Laser tech creates multilayer holograms on metal

Researchers in Scotland have developed a way to protect metal products from counterfeiting by using laser pulses to generate holographic features directly onto their surfaces.

The team from Heriot-Watt University and Renishaw in Edinburgh describe the work in a paper published in the Journal of Materials Processing Technology, suggesting the approach could be used to generate security features and traceability codes for high-value products including “jewellery, luxury watches, automotive and aerospace parts, medical tools and implants, or even collectible coins.”

Using ultraviolet (UV) nanosecond laser pulses, the scientists melt and evaporate material off the metal surface of the item to create “optically-smooth craters” that can create diffractive images that can be combined into aesthetic ‘watermarks’.  Optically-smooth protrusions (bumps) can also be introduced in selected places within the holographic structures in order to create hidden identifiers or signatures which cannot be detected by the naked eye.

Unlike stickers or labels, the resulting features can’t be removed – either accidentally or deliberately – and tampered with. It takes less than a minute to create a 2.4mm x 2.4mm hologram, a speed they suggest is already “very attractive” but could be accelerated with technological improvements.

While other groups have demonstrated similar results using alternative laser technologies, the researchers put their approach through its paces in multiple ways, generating holograms, holographic watermarks, and steganographic markings, which are concealed features within an ostensibly easy-to-read markings such as datamatrix or QR codes. The steganographic features were readable using a standard smartphone and a scanner app (NeoReader).

“These features enhance the applicability of the holograms as anti-counterfeiting markings for metal products,” they write.

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