MICRO-OPTIC SECURITY DEVICE WITH ABSOLUTE REGISTRATION

A micro-optic security device (100) includes a planar array of micro-optic focusing elements (105) and a first arrangement of image icons (120), wherein each image icon (121) of the first arrangement of image icons includes a region of light-cured material. Further, the first arrangement of image icons is visible (320) through the planar array of micro-optic focusing elements across a first predetermined range of viewing angles relative to the micro-optic security device, and the first arrangement of image icons is not visible (360) through the planar array of micro-optic focusing elements across a second pre-determined range of viewing angles relative to the micro-optic security device.

TECHNICAL FIELD

This disclosure relates generally to anti-counterfeiting of secure and/or high value documents, such as banknotes, passports and tickets. More specifically, this disclosure relates to a micro-optic security device with absolute registration between focusing elements and individual micro-optic layers which are magnified by the focusing elements.

BACKGROUND

Certain documents, including, without limitation, banknotes and some government-issued documents, utilize micro-optic security devices which comprise a plurality of small scale focusing elements (for example, micro-lenses), each of which has a footprint, in which visual information is provided to create a synthetic image which is visible to a viewer of the document. While the visual information in the footprint of any given lens is generally too small to be visible to the human eye, the collective operation of each focusing element of the plurality of focusing elements produces a humanly visible display (sometimes referred to as a “synthetically magnified” image, or a “synthetic image”) of a portion of the visual information provided in the footprint of each focusing element's footprint. This humanly visible display provides difficult-to-counterfeit indicia of the document's authenticity.

By controlling aggregate dimensional properties (for example, pitch and angle) of visual information placed under the footprints of multiple focusing elements, the appearance of the humanly visible display provided by the micro-optic system can be tuned. For example, by adjusting the period of repetition between items of visual information (for example, an icon) relative to the pitch, or repeat period of the focusing elements, the perceived distance of the humanly visible display (which in some embodiments, is a synthetic image) relative to the plane of the document can be adjusted, such that the display appears to “float” above the document, or is at a depth below the document. Similarly, by slightly rotating an axis of repetition of the visual information relative to an axis of repetition of the plurality of focusing elements, an orthoparallactic visual effect can be achieved, wherein tilts in viewing perspective along one axis produce positional shifts in the humanly visible display along an orthogonal axis.

While a wide range of visual effects and properties of the humanly visible displays provided by micro-optic security systems can be produced by controlling aggregate spatial relationships between visual information and focusing elements, absolute registration, or the ability to position visual information at a particular location within the footprint of a focusing element, and, by implication, being able to provide visible displays at predetermined viewing angles, remains a source of technical challenges and opportunities for improvement.

SUMMARY

This disclosure provides a micro-optic security device with absolute registration.

In a first embodiment, a micro-optic security device includes a planar array of micro-optic focusing elements and a first arrangement of image icons, wherein each image icon of the first arrangement of image icons includes a region of light-cured material. Further, the first arrangement of image icons is visible through the planar array of micro-optic focusing elements across a first predetermined range of viewing angles relative to the micro-optic security device, and the first arrangement of image icons is not visible through the planar array of micro-optic focusing elements across a second predetermined range of viewing angles relative to the micro-optic security device.

In a second embodiment, a method of manufacturing a micro-optic system includes applying a layer of light-curable material to a first surface of the micro-optic system having a fixed relationship to a planar array of focusing elements, wherein the first surface is disposed proximate to one or more focal points of focusing elements of the planar array of focusing elements. The method further includes directing a first pattern of structured light at a lensing surface of the planar array of focusing elements until a first portion of the layer of light-curable material is cured to form a first arrangement of image icons, and removing or deactivating uncured light-curable material from the first surface of the micro-optic system. Additionally, the first pattern of structured light is directed at the lensing surface of the planar array of focusing elements from a first predetermined range of viewing angles relative to the planar array of focusing elements.

DETAILED DESCRIPTION

FIG. 1illustrates an example of a micro-optic system100according to certain embodiments of this disclosure according to this disclosure.

Referring to the non-limiting example ofFIG. 1, micro-optic system100comprises, at a fundamental level, a plurality of focusing elements105(including, for example, focusing element107), and an arrangement of image icons120(including, for example, image icon121). According to various embodiments, each focusing element of plurality of focusing elements105has a footprint, in which one or more image icons of arrangement of image icons120is positioned. In certain embodiments, the location of the image icons within arrangement of image icons120within the respective footprints of the focusing elements of plurality of focusing elements105is associated with a predetermined range of viewing angles relative to a coordinate system using the plane of the plurality of focusing elements105.

By controlling the visibility of the arrangement of image icons120over a predetermined range of viewing angles (relative to a plane of the plurality of focusing elements105), the performance of micro-optic system100is enhanced in at least the following regards: variation in viewing angles associated with a humanly visible display produced by micro-optic system100is reduced, thereby making it easier to detect counterfeits, and more complicated visual effects within a humanly visible display (for example, 3-D effects) may be achieved. According to certain embodiments, micro-optic system100can project, without limitation, synthetically magnified images, images with movement effects (for example, where the image appears to change position within a visual plane), and animation effects (for example, where the visual content projected by the system comprises views of at least one common visual element which sequentially change over a range of viewing angles, providing, for example, a “flip book” effect), or combinations thereof.

