HK1095949B - System and method for authenticating an article - Google Patents

Description

System and method for authenticating an article

Technical Field

The present invention relates generally to anti-counterfeiting measures and, more particularly, to a method of applying a non-reproducible authentication image to one or more articles.

Background

With the increasing regularity of the current world, personal thieves and black market sales of counterfeit goods are facing considerable problems. Every year, millions of dollars are lost due to fraudulent use of untrusted documents and branded goods. The increased sophistication of optical scanners, copiers, and other devices for reproducing merchandise and identification indicia continues to enhance the ability of counterfeiters to produce fraudulent documents and other counterfeits of sufficient quality to be frequently undetectable.

One approach to providing increased security involves applying some type of indicia, typically an already encoded text string or other image, to the article so that the image cannot be seen by the unaided eye. The encoded image can only be seen by using a decoding device that "reassembles" the image as it was presented prior to encoding.

High definition scanning devices make it possible for even these images to be reproduced. Reproduction devices, such as optical scanners, typically operate by detecting reflections of light projected onto the merchandise by the scanner. Areas of the article with a large amount of pigment will absorb more light than areas with little or no pigment. The scanner may measure the amount or intensity of reflected light recorded by the scanner as computer data. This data is then used by the scanner to produce a copy of the scanned item, typically as a printed copy or digital image. The copy may be of sufficient quality that the encoded printed indicia may also be reproduced. In this case, using a decoder to view the copied item may not reveal its counterfeit nature.

Disclosure of Invention

An illustrative embodiment of the present invention is directed to an authentication article comprising a printable surface, and a latent image formed on a first portion of the printable surface with a transmittent printing medium. The latent image is an encoded version of an authentication image and is configured to be optically decoded by an optical decoder such that the authentication image can be viewed through the optical decoder when the optical decoder is placed over the latent image.

Another illustrative embodiment of the present invention is directed to a method of applying an authentication image to an article. The method comprises the following steps: acquiring a digitized version of the authentication image; encoding a digitized version of the authentication image to produce an encoded latent image; and printing the encoded latent image on a first portion of a printable surface of the article using a transmittent printing medium.

Drawings

FIG. 1 is a perspective view of an authentication article according to an embodiment of the invention;

FIG. 2 is a top view of the authenticatable article shown in FIG. 1;

FIG. 3 is an exemplary authentication image that may be used in embodiments of the present invention;

FIG. 4 is a top view of an authentication article and decoder according to an embodiment of the present invention;

FIG. 5 is a top view of a portion of the decoder shown in FIG. 4;

FIG. 6 is a side view of the decoder portion shown in FIG. 5;

FIG. 7 is a flow diagram of a method of applying an authentication image according to an embodiment of the invention;

fig. 8 is a top view of an authentication article applied to a printed surface.

Detailed Description

Previously used methods of applying coded images to an object for the purpose of authenticating or identifying the object have involved: the encoded image is printed with colored ink or toner. One approach is to segment the original image into fundamentally different blocks. Essentially, the encoded image is not visible to the naked eye unless viewed through a lens having the optical characteristics of "re-assembling" the image.

Encoding methods involving latent image raster scanning and printing are described in U.S. Pat. No.5,708,717 ("the 717 patent"), which is incorporated herein by reference in its entirety. In this method, the latent image is raster scanned with a particular frequency, which may, for example, correspond to a certain number of print lines per inch. The encoded image is then printed onto the merchandise using one or more of the four dominant color printing inks typically used to print visible indicia. If the article to be printed carries a visible image, as well as a latent image, the visible image is also raster scanned at a selected frequency so that the latent image can be adjusted according to the color and density of the various portions of the visible image. The latent image is then printed on the article together with a visible image, wherein the visible image is reproduced in its assembled (i.e., visible) form, while the latent image is in its encoded (i.e., invisible) form. The latent image becomes visible only when a decoding lens configured for the selected frequency of the latent image is placed on the latent image.

In the method of the' 717 patent, the latent image is created using pigmented ink or toner for creating a marking that is visible to advanced scanning equipment. In addition, the method may require digitizing and raster scanning any visible image to be printed on the article to allow adjustment of the latent image. Then, the visible image must be printed simultaneously with the latent image.

