Abstract: A method for forming a visual feature on the surface of an article, such as a document or other substrate, which includes the steps of forming data defining the visual feature, and using this data to control a transfer apparatus to transfer discrete elements from at least one foil onto the surface of the article, to form the visual feature. The discrete elements are applied in different densities, for example, numbers per unit area, according to differences in light intensity required to define the visual feature. The discrete elements are, preferably, optically variably reflective and, preferably, also transmissive. The transfer apparatus can be a thermal printer.

Abstract: A substrate, such as a document of value, carries a design feature (F), which includes an array of repeating patterns with the patterns exhibiting discrete differences in one or more visual characteristics, for example, shape, color or optical responses, according to a predetermined pattern. The differences are, preferably, indiscernible to the unaided eye, but can be discriminated by an optical reading machine. In an alternatively preferred embodiment, the visual characteristics of each pattern represent 8- or 16-bit information.

Abstract: A substrate is arranged for presenting a three-dimensional optical image to a viewer. The substrate is formed with a multiplicity of pairs of spaced optical elements, with each pair of spaced optical elements being arranged for directing light incident thereon to a respective eye of the viewer, when the viewer is positioned at a predetermined angle of view or within a limited range of angles of view, for giving the viewer a perception of a point image located at a predetermined distance from a plane of the substrate at an intersection of lines followed by light rays from a respective optical element of a pair of spaced optical elements. The multiplicity of pairs of optical elements are arranged at different x and y orientations on the substrate, so that corresponding multiplicity of adjacent point images, so provided, together form the three-dimensional optical image for the viewer.

Abstract: A substrate is arranged to provide at least one optically variable image the substrate has a front surface formed with a plurality of groups of elemental areas, the different said groups of elemental areas corresponding to respective pixels of the image. The different elemental areas of each group are formed with respective sets of grooves or ridges, where the grooves and ridges of different elemental areas of each group are disposed at different orientations in the different elemental areas, such that each elemental area directs light to a viewer from a respective angle of view. For any given angle of view, the image seen by the viewer is made up of light reflected or refracted without interference.