Zapping fakes with lasers
FROM banknotes to bottles of Bordeaux and Vans shoes to Viagra, good forgeries can be hard to detect—even for experts. The difficulty is finding a quick and reliable way to tell the difference between what is real and what is faked. Yet if you look closely enough with a microscope, the surface of almost any material shows a naturally occurring randomness: the wood fibres in a piece of paper look like a layer of noodles; smooth plastic resembles a mountain range. The details of these patterns are unique to each item and thus could be used like a fingerprint, to provide an almost foolproof means of identification.
The trouble is that employing a microscope powerful enough to record surface features at the required level of detail (a few microns) would be an expensive and cumbersome business, and not at all practical on a production line. However, if you shine a laser at the surface of an object, the way the light is reflected back can be used to gather information about the same features. And a fast, low-cost way of doing just that has now been commercialised by Ingenia Technology, a company based in London, to provide what it calls a tamper-proof method of “laser surface authentication”.
The process was developed initially at Imperial College, London, and is based on a phenomenon known as laser speckle. The speckle is a scattering of light caused by micron-sized ridges and groves on an object’s surface. By detecting the change in this speckle, it is possible to chart the texture of the surface.
Ingenia’s machines use a scanning head consisting of three small lasers and six detectors to examine part of an object. The strip that is scanned is predetermined; the top left-hand corner of a credit card, for instance. Variations in the speckle are then digitised to produce a code that is unique to the scanned item. This code is logged in a database, along with the product’s serial number or bar code. It can also be encrypted into the bar code. When what purports to be the same item is re-scanned at some later date, it should show the same pattern of speckle.