Small Mirrors with Big Impact

G+D Currency Technology uses innovative micro-mirror technology not solely to enhance banknote security, but to simultaneously unlock new possibilities in design too. In this interview, Dr. Stefan Bichlmeier – Head of Product Management at Louisenthal – talks about it in detail and discusses plans for the future.

Dr. Bichlmeier, what distinguishes a banknote with micro-mirror technology at first glance?

It’s the unique optical effects created on security threads and foils. Micro-mirror technology uses a very high number of extremely small mirrors which are aligned and shaped in such a way that the collective impact of their reflections results in an image which seems to dynamically move when the banknote is tipped through different angles. It even enables 3D effects such as the sense of reliefs or the shifting and floating of objects.

It’s also possible to create 3D effects using a hologram. How is micro-mirror technology different?

Unlike holograms, the effects of micro-mirror technology are very clearly identifiable even in poor lighting, and achieve an outstanding degree of contrast and contour sharpness due to highly efficient light reflection. Holograms, on the other hand, are  based on light diffraction, which results in a far more diffuse and darker-seeming image.

The combination of micro-mirrors with a coating provides excellent security against counterfeiting.

Dr. Stefan Bichlmeier, Head of Product Management at Louisenthal

Normal household mirrors can darken over time – is this also a risk for micro-mirrors if banknotes stay in circulation for a long time?

No – no impairment of the effects is expected within the lifecycle of a banknote. The mirrors don’t get cloudy, specifically because they’re not made from coated glass like household mirrors, but rather are shaped and encapsulated in a layered structure.

Tightly packed: Four million mirrors per square centimeter

Dr. Stefan Bichlmeier

How does the shaping process work?

The first step is origination: creating an original based on the design template. This involves a special piece of software calculating the size, viewing angle, and arrangement of the individual mirrors – of which there are around four million per square centimeter. Then, over several electro-forming stages, a tool is created which is used for production.

It sounds as though counterfeiters would have a difficult job imitating the effects of micro-mirror technology...

That’s certainly true. And we further reinforce barriers against counterfeiters by using special coatings such as our RollingStar® security threads, which combine micro-mirror technology with multiple, metallic  thin film layers. This technology creates a unique color shift when the banknote is tilted. Controlling the thickness of each thin film layer at nano-scale is essential to obtain a precise color shift effect. The special coating of our varifeye ColourChange foil, in combination with a window in the banknote, causes a motif to be displayed in turn as brillant blue in transmitted light, and premium gold in direct light. In each case, micro-mirrors and the coating come together to ensure very high anti-counterfeiting security, as has also been proven by independent studies.

Ensure maximum authentication

Can micro-mirror technology also be combined with additional security features?

Yes – there are plenty of options, for example UV fluorescence, or a magnetic signature that ranges from simple yes/no recognition to complex coding. Also clear text technology is applied, in which layers are partly removed, so that additional information such as text is clearly displayed when the note is held up to the light.

Do banknote processing systems need to be adapted for micro-mirror technology?

During the usual adaptation process before a new banknote is issued, for example magnetic properties of a security thread are adapted to banknote processing systems. There is no need for an additional adaptation due to micro-mirrors.

Advances in data processing mean that there will soon be even more effects in terms of both threads and foils.

Dr. Stefan Bichlmeier, Head of Product Management at Louisenthal

New coatings and combinations for greater anti-counterfeiting security

Are there banknotes with micro-mirrors already in circulation?

Our RollingStar® security threads have now been in circulation for several years, in more than 20 denominations. Over 40 additional denominations – including plenty new Galaxy security threads, with expanded, refined origination that combines 3D and dynamic effects in an very innovative way – are in the pipeline. In addition, the first notes featuring security foils are already in circulation. The Armenian 500-dram commemorative note from G+D Currency Technology even won the award “Best Regional Banknote”. This note features a Galaxy thread and – for the first time – a RollingStar® LEAD security foil. It is an excellent example of the benefits RollingStar® technologies – micro-mirrors and colour shift – offer also for foil elements. Further issues of entire series with micro-mirror foils are on the agenda and currently in production – the level of demand is staggering. In order to be able to continue serving them efficiently and reliably, we have increased our capacity considerably already some time ago.

500 dram commemorative note – front
Etchmiadzin Cathedral can be seen on the front. It was built in the 4th century and tradition states that it houses a fragment of Noah’s Ark.

500 dram commemorative note – reverse
Noah and his family, as well as various animals that took their place on Noah’s Ark, are depicted on the reverse.

What does the future of micro-mirror technology look like?

We are constantly advancing this technology, and so are conducting research in a huge range of areas: Progress in data processing means that new effects are constantly being developed in terms of both threads and foils. At the same time, we are working on new add-ons and new combination options, with the objective of further enhancing the anti-counterfeiting security of banknotes and unlocking new possibilities in terms of their design.

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Giesecke+Devrient Currency Technology GmbH

+49 89 4119-0

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