured by the curing light passing along the focal path 611, while the second portion 613b within the focal path 611 is cured by the light passing along the focal path 611. Similarly, a third volume 613c of the first color photocurable material is entirely outside the focal path 611 and adjacent focal paths and remains uncured.

[0061] FIG. 6D illustrates aspects of the structure of a micro-optical security device according to various embodiments of the present disclosure.

[0062] As shown in this illustrative example, after directionally curing a first color of photocurable material with structured light from a first viewing angle range (e.g., light traveling along multiple focal paths 610 in FIG. 6C ), uncured material is removed from multiple retaining structures 607, leaving only volumes of the first color of cured material in the spaces of multiple retaining structures 613 that were within focal path 611. For example, the volumes of uncured material in portions 613a and 613c have been removed after directional curing, while a second portion 613b remains in place within multiple retaining structures 607.

[0063] FIG. 6E shows aspects of the structure of a micro-optical security device according to some embodiments of the present disclosure. Referring to the illustrative example of FIG. 6E, to help "confine" a volume of curable material (e.g., second portion 613b) to a location within the plurality of retaining structures 607 associated with a particular focal path (e.g., focal path 611 in FIG. 6C), the remaining unfilled regions of the retaining structures 607 are filled with a substantially transparent material (e.g., a UV-curable polymer suitable for embossing and curing to form a planar array of light-collecting elements 601). According to certain embodiments, the substantially transparent material added to the retaining structures to fill the spaces not filled by the directional curing material creates an interface region (e.g., interface region 615) between the substantially transparent retaining structures and the additional substantially transparent material. The interface region, including the boundary between these regions of substantially transparent material, is invisible to the human eye but is visible with an electron microscope.

[0064] In certain embodiments according to the present disclosure, construction of the first icon layer 620 is completed by adding a substantially transparent material to the unfilled areas of the plurality of retention structures 607, upon which second or higher icon layers of the icon layer stack may be formed.

[0065] FIG. 6F illustrates aspects of the structure of a micro-optical security device according to various embodiments of the present disclosure.

[0066] According to certain embodiments, a second layer of a multi-layer (i.e., two or more layers) icon layer stack is formed on a surface of the first icon layer 620 distal to the planar array of light collecting elements 601. As shown in the non-limiting example of Figure 6F, a second plurality of retention structures 631 are formed on a surface of the first icon layer 620 distal to the planar array of light collecting elements 601 (e.g., by embossing and subsequently curing a layer of substantially transparent UV curable material).

[0067] Referring to the non-limiting example of FIG. 6F, the recesses of the second plurality of retention structures 631 are filled with a volume of uncured, substantially transparent, photocurable material 633. The uncured, substantially transparent, photocurable material 633 is then directionally cured by light traveling through the structures of the icon layer stack along the plurality of focal paths 610, similar to the light used to cure the first color photocurable material of the first icon layer 620. As shown in the example of FIG. 6F, the volume of uncured, substantially transparent, photocurable material is cured in the second plurality of retention structures 631 at locations that coincide with the focal paths of the plurality of focal paths 610. For example, the photocurable material occupying the first volume 635a is cured by light traveling along the focal path 611, while the photocurable material occupying the location 635b outside the focal path 611 remains uncured.

[0068] FIG. 6G illustrates aspects of the structure of a micro-optical security device according to certain embodiments of the present disclosure. According to certain embodiments, the uncured substantially transparent photocurable material 633 in the second plurality of retention structures 631 is removed. Because the substantially transparent photocurable material is cured at locations associated with a first viewing angle range (e.g., at locations on the plurality of focal paths 610), additional material (e.g., photocurable material of a second color) can be added to the second plurality of retention structures only at locations associated with viewing angles outside of the focal paths of light passing through the icon layer stack along the first plurality of focal paths. In this manner, certain embodiments according to the present disclosure can achieve phase alignment between colored icons of different icon layers. In other words, in various embodiments according to the present disclosure, the volume of cured substantially transparent material in the second plurality of retention structures 631 occupies a location that may crosstalk with the cured volume of colored material (e.g., second portion 613b) in the first icon layer 620 if it is accessible to materials of other colors. However, the volume of hardened substantially transparent material (eg, first volume 635a) acts to exclude the colored material from the multiple focal paths 610.