Embodiments of the invention described herein provide a method of applying a latent image to an article that is not easily reproducible and allows the latent image to be processed and printed regardless of any visible image to be printed on the article. These methods involve printing an encoded image on an article using a substantially optically transmissive print medium. As used herein, the term "transmittent print medium" refers to a print medium that allows light to pass through the print medium without a significant degree of reflection of incident light in a direction normal to the surface to which the print medium is applied. The optically transmissive print media is not completely transparent and thus produces a slight variation in the reflectivity of the substrate to which the media is applied. When a latent image is printed using a transmittent printing medium according to the present invention, the small changes caused in reflectivity may not be sufficient to cause the disparate image patches to be seen by the human eye. Moreover, the change in reflectivity is small enough that it cannot be distinguished or reproduced by a copier or scanning device. However, it is large enough that when the disparate image blocks are assembled together by the decoder to form a complete image, the image is distinguishable.

The ability to avoid detection by the scanner can be maximized by minimizing the contrast between the areas covered by the optically transmissive medium and the areas not covered by the optically transmissive medium. It has been found that: an optically transmissive medium that provides a contrast of the uncoated areas of the substrate that is less than about 5% (i.e., the substrate's reflectivity is altered by less than 5%) will not be distinguished or reproduced by a typical scanning device or copier. It has also been found that: contrast as low as 0.5% may be sufficient to produce a differentiable image with a decoder. Further improvements to the decoder may reduce the required contrast even further. Highly satisfactory results have been achieved by printing images with a transmittent print medium that produces a contrast with the substrate in the range of about 0.5% to about 1.5%.

The invention will now be described in more detail with reference to the accompanying drawings

Referring to fig. 1 and 2, an article 10 to be authenticated has a printable surface 12, the printable surface 12 being adapted to carry some form of printed indicia. The article 10 may include a primary image 14 printed on a printable surface with pigmented ink, toner, or other printing medium, and a latent image 20 to be used to authenticate the article 10.

Those skilled in the art will understand that: the article 10 may be of any size and shape so that there is a surface portion of the article 10 that can receive printed indicia. For simplicity, the article 10 is shown as a thin planar member, representing an article such as a label, tag, currency or ticket. The article 10, or at least a portion of the article 10 having the printable surface 12, may be any material capable of receiving and holding a print medium, but is not limited to paper, vinyl, cloth, metal, acrylic, polystyrene, polyester, polycarbonate, nylon, and polyethylene.

The printable surface 12 may be printed with a solid or patterned background, a primary image 14, or both a background and a primary image 14. The primary image may comprise any form of graphical image, photographic illustration or text. The background and/or primary image 14 may be printed in ink or toner, either in grayscale or in color, using any known method. In the color printing application, the initial printing may include any four-color printing process. As is known in the art, four color printing involves: separate layers of the four primary print colors (cyan, magenta, yellow, and black) are applied to create a full color image. Suitable printing methods include, for example, photolithography or lithography, intaglio, letterpress, flexography and intaglio. Digital printing finishes, such as inkjet and laser printing, may also be employed.

The article 10 also includes a latent image 20 printed on the printable surface 12 with a substantially transmittent printing medium. The latent image 20 is an encoded version of the selected authentication image 16 to be used to authenticate the article 10. The authentication image 16 may be a single graphical image or, as shown in fig. 3, may be a wallpaper pattern utilizing text or graphics in a repeating geometric or random pattern. The authentication image 16 may feature, for example, a single or repeated display of a message, including a logo or other trademark.

The latent image 20 includes a plurality of image segments that can be assembled together or decoded to allow the authentication image 16 to be viewed. In the exemplary embodiment shown in fig. 1-4, the latent image 20 is a raster scanned version of the authentication image 16 and includes a plurality of parallel lines 22 printed at a predetermined number of lines per inch (frequency). Typical line frequencies will be in the range of about 50 lines per inch to about 300 lines per inch.

The parallel lines 22 are shown in dashed lines in fig. 1 and 2, indicating that they are not normally visible. Those skilled in the art will understand that: the spacing of the lines 22 has been exaggerated for illustrative purposes.

The transmittent printing medium used to print the latent image 20 can be any material suitable for application to a printable surface without producing small changes in the reflectivity of the substrate that do not change over time. Suitable materials may be those classified as clear printer' varnish, and the like. As used herein, the term "printer varnish" refers to a coating, such as a liquid shellac or plastic coating, that may be applied to a printing surface to add durability and a smooth matte or matte finish. The transparent copy varnish is readily available and can be applied to a substrate by standard offset presses without the need for special equipment to be installed. Examples of suitable clear varnishes include Joncryl 1679 and CDX-562. A clear varnish such as this may be used to produce the desired change in reflectivity. The actual contrast with the uncoated areas of the substrate can be determined by the varnish used, the thickness of the applied layer and the use of multiple layers.

