Patent Description:
An example of currently used systems can be found in <CIT>. Which discloses a screen that displays images by reflecting projection light includes a transparent layer that transmits visible light and a plurality of linear reflection portions that are supported by the transparent layer and reflect the projection light. The reflection portions are arranged so as to be distanced from one another as viewed in the thickness direction of the screen. Each reflection portion has a reflection surface for reflecting the projection light, the reflection surface being tilted with respect to the thickness direction of the screen. The distance between the reflection surfaces adjacent in a direction orthogonal to the lines of the reflection portions as viewed in the thickness direction of the screen is <NUM> or more.

Fresnel lenses are increasingly used as decorative elements in product packaging, for example, in packaging for consumer goods such as DVD covers, tissue boxes, toiletry items, toys, and more. These Fresnel lenses can be incorporated into decorative films to create a desirable reflective metallic, textured, or "bubbled," appearance. The thickness of such Fresnel lenses can be between about <NUM> microns and about <NUM> microns. Producing even thinner Fresnel lenses can be desirable because some thinner substrates, such as some types of thin product packaging, cannot adequately support typical Fresnel lenses. Additionally, thinner Fresnel lenses may potentially use less material to produce and therefore may be lower cost than typical Fresnel lenses.

Accordingly, there is a need for methods of producing thin Fresnel lenses.

The drawings herein may not be to scale.

Fresnel lenses can provide focusing, magnification, imaging etc. like a traditional concave or convex lens, however, a Fresnel lens can be made thinner with the use of facets. The Fresnel lenses have a relatively flattened spatial extent in comparison to traditional concave or convex lenses. <FIG> shows a cross-section of an example Fresnel lens <NUM>. <FIG> shows a first side and a second side of the Fresnel lens <NUM> referred to as the top side and the bottom side. The Fresnel lens <NUM> includes a plurality of facets <NUM>. The facets <NUM> are disposed on the first side (e.g., top side) on a top surface <NUM> and are closer to the first side (top side) than to the second side (bottom side) and bottom surface <NUM>. Accordingly, the term top side may be referred to as the side where the facets are formed or are closest, in comparison to the bottom side.

As illustrated in <FIG>, Fresnel lenses <NUM> may comprise a plurality of concentric or circular rings <NUM>, also referred to as facets or elements. These rings or annular elements <NUM> may be circular or possibly stretched in one direction (e.g., elliptical) and may comprise may comprise refractive (or reflective) surfaces having local curvature and/or facet inclination/declination similar to that of a corresponding plano-convex or plano-concave refractive lens (or reflective mirror) so as to refract (or reflect) light in a manner similar to such a conventional non-Fresnel lens (or mirror). The Fresnel lens <NUM>, however, can be made thinner than the corresponding plano-convex or plano-concave (non-Fresnel) lens by removing much of the thickness of the lens. The Fresnel lenses rings, facets or elements <NUM> can be formed on the surface <NUM> of a layer of material <NUM>. The layer of material <NUM> can be optically reflective, or can be optically transmissive or transparent. The Fresnel lens <NUM> can thus provide optical power similar to a conventional lens or mirror. This optical power results from refraction or reflection of light from the facets <NUM>. The Fresnel lens <NUM> however can be thinner than non-Fresnel lens based optical elements.

As discussed above, producing thinner Fresnel lenses <NUM> may be advantageous because some thinner substrate carriers, such as some types of thin product packaging, may not be able to adequately support the Fresnel lenses. Additionally, thinner Fresnel lenses <NUM> may use less material to produce and therefore can be lower cost than typical Fresnel lenses.

Thinner Fresnel lenses <NUM> may be fabricated by scaling down the size of the facets <NUM> or facet spacing. However, if the facets <NUM> are scaled down, as the thickness of a Fresnel lens <NUM> decreases, the spacing <NUM> between the facets that make up the Fresnel lens or optical element will also decrease. Accordingly, if the Fresnel lens thickness and thus the height <NUM> of the facets <NUM> is reduced too much, then the space <NUM> between each facet will become small enough to cause visible dispersion. In particular, the spacing <NUM> between the facets <NUM> will be at a size such that the facets diffract visible light resulting in wavelength dispersion and a resultant rainbow color effect. This dispersion of incident light can cause undesirable colors (such as a rainbow of colors) to be visible and can reduce or impair the desired achromatic or "metallic" look of the Fresnel lens. Accordingly, there is a need for Fresnel lenses <NUM> that are thinner, but that do not produce undesirable wavelength dispersion and the resultant colors and that can maintain their desirable achromatic or "metallic" look.