According to certain embodiments, plurality of focusing elements105comprises a planar array of micro-optic focusing elements. In some embodiments, the focusing elements of plurality of focusing elements105comprise micro-optic refractive focusing elements (for example, plano-convex or GRIN lenses). Refractive focusing elements of plurality of focusing elements105are, in some embodiments, produced from light cured resins with indices of refraction ranging from 1.35 to 1.7, and have diameters ranging from 5 μm to 200 μm. In various embodiments, the focusing elements of plurality of focusing elements105comprise reflective focusing elements (for example, very small concave mirrors), with diameters ranging from 5 μm to 50 μm. While in this illustrative example, the focusing elements of plurality of focusing elements105are shown as comprising circular plano-convex lenses, other refractive lens geometries, for example, lenticular lenses, are possible and within the contemplated scope of this disclosure.

As shown in the illustrative example ofFIG. 1, arrangement of image icons120comprises a set of image icons (including image icon121), positioned at predetermined locations within the footprints of the focusing elements of plurality of focusing elements105. According to various embodiments, the individual image icons of arrangement of image icons120comprise regions of light cured material associated with the focal path of structured light (for example, collimated UV light) light passing through plurality of focusing elements105from a projection point associated with one or more predetermined ranges of viewing angles. In some embodiments, the individual image icons of arrangement of image icons120are not provided within a structured image icon layer. As used in this disclosure, the term “structured image layer” encompasses a layer of material (for example, a light-curable resin) which has been embossed, or otherwise formed to comprise structures (for example, recesses, posts, grooves, or mesas) for positioning and retaining image icon material. According to various embodiments, the individual image icons of arrangement of image icons120are provided within a structured image layer, while at the same time, in absolute registration with a predetermined location in the footprint of a focusing element. In certain embodiments according to this disclosure, one or more image icon elements of arrangement of image icons120has a “gumdrop” shape, wherein a sidewall of the image icon tapers inwards towards a point of focus of a focusing element of plurality of focusing elements105.

As shown in the illustrative example ofFIG. 1, in certain embodiments, micro-optic system100includes an optical spacer110. According to various embodiments, optical spacer110comprises a film of substantially transparent material which operates to position image icons of arrangement of image icons120in or around the focal plane of focusing elements of plurality of focusing elements105. In certain embodiments according to this disclosure, optical spacer110comprises a manufacturing substrate upon which one or more layers of light curable material can be applied, and then selectively cured with structured light passed through plurality of focusing elements105.

According to various embodiments, micro-optic system100comprises one or more regions of light-cured protective material130which occupy the spaces between the image icons of arrangement of image icons120. In some embodiments, the arrangement of image icons120is first formed (for example, by selectively curing and removing liquid light-curable material on optical spacer110), and then a layer of clear, light-curable material is applied to fill spaces between the image icons of arrangement of image icons120and then flood-cured to create a protective layer, which protects the image icons from being moved from their positions within the footprints of focusing elements of plurality of focusing elements105. In certain embodiments, the light-curable material used to form arrangement of image icons120is a pigmented, ultraviolet (UV)-curable polymer. In some embodiments, as an alternative to a light-curable material, protective layer130may be formed from an adhesive material suitable for affixing micro-optic system100to substrate150. According to various embodiments, by constructing protective layer130from an adhesive, the harvesting-resistance of micro-optic system100may be enhanced, in that, attempts to harvest micro-optic system100will cause some or all of the image icons of arrangement of image icons120to separate from micro-optic system100and remain adhered to substrate150, thereby rendering micro-optic system100visibly compromised.

In certain embodiments according to this disclosure, micro-optic system100comprises a seal layer140. According to certain embodiments, seal layer140comprises a thin (for example, a 2 μm to 50 μm thick layer) of substantially clear material which interfaces on a lower surface, with focusing elements of the plurality of focusing elements105, and comprises an upper surface with less variation in curvature (for example, by being smooth, or by having a surface whose local undulations are of a larger radius of curvature than the focusing elements) than the plurality of focusing elements105.

As shown in the non-limiting example ofFIG. 1, in certain embodiments, micro-optic system100can be attached to a substrate150, to form a security document160. According to various embodiments, substrate150can be a sheet of currency paper, or a polymeric substrate. According to some embodiments, substrate150is a thin, flexible sheet of a polymeric film, biaxially oriented polypropylene (BOPP). In various embodiments, substrate150is a section of a synthetic paper material, such as TESLIN®. According to some embodiments, substrate150is a section of a polymeric card material, such as a polyethylene terephthalate (PET) blank of a type suitable for making credit cards and driver's licenses.

FIG. 2illustrates an example of a micro-optic security device and a footprint of a focusing element of the micro-optic security device according to various embodiments of this disclosure.

Referring to the non-limiting example ofFIG. 2, a security document200is shown. According to various embodiments, security document200is a currency note. In some embodiments, security document200is an identification document, such as a page of a passport or a driver's license.

