Micro-optical security device with phase-aligned image layer

Abstract

A micro-optic security device (105) includes a planar microlens array (305) configured to focus light along a plurality of focal paths (610) associated with viewing angles. The micro-optic security device also includes an icon layer stack (905) positioned along the plurality of focal paths. The icon layer stack includes a first icon layer (620) having a plurality of volumes of solidified material (613b) of a first color and a plurality of volumes of substantially transparent material at locations outside the focal paths for the first viewing angle range. The icon layer stack also includes a second icon layer (640) having a plurality of volumes of solidified material of a first color at locations along the focal paths for the first viewing angle range and a plurality of volumes of solidified material of a second color at locations along the focal paths for a second viewing angle range.

Description

Technical Field

[0001] The present disclosure relates to a system for enhancing the anti-counterfeiting properties of security documents. More particularly, the present disclosure relates to a micro-optical security device having a phase-aligned image layer. Background Art

[0002] Depending on their construction and integration into end products, micro-optical security devices with dynamic, difficult-to-reproduce appearances can significantly enhance the anti-counterfeiting properties of security documents, such as currency notes, passports, and other documents requiring reliable visual identification. The overall effectiveness of a particular micro-optical security device depends on a number of variables, including, but not limited to, the uniqueness of the visual effect produced by the device, the difficulty of reproduction, and the device's mass production capabilities. For example, a micro-optical security device that produces a visual effect that is difficult to discern or visually unappealing is unlikely to be noticed by most end users, and by implication, its absence is also likely to go unnoticed by end users. In such cases, a counterfeit document lacking the correct micro-optical security device is more likely to remain undetected in circulation than one where the micro-optical security device provides a visual effect that is striking to the end user due to some combination of clarity or novelty. Similarly, the effectiveness of a micro-optical security device is enhanced when it can be manufactured on a large scale, thereby lowering the price point and promoting widespread adoption. The drive to achieve increasingly unique visual effects that are unattainable by counterfeiters but can be manufactured on a large scale by legitimate actors has long been a source of technical challenges and potential improvements in the field of micro-optical security device design. Summary of the Invention

[0003] This disclosure illustrates embodiments of a micro-optic security device having a phase-aligned image layer.

[0004] In a first embodiment, a micro-optic security device includes a planar microlens array configured to focus light along a plurality of focal paths associated with the viewing angles of the micro-optic security device. The micro-optic security device further includes an icon layer stack positioned along the plurality of focal paths. The icon layer stack includes a first icon layer comprising a plurality of volumes of solidified material of a first color at locations along the focal paths for a first range of viewing angles and a plurality of volumes of substantially transparent material at locations outside the focal paths for the first range of viewing angles. The icon layer stack further includes a second icon layer positioned below the first icon layer relative to the planar microlens array. The second icon layer further includes a plurality of volumes of solidified material of a first color at locations along the focal paths for the first range of viewing angles and a plurality of volumes of solidified material of a second color at locations along the focal paths for a second range of viewing angles. At least one of the first icon layer or the second icon layer includes a plurality of substantially transparent retention structures.

[0005] In a second embodiment, a micro-optical security device includes an array of planar focusing elements configured to focus light along a plurality of focal paths, the plurality of focal paths being associated with a viewing angle of the micro-optical security device. The micro-optical security device further includes a stack of icon layers positioned along the plurality of focal paths. The icon layer stack includes a first icon layer comprising a plurality of volumes of a directionally solidified material of a first color, wherein the plurality of volumes of the directionally solidified material of the first color are associated with a first viewing angle range of the micro-optical security device. The icon layer stack further includes a second icon layer having a plurality of volumes of a directionally solidified 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 includes a plurality of substantially transparent retaining structures. Additionally, the second viewing angle range is not of equivalent range to the first viewing angle range.

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

[0007] Before proceeding to the following detailed description, it may be advantageous to set forth the definitions of certain words and phrases used throughout this patent document. The term "coupled" and its derivatives refer to any direct or indirect communication between two or more elements, whether or not these elements are in physical contact with each other. The terms "comprise" and "include" and their derivatives mean to include, but are not limited to. The term "or" is inclusive, meaning and / or. The phrase "associated with..." and its derivatives mean to include, be included within, be interconnected with, contain, be contained within, be connected to or be connected with, be coupled to or be coupled with, can communicate with, collaborate with, be interlaced, be in parallel, be close to, be bound to or be bound with, have, have the property of, be related to or be associated with, etc. The phrase "at least one of..." when used with a list of items means that different combinations of one or more of the listed items can be used, and only one item in the list may be required. For example, “at least one of A, B, and C” includes any of the following combinations: A, B, C; A and B; A and C; B and C; and A, B, and C.

[0008] Definitions for certain other words and phrases are provided throughout this patent document. Those skilled in the art should understand that in many, if not most, cases, such definitions apply to prior as well as future uses of the defined words and phrases. BRIEF DESCRIPTION OF THE DRAWINGS

[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:

[0010] Figure 1A and Figure 1B illustrates examples of micro-optical security devices and aspects of the operation of micro-optical security devices according to various embodiments of the present disclosure;

[0011] Figure 2A and Figure 2B Various aspects of the technical challenges associated with achieving phase alignment in micro-optical security devices are illustrated by way of background art;

[0012] Figure 3A 、 Figure 3B and Figure 3C illustrates construction aspects of a micro-optical security device according to some embodiments of the present disclosure;

[0013] Figure 4A and Figure 4B illustrates aspects of the contribution of individual stacked icon layers of a micro-optic security device according to certain embodiments of the present disclosure;

[0014] Figures 5A to 5CShows examples of aspects of forming a surface-mounted image icon according to some embodiments of the present disclosure from various angles;

[0015] Figures 6A to 6I illustrates construction aspects of micro-optical security devices according to various embodiments of the present disclosure;

[0016] Figure 7 illustrates construction aspects of a micro-optical security device according to certain embodiments of the present disclosure;

[0017] Figure 8A and Figure 8B shows construction aspects of a micro-optical security device according to some embodiments of the present disclosure, and

[0018] Figure 9 Construction aspects of micro-optic security devices according to various embodiments of the present disclosure are shown. DETAILED DESCRIPTION

[0019] Discussed below Figures 1A to 9 The various embodiments used to describe the principles of the present disclosure are merely illustrative and should in no way be construed as limiting the scope of the present disclosure. Those skilled in the art will appreciate that the principles of the present disclosure can be implemented in a variety of micro-optical security devices having suitable configurations.

[0020] Although the present disclosure has been described with reference to various embodiments, various changes and modifications may occur to those skilled in the art. The present disclosure is intended to encompass such changes and modifications as fall within the scope of the appended claims.

[0021] Figure 1A and Figure 1B Examples of micro-optic security devices and aspects of their operation are shown according to certain embodiments of the present disclosure.

[0022] refer to Figure 1A to Figure 1B As a non-limiting example, a first view 101 of a security document 105 is provided. Figure 1A ) and a second view 151 ( Figure 1B ), the security document 105 includes a micro-optical security device 110. According to various embodiments, the security document 105 is a passport, a currency note, an identity card, or other document that benefits from a reliable visual authentication mark. Figure 1A to Figure 1BIn a non-limiting example, the micro-optic security device 110 includes a layer of focusing elements (e.g., microlenses) and an image stack that includes a region in which two or more image icon layers are phase-aligned. As used in this disclosure, the term "phase-aligned" as used with reference to icon structures within multiple layers of a multi-layer icon stack encompasses properties in which colored icons of a first icon layer occupy positions of the first icon layer associated with a focus path for a first range of viewing angles, colored icons of a second icon layer occupy positions of the second icon layer associated with a focus path for a second range of viewing angles, colored icons of the first icon layer occupy positions within the first icon layer associated with a focus path outside the second range of viewing angles, and colored icons of the second icon layer occupy positions of the second layer associated with a focus path outside the first range of viewing angles. In fact, with the colored image icons phase-aligned according to certain embodiments of the present disclosure, crosstalk, or the condition in which colored image icons from two or more layers of the icon stack are simultaneously projected by the focusing element 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-optic security device. According to certain embodiments of the present disclosure, controlling the incidence of crosstalk between image icon layers facilitates the creation of micro-optic security devices that exhibit improvements in at least three dimensions, which are the basis for measuring the performance of micro-optic security devices. Specifically, when phase alignment between image icons is a controllable design parameter, the transition from a multi-color composite image projected by the micro-optic security device at a first viewing angle range to a composite image projected by the micro-optic security device at a second viewing angle range can be more distinct. Embodiments of the present disclosure can, for example, produce a multi-color "flash" effect, in which the composite image includes rapidly appearing and disappearing colored components, as well as an effect in which colored regions of the composite image gradually shift or change color. Incorporating a multi-color "flash" effect in addition to a gradually evolving color effect provides a composite image that is eye-catching and captivating to the observer. Furthermore, achieving phase alignment between layers in the icon layer presents additional manufacturing challenges and implicitly makes the device more difficult to counterfeit by malicious actors. Third, certain embodiments of the present disclosure can be manufactured using structured icon tools (e.g., a mold for embossing a retaining structure into a layer of UV-curable polymer) and, as such, can be manufactured at scale.

