Micro-optic security device having phase aligned image layer

Abstract

To provide a micro-optic security device having a phase aligned image layer.SOLUTION: A micro-optic security device includes a planar array of microlenses configured to focus light along multiple focal paths (610) associated with a viewing angle. The micro-optic security device further includes an icon layer stack disposed along multiple focal paths. The icon layer stack includes a first icon layer (620) having a volume of cured material of a first color (613b) and a volume of substantially transparent material at locations outside of focal paths of the first range of viewing angle. Also, the icon layer stack includes a second icon layer (640) having a volume of substantially transparent cured material at locations along focal paths of the first range of viewing angle, and a volume of cured material of a second color (637a) at locations along focal paths of a second range of viewing angle.SELECTED DRAWING: Figure 6I

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 a phase-aligned image layer. [Background technology]

[0002] Depending on their configuration and incorporation into end products, micro-optical security devices with dynamic, difficult-to-replicate appearances can significantly improve the counterfeit resistance of security documents, such as currency, passports, and other documents requiring 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 it, and the ability to mass-produce the device. For example, a micro-optical security device that produces an obscured or visually uninteresting visual effect is unlikely to be noticed by most end users, and, by implication, its absence is likely to be similarly unnoticed by end users. In such cases, a counterfeit document without the 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 it can be mass-produced, thereby lowering its price and facilitating widespread adoption. Pushing the envelope to achieve more distinctive visual effects that are beyond the reach of counterfeiters, yet can 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 a phase-aligned image layer. [Means for solving the problem]

[0004] In a first embodiment, a micro-optical security device includes a planar array of microlenses configured to focus light along multiple focal paths associated with the viewing angles of the micro-optical security device. The micro-optical security device further includes an icon layer stack disposed along the multiple focal paths. The icon layer stack includes a first icon layer comprising volumes of curable material of a first color at locations along the focal path within a first viewing angle range and volumes of substantially transparent material at locations outside the focal path within 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 comprises volumes of substantially transparent curable material at locations along the focal path within the first viewing angle range and volumes of curable material of a second color at locations along the focal path within the 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, a micro-optical security device includes a planar array of light-collecting elements configured to focus light along multiple focal paths associated with the viewing angles of the micro-optical security device. The micro-optical security device further includes an icon layer stack disposed along the multiple focal paths. The icon layer stack includes a first icon layer comprising a volume of directional curing material of a first color associated with a first viewing angle range of the micro-optical security device. The icon layer stack also includes a second icon layer comprising a volume of directional curing material of a second color at a location along the focal path for 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. 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 "couple" and its derivatives refer to any direct or indirect communication between two or more elements, regardless of whether they are in physical contact with one another. The terms "comprise" and "comprise," and their derivatives, refer to an open-ended inclusion. The term "or" is inclusive and / or. The phrase "related to" and its derivatives refer to including, contained within, interconnected with, containing, housed within, connected to, coupled to, communicable with, cooperate with, sandwiched between, juxtaposed with, adjacent to, coupled to, having, having a characteristic of, having a relationship with, 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 that only one item in the list may be required. For example, "at least one of A, B, and C" includes any of the following combinations: 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 skilled in the art will understand that in many, if not most, cases such definitions apply to previous and future uses of the words and phrases so defined.

[0009] For a more complete understanding of the present disclosure and its advantages, 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 explanation 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] 10 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] 10 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] 10A-10C illustrate examples of how surface mounted image icons may be formed from multiple perspectives, according to some embodiments of the present disclosure. [Figure 5B] 10A-10C illustrate examples of how surface mounted image icons may be formed from multiple perspectives, according to some embodiments of the present disclosure. [Figure 5C] 10A-10C illustrate examples of how surface mounted image icons may be formed from multiple perspectives, 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 INVENTION

[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 understand 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, and the present disclosure is intended to cover such changes and modifications that fall within the scope of the claims.

[0013] 1A and 1B illustrate 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, 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 are provided. According to various embodiments, security document 105 is a passport, currency, ID card, or other document that would benefit from a reliable visual indicator of authenticity. In the non-limiting example of FIGS. 1A-1B, micro-optical security device 110 includes a layer of light-gathering elements (e.g., microlenses) and an image stack including regions where two or more layers of image icons are phase-aligned. 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 in a first icon layer occupy positions in the first icon layer associated with focal paths for a first range of viewing angles, colored icons in a second icon layer occupy positions in the second icon layer associated with focal paths for a second range of viewing angles, colored icons in the first icon layer occupy positions in the first icon layer associated with focal paths outside the second range of viewing angles, and colored icons in the second icon layer occupy positions in the second layer associated with focal paths outside the first range of viewing angles. Specifically, when colored image icons are phased according to certain embodiments of the present disclosure, crosstalk, i.e., the simultaneous projection by a light collection element of colored image icons from two or more layers of an icon stack within a given range of viewing angles, can be substantially controlled and incorporated or eliminated as a design feature of the composite image projected by the micro-optical security device. According to certain embodiments of the present disclosure, controlling the occurrence of crosstalk between image icon layers facilitates the creation of micro-optical security devices that are improved along at least three dimensions along which performance of micro-optical security devices is measured.Specifically, by using phase alignment between image icons as a controllable design parameter, a sharper transition can be achieved between a multicolor composite image projected by a micro-optical security device over a first range of viewing angles and a composite image projected by a micro-optical security device over a second range of viewing angles. For example, embodiments according to the present disclosure can produce both a multicolor "flicker" effect, in which the composite image includes colored components that rapidly appear and disappear, and an effect in which colored regions of the composite image gradually move or change. Incorporating a multicolor "flicker" effect in addition to a gradually evolving color effect can provide a composite image that is eye-catching and attracts the viewer's attention. Furthermore, achieving phase alignment between the icon layers presents additional manufacturing challenges, implicitly making such devices more difficult for malicious actors to counterfeit. Third, certain embodiments according to the present disclosure can be manufactured using structured icon tooling (e.g., molds for embossing retention structures into layers of UV-curable polymer) and thus can currently be manufactured in large quantities.