[0069] FIG. 6H illustrates aspects of the structure of a micro-optical security device according to various embodiments of the present disclosure.

[0070] 6H , after a volume of uncured substantially transparent photocurable material 633 is directionally cured to remove uncured material outside of the plurality of focal paths 610, the unfilled spaces of the second plurality of retention structures 631 (i.e., locations associated with focal paths in viewing angle ranges other than the first viewing angle range) are filled with and cured with a volume of uncured material of a second color, resulting in volumes of cured material of the second color (e.g., first volume 637a and second volume 637b). In this manner, a second icon layer 640 is formed on the first icon layer 620.

[0071] As shown in the illustrative example of FIG. 6H, the volume of hardened material of the first color is determined by the micrometer shown in the figure. A small section of the optical security device has a local repeat period P C1and a volume of second colored hardened material is placed in the sliver of the micro-optical security device shown in FIG. 6H with a local repeat period P C2 In certain embodiments according to the present disclosure, the local repeat period of the hardened volumes of material of the first color and the hardened volumes of the second color may vary across the space of the micro-optical security device.

[0072] Although the micro-optical security devices according to various embodiments of the present disclosure have been described in Figures 6A-6H with respect to a system including only two layers and two colors, embodiments according to the present disclosure are not so limited and further embodiments in which the icon layer stack includes additional layers and each layer includes multiple colored volumes of cured material associated with multiple viewing angles are possible and within the intended scope of the present disclosure. In other words, the operational and structural aspects of the micro-optical security system of Figure 6H are scalable across multiple dimensions including the color of the icon, the number of icon layers, and the number of viewing angle ranges associated with a particular composite image.

[0073] FIG. 6I illustrates aspects of the structure of a micro-optical security device according to various embodiments of the present disclosure.

[0074] Referring to the non-limiting example of FIG. 6I, the structure shown in the example of FIG. 6H is again shown, but with multiple focal paths 610 superimposed on the diagram to help show how the hardened volume of a first color material in the first icon layer 620 is phase-aligned with the hardened volume of a second color material in the second icon layer 640.

[0075] In the illustrative example of FIGS. 6A-6I , a composite image in a first color flickers, or turns “on,” when the viewing angle falls within a viewing angle range associated with the multiple focal paths 610, and turns “off” when the viewing angle falls outside of the viewing angle range associated with the multiple focal paths 610, at which point a second composite image in a second color is captured by the micro-optical system. OutputThus, in certain embodiments according to the present disclosure, the on-off period of the first icon layer is phased with the off-on period of the second icon layer. Output The appearance of the composite image and the second icon layer 640 Output This synchrony between the disappearance of the resulting composite image is aided by the phasing of the volume of hardened material of a first color in the first layer with the volume of hardened material of a second color in the second layer. Figure 6I provides a non-limiting example of such phasing.

[0076] As shown in FIG. 6I , the second portion 613b of the first icon layer 620 is bounded by the left edge of the focal path 611 and is therefore projected by the planar array of concentrating elements 601 at a viewing angle within the first viewing angle range. Similarly, the first volume 637a of the second icon layer 640 abuts but does not extend beyond the left edge of the focal path 611. Thus, the first volume 637a is not projected by the planar array of concentrating elements at a viewing angle within the first viewing angle range. However, because the positions of the second portion 613b and the first volume 637a are aligned with the left edge of the focal path 611, moving into and out of the first viewing angle range is not projected by the first icon layer 620. Output The composite image and the second icon layer 640 Output Thus, a sharp transition occurs between the captured and synthesized image.

[0077] Those skilled in the art will understand that in certain embodiments of the present disclosure, the relative thicknesses of the focusing elements, icon stack, and optical spacers will differ from the illustrations of Figures 6A-6I, which are illustrated to show aspects of the icon structures of micro-optical security devices according to various embodiments of the present disclosure.