[0023] As shown in first view 101, when security document 105 is oriented so that the surface of the document occupies values ​​within a first viewing angle range Θ1→Θ2 in coordinate system 115, the icon structure and focusing elements of micro-optic security device 110 project a two-color first composite image 120 comprising a pair of ellipses of a first color within a polygonal domain of a contrasting second color. Figures 1A to 1BAs shown in the example of FIG5 , the observer tilts the security document 105 across a first viewing angle range Θ1→Θ2 until it enters a second viewing angle range Θ2→Θ3 shown in a second view 151. In this example, as the document moves from the first viewing angle range to the second viewing angle range, the pair of ellipses "fades away," and the micro-optic system projects a second composite image, which in this illustrative example is a polygonal field of a contrasting second color, as shown in the second view 151. Thus, micro-optic systems according to various embodiments of the present disclosure provide a distinct transition from one composite image to another as the device moves between viewing angle ranges.

[0024] Although Figure 1A to Figure 1B While an example of a transition from a two-color composite image to a monochrome composite image is provided, embodiments according to the present disclosure are not limited thereto, and other embodiments involving a wider range of colors and viewing angles are possible and within the scope of the present disclosure. Furthermore, embodiments in which the colored icons of multiple layers of the icon layer stack have the same color (creating an eye-catching 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 scope of the present disclosure.

[0025] Figure 2A to Figure 2B Aspects of the technical challenges associated with achieving phase alignment within micro-optical security devices are illustrated by way of background.

[0026] exist Figure 2A to Figure 2B In the illustrative example of FIG. 1 , a first view 201 of the micro-optical unit 200 is shown. Figure 2A ) and a second view 251 ( Figure 2B ). The micro-optic security device comprises a plurality (typically millions or more) of micro-optic units. Basically, a micro-optic unit comprises a focusing element and one or more icon structures within a focal area (also referred to as a "footprint") of the focusing element. Figure 2A to Figure 2B In the illustrative example of , the micro-optic unit 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 (ie, very small curved mirrors) and gradient index ("GRIN") lenses.

[0027] In this example, the micro-optic unit 200 also includes an image icon layer 210 including a retaining structure (e.g., retaining structure 211) in which icons 213 of a colored material may be formed. The angle θa at which the focusing element 205 projects the icons 213 to the viewer depends on the position of the icons within the footprint of the focusing element 205 (illustrated by the left and right boundaries 217a and 217b). As shown with reference to the second view 251, a small shift 253 in the position of the icons relative to the footprint of the focusing element 205 translates into an angle θ at which the icons 213 are projected to the viewer. b When manufacturing at scale, some variation in the registration of the image icon layer 210's retaining structure relative to the footprint of the focusing elements is typically unavoidable. In some real-world applications, the variation in registration between focusing elements can be on the order of the pitch of the lenses in the lens array.

[0028] In the case of a micro-optic security device having a single image icon layer, changes in the registration of the image icon layer relative to the focusing elements may appear to the end user as changes in the range of angles at which a particular composite image appears to the observer. In many applications utilizing a single icon layer, this change in the viewing angle at which a particular composite image appears is not a problem or is at most a minor inconvenience because the user may have to "play around" the security document to find the viewing angle at which a particular composite image appears. In the case of a micro-optic security device with two or more icon layers stacked, the aforementioned registration changes translate into changes in the degree to which the colored icons of the icon layers are registered to one another. These changes in registration between the icon layers may appear as subtle or "faint" changes in the composite image projected by the micro-optic security device as the range of viewing angles changes. For example, in place of reference Figure 1A to Figure 1B In order to achieve a sharp transition from projecting first composite image 120 to second composite image 155 as described in the non-limiting example of FIG, the micro-optic system can simultaneously project components of the first and second composite images over an intermediate range of angles. Depending on the extent and nature of the inter-layer registration problem, the projected image can variously appear as a gradual color shifting effect (as contrasted to defined "on-off" or "flash" effects), or as a subtle blending of two or more colors, or as a visual cacophony in which different colors of different icon layers are projected without any angular relationship to each other.

[0029] Figure 3A 、 Figure 3B and Figure 3C Examples of micro-optical security devices and security documents with phase-aligned image layers according to various embodiments of the present disclosure are shown. For convenience, Figure 3C to Figure 3C Structures common to one or more of the have the same number.

[0030] refer to Figure 3A As a non-limiting example, an example of a micro-optical security device 301 according to various embodiments of the present disclosure is shown.

[0031] refer to Figure 3AAs a non-limiting example, micro-optic security device 301 generally includes a planar focusing element array 305 (e.g., including focusing element 307) and an icon layer stack 308, wherein icon layer stack 308 includes a first icon layer 320 (e.g., including image icons 321) and a second image icon layer 323 (e.g., including image icons 324). According to various embodiments, each focusing element in planar focusing element array 305 has a footprint. Furthermore, planar focusing element array includes one or more cells in which one or more image icons of the arrangement of first icon layer 320 or second image icon layer 323 are located. Furthermore, icon layer stack 308 includes at least one region in which the colored image icons of first icon layer 320 are phase-aligned with the colored image icons of second image icon layer 323. In some embodiments, the positions of the image icons (e.g., image icons 321 or 324) correspond to positions within a retaining structure made of a substantially transparent material (such as a UV curable resin) that is embossed and then cured to form an image icon layer having structures such as pores, pillars, or bumps, in which a colored material may be selectively deposited. According to some embodiments, the individual focusing elements in the planar focusing element array 305 are arranged according to one or more local repeat periods. As used in this disclosure, the term "local repeat period" encompasses an expression of how frequently a particular feature of a layer of the micro-optical security device 301 repeats within a region of interest. For example, the focusing elements in the planar focusing element array 305 may have a local repeat period of 50 lenses / mm in one area and a local repeat period of 49 lenses / mm in a different portion of the system. Similarly, the colored icons within first icon layer 320 may, for example, have a local repeat period of 51 icons / mm in a portion of micro-optical security device 301 and a local repeat period of 49.5 icons / mm in a different region of micro-optical security device 301. By varying the ratio of the local repeat period of the focusing elements to the local repeat period of the icon structures, various aspects of the appearance of the composite image of the icon structures projected by the focusing 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 varied by the ratio of the local repeat period of the focusing elements to the local repeat period of the icon structures, such that the composite image can appear to float above the plane of the micro-optical security device 301, or to be positioned 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 focusing elements to the local repeat period of the colored icon structures can itself be locally varied to give the composite image a more three-dimensional appearance.

[0032] In accordance with certain embodiments, the plurality of focusing elements 305 comprises a planar array of micro-optical focusing elements. In some embodiments, the focusing elements in the planar focusing element array 305 comprise micro-optical refractive focusing elements (e.g., plano-convex or GRIN microlenses) in which the lens surface provides a curved interface between regions of differing refractive indices (e.g., polymer lens material and air). The refractive focusing elements in the planar focusing element array 305 are, in some embodiments, made of a photocurable resin having a refractive index in the range of 1.35 to 2.05 and have a diameter in the range of 5 μm to 200 μm. In various embodiments, the focusing elements in the planar focusing element array 305 comprise reflective focusing elements (e.g., very small concave mirrors) having a diameter in the range of 5 μm to 50 μm. While the focusing elements in the planar focusing element array 305 are shown in this illustrative example as comprising circular plano-convex lenses, other refractive lens geometries (e.g., biconvex lenses) are possible and within the scope of the present disclosure.

[0033] like Figure 3A As shown in the illustrative example of FIG, first icon layer 320 includes a set of image icons (including image icon 321) positioned at locations associated with a range of directional solidification angles within the footprint of focusing elements in planar focusing element array 305. According to various embodiments, individual image icons of first icon layer 320 include regions of directionally solidified material within some or all of the space defined by a retaining structure of a structured image icon layer formed of a substantially transparent material. As used in this disclosure, the term "structured image layer" encompasses a layer of substantially transparent material (e.g., a photocurable resin) that has been embossed or otherwise formed to include structures (e.g., grooves, posts, indentations, or bumps) for positioning and retaining image icon material.