The average lateral dimension, or spacing <NUM> of each of the Fresnel rings <NUM>, for example, can be from <NUM> micron to <NUM> microns, e.g., between about <NUM> microns to about <NUM> microns or larger in some cases. As illustrated in <FIG> and <FIG>, this lateral dimension <NUM> is in the direction parallel, for example, to the x (or y) axes and in the horizontal direction (as opposed to, for example, the direction parallel to the z axis and in the vertical direction). The average lateral spacing <NUM> may also be referred to as the frequency or period of the Fresnel lens <NUM>. The Fresnel rings <NUM> have a height or depth <NUM> in the vertical direction (shown in <FIG> as parallel to the z axis). In some cases, the height <NUM> may be maintained constant and the spacing <NUM> may change, for example, with radial distance from the center of the Fresnel rings <NUM> and Fresnel lens <NUM> toward the periphery. For example, the spacing <NUM> may be larger at the center and progressively get smaller at the edges or periphery. As a result, the facet angle, α, may increase with radial distance from the center. With larger spacing <NUM>, the Fresnel lens <NUM> may be achromatic and not produce diffraction of visible light that creates a rainbow effect. In contrast, for a Fresnel lens <NUM> having a minimum spacing <NUM> less than, for example, about <NUM> microns incident visible light may be undesirably diffracted by the Fresnel rings <NUM> and this diffraction may be wavelength dependent, causing different colors to be diffracted by different amount. As a result, colored light may be visible. Likewise, this dispersion can cause the Fresnel lens <NUM> to appear colored (e.g., a rainbow of colors may be observable) as opposed to the typically desired achromatic or metallic appearance, where substantially no color dispersion of incident light occurs. These colors caused by the dispersion may be a prominent feature observable to the viewer.

For certain Fresnel lenses, the average spacing <NUM> of each of the Fresnel rings or elements <NUM> is related to the height <NUM>, also referred to as the facet height or facet depth, of the of each of the Fresnel elements <NUM>. For example, decreases in the height <NUM> of the Fresnel elements <NUM> by making the lens smaller are associated with a related decrease in the average spacing <NUM>. Accordingly, to decrease the facet height <NUM> of the Fresnel lens <NUM> below a certain desired threshold, about <NUM> microns or <NUM> micron, for example, the size of the Fresnel lens may be scaled down causing the minimum spacing <NUM> to be below the spacing at which color dispersion of incident light occurs as a result of diffraction.

Referring again to <FIG>, the surface elements <NUM> may comprise a plurality of concentric rings. The Fresnel lens <NUM> may be, for example, about <NUM> to <NUM> inches, for example, <NUM> to <NUM> inches or larger in diameter <NUM> or any range or combination or ranges defined by any of these values. The facet height <NUM> may be, for example, from about <NUM> microns or <NUM> micron to <NUM> microns, e.g., from about <NUM> to about <NUM> microns or larger, in some cases. For the Fresnel lens <NUM>, including a plurality of annular elements <NUM>, the primary optical facet angle, α, <NUM>, may vary monotonically with respect to the distance of the element <NUM> from the center of curvature of the circular element <NUM> (or varies monotonically with respect to the radius of curvature of the element <NUM> and/or distance from the center of the Fresnel lens) although the configuration need not be so limited. In some embodiments the Fresnel lens <NUM> may have a focal length (and corresponding f-number). In some cases, both the height <NUM> and the spacing <NUM> vary together, for example, to maintain a focal length of the Fresnel lens <NUM>. The variation of the primary optical facet angle, α, <NUM>, can be monotonically increasing or decreasing with respect to the radius of curvature of the element <NUM>. For example, the primary optical facet angle, α, <NUM> can vary quadratically or parabolically with respect to the radius of curvature of the element <NUM>. The primary optical facet angle, α, <NUM> can vary as a polynomial function (e.g., Bessel or Zernike polynomial function) with respect to the radius of curvature of the element <NUM>. The variation in the primary optical facet angle, α, <NUM>, however, is not so limited and may vary according to other profiles and need not be monotonically increasing or decreasing.

The variation in the primary optical facet angle, α, <NUM>, can be produced by variation in the spacing <NUM> of the Fresnel rings or elements <NUM> or variation in the height <NUM> of the Fresnel rings or elements <NUM> of both. For example, the spacing <NUM> of the Fresnel rings or elements <NUM> can change, e.g., increase or decrease, while the height <NUM> of the Fresnel rings or elements <NUM> generally remains constant. The spacing <NUM> of the Fresnel rings or elements <NUM> may monotonically increase or decrease with respect to the radius of curvature of the element <NUM> while the height or depth of the Fresnel rings or elements remains substantially constant. As a result, the primary optical facet angle, α, <NUM>, may change, increase or decrease, for example, monotonically increase or decrease respect to the radius of curvature of the element <NUM> and/or distance from the center of the Fresnel lens toward the periphery. Such variation may be configured to provide for the focal length of the Fresnel lens.

As illustrated in <FIG>, an optical element <NUM>, may comprise an "ultra" thin optical element such as an ultra thin Fresnel lens comprising a plurality of rings or elements <NUM> formed on the surface <NUM> of a layer of material <NUM>. According to the invention, the element <NUM> comprises an angled facet portion 21A and a shallower portion or substantially horizontal portion 21B. As used herein, the term horizontal is used for reference only, however, such a portion 21B may not be oriented horizontally in use. In <FIG>, the horizontal direction is parallel to the x axis (or y axis) as designed by the x, y, z axes. In some embodiments, the shallower portion or substantially horizontal portion 21B may be substantially horizontal with respect to the surface of the layer or film <NUM> onto which the annular Fresnel element <NUM> is formed. In some embodiments, the top surface of the substantially horizontal portion 21B may be the top surface <NUM> of the layer or film <NUM> on which the Fresnel element <NUM> is formed. In various implementations, a plurality of elements <NUM> extend in a horizontal direction across the layer of material or film <NUM>.

In some implementations, the shallower portion or substantially horizontal portion 21B varies in size such as width WHoriz with position, for example, with distance from a location such as the center of the Fresnel lens or some other location. In some implementations, the shallower portion or substantially horizontal portion 21B varies in size as the facet size varies. For example, the shallower portion or substantially horizontal portion 21B may vary in size (e.g., width WHoriz) as the angled facet portion 21A varies such as width WFacet in size. In some implementations, the height or depth <NUM> remains constant as the shallower portion or substantially horizontal portion 21B and/or angled facet portion 21A varies in width WHoriz, WFacet.

