METHOD OF AUTHENTICATION

摘要

A method for the authentication of a solid crystalline film is described. The polymer film is crystallised under conditions such that randomly nucleated spherulites are formed which can only be observed under polarised light illumination. The unique birefringent features of the film are established by irradiating the film with polarised light of a known state and viewing the film through an analyser of known polarisation properties. One or more images of the film can be obtained by a camera or equivalent sensor by changing the polarisation of the irradiating light or the analyser orientation, or both. A material check is undertaken to ensure that the film has the expected birefringent properties and is not counterfeit. An identity check is performed by measuring the unique pattern formed by the spherulites and comparing the measured pattern with stored data.