How 34,000 tiny holes might thwart a counterfeiter
07 July 2015
Scientists working in Singapore have found a method that might potentially prevent counterfeit in currency, documents, credit cards and ID cards.
Many modern documents include holograms to enhance their security, and they are generally difficult to replicate outside of an optical lab. Although accurate recreation of these holograms is extremely challenging, a similar shiny, multi-coloured look can be created using a mixture of pigments and base, and this may pass a quick inspection.
The new technology, developed by a team at the National University of Singapore, aims at higher-level security measures rather than street-level counterfeiting. The team has designed an 'ultra-capacity nano-photon sieve' - a device with the capacity to incorporate more than 34,000 'nanoholes' (~300nm in diameter) randomly distributed in its surface. The feature enables the display of a high-pixel and high-quality holographic image at a controlled position.
“Highly secured virtual information is stored in the collection of these nanoholes and they can only be retrieved and read at a particular distance when a proper polarized illumination is employed,” says Qiu Chang-Wei, an assistant professor at the National University of Singapore.
“Our device can be customised for various applications as the dimensionality - for example, two-dimensional or three-dimensional - display distance, polarization, and wavelength dependence can be tailored according to needs.”
“We are looking into making our system more robust, developing multiple holographic images at multiple displaying planes, wavelength-dependent, or polarization-dependent three-dimensional images, higher pixels, and other emerging applications enabled by the capability of handling such a huge quantity of nanoholes,” says Qiu.
An article describing this work is published in the journal, Nature Communications.