It will be appreciated that the particular print medium used may depend on the material and texture of the printable surface, as well as the environment to which the article will be exposed. For example, the article 10 with the latent authentication image 20 may be subjected to additional processing such as heat-induced shrink wrapping. In such an example, a transmittent printing medium suitable for a high temperature environment may be desirable.

The transmittent printing medium may be applied as a cover over the primary image 14. Thus, the latent image 20 may partially or completely cover the primary image 14. Alternatively, the latent image 20 may be printed on a portion of the printable surface that has not been printed with, or has been printed with, a background color or wallpaper design.

In some examples, the latent image 20 may be printed with a transmittent printing medium prior to application of the primary image 14. In such an example, the latent image 20 would be visible through "holes" in the primary image (i.e., areas within the boundaries of the primary image to which no ink or diffusely colored media is applied).

As discussed above, the relative transparency of the transmittent printing medium reduces or eliminates the ability to "see" or reproduce the latent image 20. This feature, in combination with the encoded features of the latent image 20, makes copying of the authentication mark extremely difficult, if not impossible.

The latent image 20 allows the authentication image 16 to be viewed only through the use of the decoder 20, as shown in fig. 4. The decoder is designed to have optical characteristics that match the manner in which the authentication image 16 is encoded. In the illustrated embodiment, the decoder includes a decoding lens 32 fabricated to correspond to the line frequency of the encoded latent image 20. Fig. 5 and 6 illustrate a portion of a decoding lens 32 that may be used in embodiments of the present invention. The decoding lens 32 is a lenticular lens having an upper, viewer-facing surface 34 with a series of curved ridges 36, and a lower, image-facing surface 38 that is substantially flat. The curvature and spacing of the curved ridges 36 are established so as to optically form the raster-scanned segments of the image 20 together. The fixed peak-to-peak distance D between the curved ridges is determined by the desired frequency of the decoding lens 32. The more the frequency of the decoding lens 32 matches the frequency of the latent image 20, the clearer the authentication image 16 will be when the article 10 is authenticated using the decoder 30. If the frequency of the decode lens 32 and latent image 20 are within about 10 lines per inch of each other, the authentication image 16 may still be seen, although the authentication image 16 may appear distorted. If the frequency difference between the decoding lens 32 and the latent image 20 exceeds about 10 lines per inch, the authentication image 16 will not be visible with the decoder 30.

Although the illustrated embodiment of the present invention shows a flat surface and a flat decoder, those skilled in the art will appreciate that: the printable surface may have a known curvature and the decoder may be configured to take into account the curvature to produce a visible authentication image.

Exemplary decoding lens 32 may be an acrylic (acrylic) or polycarbonate lens, although various other thermoplastic resins may also be used. Typically, the decoding lens 32 may be made of or may include a material having a high refractive index for improving readability of an image viewed through the decoder. As is known to those skilled in the art, the speed of light changes as it passes through different media. A particular medium has a refractive index, defined as the speed of light in a vacuum divided by the speed of light passing through the medium. Materials having a refractive index similar to that of air may be preferred in order to reduce distortion of the image seen through these materials.

The thickness of the decoding lens 32 and the radius of curvature of the curved ridge 36 are a function of the optical properties of the material used. For an acrylic lens, a typical lens thickness would be about 90 mils, while the radius of curvature of the ridges 36 would be about 30 mils.

The transmission of light through the decoder 30 to the latent image 20 may be reduced as a result of reflection of incident light by the decoder 30. This phenomenon, known as back reflection, can significantly reduce the ease of distinguishing latent images 20 printed with a transmittent medium. This may necessitate an increase in the contrast of the latent image 20 and, as a result, an increase in the likelihood of reproducibility. In attempting to decode the latent image 20 through a transparent packaging material (i.e., cellophane) such as may be used as the outer packaging material of the article 10, the back reflection effect may be exacerbated if the decoder 30 is used. In many examples, the light that is reflected without being transmitted to the latent image 20 may be between about 4% to about 16% of the total incident light. The higher the refractive index of the material through which the light must pass to reach the latent image 20, the less light is transmitted.