[0034] like Figure 3AAs shown in the illustrative example of FIG, in certain embodiments, the micro-optic security device 301 includes an optical spacer 310. According to various embodiments, the optical spacer 310 includes a film of substantially transparent material that is used to position image icons in one or more image icon arrangements of the icon layer stack 308 about a focal plane of a focusing element in the planar focusing element array 305. In certain embodiments according to the present disclosure, the optical spacer 310 includes a fabrication substrate onto which one or more layers of photocurable material can be applied, imprinted, and batch cured to form a retaining structure. In certain embodiments, the photocurable material used to form the first icon layer 320 is a pigmented ultraviolet (UV) curable 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 make the focusing elements in the planar focusing element array 305) between the focusing elements and the icon layer stack 308.

[0035] In certain embodiments according to the present disclosure, the micro-optic security device 301 includes a sealing layer 340. According to certain embodiments, the sealing layer 340 comprises a thin (e.g., 2 μm to 50 μm thick) layer of substantially transparent material that interfaces on a lower surface with the focusing elements in the planar focusing element array 305, and comprises an upper surface that has a smaller variation in curvature than the planar focusing element array 305 (e.g., due to being smooth or due to having a locally undulating surface with a larger radius of curvature than the focusing elements).

[0036] like Figure 3A In some embodiments, as shown in the non-limiting example of FIG, micro-optic security device 301 may be attached to substrate 350, for example, via adhesive layer 330, to form security document 360 (e.g., Figures 1A to 1B 105 in the security document 105). According to various embodiments, substrate 350 can be a piece of currency paper or a polymer substrate. According to some embodiments, substrate 350 is a thin, flexible polymer film, biaxially oriented polypropylene (BOPP). In various embodiments, substrate 350 is a length of synthetic paper material (such as TESLIN®). According to some embodiments, substrate 350 is a length 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 commodity such as a smartphone or computer).

[0037] Although Figure 3AAn example of a micro-optic security device 301 is shown in which both the first icon layer 320 and the second image icon layer 323 are formed within a structured image icon layer constructed of a substantially transparent material, but embodiments according to the present disclosure are not limited thereto. While the technology for forming tools for imprinting thin layers of photocurable material to form retention structures is mature and integrated with mass production tools for micro-optic security devices, other techniques for forming image icons are possible and can be used in conjunction with the structured icon layer in micro-optic security devices having phase-aligned icon layers according to various embodiments of the present disclosure. For example, in certain embodiments according to the present disclosure, a digital tooling method can be used to produce the image icon arrangement or the second image icon arrangement. As used in the present disclosure, a digital tooling method encompasses a method for manufacturing component structures (e.g., image icons or focusing elements) by defining the control logic of an electronic tool (e.g., a G-CODE file for a printer) for forming and placing the component structures of the micro-optic security device. As discussed 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 the first image icon arrangement or the second image icon arrangement can be formed as surface-mounted icons using a digital tooling method.

[0038] As another example of a digital tool 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-optic security device) onto a layer of transparent or colored uncured photocurable material to form a surface-mounted image icon. In certain embodiments, the one or more UV projectors project a pattern of ultraviolet light through a layer of focusing elements, thereby directionally curing a portion 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.

[0039] refer to Figure 3B In this particular example, the first image icon layer 320 has a non-limiting example of Figure 3A , wherein the graphic icons are formed as areas of colored material positioned within a space defined by a retaining structure, which in this particular example comprises an embossed and cured polymer layer. According to certain embodiments, the retaining structure within first icon layer 320 is filled with a first color of light-curable liquid material and then directionally cured such that a portion of the light-curable material is cured to a solid state while another portion of the light-curable material remains liquid and can be removed from the retaining structure, such as by washing.

[0040] As used in this disclosure, the term "directional curing" encompasses directing light based on projecting structured or semi-structured light (e.g., collimated light) in a pattern toward elements in an array of focusing elements from a source (or sources) positioned at positions associated with a series of predetermined viewing angles for a composite image provided by a micro-optic security device, such that the focusing elements focus the light on uncured material occupying positions in the image icon layer associated with the viewing angles. In other words and as, for example, described by the present disclosure Figures 6A to 6I As described in the illustrative example of , along the lines from sources associated with a range of viewing angles and composed of an array of focusing elements (e.g., Figure 3A Uncured material in the focal path of light focused by the focusing elements in the planar focusing element array 305) is cured, while uncured material in locations outside the focal path of the directional curing light focused by the focusing elements remains uncured.

[0041] According to certain embodiments, after the uncured material of the first color is washed from the holding structure, directional curing of the material of the other color or other iterations associated with different viewing angles are performed. Figure 3B In the illustrative example of FIG, the final step in forming first icon layer 320 is to fill the open spaces (e.g., areas not occupied by the cured colored material) with a substantially transparent light-curable material that is barely or completely invisible to at least the human eye. According to certain embodiments, the substantially transparent material layer can be inspected using an imaging device, such as an electron microscope.

[0042] refer to Figure 3B By way of non-limiting example, according to certain embodiments, icons (e.g., surface-set icons 326) or multiple volumes of cured colored material of the second icon layer 328 may be formed on the surface of the first icon layer 320 by at least two of the methods described herein.

[0043] According to certain embodiments, in one method of forming surface-mounted icons on a surface of first icon layer 320, first icon layer 320 is formed by first forming a set of retaining structures (e.g., by embossing and then batch curing a layer of a photocurable polymer). In various embodiments, in a second step, the retaining structures are then filled with uncured substantially transparent photocurable material, excess uncured substantially transparent photocurable material is scraped off from the retaining structures, wherein the material in the retaining structures is directionally cured using directional curing light having a pattern associated with a first viewing angle range to form a plurality of regions of cured substantially transparent material associated with the first viewing angle range within first icon layer 320. Subsequently, the uncured substantially transparent photocurable material is washed from the retaining structures, and the remaining usable retaining structures are filled or coated with uncured photocurable material of a first color, excess uncured photocurable material is scraped off from the retaining structures, and the remaining material is batch cured to complete first icon layer 320 having a substantially flat outer surface facing away from array of planar focusing elements 305. According to certain embodiments, an uncured photocurable material of a second color is applied to the outer surface and directionally cured using light associated with the first viewing angle range, as in the second step of forming first icon layer 320. After directionally curing, the uncured photocurable material of the second color is washed away from the outer surface, so that the surface-disposed icons of second icon layer 328 remain on the outer surface of the first icon layer.

[0044] According to certain embodiments, another method for forming a second icon layer 328 of a surface-mounted image icon includes forming the first icon layer 320 as described above and applying a layer of uncured light-curable material of a second color. The uncured light-curable material of the second color is directionally cured using patterned light at an angle complementary to the first range of angles used to cure the material of the first color. This allows for a controlled separation between the range of angles over which a composite image of the colored material of the first color is projected by the focusing element and the range of angles over which a composite image of the colored material of the second color is projected by the focusing element.

[0045] Figure 3C An example of a micro-optical security device 301 is shown according to various embodiments of the present disclosure.

[0046] Figure 3B The illustrative examples of show examples of micro-optic security devices according to the present disclosure in which an image icon layer comprising surface-mounted icons is positioned away from an array of focusing elements relative to another image icon comprising a plurality of substantially transparent retaining structures, and in which, among other things, Figure 3CAn example of a micro-optic security device 301 is shown in which a surface-disposed image icon layer is proximate to the focusing elements relative to an icon layer comprising a substantially transparent retention structure.

[0047] refer to Figure 3C In a non-limiting example, first icon layer 327 includes a plurality of surface-set image icons (including surface-set image icon 329) formed on one side of 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, the light coming from a structured light source positioned to provide light within a first viewing angle range. In this illustrative example, after directionally curing, the uncured material of the first color is removed, and optionally, subsequent sets of surface-set icons associated with different colors or different viewing angles are formed by directionally curing material of the first color or other colors. The uncured pigmented material is removed from the surface of optical spacer 310, and a layer of substantially transparent material is applied to fill the spaces between the surface-set image icons and form a flat surface on which second image icon layer 323 can be formed as an image icon layer including a retaining structure. According to various embodiments, the layer of substantially transparent material is applied so that the substantially transparent material of first icon layer 327 and the retaining structure of second image icon layer 323 are integral.

[0048] In some embodiments, the retaining structure of the second image icon layer 323 is filled with uncured photocurable material of a second color, which is then spread to remove excess uncured material. The uncured photocurable material of the second color is directionally cured using light having a pattern associated with the first viewing angle range, and the uncured material of the second color is washed away. Depending on the number of layers specified for icon layer stack 308, in some embodiments, the process of manufacturing icon layer stack 308 may end at this point without performing any further filling / curing operations.