The angled facet portion 21A of the Fresnel lens element <NUM> may have an optical facet angle α, <NUM>, which may be substantially similar to the optical facet angle α, <NUM> of the Fresnel lens, for example, described above with reference to <FIG>. Accordingly, in some implementations, the optical facet angle α, <NUM> of an annular Fresnel element <NUM> may vary monotonically with respect to the distance of the facet portion 21A from the center of curvature of an annular Fresnel element <NUM> (or varies monotonically with respect to the radius of curvature of the annular Fresnel element <NUM>). In some implementations, the variation of the primary optical facet angle, α, <NUM>, can be monotonically increasing or decreasing with respect to the radius of curvature of the annular Fresnel element <NUM> or distance, e.g., from the center of the optical element <NUM>. In some implementations, the primary optical facet angle, α, <NUM> can vary quadratically, parabolically, or as a polynomial function with respect to the radius of curvature of the annular Fresnel element <NUM> or distance, e.g., from the center of the optical element. The variation in the primary optical facet angle, α, <NUM>, however, is not so limited and may vary according to other profiles and need not be monotonically increasing or decreasing.

The variation in the primary optical facet angle, α, <NUM>, can be produced by variation in the spacing <NUM> of the Fresnel rings or elements <NUM> or variation in the height <NUM> of the Fresnel rings or elements <NUM> of both. For example, the spacing <NUM> of the Fresnel rings or elements <NUM> can change, e.g., increase or decrease, while the height <NUM> of the Fresnel rings or elements <NUM> generally remains constant. In some designs, for example, both the facet 21A and the substantially horizontal portion 21B can change with position, e.g., with distance from a location such as center of the Fresnel rings. Accordingly, the height <NUM> may remain substantially constant for some designs. The spacing <NUM> of the Fresnel rings or elements <NUM> may monotonically increase or decrease with respect to the center of curvature of the element <NUM>. The variation need not be monotonic though and can both increase and decrease. For example the spacing <NUM> may be larger at the center and progressively get smaller at the edges. As a result, the facet angle, α, <NUM>, may increase with radial distance from the center.

The shallower portion or substantially horizontal portion 21B may be oriented at an angle that is reduced compared to the optical facet angle α, <NUM>. The angle at which the shallower portion is oriented may be less than ½, <NUM>/<NUM>, <NUM>/<NUM>, <NUM>/<NUM>, <NUM>/<NUM>, or <NUM>/<NUM> than the optical facet angle α, <NUM>. The shallower portion 21B can be oriented at an even smaller angle. The angle at which the shallower portion 21B is oriented may be on average less than <NUM>°, less than <NUM>°, less than <NUM>° less than <NUM>° degree, less than <NUM>° degree. The shallower portion 21B may be <NUM>° degrees. The shallower portion 21B may be oriented on average at angles within any range formed by any of these values or may be outside these ranges. In some designs, the Fresnel lens or Fresnel element <NUM> could have a shallow portion 21B that is tilted or oriented at a larger angle than horizontal but that is less than the facet angle, α, <NUM>. In some designs, for example, the shallower portion 21B need not be horizontal and may be inclined (or decline) by amounts larger than <NUM>°, larger than <NUM>°, larger than <NUM>°, larger than <NUM>° degree, larger than <NUM>° degree, however, at a smaller angle than the optical facet angle, α, <NUM>.

The facet height <NUM>, also referred to as the facet depth <NUM>, of a Fresnel surface element <NUM> may be the vertical distance from the top surface <NUM> of the substantially horizontal portion 21B (or shallower portion) of the Fresnel surface element <NUM> to the bottommost point of the facet portion 21A of the Fresnel surface element <NUM>. The term bottom is being used herein for reference only and the bottommost point of the facet portion 21A may refer to the point of the facet portion 21A farthest from the topmost portion of the surface layer of material or film <NUM> on which the facet portion 21A is formed or with respect to the top of the optical element <NUM>. According to the invention, the facet depth <NUM> is on average less than about <NUM> microns, less than about <NUM> microns, less than about <NUM> microns, less than about <NUM> microns, less than about <NUM> microns, less than about <NUM> microns, less than about <NUM> microns, less than about <NUM> microns, less than about <NUM> microns, less than about <NUM> microns, less than about <NUM> microns, less than about <NUM> microns, less than about <NUM> microns, less than about <NUM> microns, less than about <NUM> microns, less than about <NUM> microns, less than about <NUM> microns, less than about <NUM> microns, less than about <NUM> microns, less than about <NUM> microns, less than about <NUM> microns, less than about <NUM> microns, less than about <NUM> microns, less than about <NUM> microns, less than about <NUM> microns, or less than about <NUM> microns or smaller. In some implementations, the facet depth <NUM> may be from about <NUM> microns to about <NUM> microns, from about <NUM> microns to about <NUM> microns, from about <NUM> microns to about <NUM> microns, or from about <NUM> micron to about <NUM> microns. The depth may be zero, for example, in the center of the Fresnel lens or element, or elsewhere. The average facet depth may be any value in any range formed by any of these values. Other values outside these ranges may also be possible but not falling within the scope of the invention.

