A method of forming a reflective device

There is disclosed a method of forming a reflective device which generates an optically variable image which varies according to the angle of observation. The method comprises the steps of providing a primary pattern which encodes a latent image, the primary pattern having a plurality of image elements, and providing a corresponding secondary pattern which will decode the primary pattern to allow the latent image to be observed when the primary and secondary patterns are in at least one registration, wherein the secondary pattern is provided by a micro mirror array (MMA) having a plurality of each of at least two different types of micro mirror elements, wherein the primary pattern is provided such that predetermined image elements of the primary pattern render reflection effects from predetermined micro mirror elements of the MMA optically ineffective at least at one observation angle when the reflective device is illuminated with a light source to thereby enable the latent image to be observed.