When a coherent laser hits a surface, the laser light is diffracted in all directions. It is easy to take a laser pointer and do this experiment. The pattern that is emitted is a complex dotted pattern of bright and dark intensities. These intensities appear random but are actually a property of the material and also minor changes in shape and variations in height. The genuine part is first recorded and a reference made of the laser diffraction. To determine if the part that is present in the market is genuine, another diffraction pattern is obtained from the new part at approximately the same location and compared. If the part is found to be genuine then the patterns should match.
A company called AlpVision uses “fingerprint technology” to authenticate plastic parts that have been molded and does not require UV or coherent lasers. To quote the company “AlpVision Fingerprint leverages the intrinsic microscopic surface irregularities found in a mold and uses these unique characteristics as the means of authentication”. Their technology can use an iPhone camera with their application to authenticate.
Pattern searching becomes important in today’s manufacturing wherein it does not take much to duplicate a mold and make a competing part. However, with 3D printers being common, it will be interesting to see how part manufacturers can compete when it costs just pennies to make a new part if a 3D model exists.