This is the fifth and final paper in a series about optimizing simultaneous offset, a security printing technology that facilitates registration of offset artwork between opposite sides of a substrate. The first four parts examined the simultaneous offset topics summarized in Table 1, including registration, ergonomics, color and contrast. Readers should review these prior papers for background, but the general case throughout is that simultaneous offset can be optimized in many ways that are not exemplified by its usage in contemporary security documents. This fifth paper advocates that simultaneous offset is actually a suite of highly flexible security features, extensible to full-document designs with multiple visual effects, where the strategies described in the first four parts of this series are integrated and optimized together.
|CONCEPTS FROM PART 1: REGISTRATION|
|CONCEPTS FROM PART 2: ERGONOMICS|
|CONCEPTS FROM PART 3: COLOR EFFECTS|
|CONCEPTS FROM PART 4: CONTRAST EFFECTS|
Beginning with a review of some background and following the template in Figure 1, consider the four discrete visual effects introduced in the second part of this series: image completion in Figure 2, image disappearance (or contrast reduction) in Figure 3, contrast increase in Figure 4 and color change (plus image completion) in Figure 5. Consider how partitioning of the artwork between the front and back, and how ink colors are placed, controls the visual effect displayed by each icon in transmitted light. Note that Figures 2 through 4 show only one discrete visual effect each and Figure 5 shows just two, but complex simultaneous offset designs could include multiple iterations of all four (with different and variable artwork) and encompass the entire edge-to-edge offset spread instead of one tiny icon.
Figure 1. Model of the figure structure used for most images in this paper. The left image shows the front of the document in reflected light, the right image shows the back of the document in reflected light, and the center image shows both together in transmitted light (as viewed from the front).
Figure 2. An “image completion” simultaneous offset icon. The complete icon image is partitioned between the front and back, both of which look incomplete because the artwork is not recognizable in reflected light. The complete icon image can only be seen in the transmitted light view in the center. The open regions of unprinted substrate on each side may help document users recognize that this area contains a simultaneous offset icon. Compare to Figures 3 through 5.
Figure 3. An “image disappearance” simultaneous offset icon, compatible with and incorporating a split fountain. The front and back images are negatives of one another in placement of 100% and 0% ink coverage and are surrounded by print of approximately 50% coverage. In transmitted light the density of the icon and the surrounding art become equal, and the image disappears. As in Figure 2, the void areas may help signal document users that the feature is present. Compare to Figures 2, 4 and 5.
Figure 4. A “contrast increase” simultaneous offset icon. The reflected light art is the same on the front and back, and the ink colors are also the same on both sides, so the design simply becomes darker in transmitted light. Unlike Figures 2 and 3, the complete icon art is present on both sides and does not appear half-finished to help draw user attention. Compare to Figures 2, 3, and 5.
Figure 5. A combination “color change” and “image completion” icon. The large design contains the same art on the front and back, but not inside the tiny circle. In reflected light, the large design appears red/green on the front and brown/purple in transmitted light, a color change. The tiny circle is instead an image completion feature and fills in but does not change color. This combination of two visual effects in the same art serves as a template for further innovation. Compare to Figures 2 through 4.
In contemporary security documents simultaneous offset features are almost exclusively small, localized icons featuring a single visual effect of limited complexity. For example, the simultaneous offset feature in the banknote in Figure 6 is among the largest in comparison to most modern security documents, but still occupies only a minor part of the design in the vertical strip at the left and right edges of the note.
Figure 6. A simultaneous offset design that extends from the top to the bottom edges of this banknote. These images show the right edge, but the left edge features the same design. This simultaneous offset design is large compared to most security documents, but it still only occupies a small area of the complete offset artwork. This concept could be extrapolated to extend the icon not only from top to bottom, but also from left to right to encompass more of the offset design. Compare to Figures 7 and 8.