[0015] When security document 105 is oriented so that the surface of the document occupies values ​​within a first viewing angle range Θ1 → Θ2 of coordinate system 115, as shown in first view 101, the icon structure and light collection elements of micro-optical security device 110 project a first two-color composite image 120 comprising a pair of ellipses of a first color within a polygonal field of a contrasting second color. As shown in the example of FIGS. 1A-1B, an observer tilts security document 105 through the first viewing angle range Θ1 → Θ2 until it enters a second viewing angle range Θ2 → Θ3, as shown in second view 151. In this example, the pair of ellipses is "interrupted" as the document moves from the first viewing angle range to the second viewing angle range, and the micro-optical system projects a second composite image, which in this illustrative example is a polygonal field of a contrasting second color, as shown in second view 151. Thus, micro-optical systems according to various embodiments of the present disclosure provide sharp transitions from one composite image to another as the device moves through 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 limited thereto, 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] The illustrative example of Figures 2A-B shows a first view 201 (shown in Figure 2A) and a second view 251 (shown in Figure 2B) of a micro-optical cell 200. 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 focusing element's focal area (also called its "footprint"). 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 support structures (e.g., support structure 211) within which an icon 213 of a colored material can be formed. The angle Θa at which the icon 213 is projected by the focusing element 205 to the viewer depends on its position within the footprint of the focusing element 205 (indicated by left and right boundaries 217a and 217b). As shown in connection with second view 251, a small shift (movement) 253 in the icon's position relative to the footprint of the focusing element 205 results in a change in the angle Θb at which the icon 213 is projected to the viewer. When manufactured in large quantities, some variation in the alignment of the support structures of the image icon layer 210 relative to the footprint of the focusing element is generally inevitable. 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 relative to the light collection elements may be apparent to the end user as variations in the range of angles at which a particular composite image is projected to the viewer. In many applications utilizing a single icon layer, such variations in the viewing angles at which a particular composite image is displayed are 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 with two or more stacked icon layers, such alignment variations lead to variations in the degree to which the colored icons of the icon layers are aligned with each other. These variations in alignment between the icon layers may manifest as unclear or "soft" changes in the composite image projected by the micro-optical security device over varying viewing angle ranges. For example, instead of a sharp switch from projecting first composite image 120 to second composite image 155 as described with reference to the non-limiting example of Figures 1A-1B, the micro-optical system may simultaneously project components of the first and second composite images over an intermediate range of angles. Depending on the extent and nature of the alignment problems between the layers, the projected image may variously appear as a gradual color-changing effect (as opposed to a defined "on-off" or "flicker" effect), a blurring of two or more colors, or a visual cacophony in which different colors from different icon layers are projected at angles unrelated to each other.

[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. For convenience, structures common to one or more of Figures 3A-C are numbered identically.

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

[0023] Referring to the non-limiting example of Figure 3A, micro-optical security device 301, at a basic level, includes a planar array of light collection elements 305 (e.g., including light collection element 307) and an icon layer stack 308 with a first icon layer 320 (e.g., including image icon 321) and a second image icon layer 323 (e.g., including image icon 324). According to various embodiments, each light collection element of planar array of light collection elements 305 has a footprint. Furthermore, planar array of light collection elements includes one or more cells in which one or more image icons of the arrangement in first icon layer 320 or second image icon layer 323 are disposed. Furthermore, icon layer stack 308 includes at least one region in which the colored image icons of first icon layer 320 and the colored image icons of second image icon layer 323 are phase-aligned. In certain embodiments, the locations of the graphical icons (e.g., graphical icon 321 or 324) correspond to locations within a support structure made of a substantially transparent material, such as a UV-curable resin, that is embossed and then cured to form a graphical icon layer with structures such as voids, posts, or mesas onto which colored material can be selectively deposited. According to some embodiments, the individual focusing elements of 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 micro-optical security device 301 repeats within a region of interest. As an example, the focusing elements of 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, for example, a local repeat period of 51 icons per mm in one portion of the micro-optical security device 301 and a local repeat period of 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 structures, the appearance of the composite image of the icon structures projected by the light collecting elements can be adjusted.For example, the apparent position 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, causing the composite image to appear to float above or be located 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 micro-lenses) 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 ranging from 1.35 to 2.05 in some embodiments and have diameters ranging from 5 μm to 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 to 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 , first image icon layer 320 includes a set of image icons (including image icon 321) arranged at locations within the footprint of focusing elements of planar array of focusing elements 305 associated with a range of directional curing angles. According to various embodiments, individual image icons in first icon layer 320 include regions of directionally cured material in partial or all spaces defined by retaining structures in a 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) 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 arrays of graphical icons of the icon layer stack 308 in or around the focal planes of the focusing elements of the planar array of focusing elements 305. In certain embodiments according to the present disclosure, the optical spacer 310 includes a fabrication substrate onto 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 focusing elements of the planar array of focusing elements 305) between the focusing elements and the icon layer stack 308.

