Optical component

Abstract

An optical component contains two or more hidden images for authentication and antiforgery purposes. The images are successively revealed and concealed when the optical component is held between two polarisers and one of them is rotated. The optical component comprises one or more optical retarder(s) in which the images are embedded in separate adjacent stripes or areas, each image being associated with a different mode of interaction with polarised light. Instead of two polarisers, one will suffice if the component is mounted on a reflector.

1 . An optical component, comprising one or more retarder(s) in which is/are embedded a plurality of images, the images being so arranged that, at any point in the plane of the component, an element of not more than one image is present, each image being associated with a different interaction with polarised light.  
     
     
         2 . An optical component according to  claim 1 , wherein there is a plurality of retarders in which the images are embedded, the retarders having the same or different retardation values Δnd.  
     
     
         3 . An optical component, according to  claim 1  or  2 , wherein the images are embedded in one or more retarder(s) having specific image patterns each having a different optical axis from the other specific image patterns.  
     
     
         4 . An optical component according to any preceding claim, wherein the respective images are contained in alternate areas.  
     
     
         5 . An optical component according to any preceding claim, wherein the respective images are contained in successive optionally parallel stripes.  
     
     
         6 . An optical component according to  claim 4  or  5 , wherein the areas or stripes are smaller or narrower than the eye can resolve enabling an optical component wherein one or more image(s) is/are (a) photographic image(s).  
     
     
         7 . An optical component according to  claim 4 ,  5  or  6 , wherein there are n mages, each respectively being represented on every nth stripe or nth area.  
     
     
         8 . Element for protection against forgery and/or copying, characterized by an optical component according to any one preceedingd claims.  
     
     
         9 . A viewing system, comprising a source of polarised light, an optical component according to any preceding claim, through which component the polarised light can travel, and an analyser for light which has traversed the optical component, the analyser being rotatable about the axis of the direction of travel of the light; whereby, by rotating the analyser, peaks of maximum contrasts for each image are obtained at specific rotation angles of the analyser, enabling, at each such angle, visualisation of a respective image not otherwise visible.  
     
     
         10 . A system according to  claim 8 , wherein the source of polarised light is a polarising sheet applied to the surface of the component.  
     
     
         11 . A system accorded to  claim 9  or  10 , wherein the analyser is a polarising sheet.  
     
     
         12 . A viewing system, comprising a reflector which maintains the polarisation direction of incident light, an optical element according to  claims 1  to  7  attached to said reflector, and a polariser which is rotatable about the axis of the direction of travel of the light, such that light which has traversed the polariser and the optical component is reflected at said reflector and traverses a second time the optical component and said polariser; whereby, by rotating said polariser, peaks of maximum contrasts for each image are obtained at specific rotation angles of the polariser, enabling, at each such angle, visualisation of a respective image not otherwise visible.