Technique for verifying genuineness of authenticating device

Abstract From the Canadian patent

Abstract of the Disclosure, A given type of authenticating device operates as a diffractive subtractive color filter that exhibits a reflectivity spectrum that includes a peak occurring at a wavelength that varies as a substantially linear function of the angle of incidence of polychromatic illuminating light having a particular polarization. The verification technique involves simultaneously illuminating a sample device over a range of angles of incidence by the polychromatic light, and then employing the light reflected from the sample to illuminate a reference device which is known to be genuine over the same range of angles of incidence. A sample device is indicated as being genuine …