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

[0028] As shown in the non-limiting example of FIG. 3A , in certain embodiments, micro-optical security device 301 can be attached to substrate 350, for example, by adhesive layer 330, to form security document 360 (e.g., security document 105 of FIGS. 1A-1B ). According to various embodiments, substrate 350 can be a sheet of banknote or a polymer substrate. According to some embodiments, substrate 350 is a thin, flexible sheet of biaxially oriented polypropylene (BOPP), a polymer film. In various embodiments, substrate 350 is a piece of synthetic paper material such as Teslin®. According to some embodiments, substrate 350 is a piece of polymer card material, such as a polyethylene terephthalate (PET) blank of the type suitable for making credit cards and driver's licenses. In certain embodiments, 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] While Figure 3A illustrates an example of a micro-optical security device 301 formed within a structured graphic icon layer in which both the first icon layer 320 and the second graphic icon layer 323 are constructed from a substantially transparent material, embodiments according to the present disclosure are not limited thereto. While the technology for creating tools that emboss thin layers of photocurable material to create retention structures is mature and integrated into 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. Digital tooling, as used in this disclosure, encompasses methods of manufacturing the constituent structures (e.g., graphic icons or light-collecting elements) of a micro-optical security device by defining the control logic of an electronic tool (e.g., a G-code file for a printer) used to form and position the constituent structures. 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 image icons in either the first or second array of image icons can be fabricated as surface-mounted 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 a pattern of ultraviolet light (e.g., a mask file corresponding to all or a portion of a composite image projected by a micro-optical security device) onto a layer of uncured clear or colored photocurable material to create a surface-mounted image icon. In certain embodiments, one or more UV projectors project the patterned ultraviolet light through a layer of focusing elements, thereby directionally curing portions of the uncured photocurable material. In various embodiments, instead of a digitally controlled UV projector, the pattern of UV light can be projected onto the uncured material by a rasterized UV laser beam.

[0031] 3B, in this particular example, the first graphic icon layer 320 has the same structure as in FIG. 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 material. According to certain embodiments, 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 hardens to a solid state, while other portions of the light-curable material remain in a liquid state and can be removed from the retaining structures, such as by washing.

[0032] As used in this disclosure, the term "directional curing" 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) positioned at a location associated with the intended viewing angle range of the composite image toward elements of the array of focusing elements, such that the focusing elements focus the light on uncured material occupying locations within 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 focusing elements of the array of focusing elements (e.g., planar array of focusing elements 305 of Figure 3A) is cured, while uncured material at locations outside the focal path of the directional curing light focused by the focusing elements remains uncured.

[0033] According to certain embodiments, after the uncured material of the first color 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 Figure 3B, the final step in forming the first icon layer 320 is to fill the open spaces (e.g., areas not occupied by cured colored material) with a substantially transparent photo-curable material that is little or completely invisible, at least to the human eye. According to certain embodiments, the layer of substantially 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 for creating surface-mounted icons on the surface of the first icon layer 320 involves first creating a set of support structures, such as by embossing and then flood-curing a layer of photocurable polymer, to form the first icon layer 320. In various embodiments, a second step further fills the support structures with uncured, substantially transparent photocurable material, doctor-blades off the excess, and directionally cures the material in the support structures using a pattern of directional curing light associated with a first range of viewing angles to create regions in the first icon layer 320 of cured, substantially transparent material associated with the first range of viewing angles. The uncured, substantially transparent photocurable material is then washed from the support structures, and the remaining support structures are filled or coated with uncured, photocurable material of a first color, doctor-blades off the excess, and flood-cures the remaining material, completing the first icon layer 320 with a substantially flat outer surface distal to the planar array of light-collecting elements 305. According to certain embodiments, similar to the second step of forming the first icon layer 320, a second color of uncured photo-curable 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 photo-curable 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 for forming the second icon layer 328 of a surface-mounted image icon includes fabricating 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 an angle complementary to the first range of angles at which the first color material was cured. In this manner, the separation between the range of angles at which the composite image of the first colored material is projected through the light-collecting element and the range of angles at which the composite image of the second colored material is projected through the light-collecting element 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 , which shows 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 holding 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 holding 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 using a pattern of light associated with a first composite image from a structured light source positioned 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 different colors or different viewing angles 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 upon which the second image icon layer 323 can be formed as an image icon layer including the retaining structures. 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 image icon layer 323 are filled with a second color of uncured photocurable material, which is then doctor bladed to remove excess uncured material. The second color of uncured photocurable material is directionally cured with a pattern of light associated with the first viewing angle range, washing away the second color of uncured material. 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. The micro-optical security device according to various embodiments of the present disclosure includes an icon layer stack that is magnified by an array of light-collecting elements to project a composite image that provides distinctive and eye-catching optical effects, including but not limited to multi-color composite images, with a tightly controlled range of viewing angles that each layer of the icon layer stack contributes to the composite image provided by the micro-optical security device. As discussed elsewhere herein, the micro-optical security device according to some embodiments of the present disclosure includes an icon stack with phase-aligned image icon layers.

[0042] Referring to the illustrative example of Figures 4A-4B, the contributions of a first image icon layer (e.g., first icon layer 320 of Figure 3A) and a second image icon layer (e.g., second icon layer 328 of Figure 3B) to a composite image projected by a system over a first viewing angle range (Θ1 → Θ2) and a second viewing angle range (Θ2 → Θ3) are illustrated. For ease of cross-reference, the composite image projected to a viewer by the micro-optical security device in the example of Figure 4 corresponds to the composite image shown in the illustrative example of Figures 1A-1B. That is, when viewed at angles within the first viewing angle range, the micro-optical device projects a pair of ellipses of a first color onto a background of a second color. In this non-limiting example, due to the phase alignment between the icons in the first image icon layer including the image icons of the first color and the icons in 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 oval "switches off" and is replaced with a composite image of the second color.