As shown in the illustrative example ofFIG. 2, security document200comprises a micro-optic security device205(for example, micro-optic system100inFIG. 1). According to certain embodiments, micro-optic security device205is substantially coplanar with security document200, and some or all of micro-optic security device205is maintained in a sufficiently flat condition to define a coordinate system207suitable for defining a viewing angle or viewing vector indicating a direction of incidence of a viewer's view of micro-optic security device205, or a direction in which light is directed from micro-optic security device205. In this explanatory example, micro-optic security device is depicted as a plane in a three-dimensional Cartesian coordinate system207. Other coordinate systems, and refinements to account for curvature in micro-optic security device205are possible and within the contemplated scope of this disclosure.

As shown in the enlargement210of a portion of micro-optic security device205, micro-optic security device205comprises an arrangement of image icons215(for example, arrangement of image icons120inFIG. 1), wherein each image icon of the arrangement of image icons comprises a region of light cured material with a focally tapered sidewall profile. According to various embodiments, and as shown in enlargement210, micro-optic security device205further comprises a planar array of focusing elements220. In some embodiments according to this disclosure, micro-optic security device205is relatively flexible, and can bend to accommodate intended bending (for example, bending of a currency note in a wallet or while moving around rollers in a vending machine or automatic teller machine). Accordingly, as used in this disclosure, the term “planar,” as used in this disclosure, encompasses the property that, at a micro-level (for example, considering millimeter length sections of micro-optic security device205), the constituent elements of micro-optic security device can be considered to be planar.

According to various embodiments, one or more of sealing layer140, plurality of focusing elements105, optical spacer110and protective layer130are formed from a light-curable material which is a polymeric matrix, and which can be applied in a liquid, or “goo” form to a flat surface and then cured using light to form harder, more dimensionally stable structures. Examples of materials for use in such polymeric matrices, and which have an index of refraction of 1.5 or less include, without limitation, isodecyl acrylate, dipropylene glycol diacrylate, tripropylene glycol diacrylate, polyester tetraacrylate, trimethylolpropane triacrylate, and hexanediol diacrylate. Further examples of light-curable materials according to embodiments of this include substantially transparent or clear, colored or colorless polymers such as acrylics, acrylated polyesters, acrylated urethanes, epoxies, polycarbonates, polypropylenes, polyesters and urethanes. Still further examples of materials which can be used in polymeric matrices according to some embodiments of this disclosure include, without limitation, acrylate monomers, acrylate oligomers, O-phenlyphenoxyethyl acrylate, phenylthioethyl acrylate, bis-phenylthioethyl acrylate, cumin phenoxyl ethyl acrylate, a biphenylmethyl acrylate, bisphenol A epoxy acrylates, fluorene-type acrylates, brominated acrylates, halogenated acrylates, melamine acrylates and combinations thereof. According to certain embodiments, the composition of the light curable material is specifically formulated to not include materials with a polarizing element, such as iodine, bromine, chlorine or sulfur.

In various embodiments according to this disclosure the index of refraction of material used to construct one or more of sealing layer140, plurality of focusing elements105, optical spacer110or protective layer130can be tuned, or adjusted, by adding, or adjusting the concentration of nanoparticles in the material mixture (for example, a polymeric matrix) used to form the component layer of micro-optic system100. According to some embodiments, the index of refraction of certain component layers of micro-optic system100can be adjusted by adding, for example, inorganic nanoparticles with a particle diameter of 100 nm or less to the mixture. Examples of inorganic nanoparticles which can be added to a material mixture include, without limitation, aluminum oxide, zirconium dioxide, titanium dioxide, zinc sulfide or zinc telluride. According to certain embodiments, the addition of nanoparticles to the material mixture can raise the index of refraction of the material mixture from below 1.5, to above 1.7. In some embodiments, indices of refraction above 1.7 are possible through the addition of nanoparticles to an organic resin.

While in the non-limiting example ofFIG. 2, the focusing elements of planar array of focusing elements220are shown as refractive focusing elements (in this example, plano-convex lenses), other embodiments using other types of focusing elements (for example, reflective focusing elements) are possible and within the contemplated scope of this disclosure.

As shown by further enlargement230, each focusing element240of planar array of focusing elements220is associated with a footprint250. According to various embodiments, footprint250comprises an area in which image icons can be placed, and upon which light can be focused by focusing element240. Depending on embodiments, the area and shape of footprint250may be co-extensive with (for example, a circle having the same diameter and center) focusing element240. Alternatively, in certain embodiments, the footprint of a focusing element may be larger than the focusing element, and can overlap with the footprint(s) of other focusing elements. In some embodiments, footprint250comprises a subset of the area beneath focusing element240.

In certain embodiments, within footprint250, one or more image icons260and265are positioned at positions within footprint250associated with a predetermined viewing angle of micro-optic security device205. According to various embodiments, the one or more image icons260and265are formed from regions of light-cured material. In certain embodiments, the individual regions of light-cured material have a “gumdrop-like” shape, with sidewalls that taper inwards as the distance between the image icon and the focusing element increases. In some embodiments, the sidewall of the region of cured material may not exhibit the above-described focal taper, and will instead be substantially perpendicular to the plane of the surface upon which the region of light cured material is formed.