[0078] FIG. 7 illustrates aspects of the structure of a micro-optical security device according to various embodiments of the present disclosure.

[0079] Referring to the non-limiting example of FIG. 7, in certain embodiments according to the present disclosure, the substantially transparent retaining structures of one graphical icon layer can be integrated with a volume of substantially transparent material of another layer. In the illustrative example of FIG. 7, a section 700 of a micro-optical security device according to various embodiments of the present disclosure is shown. As shown, the section 700 includes a planar array of light focusing elements 701 (e.g., planar array of light focusing elements 601 of FIG. 6A), an optical spacer 703 (e.g., optical spacer 605 of FIG. 6A), a first icon layer 705, and a second icon layer 710. According to certain embodiments, the first icon layer 705 includes a plurality of retaining structures that retain volumes of directionally curable material of a first color (e.g., first volume 715a), which occupy positions within the retaining structures associated with a focal path of structured light passing through the section 700 from a light source associated with a first viewing angle or range of viewing angles. In some embodiments, to help achieve phase alignment between the colored material of the first icon layer 705 and the second image icon layer, a substantially transparent material is used to fill areas of the retention structures of the first icon layer 705 that are not filled with the first color directional curing material.

[0080] As described with reference to the non-limiting examples of Figures 6E and 6F of the present disclosure, in certain embodiments, areas of colored material are directionally cured, a substantially transparent material is applied and cured to fill the unfilled areas of the graphical icon layer, and in some embodiments, the retention structures of the next graphical icon layer are applied in three separate steps. However, in the illustrative example of Figure 7, the retention structures of the first icon layer 705 are created (e.g., by embossing and curing a substantially transparent photocurable polymer) and filled with uncured photocurable material of a first color. Excess photocurable material of the first color is doctor-bladed off from the retention structures and then directionally cured to create volumes of cured material of the first color in the first icon layer 705. In some embodiments, after the uncured material of the first color is washed off, a layer of uncured substantially transparent photocurable material is applied to fill the unfilled areas of the first icon layer 705 and embossed to form the retention structures of the second icon layer 710, which can then be cured. According to such an embodiment, the substantially transparent retaining structures of the second icon layer 710 are integrated with portions of the first icon layer 705 to form a single "square wave" shaped intermediate layer 720 spanning the first icon layer 705 and the second icon layer 710. In certain embodiments according to the present disclosure, the retaining structures of the second icon layer 710 are filled with uncured photocurable material of a second color. After the excess photocurable material of the second color is removed (e.g., by a doctor blade), the photocurable material of the second color is directionally cured with a patterned light associated with a second viewing angle range. Depending on the specifications of the micro-optical device (e.g., if only a two-layer icon layer stack is specified), the manufacturing process ends with washing the uncured material of the second color from the second icon layer 710. Alternatively, in some embodiments, a further "square wave" of substantially transparent material is integrated with the second icon layer 710 and provides a surface (e.g., a retaining structure, or a flat surface on which surface-mounted icons can be formed) for fabricating a third icon layer (not shown).

[0081] Depending on the embodiment, the substantially transparent region of one graphical icon layer and the retaining structure of another graphical icon layer may be integrated into a single intermediate layer, advantageously simplifying the manufacturing process and eliminating a portion of the interface area between the substantially transparent material of the first graphical icon layer 705 and the substantially transparent retaining structure of the second graphical icon layer 710.

[0082] Figures 8A and 8B show structural aspects of a micro-optical security device according to various embodiments of the present disclosure. For ease of cross-referencing, structures common to both Figures 8A and 8B are numbered the same.

[0083] Referring to the non-limiting example of FIG. 8A, a section 800 of a micro-optical security device according to various embodiments of the present disclosure is shown. According to certain embodiments, the security device includes a Section 800 includes a planar array of light focusing elements 801 (e.g., planar array of light focusing elements 307 of FIG. 3A), an optical spacer 803 (e.g., optical spacer 703 of FIG. 7), a first icon layer 805, and a second icon layer 810 (e.g., second icon layer 710 of FIG. 7). Section 800 of the micro-optical security device further includes an intermediate layer 820 (e.g., intermediate layer 720 of FIG. 7) in which the substantially transparent material of the first icon layer 805 is integrated with the substantially transparent retaining structures of the second icon layer 810.