To eliminate back reflection and increase the readability of the latent image 20, either or both of the surfaces 34, 38 of the decoder 30 may be coated with an anti-reflective material. The addition of such materials may increase the light transmission of the decoder 30 to a range of about 90% to about 99% of the incident light.

For example, suitable antireflective materials may include materials such as a single layer magnesium fluoride coating, a narrow band or "V" multilayer coating, or a broad band multilayer coating. In the illustrated embodiment, the decoding lens 32 may have an anti-reflective coating, including four or more layers, resulting in a total thickness of about 2 to 4 microns. The coating may be applied to the entire surface of the lens, or to desired portions of either or both of the lens surfaces 34, 38.

The transmittent latent image 20 provides a number of significant advantages over the prior art. With the previous method, the encoded image must be printed with one of four colored inks of a four color printing process (cyan, magenta, yellow, or black). This necessarily requires that the latent image be printed simultaneously with the corresponding color layer of the primary image. The use of a dominant color also limits the placement of the encoded image to areas that do not contain this high concentration of this color.

In contrast, the latent image 20 of the present invention need not be applied when the primary image 14 and background are printed. This significantly improves the applicability and flexibility of applying and using the authentication token of the present invention. Furthermore, no adjustment of the position of the latent image is required to avoid a particular color density in the primary image 14.

Another advantage is that: the transmittent latent image 20 does not require pre-processing or manipulation of the primary image 14. Previous methods may require digitization and segmentation of the primary image to operate on color separation of the primary ink or blob colors. As is well known in the art, mottle color is a special mixed ink that is pre-made and applied to the printed page, without the use of the main print color used to create the main portion of the image. The areas to be printed with the spot colors are not printed with the main ink color. Therefore, when the encoded image is printed using the dominant color, the encoded image must be placed outside of any area printed with the blob color.

However, in an embodiment of the present invention, the latent image 20 is separately printed using a transmittent printing medium. Therefore, there is no limitation on the position of the latent image 20. The latent image 20 overlies any portion of the primary image 16, including any areas printed with a mottled color.

Another advantage of printing the latent image 20 with clear varnish is that: the image 20 may be printed with a low resolution. The resolution, typically measured in dots per inch, is a measure related to the quality of the printed image. Printers print images using varying sizes and patterns of spots made up of many ink dots. Typically, printers use a halftone grid divided into cells containing halftone dots. The proximity of cells in a grid is measured in rows per inch. When the resolution is lower, there are fewer dots per inch, and halftone speckles are more visible in the printed image. When latent image dots are formed from pigmented ink, the scanner is more likely to reproduce a low resolution image than a high resolution image. This is because in high resolution, the dots have a density that makes the scanner unable to distinguish anything other than a continuous image. Thus, low resolution printing may reduce the effect of latent images printed with pigmented ink. However, when printing latent images with transparent printing media, the difference between high and low resolution is irrelevant, because the scanner cannot distinguish the latent image from the substrate.

Thus, the latent image 20 can be printed using a transparent print medium at a wide variety of resolutions, from low resolution (corresponding to a frequency of about 50 to 65 lines per inch) to high resolution (corresponding to a frequency of 150 lines per inch or more), and any resolution in between. The advantages of using low resolution printing are: which typically involves lower maintenance and lower cost and also provides a higher level of repeatability than higher resolution processes, since lower density materials are used. Repeatability is a term used to describe the ability of a printer to consistently produce identical copies of an image.

The ability to print at low resolution also expands the substrates on which the latent image 20 can be printed. For example, some types of paper, such as newsprint, can only produce low resolution images due to the way the paper absorbs ink and how the ink spreads onto the paper. As a result, newsprint is printed at a resolution of 85 lines per inch. At the other end of the spectrum, high quality coated paper, such as that used for trash, may have a resolution of 150 or more lines per inch because less ink is spread.

The additional advantage of low resolution is: which can be implemented with almost any printing device. While most printers are capable of printing low to medium resolution images, a smaller number of printers are capable of high resolution output.

Some embodiments of the present invention provide for providing additives in the transmittent printing medium to fine tune its density or appearance. These materials may be added to the print medium in small amounts to improve the appearance or readability of the latent image without exceeding a contrast threshold that allows the latent image to be scanned. Such materials may include dyes, reflective materials, or glitter materials. Typically, glitter material reflects light only when viewed at angles other than perpendicular. Because scanners typically transmit light perpendicular to the article being scanned, glitter material may be added to the transmittent print medium without affecting the ability of the latent image 20 to avoid detection and reproduction.