As suggested by the gridlines within footprint250, each of image icons260and265occupy predefined positions within the area of footprint250. By occupying predefined positions within footprint250, each of image icons260and265can be said to exhibit absolute registration. As used in this disclosure, the term “absolute registration” encompasses a further degree of registration between focusing elements and image icons beyond aggregate registration. In a micro-optic system exhibiting aggregate registration, the aggregate dimensions of a layer of focusing elements and a layer of image icons register, with a humanly visible display appearing at an unknown viewing angle, and (in some embodiments), changing (for example, by turning on and off) at predetermined angles relative to the unknown viewing angle. However, in a system exhibiting aggregate registration, for a given footprint of a given focusing element, the location of the image icon within that footprint is not predetermined, or otherwise known in advance. By contrast, in a system exhibiting absolute registration, the positions of image icons within a particular footprint are predetermined, and associated with providing a particular human visible display at a predefined viewing angle in a coordinate system (for example, coordinate system207). Thus, according to certain embodiments, micro-optic systems (for example micro-optic security device205), with absolute registration exhibit an unexpectedly high degree of angular control over one or more human-visible displays provided by the micro-optic system.

While the illustrative example ofFIG. 2describes an embodiment in which the image icons260and265in footprint250contain all of the features of their respective human-visible displays, embodiments according to this disclosure are not so limited. According to certain embodiments, footprint250can include a control pattern, and regions of light-cured material corresponding to only part of a human-visible display can be provided within footprint250.

FIGS. 3A and 3Billustrate an example of a micro-optic security device and angular control over a visible display provided by micro-optic security devices according to some embodiments of this disclosure. For convenience of cross-reference, structures common to bothFIGS. 3A and 3Bare similarly numbered

Referring to the non-limiting example ofFIGS. 3A and 3B, a first view301(shown inFIG. 3A) and a second view351(shown inFIG. 3B) of a security document305(for example, security document200inFIG. 2) are shown. According to various embodiments, security document200comprises a micro-optic security device310(for example, micro-optic security device205inFIG. 2), which exhibits absolute registration. As shown in the illustrative example ofFIGS. 3A and 3B, security document305is held by a viewer's right hand and maintained in a substantially planar condition such that the viewing angle can be expressed as one or more of a vector or a set of angular coordinates relative to a coordinate system315. While in this non-limiting example, coordinate system315is a three-dimensional Cartesian coordinate system, other coordinate systems for expressing the viewing angle of security document305and micro-optic security device310are possible and within the contemplated scope of this disclosure. For example, in certain embodiments, to account for curvature, local regions of micro-optic security device310(in one example, 1 mm square sections) could be assigned a coordinate system which approximates local flatness. Accordingly, each point of the security device could be assigned a unique viewing vector in a 3-dimensional space.

As shown in the illustrative example ofFIGS. 3A and 3B, in first view301, security document305and micro-optic security device310are held such that the viewer is looking at micro-optic security device310at a first predetermined viewing angle, shown in the figure as Θ1. When viewed at Θ1, the focusing elements of micro-optic security device310provide a synthetically magnified image of the portions of the focusing elements' footprints (for example, image icon260inFIG. 2), comprising visual information associated with a first humanly visible display320.

According to certain embodiments, in second view351, security document305and micro-optic security device310are held such that the viewer is looking at micro-optic security device310at a second predetermined viewing angle, shown in the figure as Θ2. When viewed at Θ2, the focusing elements of micro-optic security device310provide a synthetically magnified image of the portions of the focusing elements' footprints (for example, image icon265inFIG. 2), comprising visual information associated with a second humanly visible display360. In contrast to certain micro-optic systems which only exhibit aggregate registration, the absolute registration between the focusing elements and image icons of micro-optic security device310means that viewing angles Θ1and Θ2associated with first humanly visible display320and second humanly visible display360are predetermined in a coordinate system (for example, coordinate system315). By contrast, in a system with only aggregate registration, while the difference between Θ1and Θ2(for example, a quantification of the change in viewing angle needed to produce a switch from first humanly visible display320and second humanly visible display360) may be predetermined, uncertainty regarding the positions of image icons within the footprints of focusing elements means that the values of Θ1and Θ2are not predetermined. By contrast, certain micro-optic systems according to embodiments of this disclosure exhibit absolute registration between image icons and focusing elements, which, amongst other things, catalyzes a heightened degree of angular control over the presentation of humanly visible displays by the micro-optic system.

FIGS. 4A and 4Billustrate certain technical challenges associated with achieving angular control over visible displays in some micro-optic security devices. For convenience of cross-reference, structures common to bothFIGS. 4A and 4Bare numbered similarly.

Referring to the non-limiting example ofFIGS. 4A and 4B, a first view400(shown inFIG. 4A) of a refractive focusing element401, which is positioned on a first side of an optical spacer403. A structured image icon layer405is positioned on a second side of optical spacer403. Dashed lines407aand407bshow the boundaries of the footprint of focusing element401. While in this illustrative example, the footprint of focusing element401is co-extensive with the perimeter of focusing element401, other embodiments, wherein the footprint is larger or smaller than focusing element401are possible and within the contemplated scope of this disclosure.