[0043] 4A-4B, when the micro-optical security device is viewed through a first viewing angle range (Θ1 → Θ2), the device's light-collecting elements project regions of the first icon layer including directional volumes of cured material of a first color such that the first icon layer contributes visible areas in the composite image as first ellipses 401 a and second ellipses 401 b. According to some embodiments, uncured material of the first color in the first icon layer is directionally cured in a pattern associated with ellipses 401 a and 401 b, and uncured substantially transparent material of the second icon layer is also directionally cured in a pattern associated with ellipses 401 a and 401 b, excluding the colored material of the second color from the focal path associated with the first viewing angle range and ensuring that corresponding regions 403 a and 403 b of the second icon layer do not crosstalk or otherwise interfere with the regions of the first icon layer that result in ellipses 401 a and 401 b.

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

[0045] Additionally, for a second viewing angle range (Θ→Θ), various embodiments according to the present invention directionally cure a volume of uncured material of a second color 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 projects a composite image 407 having components rendered solely from the second image icon layer.

[0046] While FIGS. 4A-4B are 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 uncolorant material in a second icon layer over the same viewing angle range, embodiments according to the present disclosure are not limited thereto. 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, one portion of the composite image can exhibit phase matching, in which one color "cuts off" immediately after the viewing angle moves outside 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, 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 over 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, from multiple perspectives, the formation of 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 surfaces of the focusing elements of the planar array of focusing elements from a projection angle corresponding to a predetermined range of viewing angles, and the structured light is focused by the focusing elements of the planar array of focusing elements onto regions of uncured photocurable material that are 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 deactivated so that only the cured regions of the photocurable material are visible through the focusing elements over the predetermined range of viewing angles. 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 a micro-optical security device.

[0049] 5A-5C, which provide a non-limiting example, a side view ( FIG. 5C ), a bottom view ( FIG. 5A ), and a perspective view ( FIG. 5B ) of a refractive light-collecting element 501 disposed on a portion of an optical spacer 503. In this illustrative example, the lens surface 510 of the light-collecting element 501 defines a curved boundary between regions of different refractive index (e.g., a polymer with a refractive index greater than 1 and air), and this 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 focusing element 501 is affixed to the optical spacer 503 and has a fixed relationship with respect to the surface of the optical spacer 503. In certain embodiments, the fixed relationship between the focusing 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 place. In some embodiments, the fixed relationship between the focusing element 501 and the surface of the optical spacer 503 is achieved by forming both the focusing element 501 and the optical spacer from a common layer of photocurable material and curing the formed layer to create an integrated focusing element-optical spacer combination.

[0051] Light collection element 501 is associated with a footprint 505 that defines an area over which light collection element 501 can focus light with sufficient sharpness to allow an image icon to be projected by light collection element 501. As shown in the examples of FIGS. 5A-5C, footprint 505 can be a three-dimensional area of ​​space such that icons from multiple layers of an icon layer stack can occupy space within footprint 505. According to some embodiments, footprint 505 is coextensive with the perimeter of light collection element 501. According to some implementations, footprint 505 is smaller than the perimeter of light collection element 501. In certain embodiments, footprint 505 represents an area that is larger than the perimeter of light collection element 501.

[0052] As shown in the illustrative example of FIGS. 5A-5C , structured light (e.g., collimated light, light from a projector, or light passed through another array of focusing elements) associated with a composite image, such as the cell shown in FIGS. 5A-5C , is projected onto the lens surface of focusing element 501 at an angle (or range of angles) associated with a predetermined viewing angle, shown in the figures as Θc. The lensing action of focusing element 501 focuses the incident light along focal path 520 within footprint 505. By applying a layer of uncured photocurable colored (or substantially transparent photocurable) material to the bottom surface of optical spacer 503 prior to applying structured light to the system, subsequent application of structured light cures the portion of the photocurable material in focal path 520, while the portion of the photocurable material outside focal path 520 remains uncured and can be removed. Thus, a surface-mounted image icon 521 can be formed on the surface within footprint 505 of focusing element 501.

[0053] Figures 6A-6I illustrate aspects of the structure of micro-optical security devices according to various embodiments of the present disclosure. 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 Figure 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 some embodiments as shown, 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, 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 the 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 certain embodiments, light projected onto the planar array of focusing elements 601 at angle Θa, or a range of viewing angles including Θa, 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., 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 substantially transparent material, such as 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 fabricate 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 aspects of a micro-optical security device configuration according to certain embodiments of the present disclosure. Referring to the illustrative example of FIG. 6B, the figure shows an initial step in the fabrication of a first icon layer of an icon layer stack (e.g., icon layer stack 308 of FIG. 3A). According to certain embodiments, a plurality of retention structures 607 are formed on the underside of optical spacer 605. In this illustrative example, the plurality of retention structures 607 comprise a set of reliefs or depressions (shown in the figure as dotted fill) formed in a layer of substantially transparent material. As shown in the figure, 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 certain embodiments according to the present invention, the local repeat period P2 of the retention structures of the first icon layer of the icon layer stack varies across the icon layer such that components of the composite image projected by the first icon layer appear at different heights relative to the physical surface of the micro-optical security device.

[0058] According to some embodiments, the 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] 6C , structured light associated with components of a composite image to be projected by a first image icon layer of an image icon stack is projected at a planar array of light focusing elements 601 and passes through an optical spacer 605, a plurality of holding structures 607, and a volume of uncured first color light curable material 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 first color light material. For example, of the first color light curable material 609 in the first holding structure 608, a first portion 613 a is outside the focal path 611, while a second portion 613 b is within the focal path 611. According to some embodiments, the first portion 613 a is not cured by the curing light passing along the focal path 611, while the second portion 613 b within the focal path 611 is cured by the light passing along the focal path 611. Similarly, a third volume 613c of first color light-curable material is entirely outside 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 holding structures 607, leaving only volumes of first color curable material in the spaces of multiple holding 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 holding structures 607.