In some implementations, the average facet depth <NUM> and the average spacing <NUM> of the annular Fresnel elements <NUM> may be decoupled. For example, a Fresnel element <NUM> may be formed in a layer of material or film <NUM> such that the facet depth <NUM> may be selected from a desired range, as described herein, while the average spacing <NUM> of the Fresnel elements <NUM> may remain the same or in the same range (e.g., that does not cause visible dispersion) for any desired facet depth <NUM> or independent of the facet depth <NUM>. In some embodiments, the average spacing <NUM> of the Fresnel lens elements (or grooves) <NUM> may be substantially the same as the average spacing <NUM> of a typical known Fresnel lens <NUM> that does not disperse incident light. According to the invention, the minimum spacing <NUM> of the Fresnel lens elements <NUM> is greater than or equal to about <NUM> microns, greater than about <NUM> microns, greater than about <NUM> microns, or greater than about <NUM> microns or greater. The average spacing <NUM> may be any value in any range formed by any of these values. Other values outside these ranges may also be possible but not falling within the scope of the invention.

In various implementation, however, the spacing may vary across the optical element or Fresnel lens. However, the spacing <NUM> may be sufficiently large to reduce the amount of visible dispersion or iridescence, e.g., such that the optical element or Fresnel lens is substantially achromatic or substantially without iridescence.

Although the angled facets 21A are shown as planar in <FIG>, the angled facets need not be planar but can be non-planar and may, for example, be curved. Examples of optical elements <NUM> comprising Fresnel lens elements having curved facets 21A are shown in <FIG>. In <FIG>, the facets 21A are convex and curve or bow outward away from the layer of material <NUM> or from the bottom surface <NUM>. In <FIG>, the facets 21A are concave and curve or bow inward toward the layer of material <NUM> or toward the bottom surface <NUM>. The angled facets 21A, can however have other curvatures. Similarly, the steepness and/or shape of the angled facets 21A can be different.

As described above, the optical element <NUM> may comprise a plurality of Fresnel surface elements <NUM> formed in a layer of material or film <NUM>. In some embodiments, the plurality of Fresnel surface elements <NUM> may be formed in the surface <NUM> of the layer of material <NUM> that is disposed on a substrate <NUM> or on a layer formed on a substrate as illustrated in <FIG> and <FIG>.

<FIG>, for example, shows a Fresnel lens elements (or grooves) <NUM> disposed on the surface <NUM> of the layer of material <NUM> so as to be exposed. The layer of material or film <NUM> has opposite first and second (top and bottom) sides and surfaces <NUM>, <NUM>. In the implementation shown in <FIG>, the angled facet portion 21A and the horizontal portion 21B are on the first (top) side and surface <NUM> and the substrate <NUM> is on the second (bottom) side and surface <NUM>. In some implementations, the layer of material <NUM> may comprise an optically transmissive or transparent layer of material and the optical element <NUM> may be an optically transmissive optical element <NUM>. Likewise, in some implementations, the substrate <NUM> is transparent or optically transmissive. Adhesive may adhere the layer of material <NUM> to the substrate <NUM>. This adhesive may comprise heat activated adhesive in some implementations. An adhesive or a cured adhesive may therefore be disposed between the layer of material <NUM> and the substrate <NUM>. According to the invention, the plurality of Fresnel lens elements <NUM> are formed by hot stamping. Other processes may also be employed but not falling within the scope of the invention.

As discussed above, the layer of material or film <NUM> may comprise an optically transmissive or transparent material. In some embodiments, the layer of material <NUM> may comprise a polymer material. For example, in some embodiments the layer of material <NUM> may comprise any one or combination polyester, polycarbonate, polypropylene, polyethylene terephthalate, and acrylic. Other material may also be used.

Also as discussed above, the substrate <NUM> may comprise an optically transmissive or transparent material. In some embodiments, the substrate <NUM> may comprise a polymer material. For example, in some implementations the substrate <NUM> may comprise any one or combination polyester, polycarbonate, polypropylene, polyethylene terephthalate, and acrylic. Other material may also be used.

According to the invention, the optical element <NUM> comprises reflective material. For example, a reflective coating <NUM> such as metallization may be formed on or added to the microstructure as illustrated in <FIG>. The horizontal portions 21B are coated with reflective material <NUM> such as metal to make the optical element (e.g., Fresnel lens) reflective. Materials besides metalization such as dielectrics, including for example, zinc oxide, may be used for the reflective coating <NUM>. In some cases, the facets 21A may also be coated with reflective material <NUM>.

Accordingly, in some cases, the optical element <NUM> (e.g., Fresnel lens) may be a multilayer structure including, for example, the substrate <NUM> and/or one or more layers in which the facets 21A are formed and/or a reflective coating <NUM> such as metallization.

Although the substrate <NUM> may comprise optically transmissive material such as optically transparent material, the substrate need not be optically transmissive or optically transparent. The substrate <NUM> may comprise opaque material. The substrate <NUM> may, for example, comprise a paper product. The substrate <NUM> may, for example, comprise paper board or other material. In some cases, the substrate <NUM> comprises packaging or a product on which the optical element <NUM> is superimposed.

In some cases additional layers may be added to either or both sides of the optical element <NUM>. In some implementations, for example, an additional layer or layers may be added to the optical element <NUM> once the facets <NUM> and/or reflective coating <NUM> have been formed. For example, an ink may be printed on top of an optical element <NUM> comprising a multilayer structure. However, in some other embodiments one or more layers may be provided below the one or more layers in which the facets <NUM> are formed.

