Patent Application
20140268327
1. Field
The disclosed concept relates generally to optically variable devices and, more particularly, to an optically variable device that exhibits non-diffractive three-dimensional optical effects.
2. Description of Related Art
An optically variable device (OVD) is a visual device that creates a change or shift in appearance, such as, for example and without limitation, a change in color, when observed from different relative observation points or when the illuminating light changes to a different angle of incidence. The evolution of the OVD as a security device stems largely from the search for a mechanism to resist counterfeiting of certain articles and products, or alternatively to render such copying obvious. For example, and without limitation, paper money, banknotes, certificates, tax stamps, security labels, product hang tags, drivers' licenses, ID cards, and credit cards, among other things, frequently employ one or more OVD's to resist counterfeiting or to verify authenticity.
U.S. Pat. No. 6,266,187 discloses a substrate that exhibits a non-diffractive three-dimensional optical effect. The substrate includes stereo pairs of elements formed on the substrate that reflect or refract light to a focal point that is spaced apart from the surface of the substrate. This creates a point image at the focal point that is visible to a viewer. By using multiple stereo pairs of elements, a three-dimensional image is formed.
In U.S. Pat. No. 6,266,187, the stereo pairs of elements only include a straight angled reflecting surface or a semi-circular shaped reflecting element. As such, the range of optically variable effects that can be provided is limited.
Notwithstanding the advancements disclosed in U.S. Pat. No. 6,266,187, the continuous introduction of additional unique effects is needed to stay ahead of the counterfeiters' ability to simulate OVD technologies. Thus, there is still a need for an OVD that provides discernible optical features, but is difficult for a counterfeiter to duplicate or simulate.
It is an object of the present disclosure, therefore, to satisfy this need by providing an OVD that provides strong, stable, and easily discernible optical effects. It is a further object of the present disclosure to satisfy this need by providing an OVD that is more difficult to copy or simulate than the prior art, and thus to provide a security device with a higher level of security.
These needs and others are met by embodiments of the disclosed concept, which provides an OVD capable of providing various non-diffractive three-dimensional optical effects.
In accordance with aspects of the disclosed concept, an optically variable device includes: a substrate; and a plurality of optical elements formed in or on the substrate and being structured to provide a non-diffractive three-dimensional optical effect for a viewer when light is incident on the optical elements, wherein the plurality of optical elements are arranged as a plurality of stereo pairs structured to reflect or refract light to corresponding focal points in three-dimensional space apart from the optically variable device to form the three-dimensional optical effect, wherein the optical elements include one or more optical elements that are curved structures having a curvature that is either less than or greater than a semi-circle.
In accordance with aspects of the disclosed concept, an optically variable device includes: a substrate; and a plurality of optical elements formed in or on the substrate and being structured to provide a non-diffractive three-dimensional optical effect for a viewer when light is incident on the optical elements, wherein the plurality of optical elements are arranged as a plurality of stereo pairs structured to reflect or refract light to corresponding focal points in three-dimensional space apart from the optically variable device to form the three-dimensional optical effect, wherein the three-dimensional optical effect includes one or more point images that change intensity when the substrate is rotated.
In accordance with aspects of the disclosed concept, an optically variable device includes: a substrate; and a plurality of optical elements formed in or on the substrate and being structured to provide a non-diffractive three-dimensional optical effect for a viewer when light is incident on the optical elements, wherein the plurality of optical elements are arranged as a plurality of stereo pairs structured to reflect or refract light to corresponding focal points in three-dimensional space apart from the optically variable device to form the three-dimensional optical effect, wherein one or more of the optical elements includes a micro-patterned surface that causes at least a portion of the three-dimensional optical effect to include a color effect.
A full understanding of the disclosed concept can be gained from the following description of the preferred embodiments when read in conjunction with the accompanying drawings in which:
As employed herein, the term “optically variable device” (OVD) is used in its conventional broad sense and includes devices comprising a single optical element alone or multiple optical elements arranged so that they may or may not be touching each other, overlapping, or physically in close proximity to each other.
A “security device” as employed herein, refers to any known or suitable device which employs one or more OVD's in order to verify the authenticity of the article on which the security device is disposed, and to deter and resist copying or counterfeiting of the article.