[0063] Figure 6E shows structural aspects of a micro-optical security device according to some embodiments of the present disclosure. Referring to the illustrative example of Figure 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 Figure 6C), the remaining unfilled areas 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 the planar array 601 of focusing elements). According to certain embodiments, the substantially transparent material added to the retaining structures to fill the spaces not filled by the directionally curable 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 can 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 focusing 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 focusing 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 clear light-curable material 633. The uncured, substantially clear light-curable material 633 is then directionally cured by light traveling through the structures of the icon layer stack along multiple focal paths 610, similar to the light used to cure the first color light-curable material of the first icon layer 620. As shown in the example of FIG. 6F , the volume of uncured, substantially clear light-curable material is cured in locations within the second plurality of retention structures 631 that coincide with the focal paths of the multiple focal paths 610. For example, the light-curable material occupying the first volume 635 a is cured by the light traveling along the focal path 611, while the light-curable material occupying locations 635 b outside the focal path 611 remains uncured.

[0068] FIG. 6G illustrates structural aspects of a micro-optical security device according to certain embodiments of the present disclosure. According to certain embodiments, uncured substantially transparent photo-curable material 633 within the second plurality of retention structures 631 is removed. Because the substantially transparent photo-curable material is cured at locations associated with a first range of viewing angles (e.g., at locations on the plurality of focal paths 610), additional material (e.g., a second color photo-curable material) can be added to the second plurality of retention structures only at locations associated with viewing angles outside 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 within the second plurality of retention structures 631 occupies a location that could potentially crosstalk with the cured volume of colored material (e.g., second portion 613b) within the first icon layer 620 if it were 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 structural aspects of a micro-optical security device according to various embodiments of the present disclosure.

[0070] 6H , after directionally curing a volume of uncured substantially transparent photocurable material 633 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 for 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 Figure 6H, volumes of curable material of a first color are disposed in a small section of the micro-optical security device shown in the figure with a local repeat period PC1, and volumes of curable material of a second color are disposed in a sliver of the micro-optical security device shown in Figure 6H with a local repeat period PC2. In certain embodiments according to the present disclosure, the local repeat periods of the cured volumes of material of the first color and the cured volumes of the second color may vary across the space of the micro-optical security device.

[0072] While micro-optical security devices according to various embodiments of the present disclosure have been described in Figures 6A-6H with reference to systems including only two layers and two colors, embodiments according to the present disclosure are not limited thereto, and further embodiments in which the icon layer stack includes additional layers, each layer including 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 icon colors, number of icon layers, and number of viewing angle ranges associated with a particular composite image.

[0073] FIG. 6I illustrates structural aspects 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 Figures 6A-6I, a composite image of a first color flickers, or abruptly "turns on," as the viewing angle enters the viewing angle range associated with the multiple focal paths 610 and abruptly "turns off" as the viewing angle leaves the viewing angle range associated with the multiple focal paths 610, at which point a second composite image of a second color is projected by the micro-optical system. Thus, in certain embodiments according to the present disclosure, the on-off periods of the first icon layer are phase-aligned with the off-on periods of the second icon layer. According to various embodiments, this synchronicity between the appearance of the composite image projected by the first icon layer 620 and the disappearance of the composite image projected by the second icon layer 640 is facilitated by the phasing of the volume of curable material of the first color in the first layer with the volume of curable material of the second color in the second layer. Figure 6I provides a non-limiting example of such phasing.

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

[0077] Those skilled in the art will understand that in certain embodiments according to the present disclosure, the relative thicknesses of the focusing element, icon stack, and optical spacer will differ from the illustrations of Figures 6A-6I, which are drawn to illustrate aspects of the icon structure 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 Figure 7, in certain embodiments according to the present disclosure, substantially transparent retention structures of one graphical icon layer can be integrated with volumes of substantially transparent material of another layer. In the illustrative example of Figure 7, a section 700 of a micro-optical security device according to various embodiments of the present disclosure is depicted. As shown, section 700 includes a planar array of light focusing elements 701 (e.g., planar array of light focusing elements 601 of Figure 6A), an optical spacer 703 (e.g., optical spacer 605 of Figure 6A), a first icon layer 705, and a second icon layer 710. According to certain embodiments, first icon layer 705 includes a plurality of retention structures that retain volumes of directionally curable material of a first color (e.g., first volumes 715a), which occupy positions within the retention structures associated with the focal path of structured light passing through 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 directionally curable material of the first color.

[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 unfilled areas of the graphical icon layer, and then, in some embodiments, the support structures of the next graphical icon layer are applied in three separate steps. However, in the illustrative example of Figure 7, the support 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 from the support structures and then directionally cured to create volumes of cured material of the first color within the first icon layer 705. In some embodiments, after the uncured material of the first color is washed away, a layer of uncured substantially transparent photocurable material is applied to fill unfilled areas of the first icon layer 705 and embossed to form the support structures of the second icon layer 710, which can then be cured. In 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 excess photocurable material of the second color is removed (e.g., with a doctor blade), the photocurable material of the second color is directionally cured with 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 may conclude by washing the uncured material of the second color from the second icon layer 710. Alternatively, in some embodiments, an additional "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, integrating the substantially transparent region of one graphical icon layer and the retaining structure of another graphical icon layer into a single intermediate layer can advantageously simplify the manufacturing process and eliminate a portion of the interface area between the substantially transparent material of the first icon layer 705 and the substantially transparent retaining structure of the second icon layer 710.