In contrast to <FIG> and <FIG> where the Fresnel lens elements <NUM> and the substrate <NUM> are disposed on opposite sides of the layer of material <NUM>, in <FIG> and <FIG> the Fresnel lens elements are disposed between the substrate and the layer of material. The layer of material or film <NUM> has opposite first and second (top and bottom) sides (and surfaces <NUM>, <NUM>). In the implementation shown in <FIG> and <FIG>, the angled facet portion 21A and the horizontal portion 21B as well as the substrate <NUM> are on the same side, here the first (top) side as opposed to the second (bottom) side.

In <FIG>, the substrate <NUM> is over the layer of material <NUM> and covers the layer of material. Similarly, the substrate <NUM> is over the Fresnel lens elements (or grooves) <NUM> and covers the Fresnel lens elements. In some implementations, adhesive adheres the substrate <NUM> to the layer of material <NUM>. This adhesive may fill in the indentations in the layer of material <NUM> that form the angled facets as illustrated in <FIG>. The Fresnel lens elements <NUM> are thereby created by the surface or interface between the layer of material <NUM> with the angled facet portion 21A and the substantially horizontal portions 21B and the adhesive and/or substrate <NUM>. As used herein, a surface need not be exposed to air but may comprise, for example, an interface between two materials or two different regions such as two regions having, e.g., different index of refraction and/or material composition. In some cases, a difference in refractive index on opposite sides of this interface or surface causes refraction of light and may provide deflection of light and/or optical power.

Accordingly, in some implementations, the layer of material <NUM> may comprise a transparent layer of material and the optical element <NUM> may be a transmissive optical element. Likewise, in some implementations, the substrate <NUM> is transparent or optically transmissive. As discussed above, adhesive may adhere the layer of material <NUM> to the substrate <NUM>. This adhesive may comprise UV activated adhesive in some implementations. An adhesive or a cured adhesive may therefore be disposed between the layer of material <NUM> and the substrate <NUM>. Also, in some cases, the plurality of Fresnel lens elements <NUM> may be formed by cold transfer. Other processes may also be employed.

As discussed above, the layer of material or film <NUM> may comprise an optically transmissive or transparent material. In some embodiments, the layer of material <NUM> may comprise a polymer material. For example, in some embodiments the layer of material <NUM> may comprise any one or combination of polyester, polycarbonate, polypropylene, polyethylene terephthalate, and acrylic. Other material may also be used.

Also as discussed above, the substrate <NUM> may comprise an optically transmissive or transparent material. In some embodiments, the substrate <NUM> may comprise a polymer material. For example, in some implementations the substrate <NUM> may comprise any one or combination of polyester, polycarbonate, polypropylene, polyethylene terephthalate, and acrylic. Other material may also be used.

The optical element comprises reflective material. For example, a reflective coating <NUM> such as metallization may be formed on or added to the microstructure as illustrated in <FIG>. The facets 21A and the horizontal portions 21B may, for example, be coated with reflective material <NUM> such as metal to make the optical element reflective. Materials besides metalization such as dielectrics, including for example, zinc oxide, may be used for the reflective coating.

Accordingly, in some cases, the optical element or Fresnel lens <NUM> may be a multilayer structure, for example, including the substrate <NUM> and/or one or more layers in which the facets are formed and/or a reflective coating such as metallization.

Although the substrate <NUM> may comprise optically transmissive material such as optically transparent material, the substrate <NUM> need not be optically transmissive or optically transparent. The substrate <NUM> may comprise opaque material. The substrate <NUM> may for example comprise a paper product. The substrate <NUM> may, for example, comprise paper board or other material. In some cases, the substrate <NUM> comprises packaging or a product on which the optical element <NUM> is superimposed.

As discussed above, the optical element <NUM> may comprise a plurality of annular Fresnel lens elements <NUM> as illustrated in <FIG>. Accordingly, the facets 21A that are part of the Fresnel lens elements <NUM> may be annular. Similarly, the substantially horizontal portions 21B that are part of the Fresnel lens elements <NUM> may be annular. The optical element <NUM> may, in some implementations, have optical power. As discussed above, the optical element may <NUM> comprise a Fresnel lens.

<FIG> schematically illustrates an example cross-section of a portion of the optical element <NUM>. As shown, a primary angle, α, of the angled facet portion 21A of the Fresnel lens elements <NUM> on average increases from a portion of the optical element <NUM> to another portion of the optical element. For example, the angle, α, of the angled facet portion 21A of the Fresnel lens elements <NUM> may on average increase from a central portion <NUM> of the optical element <NUM> to a peripheral portion <NUM> of the optical element. In some implementations, for example, the spacing <NUM> of the plurality of Fresnel elements <NUM> on average decreases from a portion of the optical element <NUM> to another portion of the optical element. In some such cases, the facet height or depth <NUM> may be constant, and the angle, α, may still increase because the spacing <NUM> reduces. The average increase in angle, α, or decrease in spacing <NUM> may occur over <NUM> to <NUM> consecutive Fresnel lens elements <NUM>, <NUM> to <NUM> consecutive Fresnel lens elements, <NUM> to <NUM> consecutive Fresnel surface elements or any range between any of these values, or outside these ranges. In some implementations, the spacing <NUM> of the plurality of the Fresnel elements <NUM> on average decreases from a central portion <NUM> of the optical element <NUM> to a peripheral portion <NUM> of the optical element.