[0049] Figure 4A and Figure 4B A micro-optical security device (e.g., Figure 1A and Figure 1B

[0014] Various aspects of the contribution of stacked icon layers of a micro-optic security device 110 in a micro-optic security device according to various embodiments of the present disclosure include an icon layer stack that is magnified by an array of focusing elements to provide a composite image that provides unique and appealing optical effects, including but not limited to multi-color composite images, with tight control over a range of viewing angles, within which each layer of the icon layer stack contributes to the composite image provided by the micro-optic security device. As discussed elsewhere herein, micro-optic security devices according to some embodiments of the present disclosure include an icon stack with phase-aligned image icon layers.

[0050] refer to Figures 4A to 4B , which shows an illustrative example of a first image icon layer (e.g., Figure 3A ) and a second image icon layer (e.g., Figure 3B The contribution of the second icon layer 328 in FIG4 to the composite image projected by the system within the first viewing angle range (θ1→θ2) and the second viewing angle range (θ2→θ3). For ease of cross-reference, in the example of FIG4 , the composite image projected by the micro-optic security device to the observer corresponds to Figure 1A to Figure 1B The composite image shown in the illustrative example of FIG. That is, when viewed at angles within a first range of viewing angles, the micro-optic device projects a pair of ellipses of a first color on a background of a second color. In this non-limiting example, as viewing angles span from the first range to the second range of viewing angles, the colored ellipses "fade" and are replaced by the composite image of the second color due to phase alignment between icons in a first image icon layer containing image icons of the first color and icons in a second image icon layer containing image icons of the second color.

[0051] like Figures 4A to 4B As shown in , when the micro-optic security device is viewed at angles within a first viewing angle range (θ1→θ2), the focusing elements of the device project multiple regions of the first icon layer comprising directional volumes of cured material of a first color, such that the first image icon layer contributes to visible regions in the composite image in the form of first ellipse 401a and second ellipse 401b. According to certain embodiments, in addition to directionally curing the uncured material of the first color in the first icon layer into a pattern associated with ellipses 401a and 401b, uncured substantially transparent material in the second icon layer is directionally cured into a pattern associated with ellipses 401a and 401b, but excluding colored material of the second color from the focal path associated with the first viewing angle range, and ensuring that corresponding regions 403a and 403b of the second icon layer do not crosstalk or interfere with the regions of the first icon layer that produced ellipses 401a and 401b.

[0052] Similarly, with respect to the second viewing angle range (θ2 → θ3), in certain embodiments, an uncured substantially transparent material is applied to the first layer and directionally cured by a light source associated with the second viewing angle range, thereby ensuring that the first icon layer does not contribute to the composite image projected by the micro-optic security device within the second viewing angle range 405. That is, in some embodiments, no colored material is present in the first icon layer at locations associated with the focal path of light passing into or out of the micro-optic security device along angles associated with the second viewing angle range.

[0053] Additionally, with respect to a second viewing angle range (θ2→θ3), in various embodiments according to the present disclosure, multiple volumes of uncured material of the second color are directionally cured using structured light provided from a 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 component derived solely from the second image icon layer.

[0054] While the micro-optic security device has been described with reference to providing a single "flash" effect produced by directionally curing a colored material of a first color in one layer of an icon layer stack and directionally curing a colorless material in a second icon layer over the same range of viewing angles, Figures 4A to 4B , but embodiments according to the present disclosure are not limited thereto. For example, in certain embodiments, techniques for achieving control over the phasing of the icon layers and the viewing angles at which the colored material of each layer of the image icon stack contributes to the composite image can be used to produce different effects. For example, in certain embodiments, a portion of the composite image can exhibit phase alignment, such as described with reference to FIG4 , where one color immediately “fades” after the viewing angle is moved outside of a first viewing angle range, while a different portion of the composite image exhibits a slight phase misalignment where the color changes with viewing angle. Additionally, in certain embodiments and as described with reference to FIG4 , a portion of the composite image can exhibit phase alignment, such as described with reference to FIG4 , where one color immediately “fades” after the viewing angle is moved outside of a first viewing angle range. Figure 3B As discussed, phase alignment between the colored material in the first image icon layer and the colored material in the second image icon layer can be achieved by directionally curing the uncured material in the second image icon layer at a viewing angle range that is complementary to the first viewing angle range used to directionally cure the colored material in the first image icon layer.

[0055] Figures 5A to 5C Aspects of forming a surface-mounted image icon in one unit of a micro-optic security device according to certain embodiments of the present disclosure are shown from various angles.

[0056] In certain embodiments according to the present disclosure, to form a surface-mounted image icon, structured light is projected at lens surfaces of focusing elements in a planar focusing element array from a projection angle corresponding to a predetermined range of viewing angles, wherein the focusing elements in the planar focusing element array focus the structured light onto regions of uncured photocurable material within the footprint of the focusing elements in the planar focusing element array. The uncured photocurable material is then removed (e.g., by spraying) or chemically inactivated such that only the cured regions of the photocurable material are visible through the focusing elements within the predetermined range of viewing angles. In this manner, a cured volume of colored material (e.g., an image icon) or substantially transparent material (e.g., excluding colored material from locations that would interfere with the contribution of a colored icon in another layer of the icon layer stack) can be formed on the surface of the micro-optic security device.

[0057] refer to Figures 5A to 5C , a side view of a refractive focusing element 501 is provided as a non-limiting example. Figure 5C )、Bottom side view( Figure 5A ) and angled views ( Figure 5B ), the refractive focusing element 501 is positioned over a portion of the optical spacer 503. In this illustrative example, the lens surface 510 of the focusing element 501 defines a curved boundary between regions of different refractive indices (e.g., air and a polymer having a refractive index greater than 1) that direct curing light to locations within the footprint of the lens, wherein the curing light cures the plurality of volumes of light-curable material of the first color to form the surface-disposed image icons 521.

[0058] According to certain embodiments, the focusing element 501 is attached to the optical spacer 503 and has a fixed relationship with 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, imprinting the layer of photocurable material to form the lens surface, and curing the material in situ. 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 form an integrated focusing element-optical spacer combination.

[0059] The focusing element 501 is associated with a footprint 505, defining a region in which the focusing element 501 can focus light with sufficient sharpness to enable the focusing element 501 to project an image icon. Figures 5A to 5CAs shown in the example of FIG, footprint 505 can be a three-dimensional spatial area, thereby allowing icons of multiple layers of the icon layer stack to occupy space within footprint 505. According to some embodiments, footprint 505 is coextensive with the perimeter of focusing element 501. According to some embodiments, footprint 505 is smaller than the perimeter of focusing element 501. In certain embodiments, footprint 505 describes an area that is larger than the perimeter of focusing element 501.

[0060] like Figures 5A to 5C As shown in the illustrative example of FIG, the angle (or angle range) associated with the predetermined viewing angle is used to combine the composite image (such as Figures 5A to 5C Structured light (e.g., collimated light, light from a projector, or light that has passed through another focusing element array) associated with the unit shown in FIG5 is projected at the lens surface of the focusing element 501, and the predetermined viewing angle is shown in the figure as θ c The lens action of the focusing element 501 focuses incident light along a focal path 520 within the footprint 505. By applying a layer of uncured photocurable colored (or substantially transparent photocurable) material to the bottom surface of the optical spacer 503 before applying the structured light to the system, the subsequent application of structured light causes the portion of the photocurable material in the focal path 520 to be cured, while the portion of the photocurable material outside the focal path 520 is uncured and can be removed. Thus, a surface-disposed image icon 521 can be formed on the surface within the footprint 505 of the focusing element 501.

[0061] Figures 6A to 6I 1 shows aspects of the construction of micro-optical security devices according to various embodiments of the present disclosure. For ease of cross-reference, Figures 6A to 6I Elements common to more than one of the embodiments have like numbering.

[0062] refer to Figure 6A As a non-limiting example, a section of a planar focusing element array 601 of a micro-optic security device according to certain embodiments of the present disclosure is shown. In some embodiments, such as shown in the figure, the focusing elements in the planar focusing element array 601 are plano-convex microlenses. In some embodiments, the focusing elements in the planar focusing element array 601 are reflective focusing elements or different refractive structures (e.g., GRIN lenses). As shown in the figure, the focusing elements of the section of the planar focusing element array 601 have a local repeat period P1, which corresponds to the distance over which a pattern of similarly sized focusing elements repeats in the section of the planar focusing element array 601 shown in the figure.