[0082] Figures 8A and 8B illustrate 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 Figure 8A, a section 800 of a micro-optical security device according to various embodiments of the present disclosure is shown. According to certain embodiments, section 800 includes a planar array of light focusing elements 801 (e.g., planar array of light focusing elements 307 of Figure 3A), an optical spacer 803 (e.g., optical spacer 703 of Figure 7), a first icon layer 805, and a second icon layer 810 (e.g., second icon layer 710 of Figure 7). Section 800 of the micro-optical security device further includes an intermediate layer 820 (e.g., intermediate layer 720 of Figure 7) in which the substantially transparent material of first icon layer 805 is integrated with the substantially transparent retaining structure of second icon layer 810.

[0084] As shown in the illustrative example of Figure 8A, the first icon layer 805 does not include a support structure for positioning a substantially transparent or colored light volume. Thus, an icon structure including a volume of a first color of light-curable material (e.g., including first volume 815a) is a surface-mounted image icon. According to various embodiments, the icon structure of the first icon layer 805 is fabricated 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 Figures 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 multiple focal paths 830 of structured light from one or more light sources projecting light onto section 800 at an angle (or range of angles) corresponding to a first range of viewing angles. 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 phase-aligned 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 range of viewing angles, the colored material of second icon layer 810 does not contribute to the composite image projected by the micro-optical system. However, when the viewing angle moves out of the first viewing angle range associated with the plurality of 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] Referring 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, using retaining structures as part of forming an icon layer is, in many respects, 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 offers new possibilities, including, but not limited to, the ability to modify the icon structure in the final product without incurring the retooling costs associated with creating new molds for the retaining structures, and "freeing up" area in the icon layer for additional colored icon structures. As shown in the non-limiting example of FIG. 8B , first volume 815a occupies the entire width of focal path 831. In contrast, given the spacing of the retaining structures in this example, colored icons of a similar width cannot be formed in second icon layer 810. According to certain embodiments, the micro-optical system of the present disclosure allows 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 those skilled in the art will understand that the thickness of the icon layer stack in these figures relative to the rest 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 way, the components of each layer of icon layer stack 905 appear equally "in focus" in the composite image projected by micro-optical security device 900.

[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 will reflect a trade-off 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 skilled in the art will appreciate that the overall thickness of micro-optical security device 900 will depend on a variety of factors, including, but not limited to, the number of layers in icon layer stack 905, the pitch of the light focusing elements used to construct planar array of light focusing elements 901, and the refractive index of the materials used to construct 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 micro-optical security device 900 is approximately 40 microns, 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 multiple focal paths associated with the viewing angles of the micro-optical security device, and an icon layer stack disposed along the multiple focal paths. According to various embodiments, the icon layer stack includes a first icon layer comprising volumes of curable material of a first color at locations along the focal path for a first viewing angle range and volumes of substantially transparent material at locations outside the focal path for 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 volumes of substantially transparent curable material at locations along the focal path for the first viewing angle range and volumes of curable material of a second color at locations along the focal path for the 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] An example of a micro-optical security device according to certain embodiments of the present disclosure is a security device in which a first icon layer includes a plurality of substantially transparent retaining structures and a second icon layer includes 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 is a security device in which a first icon layer includes a plurality of substantially transparent retention structures and a volume of 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 is a security device in which the second icon layer includes a plurality of substantially transparent retention structures and the volume of curable material of the first color 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 further including 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 is 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] An example of a micro-optical security device according to certain embodiments of the present disclosure includes a security device in which a planar array of microlenses includes an area in which the microlenses of the planar array of microlenses are arranged at a first local repeat period, and a first icon layer includes a second area in which volumes of hardened material of a first color are arranged at 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 project a composite image consisting of portions of the volumes of hardened material of the first color over a first viewing angle range.

[0101] An example of a micro-optical security device according to certain embodiments of the present disclosure is a security device in which the second icon layer includes a third region in which volumes of hardened material of a second color are arranged at a third local repeat period, and the ratio of the third local repeat period to the first local repeat period is such that the microlens projects a composite image consisting of portions of the volumes of hardened material of the second color in a second viewing angle range.

[0102] An example of a micro-optical security device according to certain embodiments of the present disclosure is a security device in which the first range of viewing angles includes an angle corresponding to a vector normal 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 further including one or more interface regions disposed between the substantially transparent retaining structure and one or more volumes of substantially transparent material at locations outside the focal path of the first viewing angle range.

[0104] An example of a micro-optical security device according to certain embodiments of the present disclosure is a security device in which a first viewing angle range is continuous with a second viewing angle range, and which projects a composite image consisting of a portion of a volume of cured material of a first color at a location along a focal path in 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.

[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 light focusing elements configured to focus light along multiple focal paths associated with the 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 volumes 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 volumes of curing material of a second color at locations along the focal paths for 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 is a micro-optical security device in which 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] An example of a micro-optical security device according to certain embodiments of the present disclosure includes a security device in which a planar array of focusing elements includes a region in which the focusing elements of the planar array of focusing elements are arranged at a first local repeat period, and a first icon layer includes a second region in which volumes of hardened material of a first color are arranged at a second local repeat period, and the ratio of the first local repeat period to the second local repeat period is such that the focusing elements project a composite image consisting of portions of the volumes of hardened material of the first color over a first range of viewing angles.