As described above, it will be appreciated that the encoded latent image 20 printed on an article using a transmittent printing medium is combined using the decoder 30 to provide a system for authenticating the article. In this system, the decoder 30 is configured to overlay the encoded latent image 20, decoding the latent image 20 by its optical properties, so that the authentication image 16 can be viewed. In some embodiments, the latent image 20 may be a raster scanned version of the authentication image 16, the latent image 20 being printed at a predetermined line frequency. In such an embodiment, the decoder may include a lenticular lens 32 configured with a corresponding frequency such that the lenticular lens 32 is placed over the latent image 20 and the authentication image 16 is visible. The lens may be configured so that the lens frequency matches the line frequency of the latent image 20 in the range of about plus or minus 10 lines per inch.

FIG. 7 illustrates a flow chart of a method of applying the authentication image 16 to the article 10 according to an embodiment of the invention. The method starts at S100. At S110, the authentication image 16 is selected or created. The authentication image 16 may include text, original work, or an existing logo or trademark. The authentication image 16 may be obtained from a photograph, pictorial or printed text, or any other indicia desired by the user that can provide a sign of authenticity. As previously mentioned, the authentication image 16 may be a single image or a wallpaper-style pattern.

At S120, the authentication image 16 is digitized for storage and/or processing by the data processing system. The pre-existing authentication image 16 may be digitized in any known manner, such as by scanning. It will be appreciated that the authentication image 16 may also be created in digital form, such as by using a digital photographing apparatus or by using a computer.

At S130, the digitized authentication image 16 is encoded using a data processing system and software suitable for the encoding task to produce an encoded image. To accomplish this, the digitized authentication image 16 may be subjected to any of a variety of different encoding or encryption techniques. As described above, one such technique (described in the' 717 patent) involves raster scanning the authentication image 16. In an embodiment of a method suitable for using raster scanning techniques, the encoding software segments the digitized authentication image 16 to create a series of equally spaced lines having a frequency of a particular number of lines per inch specified by the user. Any frequency may be used, although advantageously, the frequencies typically used in printing technology may be selected. Typical printing frequencies may range from about 50 lines per inch to about 150 lines per inch.

The encoded image may be saved as a separate new image file for creating a print pad or screen. In certain printing processes, such as photolithography, this may involve producing full-size film in a positive or negative format using a high-resolution image setter. The film can then be used to create a flexible print plate for attachment to a plate cylinder of a lithographic printing press.

At S140, the encoded image is used to print the encoded latent image 20 on the printable surface 12 of the article 10. The encoded latent image 20 is printed using a transmittent printing medium so that the elements of the latent image 20 cannot be distinguished by direct viewing or by a scanning device. In some embodiments of the present invention, the transmittent printing medium may be a transparent printer varnish, which may be applied using standard printing techniques. The latent image 20 may be printed with a transparent printer varnish in a manner consistent with the printing standards set by the graphic arts technology foundation for a given printing process.

In some examples, the background or primary image 14 has been printed to the printable surface 12 with ink, either in grayscale or in color. Any initial printing on surface 12 may be accomplished by any known method. In the color printing application, the initial printing may include any four-color printing process. Suitable printing methods may include photolithography or lithography, intaglio, letterpress, flexography, intaglio, and the like. Digital printing finishes, such as inkjet and laser printing, may also be employed.

If a portion or all of the printable surface 12 has been pre-printed with a background or primary image 14, the latent image 20 may be printed over the background or primary image 14. In fact, the printing of the latent image 20 may be implemented as a final step of the overall printing process including the initial printing. For example, the latent image 20 may be printed by adding a clear printer varnish layer on the print substrate, as if the fifth color were added to a conventional four color printing process. Alternatively, the latent image 20 may be printed completely independently of the background or primary image 16 using a separate printing device. As a result, the latent image 20 may be added at a completely different facility or by a different manufacturer than the initial printing of the article 10. The latent image 20 may even be applied to a point of sale of the article 10.

In the case where the printable surface has been printed, i.e. comprises one or more primary images, it is particularly effective to apply at least a portion of the latent image in the transmittent printing medium over a primary image that is a "line" or segmented image, i.e. an image having closely but irregularly spaced lines and/or shapes, typically comprising two or more colors that are contrasting. For example, the thread may be a bar code, such as a Universal Product Code (UPC).