As employed herein, the term “article” refers to an item or product on which the exemplary OVD, or security device comprising the OVD, is employed, and expressly includes, without limitation, articles used in high-security, banking, identification, and brand protection markets, such as, for example, identification cards, credit cards, debit cards, smart cards, organization membership cards, security system cards, security entry permits, banknotes, checks, fiscal tax stamps, passport laminates, legal documents, packaging labels and other information-providing articles wherein it may be desirable to validate the authenticity of the article and/or to resist alteration, tampering or reproduction thereof.
The focal point 4 is disposed at a location apart from the surface of the substrate 1.
A viewer viewing the OVD is able to see a point image at the location of the focal point 4 when the OVD is viewed from a limited range of angles of elevation. The angle of elevation is between the surface of the OVD and the viewpoint of the viewer. The range of angles of elevation at which the point image is visible is based on the cross-sectional profile shapes of the optical elements 2. In more detail, the cross-sectional profile shape of an optical element has an associated angle of divergence OA and θB and angle of elevation θD. Changing the cross-sectional shape of an optical element can cause the associated angles of divergence and elevation to change. In the OVD of
The point image formed by the optical elements 2 creates a non-diffractive three-dimensional optical effect. The effect is non-diffractive because it is caused by light being reflected, rather than diffracted, from the optical elements 2. Thus, the point image will generally appear the same color as the light incident on the OVD (i.e., an achromatic effect). In some embodiments of the disclosed concept, a micro-patterned surface can be employed to control the color of the point image as will be described in more detail with respect to
In the OVD of
As shown in
Referring to
Generally speaking, as the curvature of the cross-sectional profile shape of an optical element increases, the range of angles of elevation in which the associated point image is visible increases and the intensity of the associated point image decreases. It is contemplated that an OVD may employ stereo pairs of optical elements having different curvatures to control the three-dimensional optical effect. For example, optical elements having a small curvature can be used to create one portion of a three-dimensional image, and that portion would only be viewable from points within a narrow range of angles of elevation. Optical elements having a larger curvature can then be used to create the rest of the three-dimensional image, which would then be viewable from points within a larger range of angles of elevation. Having a certain portion of the three-dimensional image only becoming visible within a certain range of angles of elevation, or having different three-dimensional images visible within different ranges of angles of elevation, can be used as a security feature of the OVD.
The optical elements 62, 64, 66 each are formed as grooves having straight edges. However, the straight edges of the grooves can cause a diffractive effect. Optical element 68 has non-uniform edges which reduce or eliminate the diffractive effect. It is contemplated that non-uniform edges can be employed with any of the optical elements disclosed herein without departing from the scope of the disclosed concept. It is also contemplated that the optical elements described herein are not limited to straight grooves or ridges, but instead can take any desired shape, such as the optical elements 69 that are formed as curved grooves in the substrate 60.
The horizontal planes of the micro-patterned surface 83 may be created by partial exposure of a suitable substrate material using a method such as, for example and without limitation, laser engraving, electron beam lithography, ion beam etching, or etching, such as, chemical or plasma etching. The horizontal planes of the micro-patterned surface 83 may also be created using growth methods such as, for example and without limitation, nano-metallization or electroforming. It is also contemplated that the vertical distances between the horizontal planes may be irregular and may be made, for example and without limitation, successively increasing or decreasing adjacent plane heights.
Vertical distances between horizontal planes in micro-patterned surfaces 83 may be controlled to produce varied and controllable color effects such as, for example and without limitation, pastel color effects, directional color effects, and color switching effects. Micro-patterned surfaces 83 may be employed in combination with any of the optical elements described herein without departing from the scope of the disclosed concept to create a three-dimensional image. Adding micro-patterned surfaces 83 allows color effects such as those described herein which are visible for certain parts of the image or at certain angles of view.
The vertical distance between the horizontal planes of the micro-patterned surface can be achieved by any suitable structure. In
The cross-sectional profile shape of the optical element 82 includes the angled micro-patterned surface 83 and a curved surface 84. The disclosed concept is not limited thereto. It is contemplated that the micro-patterned surface 83 may be employed to any or all portions of an optical element without departing from the scope of the disclosed concept. It is also contemplated that the micro-patterned surface 83 may be employed on any shape of optical element surface without departing from the scope of the disclosed concept. For example, in
It is contemplated that any of the optical elements described herein, or any combinations or variations thereof, may be employed in an OVD to create a non-diffractive three-dimensional optical effect.