[0116] An example of a micro-optical security device according to an embodiment of the present disclosure is a security device in which the second icon layer includes a third region in which volumes of hardened material of a second color are arranged at a third local repeat period, and the ratio of the third local repeat period to the first local repeat period is such that the focusing element projects a composite image consisting of portions of the volumes of hardened material of the second color in a second viewing angle range.

[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 top dead center.

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

[0119] An example of a micro-optical security device according to certain embodiments of the present disclosure is a security device in which a first viewing angle range is continuous with a second viewing angle range and projects a composite image consisting of a volumetric portion of a first color of directionally curable material, the composite image becoming invisible as the viewing angle transitions from the first viewing angle range to the 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 required for inclusion in the scope of a claim. Moreover, no claim is intended to invoke 35 U.S.C. 112(f) unless the phrase "means for" is followed by a participle.

[0121] The following are appendices to the present disclosure. (Additional note 1) A micro-optical security device (105), comprising: a planar array (305) of microlenses configured to focus light along a plurality of focal paths (610) associated with the viewing angles of said micro-optical security device; an icon layer stack (905) arranged along the plurality of focal paths; the icon layer stack comprises: a volume (613b) of curable material of a first color at a location along the focal path in a first range of viewing angles; a volume of substantially transparent material at a location outside the focal path in the first range of viewing angles; 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 substantially transparent curable material at a location along the focal path in the first range of viewing angles; a volume (637a) of curable material of a second color at a location along the focal path in a second range of viewing angles; the second icon layer (640) further comprising: Including, At least one of the first icon layer or the second icon layer includes a plurality of substantially transparent retention structures. Micro-optical security device. (Additional note 2) the first icon layer includes the plurality of substantially transparent retention structures; the second icon layer includes a second plurality of substantially transparent retention structures; 2. The micro-optical security device according to claim 1. (Additional note 3) the first icon layer includes the plurality of substantially transparent retention structures; the volume of curable material of the second color includes a surface mount icon; 2. The micro-optical security device according to claim 1. (Additional note 4) the second icon layer includes the plurality of substantially transparent retention structures; the volume of curable material of the first color includes a surface mount icon (815a); 2. The micro-optical security device according to claim 1. (Additional note 5) the second color contrasts with the first color; 2. The micro-optical security device according to claim 1. (Additional note 6) the second color does not contrast with the first color; 2. The micro-optical security device according to claim 1. (Additional note 7) further comprising an optical spacer (903) disposed between the planar array of microlenses and the first icon layer; 2. The micro-optical security device according to claim 1. (Additional note 8) the first icon layer includes the plurality of substantially transparent retention structures; the substantially transparent curable material at locations outside the focal path in the first viewing angle range is integral with the second icon layer; 2. The micro-optical security device according to claim 1. (Additional note 9) the planar array of microlenses includes an area in which microlenses of the planar array of microlenses are arranged in a first local repeat period; the first icon layer includes a second region in which the volumes of hardenable material of the first color are arranged at a second local repeat period; A micro-optical security device as described in Appendix 1, wherein the ratio of the first local repeat period to the second local repeat period is such that the microlens projects a composite image consisting of a portion of the volume of hardened material of the first color in the first viewing angle range. (Additional note 10) the second icon layer includes a third region in which the volumes of hardenable material of the second color are arranged at a third local repeat period; 10. The micro-optical security device of claim 9, wherein the ratio of the third local repeat period to the first local repeat period is such that the microlens projects a composite image consisting of a portion of the volume of the second color cured material in the second viewing angle range. (Additional note 11) 2. The micro-optical security device of claim 1, wherein the first field of view angle range includes top dead center. (Additional note 12) The micro-optical security device of claim 1 further includes one or more interface regions disposed between the substantially transparent retaining structure and one or more of the volumes of the substantially transparent material at positions outside the focal path of the first field of view angle range. (Additional note 13) the first viewing angle range is contiguous with the second viewing angle range; projecting a composite image of the portion of the volume of the first color curable material at a location along a focal path in the first viewing angle range, the composite image disappearing as the viewing angle transitions from the first viewing angle range to the second viewing angle range; 2. The micro-optical security device according to claim 1. (Additional note 14) 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 the viewing angles of the micro-optical security device; an icon layer stack (905) arranged along the plurality of focal paths; the icon layer stack comprises: 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 hardened material of a second color at locations along the focal path in a second range of viewing angles; Including, at least one of the first icon layer or the second icon layer includes a plurality of substantially transparent retention structures; the second viewing angle range does not occupy the same area as the first viewing angle range; Micro-optical security device. (Additional note 15) 15. The micro-optical security device of claim 14, wherein the second icon layer further comprises a volume of directionally hardened, substantially transparent material associated with the first viewing angle range of the micro-optical security device. (Additional note 16) 15. The micro-optical security device of claim 14, wherein the second viewing angle range is complementary to the first viewing angle range. (Additional note 17) 15. The micro-optical security device of claim 14, wherein the second viewing angle range is adjacent to the first viewing angle range. (Additional note 18) 15. The micro-optical security device of claim 14, wherein the second field of view angle range overlaps with the first field of view angle range. (Additional note 19) 15. The micro-optical security device of claim 14, further comprising an optical spacer contacting at least one of the planar array of light-collecting elements or the icon layer stack. (Additional note 20) 15. The micro-optical security device of claim 14, wherein the focusing elements of the planar array of focusing elements are reflective focusing elements. (Additional note 21) 15. The micro-optical security device of claim 14, wherein the focusing elements of the planar array of focusing elements are refractive focusing elements. (Additional note 22) 15. The micro-optical security device of claim 14, wherein the second color contrasts with the first color. (Additional note 23) 15. The micro-optical security device of claim 14, wherein the second color does not contrast with the first color. (Additional note 24) the first icon layer includes the plurality of substantially transparent retention structures; the second icon layer includes a second plurality of substantially transparent retention structures; 15. The micro-optical security device according to claim 14. (Additional note 25) the first icon layer includes the plurality of substantially transparent retention structures; the volume of curable material of the second color includes a surface mount icon; 15. The micro-optical security device according to claim 14. (Additional note 26) the second icon layer includes the plurality of substantially transparent retention structures; the volume of curable material of the first color includes a surface mount icon; 15. The micro-optical security device according to claim 14. (Additional note 27) the planar array of focusing elements includes a region in which focusing elements of the planar array of focusing elements are arranged in a first local repeat period; the first icon layer includes a second region in which the volumes of hardenable material of the first color are arranged at a second local repeat period; A micro-optical security device as described in Appendix 14, wherein the ratio of the first local repeat period to the second local repeat period is such that the focusing element projects a composite image consisting of a portion of the volume of hardened material of the first color in the first viewing angle range. (Additional note 28) the second icon layer includes a third region in which the volumes of hardenable material of the second color are arranged at a third local repeat period; A micro-optical security device as described in Appendix 27, wherein the ratio of the third local repeat period to the first local repeat period is such that the focusing element projects a composite image consisting of a portion of the volume of the second color cured material in a second viewing angle range. (Additional note 29) 15. The micro-optical security device of claim 14, wherein the first field of view angle range includes top dead center. (Additional note 30) The micro-optical security device of claim 14, further comprising one or more interface regions disposed between the substantially transparent retaining structure and one or more of the volumes of the substantially transparent material at positions outside the focal path of the first field of view angle range. (Additional note 31) the first viewing angle range is contiguous with the second viewing angle range; projecting a composite image comprising the portion of the volume of directionally curable material of the first color, the composite image disappearing as the viewing angle transitions from the first viewing angle range to the second viewing angle range. 15. The micro-optical security device according to claim 14.