According to certain embodiments, structured image icon layer405comprises a layer of material with which defines a pattern of recesses, posts, mesas and other structures in the material. In various embodiments, the structures of structured image icon layer405position and retain subsequently applied (for example, by doctor blading resin into the voids in structured image icon layer405) pigmented material, which fills the negative spaces in structured image icon layer. Referring to the non-limiting example ofFIGS. 4A and 4B, a region409of pigmented material is shown as being retained within structures of structured image icon layer405, and occupying a position at a first offset411to the right hand boundary407bof the footprint of focusing element401.

Referring to the non-limiting example ofFIGS. 4A and 4B, in certain embodiments, light which passes through a lensing surface413of focusing element at a first viewing angle Θais focused by focusing element401upon region409of pigmented material. As used in this disclosure, the term “lensing surface” encompasses both curved boundaries between regions of dissimilar indices of refraction (for example, in systems using refractive focusing elements) and curved regions of reflective material (for example, in systems using reflective focusing elements). According to certain embodiments, focusing element401is part of a larger, planar array of similar focusing elements, and structured image icon layer405is likewise part of a larger array of image icons. In some embodiments, the planar array of focusing elements (which includes focusing element401) and the larger array of image icons (which includes structured image icon layer405), synthetically magnify portions of the image icon layers to create a humanly visible display.

Second view450(shown inFIG. 4B) illustrates some of the technical challenges associated with achieving angular control over humanly visible displays provided by micro-optic systems in which registration of the pigmented image icons to the focusing elements relies exclusively on retaining pigmented material within structures of a structured image icon layer. As noted elsewhere in this disclosure, focusing elements according to certain embodiments of this disclosure have diameters of between 5 μm to 50 μm, with comparatively sized footprints. Given the scale of focusing elements' footprints, controlling the range of angles at which an image icon is visible through a particular focusing element requires positioning the image icon with micron or sub-micron accuracy. While it is possible to achieve micron and sub-micron control of the relative distances between structures within a structured icon layer (e.g., achieving aggregate registration), reliably positioning a structured image icon layer with micron or sub-micron accuracy relative to the footprints of an array of micro-optic focusing elements remains a significant technical challenge.

The technical challenges associated with registering a structured icon layer relative to specific locations within the footprint of a focusing element are shown with reference to second view450. As shown in second view450, due to for example, limited manufacturing tolerances or other confounding factors affecting the precision with which a structured icon layer relative to an array of focusing elements, structured image icon layer405is shifted by a small distance Δ, with the effect that region409is positioned at a new, second offset421relative to the right-hand boundary407bof the footprint of focusing element401. As a result of being positioned at a new coordinate within the footprint of focusing element401, to be focused on region409, light passing through the lensing surface413of focusing element401must be angled at a different angle Θbto be focused on region409. In practical terms, the net effects of the uncertainty in the registration between the location of region409within the footprint of focusing element401include that the angle at which a humanly visible display in which region409contributes is not predetermined.

FIGS. 5A.5B and5C illustrate, from three different points of view, an example of passing structured light through a focusing element at a predetermined location within the focusing element's footprint according to various embodiments of this disclosure. For convenience of cross-reference, elements common to more than one figure ofFIGS. 5A-5Care numbered similarly.

According to certain embodiments of this disclosure, the technical challenges associated with achieving absolute registration and attaining angular control over the presentation of humanly visible synthetically magnified displays can be overcome. In certain embodiments according to this disclosure, structured light is projected from projection angles corresponding to predetermined range of viewing angles at the lensing surfaces of focusing elements of a planar array of focusing elements, wherein the structured light is focused by the focusing elements of the planar array of focusing elements upon regions of uncured light-curable material within the footprints of the focusing elements of the planar array of focusing elements. Subsequently, the uncured light-curable material is removed (for example, with a spray wash) or chemically deactivated, such that only the cured regions of the light curable material are visible through the focusing elements at the predetermined range of viewing angles. In this way, the technical challenges associated with registering a structured icon layer to a specified location relative to the footprints of the focusing elements of the planar array of focusing elements are bypassed, and a micro-optic system exhibiting absolute registration can be produced.

Referring to the non-limiting example ofFIGS. 5A-5C, a side view (FIG. 5C), an underside view (FIG. 5A) and an angled view (FIG. 5B) of a refractive focusing element501, which is positioned on a portion of an optical spacer503, is provided by the figure. According to certain embodiments, focusing element501is affixed to optical spacer503and has a fixed relationship to the surfaces of optical spacer503. In certain embodiments, the fixed relationship between focusing element501and the surfaces of optical spacer503is achieved by applying a layer of light-curable material to optical spacer503, embossing the layer of light-curable material to form a lensing surface and curing the material in situ. In some embodiments, the fixed relationship between focusing element501and the surfaces of optical spacer503is achieved by forming both focusing element501and optical spacer from a common layer of light-curable material, and curing the formed layer to create an integrated focusing element-optical spacer combination.

Focusing element501is associated with a footprint505, which according to some embodiments, is coextensive with the perimeter of focusing element501. According to some embodiments, footprint505is smaller than the perimeter of focusing element501. In certain embodiments, footprint505describes an area which is larger than the perimeter of focusing element501.

