According to a first aspect of the invention, there is provided a method of deriving information from an optically readable security element, comprising: optically reading the optically readable security element, the optically readable security element comprising at least one optically readable structure, optically readable in response to excitation of the optically readable structure; the reading comprising determining data indicative of an optical property of the optically readable security element using first emission electromagnetic radiation, emitted in response to excitation of the optically readable structure; the deriving information further comprising using the determined data indicative of an optical property, in combination with a temporal excitation-emission relationship related to the optically readable structure, to derive the information.