A few reasons for limited contemporary use of simultaneous offset in documents may be that issuers have not considered the flexibility simultaneous offset offers, or maybe they view it as a relatively unimportant “checkbox” feature to be included but not optimized, or maybe some issuers see simultaneous offset icons as just one of many features that compete for limited document space and must therefore be size-constrained. But once a manufacturer possesses the required press hardware capabilities, simultaneous offset becomes a powerful low-cost design platform that does not require additional manufacturing processes, expensive consumables, or supply chain logistics to scale up the size and complexity of simultaneous offset artwork.
Imagine designing multiplate, nonrepeating offset security artwork where the main priority is incorporating multiple front-to-back register effects that span the entire document edge-to-edge, to the point where offset artwork that does not contribute to the simultaneous offset design is minimized, or even excluded completely. In this model, the front and back offset designs are not independent and must work together everywhere; alternately, one could think of the back offset artwork as subordinated to both the front art and the needs of the simultaneous offset visual effects. Conventional offset artwork practices like guilloche, microprinting, fine line patterns, security halftones and others remain important and necessary but are used primarily (or even exclusively) in ways that also support the simultaneous offset design. The entire offset design strategy revolves around simultaneous offset, and offset art that does not contribute to multiple simultaneous offset visual effects, drawing user attention, or improving inspection ergonomics, is at most a minor component of the design.
An example of a full-document simultaneous offset design focused on color and saturation effects is shown in Figures 7A and 7B, though the design is too simple and is only intended for demonstration. Imagine this mockup to be a full-size birth record, where the simultaneous offset feature dominates the offset design, fills the entire page and contains different color change icons throughout. An actual security design could contain combinations of visual effects besides color changes, additional plate images, nonrepeating line artwork that cannot be counterfeited using step-and-repeat processes, integration with other transmitted light and offset features, and many other characteristics.
Figure 7A. Mockups of individual plate images in a four-plate, full-document simultaneous offset design. These images extend edge-to-edge in both directions and are the dominant feature throughout the entire offset artwork. The composite front and back reflected light mockups, and a transmitted light mockup, are shown in Figure 7B. Compare to Figures 6 and 8.
Figure 7B. Composite reflected and transmitted light images based on the individual plates shown in Figure 7A, which create several color and saturation effects in an edge-to-edge, full-document simultaneous offset design. This mockup is simple, and a better approach would incorporate image completion, image disappearance, contrast increase and color change effects all together in a panorama of complex nonrepeating artwork. Compare to Figures 6 and 8.
Similarly, Figure 8 shows an edge-to-edge, full-document mockup emphasizing contrast effects. In reflected light, the stars and stripes pattern repeats, but in transmitted light, parts of the design vanish (image disappearance) while other areas become darker (contrast increase). Just as with Figures 7A and 7B, this design is far too simple for real security work and only shows one a basic concept. A better approach would entail more complex nonrepeating artwork, multiple visual effects and so forth.
Figure 8. A simultaneous offset design featuring both image disappearance and contrast increase icons that cause some parts of the design to vanish and others to darken in transmitted light. As in Figure 7, a better approach for this design would be to incorporate multiple diverse visual effects in nonrepeating art, including placing image disappearance effects over watermarks or other transmitted light features to make them easier to inspect without competition from the offset print. Compare to Figures 6 and 7.
The edge-to-edge, full-document simultaneous offset models shown in Figures 7 and 8 can offer several potential advantages.
First, if the entire offset artwork on both sides is engaged with the simultaneous offset feature, then simultaneous offset visual effects would be easy to locate because users could find a part of the design anywhere and everywhere, instead of in only one specific location.
Second, a design in which 100% of the graphics contribute to a simultaneous offset feature would be clean and easy to interpret in transmitted light because there are no areas where the front and back offset art compete, unlike most contemporary security documents that consist mainly of uncorrelated front and back offset artwork. For examples, review Figures 2 through 5 – but instead of examining the simultaneous offset icon itself, examine the mismatched front and back artwork surrounding the icon. Outside the icon the art becomes blurry, does not contribute to transmitted light inspection and may even confuse document users that have to search around and through it for transmitted light features.