When printing a latent image on a transmittent printing medium, the latent image may cause a significant reduction in gloss level at the location where the latent image has been printed. This reduction can alert some sophisticated counterfeiters: products printed with latent images in a transmittent medium have been altered. Although what type of change has occurred or the presence of the latent image may not be apparent, the change may allow the counterfeiter to further investigate the product. Printing a latent image over a line primary image as described above, particularly an image with optional contrast and irregular variation over line spacing such as a bar code, may be particularly helpful in preventing significant differences in gloss levels at locations in the transmittent printing medium where the latent image has been printed. When a person views a thread with the naked eye, the person's vision is typically slightly distorted due to irregularities in the image. In addition, the same optional contrast and varying line spacing of the lines also reduces the ability of the optical scanner to perceive and/or replicate the latent image in the context of scanning the object.

As shown in FIG. 8, the printable surface 12 of the article 10 includes a primary image 14 as a UPC symbol. The UPC symbol is a wire comprising a series of irregularly spaced lines of varying thickness. In the embodiment shown in fig. 8, the latent image 20 is preferably printed in a transmittent printing medium applied over the printable surface 12 such that substantially all of the latent image is printed on the area of the printable surface 12 containing the primary image 14. Thus, the latent image 20 extends only partially, if not completely, beyond the edge of the UPC symbol. For clarity of fig. 8, the areas where the latent image 20 is displayed are shown as boxes, rather than as a series of dashed lines as shown in fig. 1 and 2.

In addition to printing the latent image over the line master image to mask any changes in the gloss level, the changes in the gloss level itself can be directly controlled by using a halftone screen to apply the transmittent printing medium. A halftone screen may be used to gradually change the density of the transmittent printing medium. This change in density causes the gloss level to gradually increase with increasing distance from the latent image. In this way, any reduction in gloss level that may result from printing the latent image is spread over a larger area, reducing the likelihood that a person viewing the article will be alerted to the presence of the latent image. The change in gloss level may be particularly effective when used in combination with printing on thread.

Although the latent image 20 is often printed on an earlier printed product, the latent image 20 may also be printed directly onto an unprinted portion of the printable surface 12. For example, the latent image may be printed directly onto a sheet of paper that has not been previously printed. As mentioned above, a primary image or other printing may be applied after the latent image, at least a portion of the latent image being shown by the unprinted regions of the primary image.

Referring again to fig. 7, once the article 10 has been printed with the latent image 20, the article may be dispensed, further packaged or additionally printed. The method ends at S150.

The invention also provides a method of verifying the authenticity of a suspect article in which authentic articles are printed with an encoded latent image 20 using a transmittent printing medium, whereas non-authentic articles are not. The latent image 20 corresponds to a predetermined authentication image 16 selected by the provider of the authentic article. The method involves acquiring a decoder 30, the decoder 30 configured to be placed at a target location of a suspect article, wherein the encoded latent image 20 would be at the suspect article if the article is authentic. The decoder is further configured to have the following optical characteristics: the latent image 20 can be decoded so that the authentication image 16 (if present) can be seen. The method also involves: the decoder 30 is placed over the target location of the suspect object and the target location is viewed through the decoder. Then, it is determined whether the authentication image 16 is visible. In response to a determination that the authentication image 16 is present, the suspect article is identified as authentic. In response to a determination that the authentication image 16 is not present, the suspect article is identified as being suspect.

In a method of verifying the authenticity of a suspect article in which the latent image 20 is a raster scanned version of the authentication image 16 printed with a predetermined line frequency, the decoder 30 may include a lenticular lens 32 having a lens frequency that matches the line frequency of the latent image 20 within about plus or minus 10 lines per inch.

There are many examples of using the method of the present invention and the method of verifying authenticity according to the present invention may be implemented at any time. For example, customs officials may verify a pass containing an encoded latent image upon entering or leaving the united states, and corporate investigators may verify the authenticity of branded goods contained in their sellers' warehouses.

While exemplary embodiments of the present invention have been illustrated and described, it is to be understood that the invention is not limited to the arrangements disclosed herein. The present invention may be embodied in other specific forms without departing from its spirit or essential characteristics.

Claims (23)

1. An authenticatable article, comprising:

a printable surface;

a latent image formed on a first portion of the printable surface in the transmittent printing medium, the latent image being an encoded version of an authentication image and configured to be optically decoded by an optical decoder such that, when the optical decoder is placed on the latent image, the authentication image can be viewed through the optical decoder,

wherein the transmittent printing medium is selected to provide a maximum reflectance difference between a first portion of the printable surface having the latent image printed thereon and an adjacent region of the printable portion that is no greater than 5% of a reflectance of the adjacent region.