[0063] In certain embodiments, at an angle θ a or including Θ aLight projected onto the planar focusing element array 601 is focused by the constituent elements of the planar focusing element array 603 and passes through the optical spacer 605 and subsequent layers (e.g., the icon layer stack) of the micro-optical security device along multiple focus paths 610 (e.g., including focus path 611).

[0064] According to certain embodiments, the micro-optic security device includes an optical spacer 605 comprising a sheet of substantially transparent material (such as polyethylene or polyester film), a focusing element and an icon layer stack (e.g., Figure 3A The icon layer stack 308 in FIG. 3 may be formed on the sheet of substantially transparent material. According to some embodiments, the optical spacer 605 comprises an intermediate layer of a substantially transparent photocurable polymer that is used to form other structures of the micro-optic security device, such as the planar focusing element array 601. In various embodiments according to the present disclosure, the optical spacer 605 comprises a length of biaxially oriented polypropylene (BOPP), polycarbonate, polyvinyl chloride (PVC), or polyethylene terephthalate (PET) film.

[0065] Figure 6B illustratively illustrate aspects of the construction of a micro-optical security device according to certain embodiments of the present disclosure. Figure 6B , which shows an illustrative example of forming an icon layer stack (e.g., Figure 3A 6. In some embodiments, a plurality of retaining structures 607 are formed on the bottom side of optical spacer 605. In this illustrative example, plurality of retaining structures 607 comprise a set of reliefs or recesses (shown in dashed fill lines in the figure) formed in a layer of substantially transparent material. As shown in the figure, plurality of retaining structures 607 are formed on the bottom side of optical spacer 605. Figure 6B has a local repeat period P2 in the segments of the micro-optical security device shown in In certain embodiments according to the present disclosure, the local repeat period P2 of the retention structure of a first icon layer of the icon layer stack varies across the icon layers 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.

[0066] According to some embodiments, the plurality of retention structures 607 are filled with uncured photocurable material 609 of a first color.

[0067] Figure 6C Construction aspects of a micro-optical security device according to certain embodiments of the present disclosure are shown.

[0068] refer to Figure 6CIn a non-limiting example, structured light associated with a component of a composite image to be projected by a first image icon layer of an image icon stack is projected at planar focusing element array 601 and passes through optical spacer 605, a plurality of retaining structures 607, and a plurality of volumes of uncured photocurable material 609 of a first color. As shown in this non-limiting example, the focal path of the light passing through optical spacer 605 does not encompass the entire volume of the uncured photocurable material of the first color. For example, within first retaining structure 608, a first portion 613a of the photocurable material of the first color is outside of focal path 611, while a second portion 613b is within focal path 611. In some embodiments, first portion 613a is not cured by curing light delivered along focal path 611, while second portion 613b, which is within focal path 611, is cured by light delivered along focal path 611. Similarly, a third volume of photocurable material of the first color 613c is completely outside of focal path 611 and adjacent focal paths and is uncured.

[0069] Figure 6D Construction aspects of micro-optic security devices according to various embodiments of the present disclosure are shown.

[0070] As shown in this illustrative example, when using structured light from a first viewing angle range (e.g., along Figure 6C After the light-curable material of the first color is qualitatively cured by light traveling along the plurality of focal paths 610 in the plurality of retaining structures 607, uncured material is removed from the plurality of retaining structures 607, leaving only the plurality of volumes of cured material of the first color in the spaces of the plurality of retaining structures 613 in the focal paths 611. For example, while the plurality of volumes of uncured material of portions 613a and 613c are removed after directional curing, the second portion 613b remains in place in the plurality of retaining structures 607.

[0071] Figure 6E illustratively illustrates aspects of the construction of a micro-optical security device according to some embodiments of the present disclosure. Figure 6E illustrative example, to help "lock" multiple volumes of solidified material (e.g., second portion 613b) into multiple retaining structures 607 that are aligned with a particular focal path (e.g., Figure 6CThe remaining unfilled areas of the retaining structure 607 are filled with a substantially transparent material (e.g., a UV-curable polymer suitable for imprinting and curing to form the planar focusing element array 601) at locations associated with the focus path 611 in the directionally solidified region. According to certain embodiments, the substantially transparent material added to the retaining structure to fill the spaces not yet filled by the directionally solidified material forms an interface region (e.g., interface region 615) between the substantially transparent retaining structure and the additional substantially transparent material. Although invisible to the human eye, the interface region, including the boundaries between these areas of substantially transparent material, is visible under an electron microscope.

[0072] In certain embodiments according to the present disclosure, a substantially transparent material is added to the unfilled areas of the plurality of retaining structures 607 to complete the construction of the first icon layer 620 , and a second icon layer or more icon layers of the icon layer stack may be formed on the first icon layer 620 .

[0073] Figure 6F Construction aspects of micro-optic security devices according to various embodiments of the present disclosure are shown.

[0074] According to some embodiments, a plurality of layers ( Right now The second layer of a stack of two or more icon layers. Figure 6F As shown in the non-limiting example of , a second plurality of retention structures 631 are formed (e.g., by embossing and subsequently curing a layer of substantially transparent UV curable material) on a surface of the first icon layer 620 remote from the planar focusing element array 601.

[0075] refer to Figure 6F As a non-limiting example, the recesses of the second plurality of retaining structures 631 are filled with a plurality of volumes of uncured substantially transparent photocurable material 633. The uncured substantially transparent photocurable material 633 is then directionally cured by light that travels through the structure of the icon layer stack along the same plurality of focal paths 610 as the light used to cure the first color photocurable material in the first icon layer 620. Figure 6F As shown in the example of , multiple volumes of uncured substantially transparent light-curable material are cured at locations within second plurality of retention structures 631 that overlap with focal paths in plurality of focal paths 610. For example, light-curable material occupying first volume 635a is cured by light traveling along focal path 611, while light-curable material occupying locations 635b outside of focal path 611 is not cured.

[0076] Figure 6G63. The uncured substantially transparent photocurable material 633 in the second plurality of retaining structures 631 is removed. Since the substantially transparent photocurable material is cured at positions associated with the first viewing angle range ( For example 613b ).

[0077] Figure 6H Construction aspects of micro-optic security devices according to various embodiments of the present disclosure are shown.

[0078] refer to Figure 6H As a non-limiting example, after directionally curing multiple volumes of uncured substantially transparent light-curable material 633 and removing the uncured material outside of multiple focal paths 610, multiple volumes of uncured material of a second color are used to fill the unfilled spaces of the second plurality of retaining structures 631 (i.e., locations associated with focal paths for viewing angles other than the first viewing angle range) and cured to form multiple volumes of cured material of the second color (e.g., first volume 637a and second volume 637b). In this way, second icon layer 640 is formed on top of first icon layer 620.

[0079] like Figure 6H As shown in the illustrative example of FIG, multiple volumes of solidified material of a first color are arranged with a local repeating period P in a small section of the micro-optical security device shown in the figure. C1 Placed, and multiple volumes of cured material of the second color are Figure 6H The micro-optical security device shown in FIG. C2 In certain embodiments according to the present disclosure, the local repeat period of the plurality of volumes of cured material of the first color and the plurality of volumes of cured material of the second color can vary within the space of the micro-optic security device.

[0080] Although already Figures 6A to 6H While micro-optic security devices according to various embodiments of the present disclosure are described with reference to a system including only two layers and two colors, embodiments according to the present disclosure are not so limited, and other embodiments in which the icon layer stack includes additional layers, each layer including multiple volumes of cured material in multiple colors associated with multiple viewing angles, are possible and within the scope of the present disclosure. In other words, Figure 6H Operational and constructional aspects of the micro-optic security system are scalable across multiple dimensions, including icon color, number of icon layers, and number of viewing angle ranges associated with a particular composite image.

[0081] Figure 6I Construction aspects of micro-optic security devices according to various embodiments of the present disclosure are shown.

[0082] refer to Figure 6I A non-limiting example of Figure 6H , wherein only the multiple focus paths 610 superimposed on the figure are used to help illustrate how the multiple volumes of solidified material of the first color in the first icon layer 620 are phase-aligned with the multiple volumes of solidified material of the second color in the second icon layer 640.

[0083] exist Figures 6A to 6I In the illustrative example of FIG, a composite image of a first color suddenly flashes or "appears" when the viewing angle enters the range of viewing angles associated with multiple focal paths 610, and suddenly "fades" when the viewing angle leaves the range of viewing angles associated with multiple focal paths 610, at which point a second composite image of a second color projected by the micro-optical system appears. Thus, in certain embodiments according to the present disclosure, the appearance-disappearance cycle of the first icon layer is in phase with the disappearance-appearance cycle of the second icon layer. According to various embodiments, this synchronization between the appearance of the composite image projected by first icon layer 620 and the disappearance of the composite image projected by second icon layer 640 is facilitated by phase alignment of the multiple volumes of cured material of the first color in the first layer with the multiple volumes of cured material of the second color in the second layer. Figure 6I Non-limiting examples of the phase alignment are provided.

