Attention Forgers: Optical Security Strengthens with Holographic Color Prints

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Forgers beware, researchers from Singapore University of Technology and Design (SUTD) have developed a new anti-counterfeiting device. Called “holographic color prints,” it can dissuade the forging of important documents, including passports, banknotes, and ids, among others.

According to a Credence Research report, the global anti-counterfeiting industry may reach more than $357 billion by 2026. Current deterrents take the form of anti-counterfeiting holograms, and are found on numerous products, from medicine bottles to bank card. But there’s a growing issue, since these holograms “only modulate the phase of light and can be easily copied,” according to SUTD.

SUTD’s new optical device looks like a typical color print when under ambient white light, however, under laser illumination (red, green, or blue) it projects up to three different images. The devices modulates both the phase and amplitude of light.

“This feat was achieved by fabricating a new type of nanostructured pixel strategically arranged on a plane. Each pixel acts as a speed bump (phase control) and road blocks (amplitude control) for light. The dual-function of holographic color printing increases security and deters counterfeiting,” according to SUTD.

According to the team, the color pixels were developed by “overlaying structural colored filters onto phase plates. Nanostructured posts of different heights are employed as structural colored filters to modulate the amplitude of light.” The researchers then created computer algorithms that had an input of multiple images, and determined the position of phase and colored filter elements as an output file. Lastly, a nanoscale 3D printer sculpted the final print.

Using Luigi Russolo’s 1920 painting Perfume as a test, ambient white lighting revealed nothing out of the ordinary. However, “Different thicknesses of polymerized cuboid are used to modulate the phase plates and form three multiplexed holograms, projected as a red thumbprint, a green key, and blue lettering that reads ‘SECURITY.’ All of these images were embedded within a single print,” according to SUTD (Figure 1).

Figure 1: Enhanced optical security provided by a six-color holographic color print. (Image Source: SUTD)

“The relationship of holograms in combating counterfeiting is analogous to antibiotics against infections. Every so often, new technology is needed to deter counterfeiters as the old fashioned holograms become easier to copy,” explains SUTD Associate Professor Joel Yang.

“For the first time, multiple holograms that are color selective are ‘woven’ into a colorful image using advanced nanofabrication techniques. We are hopeful that these new holographic color prints are user friendly but counterfeiter unfriendly: They are readily verified but challenging to copy, and can provide enhanced security in anti-counterfeiting applications,” says Yang.

To learn more, read the article, “Holographic colour prints for enhanced optical security by combined phase and amplitude control,” published in Nature Communications.