Likewise, the angle, α, of the angled facet portion 21A of the Fresnel surface elements <NUM> can on average decrease from a portion of the optical element <NUM> to another portion of the optical element. The spacing <NUM> of the plurality of Fresnel elements <NUM> can on average increase from a portion of the optical element to another portion of the optical element (while the facet depth remains substantially constant). The average decrease in angle or increase in spacing <NUM> may occurs over <NUM> to <NUM> consecutive Fresnel lens elements <NUM>, <NUM> to <NUM> consecutive Fresnel lens elements, <NUM> to <NUM> consecutive Fresnel lens elements or any range between any of these values, or outside these ranges.

In various implementations, the angle, α, of the angled facet portion 21A of Fresnel lens elements <NUM> can vary with respect to the center of curvature of the Fresnel lens element.

Although optical elements <NUM> can have a monotonically varying characteristic, such as facet angle, α, such characteristics need not vary monotonically. For the facet angle, α, can increase and then decrease or decrease and then increase or both or increase and decrease (or decrease and increase) multiple times with distance from a location on the optical element. Such an optical element <NUM> may be described as having an undulating pattern. The facet angle, α, may increase and/or decrease with distance from the left or with distance from the right or with distance from the top or with distance from the bottom, for example. The facet angle, α, may be zero or close to zero on some portions of the optical element <NUM> creating for example one or more flat regions. The flat region may be at the center of the optical element <NUM> in some cases, however, the flat region need not be limited to the center of the optical element <NUM>. Multiple flat regions may also exist wherein the facet angle, α, is zero or substantially zero.

Also, although the Fresnel lens elements <NUM> are shown as annular in Figure <NUM>, the Fresnel lens elements need not be annular. Similarly, although the Fresnel lens elements <NUM> are shown as circular in Figure <NUM>, the Fresnel lens elements need not be circular. A variety of shapes, configurations, and arrangements are possible. <FIG> shows an example of a cylindrical Fresnel lens comprising a plurality of elements <NUM>. Such cylindrical Fresnel lens elements <NUM> may provide different optical power in one direction than another of the optical element <NUM>. The cylindrical Fresnel lens elements <NUM> may, for example, provide a first optical power in a first direction and a second optical power in a second direction, wherein the first optical power is greater than the second optical power. These directions may, in some cases, be orthogonal directions, such as for example directions parallel to the horizontal and vertical or parallel to x and y axes. Other arrangements are possible though. As discussed herein, the optical element <NUM> may include Fresnel lens elements <NUM> comprising facets 21A and horizontal portions 21B.

As shown in <FIG> and in some embodiments an optical element <NUM> may comprise, for example, one or more Fresnel lens elements <NUM> comprising a spiral cut. In some implementations, the distance of the angled facet portion 21A (and horizontal portions 21B) from the center or central portion increases with rotation about the center or central portion. Spiral cuts can be employed for other shapes, such as for example, cylindrical lenses.

The optical element <NUM> may produce different optical effects depending on the type of optical element. An optical element comprising a plurality of Fresnel lens elements comprising concentric rings, for example, may produce an image of a ball when viewed, for example, when the optical element is reflective (such as is metalized so as to be reflective). The reflections are distorted in a manner that resembles the reflections from a metal ball or orb. An optical element comprising a cylindrical Fresnel lens, may produce an elongate image having a bar-shape, rod-shape, or pillar shape when viewed, for example, when the optical element is reflective. The reflections are distorted in a manner that resembles the reflections from a metal bar, rod or pillar.

As discussed above, in some implementations, the optical element may comprise a plurality of annular Fresnel surface elements <NUM>, where the Fresnel surface elements <NUM> vary in optical power from positive to negative (and possibly back to positive) from a more central location to a more peripheral location of the Fresnel lens (e.g., with respect to the center of the Fresnel lens). Alternatively, the facet angles of the Fresnel surface elements <NUM> could vary from negative to positive (and possibly back to negative) optical power from a more central location to a more peripheral location of the Fresnel lens (e.g., with respect to the center of the Fresnel lens). Such an optical element may be referred to as undulating. In some designs, the angle of the angled facet portion may vary so as to provide the variations from positive and negative optical power and/or vice versa. Such an optical element comprising an undulating pattern may comprise an annular or ring-like pattern such as possibly a plurality of concentric rings. The undulating pattern, in some cases, may produce an image of a toroid or doughnut shaped structure, for example, when the optical element is reflective (such as is metalized so as to be reflective). An optical element comprising a plurality of undulating Fresnel surface elements <NUM> such as an annular or ring-like pattern comprising a plurality of concentric rings that oscillates between positive and negative optical power a number of times, e.g., more than more than three times, may possibly produce an image of a plurality of concentric toriods. The result may in some cases be an image that appears to be an undulating or wavelike surface that may, for example, look like the waves produced when a rock is dropped into a still pond.