2. The authenticatable article of claim 1, wherein: the transmittent printing medium is selected to provide a maximum reflectance difference between a first portion of the printable surface having the latent image printed thereon and an adjacent region of the printable portion that is within a range of 0.5% to 1.5% of a reflectance of the adjacent region.

3. The authenticatable article of claim 1, wherein: the transmittent printing medium includes a transparent printer varnish.

4. The authenticatable article of claim 1, wherein: the transmittent printing medium includes one or more dyes and a glitter material.

5. The authenticatable article of claim 1, wherein: the latent image includes a plurality of parallel lines printed at a line frequency in a range of 50 lines/inch to 150 lines/inch.

6. The authenticatable article of claim 5, wherein: the line frequency is selected to match the lens frequency of the decoder within plus or minus 10 lines/inch.

7. The authenticatable article of claim 1, wherein: a visible primary image formed on a second portion of the printable surface is also included.

8. The authenticatable article of claim 7, wherein: at least a portion of the latent image is formed over at least a portion of the primary image.

9. The authenticatable article of claim 8, wherein: a maximum reflectance difference between at least a portion of the latent image and at least a portion of the primary image is no greater than 5% of a reflectance of at least a portion of the primary image.

10. The authenticatable article of claim 7, wherein: the primary image includes a thread.

11. The authenticatable article of claim 10, wherein: the thread is a bar code.

12. A system for authenticating the article of claim 1, the system comprising:

an optical decoder comprising a lens adapted to be placed over at least a portion of the latent image, the lens having optical decoding characteristics corresponding to an optically decodable encoding scheme for decoding the latent image when the lens is placed over the latent image, such that the authentication image is viewable through the lens.

13. The system for authenticating objects according to claim 12, wherein: the lens is a lenticular lens formed as a substantially planar piece, the lenticular lens having an upper, viewer-facing surface and a lower, image-facing surface, the viewer-facing surface having a plurality of adjacent parallel curved ridges having a common geometry including a curved uppermost surface having a predetermined curvature, the number and geometry of the parallel curved ridges establishing a lens frequency.

14. The system for authenticating objects according to claim 13, wherein: the lens includes an anti-reflective coating coated on at least one of the upper, viewer facing surface and the lower, image facing surface.

15. The system for authenticating objects according to claim 14, wherein: the anti-reflective coating comprises a magnesium fluoride coating.

16. The system for authenticating objects according to claim 14, wherein: the anti-reflective coating includes at least one of a narrow band coating and a wide band coating.

17. The system for authenticating objects according to claim 14, wherein: the antireflective coating has a total thickness in a range of 2.0 microns to 4.0 microns.

18. A method of applying an authentication image to an article, the method comprising:

acquiring a digitized version of the authentication image;

encoding a digitized version of the authentication image to produce an encoded latent image; and

printing the encoded latent image on a first portion of a printable surface of the article using a transmittent printing medium,

wherein the transmittent printing medium is selected to provide a maximum reflectance difference between a first portion of the printable surface having the latent image printed thereon and an adjacent region of the printable portion that is no greater than 5% of a reflectance of the adjacent region.

19. The method of applying an authentication image to an article according to claim 18, wherein: the transmittent printing medium is selected to provide a maximum reflectance difference between a first portion of the printable surface having the latent image printed thereon and an adjacent region of the printable portion that is within a range of 0.5% to 1.5% of a reflectance of the adjacent region.

20. The method of applying an authentication image to an article according to claim 18, wherein: the transmittent printing medium includes a transparent printer varnish.

21. The method of applying an authentication image to an article according to claim 18, wherein: the article includes a visible primary image disposed on a printable surface, and the act of printing the encoded latent image includes: printing at least a portion of the encoded latent image on at least a portion of the primary image.

22. The method of applying an authentication image to an article according to claim 21, wherein: applying a light transmissive printing medium onto a first portion of a printable surface of an article using a plurality of halftone screens, wherein the light transmissive printing medium is applied at varying densities across the printable surface.

23. The method of applying an authentication image to an article according to claim 22, wherein: the varying density of the applied transmittent printing medium causes the gloss level of the article to gradually increase with increasing distance from the latent image printed on the first portion of the printable surface.