[0084] like Figure 6IAs shown in FIG, second portion 613b of first icon layer 620 is bounded by the left edge of focal path 611 and is therefore projected by planar focusing element array 601 at a perspective within the first viewing angle range. Similarly, first volume 637a of second icon layer 640 abuts but does not intersect the left edge of focal path 611. Therefore, first volume 637a is not projected by the planar focusing element array at perspectives within the first viewing angle range. However, because the positions of second portion 613b and first volume 637a are aligned with the left edge of focal path 611, entering and exiting the first viewing angle range results in a distinct transition between the composite image projected by first icon layer 620 and the composite image projected by second icon layer 640.

[0085] Skilled artisans will appreciate that in certain embodiments according to the present disclosure, the relative thicknesses of the focusing elements, icon stacks, and optical spacers may differ from Figures 6A to 6I , which are diagrams drawn to illustrate aspects of icon structures of micro-optic security devices according to various embodiments of the present disclosure.

[0086] Figure 7 Construction aspects of micro-optic security devices according to various embodiments of the present disclosure are shown.

[0087] refer to Figure 7 By way of non-limiting example, in certain embodiments according to the present disclosure, a substantially transparent retaining structure of one image icon layer may be integral with multiple volumes of substantially transparent material in another layer. Figure 7 In an illustrative example of FIG, a section 700 of a micro-optical security device according to various embodiments of the present disclosure is shown. As shown in the figure, the section 700 includes an array of planar focusing elements 701 (e.g., Figure 6A Planar focusing element array 601 in), optical spacer 703 (e.g., Figure 6A 705 ), first icon layer 705, and second icon layer 710. According to certain embodiments, first icon layer 705 includes a plurality of retaining structures containing multiple volumes of directionally solidified material of a first color (e.g., first volume 715a), the directionally solidified material occupying locations in the retaining structures associated with the focal path of structured light passing through segment 700 from a light source associated with a first viewing angle or range of viewing angles. In some embodiments, to facilitate phase alignment between the colored materials in first icon layer 705 and second icon layer, regions of the retaining structures of first icon layer 705 not filled with the directionally solidified material of the first color are filled with a substantially transparent material.

[0088] As referenced in this disclosure Figure 6E and Figure 6FAs described in the non-limiting example of , in certain embodiments, areas of colored material are directionally cured, a substantially transparent material is applied and cured to fill the unfilled areas of the image icon layer, and then, in some embodiments, a retaining structure for the next image icon layer is applied in three discrete steps. However, in Figure 7 In the illustrative example of a first icon layer 705, a retaining structure is formed (e.g., by embossing and curing a substantially transparent photocurable polymer) and filled with uncured photocurable material of a first color. After excess first color photocurable material is scraped off the retaining structure, directional curing is then performed to form multiple volumes of cured material of the first color within first icon layer 705. In some embodiments, after the uncured first color material has been washed away, a layer of uncured substantially transparent photocurable material can be applied to fill the unfilled areas of first icon layer 705, embossed to form a retaining structure for second icon layer 710, and then cured. According to the described embodiment, the substantially transparent retaining structure of second icon layer 710 is integral with portions of first icon layer 705 and forms a single "square wave"-shaped intermediate layer 720 spanning first and second icon layers 705, 710. In certain embodiments according to the present disclosure, the retaining structure of second icon layer 710 is filled with uncured photocurable material of a second color. After excess photocurable material of the second color is removed (e.g., by a doctor blade), the photocurable material of the second color is directionally cured by patterned light associated with the second viewing angle range and is left uncured. Depending on the specifications of the micro-optical device (e.g., where only a two-layer icon layer stack is specified), the manufacturing process ends by washing the uncured material of the second color from second icon layer 710. Alternatively, in some embodiments, another "square wave" of substantially transparent material is integral with second icon layer 710 and provides a surface for forming a third icon layer (not shown) (e.g., a retaining structure, or a flat surface on which surface-mounted icons can be formed).

[0089] Depending on the embodiment, integrating the substantially transparent area of ​​the image icon layer and the retaining structure of another image icon layer into a single intermediate layer can help simplify the manufacturing process and remove some 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.

[0090] Figure 8A and Figure 8B 1 shows aspects of the construction of micro-optical security devices according to various embodiments of the present disclosure. For ease of cross-reference, Figure 8A and Figure 8B Structures that are common to both have the same number.

[0091] refer to Figure 8A As a non-limiting example, a section 800 of a micro-optical security device according to various embodiments of the present disclosure is shown. According to some embodiments, the section 800 includes an array of planar focusing elements 801 (e.g., Figure 3A Planar focusing element array 307 in), optical spacer 803 (e.g., Figure 7 optical spacer 703 in), first icon layer 805 and second icon layer 810 (e.g., Figure 7 The second icon layer 710 in the micro-optical security device. Segment 800 of the micro-optical security device also includes an intermediate layer 820 (e.g., Figure 7 an intermediate layer 720 in the middle), wherein the substantially transparent material of the first icon layer 805 is integral with the substantially transparent retaining structure of the second icon layer 810.

[0092] like Figure 8A As shown in the illustrative example of FIG, first icon layer 805 does not contain a retaining structure for positioning multiple volumes of substantially transparent or colored photocurable material. Therefore, the icon structure containing multiple volumes of photocurable material of a first color (e.g., including first volume 815a) is a surface-set image icon. According to various embodiments, the icon structure of first icon layer 805 is produced by directionally curing portions of an applied layer of uncured photocurable material of a first color (e.g., according to the disclosure of reference 1). FIG5A to FIG5B ).

[0093] Figure 8B This is illustrated by showing multiple focus paths 830 of structured light from one or more sources. Figure 8A In other aspects of the configuration of the segment 800 of the micro-optical security device, the one or more sources project light onto the segment 800 at an angle (or range of angles) corresponding to the first range of viewing angles. Figure 8B By way of non-limiting example, in certain embodiments according to the present disclosure, surface-mounted image icons (e.g., first volume 815a) can be phase-aligned with icons formed in a retaining structure. As shown in this non-limiting example, in second icon layer 810, the left edge of first volume 815a and the right edge of second volume 815b are bounded by the left edge of focal path 831. Thus, at viewing angles within a first range of viewing angles, the colored material in second icon layer 810 does not contribute to the composite image projected by the micro-optic system. However, due to, for example, the phase alignment between first volume 815a and second volume 815b, when the viewing angle leaves the first range of viewing angles associated with plurality of focal paths 830, the micro-optic system distinctly "transitions" from projecting material in first icon layer 805 to projecting material in second icon layer 810.

[0094] refer to Figure 8B illustrative examples of the present disclosure, flexibility in the design of micro-optic security systems is provided according to certain embodiments of the present disclosure. As previously described in this disclosure, the use of a retaining structure as part of forming the icon layer is in many respects a mature technology that has been improved and adapted for mass production of micro-optic security devices. At the same time, digital tooling and forming the icon structure without having to make a mold for the retaining structure provides new possibilities, including but not limited to being able to change the icon structure of the final product without the re-tooling costs associated with making new molds for the retaining structure, and "freeing up" areas of the icon layer for additional colored icon structures. Figure 8B , first volume 815a occupies the full width of focal path 831. In contrast, given the spacing of the retaining structures in this example, it is not possible to form colored icons of similar width in second icon layer 810. According to certain embodiments, micro-optic systems according to the present disclosure allow designers and manufacturers of micro-optic security devices to blend physical tooling (i.e., using molded retaining structures) and digital tooling (i.e., making surface-mounted icons) in the layers of an image icon stack, thereby combining the flexibility of digital tooling with the convenience and accumulated expertise of working with physical tooling.

[0095] With the present disclosure Figures 6A to 6I and Figure 7 Likewise, the skilled person will understand that Figure 8A and Figure 8B In the illustrative examples of FIG, the various figures have been drawn to emphasize the icon structure, and the thickness of the icon layer stack relative to the rest of the micro-optical device in these figures may be different from that of some real devices.

[0096] Figure 9 Construction aspects of micro-optic security devices according to various embodiments of the present disclosure are shown.

[0097] refer to Figure 9 As an illustrative example of a micro-optic security device 900, an example 900 of a micro-optic security device 900 is provided to illustrate the proportions of a dual-layer icon layer stack relative to the remainder of the micro-optic security device 900 according to certain embodiments of the present disclosure.