As shown in the illustrative examples ofFIGS. 5A-5C, structured light (for example, collimated light, light from a projector, or light which has been passed through another array of focusing elements) is projected at the lensing surface of focusing element501at an angle (or a range of angles) associated with a predetermined viewing angle, which is shown in the figure as Θc. The lensing action of focusing element501focuses the incident light in a region520within footprint505. By using the structured light passing through focusing element501to create an image icon comprising a region of cured light curable material proximate to region520, a micro-optic system with absolute registration according to various embodiments of this disclosure can be produced.

WhileFIGS. 5A-5Cillustrate certain aspects of achieving angular control of a humanly visible synthetically magnified image in a micro-optic system using refractive focusing elements, embodiments according to this disclosure are not so limited, and other configurations of focusing elements, such as, for example, reflective focusing elements. Additionally, in some embodiments according to this disclosure, optical spacer503can be omitted, and a fixed relationship between a mounting surface for an image icon and a lensing surface of a focusing element can otherwise be achieved. For example, depending on the geometry and index of refraction of a plano-convex lens, the planar side of a plano-convex lens can define a surface having a fixed relationship to the lensing surface of the focusing element, upon which an image icon with absolute registration can be formed.

FIGS. 6A-6Cillustrate operations of a method for creating image icons of an arrangement of image icons with absolute registration according to certain embodiments of this disclosure. For convenience of cross-reference, structures common to more than one ofFIGS. 6A-6Care numbered similarly.

Referring to the non-limiting example ofFIGS. 6A-6C, a focusing element601of a planar array of focusing elements in a micro-optic security device (for example, plurality of focusing elements105and micro-optic system100inFIG. 1) is shown as being positioned on an optical spacer603, such that focusing element601has a fixed relationship with the bottom surface605of optical spacer603. At a first operation620(shown inFIG. 6A) of a method for creating image icons with absolute registration an uncured layer of light-curable material615is applied to bottom surface605of optical spacer603. In some embodiments, in performing operation620, light-curable material615is applied in all the footprints of focusing elements of the array of focusing elements of which focusing element601is a member. In various embodiments, light-curable material615is applied to only a subset (e.g., a partial layer) of the footprints of focusing elements of the array of focusing elements of which focusing element601is a member. As part of operation620, structured light associated with a pattern (for example, a pattern corresponding to the features of a humanly visible display provided by the micro-optic security system) is projected from a first predetermined range of viewing angles (Θdto Θe) at a lensing surface607of focusing element601. In some embodiments, focusing element601focuses the light at a focal point609, and the interaction between the focused light and uncured layer of light-curable material615creates a region613of cured light-curable material forming all or part of an image icon of an arrangement of image icons. According to certain embodiments, region613of cured light-curable material has a focally tapered sidewall profile. As used in this disclosure, the term “focally tapered” encompasses reduction in the cross section of a region of cured light-curable material towards a focal point of a focusing element. When viewed under a microscope, focally tapered image icons may appear to have a “gumdrop” like shape.

As shown in the illustrative example ofFIGS. 6A-6C, at operation630(shown inFIG. 6B), uncured light-curable material is removed from the bottom surface605of optical spacer603, leaving an image icon631. In some embodiments, the uncured light-curable material is deactivated to visibly contrast with image icon631. As image icon631occupies a predetermined position within the footprint of focusing element601, it is visible through focusing element601through the first predetermined range of viewing angles (i.e., Θdto Θe). Further, because image icon631occupies a predetermined position within the footprint of focusing element601, it is not visible through focusing element601through a second predetermined range of viewing angles. Put more simply, by creating image icon631by passing the curing light through the focusing element, angular control over the visibility (e.g., absolute registration) is achieved in certain embodiments according to this disclosure.

Referring again to the non-limiting example ofFIGS. 6A-6C, at operation640(shown inFIG. 6C), a protective layer645of light-curable material is applied in the regions outside of image icon631and flood-cured. According to various embodiments, protective layer645helps maintain the registration of image icons relative to a predetermined location within the footprint of focusing element601, by filling the spaces between image icons, thereby reducing the image icons' freedom of movement, and making it harder to dislodge the image icons from the surface to which they are attached. Further, in some embodiments, protective layer645also enhances the ruggedness of the micro-optic system by creating a retaining matrix which helps resist separation of image icon631from bottom surface605of optical spacer603during handling (for example, in a reel-to-reel process) and attachment to a substrate (for example, substrate150inFIG. 1).

FIGS. 7A and 7Billustrate operations of a method for creating a second image icon within the footprint of a focusing element according to various embodiments of this disclosure. For convenience of cross-reference elements common to both ofFIGS. 6A and 6Bare similarly numbered. According to certain embodiments, a second image icon within the footprint of a focusing element can contribute the operation of a micro-optic security device in multiple ways.

As a first example, where a first image icon is of a first color, placing a second image icon of a second color at a position within the footprint of a focusing element near the first image icon can, when aggregated over a plurality of focusing elements and image icons, create regions in a synthetically magnified humanly visible display of a third color, where the third color is a mixture of the first two colors. As one example, a humanly visible display with red, blue and purple regions can be created using only red and blue image icons.

