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.