[0098] According to some embodiments, the micro-optic security device 900 includes an array of planar focusing elements 901 (e.g., Figure 6A Planar focusing element array 603 in), optical spacer 903 (e.g., Figure 3A909) and icon layer stack 905 including first icon layer 907 and second icon layer 909. In various embodiments, micro-optic security device 900 is configured such that the focusing elements in planar focusing element array 901 focus light onto a point in plane 911 along the boundary between first icon layer 907 and second icon layer 909. In this manner, components of each layer of icon layer stack 905 similarly appear "in focus" in the composite image projected by micro-optic security device 900.

[0099] In various embodiments according to the present disclosure, the micro-optic security device 900 has an overall thickness 913 of 5 to 500 microns, as measured from the outside of the second icon layer 909 to the outside of the planar array of focusing elements 901. In some embodiments, the micro-optic security device 900 has an overall thickness in the range of 10 to 200 microns. In some embodiments, the micro-optic security device 900 has a thickness of 20 to 60 microns. Skilled artisans will appreciate that in many embodiments, the overall thickness of the device reflects a compromise between various performance parameters of interest, including the maximum allowable thickness of the micro-optic security device 900, manufacturing concerns (e.g., the number of steps in the manufacturing process), and the optical performance requirements of the end user (e.g., the detailed and dynamic programming of the visual effects provided by the micro-optic security device 900). The skilled artisan will further appreciate that the overall thickness of the micro-optic security device 900 depends on various factors, including, but not limited to, the number of layers in the icon layer stack 905, the pitch of the focusing elements used to construct the planar focusing element array 901, and the refractive index of the material used to construct the planar focusing element array 901; and that embodiments thicker or thinner than 5 to 500 microns are possible and within the scope of the present disclosure. According to certain embodiments in which the micro-optic security device 900 has an overall thickness of approximately 40 microns, the dual-layer image icon stack 905 has a thickness of approximately 3 microns.

[0100] Examples of micro-optic security devices according to certain embodiments of the present disclosure include a security device comprising: a planar microlens array configured to focus light along a plurality of focal paths associated with the viewing angles of the micro-optic security device; and an icon layer stack disposed along the plurality of focal paths. According to various embodiments, the icon layer stack comprises a first icon layer comprising a plurality of volumes of cured material of a first color at locations along the focal paths for a first range of viewing angles and a plurality of volumes of substantially transparent material at locations outside the focal paths for the first range of viewing angles. The icon layer stack further comprises a second icon layer disposed below the first icon layer relative to the planar microlens array. The second icon layer comprises a plurality of volumes of cured material of a first color at locations along the focal paths for the first range of viewing angles and a plurality of volumes of cured material of a second color at locations along the focal paths for a second range of viewing angles. At least one of the first icon layer or the second icon layer comprises a plurality of substantially transparent retention structures.

[0101] Examples of micro-optic security devices according to certain embodiments of the present disclosure include a security device wherein the first icon layer includes the plurality of substantially transparent retention structures, and wherein the second icon layer includes a second plurality of substantially transparent retention structures.

[0102] Examples of micro-optic security devices according to certain embodiments of the present disclosure include a security device wherein the first icon layer comprises the plurality of substantially transparent retention structures, and wherein the plurality of volumes of solidified material of the second color constitute surface-set icons.

[0103] Examples of micro-optic security devices according to certain embodiments of the present disclosure include a security device wherein the second icon layer comprises the plurality of substantially transparent retention structures, and wherein the plurality of volumes of solidified material of the first color constitute surface-set icons.

[0104] Examples of micro-optic security devices according to certain embodiments of the present disclosure include security devices wherein the second color contrasts with the first color.

[0105] Examples of micro-optic security devices according to certain embodiments of the present disclosure include security devices wherein the second color does not contrast with the first color.

[0106] Examples of micro-optic security devices according to certain embodiments of the present disclosure include a security device further comprising an optical spacer disposed between the planar microlens array and the first icon layer.

[0107] Examples of micro-optical security devices according to certain embodiments of the present disclosure include a security device wherein the first icon layer includes the plurality of substantially transparent retention structures, and wherein the substantially transparent solidified material at a location outside of the focal path of the first viewing angle range is integral with the second icon layer.

[0108] Examples of micro-optical security devices according to certain embodiments of the present disclosure include a security device wherein the planar microlens array includes a region in which the microlenses in the planar microlens array are arranged with a first local repeat period, wherein the first icon layer includes a second region in which multiple volumes of solidified material of the first color are arranged with a second local repeat period, and wherein the ratio of the first local repeat period to the second local repeat period causes the microlenses to project a composite image of portions of the multiple volumes of solidified material of the first color within the first viewing angle range.

[0109] Examples of micro-optical security devices according to certain embodiments of the present disclosure include a security device wherein the second icon layer includes a third zone in which the multiple volumes of solidified material of the second color are arranged with a third local repeat period, and wherein the ratio of the first local repeat period to the third local repeat period causes the microlens to project a composite image of portions of the multiple volumes of solidified material of the second color within the second viewing angle range.

[0110] Examples of micro-optic security devices according to certain embodiments of the present disclosure include security devices wherein the first range of viewing angles includes angles corresponding to vectors normal to a plane of the micro-optic security device ( For example, top dead center).

[0111] Examples of micro-optical security devices according to certain embodiments of the present disclosure include a security device comprising one or more interface regions disposed between a substantially transparent retention structure and one or more of a plurality of volumes of substantially transparent material at locations outside of a focal path of the first viewing angle range.

[0112] Examples of micro-optic security devices according to certain embodiments of the present disclosure include a security device wherein the first viewing angle range is continuous with the second viewing angle range, and wherein the micro-optic security device projects a composite image of portions of multiple volumes of cured material of the first color at positions along a focal path of the first viewing angle range, the composite image disappearing when the viewing angle transitions from the first viewing angle range to the second viewing angle range.

[0113] Examples of micro-optical security devices according to certain embodiments of the present disclosure include a security device comprising: an array of planar focusing elements configured to focus light along a plurality of focal paths associated with the viewing angles of the micro-optical security device; and an icon layer stack positioned along the plurality of focal paths, the icon layer stack comprising: a first icon layer comprising a plurality of volumes of directionally solidified material of a first color, wherein the plurality of volumes of directionally solidified material of the first color are associated with a first viewing angle range of the micro-optical security device; and a second icon layer comprising a plurality of volumes of solidified material of a second color at positions along the focal paths for a second viewing angle range, wherein at least one of the first icon layer or the second icon layer comprises a plurality of substantially transparent retaining structures, and wherein the second viewing angle range is not of the same range as the first viewing angle range.

[0114] Examples of micro-optical security devices according to certain embodiments of the present disclosure include a micro-optical security device wherein the second icon layer further comprises a plurality of volumes of directionally solidified substantially transparent material, and wherein the plurality of volumes of directionally solidified substantially transparent material are associated with the first viewing angle range of the micro-optical security device.

[0115] Examples of micro-optic security devices according to certain embodiments of the present disclosure include a micro-optic security device wherein the second range of viewing angles is complementary to the first range of viewing angles.

[0116] Examples of micro-optic security devices according to certain embodiments of the present disclosure include a micro-optic security device wherein the second viewing angle range is adjacent to the first viewing angle range.

[0117] Examples of micro-optic security devices according to certain embodiments of the present disclosure include a micro-optic security device wherein the second viewing angle range overlaps with the first viewing angle range.

[0118] Examples of micro-optic security devices according to certain embodiments of the present disclosure include a security device further comprising an optical spacer contacting at least one of the array of planar focusing elements or the icon layer stack.

[0119] Examples of micro-optic security devices according to certain embodiments of the present disclosure include security devices wherein the focusing elements in the array of planar focusing elements are reflective focusing elements.

[0120] Examples of micro-optic security devices according to certain embodiments of the present disclosure include security devices wherein the focusing elements in the array of planar focusing elements are refractive focusing elements.

[0121] Examples of micro-optic security devices according to certain embodiments of the present disclosure include security devices wherein the second color contrasts with the first color.

[0122] Examples of micro-optic security devices according to certain embodiments of the present disclosure include security devices wherein the second color does not contrast with the first color.

[0123] Examples of micro-optical security devices according to certain embodiments of the present disclosure include a security device wherein the array of planar focusing elements includes a region in which the focusing elements in the array of planar focusing elements are arranged with a first local repeat period, wherein the first icon layer includes a second region in which the multiple volumes of solidified material of the first color are arranged with a second local repeat period, and wherein the ratio of the first local repeat period to the second local repeat period causes the focusing elements to project a composite image of portions of the multiple volumes of directionally solidified material of the first color within the first viewing angle range.