In some cases, the ultra thin Fresnel lens may not disperse incident light even though a facet depth <NUM> of the ultra thin Fresnel lens may be smaller than a facet depth <NUM> at which an typical known Fresnel lens <NUM> would disperse incident light. Likewise, with certain designs, an optical element <NUM> having one or more or characteristics or features as described herein may have a desired achromatic or substantially achromatic or metallic appearance with a facet depth <NUM> less than about <NUM> microns as described above. According to the invention, the facet depth or height <NUM> is less than <NUM> microns, <NUM> microns, <NUM> microns, <NUM> microns, <NUM> microns, <NUM> micron or less or may be greater than <NUM> microns, <NUM> micron, <NUM> micron, <NUM> micron, <NUM> micron, or may be any value in any range defined by any of these values. Being achromatic or substantially achromatic appearance, the optical element <NUM> may reflect or transmit incident light (depending on whether the optical element is a reflective or transmissive optical element) without a substantial amount of color dispersion or iridescence.

A transmissive optical element may for example transmit more light than it reflects while a reflective optical element may reflect more light than it transmits. In some implementations, the optical element <NUM> is a transmissive optical element (transmitting more light than it reflects) while other of the optical element is s reflective optical elements (reflecting more light than it transmits).

Accordingly, in various implementations, an optical element <NUM> may comprise a plurality of Fresnel lens elements <NUM> comprising an angled facet portion 21A and a shallower portion (e.g., a substantially horizontal portion) 21B, where the minimum spacing <NUM> of the Fresnel lens elements <NUM> corresponds to the spacing or frequency of the grooves in a conventional thicker Fresnel elements <NUM> that does not cause dispersion, but the facet depth or height <NUM> of the ultrathin Fresnel surface elements is less than the facet depth or height of the conventional thicker Fresnel elements. In this way, various implementations of the optical element <NUM>, for example, an ultrathin Fresnel lens <NUM> having one or more characteristics as described above, may be formed having a minimum spacing <NUM> or frequency that is substantially similar to the frequency of a conventional Fresnel lens that does not cause prominent dispersion, while the formed optical element <NUM> has a facet depth or height <NUM> that is smaller than the facet depth or height of the conventional Fresnel lens.

<FIG> shows the facet depth or height <NUM> of a tool used to fabricate the ultra thin optical element (e.g., Fresnel lens) as well as the facet angle, α, plotted as a function of radial distance.

As can be seen in <FIG>, the facet depth <NUM> of the ultra thin Fresnel lens is less than about <NUM> microns. The facet angle, α, also changes with radial position on the optical element (e.g. Fresnel lens) <NUM>. Note that above a certain radius, e.g., <NUM>, the facet depth <NUM> is substantially constant. The facet spacing <NUM> may be changing (e.g., reducing) to provide the facet angle, α, that increases above <NUM> and toward the periphery <NUM>.

<FIG> is an image of a thick Fresnel lens that has a minimum facet spacing of <NUM> microns or larger. Having a minimum facet spacing of <NUM> microns or larger reduces dispersion and produces a more achromatic or "metallic" in appearance. Depending on the application, in some cases, however, being thick can be less preferred. As discussed above, the photographer who took the photograph of the Fresnel lens of <FIG> as well as the photographer who took the photograph of the Fresnel lenses of <FIG> and <FIG> is visible at the center of the respective lenses. The reflections of the photographer in the respective lenses shows the photographer's right hand (on left side) as well as the camera held in the photographer's left hand (on right side). A mirror image of the photographer is visible, therefore the photophapher's right hand is on the left side and the photographer's left hand is on the right side of the image.

<FIG> shows an example of a thinner optical element (e.g., Fresnel lens) than the optical element shown in <FIG>. The optical element shown in <FIG> has been made thinner by scaling down both facet height <NUM> and spacing <NUM>. The Fresnel lens <NUM> has a facet depth <NUM> less than about <NUM> microns and a corresponding facet spacing of less than about <NUM> microns. As a result of the reduced facet spacing <NUM>, however, there is significant color dispersion of incident white light resulting in rainbow colored sections and different sections with different highly saturated colors. Moreover, the color dispersion results in chromatic aberration that causes the image of the photographer at the center of the Fresnel lens to be blurred in comparison, for example, to the image of the photographer at the center of the thick Fresnel lens shown in <FIG>, which has less dispersion because the minimun spacing is larger. The blur, for example, of the hands of the photographer (especially the right hand on the left side) as well as of the camera are clearly visible in <FIG>.

The resultant optical properties of an optical element (e.g. Fresnel lens) <NUM> designed as described herein can be observed in the example reflective optical element shown in <FIG>. The Fresnel lens shown in <FIG> has a reduced facet depth, for example, a maximum facet depth of about <NUM> microns such as shown in the plot of Fiugre <NUM>. Despite the very small facet depth <NUM>, which can be included in a reduced thickness optical element (e.g., "ultra thin" optical element), the minimum facet spacing is <NUM> micrometers or larger. As a result of the larger facet spacing, the Fresnel lens is achromatic or "metallic" in appearance and has substantially reduced color dispersion. Moreover, as described above, the reduced dispersion produces less chromatic aberration that would otherwise cause the image of the photographer at the center of the photo to be more blurred. (See, for comparison, the clearer image of the hand of the photographer (e.g., right hand) that is visible in <FIG> as compared to the relatively blurred image of the photographer's hand at the center of the Fresnel lens shown in <FIG>). The image of the photogpher at the center of the "ultra" thin Fresnel lens shown in <FIG> is sharper than the image of the photographer at the center of the Fresnel lens shown in <FIG>, because the minimun facet spacing of the "ultra" thin lens of <FIG> is larger and thus the lens produces less chromatic aberration.