As a second example, placing a second image icon within the footprint of a focusing element, when aggregated over a plurality of focusing elements and second image icons, can be done to support a micro-optic security device in providing a second (or multiple) humanly visible displays which are visible and invisible at predetermined ranges of viewing angles. According to certain embodiments, absolute registration of image icons within the footprints of focusing elements permits creating pluralities of humanly visible displays, each of which is visible at a narrow, predetermined range of viewing angles, which can create the appearance of a humanly visible display which appears to be constantly moving (for example, by rotating) or changing shape.

Referring to the non-limiting example ofFIGS. 7A and 7B, two operations of a method for creating a second image icon of a second color within the footprint703of a focusing element705are shown. According to certain embodiments, at operation701(shown inFIG. 7A), a fresh layer707of uncured light curable material of a second color relative to first image icon713, is applied to a surface709(in this case, the underside of optical spacer711) which has a fixed relationship to focusing element705, and upon which a first image icon713has already been formed. According to certain embodiments, the light curable material of fresh layer707of uncured light curable material has the same characteristic color as first image icon713. In some embodiments, the light curable material of fresh layer707of uncured light curable material has a different characteristic color than first image icon713.

In some embodiments, as part of operation701, structured light of a pattern of structured light (for example, a pattern corresponding to visible features of a second humanly visible display) is projected from a second predetermined range of viewing angles (shown in the figure as the range from Θfto Θg) at lensing surface715of focusing element. As a result of passing structured light through focusing element705from the second predetermined range of viewing angles, a region717of cured light-curable material forming a second image icon is formed within footprint703.

According to various embodiments, at operation720(shown inFIG. 7B), the uncured light-curable material in layer707of light-curable material is removed (for example, by spray washing) or otherwise deactivated, leaving second image icon as a region of contrast which is visible through focusing element705at viewing angles in the second predetermined range of viewing angles, and which is not visible through focusing element705at one or more predetermined ranges of viewing angles outside of the second predetermined range of viewing angles.

Examples of micro-optic security devices according to various embodiments of this disclosure include micro-optic security devices comprising a planar array of micro-optic focusing elements and a first arrangement of image icons, each image icon of the first arrangement of image icons comprising a region of light-cured material, wherein the first arrangement of image icons is visible through the planar array of micro-optic focusing elements across a first predetermined range of viewing angles relative to the micro-optic security device, and wherein the first arrangement of image icons is not visible through the planar array of micro-optic focusing elements across a second predetermined range of viewing angles relative to the micro-optic security device. While in the non-limiting example ofFIGS. 7A and 7B, uncured light material of the first color (for example, material used to create image icon713is shown as being washed away after the formation of the first image icon, embodiments according to this disclosure are not so limited. In certain embodiments, multiple image icons associated with multiple viewing angles may be formed using light curable material of the first color without washing uncured material away between projecting light at different angles. In certain embodiments, uncured material of a first color is washed away to create space for uncured light curable material of a second color.

Examples of micro-optic security devices according to various embodiments of this disclosure include micro-optic security devices wherein the first arrangement of image icons is associated with a first characteristic color, and further comprising a second arrangement of image icons, each image icon of the second arrangement of image icons comprising a second region of light cured material, wherein the second arrangement of image icons is visible through the planar array of micro-optic focusing elements across a third predetermined range of viewing angles relative to the micro-optic security device, and wherein the second arrangement of image icons is not visible through the planar array of micro-optic focusing elements across a fourth predetermined range of viewing angles relative to the micro-optic security device.

Examples of micro-optic security devices according to various embodiments of this disclosure include micro-optic security devices wherein the second arrangement of image icons is associated with a second characteristic color.

Examples of micro-optic security devices according to various embodiments of this disclosure include micro-optic security devices wherein each image icon of the first arrangement of image icons is associated with a focusing element of the planar array of micro-optic focusing elements, wherein each image icon of the second arrangement of image icons is associated with a focusing element of the planar array of micro-optic focusing elements, wherein each focusing element of the planar array of micro-optic focusing elements has a footprint, and wherein the footprint of at least one focusing element of the planar array of micro-optic focusing elements comprises an image icon of the first arrangement of image icons and an image icon of the second arrangement of image icons.

Examples of micro-optic security devices according to various embodiments of this disclosure include micro-optic security devices wherein the first arrangement of image icons is disposed relative to the planar array of micro-optic focusing elements such that a portion of the planar array of micro-optic focusing elements forms a synthetic image of a portion of the first arrangement of image icons.

Examples of micro-optic security devices according to various embodiments of this disclosure include micro-optic security devices wherein each image icon of the first arrangement of image icons is associated with a focusing element of the planar array of micro-optic focusing elements, wherein each focusing element of the planar array of micro-optic focusing elements has a footprint, and wherein a plurality of image icons of the first arrangement of image icons are disposed at different locations within the footprints of their respective focusing elements to project at least one of a synthetic image, a three-dimensional image, an image with a movement effect, or an image with an animation effect.

Examples of micro-optic security devices according to various embodiments of this disclosure include micro-optic security devices wherein image icons of the first arrangement of image icons are disposed relative to the planar array of micro-optic focusing elements to create a flicker effect with a predetermined “on” period.