Claims

1. A micro-optical security device (105), comprising: a planar array (305) of microlenses configured to focus light along a plurality of focal paths (610) associated with the viewing angles of said micro-optical security device; an icon layer stack (905) arranged along the plurality of focal paths; the icon layer stack comprises: a volume (613b) of curable material of the first color at a location along the focal path at a predetermined viewing angle within the first viewing angle range; a volume of transparent material at a location outside the focal path at a predetermined viewing angle within the first viewing angle range; 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; a volume (637a) of curable material of a second color at a location along the focal path at a predetermined viewing angle within a second viewing angle range; the second icon layer (640) further comprising: Including, at least one of the first icon layer or the second icon layer includes a plurality of transparent retaining structures; the volume of curable material of the first color and the volume of curable material of the second color are phase-aligned; the planar array of microlenses includes an area in which microlenses of the planar array of microlenses are arranged in a first local repeat period; the first icon layer includes a second region in which the volumes of hardenable material of the first color are arranged at a second local repeat 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 volume portion of the first color curable material to a viewer 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; 10. The micro-optical security device of claim 1.

3. the first icon layer includes the plurality of transparent retaining structures; the volume of curable material of the second color includes a surface mount icon; 10. 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); 10. The micro-optical security device of claim 1.

5. the second color contrasts with the first color; 10. The micro-optical security device of claim 1.

6. the second color does not contrast with the first color; 10. 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; 10. 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; 10. 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 at a third local repeat period; 10. The micro-optical security device of claim 1, wherein the ratio of the first local repeat period to the third local repeat period is such that the microlenses project a composite image consisting of portions of the volume of the second colored cured material to an observer in the second viewing angle range.

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

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

12. the first viewing angle range is contiguous with the second viewing angle range; projecting a composite image of the portion of the volume of the first color curable material to an observer 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; 10. 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 the viewing angles of said micro-optical security device; an icon layer stack (905) arranged along the plurality of focal paths; the icon layer stack comprises: 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 a volume of curable material of a second color at a location along the focal path at a predetermined viewing angle 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 volume of directional curable material of the first color and the volume of curable material of the second color are phase-aligned; the second viewing angle range does not occupy the same area as the first viewing angle range; the planar array of focusing elements includes a region in which focusing elements of the planar array of focusing elements are arranged in a first local repeat period; the first icon layer includes a second region in which the volumes of hardenable material of the first color are arranged at a second local repeat period; a ratio of the first local repeat period to the second local repeat period such that the light concentrating element projects a composite image of the portion of the volume of directionally curable material of the first color to a viewer in 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 clear material associated with said first viewing angle range of said micro-optical security device.

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

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

17. 14. The micro optical security device of claim 13, wherein said second range of viewing angles overlaps with said first range of viewing angles.

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

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

21. 14. 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 curable material of the second color 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 curable material of the first color includes a surface mount icon; 14. The micro-optical security device of claim 13.

26. the second icon layer includes a third region in which the volumes of hardenable material of the second color are arranged at a third local repeat period; 14. The micro-optical security device of claim 13, wherein the ratio of the first local repeat period to the third local repeat period is such that the focusing element projects a composite image consisting of a portion of the volume of the second color cured material to an observer at a second viewing angle range.

27. 14. The micro optical security device of claim 13, wherein said first range of viewing angles includes top dead center.

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

29. the first viewing angle range is contiguous with the second viewing angle range; projecting a composite image of the volume of the first color directionally curable material to a viewer, the composite image disappearing as the viewing angle transitions from the first viewing angle range to the second viewing angle range; 14. The micro-optical security device of claim 13.

Images