[0084] As shown in the illustrative example of FIG. 8A, the first icon layer 805 does not include a retaining structure for positioning a substantially clear or colored light volume. Thus, an icon structure including a volume of a first color light-curable material (e.g., including first volume 815a) is a surface mount image icon. According to various embodiments, the icon structure of the first icon layer 805 is created by directional curing portions of a coated layer of uncured light-curable material of the first color (e.g., according to the method illustrated with reference to the example of FIGS. 5A-5B of this disclosure).

[0085] FIG. 8B illustrates further structural aspects of section 800 of the micro-optical security device of FIG. 8A by showing structured light of multiple focal paths 830 from one or more light sources projecting light onto section 800 at an angle (or range of angles) corresponding to a first viewing angle range. Referring to the non-limiting example of FIG. 8B, in certain embodiments according to the present disclosure, a surface mounted image icon (e.g., first volume 815a) can be phased with an icon formed on a holding structure. As shown in this non-limiting example, both the left edge of first volume 815a and the right edge of second volume 815b in second icon layer 810 are bounded by the left edge of focal path 831. Thus, at viewing angles within the first viewing angle range, the colored material of second icon layer 810 is colored by the micro-optical system. Output However, when the viewing angle moves out of the first viewing angle range associated with the multiple focal paths 830, for example due to phasing of the first volume 815a and the second volume 815b, the micro-optical system sharply "switches" from the projection material of the first icon layer 805 to the projection material of the second icon layer 810.

[0086] With reference to the illustrative example of FIG. 8B, certain embodiments according to the present disclosure provide flexibility in the design of micro-optical security systems. As previously described in this disclosure, the use of retaining structures as part of forming an icon layer is in many ways a mature technology that has been refined and is suitable for mass production of micro-optical security devices. At the same time, digital tooling and the creation of icon structures without the need to create molds for the retaining structures provides new possibilities, including, but not limited to, the ability to modify the icon structure of the final product without incurring retooling costs associated with creating new molds for the retaining structures, and "freeing up" areas of the icon layer for additional colored icon structures. As shown in the non-limiting example of FIG. 8B, the first volume 815a occupies the entire width of the focal path 831. In contrast, colored icons of similar width cannot be formed in the second icon layer 810, given the spacing of the retaining structures in this example. In certain embodiments, the micro-optical systems disclosed herein enable designers and manufacturers of micro-optical security devices to mix physical tooling (i.e., the use of mold holding structures) and digital tooling (i.e., the creation of surface mounted icons) at the layers of the image icon stack, enjoying both the flexibility of digital tooling and the convenience and accumulated expertise of working with physical tooling.

[0087] As with Figures 6A-6I and 7 of the present disclosure, in the illustrative examples of Figures 8A and 8B, the figures are drawn to emphasize the icon structure, and one skilled in the art will understand that the thickness of the icon layer stack in these figures relative to the remainder of the micro-optical device may differ from the thickness of a particular actual device.

[0088] FIG. 9 illustrates aspects of the structure of a micro-optical security device according to various embodiments of the present disclosure.

[0089] Referring to the illustrative example of FIG. 9, an example of a micro-optical security device 900 according to certain embodiments of the present disclosure is provided to illustrate the proportion of a two-layer icon layer stack relative to the remainder of the micro-optical security device 900.

[0090] According to certain embodiments, micro-optical security device 900 includes a planar array of light focusing elements 901 (e.g., planar array of light focusing elements 603 of FIG. 6A), an optical spacer 903 (e.g., optical spacer 310 of FIG. 3A), and an icon layer stack 905 comprising a first icon layer 907 and a second icon layer 909. In various embodiments, micro-optical security device 900 is configured such that the focusing elements of planar array of light focusing elements 901 focus light to a point in a plane 911 along the boundary between first icon layer 907 and second icon layer 909. In this manner, the components of each layer of icon layer stack 905 are focused by micro-optical security device 900. Output All the pixels appear equally "in focus" in the resulting composite image.

