Abstract: A security element for authenticating bank notes, credit cards, security passes and the like is disclosed. The security element incorporates a reflective-type diffraction grating, which grating comprises a continuous layer of reflecting material on which is deposited a layer of dielectric material. Non-continuous reflecting layer portions are embedded in the dielectric material. It is practically impossible to lay bare the diffraction grating without destroying it.

Abstract: An apparatus adapted for thermally erasing or changing machine readable optical markings previously entered on a carrier of thermoplastic material which has two major sides, and wherein the optical markings cause a predetermined modification of any light rays impinging on the optical markings by either diffraction or refraction, include a erasing device adapted to be located on one major side of the carrier, for erasing or changing the markings, a reading device, operative during operation of the erasure device, and including at least two light sensors adapted to be located on the other major side of the carrier, so as to check the erasure or change of the markings effected by the erasing device. The light sensors provide output signals of respective opposite polarities following erasure or change of any one of the markings.

Abstract: A projection screen is disclosed having a surface formed by a plurality of irregularly distributed microstructural elements shaped like the outer surface of contiguous bubbles. Also disclosed is a method for making such projection screens.

Abstract: There is described a process for embossing onto a document machine-readable information in the form of optical markings with a light-modifying relief structure for indicating the genuineness of the document, comprising transferring a thermoplastic layer to the document from an embossing foil by means of a hot embossing die, and simultaneously embossing the optical markings in at least the thermoplastic layer. Also described are embossed documents produced by the disclosed process.

Abstract: An optical reading apparatus is described for reading documents which contain information in the form of optical markings which deflect a reading beam coming from a light source in at least one given direction of deflection. A first light sensor detects a deflected partial beam. A second light sensor, the optical axis of which lies in a given direction of deflection, is only receptive to those light rays deflected at the document which lie outside a first cone and inside a second cone which is coaxial with the second light sensor. A comparator compares the electrical signals of both light sensors. Altered markings, which cause additional dispersion of the reading beam, can be reliably distinguished from the unaltered markings.

Abstract: There is disclosed a method for embossing a relief pattern of high resolution into a thermoplastic information carrier by means of a heatable embossing matrix. The matrix, which exhibits the desired relief pattern, is pressed onto the thermoplastic information carrier, and is then heated by means of an electric current. After the electric current has ceased, the embossing pressure is maintained until the thermoplastic information carrier has hardened through cooling. Alternative methods permits selected variation of the relief pattern to be embossed by selectively altering the surface of the support member which supports the information carrier during the embossing operation or by selectively heating the embossing matrix.

Abstract: A method and device for identifying documents. A multiplicity of machine-readable markings which characteristically modify incident light by diffraction or refraction are applied to the documents, and selected markings are then cancelled out, the remaining markings representing coded information. The markings are of at least two different kinds causing different modification of incident light, and are arranged in a characteristic configuration on the documents. Information about said configuration is stored in an identification device to permit checking of the remaining markings.

Abstract: There is disclosed a document comprising a flat support member of non-thermoplastic material at least partly coated with a thermoplastic coating, in which coating are embossed optical markings having a light-modifying relief structure, said markings representing information indicating the genuineness or identity of the document. There is also disclosed a process for producing such a document, and an embossing die for use in such a process.

Abstract: A document is disclosed, which comprises an information carrier in which information is recorded as optical markings. The information carrier has a shape-memorizing capability actuated by supplying energy, such as heat, which changes the shape of the information carrier and the optical markings.

Abstract: There is described a method of producing a document coded with machine-readable information, said document having an information carrier with a multiplicity of storage positions, wherein selected storage positions are occupied by respective machine-readable optical markings, which markings cause a predetermined modification of incident light; the geometrical position of the markings on the information carrier represents coded information. In the method disclosed, such an optical marking is introduced into each storage position, and subsequently, selected optical markings are cancelled or altered. Also described are documents coded by means of the disclosed method, as well as a device for cancelling or altering the optical markings.

Abstract: A method and apparatus are provided for storing and reading authenticating information which is recorded on a carrier comprising at least one diffraction screen for modifying the path of a beam from an optical reading apparatus consisting of a light-source and a light-receiver. A method is provided for producing an information carrier having at least one diffraction screen.