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19 Aug 2005
Laser written images could help prevent forgery of bank cards and security passes.
A technique for producing UV laser-written digital images that change their appearance with viewing angle has been developed by Sherwood Technology, UK. The Widnes-based color chemistry expert says that its hologram-style images named DigiVU OVD could help protect important documents and branded products from counterfeiting.
According to Sherwood, its process can write black and white digital images with a resolution of up to 2500dpi on to a metallic substrate or foil coated with the firm’s proprietary ink. An interaction between the UV (266 or 355 nm) writing beam and the ink creates an image which reflects light differently depending on the angle of the incident light -- shifting between a positive and negative image.
Andrew Jackson, Sherwood’s Applications Marketing Manager, says that it takes just a few seconds to write the image depending on its size and resolution. Unlike holograms which need to be prepared in advance, the design of the laser written images could be easily changed. Potential applications include the use of images of individuals on a security pass, identity card or bank card.
According to Jackson, the process was inspired by customer requests for images that were clearly visible and easily identifiable with the naked eye without the need for any kind of reading machine. Sherwood will market the process alongside its DigiVU micro -- a range of tiny unobtrusive security marks and 2D codes that can be applied to products.
Sherwood is also working hard on developing a single coating that allows full-color laser marking and is confident that it will have a solution within the next 12 months. “By varying the energy of the beam you get different colors from a single coating. We’ve achieved red, blue and yellow so far but green is proving more difficult to produce.”
Author
Oliver Graydon is editor of Optics.org and Opto & Laser Europe magazine.
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