[0124] Examples of micro-optical security devices according to certain embodiments of the present disclosure include a security device wherein the second icon layer includes a third zone in which the multiple volumes of solidified material of the second color are arranged with a third local repeat period, and wherein the ratio of the first local repeat period to the third local repeat period causes the focusing element to project a composite image of portions of the multiple volumes of solidified material of the second color within a second viewing angle range.

[0125] Examples of micro-optic security devices according to certain embodiments of the present disclosure include security devices wherein the first viewing angle range includes top dead center.

[0126] Examples of micro-optical security devices according to certain embodiments of the present disclosure include a security device comprising one or more interface regions disposed between the substantially transparent retention structure and one or more of a plurality of volumes of substantially transparent material at locations outside of a focal path of the first viewing angle range.

[0127] Examples of micro-optical security devices according to certain embodiments of the present disclosure include a security device wherein the first viewing angle range is continuous with the second viewing angle range, and the micro-optical security device projects a composite image of portions of the multiple volumes of directional solidified material of the first color, wherein the composite image disappears when the viewing angle transitions from the first viewing angle range to the second viewing angle range.

[0128] This disclosure should not be interpreted as implying that any particular element, step, or function is essential to the scope of the claims. Furthermore, the claims are not intended to invoke 35 USC § 112(f) unless the specific phrase "means for..." is followed by a participle.

Claims

1. A micro-optical security device (105), comprising: a planar microlens array (305) configured to focus light along a plurality of focal paths, the plurality of focal paths (610) being associated with a viewing angle of the micro-optical security device; as well as An icon layer stack (905) is positioned along the plurality of focus paths, the icon layer stack comprising: A first icon layer (620), the first icon layer (620) comprising: a plurality of volumes of solidified material (613b) of a first color, the plurality of volumes of solidified material (613b) of the first color being located along a focal path of a first range of viewing angles; and a plurality of volumes of substantially transparent material located outside of a focal path of the first range of viewing angles; and a second icon layer (640), the second icon layer (640) being disposed below the first icon layer relative to the planar microlens array, the second icon layer further comprising; a plurality of volumes of substantially transparent solidified material located along a focal path of the first range of viewing angles; and a plurality of volumes of solidified material (637a) of a second color, the plurality of volumes of solidified material (637a) of the second color being located along a focal path of a second range of viewing angles, Wherein at least one of the first icon layer or the second icon layer includes a plurality of substantially transparent retention structures.

2. The micro-optical security device according to claim 1, wherein the first icon layer comprises the plurality of substantially transparent retention structures, and Wherein the second icon layer comprises a second plurality of substantially transparent retention structures.

3. The micro-optical security device according to claim 1, wherein the first icon layer comprises the plurality of substantially transparent retention structures, and wherein the plurality of volumes of solidified material of the second color constitute a surface-set icon.

4. The micro-optical security device according to claim 1, wherein the second icon layer comprises the plurality of substantially transparent retention structures, and wherein the plurality of volumes of solidified material of the first color constitute a surface-mounted icon (815a).

5. The micro-optical security device according to claim 1, The second color contrasts with the first color.

6. The micro-optical security device according to claim 1, wherein the second color does not contrast with the first color.

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

8. The micro-optical security device according to claim 1, wherein the first icon layer comprises the plurality of substantially transparent retention structures, and The substantially transparent solidified material at a position outside the focal path of the first viewing angle range is integral with the second icon layer.

9. The micro-optical security device according to claim 1, wherein the planar microlens array comprises a region in which the microlenses in the planar microlens array are arranged with a first local repetition period, wherein the first icon layer includes a second region wherein a plurality of volumes of solidified material of the first color are arranged with a second local repeating period, and wherein a ratio of the first local repeat period to the second local repeat period causes the microlenses to project a composite image of portions of the plurality of volumes of solidified material of the first color over the first range of viewing angles.

10. The micro-optical security device according to claim 9, wherein the second icon layer includes a third region wherein a plurality of volumes of solidified material of the second color are arranged with a third local repeat period, and wherein a ratio of the first local repeat period to the third local repeat period causes the microlenses to project a composite image of portions of the plurality of volumes of solidified material of the second color over the second range of viewing angles.

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

12. The micro-optical security device of claim 1 , further comprising: One or more interface regions disposed between the substantially transparent retention structure and one or more of the plurality of volumes of substantially transparent material at locations outside of a focal path of the first range of viewing angles.

13. The micro-optical security device according to claim 1, The first viewing angle range and the second viewing angle range are continuous, and wherein the micro-optic security device projects a composite image of portions of multiple volumes of solidified material of the first color at positions along a focal path of a first viewing angle range, the composite image disappearing when the viewing angle transitions from the first viewing angle range to the second viewing angle range.

14. A micro-optical security device, comprising: an array of planar focusing elements (305) configured to focus light along a plurality of focus paths, the plurality of focus paths (610) being associated with a viewing angle of the micro-optic security device; as well as An icon layer stack (905) is positioned along the plurality of focus paths, the icon layer stack comprising: a first icon layer (620), the first icon layer (620) comprising a plurality of volumes of directionally solidified material of a first color, wherein the plurality of volumes of directionally solidified material of the first color are associated with a first range of viewing angles of the micro-optic security device; as well as a second icon layer (640) comprising a plurality of volumes of solidified material of a second color at locations along a focal path for a second range of viewing angles, wherein at least one of the first icon layer or the second icon layer comprises a plurality of substantially transparent retention structures, and The second viewing angle range is not the same as the first viewing angle range.

15. The micro-optical security device of claim 14, wherein the second icon layer further comprises a plurality of volumes of directionally solidified substantially transparent material, and wherein the plurality of volumes of directionally solidified substantially transparent material are associated with the first viewing angle range of the micro-optical security device.

16. The micro-optic security device of claim 14, wherein the second range of viewing angles is complementary to the first range of viewing angles.

17. The micro-optic security device of claim 14, wherein the second viewing angle range is adjacent to the first viewing angle range.

18. The micro-optic security device of claim 14, wherein the second viewing angle range overlaps with the first viewing angle range.

19. The micro-optic security device of claim 14, further comprising an optical spacer contacting at least one of the array of planar focusing elements or the icon layer stack.

20. The micro-optic security device of claim 14, wherein the focusing elements in the array of planar focusing elements are reflective focusing elements.

21. The micro-optic security device of claim 14, wherein the focusing elements in the array of planar focusing elements are refractive focusing elements.

22. The micro-optic security device of claim 14, wherein the second color contrasts with the first color.

23. The micro-optic security device of claim 14, wherein the second color does not contrast with the first color.

24. The micro-optical security device according to claim 14, wherein the first icon layer comprises the plurality of substantially transparent retention structures, and Wherein the second icon layer comprises a second plurality of substantially transparent retention structures.

25. The micro-optical security device according to claim 14, wherein the first icon layer comprises the plurality of substantially transparent retention structures, and wherein the plurality of volumes of solidified material of the second color constitute a surface-set icon.

26. The micro-optical security device according to claim 14, wherein the second icon layer comprises the plurality of substantially transparent retention structures, and wherein the plurality of volumes of solidified material of the first color constitute a surface-set icon.

27. The micro-optical security device of claim 14, wherein the array of planar focusing elements comprises a region wherein the focusing elements in the array of planar focusing elements are arranged with a first local repeat period, wherein the first icon layer includes a second region wherein a plurality of volumes of solidified material of the first color are arranged with a second local repeating period, and Wherein a ratio of the first local repeat period to the second local repeat period causes the focusing element to project a composite image of portions of the plurality of volumes of directionally solidified material of the first color over the first range of viewing angles.

28. The micro-optical security device according to claim 27, wherein the second icon layer includes a third region wherein a plurality of volumes of solidified material of the second color are arranged with a third local repeat period, and Wherein a ratio of the first local repeat period to the third local repeat period causes the focusing element to project a composite image of portions of the plurality of volumes of solidified material of the second color over a second range of viewing angles.

29. The micro-optic security device of claim 14, wherein the first viewing angle range includes top dead center.

30. The micro-optical security device of claim 14, further comprising one or more interface regions disposed between the substantially transparent retention structure and one or more of the plurality of volumes of substantially transparent material at locations outside of a focal path of the first viewing angle range.

31. The micro-optical security device of claim 14, The first viewing angle range and the second viewing angle range are continuous, and The micro-optic security device projects a composite image of portions of the plurality of volumes of directionally solidified material of the first color, the composite image disappearing when a viewing angle transitions from the first viewing angle range to the second viewing angle range.

Images