METHODS OF MAKING HOLOGRAPHIC DEVICES

摘要

A method of making a holographic device (4) comprises the steps of: forming a heterogeneous support medium (2) having at least two regions (1 ) which are heterogeneous; placing the heterogeneous support medium under recording conditions, e.g. in a liquid X, which are selected to change one or more physical properties of the heterogeneous support medium, wherein the extent or nature of the change in the physical property or physical properties is different in at least two of the heterogeneous regions; recording a holographic image in the heterogeneous support medium while it is under recording conditions; and removing the heterogeneous support medium from recording conditions. Such a device can be used for security and authentication.