Third, multiple iterations of each of the four visual effects identified in prior papers in this series could be integrated in many locations with different artwork and different plate combinations throughout the design, with each instance treated as a distinct and unique security feature. Revisit Figures 5, 7 and 8 for examples of simultaneous offset designs that contain multiple visual effects.
Fourth, document real estate can be conserved. It is unnecessary to identify a specific area to fit in a simultaneous offset icon, since various simultaneous offset effects can be found everywhere.
Security Feature Integrations
The previous section introduced the concept of designing the entire front and back offset artwork around the priorities of a complex, multi-effect, edge-to-edge, full-document simultaneous offset design. This idea can be extended beyond offset artwork to other transmitted light features such as watermarks, security threads, perforations and others. For example, reflected light offset artwork is often designed to alert document users to the location of a transmitted light security feature and make it easier to inspect. Some examples include gaps in printed artwork that signal the location of a watermark as in Figure 9, or an image completion simultaneous offset feature like the one shown in Figure 2 where the unprinted space makes the design look half-finished and helps draw user attention.
Figure 9. Ergonomic design for a watermark feature that advertises itself before transmitted light inspection. In reflected light, the left image shows an open area of unprinted paper that signals that a security feature is present, making the watermark easier to locate. When viewed in transmitted light in the right image, the absence of overprinting also makes the watermark details easier to inspect.
Expanding further on these reflected light design concepts and simultaneous offset, some issuers already print simultaneous offset features over watermarks so both features draw attention to each other and can be inspected together, as shown in Figure 10.
Figure 10. Intersection of a simultaneous offset icon with a watermark. Since both are transmitted light features, they can be inspected in tandem and help advertise one another.
Another example is an image completion simultaneous offset icon intersected with a perforation, as in Figure 11.
Figure 11. Intersection of a simultaneous offset icon with a perforation. Since both are transmitted light features, they can be inspected in tandem and help advertise one another.
Figures 10 and 11 show image completion in simultaneous offset icons, but other visual effects or combinations of visual effects could also be used. Consider how contrast-reducing (image disappearance) effects like the one in Figure 3 could be intersected with transmitted light features. Simultaneous offset images that vanish in transmitted light allow for easier inspection of a watermark, security thread and/or perforation in the same area without the competing offset art. Also, consider the reverse, where a highlight watermark could be placed in areas containing simultaneous offset to reduce substrate opacity, improve contrast and make the simultaneous offset feature easier to check. For example, the highlight watermark shown in the passport data page in Figure 12 is really intended for tamper resistance, but it also improves visibility of the simultaneous offset icon where they intersect.
Figure 12. Intersection of a simultaneous offset icon with a highlight watermark. In transmitted light, simultaneous offset icons may be easier to inspect in areas of thinner paper where the contrast is improved. Although this specific watermark is primarily an anti-alteration feature for a passport data page, different highlight watermark configurations could be explored for the purpose of showcasing a simultaneous offset feature.
Beyond harmonizing with other transmitted light features, reflected light simultaneous offset artwork should also be optimized to resist both digital and traditional counterfeiting by forcing counterfeiters to deal with problems unrelated to front-to-back register, including resolution, gamut limitations, multi-process same-side registration, halftone simulation limitations, etc. These strategies were presented previously in this series and will not be revisited in detail here.
The above offset strategy proposes a complex, multi-effect simultaneous offset feature be the focus of the entire offset art, such that transmitted light inspection shows a giant edge-to-edge simultaneous offset design where no mismatched front and back art compete, and other transmitted light security features are accentuated rather than obfuscated. The entire document and all of its components, not just a tiny part of the offset artwork, is designed to be accessible and utilitarian when viewed in transmitted light. Intaglio is not typically associated with front-to-back register printing technology or intended for transmitted light inspection, but some compatible thinking can be applied.
