White light that was emitted from a white light source and converged through a condenser lens enters a light guide with a maximum incidence angle .alpha.. Since excitation light emitted from an excitation light source is adjusted by the adjustment optical system for its beam diameter, it enters the light guide with a maximum incidence angle .beta. (.beta.<.alpha.) after being converged by the condenser lens. Then, a motion mechanism displaces a second lens in an adjustment optical system in the direction of the optical axis to vary the beam diameter and the maximum incidence angle .beta. of the excitation light, whereby a divergence angle of the excitation light emitted through a light distribution lens is made to correspond to the divergence angle of the visible light.

A coin (1) with a metal surface (2, 3) has macroscopic reliefs (5) which serve for visually specifying the value of the coin and as an authenticity feature. Microscopically fine relief structures (8) with a diffraction effect are formed directly in at least one of the surfaces (2, 3). The relief structures (8) are preferably arranged in a recessed relationship and are covered with a lacquer (9). It is also advantageous if at least a part of the relief structures (8) entails an asymmetrical profile shape and/or the grating vectors in a radial orientation. The release structures (8) may also include a machine-readable coding which is recognized by inexpensive optical reading devices for installation in coin testers. The application of the microscopic relief structure (8) to a hard material surface (2, 3) can be effected by the removal of material by means of exposure of the material surface (2, 3) with a laser beam. In that operation the laser beam passes through a mask for determining the form of the relief structures (8) and then an optical image-forming system for reduction purposes. The exposure procedure can also be implemented in accordance with the dual beam interference method. In a further method the microscopic relief structures (8) are etched into the material surface (2, 3).

A method of determining at least one characteristic of one or more security documents such as banknotes, each security document including a sheet-like substrate of plastics material and opacifying layers applied to opposing faces of the substrate, the method comprising the steps of:(a) projecting radiation from a radiation source into the substrate of each security document for propagation therein, the opacifying layers acting to guide the projecting radiation within the substrate; (b) detecting a radiation emission of the substrate of each security document, the radiation emission resulting from the propagated radiation; and (c) analysing one or more characteristics of the radiation emission.

The invention relates to a validation device comprising at least one specular reflective layer, indicia on said reflective layer, a polymer protective layer overlaying said indicia, and a polymer protective layer on the side of the reflective layer opposite to said indicia wherein said indicia are formed by thermal dye transfer.

The present invention provides a method and apparatus for an optical processor. Polymerizable compounds in a specific composition containing photo-reactive materials, optically polar materials, and optical materials which can be cured with actinic radiation to form polymeric compositions, are provided. The resultant polymeric compositions are capable of forming complex optical interconnecting network structures.