Examples of micro-optic security devices according to various embodiments of this disclosure include micro-optic security devices comprising one or more regions of light-cured protective material between image icons of the first arrangement of image icons.

Examples of micro-optic security devices according to various embodiments of this disclosure include micro-optic security devices wherein image icons of the first arrangement of image icons are not provided within a structured image icon layer.

Examples of micro-optic security devices according to various embodiments of this disclosure include micro-optic security devices wherein image icons of the first arrangement of image icons are provided within a structured image icon layer.

Examples of micro-optic security devices according to various embodiments of this disclosure include micro-optic security devices wherein focusing elements of the planar array of micro-optic focusing elements comprise refractive focusing elements.

Examples of micro-optic security devices according to various embodiments of this disclosure include micro-optic security devices wherein focusing elements of the planar array of micro-optic focusing elements comprise reflective focusing elements.

Examples of micro-optic security devices according to various embodiments of this disclosure include micro-optic security devices wherein image icons of the first arrangement of image icons comprise regions of light-cured material with focally tapered sidewall profiles.

Examples of micro-optic security devices according to various embodiments of this disclosure include micro-optic systems wherein the protective layer comprises a layer of adhesive material.

Examples of methods of manufacturing micro-optic systems according to various embodiments of this disclosure include methods comprising applying a layer of light-curable material to a first surface of the micro-optic system having a fixed relationship to a planar array of focusing elements, wherein the first surface is disposed proximate to one or more focal points of focusing elements of the planar array of focusing elements, directing a first pattern of structured light at a lensing surface of the planar array of focusing elements until a first portion of the layer of light-curable material is cured to form a first arrangement of image icons, and removing or deactivating uncured light-curable material from the first surface of the micro-optic system, wherein the first pattern of structured light is directed at the lensing surface of the planar array of focusing elements from a first predetermined range of viewing angles relative to the planar array of focusing elements.

Examples of methods of manufacturing micro-optic systems according to various embodiments of this disclosure include methods comprising directing a second pattern of structured light at the lensing surface of the planar array of focusing elements until a second portion of the layer of light-curable material is cured to form a second arrangement of image icons, wherein the second pattern of structured light is directed at the lensing surface of the planar array of focusing elements from a second predetermined range of viewing angles relative to the planar array of focusing elements.

Examples of methods of manufacturing micro-optic systems according to various embodiments of this disclosure include methods wherein image icons of the first arrangement of image icons are associated with a first characteristic color, and wherein image icons of the second arrangement of image icons are associated with a second characteristic color.

Examples of methods of manufacturing micro-optic systems according to various embodiments of this disclosure include methods wherein each image icon of the first arrangement of image icons is associated with a focusing element of the planar array of focusing elements, wherein each image icon of the second arrangement of image icons is associated with a focusing element of the planar array of focusing elements, wherein each focusing element of the planar array of focusing elements has a footprint, and wherein the footprint of at least one focusing element of the planar array of focusing elements comprises an image icon of the first arrangement of image icons and an image icon of the second arrangement of image icons.

Examples of methods of manufacturing micro-optic systems according to various embodiments of this disclosure include methods wherein the first arrangement of image icons is disposed relative to the planar array of focusing elements such that a portion of the planar array of focusing elements forms a synthetic image of a portion of the first arrangement of image icons.

Examples of methods of manufacturing micro-optic systems according to various embodiments of this disclosure include methods wherein image icons of the first arrangement of image icons are formed at predefined positions on the first surface of the micro-optic system relative to the planar array of focusing elements to create a flicker effect with a predetermined “on” period.

Examples of methods of manufacturing micro-optic systems according to various embodiments of this disclosure include methods comprising applying a layer of light-curable protective material to portions of the first surface in between image icons of the first arrangement of image icons and flood-curing the layer of light-curable protective material.

Examples of methods of manufacturing micro-optic systems according to various embodiments of this disclosure include methods comprising applying a protective layer of adhesive material to portions of the first surface in between image icons of the first arrangement of image icons.

Examples of methods of manufacturing micro-optic systems according to various embodiments of this disclosure include methods wherein image icons of the first arrangement of image icons are formed in a structured image icon layer.

Examples of methods of manufacturing micro-optic systems according to various embodiments of this disclosure include methods wherein image icons of the first arrangement of image icons are not formed in a structured image icon layer.

Examples of methods of manufacturing micro-optic systems according to various embodiments of this disclosure include methods wherein focusing elements of the planar array of focusing elements comprise refractive focusing elements.

Examples of methods of manufacturing micro-optic systems according to various embodiments of this disclosure include methods wherein focusing elements of the planar array of focusing elements comprise reflective focusing elements.

Examples of methods of manufacturing micro-optic systems according to various embodiments of this disclosure include methods wherein each image icon of the first arrangement of image icons is associated with a focusing element of the planar array of focusing elements, wherein each focusing element of the planar array of focusing elements has a footprint, and wherein a plurality of image icons of the first arrangement of image icons are disposed at different locations within the footprints of their respective focusing elements to create a synthetic image with a three-dimensional effect.

Examples of methods of manufacturing micro-optic systems according to various embodiments of this disclosure include methods wherein an image icon of the first arrangement of image icons is formed with a focally tapered sidewall profile.