First, intaglio art should complement the simultaneous offset feature (and other transmitted light features) and not obscure it to the point of preventing inspection. If the simultaneous offset design does extend edge-to-edge some overlap between the offset and intaglio would be normal, but even that could be avoided if desired. Intaglio over a modest amount of the document surface paired with simultaneous offset that covers the entire document may be an appropriate compromise. Further, although one-sided intaglio is typical for many document types (birth records, visas, etc.), some banknotes have intaglio on both sides. Among issued banknotes with two-sided intaglio the front and back are almost always uncorrelated, so the front and back intaglio designs often overlap in transmitted light and the details of both become obscured. One goal of the simultaneous offset strategies proposed here is that the entire document be designed for easy transmitted light inspection, so one-sided intaglio may be a good choice since there is no back intaglio image to compete. If two-sided intaglio is used, the front and back designs can be arranged not to intersect in transmitted light to prevent visual confusion.
Setting aside considerations specific to its compatibility with simultaneous offset, intaglio artwork can itself be designed with transmitted light inspection in mind. Some methods are varying plate engraving depth to control color saturation, including areas of dry embossing that are easier to see in transmitted light than in reflected light, or emphasizing multi-depth microprinting as described in prior work. (As a side note, microprinting can easily be added to any reflected light offset image, but in transmitted light microprinting on the back may not be legible due to loss of detail.) These intaglio-specific topics deserve their own separate analysis and are noted here only for completeness.
Compromises and Limitations
The strategies described in this paper (and series) present novel security benefits but also raise many questions, including how the importance of two-sided artwork is perceived by issuers. Some document types (i.e., birth records) typically contain little artwork on the reverse, so introducing back-side art to support a simultaneous offset feature inspected from the front may not be controversial. On the other hand, in banknotes the back is often viewed as important real estate to convey national branding imagery that supplements, but is uncorrelated to, the front art. In banknotes, issuers may be reluctant to see the back design become an extension of the front art and simultaneous offset feature because then it cannot also be a vehicle for additional standalone imagery. A similar analysis for passport visa pages, plastic cards and other document types might also be undertaken.
Other considerations include design practices and quality control. Implementing the techniques described in this series requires adapting to new constraints and unconventional approaches to security design, since the entire offset artwork on both sides is treated as a single unit. Similarly, manufacturers must maintain good registration and predictable ink behavior for both same-side and opposite-side multiplate offset work, as quality control consistency is particularly critical for simultaneous offset features. If a simultaneous offset feature is not printed consistently in a genuine document the user population will learn to ignore it and it will contribute no security value, which would be especially problematic in a document where simultaneous offset was used extensively. Designers, manufacturers, and issuers must determine for themselves which, if any, of the concepts presented in this series are appropriate for their own documents, capabilities, and workflows.
In contrast to the limited use, it now sees in contemporary security printing, this paper and series have described how simultaneous offset can be transformed into a core technology for complex edge-to-edge, full document offset security designs. Earlier parts of this series evaluated simultaneous offset features from many different viewpoints, including plate count, resistance to digital/traditional counterfeiting workflows, ergonomic design, placement near other transmitted light features, integration with other offset-compatible features, discrete visual effects and color/contrast effects. But these variables do not exist in isolation. A thoughtfully optimized full-document simultaneous offset panorama could incorporate all of them together in ways that make turn the entire document landscape into a large and complex transmitted light feature, while at the same time presenting technical barriers that make both traditional and digital counterfeiting costly, labor-intensive, and complicated. Again, it is up to each issuer to determine the best way to employ this underutilized technology.
Disclaimer: This document represents the opinions of its authors and not necessarily the opinions of the U.S. government. The technologies and strategies described may not be available, appropriate or manufacturable for all document issuers. The examples shown do not imply anything about the quality of a document, its designer, its manufacturer, or the issuing authority. For informational purposes only.