[0091] In various embodiments according to the present disclosure, the micro-optical security device 900 has an overall thickness 913, measured from the outside of the second icon layer 909 to the outside of the planar array of light collecting elements 901, of between 5 and 500 microns. In some embodiments, the micro-optical security device 900 has an overall thickness ranging from 10 to 200 microns. In some embodiments, the micro-optical security device 900 has a thickness of between 20 and 60 microns. Those skilled in the art will appreciate that in many embodiments, the overall thickness of the device reflects a tradeoff between various performance parameters of interest, including the maximum allowable thickness of the micro-optical security device 900, manufacturing concerns (e.g., the number of steps in the manufacturing process), and the end user's optical performance requirements (e.g., how detailed and dynamic the visual effect provided by the micro-optical security device 900 needs to be). Additionally, one of ordinary skill in the art will appreciate that the overall thickness of the micro-optical security device 900 will depend on a variety of factors, including, but not limited to, the number of layers in the icon layer stack 905, the pitch of the light focusing elements used to construct the planar array of light focusing elements 901, and the refractive index of the materials used to construct the planar array of light focusing elements 901, and that embodiments thicker or thinner than 5-500 microns are possible and within the intended scope of the present disclosure. According to a particular embodiment in which the overall thickness of the micro-optical security device 900 is approximately 40 microns, the two layer image icon stack 905 has a thickness of approximately 3 microns.

[0092] An example of a micro-optical security device according to certain embodiments of the present disclosure includes a security device including a planar array of microlenses configured to focus light along a plurality of focal paths associated with a viewing angle of the micro-optical security device, and an icon layer stack disposed along the plurality of focal paths. According to various embodiments, the icon layer stack includes a first icon layer comprising a volume of a first color of hardened material at a location along the focal path at a first viewing angle range and a volume of a substantially transparent material at a location outside the focal path at the first viewing angle range. The icon layer stack further includes a second icon layer disposed below the first icon layer relative to the planar array of microlenses. The second icon layer comprises a volume of a substantially transparent material at a location along the focal path at a first viewing angle range and a volume of a second color of hardened material at a location along the focal path at a second viewing angle range. At least one of the first icon layer or the second icon layer includes a plurality of substantially transparent retention structures.

[0093] As an example of a micro-optical security device according to certain embodiments of the present disclosure, a first The security device includes an icon layer including a plurality of substantially transparent retaining structures and a second icon layer including a second plurality of substantially transparent retaining structures.

[0094] An example of a micro-optical security device according to certain embodiments of the present disclosure includes a security device in which a first icon layer includes a plurality of substantially transparent retention structures and a volume of a second colored curable material includes surface mounted icons.

[0095] An example of a micro-optical security device according to certain embodiments of the present disclosure includes a security device in which a second icon layer includes a plurality of substantially transparent retention structures and a volume of a first colored curable material includes a surface mounted icon.

[0096] An example of a micro-optical security device according to certain embodiments of the present disclosure includes a security device in which the second color contrasts with the first color.

[0097] Examples of micro-optical security devices according to certain embodiments of the present disclosure include security devices in which the second color does not contrast with the first color.

[0098] An example of a micro-optical security device according to certain embodiments of the present disclosure includes a security device that further includes an optical spacer disposed between the planar array of microlenses and the first icon layer.

[0099] An example of a micro-optical security device according to certain embodiments of the present disclosure includes a security device in which a first icon layer includes a plurality of substantially transparent retention structures and a substantially transparent cured material at a location outside the focal path of a first viewing angle range is integrated with a second icon layer.