It is contemplated that the optical elements described herein may be produced by any suitable method by the removal of or by the addition of material. Optical elements formed by the addition of material, for example and without limitation, the ridge shaped optical elements 32, 42 of
Optical elements formed by the removal of material, for example and without limitation, the recessed-type optical elements 12, 22, 52 of
Once formed, optical elements may have their reflectivity enhanced with reflective coatings such as, for example and without limitation, print materials, vacuum deposition layers, or liquid crystal layers.
The optical elements described herein may be formed on any suitable substrate. For embodiments comprising elements formed by the addition of material, the substrate may comprise any convenient surface suitable for the addition process and reflective material chosen. For example, substrates which may be usefully employed by printing a reflective lacquer may include, for example and without limitation, plastic, paper, glass or metal. For embodiments comprising elements formed by the removal of material, the substrate may comprise any convenient surface on which a surface relief can be formed, for example and without limitation, plastic, paper, glass or metal, but is preferably a plastic film or foil. Films such as polyethylene, polyimide, OPP, PET may be preferably used.
The dimensions of the optical elements and the spacing between them is preferably greater than those associated with diffraction effects so that dispersion color effects are limited. Diffraction effects can also be limited by creating some irregularity to the pattern of the multiple optical elements that form the three-dimensional image. The shape of the individual optical elements (e.g., groove or ridge edges) may be straight, curved, or irregular. Increasing the size of the optical elements eases some mass production problems. However, as the optical elements are increased in size, the fidelity of the resultant three-dimensional image is reduced. It has been found that optical elements having sizes of, without limitation, 2 to 5 microns are compatible with standard mass production techniques and are not limited to embossing or cast curing. For other applications such as print applications, the optical elements would be larger and would preferably have dedicated sizes and shapes to optimize the print quality commensurate with the specific print application.
Once formed, the optical elements may then be mass replicated by first replicating the surface of the substrate in nickel metal by means of electroforming. The nickel surface may then be used as a durable tool to replicate the relief surface in other substrates by means such as, for example and without limitation, embossing via heat and pressure, molding, casting, casting and cross-link curing or other such means.
An optical pattern or image may be designed to include pairs of optical elements of various shapes, sizes, degrees of symmetry, and formation process, each contributing its particular optical effect to the viewable image. Such elements may be formed in one or multiple passes, and in register or out of register.
Further, in all embodiments the orientation of the structure on the substrate surface can be varied to create gradual changes in the viewed image as a function of the positions of the light source and observer. In this way a small and local change can vary over a wide range of orientations creating a kinetic movement or animation effect.
By a combination of the multiple embodiments disclosed above, complex optical imagery may be produced precisely suited for use as high-security OVD's and security devices comprising such OVD's.
An adhesive layer may be present on either surface of the substrate as a means to attach the OVD to an article. It is also contemplated that a protective layer may be added.
It is also contemplated that any of the optical elements described herein may be employed in an OVD that is employed as part of a security device or an article comprising such a security device.
Security devices may be created by incorporating the OVD into a configuration that can be affixed to or embedded into an article to be authenticated. For example, and without limitation, the OVD can be incorporated into a security label, thread, patch, laminate or transfer film. Alternatively, the OVD may be formed directly into an article to be protected, such as the case with an optical disk.
Such security devices may then be affixed to or embedded into an article to be authenticated. End-users of the article may verify the authenticity of the article by examining the OVD and confirming that the predetermined optical pattern or image is present.
While specific embodiments of the disclosed concept have been described in detail, it will be appreciated by those skilled in the art that various modifications and alternatives to those details could be developed in light of the overall teachings of the disclosure. Accordingly, the particular arrangements disclosed are meant to be illustrative only and not limiting as to the scope of the invention which is to be given the full breadth of the appended claims and any and all equivalents thereof.
This patent application claims the priority benefit under 35 U.S.C. §119(e) of U.S. Provisional Application No. 61/787,313 filed on Mar. 15, 2013, and entitled, “OPTICALLY VARIABLE DEVICES AND AN ASSOCIATED METHOD,” the contents of which are hereby incorporated herein by reference.
| Number | Date | Country | |
|---|---|---|---|
| 61787313 | Mar 2013 | US |