Although Fresnel lens <NUM> having circular and/or annular Fresnel lens elements <NUM> are possible, for example, as shown in in <FIG>, the Fresnel lens elements may be different and have different shapes. For example, the Fresnel lens elements <NUM> need not be circular or annular. The Fresnel lens elements <NUM> may, for example, be cylindrical and have linear Fresnel lens element portions, such as shown in <FIG>. Other variations are possible, for example, an optical element can have Fresnel surface elements that have an undulating pattern. Similarly, as described above, the Fresnel lens elements may comprise a spiral cut. As shown, this spiral shape includes a center and a plurality of annular or ring shaped elements that are concentric. <FIG> schematically show top views of optical elements <NUM> comprising a plurality of Fresnel lens elements <NUM>. The shape and number of the Fresnel lens elements <NUM> may vary from that shown. Likewise, the shape and size of the optical element <NUM> can vary from that shown.

Similarly, a plurality of optical elements <NUM> may be included together, for example, in a sheet. The boundaries between the optical elements <NUM> may be regular (such as a square or rectangular array) or irregular (e.g., random or pseudorandom or otherwise irregular). The optical elements <NUM> may be arrange to produce a letter, character, symbol, image, etc. or may be selectively disposed on portions of a surface so as to coincide with letter, character, symbol or image. The optical elements <NUM> may, for example, be disposed on a portion of packaging where lettering or an image is disposed. In this manner, the optical effect produced by the optical elements <NUM> may highlight the letters or image (or other character or symbols). As discussed above, in some embodiments the optical element <NUM> may produce the image of a ball or orb, wherein the focal length of the Fresnel lens comprising the optical element <NUM> is correlated to the diameter of the ball or orb.

As illustrated in <FIG>, certain optical element <NUM> may comprise Fresnel lens elements <NUM> comprising angled facet portions 21A and substantially horizontal portions 21B wherein the width of the substantially horizontal portion is greater than the width of the angled facet portions. Such a configuration may attenuate the optical effect caused by the angled facet portions 21A, which may be desirable in some applications. Likewise in certain implementations, the width of the substantially horizontal portion 21B comprises <NUM>% or more of the width <NUM> of the Fresnel lens element <NUM> and the width of the faceted portion 21A may comprise <NUM>% or less of the width of the Fresnel lens element. Similarly, in some implementations, the width of the substantially horizontal portion 21B comprises <NUM>% or more of the width <NUM> of the Fresnel lens element <NUM> and the width of the faceted portion 21A may comprise <NUM>% or less of the width of the Fresnel lens element <NUM>. In some implementations, the width of the substantially horizontal portion 21B comprise <NUM>% or more of the width <NUM> of the Fresnel lens element <NUM> and the width of the faceted portion 21A may comprise <NUM>% or less of the width of the Fresnel optical element. In some implementations, the width of the substantially horizontal portion 21B comprise <NUM>% or more of the width <NUM> of the Fresnel lens element <NUM> and the width of the faceted portion 21A may comprise <NUM>% or less of the width of the Fresnel lens element. Accordingly, the width of the substantially horizontal portion 21B may comprise <NUM>%, <NUM>%, <NUM>%, <NUM>% or more of the width or spacing <NUM> between Fresnel lens elements <NUM> and may be less than <NUM>%, <NUM>%, <NUM>%, <NUM>% for one or more of the Fresnel lens elements in the optical element <NUM>. Any value in any range formed by any of these values are possible, although values outside these ranges are also possible. Similarly, the width of the angled facet portion 21A may comprise <NUM>%, <NUM>%, <NUM>%, <NUM>% or less of the width or spacing <NUM> between Fresnel lens elements <NUM> and may be more than <NUM>%, <NUM>%, <NUM>%, <NUM>% for one or more of the Fresnel lens elements in the optical element <NUM>. Any value in any range formed by any of these values are possible, although values outside these ranges are also possible.

In such implementations, the facet depth <NUM> may or may not be less than <NUM> microns. In some implementations, the facet depth or height <NUM> is larger than <NUM> microns, <NUM> microns, <NUM> microns, but not larger than about <NUM> microns. Although the facet depth may be any value in any range defined by any of these values, other facet depths outside these ranges are also possible but not falling within the scope of the invention.

In some implementations, the facet depth or height <NUM> is less than <NUM> microns, <NUM> microns, <NUM> microns. In some embodiments, the facet or height <NUM> is greater than <NUM> microns, <NUM> microns, or <NUM> microns. Although the facet depth may be any value in any range defined by any of these values, other facet depths outside these ranges are also possible.

As discussed above, features in the drawings provided herein may not be to scale.

Claim 1:
A hot stamped film, said film having first and second surfaces (<NUM>,<NUM>) separated from each other in a vertical direction, said film comprising an optical element (<NUM>), said optical element (<NUM>) comprising:
a plurality of Fresnel lens elements (<NUM>) spaced in a horizontal direction with respect to each other, individual ones of said plurality of Fresnel lens elements (<NUM>) comprising an angled facet portion (21A) and a substantially horizontal portion (21B), said plurality of Fresnel lens elements (<NUM>) closer in said vertical direction to said first surface (<NUM>) than said second surface (<NUM>),
wherein said angled facet portion (21A) has a depth that is on average less than about <NUM> microns, and
wherein a minimum spacing (<NUM>) of the plurality of Fresnel lens elements (<NUM>) is greater than or equal to <NUM> microns,
characterized in that the substantially horizontal portion (21B) is coated with reflective material (<NUM>).