[0100] As an example of a micro-optical security device according to certain embodiments of the present disclosure, the planar array of microlenses includes an area in which the microlenses of the planar array of microlenses are arranged with a first local repeat period, the first icon layer includes a second area in which volumes of hardened material of a first color are arranged with a second local repeat period, and the ratio of the first local repeat period to the second local repeat period is such that the microlenses display a composite image consisting of portions of the volumes of hardened material of the first color over a first viewing angle range. Output Examples of security devices that are similar to this include:

[0101] As an example of a micro-optical security device according to certain embodiments of the present disclosure, the second icon layer includes a third region in which volumes of hardened material of a second color are arranged in a third local repeat period, and the ratio of the third local repeat period to the first local repeat period is such that the microlenses display a composite image consisting of portions of the volumes of hardened material of the second color in a second viewing angle range. Output Examples of security devices that are similar to this include:

[0102] An example of a micro-optical security device according to certain embodiments of the present disclosure is a security device in which a first range of viewing angles includes an angle corresponding to a vector perpendicular to the face of the micro-optical security device (eg, top dead center).

[0103] An example of a micro-optical security device according to certain embodiments of the present disclosure includes a security device that further includes one or more interface regions disposed between a substantially transparent retention structure and one or more volumes of substantially transparent material at a location outside the focal path of the first viewing angle range.

[0104] As an example of a micro-optical security device according to certain embodiments of the present disclosure, a first viewing angle range is contiguous with a second viewing angle range, and the position along the focal path of the first viewing angle range is A composite image of a portion of the volume of a first color of hardenable material is generated at the Output An example of such an application is a security device in which the composite image becomes invisible when the viewing angle transitions from a first viewing angle range to a second viewing angle range.

[0105] An example of a micro-optical security device according to certain embodiments of the present disclosure includes a micro-optical security device including a planar array of focusing elements configured to focus light along multiple focal paths associated with viewing angles of the micro-optical security device, and an icon layer stack disposed along the multiple focal paths, the icon layer stack including a first icon layer including a volume of directional curing material of a first color associated with a first viewing angle range of the micro-optical security device, and a second icon layer including a volume of curing material of a second color at a location along the focal path of a second viewing angle range, at least one of the first icon layer or the second icon layer including a plurality of substantially transparent retention structures, and the second viewing angle range does not occupy the same area as the first viewing angle range.

[0106] An example of a micro-optical security device according to certain embodiments of the present disclosure includes a micro-optical security device where the second icon layer further includes a volume of directionally hardened substantially transparent material associated with a first viewing angle range of the micro-optical security device.

[0107] An example of a micro-optical security device according to certain embodiments of the present disclosure includes a micro-optical security device in which the second range of viewing angles is complementary to the first range of viewing angles.

[0108] An example of a micro-optical security device according to certain embodiments of the present disclosure includes a micro-optical security device in which the second viewing angle range is adjacent to the first viewing angle range.

[0109] An example of a micro-optical security device according to certain embodiments of the present disclosure includes a micro-optical security device in which the second viewing angle range overlaps with the first viewing angle range.

[0110] Examples of micro-optical security devices according to certain embodiments of the present disclosure include security devices that further include an optical spacer in contact with at least one of the planar array of light focusing elements or the icon layer stack.

[0111] Examples of micro-optical security devices according to certain embodiments of the present disclosure include security devices in which the focusing elements of the planar array of focusing elements are reflective focusing elements.

[0112] Examples of micro-optical security devices according to certain embodiments of the present disclosure include security devices in which the focusing elements of the planar array of focusing elements are refractive focusing elements.

[0113] An example of a micro-optical security device according to certain embodiments of the present disclosure includes a security device in which the second color contrasts with the first color.

[0114] Examples of micro-optical security devices according to certain embodiments of the present disclosure include security devices in which the second color does not contrast with the first color.

