『倫敦的一家公司發(fā)明了一種快速、低廉的辨別贗品的方法——“激光表面認證”法。』

　　Anti-counterfeiting measures: Zapping fakes with lasers

　　打假新招：激光打假

　　Jul 12, 2011 | From The Economist

　　FROM banknotes to bottles of Bordeaux and Vans shoes, 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.

　　According to Andrew Gilbert, one of Ingenia’s directors, the probability of two surfaces generating the same code are lower than one part in a million trillion trillion. That is far more accurate than fingerprints, for example. Nor is the system easy to fool. A piece of paper such as a banknote can be crumpled, soaked in water, scorched and scribbled on but still have its surface clearly readable. Even torn, scratched and partially missing surfaces can be read. This is because, during the original scan, the detectors pick up such a large amount of information that a re-scan need provide only part of the speckle pattern for a reliable comparison to be made. Too much damage to or tinkering with an item would, of course, raise suspicions anyway.

　　With scan times of less than a second, the system is fast enough to be used on a production line. Nor does it involve having to make changes to a product or its packaging to incorporate security features, such as adding watermarks, fitting holograms or implanting microchips. Those things are difficult, but not impossible, for forgers to replicate. Ingenia has tested the system on the packaging used for various high-value goods, like perfume, along with the security seals used on dangerous or valuable substances, and on passports, postage stamps and documents such as financial instruments. As the system provides each item with an identity, it can be used to track genuine goods and documents. Should a bank want to, it would be able to match every note it issued with the serial number printed on it. However clever a counterfeiter is, forging that is likely to prove impossible. (637 words)