An identification card provided with secret data contained in the form of a wave guide
hologram recorded in a layer on the card. Light for developing or displaying the hologram is
introduced into a wave guide layer extending along the surface of the card through a grating
that admits light only of a given wave length suitable for developing the wave guide
hologram. The secrecy of the wave guide hologram is further enhanced by incorporating into
the light coupling grating a further hologram by which light only of a predetermined pattern …