[0115] As an example of a micro-optical security device according to certain embodiments of the present disclosure, the planar array of light focusing elements includes an area in which the focusing elements of the planar array of light focusing elements are arranged with a first local repeating period, and the first icon layer includes an area in which volumes of a first colored hardened material are arranged with a second local repeating period. a ratio of the first local repeat period to the second local repeat period such that the light collecting elements form a composite image of a portion of the volume of the first colored curable material over a first viewing angle range; Output Examples of security devices that are similar to this include:

[0116] As an example of a micro-optical security device according to certain embodiments of the present disclosure, the second icon layer includes a third region in which volumes of hardenable material of a second color are arranged in a third local repeat period, and a ratio of the third local repeat period to the first local repeat period is such that the light collecting elements form a composite image of the portions of the volumes of hardenable material of the second color in a second viewing angle range. Output Examples of security devices that are similar to this include:

[0117] An example of a micro-optical security device according to certain embodiments of the present disclosure includes a security device in which the first range of viewing angles includes the top dead center.

[0118] An example of a micro-optical security device according to certain embodiments of the present disclosure includes a security device that further includes one or more interface regions disposed between a substantially transparent retention structure and one or more volumes of substantially transparent material at a location outside the focal path of the first viewing angle range.

[0119] As an example of a micro-optical security device according to certain embodiments of the present disclosure, a first viewing angle range is contiguous with a second viewing angle range, and a composite image is displayed comprising a portion of a volume of a first color directionally curable material. Output An example of such an application is a security device in which the composite image becomes invisible when the viewing angle transitions from a first viewing angle range to a second viewing angle range.

[0120] Nothing in this application should be construed as implying that a particular element, step, or function is an essential element, step, or function that must be included in the scope of the claim. Moreover, the claims are not intended to invoke 35 U.S.C. 112(f) unless the phrase "means for" is followed by a participle.

Claims

1. A micro-optical security device (105), comprising: a planar array (305) of microlenses configured to focus light along a number of focal paths (610) associated with a viewing angle of said micro-optical security device; an icon layer stack (905) arranged along said plurality of focal paths; the icon layer stack comprising: a volume (613b) of curable material of the first color at a position along the focal path at a given viewing angle within the first viewing angle range; a volume of transparent material at a location outside the focal path at a given viewing angle within the first viewing angle range; and A first icon layer (620) comprising: a second icon layer (640) disposed below the first icon layer relative to the planar array of microlenses, a volume of transparent, curable material at a location along the focal path at a predetermined viewing angle within the first viewing angle range; and a volume (637a) of curable material of a second color at a location along the focal path at a given viewing angle within a second viewing angle range; and The second icon layer (640) further comprises: Including, At least one of the first icon layer or the second icon layer includes a plurality of transparent retaining structures; the planar array of microlenses includes an area in which microlenses of the planar array of microlenses are arranged in a first local repeating period; the first icon layer includes a second region in which the volumes of hardened material of the first color are arranged in a second local repeating period; a ratio of the first local repeat period to the second local repeat period such that the microlenses project a composite image of the portion of the volume of the first color curable material in the first viewing angle range. Micro-optical security device.

2. the first icon layer includes the plurality of transparent retaining structures; the second icon layer includes a second plurality of transparent retaining structures; The micro-optical security device of claim 1 .

3. the first icon layer includes the plurality of transparent retaining structures; the volume of the second colored curable material includes a surface mount icon; The micro-optical security device of claim 1 .

4. the second icon layer includes the plurality of transparent retaining structures; the volume of curable material of the first color includes a surface mount icon (815a); The micro-optical security device of claim 1 .

5. the second color contrasts with the first color; The micro-optical security device of claim 1 .

6. the second color does not contrast with the first color; The micro-optical security device of claim 1 .

7. further comprising an optical spacer (903) disposed between the planar array of microlenses and the first icon layer; The micro-optical security device of claim 1 .

8. the first icon layer includes the plurality of transparent retaining structures; the transparent curable material at locations outside the focal path at predetermined viewing angles within the first viewing angle range is integral with the second icon layer; The micro-optical security device of claim 1 .

9. the second icon layer includes a third region in which the volumes of hardenable material of the second color are arranged in a third local repeating period; 2. The micro-optical security device of claim 1, wherein a ratio of the first local repeat period to the third local repeat period is such that the microlens emits a composite image consisting of a portion of the volume of the second colored cured material in the second viewing angle range.

