SECURITY DEVICE

摘要

A security device comprises a holographic optically variable effect generating structure (1) having at least two discrete sections (2). The sections (2) generate in response to white light illumination (51) an optically variable image (3-5) consisting of at least two defined graphical elements located at or near an image plane either on or adjacent to the plane of the device. In response to coherent illumination (6), the sections generate at least two discrete covert images (7-9), in the form of indicia, whose image planes are located at a distance away from the real plane of the device. The covert images (7-9) are reconstructed at different angles to a normal to a substrate (1) supporting the device such that the covert images are spatially separated on their image plane, the covert images being non-visible under white light illumination.