Abstract: There is disclosed a method of forming a security image from two or more images comprising manipulating tonal values of each image element of a first image to take values within a first set of tonal values, manipulating tonal values of each image element of a second image to take values within a second set of tonal values, and forming a security image (20) from the manipulated tonal values of the first and second images, the first and second sets of tonal values being selected so that at least one of the first and second images is concealed in the security image.

Abstract: There is disclosed a method of forming a latent image. The method involves transforming a subject image into a latent image having a plurality of latent image element pairs. The latent image elements of each pair are spatially related to one another and corresponding to one or more image elements in said subject image. The transformation is performed by allocating to a first latent image element of each pair, a value of a visual characteristic representative of the one or more corresponding image elements of the subject image, and allocating to a second latent image element of the pair a value of a visual characteristic which is substantially complementary to the value of the visual characteristic allocated to the first latent image.

Abstract: There is disclosed a method of forming a reflective device which generates an optically variable image which varies according to the angle of observation. The method comprises the steps of providing a primary pattern which encodes a latent image, the primary pattern having a plurality of image elements, and providing a corresponding secondary pattern which will decode the primary pattern to allow the latent image to be observed when the primary and secondary patterns are in at least one registration, wherein the secondary pattern is provided by a micro mirror array (MMA) having a plurality of each of at least two different types of micro mirror elements, wherein the primary pattern is provided such that predetermined image elements of the primary pattern render reflection effects from predetermined micro mirror elements of the MMA optically ineffective at least at one observation angle when the reflective device is illuminated with a light source to thereby enable the latent image to be observed.

Abstract: There is disclosed a method of forming a diffractive authentication device which generates an optically variable image which varies according to the angle of observation. The method comprises the steps of, providing a primary pattern which encodes a latent image, the primary pattern having a plurality of image elements, and providing a corresponding secondary pattern which will decode the primary pattern to allow the latent image to be observed when the primary and secondary patterns are in at least one registration, wherein the secondary pattern is provided by a diffraction grating microstructure having a plurality of each of at least two different types of diffraction elements.

Abstract: There is disclosed a method of encoding a latent image. The method comprises providing a latent image to be encoded, the latent image having a plurality of latent image elements, each latent image element having a visual characteristic which takes one of a predetermined set of values, providing a secondary pattern having a plurality of secondary image elements, the secondary pattern being capable of decoding the latent image once the latent image has been encoded, relating the latent image elements to the secondary image elements, and forming a primary pattern comprising a plurality of primary image elements which correspond to the secondary image elements displaced in accordance with the value of the visual characteristic of the latent image elements to which said secondary image elements are related.

Abstract: The present invention relates to a security device or a security apparatus comprising one or more primary images (103) encoded within a secondary image in such a manner that the primary images can only be observed by an observer (102) when the secondary image, a decoding mask (105) and the observer are in a predetermined alignment. Embodiments of the invention have application in the provision of security devices which can be used to verify the legitimacy of a document, instrument or the like.

Abstract: Accordingly, in an aspect of the invention, and not necessarily the broadest aspect, there is provided a hybrid homogeneous-heterogeneous catalyst containing catalytic groups, wherein the catalytic activity of the catalyst is largely provided as a result of the interaction of catalytic groups in a suitable proximity and disposition to other catalytic groups, the proximity and disposition resulting from statistical considerations.