10. The micro-optical security device of claim 1 , wherein the first viewing angle range includes top dead center.

11. The micro-optical security device of claim 1, further comprising one or more interface regions disposed between the transparent retention structure and one or more of the volumes of the transparent material at locations outside a focal path at a predetermined viewing angle within the first viewing angle range.

12. the first viewing angle range is contiguous with the second viewing angle range; emit a composite image of the portion of the volume of the first color of curable material at a location along a focal path at a predetermined viewing angle within the first viewing angle range, the composite image becoming invisible as the viewing angle transitions from the first viewing angle range to the second viewing angle range. The micro-optical security device of claim 1 .

13. 1. A micro-optical security device, comprising: a planar array (305) of focusing elements configured to focus light along a plurality of focal paths (610) associated with a viewing angle of said micro-optical security device; an icon layer stack (905) arranged along said plurality of focal paths; the icon layer stack comprising: a first icon layer (620) including a volume of directionally curable material of a first color associated with a first viewing angle range of said micro-optical security device; a second icon layer (640) comprising volumes of a second colored curable material at locations along the focal path at predetermined viewing angles within a second viewing angle range; Including, At least one of the first icon layer or the second icon layer includes a plurality of transparent retaining structures; the second viewing angle range does not occupy the same area as the first viewing angle range; Micro-optical security device.

14. 14. The micro-optical security device of claim 13, wherein said second icon layer further comprises a volume of directionally hardened transparent material associated with said first viewing angle range of said micro-optical security device.

15. The micro-optical security device of claim 13, wherein said second viewing angle range is complementary to said first viewing angle range.

16. The micro optical security device of claim 13, wherein the second viewing angle range is adjacent to the first viewing angle range.

17. The micro optical security device of claim 13, wherein the second viewing angle range overlaps with the first viewing angle range.

18. 14. The micro-optical security device of claim 13, further comprising an optical spacer contacting at least one of said planar array of light focusing elements or said icon layer stack.

19. The micro-optical security device of claim 13, wherein the focusing elements of said planar array of focusing elements are reflective focusing elements.

20. The micro-optical security device of claim 13, wherein the focusing elements of said planar array of focusing elements are refractive focusing elements.

21. The micro-optical security device of claim 13, wherein said second color contrasts with said first color.

22. 14. The micro-optical security device of claim 13, wherein said second color does not contrast with said first color.

23. the first icon layer includes the plurality of transparent retaining structures; the second icon layer includes a second plurality of transparent retaining structures; 14. The micro-optical security device of claim 13.

24. the first icon layer includes the plurality of transparent retaining structures; the volume of the second colored curable material includes a surface mount icon; 14. The micro-optical security device of claim 13.

25. the second icon layer includes the plurality of transparent retaining structures; the volume of the first colored curable material includes a surface mount icon; 14. The micro-optical security device of claim 13.

26. the planar array of focusing elements includes a region in which focusing elements of the planar array of focusing elements are arranged with a first local repeating period; the first icon layer includes a second region in which the volumes of hardened material of the first color are arranged in a second local repeating period; The micro-optical security device of claim 13, wherein the ratio of the first local repeat period to the second local repeat period is such that the focusing element emits a composite image consisting of a portion of the volume of the first colored hardened material in the first viewing angle range.

27. the second icon layer includes a third region in which the volumes of hardenable material of the second color are arranged in a third local repeating period; 27. The micro-optical security device of claim 26, wherein the ratio of the first local repeat period to the third local repeat period is such that the focusing element emits a composite image consisting of a portion of the volume of the second colored hardened material in a second viewing angle range.

28. The micro-optical security device of claim 13, wherein the first viewing angle range includes top dead center.

29. The micro-optical security device of claim 13, further comprising one or more interface regions disposed between the transparent retention structure and one or more of the volumes of the transparent material at locations outside a focal path at a predetermined viewing angle within the first viewing angle range.

30. the first viewing angle range is contiguous with the second viewing angle range; emit a composite image of the volume of the first color directionally curable material, the composite image disappearing as a viewing angle transitions from the first viewing angle range to the second viewing angle range.

14. The micro-optical security device of claim 13.

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